INFLUENCE OF RESERVOIR HETEROGENEITY ON HYDROFRACTURE

Based on the mesoscopic heterogeneity of rock, the RFPA2D-Flow software is used to explore the law of fracking. In this model, material is discretized into a large number of elements with the same size and different mechanical and permeable parameters in order to represent heterogeneity of rock. A coupling analysis of seepage and damage under hydraulic fracturing on rock is performed to simulate the fracture process of rock. Through the numerical results of single and double hole model, we draw the conclusions as follows:(1)The rock heterogeneity influences the pattern of fracture, results in the branching of hydraulic fracture. With the increase of the homogeneity, form of hydraulic fracture gets much smoother. The fractures in the single wellbore model are more symmetrical on both sides of wellbore. The connectivity between the double holes gets worse.(2)Heterogeneity of rock has a significant influence on the initiation and breakdown pressure. Both fracture initiation and breakdown pressure values increase with the increasing homogeneity. When the rock is homogeneous, both are almost equal.(3) At the same boundary conditions, the stress distribution curve of homogenous model is smooth and continuous, however, the curve display fluctuation in heterogeneous model. The fluctuation gets obvious with the increasing heterogeneity.(4)Pore pressure increment zone exists between the two holes in the double hole model, anattract effect occurs between the two holes, the critical pressure is influenced by the orientation of the two holes. The above results are of some significance to hydraulic fracturing tests and engineering practice.