Induced Casing Deformation in Hydraulically Fractured Shale Gas Wells: Risk Assessment, Early Warning, and Mitigation

In recent years, casing deformation has become a key factor affecting the scale and efficiency of shale gas development. Consequently, a fast and efficient integrated prevention, control, and treatment technology for casing deformation is of great significance in terms of both theory and application. This paper combines a geological mechanics analysis and multi-cluster fracture propagation to investigate the risk evaluation, early warning and identification, and warning and identification technology relating to casing deformation and its application. It proposes a method for the dynamic and static evaluation of casing deformation risk levels and types, and establishes an index system incorporating stress, fracture, time, and space factors. This four-factor evaluation method is in greater alignment with field conditions. It also proposes a method for the early warning and identification of casing deformation based on fracture monitoring and an operation curve, and clarifies the dominant engineering factors around casing deformation. According to the findings, the total fluid volume per stage has a greater impact on casing deformation than a high pump rate. The prevention and control of casing deformation should preferably be realized by optimizing the fracturing parameters. Moreover, the paper reviews existing technologies for treating casing deformation, several of which are defined as major technologies: small-diameter bridge plug staged fracturing and small-size gun perforation, and long-stage multi-cluster asynchronous fracture initiation and composite temporary plugging and diversion. The study results provide support for a significant reduction in the casing deformation rate during fracturing, improving the effective stimulation degree in the casing deformation section in shale gas wells in the southern Sichuan Basin. These results could serve as references for subsequent research.