Research on Fracture Network Propagation Pattern of Shale Reservoir Based on Fracture Mechanics

The fracturing of shale reservoir belongs to the crack propagation problems of brittle material. Based on the theory of linear elastic fracture mechanics,the impact of natural fracture on hydraulic fracture is studied,and calculation model of the new crack initiation angle are constructed.On this basis,the crack propagation calculation program is developed,which is made to analyze the controlled factors of fracture network propagation pattern on the way of geology and engineer.Studies show that the natural fracture prone to shear failure and the hydraulic fracture turns to the direction of natural fracture,which is easy to form complex fracture network on the occasion of low horizontal principal stress difference and low approaching angle.The new crack initiation angle has a close relationship with natural fracture dip,horizontal stress difference and pressure in the fracture.Distribution of natural fracture(dip and distance)has an impact on the net pressure at the fracture opening and the biggest width of the fracture.Fracturing fluid with low viscosity is in favor of increasing the limit extension distance,and high construction displacement can increase the natural fracture width of the intersection and be helpful for the proppant to pass through bending section which can avoid bridge plug.The research results can provide an important theoretical reference for the fracturing design in shale reservoir.