Geomechanical Characteristics of Cretaceous Ultra-Deep Sandstone Reservoirs in the Southern Keshen Area, Kuqa Depression: Implications for Exploration and Development

Abstract

Significant progress has been made in exploring ultra-deep tight sandstone gas in the Tarim Basin, but sweet spot prediction remains challenging in the Keshen block of the Kuqa Depression. Based on integrated geological, experimental, and seismic data, this study characterizes the geomechanical properties and in situ stress field of the Cretaceous Bashijiqike Formation and identifies the main controls on reservoir quality. 3D geomechanical modeling and finite element simulations reveal that fracture development, stress–fracture angle, structural style, and the absence of stress concentration jointly govern reservoir favorability. Stress concentration can coexist with fracture development due to differential sandstone–mudstone deformation, leading to fracture deactivation. Favorable reservoirs occur in structural positions with extensive natural fractures, moderate principal stress–fracture angles, and low stress concentration. Coupling between in situ stress and natural fractures is the key to sweet spot prediction. The proposed geomechanical workflow improves precise identification of engineering and geological sweet spots, enhancing exploration and development efficiency in ultra-deep tight gas reservoirs.