Visualization of Casing Stress Characteristics under Non-Uniform In-situ Stress and Non-uniform Cement Sheath

Abstract

Casing damage is a common problem in oil and gas fields due to the complicated stress state of casing. Especially in the horizontal well section, the casing is difficult to be centered, and the eccentric casing is prone to failure under non-uniform in-situ stress. In order to study the influence of non-uniform in-situ stress and non-uniform cement sheath on the stress state of casing, a numerical model of the coupling of casing, cement sheath and formation is established. The stress distribution characteristics of casing under four conditions of uniform in-situ stress uniform cement sheath, uniform in-situ stress non-uniform cement sheath, non-uniform in-situ stress uniform cement sheath and non-uniform in-situ stress non-uniform cement sheath are compared. The results show that the non-uniform cement sheath will cause the stress distribution of casing to be uneven, and the maximum stress on the casing is proportional to the amount of eccentricity. The non-uniform in-situ stress will cause the casing stress to be uneven and affect the extreme value of the stress on the casing inner wall. The results will provide the theoretical basis for the casing damage prediction effectively.