Key Factors Influencing Casing Deformation in Sichuan Basin Shale Gas Reservoirs

ABSTRACT: Casing deformation during hydraulic fracturing in shale gas reservoirs is a critical issue affecting wellbore integrity, operational efficiency, and production performance. This study investigates 18 shale gas wells in the Sichuan Basin, China, identifying 43 casing deformation points. Using geomechanical models, well logging data, and core analysis, the study examines the key mechanisms of deformation, including large dogleg severity, high incidence angles, and natural fractures. Three primary deformation types were identified: Type I due to large dogleg severity, Type II from high incidence angles, and Type III associated with natural fractures and fault slippage. These deformations commonly occur at geological interfaces, such as the Long1-1 and Long1-2 layers, where mechanical contrasts exacerbate stress concentrations. The distribution of observed cases includes 21 Type I, 20 Type II, and 14 Type III deformations. This research provides a comprehensive framework for understanding casing deformation mechanisms and offers practical recommendations for optimizing well designs, drilling strategies, and real-time monitoring to improve wellbore stability and reduce deformation risks in shale gas operations. 1. INTRODUCTION Casing deformation during hydraulic fracturing in unconventional shale gas plays poses significant challenges to wellbore integrity, operational efficiency, and production performance. It not only compromises the mechanical stability of the wellbore but also affects the overall economics of shale gas operations by increasing repair costs and decreasing productivity. This issue is particularly prevalent in regions with complex geological settings, such as areas with high fault activity and dense natural fractures. Although casing deformation has been acknowledged as a critical concern, especially in regions like North America, research and published data remain limited (Uribe-Patino et al., 2024). In contrast, significant progress has been made in understanding casing deformation in other regions, such as the Sichuan Basin in China (Zeng et al., 2021; Liu et al., 2023; Han et al., 2023; Wu et al., 2023, 2024), highlighting the need for further research in other global shale gas plays, including North America and Argentina's Vaca Muerta shale (Filipich et al., 2024).