Initiation Analysis of Hydraulic Fractures in Glutenite Reservoirs: Implications from a Post-Fracturing Cored Well in the Triassic Baikouquan Formation, North Slope of Mahu Depression

Summary In this study, we investigate the initiation and behavior of hydraulic fractures (HFs) in glutenite reservoirs using data from a post-fracturing cored well in the Triassic Baikouquan Formation, North Slope of Mahu Depression. Through the integration of core observation, imaging logs, and computed tomography (CT) scans, we identified 335 HFs. Statistical analysis revealed shear fractures to be twice as prevalent as tensional fractures in glutenite reservoirs, with shear fractures exhibiting smooth surfaces, planar geometry, and relatively straight propagation paths, while tensional fractures appeared rough, irregular, and tortuous. We identified three distinct fracture growth mechanisms—tensional fractures and two types of shear fractures controlled by different stress mechanisms (inverse fault stress and strike-slip fault stress). Each mechanism resulted in specific fracture characteristics, with tensional fractures exhibiting solitary behavior and shear fractures displaying multiple cracks with higher density and a straighter propagation path. Numerical simulation results demonstrated that HF propagation distance increased with displacement, emphasizing its significant influence on fracture behavior. Stress shadow effects induced by HFs caused stress redistribution, leading to principal stress deflection and fracture reorientation. At net pressures exceeding 25 MPa, induced stress fields in the gap between perforating clusters transitioned to favor shear fractures, while tensional fractures predominated in the position of perforation. The findings provide insights into the distribution and characteristics of HFs in glutenite reservoirs and underscore the importance of controlling net pressure during hydraulic fracturing operations. By analyzing the initiation of different types of hydraulic fractures, we provide recommendations for fracturing treatments to guide field production.