Experimental investigation on the influence of perforation on the hydraulic fracture geometry in shale

The physical simulation experiment of hydraulic fracturing is an effective way to obtain the geometry and propagation criterion of hydraulic fractures. The physical and mechanical properties of the Longmaxi shale were investi- gated by using XRD,scanning electron microscope,strength test and other experiments. Moreover,the tri-axial fractu- ring simulator has been used to study the effects of physical and mechanical properties of shale,and the perforation on the fracture geometry. The results show that:① Four types of hydraulic fractures corresponding to three types of perfo- ration are summarized,in which the combination type perforation has a certain promotion effect on the formation of complex fractures. When the phase angle and spacing between perforations are too small,the interference between frac- tures is enhanced,which is not conducive to increasing the fracture scale. ② The pressure-time curves show obvious differences due to the different types of perforation. The fluctuation degree of the curve and the complexity of fractures have a positive correlation to a certain extent. ③ The penetrating,branching of hydraulic fractures are the precondition for the formation of fracture networks when they intersect with the structural plane. The physical and mechanical prop- erties such as anisotropy,micro fractures,brittleness index will affect the propagation path and the tortuosity of hydrau- lic fractures in shale.