Analysis and Optimization of Construction Parameters for Preventing Casing Deformation in the Changning Shale Gas Block, Sichuan Basin

In order to solve the problem of casing deformation in the Changning shale gas block in the Sichuan Basin, the construction parameters of wells with deformed casing were analyzed and optimized. The fracture and in-situ stress model of the platform H were established based on 3D seismic data, logging and test data. The hydraulic fracturing numerical simulation was conducted based on the Mohr-Coulomb critical stress and mass conservation law. Based on the classification of slip risk, the relationship between the construction parameters for fracturing and activation of fracture zones was analyzed. The statistics and analysis results showed that when only fluid volume reduction measures were taken, the casing deformation ratio in fractured zones was 21.7%. When only the flowrate reduction measures were taken, the casing deformation ratio was 8.1%. It can been seen from fracturing simulation that, for those faults with high slip risk, when the fluid volume is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 17% and 26%, respectively. When the flowrate is reduced by 20%, the length of activated fault and the number of activated fractures are reduced by 3% and 6%, respectively. For those faults with medium slip risk, when the fluid volume is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 22% and 30% respectively. When the flowrate is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 43% and 60%, respectively. The research results showed a suggestion on construction parameters that reducing fluid volume for high slip risk faults and reducing flowrate for medium slip risk faults. This could provide a reference for solving casing deformation problem on site.