cerberus for coiled tubing achilles tutorial tutorial 1 introduction welcome to the cerberus for...

Cerberus for Coiled Tubing Workbook

Cerberus for Coiled Tubing Achilles Tutorial

Worked Examples for Fatigue Modeling

Example pages from the Achilles study guide to illustrate the tutorial style.

Copyright © 2007 Aradia Consulting All rights reserved. This publication may not be reproduced without the written

permission of Aradia Consulting. Rev A2 January 2007

Copyright © 2006 Aradia Consulting

Achilles Tutorial

Contents 1 Introduction.........................................................................................................1 2 Getting Started....................................................................................................3 2.1 Installing Cerberus for Coiled Tubing .........................................................3 2.2 Starting Cerberus for Coiled Tubing ...........................................................3 2.3 Selecting units..............................................................................................5 3 Worked Example 1 .............................................................................................6 3.1 Scenario description......................................................................................6 3.2 Sourcing input data .......................................................................................6 3.3 Preliminary discussion ..................................................................................8 3.4 Entering the input data ..................................................................................10 4 String Manager ..................................................................................................11 4.1 Overview.....................................................................................................11 4.2 Starting String Manager..............................................................................12 4.3 String Configuration Wizard.......................................................................14 4.4 String properties..........................................................................................19 4.4.1 Sections ...........................................................................................19 4.4.2 Welds ..............................................................................................22 4.4.3 Zones...............................................................................................25 4.4.4 Locking and Archiving ...................................................................26 4.5 Fatigue profile...............................................................................................28 4.6 String history.................................................................................................33 4.7 Utilities..........................................................................................................35 4.8 Modifying the string .....................................................................................36 4.8.1 Cutting out pipe...............................................................................36 4.8.2 Splicing in pipe ...............................................................................38 4.8.3 Reversing the string ........................................................................40 5 Reel Manager ......................................................................................................41 5.1 Overview.......................................................................................................41 5.2 Starting Reel Manager ..................................................................................41 5.3 Creating a new reel .......................................................................................42 5.4 Other properties and features ........................................................................43



6 Job Manager..................................................................................................44 6.1 Overview.................................................................................................44 6.2 Starting Job Manager ..............................................................................45 6.3 Job Design Wizard..................................................................................46 6.4 Job Log (depth and pressure data) .........................................................51 6.4.1 Getting started................................................................................57 6.4.2 Adding a row..................................................................................57 6.4.3 Inserting a row ...............................................................................59 6.4.4 Deleting a row................................................................................59 6.4.5 Copy and pasting rows...................................................................60 6.4.6 Other job log features.....................................................................61 6.5 Navigating Job Manager .........................................................................62 6.6 Locking and Archiving ...........................................................................64 6.7 Preparing to run the fatigue calculations ................................................66 7 Reel-Trak.......................................................................................................66 7.1 Overview.................................................................................................66 7.2 Starting Reel-Trak...................................................................................66 7.3 Loading a job ..........................................................................................68 7.4 Running a job..........................................................................................69 7.4.1 Job Log...........................................................................................71 7.4.2 String Viewer .................................................................................72 7.5 Saving the results ....................................................................................73 7.6 Reviewing the results..............................................................................74 7.7 Summary .................................................................................................75 8 Worked Example 2 .......................................................................................76 8.1 Scenario description................................................................................76 8.2 Sourcing input data .................................................................................76 8.3 Preliminary discussion ............................................................................76 9 Job Manager (using Orion data) ................................................................77 9.1 Job Wizard ..............................................................................................78 9.2 Job Log (Orion data)..............................................................................81 10 Reel-Trak.....................................................................................................8


Achilles Tutorial

1 Introduction Welcome to the Cerberus for Coiled Tubing Achilles tutorial!

This study guide, along with the online version at http://www.cerberustutorials.com, introduces users to the Achilles (fatigue life) module of the Cerberus for Coiled Tubing modeling software suite. The objective is to bring new or inexperienced users to a minimum level of competency, ideally prior to attending a training class in person. In this manner, students enter the classroom already familiar with navigating the software and some of the basic concepts behind the modeling, allowing more advanced topics to be addressed more quickly. The material is sufficiently detailed, however, that individuals wishing to teach themselves Achilles should be able to perform their own fatigue calculations even without the benefit of a subsequent class.

Achilles is one of the three main modules in the Cerberus for Coiled Tubing software suite. It allows you to track the fatigue life of a CT string, in order to avoid costly failures at the wellsite and yet maximize the usage of the pipe before it is retired from service.

CT fatigue is the invisible and irreversible phenomenon that occurs in the steel when the pipe is repeatedly strained beyond its plastic limit. This happens every time the CT is spooled off the drum and over the gooseneck (guide arch) into the well, and again as it is spooled back onto the drum. This repeated bending and straightening can only happen a limited number of times before fatigue cracks form in the steel and propagate through the tubing wall. As soon as even one crack opens communication between the inside and outside of the pipe (i.e. a leak), the CT is compromised and has to be withdrawn from service. In severe cases the pipe may even part, with potentially catastrophic consequences.

In most field locations, the CT has to be taken out of service before the first leak occurs, however minor, because a loss of pipe integrity can pose an unacceptable risk to personnel and the operation. Since the fatigue crack usually cannot be seen or detected before it fails, and cumulative fatigue damage cannot be measured with current technology, some other methodology must be used to decide when to stop using the CT. One such method is to use modeling software like Achilles to predict when the CT fatigue life has been exhausted based on its previous usage.

The fatigue life of a length of pipe is often expressed as the number of times it can be bent and straightened under the same conditions before the model predicts that it will fail. However, the fatigue life of CT string can vary greatly from one part of the string to another, and indeed between points just a few feet apart, depending on how many times each segment is bent, to what radius, and with what pressure on the inside. The modeling software therefore has to track the fatigue life of the pipe on a point-by-point basis along the entire length of the string. Each time that the pipe is moved in or out of the well, some portion of the tubing is bent and the new fatigue life for the affected section must be calculated and stored. This task is performed by calculation program Reel-Trak.

A CT string is said to have reached the end of its fatigue life when any part of the string reaches a predefined limit. (usually 80% of its theoretical life)


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If Achilles shows that the fatigue is concentrated in one zone of the pipe, as can easily happen if the CT is deployed in wells of similar depth or if it is used for drilling or fishing operations, it may be possible to cut out the high fatigue section, weld the two pieces back together and continue using the string, although this introduces a butt weld which is itself a concern.

Fatigue life modeling is now considered an essential part of coiled tubing operations. The ability to predict the safe working life of a CT string has revolutionized the coiled tubing industry by extending the economic life of tubing while allowing new applications like drilling and fracturing to be undertaken with confidence. Navigating the Tutorial

The purpose of this tutorial is to familiarize you with tracking CT fatigue in Cerberus, and in particular to help you navigate around the program even if you don’t at first understand all the features. The tutorial does not attempt to show you all the available features, to avoid confusing you with too much information, but instead concentrates on getting the main task done.

Some features are described in blue information boxes like this one. These are used to tell you about features that are not needed for the current worked example, but which may be useful for other situations.

This is an example of a yellow Tip box, used to point out short-cuts or hidden methods that will make Cerberus easier to use.

The online version of this tutorial covers essentially the same material as the study guide but in more depth, including greater use of screen captures and in some cases demonstration videos. New material is added to the online version before it is included in the study guide, and multiple choice quizzes are used to evaluate your progress. So, if you have internet access available in your location, we suggest you use the online tutorial as your primary method and keep the book as a reference. The online tutorial can be accessed at http://www.cerberustutorials.com There is inevitably some repetition in the worked examples, as the same steps are retraced. Variations are deliberately introduced where possible, to illustrate new points without distracting from the primary goal of learning how to model CT fatigue. Please have Cerberus running and carefully follow the steps described in dark blue text.


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Achilles Tutorial

3 Worked Example 1 Creating a CT string and calculating fatigue

Preparation • Scenario description • Sourcing input data • Preliminary discussion • Getting started

Configuration • String Manager • Reel Manager • Job Manager

Calculations • Reel-Trak • Summary

3.1 Scenario Description You recently received a new CT workstring in your location, and have already performed the first two jobs with it. You want to calculate and record the fatigue life of the pipe for these jobs.

• The first job, presented here as Worked Example 1, was a sand cleanout in a 12,042' well. You did not have a data acquisition system available for this job, so you recorded the events manually as best you could.

• The second job, covered later as Worked Example 2, involved milling a bridge plug in a 8,090' well. You had an Orion™ data acquisition system for this job1, so all the pipe movements and pressures were recorded electronically.

3.2 Sourcing Input Data Both jobs involve the same string and reel. Coiled Tubing The new CT, serial #CT34201, is a tapered QT-800 string of 1.50" diameter, 16,850' long. The first 7,050' has a wall thickness of 0.125", followed by 2,300' of 0.118", then the remaining 7,500' is 0.109" (you would normally get this information from the manufacturer’s data sheet)

Reel The above CT has been installed on a work reel R433 with the following dimensions: Core diameter = 68", Flange diameter = 115", Width = 84" Wellsite Information The first job was on well Hutchings-3. According to a data sheet kept by the engineer in charge (not reproduced here), the winch unit was positioned about 80' from the wellhead, and the top of the injector was 32' above the master valve. A 72" guide arch was used for the job.

1 Orion is a CTES product specifically designed to interface with Cerberus. Data from other acquisition systems can be imported and used in Cerberus, but this capability may require additional functionality and licensing. Contact CTES for further information.



String with Fatigue (a real example)

The following chart shows a 2.00" string that has performed 15 jobs in wells with depths between 8,000' and 10,000' deep. The wall varies from 0.109" at the downhole end to 0.175" at the uphole end, with several sections of continuous taper.

Note that moving the cursor over the diagram causes the used life to displayed at the top of the chart, and the CT properties to be displayed above the string diagram. Note also that the 80% limit line is shown as a horizontal dashed red line.

The used life is fairly constant (12-14%) for the downhole 6,000' [A], where the pipe is being run in and out of hole without much cycling and probably without much pressure. There is a small blip at each of the bias welds due to their higher derating factor.

The fatigue is higher (17-18%) in region [B], where the pipe was probably making repeated passes in some of the wells, possibly at pressure while pumping treatment fluid.

The drop (10-11%) in region [C] is probably because only some of the 15 wells extended to this depth and beyond, so this section of pipe left the reel less often.

The peaks (48% and 34%) at [D] are almost certainly because the pipe was repeatedly cycled over a small distance, probably at pressure, perhaps while cleaning out sand or trying to latch a fish. They may have occurred during one job or two separate jobs.

The uphole end of the string [E] never left the reel and consequently has almost no used life (0.3%, being the initial spooling onto the drum at the manufacturer).


Achilles Tutorial

4.6 String History The string history is a chronological list of key events in the life of the string, and in particular the jobs for which the fatigue life has been calculated. It can be viewed by either clicking on the toolbar button shown below, or by selecting the View | History Log… menu option from the main String Manager screen.

Being new, our current string has only one event, the date the database was created. A example for a string with a history of jobs is on the following page.

Recording events An entry in the history log is recorded automatically whenever the following events occur in String Manager or Reel-Trak: 1) The string database is created by the user. 2) A job is executed in ReelTrak to calculate new fatigue life. 3) The CT is cut, spliced or reversed. 4) The string database is locked or unlocked. 5) The string is saved under a different name. 6) The fatigue data is copied from another string. Users can only edit the Comments field, all the other entries are read-only.

Undoing events Events highlighted in red in the list can be undone, meaning the user can restore the string database to its state at some previous time in its life. Highlight the desired event in the history log and click on the Undo button. Naturally, this can have serious consequences for the integrity of the string record, and must be approached with great care.



4.8 Modifying the String The CT string can change in several ways during its life. Some pipe may be cut off the end or from the middle (cut), other pipe may be added onto the end (splice), or the string may be spooled from one drum to another with the result that the string is now back-to-front (reverse). Each of these scenarios is addressed in String Manager.

4.8.1 Cutting the string

Pipe is commonly cut off the free end of the string after each job, to remove any damage incurred during rig-up. Or, a section of pipe is sometimes cut from the middle of the string to remove a particularly high fatigue section, and the two ends then welded back together. To cut the string, either select main menu item Configuration | Edit | Cut string… or click on the toolbar button shown below.

The resulting screen has three cut options, described below. [the screen captures are cropped to save space]

Cut and Discard from End You simply want to cut off a length of pipe from the downhole end and throw it away. Specify the length you want to cut. The piece to be removed is shown on the diagram in red.

Click the cut button to perform the edit. The following entry is automatically made in the String History table.

Any information pertaining to the cut section, like welds or fatigue data, is discarded. You can undo this operation if necessary from the String History screen.


Achilles Tutorial

6.4.3 Inserting a Row If you want to go back and insert a row between two existing rows, you (a) select the row to insert above, and (b) click the Insert button. Select a row by clicking on the gray box on the far left of the row.

You now click the Insert button, or type <ctrl-I>

You will of course need to change the data for the new row.

6.4.4 Removing a Row To remove a row or rows, you (a) select the data to be removed, and (b) make the cut. Select a row by clicking on the gray box on the far left of the row.

You can select multiple rows by holding the mouse button down and dragging it. All the selected rows are highlighted as shown below.

You now click the Cut button, or hit the <delete> key on your keyboard, or type <ctrl-X>

You are prompted to confirm the cut. The selected rows are deleted if you respond Yes.



The string used life1 [A] is shown as bars2,3, one for each 10' segment4 of pipe. The dark blue is used life from this job, the gray is pre-existing damage from previous jobs. Moving the cursor over the chart will display [B] the used life at that position in the string. The spike at [C] is caused by the derating factor of the bias weld at that position5. The pipe at [D] has not been spooled from the reel and therefore has not been bent. The depth bar [E] shows where the pipe is relative to the reel and guide arch at surface. Green is pipe on the reel, blue is in the well6. The current data bar [F] shows the event and data from the log being processed. The status bar [G] shows whether you are in Test or Execute Mode.

1 used life is fatigue plus any downgrading due to exposure to hazardous environments and zones, see section 4.4. 2 you can display the life as a continuous line by setting plot options. 3 the bars are usually so close that the chart appears as solid blue, zoom in to see the effect shown in the example. 4 the default segment length can be changed in String Manager preferences. 5 right-click on or near the weld to view the weld properties. 6 right-click on the depth bar to view a full color key.


Achilles Tutorial

Note that there is an accumulation of fatigue at 8,975' as the bridge plug is milled, although the maximum is still only 3.6%.


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