Fourier Transform-Based Inversion of Surface Deformation for Risk Assessment of Casing Damage: A Case Study of the Daqing Oilfield

The intrinsic mechanism linking surface deformation to casing damage due to layer slippage remains unclear. Moreover, no method currently exists for calculating the slip deformation field of horizontal structural weakness planes from surface deformation. Therefore, we present a novel approach to infer formation pore pressure using surface deformation data based on Fourier transform and Wiener filtering. A forward modeling method is used to determine slippage along horizontal structural weakness planes, and a theoretical method is developed to derive slippage from observed surface deformation. We also apply a critical slippage threshold for casing damage to delineate risk zones via a maximum slip calculation model using data from the Daqing Oilfield in China. Our results reveal a strong correlation between casing damage occurrence and identified risk areas; within 6 months, 12 new casing damage wells appeared in high-risk areas, compared with 5 in low-risk zones. This method provides a scientific basis for the formulation of prevention schemes against shear casing damage in oilfields with weak horizontal structures.