An Analytical Approach to Prevent Casing Deformation in Deep Reservoir Stimulation -A Case Study from China

Abstract Casing deformation in deep shale gas horizontal wells (vertical depth >3,500m) during staged fracturing operations has become a critical constraint affecting development effectiveness in the Luzhou Block of Sichuan Basin. Through multi-factor analysis of representative deep shale gas horizontal wells, this study clarifies the primary characteristics and contributing mechanisms of casing deformation. The casing deformation mechanisms in Luzhou's deep horizontal wells are governed by both geological reservoir factors and engineering parameters. Well Lu 201H4, the first pilot horizontal well in the central Luzhou area, serves as a critical reference for resource development planning and fracturing design optimization in this region. Adhering to an integrated geology-engineering approach, a detailed evaluation was performed based on geological and operational characteristics of the well pad, as well as insights from offset well completions. Key considerations included the distribution of natural fractures, formation flexure, and fault systems. By coupling a geomechanical model with these parameters, slip potential risk assessments were carried out across six major natural fracture zones. Results indicate that the coefficient of friction across the platform ranges from 0.28 to 0.52. With the goal of maximizing Estimated Ultimate Recovery (EUR), the study incorporated natural fracture prediction, quantitative slip potential assessment, and engineering parameter optimization to enhance complex fracture network connectivity. This effort resulted in the establishment of an integrated geoengineering casing deformation prevention system, which provides critical guidance for lifecycle well design and field execution. The system effectively mitigates operational challenges such as fracture interference and casing deformation. This prevention methodology has since been successfully applied across multiple shale gas blocks in southern Sichuan, yielding significant improvements in single-well productivity and economic returns. The approach offers valuable insights and a replicable model for the efficient development of unconventional reservoirs both in China and globally.