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XRODAdvanced Design and Simulation

of Rod Pumping Systems for Deviated and Ver tical Wells

3075 E. Imperial Hwy Suite 125Brea, CA 92821Telephone #: (562) 694-3297Fax #: (562) 694-8641gotheta.com

E-mail Addresses:Product Manager: Kevin Lo, [email protected] Support: [email protected]: Christy Kukula, [email protected]

http://www.gotheta.com

mailto:christy%40gotheta.com?subject=

© Theta Oilfield Services, Inc., 2014.All Rights Reserved. This manual may not be reproduced in whole or in part without the written per-mission of Theta Oilfield Services, Inc.

XROD, XROD-V, RODSTAR, RODSTAR-D, RODSTAR-V, RODDIAG, XDIAG, XDIAG-V, XDIAG-D, XBAL, XTOOLS, XANIMATE are trademarks of Theta Oilfield Services, Inc.

Printed in the United States of AmericaFourth Edition, April 2014

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ContentsTechnical Support . . . . . . . . . . . . . . . v

System Requirements . . . . . . . . . . . . . v

1 introduction 1

1.1 Program Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Advanced Capabilities and Program Limitations. . . . . . . . . . . . . . . 3

1.3 Help System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 XROD CD and Software Sentinel . . . . . . . . . . . . . . . . . . . . . . 3

2 Software installation 5

2.1 XROD Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Questions About Installation . . . . . . . . . . . . . . . . . . . . . . . 5

2.3 Installing the Software Sentinel . . . . . . . . . . . . . . . . . . . . . . 5

3 Starting and Setting Up XROD 7

3.1 Starting XROD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.2 Exiting XROD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.3 Setting up XROD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.3.1 General setup options . . . . . . . . . . . . . . . . . . . . . . . 12

3.3.2 Defaults and Limits . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.3.3 Output Options. . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.3.4 Pumping Unit Options . . . . . . . . . . . . . . . . . . . . . . . 15

3.3.5 Rod Grade Options . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.3.6 Cost Database . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.3.7 Batch Mode Options . . . . . . . . . . . . . . . . . . . . . . . . 20

3.3.8 AI Mode Preferences . . . . . . . . . . . . . . . . . . . . . . . . 22

4 Running XROD 25

4.1 XROD’s User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.1.1 XROD’s Help System . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2 Entering Rod Pumping System Data into XROD, AI mode . . . . . . . . . . . 27

4.3 Entering Rod Pumping System Data into XROD, non-AI mode. . . . . . . . . 29

4.3.1 Entering Well Information Data . . . . . . . . . . . . . . . . . . . 30

4.3.2 Entering Production Information. . . . . . . . . . . . . . . . . . . 32

4.3.3 Entering Pump and Tubing Information Data . . . . . . . . . . . . . 33

4.3.4 Entering Rod String Data . . . . . . . . . . . . . . . . . . . . . . 36

iv | Table of Contents

4.3.5 Entering Pumping Unit Data . . . . . . . . . . . . . . . . . . . . . 40

4.3.6 Entering Motor Information and Energy Cost . . . . . . . . . . . . . 48

5 Changing, Loading and Saving Data 51

5.1 Visual Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.2 Storing Data Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.3 Running and Viewing the Output . . . . . . . . . . . . . . . . . . . . . 52

5.3.1 Saving the output . . . . . . . . . . . . . . . . . . . . . . . . . 54

5.3.2 Running in Batch Mode . . . . . . . . . . . . . . . . . . . . . . . 55

5.4 Loading Data from Disk . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.4.1 Viewing Previously Saved Output . . . . . . . . . . . . . . . . . . 59

5.5 Manipulating Input Windows . . . . . . . . . . . . . . . . . . . . . . . 59

6 Rod Pump System Design 61

6.1 Understanding XROD’s Output . . . . . . . . . . . . . . . . . . . . . . 62

6.1.1 Dynamometer and Permissible Load Plots . . . . . . . . . . . . . . 62

6.1.2 Torque Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.1.3 IPR Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.1.4 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.2 Rod Pump System Design Guidelines . . . . . . . . . . . . . . . . . . . 70

6.2.1 Shallow, High Rate Well Simulation . . . . . . . . . . . . . . . . . 71

6.2.2 Selecting the Target Production . . . . . . . . . . . . . . . . . . . 71

6.2.3 Avoiding Rod Compression . . . . . . . . . . . . . . . . . . . . . 71

6.2.4 Minimizing Power Consumption . . . . . . . . . . . . . . . . . . . 72

6.2.5 Reducing Gearbox Torque . . . . . . . . . . . . . . . . . . . . . . 72

6.2.6 Using XROD for Correct Equipment Sizing . . . . . . . . . . . . . . . 72

6.2.7 Using XROD for Diagnostic Analysis . . . . . . . . . . . . . . . . . . 73

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Technical SupportTechnical Support for XROD is provided by phone and e-mail to customers with a current An-nual Technical Support Agreement.The first year of technical support is provided free with the initial purchase of a license.Support for customers with an expired agreement is billed at $100/hour with a one-hour minimum per incident.Please include the Serial Number from your Senti-nel when contacting support.

Phone Support:Monday-Friday 8:00 AM - 4:00 PM PST.(562) 694-3297

E-Mail Support:[email protected]

System RequirementsProcessor: 1.6 GHz or higher

Operating System: Windows XP/Vista/7/8Memory: 1 GB of RAM or higher

Hard Disk Space: 150 MB available disk space

Display: 1024 x 768 or higher

mailto:[email protected]

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1 Introduction

XROD™ is a powerful, easy-to-use rod pumping system simulator and Artificial Intelligence (AI) design tool. With XROD you can design new rod pumping installations faster than ever before, or make changes to existing rod pumping systems by running the program in non-AI mode. It is a tool that you can use to compare pumping units, pumping speeds, plunger sizes, rods, motor types, etc. You can evaluate the effect of pump fillage, fluid level, or an out-of-balance unit. Also, you can study the effect of prime mover speed variation, stuffing box friction, etc. XROD also allows you to combine sophisticated rod pumping system model-ing with inflow performance data for even more powerful capabilities. The artificial intelligence (AI) technology in XROD allows you to get great system designs in seconds with minimum input data.In the non-AI Mode, XROD behaves the same as RODSTAR (but with some additional capabili-ties). XROD is very easy to use, flexible, customizable, and fast. With a single click of the mouse, you can access any input screen at any time. You can change an input by simply clicking on it, and when you have a question, simply press ! for context sensitive help for any input item. You can also take advantage of standard Windows features such as being able to copy the dynamometer, torque plots, or IPR plots to the clipboard and then paste them in any other Windows document.By taking advantage of the program’s powerful AI mode, you can save a lot of time and come up with better answers as compared to RODSTAR in vertical mode. This makes it possible to optimize rod string designs, find out the pumping speed and plunger size you need for a target production,

etc. in seconds instead of hours. XROD in the AI mode makes it possible to get these answers even with little rod pumping expertise.The advantage of XROD’s AI mode over ROD-STAR in vertical mode is the built in expertise which substantially minimizes the user input required. After setting up the program one time with some basic preferences for rods and pumping unit types to consider, you can simply enter a depth and production goal. XROD will utilize your preferences and find the best system design for the well including the pumpjack size, stroke length, plunger diameter, rod string design, pumping speed, motor size, etc., all done using a batch pro-cess which also generates a summary spreadsheet with all the best designs listed for each pumping unit type.

1.1 Program FeaturesXROD remembers the information you type when you start a case from scratch. You can exit XROD while in the middle of entering data for a new case, and XROD will save the data you have entered. This works the same way if your system crashes. The next time you start XROD, the program will ask you if you want to resume entering data. If so, you will be returned to the data entry window you were using when you left XROD, with all the data you had entered already in place. XROD contains data for all common pumps, rod sizes, rod grades, pumping units, tubing sizes, etc. Also, it “knows” when you need slim hole couplings or a thin wall pump, what rods fit in the tubing size you selected, the maximum recommended pumping speed for any system design, etc. When running XROD in AI mode, the program will design all of these parameters for you.

2 | Introduction

XROD can read well files created with ROD-DIAG™, XDIAG™ (Theta Oilfield Services, Inc.’s diagnostic computer programs) and CBAL-ANCE™ or XBAL™ (Theta Oilfield Services, Inc.’s pumping unit balancing programs). XROD can read all the data contained in a RODDIAG or XDIAG file, including the measured dyna-mometer card. This allows you to redesign pump-ing systems without having to reenter system data. XROD can display and print the measured dynamometer card overlaid on the same plot as the predicted surface dynamometer card (in the non-AI mode). This feature has many uses that include finding the correct rod-tubing friction, or determining whether the load cell used to record the dynamometer card may be out of calibration. XROD will not read XROD files unless it is in the AI Mode. The program switches from RODSTAR (non-AI mode) to XROD using the “AI” button on the toolbar and XROD files are not compatible with RODSTAR. If you attempt to open ROD-STAR files while in AI mode XROD will prompt you to switch to non-AI mode in order to work with these files, and vice versa.By being able to read CBALANCE/XBAL files, XROD can get the existing maximum counter-balance moment based on the existing position of the counterweights. This eliminates the need for a field measurement of counterbalance effect. Also, you can enter the calculated balanced maximum counterbalance moment back into CBALANCE/XBAL to find out how to balance the pumping unit in one step.XROD can simulate any pumping system and can accurately predict its performance. For a system you specify or ask the program to design for you in the AI mode, the program predicts the sur-face and downhole dynamometer cards. Also, it calculates the peak gearbox torque and gearbox loading, structure loading, rod loading, pump stroke, minimum required pump length, plunger length, pump spacing, expected production rate, the counterbalance needed to balance the unit, the prime mover size, overall system efficiency, daily energy consumption, monthly electricity bill, and

other useful information. Also, XROD, in non-AI mode, allows you to enter inflow performance data so that you can easily design a pumping system for any pump intake pump intake pressure, calculate the expected production rate, pump intake pressure and pump condition for any rod pumping system, find out the maximum production rate you can get, and more.Also, in contrast to the conventional trial and error system design, with XROD you can simply enter the pump depth and a target production and the program simultaneously recommends the best system designs for each pumping unit type you selected in Setup. It calculates strokes per minute, plunger size, rod string design, motor size, etc. It recommends the best pumping unit size you need for each manufacturer based on the target produc-tion you entered. Or, you can enter IPR data and have XROD calculate the target production and design the system for that target production.XROD comes with a large pumping unit database so that you can easily select and compare pumping units without having to get the unit dimensions yourself. XROD can model any pumping unit geometry including long stroke units such as the Rotaflex. Also, you can enter your own pumping unit data in case your unit is not in the program’s database. Advanced error trapping and warning messages help prevent errors and make you aware of special requirements necessary for proper system operation.It is important to remember that XROD was cre-ated with the idea of reducing the required input to the bare minimum of pump depth and target production when in the AI mode. The program will design the whole system for you from this information and for each pumping unit type you selected in the AI Mode Preferences in Setup. In order to input any other data you must click the AI button to exit AI mode. When you do this, XROD will behave like RODSTAR and it will require the same input data as RODSTAR.

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1.2 Advanced Capabilities and Program LimitationsXROD has many advanced features that enable you to accurately predict system performance for any rod pumping system. It can simulate wells of any depth including very deep or shallow wells. XROD, like RODSTAR can model fluid inertia effects that are present in wells that pump incom-pressible fluids with larger than 2.00” plungers from depths of less than 4000 feet.By calculating the minimum stress at the bottom of each rod section, XROD shows whether the rods are in compression or not. This is vital for fiberglass rods which must never be in compression to avoid premature failures. This is also important for steel rods since excessive compression can cause buckling failures.XROD can model the effect of prime mover speed variation and pumping unit inertia and can ac-curately calculate electricity consumption and the monthly energy bill. Because XROD uses actual motor efficiency curves, the results are very ac-curate. You can use this capability to compare the energy consumption of systems with different rod designs, plunger sizes, or pumping unit types. XROD’s Inflow Performance Relationship (IPR) capabilities allow you to select the IPR relationship you want XROD to use (Vogel or Fetkovich), you can enter one to ten test points, and can integrate IPR and rod pumping system models to predict the maximum production rate possible, the fluid level and pump condition for a given pumping speed, or the target production for any fluid level or pump intake pressure you want.Because of all these features, XROD has virtually no limitations and is the most advanced and easiest to use program of its kind.

1.3 Help SystemXROD takes full advantage of Microsoft Win-dows to bring you state-of-the-art context-sensitive

help for any input field by simply pressing the ! key. Also, you can search help for any other item.

1.4 XROD CD and Software SentinelThe XROD program installation CD contains many compressed files that the installation pro-gram copies to the hard disk of your computer. Some of these are useful to know about. These are located in the same folder where you elected to install XROD. The default is “C:\Program Files\Theta\RODSTAR” or “C:\Program Files\Theta\XROD”.

File Name: Explanation:XRODV.EXE The program file for

XROD. It is the file that your Desktop Icon runs when you double-click it.

RODSTAR.CDB Contains the costs for both rods and pumping units. Once you create this file by entering rod and pumping unit cost data, you can provide copies to other users in your company.

CUSTOM32.PUD This file contains the measured pumping unit information you entered in Setup. Once you create this file, you can distribute copies to other users in your company.

4 | Introduction

Files ending in .PUD The program’s pumping unit database. When updates are announced on our Website for new pumping units that have been added, you can download a zipped file that contains addi-tional PUD files to add to your folder.

Files beginning with demo_

Several files are in-cluded that are example cases to demonstrate the program functions.During installation, there are copies of these files placed in the folder used when opening case files.

Files ending in .RST Case files saved by RODSTAR release prior to 3.0.

Files ending in .RSVX Case files saved by RODSTAR in vertical mode.

Files ending in .XRVX Case files saved by XROD in AI mode.

Files ending in .RDG Case files saved by RODDIAG.

Files ending in .XDG Case files saved by XDIAG.

Files ending in .CBL Case files saved by CBALANCE

SENTINEL.INI For installations using a Network license, this file is located in the program folder on the client PC and has the name or IP address of the license server being used.

The XROD program is protected and cannot run without a software sentinel supplied by Theta Oilfield Services, Inc.. See Chapter 2 for details on how to install the software sentinel.

XROD | 5

2 Software Installation

Before you install the program, make sure you have the hardware and software you need to run XROD

2.1 XROD InstallationXROD is installed from the Theta Software Suite installation CD that you received or from the installation file you download from our web site. Load the CD onto your PC and the installation program should load automatically. Or, if you downloaded a stand-alone installation file, double click on its name. After the “Welcome” screen you will have three options for whether you are using a Network or Standalone license and whether you have a USB Sentinel or a Parallel Port Sentinel. After selecting the proper choice, the next screen will prompt you for the programs to install. That screen also has a button that lets you display and print the detailed Installation Guide for your spe-cific installation. After installing the program, put your original CD away in a safe place. If the Software Installation Suite CD becomes damaged or lost, please call Theta Oilfield Services, Inc. at (562)694-3297 for a replacement.

2.2 Questions About InstallationThe following are some answers to questions you may have about installing XROD.Do I need to delete earlier versions of XROD before I install?No. When updating versions of XROD, the pro-gram defaults to install to the “C:\Program Files\

Theta\XROD” directory. If your previous copy of XROD is in another directory, you can specify to install over it. It will not replace any of your case files, just the old version of the program.The installation defaults to setting “C:\THETA” as the common folder for your case files. Using a common folder is a good idea since several of the Theta Enterprise applications that you might have can all share the same case files.Although a new version of XROD can read files created with older versions, an older version of XROD cannot read files created with a new ver-sion of the software.What happens to files I have created with older versions of XROD?Nothing. When you install or reinstall XROD, only program files are replaced. The latest version of XROD saves files in the XML file format but can read files created with older versions of XROD as well.What happens to the Setup Settings from previ-ous versions? If the previous version is not very old (before the new setup options were developed) then your set-tings will be preserved.

2.3 Installing the Software SentinelYour XROD license is validated and protected by a security bitlock called a Sentinel. For Stand-alone installations, this is either a USB key or a Parallel Port key that is attached to your PC. For Network Licenses, the key is attached only to the

6 | Software Installation

Network License Server. See the Detailed Instal-lation Guide that is available for printing from the Software Installation Suite CD.Theta Oilfield Services, Inc. uses SafeNet sentinels for software protection. USB type sentinels can be plugged into any available USB port or hub on the PC. Only one sentinel is needed to support mul-tiple products on a standalone PC or on a network server.XROD communicates with the sentinel and al-though the program can be copied, it will not op-erate without a sentinel supplied by Theta Oilfield Services, Inc.. If the sentinel is not installed correctly, the pro-gram will warn you that the sentinel does not ap-pear to be connected. If this occurs, make sure the sentinel in properly installed and the connection is not loose. If the sentinel is properly installed but is not working, it may have been damaged. Frequent plugging and unplugging, and static electricity can damage the sentinel. If this occurs, contact Theta Oilfield Services Inc. to determine if you need a replacement. Do not discard the damaged sentinel. Even if it is damaged, you must return it to Theta Oilfield Services, Inc. before a replacement can be sent out. When XROD first starts, it reads and displays the serial number of your sentinel on the opening screen.

XROD | 7

3 Starting and Setting Up XROD

3.1 Starting XRODThe XROD installation program will put an Icon on your Desktop and an entry in your Start Pro-grams for access to XROD. To start the program, simply double-click on its icon.You can also start XROD from the File Manager by double clicking on XRODV.EXE. Also, the Windows File Manager allows you to associate files with applications. When you associate a file with an application, you open the file and start the application at the same time. For example, to associate RODSTAR files (with an “.RSVX” file name extension) with XRODV.EXE, do the following:1. From the File manager, go to a directory that

contains XROD files and double-click on one of these files.

2. If the file is not already associated with XROD windows will let you know and ask you to select the program from a list. Make sure this option is selected and click on the OK button.

3. Click on Browse, go to the directory where XRODV.EXE resides (typically, it will be in C:\Program Files\Theta Enterprises\XROD, and double click on it.

4. Choose the OK button.After you do the above steps then to load and run a RODSTAR file from the File Manager, simply double click on it.XROD has a “getting-started” window, shown in Figure 3.1, that appears whenever you start the program. The window shows the most common toolbar icons you need to know to begin using XROD.

3.2 Exiting XRODTo exit XROD, double click on its Control-menu box (upper left hand corner) or select File and then Exit. Another way to exit XROD is to press A+ $. Before exiting XROD make sure you have stored your data to disk (XROD asks you if you

Figure 3.1 - The “Getting Started” Window

8 | Starting and Setting Up XROD

want to save the data when you exit, if you have changed your data since the last time you saved it). Otherwise it will be lost.

The XROD Window Figure 3.2 shows the XROD window that appears when you start the program. XROD behaves like any other standard Windows program. You can use the mouse to move and size windows, move and restore icons, select text, choose commands from menus, and dialog boxes, and complete almost any other task in XROD aside from typing text.Following is an explanation of the parts of the XROD window as shown in Figure 3.2.The control-menu box is in the upper-left corner of each window. The control menu is most useful if you use the keyboard. You can use the control

menu commands to resize, move, maximize, mini-mize, and close windows. Also, you can use it to switch to other applications. (If you use a mouse, you can perform these tasks by clicking and drag-ging.) Double-clicking on the control menu box closes XROD.The title bar shows the name of the application and the name of the file currently in memory. If more than one window is open, the title bar for each active window (the one that you are working with) is a different color or intensity than the other title bars.The menu bar lists the available menus. A menu contains a list of commands, or actions, you can carry out with XROD. For example, click on the Help menu to see a list of helpful choices.The Minimize button reduces XROD to an icon. After you minimize XROD, you can reopen it by

Figure 3.2 - XROD’s main window

XROD | 9

double clicking on the XROD icon at the bottom of your screen.The Maximize button causes the XROD window to fill the entire screen. After you maximize the XROD window, the maximize button shows a double box and is called the restore button. Click-ing on the restore button re-sizes the XROD win-dow to the size it was before you maximized it.Using the mouse you can resize XROD’s main windows. When you resize XROD’s window to a size smaller than required to display all informa-tion, it will display vertical or horizontal scroll bars as necessary. You can use these scroll bars with the mouse to view unseen portions of entry windows that do not fit in the allotted space.The Close button causes XROD to exit. It’s easier to click the Close button once than to select Exit from the File menu.The Status bar shows useful messages during data entry, when you load a case from disk or when you point to a toolbar icon. The status bar is located at the bottom of the main window.The toolbar gives you quick access to menu com-mands using your mouse. When you first load XROD, only some of the buttons on the toolbar are active. When you enter data or read a file from disk, then the print button and all the buttons that correspond to input windows become active. If you load a file that contains output then the report icon also activates. Otherwise, if the file contains only input then the report icon remains inactive until you run the case. For a quick reminder of what each toolbar button does, simply place the mouse pointer on it. A small message box called a “tool tip” appears that tells you what the toolbar icon does (see Figure 3.3). Also, the status bar shows more information about the same tool bar item.Following is a more detailed explanation of each button on the toolbar from left to right:

New file - This is the first button on the toolbar and shows a picture of a blank page. Click on this button to start entering data for a new case.Open file - This is the second button on the toolbar and shows the standard open file icon used by most Windows programs. Click on this button to read a RODSTAR, XROD, RODDIAG, or XDIAG file that was previously stored on disk.Save file - This is the third item on the toolbar and shows a picture of a diskette. Click here to save the data in memory to disk. If this is the first time you are saving this case, XROD asks for a new file name. After you save a file, or after you load a file from disk and make changes to it, click on this button to quick-save the data under the same file name. To save it under a different file name click on File on the menu bar and then select Save As....Setup - This is the fourth item on the toolbar. Click here to see XROD’s Setup window. This allows you to specify inputs and preferences that normally do not change often such as: your com-pany name, electricity cost, units of measure, standard sucker rod length, custom sucker grades, measured pumping unit data, pumping unit and sucker rod cost, batch run options, printed report options, and custom summary spreadsheet formats.Well information - This is the fifth item on the toolbar and shows a picture of a file cabinet. Click here to open the well information window. When

Figure 3.4 - XROD’s toolbar when in non-AI mode

Figure 3.3 - Tool Tip Example


you first load XROD this icon (and the next five icons) is inactive until you enter well information data or until you load a file from disk. The file information window contains data such as pump depth, run time, pump condition, tubing and cas-ing pressures, fluid gravity, etc.Production information - This is the sixth item on the toolbar and shows a picture of a barrel. Click here to open the production information window that has data for items such as fluid level, pump intake pressure, target production, IPR data, etc.Pump and tubing information - This is the seventh item on the toolbar and shows a picture of a down-hole pump . Click here to see data for tubing size, pump type and size, tubing anchor depth, rod-tub-ing friction, and fluid inertia effects.Rod string information - This is item eight on the toolbar and shows a picture of a sucker rod. Click here to open the rod string information window. This is where you specify what kind of rod string you want XROD to design for you. Also, you can enter your own rod string design, specify the ser-vice factor you want to use, etc.Pumping unit information - Click here to open the pumping unit information window that has data for pumping unit type, crank rotation, stroke length, structural unbalance and counterbalance data.Motor information - This icon shows a picture of a motor. Click here to open the motor information window that has data for electricity cost, power meter type, motor type and size, moments of iner-tia and whether to include motor speed variation.Previous window - This icon shows an arrow pointing to the left. Click it to go back to the pre-vious input window.Next window - This shows an arrow pointing to the right. Click here to advance to the next win-dow when entering data for the first time or when you are changing data.AI Mode - Click on this icon to change between AI and non-AI (RODSTAR) modes.

Run - This item follows the arrow icon on the toolbar and shows a picture of surface and down-hole dynamometer plots. Click here to run XROD after entering all your data or after you change an input.Report - This item follows the run icon on the toolbar and shows a picture of a printed page. Click here to view the output in memory. This allows you to view the output saved in a file you just loaded from disk, or to return to the output screen. If this button is inactive (dimmed) it means that there is no output report in memory. To make it active, run the case, or load a case with saved output.E-mail Icon - Click on this icon to e-mail one or more cases to Theta Oilfield Services, in case you have questions.Print - This button follows the Report button on the toolbar and shows a picture of a printer. Click it to send the output to the printer.If you have entered data for a case, but haven’t run the calculations yet, you can get a printout of your input data by itself. You get the same one-page output, except that only the input data appears on the page.The Print… command on the File menu allows you to select exactly which parts of the output you want printed. For more information, see section 3.3.4, Output Options under Setup.Export CBM - This item is second from last on the toolbar and shows a picture of a crank and coun-terweight. This button becomes active after XROD runs or after you load a file with saved output. Click it to place the maximum counterbalance mo-ment for balanced conditions on the clipboard for use in CBALANCE or XBAL.Automatic Batch - This enables the batch mode set-ting. If not set up it will redirect you to the setup option for this feature.Help - This is the last item on the toolbar and shows a picture of a question mark. Click this but-ton at any time to get help.

XROD | 11

Visual Input - This al-lows you to select what system variable you want to change using a visual depiction of a rod pumping system. Right click to select a specific item to change and then

left-click on the specific item.Alphabetical List - This shows an alphabeti-cal list of all the input parameters. Selecting any of these parameters and clicking ok will bring up the window in which you can modify this input.

3.3 Setting up XRODClick on the Setup button on the toolbar to open XROD’s Setup window. Another way to access Setup is to open the Tools menu and then select XROD Setup. This window which is shown in Figure 3.5 allows you to enter items that do not normally change from run to run. Also, Setup allows you to customize XROD by entering your company name, default electricity cost, custom rod grades, measured pumping units, rod and pumping unit cost data, and a lot more.

The measured pumping unit data you enter is saved in the CUSTOM32.PUD file in the program directory; the cost data you enter for rods and pumping units is saved the RODSTAR.CDB file in the program directory. XROD stores all other information you enter in Setup in the registry.

Figure 3.6 - Help for XROD’s setup

Figure 3.5 - XROD’s Setup window


It is recommended to save a file with your personal settings because you have the option to convert your settings to the settings saved on a file. If you wish to duplicate a run, one of your colleagues created, you can use the settings from the file. To restore your settings you can load your saved file and follow the prompts to load the settings from your saved file.You can access the help menu for helpful tips when setting up XROD. This menu contains three tabs to navigate the help topics and a fourth tab for help with terms (Glossary). For context sensitive help simply press the F1 key while in the field in question. The help menu will automatically open up to the help topic pertaining to that field. You can manually search the topic using the Contents tab or use the search tab to input a specific term and search for help topics related to that term. Figure 3.6 shows the help feature for the XROD Setup window.

3.3.1 General setup options

Measurement UnitsFor measurement units you can select English, Cana-dian, or Metric/SI. Eng-

Figure 3.7 - Setting up default quantities for XROD

Figure 3.8 - Selecting output options

XROD | 13

lish units are mainly used in the USA and South America. If you select this option XROD will ask for pump depth in feet, production rate in BFPD, plunger and rod diameters in inches, etc. The “Canadian” option provides you with the common mix of English and Metric units used in Canada. The “Metric/SI” option will cause XROD to use Metric/SI units for most inputs. Regardless of the units you select, you can press @ while entering numeric data to convert from one system of units to the other. When you press @ to convert units, the background of the input field box changes color from light blue to light green.

3.3.2 Defaults and LimitsThe “Defaults” input window in Setup for XROD is shown in Figure 3.7. Here, XROD allows you customize the default information used by the program when you begin entering data for a new case. You can also change the rod stress loading limits used by XROD in a steel or fiberglass rod design, so that XROD will use larger rods rather than exceed the loading lim-its you specify. Any of the following items can be custom-ized: • Casing pressure• Company name• Electricity cost• IPR correlation• Motor type• Oil gravity• Plunger size• Pump condition

• Pump efficiency• Pump fillage• Pump load adjustment• Run time• Standard steel sucker rod length• Steel rod service factor• Stuffing box friction• Tubing pressure• User name• Water cut• Water specific gravityThe program uses the standard steel sucker rod length (typically 25 or 30 ft.) to calculate steel rod string section lengths that are evenly divisible by it. This works whenever XROD designs the rods

Figure 3.9 - Cover Page Editor Window


in the setup window. Second Company fields hold this information. This page may also be edited using the comments button on the well informa-tion window. When clicking this button you will find the input window for the cover page, refer to Figure 3.9. This page is regenerated when viewing the report so that you can run a case and edit the cover page to comment on the results of the run. The cover page window contains input fields for your company information labeled “My Company”. The recipient of the document is labeled “Customer Company”. Special buttons have been created to automatically insert comments from other parts of the program which include “Add Well Informa-tion Comment”, “Add Rod String Information”, and “Add Setup/Defaults Cover Page Comment”. An example of a completed cover page is shown in Figure 3.10.

♦ Input data and calculated results.This option prints one page showing all the input data and the results of the calculations, as well as miniature predicted dynamometer and torque

string (when XROD calculates a steel rod string taper design, whether for a steel rod string, or a tapered steel rod section beneath a fiberglass.) For Corod rod strings, XROD ignores this number. For fiberglass rods, the program uses the standard length of 37.5 feet.

3.3.3 Output OptionsXROD gives you full control over what is shown on the printed output. Using the Output Options tab in Setup, shown in Figure 3.8, you can select the items you want included on the output. The options you select here are the items printed by de-fault when you select Print… from the File menu, or use the Print toolbar button. You can choose from among the following:

♦ Cover PageThis option prints a page showing all the company data of the user and recipient of the results output. To insert this information, select the defaults tab

Figure 3.10 - Cover Page

XROD | 15

plots. ♦ Cost analysis.

This option prints both the rod string and the pumping unit costs. You must already have entered the costs into XROD’s cost database (see section 3.3.6, “Cost Database,” on page 23 for more infor-mation).

♦ Inflow performance (IPR) chart.Selecting this option gives you an additional page with the IPR plots, the IPR data including the test points, and a table of pressure versus production.

♦ Dynamometer cards and Torque PlotsSelecting this option prints a separate single page containing the predicted surface and downhole dynamometer cards with the predicted permissible load diagram. It also prints the net gearbox torque plots for existing and balanced conditions on the bottom half of the page. The dynamometer card plot may also show the actual (measured) surface dynamometer card (if you loaded a RODDIAG or XDIAG case into XROD).

♦ Overlay actual (measured) dynamometer card.If you load a RODDIAG or XDIAG case into XROD in the non-AI mode, the program can plot the surface dynamom-eter card that was stored in the RODDIAG or XDIAG file on the same plot as the predicted dynamometer card.

3.3.4 Pumping Unit Options

Under this item, there are two sub-items, Customize Pumping Unit List, and Measured Pumping Unit List. Let

us take a look at each of these items: ♦ Customize Pumping Unit List

This option allows you to customize the list of units displayed by the program at the pumping unit selection window (non-AI mode) when you select the option “Use custom pumping unit list”. Here you can select the pumping unit manufac-turer and the pumping unit sizes you have for each manufacturer in the field. After you customize the pumping unit list, you can select pumping units faster since the program will only show the units you have in the field instead of displaying all the pumping units in the pumping unit database. As mentioned above, you need to select the option “Use custom pumping unit list” in the pumping unit input window to see the custom list.Also, when running XROD in AI mode, you can select the option to use the customized pumping unit list only by selecting this option in the AI Mode Preferences window in Setup. This saves you time by minimizing the time and effort required to select a pumping unit. For example, if you only have 12 different sizes of Lufkin Conventional, 10 sizes of Mark II, and 14 American Conventional unit sizes, you can setup XROD to show only these units in the pumping unit selection screen. To customize XROD’s pumping unit list, do the following:

Figure 3.11 - Customizing the pumping unit database


1. Click on the “+” symbol on the left of “Pumping Unit Options.” Then, click on “Custom pumping unit list”. This opens the window shown in Figure 3.11.

2. Drop down the manufacturer list by clicking on the down arrow next to “Manufacturer:”

3. Select a manufac-turer you want to add to your custom pumping unit list as shown in Figure 3.12. If this is a new manufacturer for the custom list, all available pumping units will appear in the window on the right side of the screen.

4. You can select the units to include in the custom pumping unit list using drag and drop. To add a unit from the list of available units to the custom database list, you simply drag (click on it with the mouse and hold the left mouse button while moving it) the units you want from the list on the right to the custom list on the left. Or, you can click on a unit once to select it, and then click on the <<Add button (in the middle of the screen). The program automati-cally arranges the units in the proper order (largest stroke length and largest gearbox size first).

5. To remove a unit from the custom-ized list, simply

drag it from the list on the left, and drop it in the list to the right. Or, you can click on a unit once and then click the Remove>> but-ton (in the middle of the screen). To make sure you select the correct pumping unit, highlight it (click on it once with the mouse) and the Name: and Other: fields on the bottom of the screen will show additional information about the pumping unit as shown in Figure 3.13. This is especially useful for manufacturers (for example, American conventional) who have more than one unit with the same designation but different crank types. In such a case, the

Figure 3.13 - Customizing the pumping unit database

Figure 3.12 - Selecting a manufacturer

XROD | 17

Other: field shows the crank type of the unit or other information that helps identify the pumping unit type. This is not the only way to custom-ize the pumping unit database. As discussed in the section dealing with the pumping unit information screen, you can also select a unit you want to add to the custom-ized unit list by first selecting it from the full database and then selecting to use the custom pumping unit list. At that point XROD will ask you if you want to add this unit to the custom pumping unit database. If you do, then select Yes.

6. After you are done customizing the pumping unit list, click on OK.

♦ Measured Pumping Unit ListHere you can enter data for pumping units that are not in XROD’s main database. If you have the dimensions you need for these units you can enter them here to make them a permanent part of your XROD software. To enter dimensions for a pumping unit, do the following:

1. Click on “Measured Pumping Unit List”.2. Click on the “+” symbol (on the left of the pen-

cil symbol). This will open the window shown in Figure 3.14.

3. Enter the data in this window starting with the

Figure 3.15 - Custom pumping unit help

Figure 3.14 - Entering custom pumping unit information


pumping unit manufacturer name.4. Enter the pumping unit data for your pumping

unit.5. When you are done entering data click on

“OK”.If you need help with one of the items you have to enter, press ! to get context sensitive help on that item. For example, if you press ! when you are in one of the pumping unit dimension input fields, the program will show you an outline drawing of the pumping unit with a visual explanation of the pumping unit dimensions (see Figure 3.15). To get more information on any of the dimensions you see, simply click on it with the mouse. For ex-ample, you can click on the “P” box to see detailed help on the P dimension. Also, you can click on the “See Also” hot button to get help for any other pumping unit related item.

3.3.5 Rod Grade Options

Entering Custom Rod GradesTo enter a rod grade that is not in the program’s database, do the follow-ing:1. From the setup win-

dow, click on “Cus-tom Rod Grades.”

2. To add a new rod grade, click on the “+” button (to the left of the pencil icon). This opens up a new win-dow where you can enter the name of the rod you want to add, the tensile strength, and the stress analy-sis method you want XROD to use for this

rod as shown in Figure 3.16. 3. You can also specify that this is a sinker bar by

clicking on the “Sinker bar” option at the lower left hand corner of this window.

4. Enter the rest of the information for the rod you want to add and then click on the “OK” button.

XROD allows you to select any of the available stress analysis methods. Once you enter a special rod grade to the program, it becomes part of the program’s equipment database and it works exactly the same way as XROD’s built-in rod grades.For example, once you enter a special rod grade, you can enter cost information for it, and you can select it from the same rod grade menu that XROD uses for the built-in rod grades.The modify (Pencil Icon) and delete (“X” Icon) options allow you to change or erase custom rod grades you have already entered.

Figure 3.16 - Entering custom rod grade information

XROD | 19

3.3.6 Cost DatabaseWhen you click on this item in Setup, XROD displays a window, shown in Figure 3.17, that allows you to enter or change pumping unit or rod string costs. To enter or change pump-ing unit costs select “Pumping unit costs” This makes the window change by showing a drop-down list box that you can use to select the pumping unit manu-facturer. As shown in Figure 3.18, after you select the manufacturer, XROD displays a mini-spreadsheet that you can use to enter pumping unit costs. To enter the cost for a pumping unit, click on the cell to the right of the pumping unit and enter the cost.When you are done entering pumping unit costs for the pumping units you want, click on OK. Or, if you want to en-ter rod string cost data, Select “Rod string costs” and then select the rod type and rod grade. XROD will display a mini-spreadsheet for you to enter the cost per foot (or per meter) for each rod diameter as shown in Figure 3.19. You do not have to enter cost data for all the rod diameters

you see. Simply enter the cost only for the rod

Figure 3.18 - Pumping unit cost database

Figure 3.17 - Cost Database Setup Window


grades and diameters you use.

3.3.7 Batch Mode OptionsXROD runs a batch pro-cess automatically when in AI mode. This will be ex-plained in more detail in the AI Mode Preferences section of this manual. The following explains the use of the batch utility when operating XROD in non-AI mode.When you click on this tab, XROD displays a setup page that allows you to choose different options relating to the batch run capabilities of XROD. The top portion of this input window al-lows you to select whether you want XROD to print the results of each case it runs in batch, whether to create a summary spread-sheet file, or whether to rerun cases that contain saved output. Also, it lets you choose what action to take when you load a file that contains custom rod grades as shown in Figure 3.20. For example, if you want to update the setup information with the data in the file, then select the option “Update Setup with file’s information.”If you check the Make Printouts check box, XROD will print out ev-ery case you run in batch.

If you check the Create summary spreadsheet

Figure 3.20 - Batch mode options

Figure 3.19 - Entering rod string cost in Setup

XROD | 21

summarizes the values he is interested in. Later Paul can run the same cases in batch mode and create a spreadsheet with the items he is interested in which are different that John’s. Since John ran all 20 cases, the files now contain both input and calculated results. When Paul runs the same cases in batch, he checks the Don’t re-run cases with

check box, XROD will summarize the results of all the files you run in batch in a Excel spreadsheet file. If you select the option “View spreadsheet file”, after you run several cases with the batch pro-cess, the program will automatically create an Excel spreadsheet and will load it into Excel automatically.If you check the “Don’t re-run cases with saved output” check box, XROD will not rerun cases that have saved output. When you run XROD in batch mode, XROD saves the output in the same file as the input data. Also, when you run one case at a time, you can save the output by saving the file to disk when you are looking at the output. The option to avoid rerunning cases that contain output is use-ful when you want to create more than one spreadsheet file using different spreadsheet formats. Once the files have been run with batch, each file will contain all the output calculations. For example, let us assume that there are two different users (John and Paul) who are running XROD and they each have their favorite spread-sheet formats. John can run 20 cases in batch mode and cre-ate a spreadsheet that

Figure 3.22 - AI Mode Preferences

Figure 3.21 - Spreadsheet setup


saved output option to save time. Since the out-put results are already saved in the XROD files, Paul’s batch run will proceed very quickly since all XROD has to do is extract the calculated values that Paul specified in his spreadsheet format from these 20 cases.

Creating and/or Changing spreadsheet formatsAs shown in Figure 3.20, you can click on the “+” icon at the “Spreadsheet Setup” section of the batch window to add a new batch spreadsheet for-mat (design of the spreadsheet). Also, this section lists the spreadsheet formats you have saved. To use one of these spreadsheet formats for your next batch run, highlight it by clicking on it and then click the OK button to exit Setup. If you have not created any spreadsheet formats, the only format that appears is the (Default) format that XROD will use when you run it in the batch mode and choose to create a summary spreadsheet file. To create a new spreadsheet for-mat click on the ”+” button. This opens the spread-sheet setup window that you see in Figure 3.21.The list on the left side shows the columns that are in the spreadsheet now and their order. The list on the right shows additional variables you can add to the spreadsheet. You can use drag and drop to move an item from one list to the other. For example, to add rod string cost as the last column in the spreadsheet, locate it on the table on the right (variables are listed in alphabetical order) and drag it (click and hold while moving with the left mouse button) to the other side. When you drag a value into the table on the left, the cursor shows an arrow that shows where this new value will be added. After you drop the new item in the spread-sheet table, it remains highlighted. Then, to move it up or down in the list click on the Move Up or Move Down buttons below the list of spreadsheet variables. Or, you can click on the Remove>> but-ton to send the highlighted variable back to the “Available values” list on the right.Another way to add items to your spreadsheet is by highlighting a value on the list on the right, high-lighting a value on the list on the left, and clicking

the <<Add Before or <<Add After buttons in the middle of the screen. However, using the mouse is much easier. After you are done designing the for-mat of the spreadsheet, you can save it by entering a name for it in the Format name: field at the bot-tom of the screen. Then click OK to return to the previous screen. From here, you can create another spreadsheet format, or modify or delete one of the existing formats. To modify an existing format, click on its name and then click on the edit icon (pencil). Or, to de-lete an existing format, highlight it, and then click on the delete icon (X).The format you select in this part of the program by clicking on the format name will also be used by XROD when it runs in the AI mode.

3.3.8 AI Mode PreferencesXROD uses these preferences when finding the best designs for each pumping unit type. Figure 3.22 shows the AI Mode Preferences window. In the Rod Preferences section, you have the option of running with either steel rods only or fiberglass with steel on the bottom of the string. There is a drop down to select your preferred high strength rod type, fiberglass rod, and sinker bars. The high strength rods you select will be recom-mended only if API grades C or D are overloaded. XROD can design the sinker bar section for you, and has an option to convert to no-neck bars if needed (if regular sinker bars with elevator necks are overloaded). There is also an input field for the service factor to use in the calculations. Another option is to select to use your customized pumping unit list (if you created one) to find if any of the pumping units you have available can be used to get the target production you want.When you select to use the customized pumping unit list, the program will automatically check the different pumping unit manufacturers it finds in your customized list and will automatically list them and select then in the AI Mode Prefer-ences window. Also, you can choose to use the

XROD | 23

general pumping unit list if needed (for example, if you customized list of units does not contain the pumping unit size needed for your target produc-tion).Rod tubing friction has a special section in XROD. You can select to use average friction coef-ficients for upstroke and downstroke, or a multiple of the average for high friction applications such as wells with paraffin, scale, or deviation.You can also select the power meter type you have and whether to use motor speed variation in the calculations.Please note that XROD automatically recommends a NEMA D motor size only. If you want to use an Ultra high slip motor, from the batch run log of XROD, double-click on the design you want, then switch to non-AI mode and then you can change the motor to a different type and run the case again.

XROD | 25

4 Running XROD

To start XROD, double click on its icon. After a few seconds you will see XROD’s introductory window and then the XROD main window. When XROD first loads, only the new file, open file, setup, and help buttons are active on the toolbar. If you have not set up XROD then do so before en-tering a new case (see Chapter 1 for information on setting up RODSTAR). It is especially important to go to the “AI Mode Preferences” after you click on the Setup icon on the toolbar to select the rod type, your preferred high strength rods and pump-ing unit manufacturers to consider, etc, since these are the options the program will use when running in the AI mode.

4.1 XROD’s User InterfaceXROD has a user-friendly interface that simplifies and speeds up data entry. The program uses stan-dard Windows features along with other unique features we designed to make entering and changing data as easy as possible. Figure 4.1 shows how to access the most recently saved files and select the file you want to load into XROD. If you are not familiar with Microsoft Windows, please take some time to study your Windows manual. Teaching you how to use Windows is beyond the scope of this manual (although many Windows proce-dures are explained). By taking the time to understand and learn how to use Windows, you will be able to effectively use not only XROD, but any other Windows program.

XROD’s interface has most of the elements that are common to all Windows programs. For exam-ple, all Windows programs have a menu bar with drop-down menus and a control menu box at the top left corner. You can access all menu items using either the mouse or the keyboard. Using the mouse is by far the easiest way. When selecting an item from a menu, visual clues tell you what will happen next.

♦ An item followed by no markings starts an action. (For example, click on File and then click on New.

♦ An item followed by an ellipsis (...) needs more information before taking action; normally, the additional information is entered into a dia-log box. (For example, click on File and click on Open…)

Figure 4.1 - The most recently saved file list

26 | Running XROD

An easy way to load files you recently saved:XROD has a most-recently-used file list on the File menu, as shown in Figure 4.1. Selecting the Recent Files sub-menu will show you up to nine of the most recently accessed files. A file is placed at the top of the list whenever it is loaded, or saved with a new name. This list can also be accessed by clicking on the drop-down button on the toolbar to the right of the open file icon.You can only open XROD files in the AI Mode. When in AI Mode you can also open all ROD-STAR file types and also RODDIAG and XDIAG files. However, when loading XDIAG or RODDIAG file, please remember to enter a target

production before running the program. Also, when you load a RODDIAG or XDIAG file in the AI Mode, the program will ignore the existing system data other than data from the first input window and target production and will recom-mend new system designs for each pumping unit type you selected in the AI Mode Preferences in Setup.

4.1.1 XROD’s Help SystemXROD has a powerful help system that provides context sensitive help for every input item. It al-lows you to locate help on any subject relating to system design and simulation. It even includes a complete artificial lift glossary that provides in-stant access to definitions for hundreds of artificial lift terms. Also, the help system helps you learn how to use it by including extensive help on itself.Click on the Help drop-down menu to see the Help menu choices which are:

♦ Contents.. ♦ Index.. ♦ Search.. ♦ About XROD..

To see XROD’s version number, and your senti-nel’s serial number, click on About XROD.Click on Contents to see a list of items XROD can provide help for. As you can see, XROD shows text and pictures in its help screen. For example, XROD displays a picture of the toolbar and in-structs you to click on the button you want help for. Using the mouse, you can resize or move the Help window.Next, click on Help and then click on Glossary to see an alphabetical listing of artificial lift terms. To see the definition of any of the terms in the glos-sary, click on it. For example, click on API grav-ity to see a definition. Also, you can click in the list of items in the Glossary and then type a letter to go to the terms that start with that letter. For, example, to find the definition for Permissible load

Figure 4.2 - RODSTAR’s Artificial Lift Glossary

XROD | 27

diagram, press “P” and then click on Permissible load diagram.XROD has context sensitive help for each input item. To access the help, simply press ! while in the input field in question.

4.2 Entering Rod Pumping System Data into XROD, AI modeXROD has greatly simplified the rod pumping system design process. With it’s built in expertise, minimal input data is needed.First be sure to select all the appropriate setup op-tions in the setup window. Refer to Chapter 3 to setup XROD.When entering data in XROD’s input windows, it helps to know the following:

♦ To replace the contents of an input box,

double click it before typing in it. ♦ If an input window contains a name that is

made up of more than one word, double click any word to select it. Then, to replace it, simply type a new word.To enter rod system data in XROD for the first time, click on the first icon on the toolbar or open the File menu and select New. This opens the Well Information input window, shown in Figure 4.3. You can move this window with the mouse by dragging it to the desired location. Also, you can use the mouse to resize this input window.XROD’s input windows use the following unique color scheme:

♦ Required data input fields appear with a yellow background. You must enter data in these fields before closing the window, continuing to the next window, or running the calculations.

Figure 4.4 - XROD’s Production Information window

Figure 4.3 - XROD’s Well Information window

28 | Running XROD

♦ The active input field or list box appears in cyan.This color scheme helps you to easily see what data you need and where you are in the input window. There are two ways of moving around in an input window. You can click the input field you want, or you can enter data in order by pressing T to move forward from field to field. Also, you can press S+ T to move backwards. After enter-ing data in fields with yellow background color, their color changes to white when you move to the next field.You can get context sensitive help for any input field by pressing !. Please use the context sensi-tive help as often as possible because it contains important information that will allow you to make

better use of XROD. Also, the context sensitive help makes you aware of program assumptions or limitations.With all of your information in setup the only required fields for input are the following:

♦ Well Name ♦ Pump Depth ♦ Target Production

After the well name and pump depth are entered, click the next arrow and enter the target produc-tion in the Production Information window as shown in Figure 4.4. Click the next arrow again and you will be prompted to save the file. After saving the file, click the run button on the toolbar and the batch log window will open and display the progress of the batch run.The batch log page will display all of the system

Figure 4.5 - XROD’s AI Mode Batch Log

XROD | 29

designs for each pumping unit manufacturer along with the AI score for each as shown in Figure 4.5. If a system could not achieve the target produc-tion, a message will be printed on the batch log about this problem.After all the runs are completed you may double-click on any individual file names highlighted in blue to find the full report on this system design recommended by XROD. To return to the batch log, click on the close button on the bottom right corner of the Output Results window. From here you can open another design shown on the batch run log. If you wish to change the input information in any of the individual system designs, double-click on the case file name to see the detailed report for this case. Then click the AI button to switch out of the AI Mode button on the toolbar. You now can change any of the parameters of the system and run an individual case by clicking the run button. Please note that when you switch out of the AI batch mode, you cannot go back to the AI batch log unless you rerun the case after switching back to the AI mode.

4.3 Entering Rod Pumping System Data into XROD, non-AI modeThe following procedure is done using XROD in non-AI Mode. This will behave like RODSTAR but with the added scor-ing feature that comes with XROD. More about this feature can be found in section 5.3 of this manual.When entering data in XROD’s input windows, it helps to know the fol-lowing:

♦ To replace the contents of an input box, double click it before typing in it.

♦ If an input window contains a name that is made up of more than one word, double click any word to select it. Then, to replace it, simply type a new word.To enter rod system data in XROD for the first time, click on the first icon on the toolbar or open the File menu and select New. This opens the Well Information input window, shown in Figure 4.6. You can move this window with the mouse by dragging it to the desired location. Also, you can use the mouse to resize this input window.XROD’s input windows use the following unique color scheme:

♦ Required data input fields appear with a yellow background. You must enter data in these fields before closing the window, continuing to the next window, or running the calculations.

♦ The active input field or list box appears in cyan.This color scheme helps you to easily see what data you need and where you are in the input window. There are two ways of moving around in an input window. You can click the input field you want, or you can enter data in order by pressing T to move forward from field to field. Also, you can press S+ T to move backwards. After enter-ing data in fields with yellow background color, their color changes to white when you move to the

Figure 4.6 - The Well Information input window

30 | Running XROD

next field.You can get context sensi-tive help for any input field by pressing !. Please use the context sensitive help as often as possible because it contains important informa-tion that will allow you to make better use of XROD. Also, the context sensitive help makes you aware of program assumptions or limitations.

4.3.1 Entering Well Information DataIf you entered a company name in Setup, it appears in the Company name field. This saves you from hav-ing to enter the same company name every time you enter data. The date defaults to the date in your computer’s memory. If the date in your com-puter is not correct, you can type over it. The well name is required because XROD uses it to create the default file name when you save data to disk.The pump condition panel allows you to select pump condition and pump efficiency or pump fillage. To select one of these input fields click on the input field or its label. Press ! while in one of these fields for some useful information.The option to have the pump condition and fil-lage calculated works along with the Production Information window. When you select this option you must enter a pumping speed and IPR data in the second input window. Based on the SPM you enter, XROD calculates the pump displacement versus maximum available production from the IPR data as well as the final pump intake pressure. XROD uses an iteration scheme to converge to the correct pump condition and pump fillage that will result from the SPM you enter, along with the calculated pump intake pressure.

The Production Information window also gives you the option of having XROD calculate the required pumping speed based on a target production you enter. However, the option of calculating the SPM from your target production is only avail-able if you select a full pump. For fluid pound or gas interference, you must enter a pumping speed in the Production Information window.

Other input data in the Well Information window:CommentYou can enter a comment about the case. When clicking this button you will find the input window for the cover page. This page is regenerated when viewing the report so that you can run a case and edit the cover page to comment on the results of the run. For more information see chapter 3.Pump Load Adjustment The pump load adjustment allows you to increase the fluid load picked up by the plunger. Usually this is unnecessary. However, this input allows you to account for extra downhole loads due to exces-sive downhole friction (for example due to wellbore

Figure 4.7 - The Production Information input window

XROD | 31

deviation), or due to the “plunger effect” of large sinker bars. It is recommended that you use zero for this number unless you have more than 1000 feet of large sinker bars such as 15/8’’ or 1¾’’ bars in 2’’ tubing. The value of this number in pounds is typically 5% to 10% of the pump depth in feet. For example, for a pump depth of 6000 feet, enter a value of 300 to 600 pounds (but only if you use more than 1000’ of large sinker bars). XROD will not allow you to enter a value that is larger than 15% of pump depth. Also, you can use this input to add pump load for more conservative predic-tions.

Please note that XROD assumes that the tubing-casing annulus is full of oil. It cal-culates the specific gravity of the oil from the API gravity you enter. If you do not agree with this assumption then change the oil API gravity to correspond to the specific gravity you want XROD to simulate. For example, if you want to simulate water in the casing-tubing annulus instead of oil, then enter an API gravity of 10 (which cor-responds to a fluid specific gravity of 1.0).

Percent water cutThe percent water cut input along with oil API gravity allows XROD to calculate a default specific gravity for the produced fluid. Also, it uses this data to calculate $/bbl (or $/m3) electricity costs.

Oil API gravityXROD uses the oil API gravity to calculate fluid load on the plunger and the default specific grav-ity of the produced fluid.

Also, as discussed above, XROD uses this num-ber to calculate the specific gravity of the fluid in the casing-tubing annulus which it assumes to be 100% oil.

Fluid specific gravityXROD uses the oil API gravity and percent water cut you entered to calculate the default specific gravity of the produced fluid. The program will display this value when it prompts you to enter the fluid specific gravity. XROD calculates the default specific gravity without considering free gas. This is okay for designing new wells since we prefer to be more conservative. However, if you want to simulate an existing system that produces gas, you must enter a lower number than the one calcu-lated by XROD. With some experience and with “history-matching” between predicted and actual dynamometer cards you can come up with effective specific gravities that will accurately model your rod pumping systems. If you use a specific gravity that only considers liquids, it will result in higher

Figure 4.8 - The inflow performance relationship (IPR) plot

32 | Running XROD

predicted loads, power consumption, etc.If you are designing a new system and you are not sure what the specific gravity is, use the higher value you expect to have to make sure that your system will not be overloaded when in operation. However, when matching measured dynamometer cards, use a specific gravity that is as close as pos-sible to the actual value.After you finish entering data for the Well Infor-mation window click on the next screen button (right arrow) on the toolbar to open the Production Information input window. To move back to the previous window, simply press the left arrow icon on the toolbar.

Remember that pressing @ converts to the op-posite system of units. For example, if you selected English units but want to enter the pump depth in meters, press @ before entering the value. If the value for any field with units has already been

entered, pressing @ will show it in the opposite units.

4.3.2 Entering Production InformationThe Production Information input window allows you to enter a fluid level or pump intake pressure as shown in Figure 4.7. Also, you can select to enter a pumping speed, enter a target production (the program will calculate the pumping speed to get the target production), or you can select to calcu-late the target production from inflow performance data.If you choose to enter IPR data, the Production Information window expands to reveal the data you must enter. This includes the correlation you

want to use for the inflow performance relationship (IPR), the depth from surface to the middle of the perforations, the static bottom hole pressure, and bubble point pressure. Also, you can enter from one to 10 test points. If you select to use the Vogel method for the oil IPR calculations then you only need one point. If you use Vogel and enter more than one point, then only the first point is used. You can enter more than one test point if you use the Fetkovich method. The pressure that cor-responds to each production test point can either be pump intake pressure or flowing bottomhole pressure (in the middle of the perfs). To add a new pair of Pi and Fluid production data, click on the add button (top right) icon. To delete a set of data points, click on the remove icon (bottom right).

You can get help for any input item by pressing ! when in the input field or by clicking on the ques-tion mark icon on the toolbar.If you do not know what the bubble point pres-sure is, but you know the well is producing below the bubble point pressure, then leave the bubble point pressure field blank and click on “Producing below bubble point” or in the check box next to it. After you enter the last piece of IPR data, click to a different input field, press T or click on the “Update prod.” button to allow RODSTAR to calculate the maximum oil, water, and fluid pro-duction rates and target production. You can see the IPR plot by clicking on the IPR Plot... button (under the target production field). When the IPR plot is displayed as shown in Fig-ure 4.8, you can move the cyan line that you see on the plot with the mouse to see the calculated production rate for any bottomhole pressure. To move this line, point to it with the mouse until the mouse cursor changes shape and then drag the line to any pressure point on this plot. As you are moving this line, the producing bottom hole pres-sure, pump intake pressure, oil production, water production and total fluid production are dynami-cally recalculated. You can print the IPR plot you see on the screen by clicking on the Print button at the bottom right hand corner of the screen, or

Figure 4.9 - Fetkovich ‘n’ value

XROD | 33

you return to the production information screen by clicking on Close.RODSTAR offers you the option to enter the val-ue of n for the Fetkovich IPR correlation as shown in Figure 4.9. The window includes a check box, labeled Calculate ‘n’, that tells XROD whether you want to enter the value or have XROD cal-culate it from your data. If you enter only one test point, XROD uses a value of 1.0 for n unless you select to input your own value. However, if you enter two or more test points, XROD calculates n from a log-log plot.If you enter inflow performance (IPR) data, XROD can calculate the pump intake pressure using the target production you have entered (see Figure 4.10). You can select to have XROD calcu-late the pump intake pressure from the IPR data, or if there is no IPR data available, you can enter a pump intake pressure or fluid level yourself. Usu-ally, for new systems, it is recommended that the system be designed for the highest possible fluid load on the plunger. This is accomplished by en-tering a fluid level that is equal to pump depth.

4.3.3 Entering Pump and Tubing Information DataOn the third input screen, you can select the tubing size, tubing anchor depth (if anchored), pump type, plunger size, and the upstroke and downstroke rod-tubing friction coefficients. Also, for shallow, high rate wells, you can include fluid inertia effects. If you select to include fluid inertia1 effects then you must also enter the fluid compress-ibility index. For more information on this option read the discussion that follows later in this sec-tion, or use the context sensitive help system.

1 Fluid inertia effects are dynamic effects that increase fluid load on the plunger in wells less than 4000 feet with pump plungers larger than 2.0 inches

You can select the pump plunger size from a list of standard sizes, or you can enter a non-standard size by selecting “Other” from the list of plunger sizes. If you are simulat-

ing a full pump and you entered a target produc-tion, you can select to have XROD recommend the pump plunger size for you. This option is only available when you enter a target production and select full pump for pump condition. Please note that the pump type you select affects the plunger size that the program will recommend. It may be interesting to make one run with an insert pump type and one with a tubing pump to see what XROD recommends.

Other input data in the Pump and Tubing Information window:Rod-tubing friction coefficientsFor rod-tubing friction , XROD allows you to enter upstroke and downstroke friction coefficients yourself, or you can have the program calculate them for you. If you do not know what to enter, then choose to have XROD calculate the rod-tub-ing friction for you. The friction factors calculated by XROD are estimates for average friction for a vertical wellbore. If you are simulating a system with excessive downhole friction, you must enter your own rod-tubing friction coefficients for more accurate results. There are several downhole con-ditions that increase rod-tubing friction such as: wellbore deviation, a well with heavy oil produc-tion, paraffin or scale problems, etc.

The most accurate way to figure out the rod tubing friction in XROD is to import a measured dynamometer card from a ROD-DIAG or XDIAG file (in non-AI mode). Then, “history-match” this actual card by manually adjusting the friction. You do this by varying the upstroke and downstroke rod-tubing friction coefficients until the sur-

Figure 4.10 - Options for calculating pump intake pressure

34 | Running XROD

face dynamometer card predicted by the pro-gram matches the measured dynamometer card. This technique allows you to find the rod-tubing friction that gives the best results when simulating this system. From then on you can use these friction factors every time you simulate this pumping system.

Please note that this “history-matching” technique works only if the dynamometer card that you mea-sure corresponds to a pump condition that XROD can simulate (full pump, fluid pound, or gas inter-ference). For example, if the pump is worn out or is hitting up or down, etc., then this technique will

not work as well. This is because you will be unable to get a good match between predicted and mea-sured dynamometer cards. If you do not have a measured dynamometer card, use the following guidelines for entering rod-tub-ing friction coefficients in non-AI mode:1. First select to have XROD calculate the rod-

tubing friction coefficients for you. You can use these calculated values as guidelines to decide what values to enter yourself to better simulate your rod pumping system.

2. For heavy oil or for wells with paraffin or scale buildup, use 2-3 times the value calculated by XROD. You can use the same guideline for deviated wells when the deviation is close to the bottom of the wellbore.

3. For deviated wells with the deviation close to the surface you may need to enter a larger number such as 4-6 times as high as the values calculated by the program. Also, it may be appropriate to use different values for upstroke and downstroke frictions to better match your downhole conditions.

Figure 4.12 - Steel rod string design options

Figure 4.11 - Rod string entry options

XROD | 35

Buoyancy effectsThe option to include buoyancy effects should be left unchecked in most cases. This is because buoyancy does not cause buckling of the rod string. However, for fiberglass-steel rod strings, after the design is finalized, It is recommended that an ad-ditional run be made including buoyancy effects to ensure that the fiberglass portion of the rod string is not in compression. If it is in compression, then more sinker bars must be used, the pumping speed need to be reduced, or both.When buoyancy is not included, the bottom of each rod section except the last section should have a positive stress. Otherwise the rods may be going into buckling. It is normal for the very bottom of the rod string to be in compression if you enter a pump friction that is not zero (a minimum pump friction of 200 lbs is recommended).For more information on the theory behind these recommendations, please read SPE paper number 25416 “Interpretation of Calculated Forces on Sucker Rods” by J. F. Lea and P. D. Pattillo. Pre-sented at the Production Operations Symposium in Oklahoma City, March 1993.

Fluid inertia effectsIf the well depth is less than 4250 feet and the pump plunger size is larger than 2.00 inches, XROD allows you to consider fluid inertia effects. These dynamic effects become important in wells with plungers larger than 2.0” and pump depths of 4000 feet or less. However, there is no exact “magic” depth for which fluid inertia becomes important. Therefore, XROD allows you to include these effects for wells up to 4250 feet deep and with a plunger size equal to or larger than 2.0”. Another important factor is fluid compressibility. The more compressible the fluid is, the less promi-nent the fluid inertia effects are.If you include fluid inertia effects, XROD will prompt you for the fluid compressibility index. The default is 3 but you can vary this number between 1 and 7 (x10-6 psi-1). The compressibility index tells XROD how compressible the fluid in the tubing is. The value of the compressibility index af-fects the shape of the predicted dynamometer cards (surface and downhole). If you are not sure what number to use, experiment with different values until you can match measured dynamometer cards for the well you are simulating.

Figure 4.13 - Fiberglass rod string design window

36 | Running XROD

When you include fluid inertia effects, pump efficiency becomes a variable that affects the dynamic fluid load on the plunger. Therefore, using 90% pump efficiency gives higher peak polished rod load than using 80%.

The option to include fluid inertia effects is only available if you are modeling a full pump. Please do not confuse fluid inertia effects with the mo-ments of inertia of the pumping unit that have to do with gearbox torque due to prime mover speed variation. Fluid inertia effects refer to additional dynamic forces on the plunger caused by the pickup and rapid acceleration of the fluid load.XROD simulates fluid inertia effects with a second wave equation that models the pressure waves in the fluid in the tubing. This increases simulation accuracy by accounting for pressure pulses travel-ing up and down in the tubing fluid. These pres-sure waves have a direct affect on the pump plung-er. Since the program has to do many additional calculations when you include fluid inertia effects, XROD may take 60%-80% longer to run.

4.3.4 Entering Rod String DataThe fourth input window deals with the rod string design. As Figure 4.11 shows, you can select one of the three available rod string entry options:XROD Steel design, XROD Fiberglass-Steel de-sign, or Manual rod string entry. The symbols for these options are explained in Figure 4.11.

XROD Steel Design

If you select this option, XROD displays a window such as the one shown in Figure 4.12. Here, you can select the maximum and minimum rod diam-eters to consider, whether to include sinker bars, the service factor, and additional rod costs.If you want to include sinker bars then you must enter the diameter and length of the bar (or sinker rod). XROD does not calculate the length of the sinker bar section because there is no industry consensus on how to design sinker bars. However, XROD will design the rod string above the sinker bar section you specify. XROD attempts to design an optimum rod string based on the rod grade and the maximum and minimum rod diameters you enter. First, XROD figures out how many rod tapers are needed. Then, it automatically adjusts the length of each section until the stress loading is the same at the top of each rod section. This equalizes and minimizes stress loading on the rod string. This “stress bal-ancing” approach gives the lowest cost rod string with equally distributed stress loading, for the rod grade you select.This approach works the same regardless of steel rod grade or type. For example, you can have XROD design a Corod rod string for semi ellipti-cal “Ultra” Corods using a maximum diameter of 17/16”, a minimum diameter of 13/16”, and a 375’ section of 1 5/8’’ sinker bars on the bottom. XROD uses only the rod sizes it needs. For exam-ple, if the loads are not high enough to require the use of the 17/16” rod diameter then XROD will go to the next size (16/16”). If this is still too big, it will use the 15/16”.The maximum rod loading used by XROD to de-

Figure 4.14 - RODSTAR Designed Fiberglass-Steel Rod String

XROD | 37

cide when the next larger diameter rods are needed is 95% by default. However, you can change this number if you like by going to the Setup “De-faults” window.

Fiberglass/steel XROD designIf you select the option to have XROD design a fiberglass-and-steel rod string, you will see the data input screen in Figure 4.13. For example, let us say you want to use a design with fiberglass rods on top followed by a tapered steel section with 1” and 7/8” rods, and then 375 feet of 1” sinker bars. XROD is able to design this rod string for you. Also, it balances the steel design under the fiber-glass section (for two or more rod sections) so that there is equal stress loading at the top of each sec-tion as shown in Figure 4.14. This Figure shows a fiberglass-steel rod string designed with XROD. XROD can design tapered steel rod strings under the fiberglass section for any type of steel rod, including non-API high strength rods, and Corods. If you want to fine-tune a XROD design, in non-AI mode, select to enter your own rod string design by clicking on the manual rod string entry icon. XROD will show you the current rod string design in memory as if

you entered it yourself. Then, you can make any changes you want to the rod string without having to reenter everything.Also, you can have XROD design the rod string while calculating the pumping speed and plunger size, to get the target production. However, be-cause of the complexity of the calculations, si-multaneous use of all or most of XROD’s “smart” options will result in longer run times. This is especially true if you also select to include the ef-fect of prime mover speed variation. Also, depend-ing on the case, XROD’s run time may be longer if you enter a target production that is too large for the pumping system.If you select only sinker bars on the bottom (with-out regular steel rods between the fiberglass and sinker bar) then XROD will calculate the length of the sinker bar section for you. If you select both sinker bars and a tapered steel design between the sinker bars and the fiberglass rods, then you must enter the length of the sinker bar (or sinker rod) section. XROD will determine the length and diameters of the tapered steel portion based on the maximum and minimum diameter limits you enter.

Figure 4.15 - Selecting rod grades in Non AI-Mode

38 | Running XROD

simulate, or to modify a design that XROD itself came up with (when you select to have the pro-gram design the rod string for you). This is not a good option to use when you first design a new system because it requires the most work and expe-rience.When you select this option, you can enter data for either steel or fiberglass rods as Figure 4.15 shows. This can only be done in the non-AI mode. You can enter the number of rod sections, the service factor you want to use, and rod string data for up to eight rod sections. For each section, you can select the rod type or grade, diameter, and length. For Fiberflex fiberglass rods you can also specify the sucker rod length.If you select one of the fiberglass manufacturers listed on the drop down list next to the rod grade input field, the program knows the weight per

foot and modulus of elasticity and will not prompt you for them. The program warns you about rods that do not fit in the tubing. Also, it warns you if

XROD may reject a steel rod diameter if it is not needed. For example, if you asked XROD to design a rod string with fiberglass on top, a tapered steel section under the fiberglass, and a 500 foot 1.5 inch sinker bar section on the bottom. XROD will determine the fiberglass diameter and length you need, and the steel rod section and tapers you need. If XROD cannot balance the steel rod string design because the 3/4’’ section is not needed, it will not use any 3/4” rods. Another interesting capability of XROD is that if you use continuous rods (Corod or Prorod) instead of regular rods under the fiberglass, it may skip a rod diameter, if it has to, in order to balance the rod string stress loading. This is not a bug. Some-times the program has to do this to successfully balance the steel portion of the rod string.

Entering Your Own (Manual) Rod StringThis option is primarily used for entering rod string data for an existing system you want to

Figure 4.16 - Pumping unit manufacturer list

XROD | 39

the rod string length is shorter or longer than the pump depth. The total length of the rod string can be up to 50 feet shorter than the pump depth. However, it cannot be longer than the pump depth. For example, if the pump depth is 5000 feet, you can enter a rod string that is between 4950 and 5000 feet. When entering rod string data for the first time, XROD shows a default length for the last rod section equal to the difference between the pump depth and the rod string length you entered so far.Selecting the option to enter your own rod string gives you maximum flexibility. However, it re-quires the most expertise to come up with a good rod string design. You can use this option to select different rod grade or manufacturer for each rod section. In general, this option allows you to enter any rod string design, no matter how unusual. The minimum length you can enter for any rod section is 25’ (length of a single sucker rod).When entering the rod string data manually, XROD allows you to add and remove rod sections from anywhere in the rod string, instead of only

at the bottom. The window has icons on the left side for inserting a rod section, for removing a rod section, or for moving a section up or down. For example, if you want to remove a rod section, first click on it and then click on the Delete Rod rod section icon. To add a rod section, click on an existing rod sec-tion and then click on the Insert/Add Rod Sec-tion icon. The new section will be added below the selected section.XROD asks for confirmation whenever you re-move sections from the rod string, whether by us-ing the Remove rod section button or by reducing the number of rod sections.

The meaning of the term “Sinker Bar” in XRODIn XROD, the term “sinker bar” means a steel rod that is made specifically to be used at the bottom of the rod string for weight such as 1 3/8”, 1½”, 1 5/8”, etc. The term “sinker rod” means a regular rod such as a 1” or 7/8” rod that is placed on the

Figure 4.17 - Measured pumping unit list

40 | Running XROD

bottom of the rod string for weight. For a 1” or 7/8” rod to be considered a “sinker rod” it must be larger than the diameter of the rod above it.

When entering the rod string manually, make sure you select “Sinker bars” in the list of rod grades for sinker bars as shown in Figure 4.14. Do not select “Steel” rod type and then “Other” for the rod size.

4.3.5 Entering Pumping Unit DataThe pumping unit input screen allows you to select a pumping unit from the database that comes with XROD, or from your measured pumping unit database (if you entered your own pumping unit dimensions in Setup). Another option is to enter a pumping unit ID.The pumping unit ID is a unique string of letters and numbers. XROD displays the pumping unit ID along with other unit information after you select a unit. If you make a note of this unit ID (in the well file for example), you can use it to specify

the pumping unit instead of having to select it from the list. This is a unique ID for each pumping unit in the program’s database.

Selecting a pumping unit manufacturerXROD allows you to easily select a pumping unit manufacturer and unit size with drop-down list boxes. To display the menu with all pumping unit types available, click on the drop arrow next to the “Manufacturer” field (see Figure 4.16). This is a scrollable list of all units in the program’s database in alphabetical order. You can go to the top of the

list by pressing }. You can jump to the bottom

of the list by pressing ~. You can also move up

or down by pressing O (Page up) or N (Page Down). A convenient way to move through the list is to press the first letter of the unit name you want to use. For example, to locate the National “E”

Series pumping unit entry, you can press n and the highlight bar will jump to the first name in the

Figure 4.18 - The custom pumping unit list

XROD | 41

list that starts with N. Then simply click on the National “E” Series entry. At the top of the list of pumping unit manufacturers is the item “Mea-sured pumping units”. This option allows you to select a unit for which you entered geometric data in Setup. When you select the “Measured pumping units” option, XROD will display a list that only shows the measured pumping units, as Figure 4.17 shows. As Figures 4.16 and 4.17 show, there is a check box that allows you to use the custom pumping unit list instead of the main pumping unit list. If you check this option, before you select a unit, the Manufacturer list will show a shorter list that contains only the manufacturers you selected in Setup in your custom unit list as shown in Figure 4.18. When the “Use custom pumping unit list” option is checked, when you select a pumping unit, you will see a short list containing only the unit sizes you selected for your customized list for this manufacturer.

After you select a manufacturer you can use the same procedure to select the unit size you want from the pumping unit drop-down list box . You can move through this list the same way as with the pumping unit manufacturer selection menu. The pumping units on this menu are ordered from largest to smallest stroke length, gearbox size, and structure size. However, if the window shows the pumping unit name (for old units) the units are listed alphabetically.When you enter a unit, the Unit ID, the program automatically displays the unit that the ID corre-sponds to. XROD displays the information nec-essary for you to correctly identify your unit. For example, for American conventional units you will see that certain unit sizes appear more than once on the selection list. However, they have different cranks.

How to add units to the custom pumping unit list

Figure 4.19 - XROD recommends a unit size based on target production

42 | Running XROD

You can use the “Use custom pumping unit list” check box to add units from the main list to your custom list. For example, if you run across a pump-ing unit that is not in your custom list yet, clear the “Use custom pumping unit list” check box so that you can use the general pumping unit list.After you select the pumping unit then click on the “Use custom pumping unit list” check box. XROD asks if you want to add this pumping unit to the custom pumping unit database. Select Yes to add this unit to your custom list. The program will add this unit to the custom list and also switches to the custom list.This option allows you to add units to your custom list without having to do it from Setup. To remove units from your custom list or to add more than one unit, go to the setup window and customize the list of units as described earlier in this manual.You can also use this feature as a way to main-tain an inventory of available pumping unit types. When this custom pumping unit list has been completed, you can select to have XROD use this list when designing your system. (see AI Mode Preferences in Setup). This way, you can quickly find if a unit in your inventory will work for the new system design.

Selecting to enter a pumping unit IDThe unit ID option is the fastest way to enter pumping unit information if you already know the pumping unit ID for your unit. You can see the pumping unit ID on the pumping unit entry window after you select a unit. Once you locate your unit, you can make a note of its ID in the well file. Then, the next time you want to use this unit, you can select to enter its ID. For example, for a Lufkin Mark II M-456-305-144, the unit ID is ML32. To identify some units correctly, it is necessary to know the crank number since they may have the same API designation but different geometric dimensions depending on crank number (primarily units made by American International Manufac-

turing Company).TIP: If your unit is not listed in XROD and you do not have the unit dimensions, then use a unit that is closest to it. As long as you use the same unit geometry and a unit with the same stroke length and gearbox rating, the results should be close to actual as long as the pumping unit is the same unit type as the one you selected.If after you enter a pumping unit ID XROD dis-plays “The pumping ID you entered is not valid” this means that ID you entered is not recognized by XROD. This can happen for two reasons:1) You entered the wrong ID such as R0 (which does not exist), or CL901 instead of CL91.2) You have erased the pumping unit file by acci-dent, or the pumping unit files are not in the same directory as the program.

XROD Recommended unit sizeIf you enter a target production instead of pumping speed, XROD will display a recommended pump-ing unit size to help you select a pumping unit. This recommendation can be very helpful if you are designing a new pumping system and must decide what size unit you need. XROD recommends a unit size based on the type of pumping unit you selected. For example, if you select a Lufkin Mark II then XROD’s recommendation will be for a Mark II unit. If you select a Lufkin Conventional, then its recommendation will be different since it is for a conventional unit. The program will automatically select the closest unit available from the selected manufacturer as compared to the size it recommends. XROD in non-AI mode makes this recommendation without running through the predictive calculations. Therefore, it may not nec-essarily recommend the best pumping unit size for your application. However, in most cases it should be pretty close to the size you need. If you want the program to recommend the best pumping unit, then use the AI mode.There are other important factors that you must consider when deciding what unit size you need.

XROD | 43

These include: available used pumping units, ex-pected changes in well conditions, desired pump-ing speed, etc. When you enter data for a case for the first time and you are at the pumping unit selection screen, XROD will not only display the recommended unit size, but will automatically se-lect the unit closest to the recommended size from the available list. If you do not want to use the unit recommended by XROD then select another one. The recommended unit size is a push button, as shown in Figure 4.19. So, whenever you want to return to the pumping unit size recommended by XROD, just click the button and XROD will automatically select the unit size that is closest to the recommended size. In general, the size recommended by RODSTAR will be close to the minimum required unit size to avoid overloading the unit. Also, XROD’s recom-mendation depends on the manufacturer and unit type you select and whether you are using steel rods only, or fiberglass with steel on the bottom. In some cases you may be able to use a smaller unit by selecting a pumping unit geometry that is better suited for your application. There are several factors that determine what unit is best. They include, cost, gearbox loading, system efficiency, rod com-pression, minimum polished rod load (indicates separation of the polished rod from the carrier bar if close to zero), etc.

Selecting crank hole number and crank rotationAfter you select a pumping unit you must select the crank hole number, and the direction of rota-tion with the well to the right (if you are using a unit that can rotate either way). For units with a required direction of rotation, like the Mark II , Torqmaster, Lufkin Reverse Mark, or American Producer II, the program will not allow you to change crank rotation. For units that can rotate either clockwise or counterclockwise, XROD de-faults to the direction of rotation that will usually give the lowest torque. However, this default direc-tion of rotation may not always be ideal for your system design. To find out for sure which rotation

is best for your system you must make two runs: one with clockwise crank rotation and one coun-terclockwise. Then look at the effect of rotation on gearbox torque, system efficiency, rod loading, etc.

Entering your own pumping unit dataIf the pumping unit you want to simulate is not in XROD’s database, you can enter your own pumping unit dimensions. To enter the data in the program you have to first access the setup screen of XROD (click on fourth button on toolbar). Then, click on the “+” next to “Pumping Unit Options” tab and select “Measured Pumping Unit List” as explained in section 3.3.4 in this manual. Then, select to add a new unit to enter data for a pump-ing unit not in the program’s database.The data you must enter consists of geometric dimensions as defined in the API 11E publication. You can get these dimensions from the pumping unit manufacturer or measure them yourself. Or, you may be able to find most of the dimensions you need from catalogs or blue prints. For old units without an API designation on their nameplate, you may be able to put together an equivalent API designation. Look at the gearbox nameplate for the gearbox rating in thousands of in-lbs. Measure the stroke length, and try to decipher additional infor-mation from the unit’s nameplate for the structure rating, stroke length, and structural unbalance. If the nameplate is legible then write down the unit’s serial number or order number. If the unit’s manufacturer is still in business, you may be able to get the data you need from the serial number or order number. For help in locating dimensional data for pumping units not in the manual call Theta Oilfield Services, Inc..XROD allows you to enter data for Conventional, Mark II, Air Balanced, Enhanced Geometry, or Long Stroke units. When you enter your own pumping unit dimensions, XROD calculates and displays the stroke length based on the dimen-sions you enter. For all pumping unit types you must first enter the name of the manufacturer, the unit name or model number, the gearbox rating

44 | Running XROD

in thousands of inch pounds, the structure rating in hundreds of pounds, and the maximum stroke length in inches. From these numbers XROD puts together the API pumping unit designation. The API pumping unit designation is a standard way of describing the size and capacity of pumping units as the following example explains:The first number is the gearbox rating in thousand inch-pounds. In this example the gearbox rating is 320,000 inch-lbs. The second number is the struc-ture rating in hundreds of pounds. In this case the structural rating is 256. This means that to avoid overloading the structure of the unit, polished rod load must not exceed 25,600 lbs. The last number shows the maximum stroke length of the unit in inches (100 inches in this case). Following is an explanation of the rest of the data needed for each unit type (refer to Figure 3.12):

Conventional and Enhanced Geometry Pumping Unit DataFor these units you must enter pumping unit di-mensions R, A, C, I, P, and K in inches, the struc-tural unbalance in pounds, and the crank offset angle in degrees. For enhanced geometry units the crank offset angle must be negative. Figure 3.12 shows the dimensions XROD needs.The API spec. 11E defines the above dimensions as follows:

Dimension: Description:R Radius of the crank (inches)A Distance from the centerline of the

saddle bearing to the centerline of the polished rod (inches)

C Distance from the centerline of the saddle bearing to the centerline of

the polished rod (inches)I Horizontal distance from the

centerline of the saddle bearing to the centerline of the crankshaft

(inches)

P Effective length of the pitman arm, in inches (from the center of the equalizer bearing to the center

of the crank-pin bearing) K Distance from the center of the

crankshaft to the center of the saddle bearing (inches). Some-times, instead of the K dimen-

sion, pumping unit manufacturers supply data for dimensions H and G instead (described below). From these dimensions and dimension I (defined above) you can calculate

K as follows: K= ( H-G ) + I2 2

H Height from the center of the saddle bearing to the bottom of

the base beams (inches)G Height from the center of the

crank shaft to the bottom of the base beams (inches)

Mark II Pumping Unit DataFor Mark II units you must also enter pumping unit dimensions R, A, C, I, P, and K in inches, the structural unbalance in pounds, and the crank offset angle in degrees. This angle is positive for Mark II units.The API spec. 11E defines the above dimensions as follows:

Dimension: Description:R Radius of the crank (inches)A Distance from the center of the

Sampson Post bearing to the cen-terline of the polished rod (inches)

C Distance from the centerline of the Sampson Post bearing to the cen-ter of the equalizer (or cross yoke)

bearing (inches)I Horizontal distance between the

centerline of the Sampson Post bearing and the centerline of the

crankshaft (inches)

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P Effective length of the pitman arm, in inches (from the center of the equalizer (or cross yoke) bear-ing to the center of the crank-pin

bearing)K Distance from the center of the

crankshaft to the center of the Sampson Post bearing (inches)

H Height from the center of the saddle bearing to the bottom of

the base beams (inches)G Height from the center of the

crank shaft to the bottom of the base beams (inches)

Air Balanced Pumping Unit DataFor these units you must also enter pumping unit dimensions R, A, C, I, P, and K in inches. In ad-dition, you need data for M, S and V0. The API spec. 11E defines the above dimensions as follows:

Dimension: Description:R Radius of the crank (inches)A Distance from the center of the

Sampson Post bearing to the cen-terline of the polished rod (inches)

C Distance from the centerline of the Sampson Post bearing to the center of the equalizer bearing

(inches)I Horizontal distance between the

centerline of the Sampson Post bearing and the centerline of the

crankshaft (inches)P Effective length of the pitman

arm, in inches (from the center of the equalizer bearing to the center

of the crank-pin bearing)K Distance from the center of the

crankshaft to the center of the Sampson Post bearing (inches).

M Geometry constant (in2). It is the distance from the Sampson Post bearing to air tank bearing (dis-tance X in Figure 2.3) multiplied by the area of the piston in the air cylinder divided by dimension A or: X*Ap/A, where Ap is the area of the air cylinder piston in square

inches.

Figure 4.20 - Dimensions for long stroke units

Figure 4.21 - Definition of structural unbalance

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S Pressure in the air counterbal-ance cylinder required to offset

the weight of the walking beam, horsehead, equalizer, pitman arms,

etc. (psig).V0 Minimum air volume between the

plunger and cylinder at the bottom of the stroke (in3).

Long Stroke Pumping Unit DataFor these units you must enter the sprocket diam-eter (D), the centerline distance between the top and bottom sprockets (distance C), the pitman arm length (P) if one exists (usually this is zero), and the top drum diameter ratio (usually equal to 1). You can see a diagram of the dimensional data you need by pressing F1 in any input field, or you can take a look at Figure 4.20.You can also use this pumping unit model to sim-ulate any non-beam pumping unit with a long, slow stroke. You can do this by entering data that will produce the same stroke length as the unit you want to model. The stroke length of a long stroke unit is given by:

Stroke = C + D For example, to simulate a hydraulic pumping unit with a stroke length of 200 inches, you can enter a sprocket diameter (D) of 20 inches and a centerline distance between sprockets equal to 180 inches. If you use this approach to design a system with a

hydraulic unit then the torque calculations, energy consumption, and other results that depend on torque will be incorrect or meaningless. However, the predicted polished rod dynamometer card, polished rod horsepower, stress analysis, etc. will be valid. This technique can be used as long as the upstroke and downstroke polished rod velocities of the hydraulic or long stroke unit you want to simulate are approximately equal. Tip: To predict energy consumption more ac-curately for hydraulic units using the long stroke pumping unit model, input a pitman arm length of zero and a drum diameter ratio of 2.Another thing to keep in mind is that even though the combination of C and D dimensions deter-mines the stroke length of long stroke units, the ratio of C/D determines the acceleration and de-celeration of the polished rod. For the long stroke geometry shown in Figure 4.20, when the connec-tion point between the belt and the chain touches the sprocket, the polished rod speed changes (accelerates or decelerates). When the connection point leaves the sprocket (C section in Figure 4.20) the speed is constant. Therefore, different com-binations of C and D dimensions may be needed to correctly simulate the polished rod motion of a hydraulic pumping unit.

Definition of Structural UnbalanceStructural unbalance is a term used for pumping units with walking beams. It is defined in API 11E as the force you need at the polished rod to hold the walking beam horizontal with the pitman arms disconnected from the crank pins. This force is positive when acting down and negative when acting up. See Figure 4.21 for a visual explanation of structural unbalance. Structural unbalance for conventional units can be either positive or nega-tive. For Mark II units it is always negative. If you do not know the structural unbalance for the unit you want to simulate then enter zero. In most cases the structural unbalance will not affect the results significantly (especially for Conventional geometry units).Figure 4.22 - Definition of crank offset angle

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Definition of Crank Offset AngleThe crank offset angle (or crank phase angle) is the angle between a line through the crank holes and a line through the counterweight arm. Figure 4.22 shows how the crank offset angle is defined. XROD expects a positive crank offset angle for Mark II units and a negative one for enhanced geometry units such as the Torqmaster, Lufkin Reverse Mark, or American Producer II. For conventional pumping units the crank offset angle is zero.

Entering Counterbalance InformationAfter you select a pumping unit or enter your own pumping unit data, the crank hole number, and direction of rotation, you must enter counterbal-ance information. Entering an existing maximum counterbalance moment allows you to simulate an existing system to find out if the unit is overloaded or out of bal-ance. If you only want to find the maximum coun-terbalance moment required to balance the unit (which is usually the case for new designs) then click on the “Unknown” check box and XROD will calculate it for you. For beam pumping units except for air balanced,

you can enter a maximum counterbalance mo-ment in thousand inch-lbs. XROD also gives you the option to import the maximum counterbal-ance moment from a CBALANCE / XBAL file or from the clipboard. If you ran CBALANCE or XBAL before running XROD, then the value of the existing maximum counterbalance moment will be in the clipboard. Then, as soon as you click on the Use CBALANCE/XBAL information button, XROD will allow you to use the value exported by CBALANCE or to read a CBAL-ANCE file from disk.For air balanced units you must enter the air cyl-inder pressure in psig at the bottom of the stroke. For long stroke units you must enter the counter-balance weight in thousands of pounds. For these units, the option to read a CBALANCE file is disabled since it does not apply.If you enter existing counterbalance data, XROD calculates and displays the permissible load dia-gram for existing conditions. Also, the recom-mended prime mover size and overall system efficiency will be for the existing conditions. If you select “unknown” for maximum counterbalance moment then XROD calculates all these numbers and the permissible load diagram for balanced con-ditions only.The range of allowable counterweight is different

Figure 4.23 - Entering motor information

48 | Running XROD

for different Rotaflex units. XROD takes this into account when validating your entry for counterbal-ance weight. For example, the minimum counter-weight possible for the 1200 model is 13,500 lbs. Therefore, if you try to enter a counterweight that is less than 13.5 M lbs, (M =thousands) XROD will warn you that the counterweight for this unit must be between 13.5 and 32.5 M lbs.

Changing Structural UnbalanceIn some cases, when the pumping unit is signifi-cantly oversized for the downhole equipment, you may have to add counterweights on the walking beam next to the horsehead to balance the unit. This changes the structural unbalance from the catalog value. XROD allows you to change the structural unbalance even when you select a pump-ing unit from the program’s database. The structural unbalance field can also be used to simulate beam balanced units. By changing the value of the structural unbalance, you can figure out how much weight you need to add or remove from the walking beam to balance a beam bal-anced unit.

4.3.6 Entering Motor Information and Energy CostXROD can simulate NEMA D or ultra high slip motors and calculates power consumption from actual motor efficiency curves. The program uses the electricity cost you enter to predict the monthly electricity bill, $/bbl fluid, and $/bbl oil (based on water cut). XROD defaults to the cost number you specify in Setup. The $ symbol here is meant to represent currency (not just US dollars). As Figure 4.23 shows, under the electricity cost input box there are option buttons that you can use to se-lect the power meter type. You have two options: Detent, or Non-detent. A Detent KWH meter can rotate only in one direction. A ratchet prevents it from turning the other way. Therefore, if your unit is generating electricity, you do not get credit for it. The non-detent meter can rotate either way and so it credits you for electricity the pumping unit generates.

Prime mover type selectionUsing drop-down list boxes you can select the mo-tor type you want to simulate. XROD has motor performance and efficiency data for NEMA D, Sargent Ultra High Slip, Reliance Ultra High Slip motors, and Rotaflex Multi-HP NEMA C mo-tors. If you select a NEMA D motor you can enter a motor size, or you can choose to have XROD recommend a NEMA D motor for you. If you select an ultra high slip motor then you must select the motor size and torque mode. If you select a motor size or mode that is too small for the well conditions then XROD will display a warning message and will give you the option to change your data. XROD warns you if you select an ultra-high-slip motor when you have selected an air-balanced or long stroke pumping unit. These units have little or no rotating moment of inertia, so using an ultra-high-slip motor does not result in any significant differences in the calculations. Therefore, for these units, do not select an ultra high slip motor or to include speed variation effects.If you select a NEMA D motor type for a new case, or switch from an ultra-high-slip motor to a NEMA D motor, XROD automatically selects the option to recommend the motor size.

Motor speed variationThe option to include the effect of motor speed variation is only available for conventional, en-hanced geometry, and Mark II units. Inertia ef-fects are negligible for long stroke and air balanced units.If you select not to include speed variation effects then XROD assumes constant prime mover speed and will not model the effect of pumping unit in-ertia. If you choose to include speed variation then XROD gives you the option to enter a percent speed variation or have the program calculate the speed variation for your prime mover.

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Pumping unit moments of inertiaIf you select to include the effect of motor speed variation then you can enter a rotating moment of inertia in lbs-ft2, or have the program estimate this number for you. For the articulating moment of inertia XROD defaults to a number that is either the actual articulating moment of inertia supplied by the pumping unit manufacturer, or an estimate based on unit size. Therefore, unless you have an even more accurate number for the articulating moment of inertia, it is recommended that you use the default number displayed by the program. For more accurate results, have XROD calculate the prime mover speed variation. However, you can also enter a speed variation value if desired. If you select to enter speed variation, XROD shows a default value of 8% which corresponds to a rec-ommended average speed variation for NEMA D motors. You can get more conservative results by entering a speed variation that is less than the maximum expected speed variation for your prime mover. Selecting to include prime mover speed variation will approximately double XROD’s run time.What is moment of inertia?Although this manual is not intended to teach engineering or physics, it is important to briefly explain moment of inertia and how it can affect XROD’s results. The mass moment of inertia of a body is a measure of its resistance to acceleration. In other words, the higher the moment of inertia of a body, the more difficult it is to quickly speed it up or slow it down.The rotating and articulating moments of inertia are important in accurately simulating the behavior or the pumping unit and in calculating net gearbox torque when you use a high speed variation prime mover. The rotating moment of inertia that XROD needs is the total rotating moment of inertia. This includes the individual rotating moments of inertia of the cranks and counterweights about the slow speed shaft of the pumping unit, the total gear reducer inertia, and the motor rotor inertia. The articulating moment of inertia of the pumping unit

around the saddle bearing includes the inertia of the walking beam, horsehead, and pitman arms.As mentioned above, you can either enter a rotat-ing moment of inertia, or you can have XROD estimate it for you. To calculate accurately the rotating moment of inertia you must have moment of inertia data for the cranks and counterweights, gearbox, motor rotor, etc. Also, the rotating mo-ment of inertia depends on the position of the counterweights on the cranks. Since this data may not be known, it is recommended that you let XROD estimate the rotating moment of inertia for you.Since the articulating moment of inertia depends on the walking beam size, horsehead and pitman arms, it is a fixed number for any given pumping unit. Therefore, it is easier to calculate than the rotating moment of inertia. XROD’s pumping unit data base contains accurate articulating moment of inertia values that were either obtained from unit manufacturers, or were estimated based on unit size. The articulating moment of inertia from the pumping unit database appears as the default number when the program prompts you for the articulating moment of inertia.Including speed variation and moments of inertia will usually result in lower predicted peak gearbox torque, lower peak polished rod load, and higher minimum polished rod load. This is because a high speed variation prime mover slows down as the torque on it increases. The rotational inertia of cranks and counterweights causes a release of ener-gy that lowers the torque the gearbox must supply. The articulating inertia adds torque to the gearbox since it opposes the acceleration of the walking beam and horsehead. However, the effect of the articulating moment of inertia is usually small compared to the effect of the rotating moment of inertia. When the prime mover slows down in response to high torque, it causes the polished rod to slow down as well. This results in lower dynamic forces and therefore lower peak polished rod load.

XROD | 51

5 Changing, Loading and Saving Data

5.1 Visual InputFigure 5.1 shows XROD’s “visual” input facility that makes it easy to locate a system parameter you want to change. As you are entering the data for a new case, or after you have loaded a case from disk, the visual input window can be displayed by clicking on the Visual Input button on the toolbar. This shows an interactive picture of the pump-ing system. This feature is useful when running in non-AI Mode since the AI mode has only two input windows.As you move your mouse over the picture of the system, tool tips appear naming various parts of the system. Whenever a tool tip is showing, you can right-click with the mouse to get a pop-up menu listing input variables associated with that part of the system. This visual way of changing data is more useful when you are changing data in existing files or when you are making “what if...” runs. If you are entering a case from scratch, menu items that correspond to data you haven’t yet entered will be disabled.Left-clicking when a tool tip is displayed opens the data entry window associated with the part of the system you clicked on. Another way to change data is to click on the “Alphabetical list…” button at the bottom of the visual input window. This brings ups an alphabetical listing of all variables you can change. You can locate the variable you want to change by scrolling down using the mouse.

5.2 Storing Data FilesAfter you finish entering data for a system, you can save the data to disk by clicking on the Quick

Save button on the toolbar (third from left with diskette icon), or by selecting File from the menu bar and then choosing Save As... This brings up a standard Windows dialog box that allows you to save your file with the file name you want. XROD shows the default file name it creates from the well name and by adding an “.RSVX” file name exten-

Figure 5.1 - XROD’s Visual Input window

52 | Changing, Loading and Saving Data

sion for RODSTAR or “.XRVX” for XROD. You can change the file name by typing over it, but you cannot change the file name extension. When you type your own file name, you do not have to type the file name extension. XROD automatically adds this extension for you. You do not have to store your data every time you make a change. It is recommended that you save the original data and then wait until you get a good design before storing data to disk. After saving data once, XROD makes it very easy to update the file with the data in memory with a single mouse click on the Quick Save button on the toolbar.If you save your data after running XROD and the output is displayed on screen, then the non-AI mode saves both the input and output in the file. This is advantageous because once you save the output then you can view and print the output without having to rerun the case. XROD AI mode

allows you to save the output as well but as indi-vidual files. On the batch log window click Save All Cases and all of the cases from the run will be saved individually with their output.

5.3 Running and Viewing the OutputAfter you enter all your data and you press the Next Screen button from the motor information window, the Run button on the toolbar becomes active. To run the program simply click on the Run button on the toolbar (the dynamometer card icon to the right of the right arrow icon). Another way to run the program is to click on Run on the menu bar. After XROD runs, it displays the out-put report, as Figure 5.2 shows. At the bottom of this screen there are buttons that allow you to view the dynamometer, torque, or IPR plots and the report. When you select to see the dynamometer

Figure 5.2 - Summary output report - upper half

XROD | 53

plots, you can select to animate the surface and downhole pump cards.When running XROD, these output reports can be opened by double-clicking the file directory in the batch log, see Figure 5.4. These reports will display all the specific parameters of the systems that XROD designed for your well.To look at different parts of the output you can click the appropriate buttons at the bottom of the screen (Dynamometer, Torque, IPR Plot, or Report). When you click on Report, you can scroll up or down with the mouse, or you can click and drag on the report itself. Figure 5.3 shows the bot-tom section of the summary report. The summary report looks exactly the same as the printed report.To return to the batch log simply click the close button on the bottom right corner of the Output

Results window. Any action to close this window without using this button will close the batch log and you will not be able to return to the batch log. If you wish to make adjustments in a specific sys-tem but do not want to lose the cases in the batch log, you may save all cases with the Save All Cases button on the top right of the batch log window. These cases will be saved by default to your “C:\THETA\SavedXROD_Runs” folder. XROD will also create an Excel spreadsheet with all the cases listed in order for you to make a side by side comparison of the cases. This spreadsheet will automatically open once the run is completed. You may edit these spreadsheets to any format you would like by using the Batch Mode setup options. Refer to Chapter 3.If you have XBAL on your computer, you can have XROD export the balanced maximum counterbal-

Figure 5.3 - Summary output report - lower half


ance moment it calculates to CBALANCE. You can do this any time the calculations have been run (whether or not you are actually viewing them) by clicking on the Export CBM button on the

toolbar ( ). XROD can calculate two possible ways to bal-ance a unit: for minimum torque, or for minimum energy consumption.The most common way to balance a unit is for minimum torque. However, if the gearbox is not overloaded, you may want to balance the unit for minimum energy consumption instead. After viewing the output you can decide which value of balanced counterbalance moment you want to export to CBALANCE (so that CBAL-ANCE can calculate the counterweight positions required to balance the unit). When you click on

the Export CBM... button RODSTAR displays the window shown in Figure 5.6 (if there are two possible ways to balance the unit). Click on the option you want and click on the OK button. RODSTAR confirms that the value of the maxi-mum counterbalance moment has been exported by displaying the message box shown in Figure 5.7.

5.3.1 Saving the outputIf you save the file while the output is being dis-played on the screen, in non-AI mode, XROD saves the output along with the input in the same file. Then, you can load a file with output and you can display and print the output without having to rerun the program. To save the output, click on the quick save icon on the tool bar, or select File on the menu bar and then select Save As..

Figure 5.4 - XROD’s AI Mode Batch Log

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When you load a file that has output saved, the program will tell you that output results are avail-able on the status bar (at the bottom of the XROD window).With XROD, you may save all cases with the Save All Cases button on the top right of the batch log window. These cases will be saved by default to your “C:\THETA\SavedXROD_Runs” folder. These files will be saved as RSVX files.If you save the XROD file (XRVX) it will only be the settings and input parameters and you must run the file to obtain the output results.

5.3.2 Running in Batch ModeXROD runs batches as a default but you may run more than one case at a time using the non-AI mode by selecting to run two or more files in batch mode. The batch mode starts automatically when you select to load more than one file. This capabil-

Figure 5.5 - XROD’s Output Results

Figure 5.6 - Exporting the maximum CB moment


ity allows you to make an unlimited number of XROD runs automatically, and without you hav-ing to be at the computer. XROD even allows you to schedule the batch run to start at any time (from the Setup window). To start the batch, select to open a file (either by clicking the Open File toolbar button, or by select-ing Open… from the File menu). This brings up the open file dialog box. To select a group of files

to run in batch, click on the first file and then, while pressing S, click on the last file in the list. Or, you can click on the first file and then drag the mouse to highlight all the files you want to run (it must be a continuous group). To select individual files, click on the files you want to select while pressing C. The selected files are high-lighted as Figure 5.8 shows. When you are done

selecting files, click OK.At this point, XROD will display the option box in Figure 5.9 asking you to choose the options you want for the batch run. The first option causes XROD to create printouts for all the files it runs. This option is unselected by default. The second option causes XROD to create a sum-mary spreadsheet file for all the cases it runs. The option to view the spread-sheet in Excel means that once the cases are pro-cessed and the spreadsheet is created, XROD will au-tomatically load Excel and display the results for you.Figure 5.8 - Selecting files for a batch run

Figure 5.7 - Maximum CB moment exported

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The last option allows you to specify whether you want XROD to rerun cases with saved output or not. If you do not select the option “View spreadsheet in Excel” when you click on “Proceed”, XROD asks you for Excel file name as shown in Figure 5.10. Otherwise, if you select to view spreadsheet in Excel, XROD starts running in batch immedi-ately.Creating a summary spreadsheet is very useful because it allows you to summarize many runs in a very concise way. After the results are in a spread-sheet file, you can plot one variable versus another, you can sort the spreadsheet columns by rod string

cost, system efficiency, energy cost per barrel of oil, etc. There is no limit to what you can do with the results.The spreadsheets that XROD create summarize the results of all the runs and loads it directly into Excel. Under the Setup window you can “design” and save an unlimited number of spreadsheet formats. If you do not specify a spreadsheet format before running many cases in batch mode, XROD uses the default spreadsheet format that comes with XROD and contains the most common sys-tem design comparison variables.The option “Don’t re-run cases with saved out-put” allows you to create different summary spreadsheet files with the same set of XROD files. When you select this option XROD runs very fast in batch because all it has to do is extract the cal-culated values that have already been saved in the XROD files and enter them in the spreadsheet. When XROD starts to run the files you selected, it displays a batch run log window such as that shown in Figure 5.11 that shows the number of files you selected, the number of runs that have been completed so far, and the overall percent

completion. XROD shows the name of each file that it runs. XROD prints warnings or errors after the name line while running each case. After each new run is complete, the program prints “** Run Complete **”.This is a useful record of the cases that XROD ran and any warning or errors generated while running them. You can cancel a batch run at any time by clicking on “Cancel”. The program will stop after it finishes running the current case and it will display a message box

Figure 5.9 - Batch run options

Figure 5.10 - Selecting a spreadsheet file to create


that says: “The batch run was canceled.”After the batch run is done, click OK to close this information box. Then, click on the print icon on the tool bar. We recommend printing the batch run log, especially when running many XROD cases. The batch run log shows what files you ran, and any errors or warnings for each case.Using the batch process can save you from hav-ing to wait for each case to run. You can have your case execute while at lunch or even overnight.

5.4 Loading Data from DiskAfter you enter data and store a file you can easily modify it by loading it back in memory. Also, you can load a file with saved output and view or print the output results without having to rerun a case (non-AI mode). You can do this by:- Clicking on the Open button on the toolbar (second from left).- Clicking on File on

Figure 5.11 - A batch run log

Figure 5.12 - Selecting a file to open

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the Menu bar and then on Open, or by pressing C+ o.Also, XROD keeps track of up to nine of the most recent files you saved or loaded and allows you to quickly load any of them. To see a list of these files click on the drop-down icon between the file open and file save icons on the tool bar and then click on the file you want to load. Or, you can click on File from the menu bar and select “Recent Files”If there is data in memory, XROD will warn you that loading new data will erase the existing data in memory. This alerts you and helps prevent ac-cidental loss of your data before you have a chance to save it.XROD has a powerful and easy-to-use file man-agement system. When you select to load data from disk, XROD displays the current path and a list of files in the current directory in alphabeti-cal order. Also, XROD allows you to read ROD-DIAG files, XDIAG files, and even older XROD files. XROD displays a list of the file type you selected in the current directory as the Figure 5.12 shows.To load one of these files, double click on it, or

Figure 5.13 - Minimized input windows

click on it once and then click on OK. If the file you want is not in the current directory, you can easily move to any directory on any drive in your system since this window also lists sub directories, and system drives.If your current directory contains many XROD files, it may be faster to press the first character of the file you are looking for. For example, if you are looking for well name “PR101.XRVX”, click in the list once, and then press p and the program will jump to the first file in the list that starts with “P.”

5.4.1 Viewing Previously Saved OutputWhen you load a RSVX file that contains output you can display the output without having to rerun the case. When you load a case that contains input data only (no output results were saved), XROD displays the first input window (well information). Also, the report and print icons on the toolbar are not available. However, when you load a file that contains both input and output, XROD does not open any input windows. The status bar at the bot-tom of the screen shows a message like the follow-ing:

“Successfully loaded file: C:\The-ta\XROD cases\special cases\abc#1.rsvx (output results are available).” Also, the report and print icons on the tool bar are active. To see the output without having to re-run the case, click on the report icon on the tool bar. To print the output, click on the printer icon (next to the e-mail icon).

5.5 Manipulating Input WindowsXROD is a standard Microsoft Windows application and it al-


lows you to manipulate the input windows several different ways. After entering data for all the input windows, or after you load a file from disk, you can display one window at a time, you can open all windows, or you can arrange them any way you want as explained below:

♦ After entering data for a case or after load-ing a file from disk, click on each window’s icon on the toolbar. This loads all input windows.

♦ You can click on the minimize button of each form to minimize them into icons at the bottom of the main window as Figure 5.11 shows. To open any of the minimized windows, double click on its icon or click on it once and then select Restore.

♦ You can use the mouse to resize windows, or to drag a window or an icon anywhere in the XROD main window.

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6 Rod Pump System Design

You can use XROD to quickly design any rod pumping system, compare pumping units, sucker rod designs, insert versus tubing pumps, clockwise versus counterclockwise crank rotation, include IPR modeling in your predictions, etc. XROD can calculate the pumping speed, pump plunger size, and rod string design for you. Also, it can recom-mend motor size and pumping unit size based on your target production. These powerful features help you design rod pumping systems faster than ever before. Also, because XROD uses state-of-

the-art design algorithms, it is very accurate and reliable. The biggest advantage of XROD is that it lets you design rod pumping systems very fast using your AI mode preferences. You can then go into the individual design and fine tune it if neces-sary. This dramatically reduces the time it takes to design rod pumping systems. I also improves the designs since the AI capabilities of XROD result in excellent system designs with very high scores.Because XROD can predict energy consumption very accurately, you can use it to select the most

Figure 6.1 - XROD Summary Report

62 | Rod Pump System Design

economic system designs. The following sections explain how to apply XROD to solve common de-sign problems. As you become more familiar with XROD you will discover many different applica-tions for this powerful rod pump system design tool. XROD’s capability to read RODDIAG and XDIAG files (in non-AI mode) and overlay the measured dynamometer card on the same plot as the predicted one is very useful. With this capabil-ity you can:1. Perform a “History Match” on existing rod

pumping systems before you make a design change. This allows you to figure out unknown quantities such as rod-tubing friction.

2. Detect an out-of-calibration load cell (used to record the actual dynamometer card) by checking for a consistent shift in actual versus predicted dynamometer card shape.

3. Detect incorrect fluid level measurements due to foam in gassy wells.

6.1 Understanding XROD’s OutputTo maximize the benefit of using XROD, it is important to understand its output. After XROD runs in non-AI mode, it displays the summary output report page. Also, it shows buttons on the bottom of the output window that allows you to access the predicted dynamometer plot, torque plot, IPR plot (if IPR data was entered), or return to the output report as Figure 6.1 shows.

6.1.1 Dynamometer and Permissible Load PlotsWhen you click on the “Dynamometer” button then you see the predicted surface and downhole dynamometer card plots along with the permis-sible load diagram as shown in Figure 6.2 . These plots show the predicted surface and downhole dynamometer cards, measured surface dynamom-eter card from a RODDIAG or XDIAG file (if

Figure 6.2 - Dynamometer plots and Permissible Load diagram

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you selected that option), and the permissible load diagram. XROD uses a permissible load diagram that shows if the gearbox or structure of the pumping unit are overloaded or if the minimum polished rod load is negative. This is different than the traditional permissible load diagram that only shows whether the gearbox is overloaded. This extended permissible load diagram can be made up of curved lines only, combination of curved and straight lines, or straight lines only. If the upstroke part of the predicted surface dynamometer card exceeds the curved line of the permissible load diagram this indicates that the gearbox is over-loaded at that point. If the dynamometer card cuts into the straight line section of the permissible load diagram on the upstroke, this indicates that the structure of the pumping unit is overloaded because the polished rod load is larger than the structure rating of the unit.For the exact numbers of peak net gearbox torque and gearbox loading, look at the torque analy-

sis section of the printout. The permissible load diagram corresponds to existing conditions if you entered a counterbalance moment. If you did not enter an existing max. CB moment then the pro-gram shows a permissible load diagram for bal-anced condition (for minimizing gearbox torque).

Note!: The above discussion about XROD’s permissible load diagram refers to beam pump-ing units. The permissible load diagram for long stroke units such as the Rotaflex will have straight line segments that correspond to gear-box loading or structure loading. Please look at the structure loading number on the first page of the output and the percent gearbox loading under torque analysis for the exact percent unit loading.

In addition to showing whether the gearbox is overloaded, the permissible load diagram also shows how well the pumping unit matches the load requirements of your system. If the predicted polished rod dynamometer card fits nicely in the

Figure 6.3 - Torque plot


permissible load envelope, this indicates a good agreement between the pumping unit and the rest of the system.However, if the predicted surface dynamometer card shows a trend that is opposite that of the permissible load diagram, this shows that design changes are necessary to avoid overloading the pumping unit and to better match it to the rest of the system. If the permissible load has a trend that is opposite than the predicted dynamometer card, it may indicate that the pumping unit you se-lected is not the best geometry for this application. You may have to change the spm, plunger size, rod string design, or stroke length to get a better match between the dynamometer card and permis-

sible load diagram. Including prime mover speed variation and inertia effects will alter the shape of the permissible load diagram. The lines will be smoother if you do not include prime mover speed variation. If you include speed variation the permissible load diagram will tend to reflect changes in polished rod load. This is because the permissible load diagram in XROD includes the effect of rotating and articulating mo-ments of inertia. As the prime mover speed chang-es, this causes changes in polished rod velocity and acceleration which in turn changes the polished rod load and the distance between the dynamom-eter card and the permissible load diagram.

Figure 6.4 - Inflow performance relationship (IPR) plot

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6.1.3 IPR PlotWhen you click on the “IPR Plot” button, XROD displays separate oil, water, and fluid production versus flowing bottomhole pressure plots as Figure 6.4 shows. Also, it shows a line with the current bottom hole pressure and the test points you en-tered. The line below the title of the plot shows the correlation you selected to use for the oil IPR and if you selected the Fetkovich method, it shows the value of n. If you only enter one test point, n is set to one. If you enter two or more test points then XROD calculates the value of n by doing a log-log plot. For water, XROD uses a straight line IPR.

6.1.4 ReportTo see the report, click on the “Report” button. To open a report from the batch log simply click on the file name. You can scroll this window using the mouse by clicking or the up or down arrows at the top or bottom of the range bar on the right edge of the window.Or, you can click and drag the range bar or the report itself with the mouse.Cover PageIf this page is enabled, it will be the first page of the report. This page is designed to create a pre-sentable cover page when sending reports to other parties. You may put your company logo and con-tact information as well the recipients information clearly documenting who performed the run and who the run is addressed to.ScoringThis page will display the overall score of the design in a basic letter grade format. If there are any areas of concern which may have caused a low score, XROD will display the issues here and rec-ommend solutions to the problems. If the system receives a good score without recommendations, then the scoring page will not be displayed.

The output window has new buttons that allow you to animate the calculated dynamometer cards. Figure 6.2 shows a “play” button (the one with the double arrow) which causes small dots to move around the surface and downhole dynamometer cards; a “stop” button which makes the movement stop; and a “step” button (the one with the single arrow) which lets you move the dots one time-step at a time, while holding the button down moves the dots in slow motion. This facility can be used to get a better understanding of rod stretch effects and other phenomena such as the position and speed of the pump plunger and how this relates to the surface dynamometer card. From this screen you can look at any other part of the output by clicking the appropriate option at the bottom of the screen. For example, to view the torque plots click on Torque. Also, you can select to view the report on screen, or you can send the output to the printer. After you are done viewing the output, close the screen by clicking on Close.

6.1.2 Torque PlotWhen you click on the “Torque Plot” button XROD displays the net gearbox torque plots for existing and balanced conditions. If you entered an existing maximum counterbalance moment, then you may see a plot with up to three curves: one for existing conditions, one for balanced conditions for minimum torque, and one for minimum energy consumption. If there is no difference between the curve for minimum torque and the one for minimum energy, then the program shows only two curves (existing and balanced). If you selected “unknown” max. CB moment then XROD will only show one curve if there is little difference between balanced for min. torque vs balanced for minimum energy consumption (see Figure 6.3). Otherwise, it will show two balanced curves: one for minimizing torque and one for minimizing energy consumption.


Input and Output SummaryThe summary report that appears when you first run XROD shows input data on the left side of the page and calculated numbers on the right size. The top part of the printout shows the company name, well name, user name, date of the run, and com-ment. Following is a detailed explanation of each item on the output.

Polished Rod Loads and HorsepowerThe peak and minimum polished rod loads show the polished rod load fluctuation predicted by XROD. The polished rod horsepower shows how much work the pumping system is putting into the rod string to lift the predicted production from the present fluid level to the surface.If you entered a target production or used IPR data to determine the target production, XROD calcu-lates the SPM required to get the target produc-tion.

System EfficiencyThe system efficiency is calculated by regarding the whole pumping system as a black box with electricity going in and produced fluid coming out. This number shows how efficiently the system con-verts electric power to work needed to lift the pro-duced fluid to the surface. A system efficiency of 45% or above is excellent. In General, deeper wells will have lower efficiencies than shallow wells since deep wells have more rod-tubing frictional loses.Efficiencies of 35%-45% are average, while system efficiencies of less than 35% are poor and can usu-ally be increased by using a longer, slower stroke (with larger pump plunger).

Permissible Load HPPermissible load horsepower is defined as the area bounded by the upper permissible load line, lim-ited by the structural rating of the pumping unit and the lower permissible load line, limited by zero

minimum load.The ratio PLHP/PRHP (permissible load HP divided by polished rod HP) is a number that should be as large as possible without overloading the pumping unit. The larger this number is, the more of the pumping unit potential capacity you are using.

Fluid load on PumpFluid load on the pump shows how much fluid load the plunger is carrying on the upstroke. This is a function of pump depth, fluid level from sur-face, and plunger size. Fluid load on the pump is a function of pressure difference across the plunger and pump plunger diameter.

Unit Structural LoadingPumping unit Structural Loading indicates wheth-er or not the pumping unit structure is overloaded. This is a function of the peak polished rod load and the structural capacity of the pumping unit (the middle number in the API pumping unit designation).

Buoyant Rod WeightBuoyant rod weight shows how much the rod string weighs in fluid. Since the rod string is im-mersed in the fluid inside the tubing, it weighs less than in air. You can compare this number to a measured standing valve load. A good standing valve check should be close to the weight of rods in fluid as calculated by XROD for a pump that is in good mechanical condition. If these two numbers differ by more than 10% and the standing valve is in good condition, it may be an indication that the load cell is out of calibration or that the standing valve load was incorrectly measured. Also, the sum of the buoyant rod weight plus fluid load on the pump should be close to the traveling valve load for a good pump.

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N/No’ and Fo/SkrThe dimensionless numbers N/No’ and Fo/SKr are defined in API RP 11L1 . N/No’ is the ratio of pumping speed to natural frequency of the rod string. Fo/SKr is the rod stretch caused by the static application of fluid load, as a percent of the polished rod load stroke. In general, the higher the Fo/Skr is, the shorter the pump stroke will be. Also, the higher the N/No’ the larger the pump stroke is. These numbers also relate to system ef-ficiency. In general, the larger N/No’ is, the lower the efficiency will be. The larger the Fo/SKr is, the better the system efficiency is. However, this relationship is not linear.

For low Fo/Skr numbers (below 0.25) fiberglass-steel rod strings will have very low system efficien-cies and should be avoided. For fiberglass rods try

1 API RP 11L (Third Edition) Recommended Practice for Design Calculations for Sucker Rod Pumping Units. American Petroleum Institute, Dallas TX.

to keep Fo/Skr above 0.3 and below .8 for best results. Also for fiberglass rod strings, you should keep N/No’ below 1.0 and above .4 for best results.

Prime Mover Speed VariationIf you select to have XROD calculate the motor speed variation for you then this section shows what this number is. For NEMA D motors this number will vary from 2% to 14% depending on motor size. For correctly sized ultra high slip mo-tors it can be as high as 50%. If motor speed varia-tion is not considered then this will be indicated on the output report.

Pumping Unit DataThis section (see Figure 6.5) shows the pumping unit you selected, the pumping unit ID, the cal-culated stroke length, the structural unbalance, the crank offset angle, crank rotation with the well to the right, and the crank hole number. If

Figure 6.5 - Section of XROD Output Report


you entered your own pumping unit dimensions for a unit not in the program’s database, if the calculated stroke length is different from what you think it should be, check the pumping unit data to make sure you entered the right dimensions. If you selected to include speed variation and inertia ef-fects in the calculations, XROD will also print the rotating and articulating moments of inertia.

Torque Analysis and Electricity ConsumptionIn this section, the program prints the predicted peak gearbox torque, percent gearbox loading, cy-clic load factor, maximum counterbalance moment, and counterbalance effect. Also, it calculates elec-tricity consumption. XROD predicts the KWH consumed per day, the estimated monthly bill, and cost per barrel of fluid and per barrel of oil per day. Use the cost per barrel numbers when comparing system performance to ensure a valid comparison. This is because a system that shows a lower month-ly bill may also be producing less fluid. If you enter a non-zero maximum counterbalance moment the program calculates the above num-bers for both existing and balanced conditions. If the existing max. CB is unknown, it will calculate the above numbers for balanced conditions only. XROD has the capability to balance pumping units for minimum torque and minimum energy. If the maximum counterbalance moment for mini-mum energy equals the one for minimum torque then the program shows only one recommendation for balanced conditions. However, if the two values are more than 2% different then it shows two bal-anced columns: One for minimum torque, and one for minimum energy. The torque plots show how net gearbox torque changes throughout the pump-ing cycle for existing and balanced conditions.To maximize gearbox life you must keep gearbox loading less than 100%. The cyclic load factor indicates how smooth the gearbox torque is. The smaller this number is, the more uniform the net gearbox torque is. Also, a smaller cyclic load factor will result in higher system efficiency because of less thermal losses in the motor.

Tubing, and Pump InformationHere you see the tubing inside and outside di-ameters, the anchor depth, the calculated tubing stretch, the upstroke and downstroke rod-tubing friction factors you entered or that were calculated by XROD, pump load adjustment., etc. Also, this section shows the pump depth, the pump type, and plunger size. XROD uses the pump volumetric efficiency you enter to calculate the expected production rate. When you ask the program to calculate the spm by entering a target production, it will calculate a larger spm if you enter 80% pump efficiency than when you enter 90% pump efficiency.

Tubing, Pump and Plunger CalculationsThis section shows tubing stretch and production loss due to tubing stretch, gross pump stroke, the pump spacing recommendation, minimum re-quired pump length, and recommended plunger length. The pump spacing recommendation should be used as follows:

After working on the well and before you are ready to restart the pumping unit, make sure the tubing is full of fluid. Then lower the rod string slowly until it tags bottom. Then raise the rod string a distance equal to the one recommended by XROD next to: “Pump spacing (in. from bottom): ” Then, attach the polished rod to the bridle with the unit stopped at the very bottom of the down-stroke.

Please note that the working fluid level makes a big difference in pump spacing and pump length. This is especially true for fiberglass rods since the plunger travel is strongly dependent on fluid load on the plunger.

Rod String Design and Stress AnalysisThis section shows the rod string design and ser-vice factor you selected, the calculated percent rod

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loading for each rod section, the maximum and minimum stresses at the top, and the bottom min-imum stress for each rod section. To ensure your rods are in tension, do not include buoyancy effects (this should always be the case for steel rods). Then, make sure there are no negative stresses on any other rod section other than the sinker bar sec-tion on the bottom of the rod string.If you are using fiberglass rods you would not want to use a design with a negative bottom minimum stress on the fiberglass section even with buoyancy effects included. Compressive loading will cause fiberglass rods to part. Also, to maximize rod life, stress loading must be less than 100% in all cases. For sinker bars, XROD calculates stress loading, top maximum and top minimum stresses based on the elevator neck or pin undercut diameter of the sinker bars. However, XROD still uses the full body diameter in the calculation of stress at the bottom of the sinker bar section.

Rod String and Pumping Unit Cost AnalysisThis section shows the cost of each rod section as well as the total rod string cost (see Figure 6.6).

Also, below the rod string cost is the pumping unit cost. XROD shows the cost information only if you select this option in Setup. You must first enter rod string and pumping unit cost data in Setup before XROD can show you accurate cost infor-mation here.

Inflow Performance Relationship InformationThis section shows the correlation used for oil IPR, mid-perf depth, the static bottomhole pres-sure, and the bubble point pressure (if entered) or whether the well is producing below the bubble point pressure. Also, it shows a table of input test point data of flowing bottomhole pressure versus measured production, and a table of pressure vs. production table. As Figure 6.7 shows, this table shows separate oil, water, and fluid production rates for different pump intake pressures.

6.2 Rod Pump System Design GuidelinesThe following discussion applies to XROD’s non-AI mode. When designing a rod pumping

Figure 6.6 - System cost analysis


system you must specify the equipment, strokes per minute, and stroke length required to get the desired production at the lowest possible cost. In your efforts to select the best system design for your well you will be mostly concerned with the following parameters:

♦ Production Rate ♦ Capital costs ♦ Rod loading ♦ Gearbox loading ♦ System efficiency and power costs

Ideally, the system you select will give the highest present value profit after tax, considering capital and operating costs. Up to now, rod system design was a tedious trial and error process that usu-ally resulted in a system that could be far from ideal. Since achieving an optimum design requires equipment and data that may not be available, only the most obvious system parameters are usually considered. In most cases production rate is of highest priority, followed by rod loading, gear-box loading, and energy cost. If electricity cost is high, you can lower it by using a larger pump and a slower pumping speed. However, a large pump will increase rod loading and gearbox torque. Also, a large pumping unit must be used. This will increase capital cost. On the other hand, a small pump demands a faster pumping speed and longer stroke to maintain production. This increases ener-gy consumption but reduces the required pumping unit size. Usually, you must reach a compromise

between efficiency, rod loading, pumping unit size, and cost. A very important aspect of system design is pump-ing rate. If you know the maximum production rate you can expect then design the pumping sys-tem for a production rate a little higher than that. This ensures enough pump capacity to account for normal pump wear and inaccurate data. However, if the pumping rate is substantially higher than what the well is capable of producing, then the well will pump off. Fluid pound is a problem that results from the common practice of over-design-ing the pumping capacity. Fluid pound is damag-ing to pump, rods and pumping unit. If you do not take steps to minimize fluid pound it will reduce efficiency and equipment life. You can reduce fluid pound by slowing down the unit, shortening the stroke length, using a smaller pump, or by install-ing a percentage timer or pump off controller. Because XROD can simulate fluid pound, you can use it to see what will happen if the well pumps off.

6.2.1 Shallow, High Rate Well SimulationXROD can simulate any pumping unit geometry and gives accurate results for any pump depth or production rate. This is especially significant for shallow well applications because conventional design computer programs such as the API RP 11L and other wave equation programs give poor results. This is because at shallow depths, polished

Figure 6.7 - IPR report

XROD | 71

rod load is increasingly dependent on the dynamic effects of fluid in the tubing. This is especially true for high production rate shallow wells (pump depth less than 4000 feet with larger than 2.00” plunger). To accurately simulate these wells, XROD uses two wave equation models simultaneously, one for the rod string and one for the fluid in the tubing. This unique capability allows very accurate predictions. XROD can predict the expected surface and downhole dynamometer card shapes common to shallow, high rate wells. When designing shallow high rate wells it is recommended that you use pump ef-ficiencies of 90%-95% to avoid under-predicting peak polished rod load, torque, etc. This higher pump efficiency will result in higher fluid velocity in the tubing and higher fluid inertia forces on the plunger. However, when you are trying to “history match” an existing system, you may need to use a pump efficiency of less than 90% to better match the actual pump slippage of your system.

6.2.2 Selecting the Target ProductionTo avoid severely over-sizing the displacement capacity of your pumping system, design it with a pump efficiency of 80%-85% or even 75% if you expect the downhole pump to wear out quickly. This ensures that you will get your production without grossly over-designing the system.To minimize energy consumption and stress load-ing, use the largest plunger diameter and slow-est pumping speed combination possible without overloading the rod string and pumping unit. If you have to make a choice between stress loading and power consumption, opt for lower stress load-ing especially if you are close to 100% since rod breaks are more costly than a slightly lower system efficiency. Note that these are only general guidelines. Eco-nomics and local field conditions may require a different design philosophy than the one described above. Regardless of your objectives and design philosophy, with XROD you can design rod

pumping systems faster and more accurately than with any other computer program.

6.2.3 Avoiding Rod CompressionXROD calculates rod stresses at the top and bot-tom of each rod section. It calculates the maximum and minimum stress at the top of each rod section in order to calculate the percent stress loading. It also calculates the minimum stress at the bottom of each rod section. The bottom minimum stress shows if the rods are in compression.Steel rods can tolerate some compressive force but fiberglass rods cannot tolerate any compression at all. This is why fiberglass rods must have steel rods or sinker bars at the bottom. The weight of the sinker bars overcomes the opposing hydrostatic force and pump friction. If correctly designed, the sinker bars or steel rods ensure that the fiberglass rods are always in tension.Although steel rods can be subjected to some com-pression without adverse effects, excessive negative stresses can cause buckling problems. The recom-mended way to use XROD to determine how many sinker bars you need to avoid compres-sion is to select to have the program design the sinker bars for you in the AI Mode Preferences in Setup. Other ways of minimizing buckling prob-lems include using smaller pumping speeds and avoiding use of small diameter rods such as 5/8” or even ¾”.Please note that XROD can design the sinker bars you need to keep the rods in tension and avoid buckling even in non-AI mode.

6.2.4 Minimizing Power ConsumptionIn general, the slower the pumping speed and the larger the pump plunger size, the less energy the pumping system will use. However, minimizing energy consumption must not be the sole purpose of system design because a large pump plunger diameter will result in large polished rod load and


gearbox torque. This will require the purchase of a larger unit, larger rods and bigger prime mover. To come up with the best pumping system design you must consider the economics of the whole system and whether you plan to use existing equipment or buy new ones. XROD’s power and ease of use allows you to get the most economic pumping system based on your economic criteria. Because XROD calculates the predicted energy consumption, rod sizes, rod loading, and recommends a pumping unit size, it provides you with the data you need for sound economic decisions.

6.2.5 Reducing Gearbox TorqueSometimes, using the largest unit stroke may not be the best way to maximize production since it can result in severe gearbox overload. If this oc-curs you may be able to use the next smaller unit stroke and speed up the unit to get your produc-tion without overloading the gearbox. Another way of reducing gearbox loading is by using a smaller pump plunger. Another way is to use a lighter rod string by using either high strength steel or fiber-glass rods. Also, you can reduce gearbox torque with an ultra high slip motor. XROD can predict the gearbox torque depending on the pumping unit size and ul-tra high slip motor size. Also, XROD can calculate the motor speed variation and power consumption very accurately.

6.2.6 Using XROD for Correct Equipment SizingWhen designing a new rod pump system you must ensure that the system you select has sufficient ca-pacity to produce the well under the heaviest loads possible during its operating life. For most systems this will occur when the fluid level is at the pump. Therefore, even if you do not expect the fluid level to be at the pump, it is a good idea to design the pumping system (especially when using steel rods) for fluid level at the pump. This ensures that the

equipment you plan to use will not be overloaded if the fluid level drops in the future.For systems with fiberglass-steel rod strings, you may get higher gearbox torque loads and higher polished rod horsepower when the fluid level is above the pump. This occurs because fiberglass rods are very sensitive to fluid load. When the fluid level is above the pump, the fluid load on the pump is reduced. This causes a longer pump stroke which in turn affects the shape of the surface dynamome-ter card making it fatter. This in many cases brings the predicted surface dynamometer card closer to the permissible load diagram causing the gearbox load to increase. Also, when the area of the surface dynamometer card increases, the system requires a larger motor size. This means that when you use fiberglass rods you should run system simulations using different fluid levels (within the expected fluid level range) to see which fluid level results in the highest loads and largest required motor size. Using different fluid levels also affects the calculat-ed pump stroke length and therefore the required pump length and pump spacing . XROD can recommend a NEMA D motor size based on the fluid level or pump intake pressure you enter.TIP: You can speed up your system design con-siderably by asking XROD to design a rod string for you. Even if you do not plan to use the design XROD recommends, it is easy to “grab” XROD’s recommended design and modify it. To do this, after the program runs, go to the rod string entry screen and select the “Manual rod string entry” option. The program will default to the rod string it calculated, and it will display this data as if you had entered it yourself. So, you can simply change only the data you want to modify. Please keep in mind that XROD expects the length of the rod string you enter to be within 50 feet of the pump depth. However, it cannot be longer than the pump depth.

6.2.7 Using XROD for Diagnostic AnalysisAlthough XROD is primarily a design tool it can

XROD | 73

be a very powerful diagnostic aid, when used in conjunction with RODDIAG or XDIAG. This is due to the powerful overlay feature that allows direct comparison of predicted versus measured dynamometer cards.

Using XROD’s Dynamometer Overlay FeatureThis feature has many different uses. For example, it can help you figure out if your load cell is out of calibration, if the fluid level you measured was incorrect, etc. XROD can help you find these problems by comparing the shape and load range of the measured dynamometer card versus the one predicted by the program. Also, it can help verify downhole problems such as a worn pump, leaking traveling or standing valves, deep rod parts, stuck pump etc. You can simulate a worn out pump or a deep rod part by entering a fluid level of zero feet from surface. This will result in zero fluid load on the pump plunger. XROD cannot simulate a traveling valve leak, a hole in the pump barrel, or a sticking pump. But, it can predict what the dynamometer card should look like if there were no problems. Then, by comparing the actual dynamometer card shape with the theoretical shape, you can have more confidence in your diagnosis of the problem. For example, if you have a traveling or standing valve leak or a worn out pump, then the pump will be doing less work and the surface dynamometer card will have less area than the theoretical polished rod dynamometer card. If the pump is sticking, or if there is more friction than normal between rods and tubing (due to par-affin, scale, etc.), the measured dynamometer card will be fatter than normal. The theoretical polished rod dynamometer card predicted by XROD (for average friction calculated by the program) will be smaller than the measured dynamometer card. By entering a larger rod-tubing friction coefficient you can get a better match between actual and predict-ed dynamometer cards. This technique helps you figure out what rod-tubing friction factor to use for better simulation of your rod pumping wells.

Rod-tubing friction is especially important for fiberglass rods. Higher friction than normal may actually reduce the area of the predicted surface dynamometer card because it causes the rods to stretch which results in a small stroke at the pump.

Theta Oilfield Services, Inc., 3075 E. Imperial Hwy Suite 125, Brea, CA 92821 USA Phone: (562) 694-3297 | gotheta.com

http://www.gotheta.com

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