introduction to petroleum engineering - lecture 10 final- casing

7/27/2019 Introduction to Petroleum Engineering - Lecture 10 Final- Casing

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BEng (Hons) Petroleum Engineering

Course:

Introduction To Petroleum Engineering

Instructor

Dr. Tarek Darwich


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Course Outlines: What is Petroleum Engineering?

The Life Cycle of Oil and Gas projects,

Origin, formation and accumulation of Petroleum,

Oil & Gas Exploration,

Appraisal of Oil & Gas Discoveries,

Development of Oil & Gas Discoveries,

Producing Oil & Gas Fields, Transportation of Oil & Gas,

The Petroleum Industry & the Environment,

Petroleum Economics.

I ntroduction to Petroleum Engineer ing

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Well Casing


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Drilling and Casing of the Reservoir Section


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https://www.ppdm.org/wiki/images/Drill_Hole_3.gif


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The casing String

After having drilled a certain length of hole, in order to guarantee itsstability it has to be cased.

The spacing between the pipes and the hole is then filled with a cementslurry to ensure a hydraulic and mechanical seal.

Casing cost comprises one of the major cost items in well drilling projects.

Casing acts as an anchorage for the BOP while drilling and for the Christmastree in production wells.

Proper planning and design of casing setting depth and casing pipe selectionare vital to achieve a cost-effective and safe well.


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Main Types of Casing Strings

The main types of casingare:

Conductor

Surface Casing

Intermediate Casing

Production Casing

Liners


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Surface Casing

This casing is set to: Prevent cave-in of unconsolidated, weak near-surface formations.

Provide blowout protection from high pressure shallow gas formations.

Isolate fresh water sands

Prevent loss of circulation

Partial protection of subsequent casing strings from corrosion

In deviated wells, the surface casing may cover the build section to preventkey seating of the formation during deeper drilling.

Typically cemented to surface or mudline.

Before setting the surface casing, no BOPs are installed.

Surface casing setting depth ranges from 300 to 5,000 ft, their diametersnormally range from 24 to 17 .


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Intermediate Casing

This casing is set to: Isolate unstable sections

Isolate lost circulation/low pressure zones.

Isolate Shallow production zones.

Often set in the transition zone from normal to abnormal pressure.

The cement top must isolate any hydrocarbon-bearing zone.

Some wells may require multiple intermediate strings.

Some intermediate strings may also be production strings if a liner is runbeneath them.

Intermediate casing diameters range from 17 to 9 5/8.


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Production Casing

This casing is set to: Isolate production zones

This casing maybe exposed to injection pressures from fracture jobs down

the casing, or gas lift, or any inhibitors.

The cement top must isolate any hydrocarbon-bearing zone.

A good primary cement job is much more critical for this string.

Production casing and production liners are commonly have gas-tightconnections.

Production casing diameters range from 9 5/8 to 5 with the 7 casing iscommonly in use.


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A Liner

A casing string that does not stretch back to the wellhead but instead is hungfrom another casing string.

casing is set to: Used in lieu of full casing strings to reduce cost

Allow the use of larger tubing above the liner top Not exceed a tension limitation on the rig

Liners can be either intermediate or production strings.

They are typically cemented over their whole length.


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Preliminary Casing Design It is an important part of the well planning step.

Preliminary well design includes: Data gathering and interpretation

Determination of shoe depths and number of strings.

selection of hole and casing sizes

Mud weight design

Directional design.


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Required Information in Casing Design Formation Properties:

Pore pressure

Fracture pressure

Formation compressive strength (borehole failure)

Temperature profile

Location of squeezing salt and shale zones

Location of permeable zones Chemical stability/shale zones (mud type and exposure time)

Lost Circulation zones

Shallow gas

Location of fresh water sands

Presence of H2S and/or CO2.

Directional Data: Surface location

Target Location

Well interference data


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Required Information in Casing Design Minimum Hole Diameter Requirement:

Minimum hole size required to meet drilling objectives

Logging tool OD

Tubing size(s)

Packers and related equipment requirments.

Subsurface safety valve outer diameter (especially for offshore wells)

Completion requirements

Production Data Packer Fluid Density

Produced Fluid Composition

Worst case loads which may occur during completion, production and workover operations.

Other Requirement: Available inventory

Regulatory requirements

Rig equipment Limitations


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Slim hole Drilling & Casing Issues Small hole sizes (and consequently casing sizes) reduce the total

cost of the well since:

drilling times are faster

less mud to be used (purchase and disposal of mud)

smaller mud equipment can be used (cleaning, pumping, .)

smaller casing can be used (cheaper)

smaller rig can be used

Rig site can be smaller

Constraints

Well control issues (higher velocities in the annulus in case of gas kick)

Smaller production tubing sizes and artificial lift equipment.


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API Casing Performance Properties The American Petroleum Institute (API) has developed internationally accepted

standards for oilfield tabulars.

These standards are summarised in bulletins that contain the minimumperformance properties and equations to calculate them.

It SHOULD be understood that these properties are guidelines (minimumrequirements).

For casing design calculations, the exact strength values provided by the individualmanufacturer shall be applied.

A casing is defined by: Casing outside diameter (OD)

Weight per unit length (determines wall thickness)

Grade of steel

Type of coupling

Length of joint


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API Casing Grades


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introduction to petroleum engineering - lecture 10 final- casing

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