Casing Tensile Loads and Design Considerations Quiz

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Questions and Answers

What is the primary purpose of the Surface Casing?

Prevent washouts of soft formations (correct)

Provide isolation or protection for interval of concern

Convert liners to full strings

Isolate production zone

Which casing type is specifically designed to address borehole stability issues?

Conductor

Intermediate Casing (correct)

Production Casing

Injection / gas lift conduit

What is the main function of Liners in a well casing design?

Isolate differing pressure regimes

Provide isolation or protection for interval of concern (correct)

Isolate production zone

Tubing leak protection

Which type of casing string configuration allows BOP installation for pressure control?

Surface Casing Signup and view all the answers

What is a common function of Production Casing?

Isolate production zone Signup and view all the answers

Which casing string is considered a critical barrier to the well according to the text?

Production Casing Signup and view all the answers

What is the purpose of a guide shoe or casing shoe in a casing string?

To guide the casing past obstructions in the wellbore Signup and view all the answers

What component allows the casing to be suspended from the wellhead in a casing string?

Casing hanger Signup and view all the answers

What purpose do float collars serve in a casing string?

Aid in cementing operations Signup and view all the answers

Which parameter is NOT considered a part of the casing dimensional specifications?

Young's Modulus Signup and view all the answers

What type of equipment are scratchers in a casing string primarily used for?

Centralization Signup and view all the answers

How are casing strings typically named?

Based on their functions Signup and view all the answers

What is the primary function of a liner in well casing?

To reinforce and extend the previous casing string Signup and view all the answers

What is a key advantage of using a liner compared to running a full casing string?

All of the above are advantages of using a liner Signup and view all the answers

What is the typical length of overlap between a liner and the previous casing string?

200ft - 400ft Signup and view all the answers

Which component is used to anchor a liner to the inside of the previous casing string?

Liner hanger Signup and view all the answers

In what type of well sections can liners be used?

In both intermediate and production sections Signup and view all the answers

What is the purpose of pressure testing a liner before running the well completion?

To verify the integrity of the liner and its connections Signup and view all the answers

What is the primary purpose of casing a well?

All of the above Signup and view all the answers

What is the approximate length of each pipe joint in a casing string?

40 feet Signup and view all the answers

What percentage of the total well cost is typically attributed to casing?

20-30% Signup and view all the answers

What is the purpose of cementing the annular space between the casing string and the borehole?

All of the above Signup and view all the answers

How many casing strings are typically required to reach the target depth of a well?

3-4 Signup and view all the answers

What is the primary purpose of setting the casing string at an appropriate depth?

To prevent cratering of formations and uncontrolled flow to the surface Signup and view all the answers

Which of the following is NOT a reason for running an intermediate casing string?

Facilitate open hole completion Signup and view all the answers

What is the main purpose of the production casing?

Both A and C Signup and view all the answers

If a gas influx occurs while drilling the next hole section, and the casing is set too high, what is the potential consequence?

The formations around the casing may crater, and the influx may flow to the surface Signup and view all the answers

What is the purpose of running a liner instead of a production casing string?

To facilitate an open hole completion Signup and view all the answers

How is the number of intermediate casing strings determined?

Based on the number of troublesome formations encountered Signup and view all the answers

Study Notes

Overview of Casing Design

Casing design parameters are affected by location's geological conditions, formation pore pressure profile, and fracture pressure profile.

Types of Casings

Conductor casing: provides structural support, prevents washouts of soft formations, and serves as the first flow conduit.
Surface casing: isolates fresh/groundwater formations, allows BOP installation for pressure control.
Intermediate casing: addresses borehole stability issues, isolates differing pressure regimes, and isolates problematic formations.
Production casing: isolates the production zone, provides tubing leak protection, and serves as an injection/gas lift conduit.
Liners: provide isolation or protection for an interval of concern and can be converted to full strings with tiebacks.

Principal Loads on Casing

Operational limits (drag, margin of overpull) and doglegs & buckling affect casing design.

The Casing Design Process

Strength Parameters

Casing dimensional specifications (size, OD, ID)
Yield strength
Wall thickness
Material properties (Young's Modulus, Poisson's Ratio)
Composition, hardness, toughness, etc.

Design Uncertainties

Changes in load cases (worst-case scenario)
Load parameters (changes based on operational requirements)
Failure mode

Data Requirements for Casing Design Process

Rig type
Pressures (pore and fracture)
Temperature profile
Contaminants level (reservoir and other formations)
Directional survey – planned trajectory
Casing OD and minimum ID
Tentative casing setting depth based on project requirements
Casing type (subject to procurement plan)
Mud density
Cement density

The Components of a Casing String

A casing string is composed of individual joints (40 ft in length) connected by threaded connections.
A guide shoe or casing shoe is attached to the bottom of the casing string.
A casing hanger allows the casing to be suspended from the wellhead.
Other equipment may be included in the casing string or attached to the outside of the casing:
- Float collar
- Centralizers
- Scratchers

Casing Terminology

Casing strings are named based on their functions.
Liner: a short casing string suspended from the inside of the previous casing string by a device known as a liner hanger.

Introduction to Casing

Wells are drilled in sections, with each section sealed off by lining the inside of the borehole with steel pipe (casing).
The annular space between the casing string and the borehole is filled with cement before drilling the subsequent hole section.
Casing costs account for 20-30% of the total well cost.
Great care must be taken when designing a casing program that meets the requirements of the well.

Reasons for Casing

To prevent unstable formations from caving in.
To protect weak formations from high mudweights that may be required in subsequent hole sections.
To isolate zones with abnormally high pore pressure from deeper zones which may be normally pressured.

Casing Terminology – Intermediate Casing

Intermediate (or protection) casing strings isolate troublesome formations between the surface casing setting depth and the production casing setting depth.

Casing Terminology – Production Casing

The production casing is run through the pay zone or set just above the pay zone (for an open hole completion or prior to running a liner).
The main purpose of this casing is to isolate the production interval from other formations (e.g., water-bearing sands) and act as a conduit for the production tubing.

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Description

Learn about the source and combination of tensile loads on casing during different operations, as well as how bi-axial and tri-axial loads are accommodated in the casing design process. Explore the sealing off of well sections using steel pipe and the importance of casing in drilling operations.