Study on the Key Factors Analysis and Measures Prevention of Casing Deformation in Horizontal Wells for Unconventional Reservoir

Abstract Based on the structural distribution characteristics and fracture development characteristics of block 530 in the Junggar Basin, Xinjiang, and by using microseismic, logging, and in-situ stress data, the characteristics of casing deformation in deep shale gas wells were summarized, the mechanism and main controlling factors of casing deformation were clarified, a risk assessment chart for casing deformation was established, and targeted risk prevention and control countermeasures were proposed. The research shows that fracture slip activation by fracturing is the main controlling factor of casing deformation. The fracture approach angle in the work area is mainly 10°-50°, accounting for 65.34%, and the critical activation pore pressure increment is 6.05-9.71 MPa. For casing deformation caused by geological factors, the prevention and control measures mainly include avoiding risky fractures and selecting low-stress mechanism factor areas for well placement. For casing deformation caused by engineering factors, the prevention and control measures mainly include four aspects: When placing wells, try to avoid high-activation-risk and high-slip-risk fractures. When it is impossible to avoid them, try to select areas away from the center of the fracture; Optimize wellbore parameters, adjusting the wellbore azimuth can reduce the shear stress acting on the casing to a certain extent and reduce the degree of casing deformation; Optimize the wellbore structure design, and ensure that the curvature radius of the horizontal well bending section is greater than 200 m on the basis of not affecting the drilling encounter rate of high-quality reservoirs; Optimize the fracturing operation parameters, increasing the avoidance distance, reducing the single-stage construction pressure, and increasing the stage length are effective measures to reduce the risk of casing deformation.