关键词: 水力压裂, 射孔布置, 裂缝起裂与扩展, 断裂韧性

Abstract: Understanding hydraulic fracturing initiation and propagation in low permeability reservoir is of great significance for exploiting and enhancing recovery of unconventional oil and gas resources. Cement, mortar and quartz sand were mixed to model the natural shale rock. Our laboratory tests proved that, the mechanical properties, especially fracture toughness, were close to those of the natural shale rock. The numerical codes FRANC 3D and ANSYS were adopted to probe into initiation and propagation of hydraulic fractures in reservoir rock in different horizontal stress ratio and perforation layout. The simulation and analysis have indicated that：1) Perforation fracturing initiation and propagation in three dimensions are properly simulated by FRANC 3D and ANSYS; 2) The initiation fracture pressure decreases with the increase of horizontal stress ratio; 3) Perforation parallel to the maximum horizontal stress has the smallest initiation fracture pressure. Propagation plane deflection tends to be parallel to the maximum horizontal stress when they are not in parallel; 4) Linearly distributed perforation is superior to symmetric perforation and staggered perforation as it provides the minimum initiation fracture pressure.

Key words: hydraulic fracturing, perforation, crack initiation and propagation, fracture toughness