Casing Shear Deformation Analysis of Shale Gas well Based on Shale Formation Strength Reduction Method

The problem of casing deformation caused by fault slippage due to the hydraulic fracturing process in Changning-Weiyuan area, Sichuan Province, has seriously affected the economic benefits of shale gas wells. In order to clarify the relationship between the strength of fractured rock mass, the size of fractured rock mass, and the parameters of cement sheath, based on the characteristics of artificial shale formation during hydraulic fracturing, the shale strength is reduced. The finite element model of the casing, cement sheath and formation is analyzed, and the deformation law of the casing during the shale strength reduction process is analyzed. The results show that the greater the reduction of the strength of the shale, the greater the risk of shear deformation of the casing. The fracturing height has a great influence on the casing deformation, which increases substantially linearly, and the crack width has little effect on the casing deformation. 2 The Young’s modulus of the cement sheath has little effect on the deformation of the casing, and reducing the Young’s modulus of the cement sheath cannot effectively alleviate the deformation of the casing. Increasing the wall thickness of the cement sheath increases the contact area between the cement sheath and the formation, and the degree of deformation increases. 3 increasing the wall thickness of the casing can alleviate the deformation degree of the casing, and the wall thickness of the casing should be optimized during the fracturing process. The research results have a certain guiding role for the prevention and treatment of casing deformation.