Investigation of Casing Stress Distribution under Combined Effects of Perforation Operation and Initial Stress Field Induced by Cementing Defects

Summary Quality defects caused by gravity and other factors during cementing operations in horizontal wells can significantly affect the cement sheath’s ability to protect the casing during subsequent perforation operations. Currently, research on the influence of cementing defects on the casing during the perforation process is relatively scarce. In this paper, we establish a perforation simulation model that considers the initial stress of the casing caused by cementing defects. The impact of cementing defects on the stress distribution and risk zone of the casing after perforation are analyzed using the fluid-structure coupling method. The research results show that under the defined boundary conditions, eccentricity has a relatively small effect on casing stress and risk zone after perforation, but it promotes the axial expansion of the low-stress region around the channel. With the increase of the circumferential spread angle, the maximum stress of the casing before perforation first increases and then decreases, and the position of the maximum stress changes accordingly. After perforation, the high-stress area of the casing is mainly distributed around the perforation channel and extends axially. When there is a missing thickness, the maximum stress of the casing before perforation increases as the missing thickness increases, and the maximum stress is primarily located at the inner wall of the casing adjacent to the edge of the circumferential spread angle. The distribution of high-stress regions around the channel after perforation is predominantly elliptical. The research results can provide important references for assessing the failure risk of the perforated casing with cementing defects in horizontal wells.