A Design Method for Irregular Casing in Salt Rock Formation

Abstract

The invention relates to a method for designing a salt rock stratum irregular-shaped sleeve. According to different salt rock stratum creep stress states, by changing the inner diameter or outer diameter of the irregular-shaped sleeve, the sleeve cross section shape suitable for a crustal stress level condition is determined. The irregular-shaped sleeve has the following two forms: an inner wall of the sleeve is circular, and an outer wall of the sleeve is oval; and an inner wall of the sleeve is oval, and an outer wall of the sleeve is circular. When the irregular-shaped sleeve is put into a shaft, the position with the maximum wall thickness and the direction of the maximum horizontal crustal stress are uniform. By means of the method, effective stress of a sleeve body under an uneven horizontal crustal stress state can be effectively reduced, the sleeve can be prevented from being damaged, and the technical problem that the strength of the sleeve with the existing wall thickness under the uneven horizontal crustal stress state is not enough and the sleeve can not be kept well in the follow-up production process is solved.

Description

Technical field [0001] The invention relates to a casing design method aimed at salt rock formations. Background technique [0002] Drilling in salt-gypsum layers in deep formations is one of the major technical problems in drilling engineering. Due to the particularity of rock properties in salt-gypsum layers, the complex conditions of drilling and completion of salt-gypsum layers and the forms of downhole accidents can be described as "dissolution, shrinkage, collapse, swelling, leakage, Stuck, sprayed, damaged" 8 words to describe. Especially when the salt-gypsum layer creeps after drilling the wellbore, it often causes accidents such as wellbore instability, pipe sticking, and casing collapse after cementing. In my country's oil and gas drilling projects, large sections of complex rock-salt formations are often encountered. During the drilling process, it is easy to cause shrinkage sticking or blockage when tripping, and blockage when running the casing. At the same ti...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a design method for special-shaped casing in salt rock formation, which can effectively reduce the effective stress of the casing body under the non-uniform horizontal stress state of the casing, prevent the casing from being damaged, and solve the current problem. There is a technical problem that the strength of the thick-walled casing is not enough under the state of non-uniform horizontal ground stress, which cannot ensure that the thick-walled casing remains intact in the subsequent production process

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