Optimizing Hydraulic Fracture Design to Mitigate Casing Deformation in Deep Shale Gas Reservoirs with Complex Natural Fractures

ABSTRACT: Casing deformation in shale gas wells is a significant challenge that compromises wellbore integrity and reduces production efficiency, particularly in complex geological settings such as the Sichuan Basin, China. This study focuses on mitigating casing deformation risks in a typical shale gas pad consisting of four horizontal wells. A detailed geomechanical analysis was conducted, examining stress distribution and rock brittleness. A natural fracture model was developed, identifying four groups of fractures with lateral scales ranging from tens of meters to kilometers. A total of 31 stages with casing deformation risks were identified: 6 stages in Well-1, 6 in Well-2, 10 in Well-3, and 9 in Well-4. Three mitigation methods were proposed: optimizing stage and cluster design to avoid high-risk fracture zones (e.g., bypassing a 130-meter high-risk section in Well-2), reducing sand intensity to below 3 tons per meter in 2/3 of high-risk stages, and adjusting the fracturing sequence to prioritize high-risk stages. These methods effectively enhance wellbore integrity and optimize hydraulic fracturing operations. 1. INTRODUCTION Casing deformation during hydraulic fracturing presents a significant challenge in the development of shale gas reservoirs, especially in geologically complex regions such as the Sichuan Basin, China (Zeng et al., 2021; Liu et al., 2023; Han et al., 2023; Wu et al., 2024; Uribe-Patino et al., 2024). As global demand for shale gas rises, maintaining the integrity of wellbore casings becomes increasingly crucial to ensuring safe and productive gas extraction. Casing deformation, which results from excessive stress and strain on the steel casing, can compromise wellbore integrity, leading to reduced production, costly repairs, and even well abandonment in severe cases. The presence of natural fractures, varying stress conditions, and faults in the reservoir often exacerbate deformation, making it essential to understand these mechanisms and develop effective mitigation strategies to optimize hydraulic fracturing and ensure the long-term viability of shale gas wells.