Chemical-technological phenomena occurring during borehole cementing operations in terms of casing design, with particular emphasis on their collapse and burst strength

Abstract

One of the most important issues that needs to be addressed in the borehole design process is the optimal design of the borehole structure, including the appropriate selection of individual casing columns and their setting given the assumed geological and cementing-technical conditions. Specific geological and technical conditions imply a number of both conditions and constraints. A kind of dimensional unification of pipes adopted by API many decades ago, i.e. a series according to the outer diameter of the pipes, constitutes the main natural constraint. Other elements of this unification, such as a series of steel grades or of classic and PREMIUM thread connections were implemented gradually as drilling technology developed. Regardless of these conditions, one thing always remains the same when designing casing and selecting production tubing, i.e. maintaining the balance between the existing loads acting on the pipes during the drilling process and operation of the borehole and the minimum mechanical strength of the pipes. This article reviews the methods and guidelines for casing pipe designing published by API and of computer programs, including StressCheck, which is currently one of the commonly used pipe design tools. The strength issues discussed in the article refer mainly to the pipe body, ignoring the complex issue of the strength of the thread connections, especially those of PREMIUM type, whose qualification is not subject to API standards, but to the guidelines contained in ISO 13679.