Study on numerical simulation of effect on natural fractures to hydraulic fracture propagation in shale reservoirs

There are a large number of natural fractures in shale reservoirs,which have a significant effect on fracture propagation during hydraulic fracturing. In order to explore the influence of natural fractures on the propagation law of hydraulic fractures,considering the coupling effect between rock reservoir deformation and fluid flow in fractures and the interaction between natural fractures and hydraulic fractures,a two-dimensional fluid-solid coupling hydraulic fracturing fracture intersection propagation model for shale reservoirs is established. The correctness of the model was verified by comparing the results with the classical KGD model and the laboratory test results. The research shows that with the linear increase of horizontal stress difference,the water injection pressure of fracture initiation increases linearly. The maximum horizontal principal stress induces the propagation path of hydraulic fracture and natural fracture. When the hydraulic fracture intersects with the natural fracture,the water pressure at the water injection point drops sharply. The stress concentration area is prone to occur at the fracture intersection,and the width at the fracture intersection is discontinuous. The larger the intersection angle of natural fractures,the more obvious the discontinuity of fracture width. At the same time,the shorter the fracture length,the smaller the area. Natural fracture length has little effect on fracture length,but has obvious effect on fracture width and area. However,natural fracture length has little effect on fracture length,but has obvious effect on fracture width and area. The research can provide reference for the design of hydraulic fracturing during actual shale reservoir.