Strings, casing

The casing string for a certain well is to consist of 13-f-in. casing with coupling outside diameter of 14.375 in. Determine the required outside diameter of the drill collar in order to avoid possible problems with running casing if the borehole diameter is assumed to be 17- in. 

CASING AND CASING STRING DESIGN Types of Casing... 

Based upon the primary function of the casing string, there are five types of casing to be distinguished. 

The production casing string for a certain well is to consist of 5-in. casing. Determine casing and corresponding bit sizes for the intermediate, surface and conductor string. Take casing data and bit sizes from Table 4-140. 

Having defined bit and casing string sizes, the setting depth of the individual strings should be determined. 

The second intermediate casing string is required and must be set at a depth of 10,000 ft. 

Casing and Casing String Design 1157 d = inside diameter of pipe in in. 

The term combination casing string is generally applied to a casing string that is composed of more than one weight per foot, or more than one grade of steel, or both. 

Casing must be designed to resist expected burst pressure at any depth. In burst pressure consideration, it is suggested to consider different design models depending upon the type of casing string. 

Evaluate an expected burst pressure acting on surface casing string in exploratory drilling if setting depth of the string is 5,000 ft, mud specific gravity is... 

The maximum tensile load acting on the casing string is often considered as the static weight of the casing string as measured in air. 

It should be pointed out that hydrostatic pressure does not produce an effective compression and, therefore, is not considered. If the casing string is suspended at the top of the hole that is filled with fluid, then the only effect of hydrostatic pressure is reduction of casing weight per foot and the string is effectively under tension. 

An example is offered on the following pages of the design procedure to be followed in designing a combination casing string. 

Design a combination casing string if data are as below ... 

Part 2. Check casing string on burst pressure obtained in Part 1 and make necessary corrections. 

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