Experimental and Numerical Investigation on Interaction Mechanism Between Hydraulic Fracture and Natural Fracture

Hydraulic fracture propagation under natural fracture distributions has always been a hot topic in unconventional reservoir stimulation. In this work, the hydromechanical behavior controlled by rock fabric is understood and quantified via physical and numerical simulations. A unique large-scale (762 mm × 762 mm × 914 mm) hydraulic fracturing simulation experimental technology considering quantitative simulation of the cementation performance of natural fractures is established. Combined with the laboratory results, a planar, heterogeneous, multiscale hydraulic fracturing numerical model based on the cohesive zone method is developed and verified. The experimental and numerical results reveal three simple modes between hydraulic fracture and natural fracture, namely, natural fracture opening, shearing and crossing. In addition, some mixed modes of complex fracture exist. Compared with engineering factors, the interaction between natural fractures and hydraulic fractures is more obviously controlled by geological factors. A greater horizontal stress difference, angle between the maximum horizontal stress direction and natural fracture, tensile strength of natural fractures and pumping parameters are conducive to crossing natural fractures. On the basis of the simulation results, three field-scale diagrams of the interaction between natural fractures and hydraulic fractures are systematically established. The interaction results can be visualized in reference to most geological and engineering conditions. Considering the greater horizontal stress difference and natural underdevelopment, the single model of fracture propagation along the maximum direction is dominant in most tight or shale oil basins in China. The physical and numerical simulation technologies in this paper will help to optimize the volume stimulation design of unconventional reservoirs.