Category Archives: Casing Design

Casing Size Selection – How To Select Casing Size to Match the Drilling and Completion Goal

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We’ve learnt several topics in regard to casing design and this article will demonstrate you how to determine casing size in the well.

casing-size-selection-cover

Casing size selection is determined from the inside outward and it starts from the bottom hole.

The sequence of design is based on the following steps;

1. Proper sizing of tubing is determined by inflow performance analysis.

2. Completion equipment is planned to install with tubing string. Determine which part has the biggest OD. This will directly impact of production casing.

3. Bit size for drilling the production section.

4. Casing size must be smaller than bit size and its ID must be bigger than the biggest component in completion string.

5. Once you get the last casing string, the upper string is selected by repeating bit selection and casing selection similar to step #3 and #4.
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Casing Seat Selection – How To Select Casing Setting Depth

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From the previous article, you’ve learnt about overall of casing design process and in this article we are going to discuss about how to select casing setting depth. The selection of casing string and setting depth is based on formation pore pressure and fracture gradient of the well.

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For the casing setting depth determination, pore pressure and fracture gradient are normally described in PPG (Figure 1).

Figure-1---Pore-Pressure-and-Fracture-Pressure-Plot

Figure 1 – Pore Pressure and Fracture Pressure Plot

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Casing Design Overview – Overall Process of How To Do Casing Design in Oil and Gas Industry

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After understanding the basic of each casing string run in oil wells, we will go into casing design overview. This article will give you general ideas of casing design.

casing-Design-Overview

Casing Design Objectives

The items below are design objectives for well constructions which drilling engineers must consider.

  • Design must meeting production strategies.
  • Design must provide mechanical integrity based on anticipated load cases which will be encounter during life time of the well.
  • Cost of well must be economic.
  • Design must provide ways to be able to plug and abandon the well at the end of wells life.

These objectives are generic and your wells may have additional objectives based on business needs.

Data Required for Casing Design

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Basic Understanding of Oil Well Casing and Tubing

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Oil well construction requires several casing string to reach a planned depth of a well therefore we will discuss about the basic of each casing string used in the oil wells.

Basic-Understanding-of-Oil-Well-Casing-and-Tubing

In this article, we will cover the following strings;

  • Conductor Casing
  • Surface Casing (Structural Casing)
  • Intermediate Casing
  • Casing Liner
  • Production Casing
  • Production Tubing

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