关键词: 砂砾岩, 水力压裂, 数值模拟, 扩展过程, 裂缝

Abstract: Great variability of lithology and permeability, low porosity, poor connectivity, complex pore structure and serious heterogeneity are the common characteristics of glutenite reservoir. Therefore it is difficult to control crack propagation form of hydraulic fractures, and undertake a large-scale reconstruction. Based on the characteristics of a typical glutenite reservoir in China, the propagating mechanism of hydraulic fractures is investigated by using numerical method. Numerical simulation results show that the hydraulic fracturing is more complex due to the existing of gravels and there are four fracturing modes: terminations, deflections, penetrations and attractions. The primary fractures are strictly dependent on the difference of the maximum and minimum stress. With the increasing of principal stress difference, fractures are selected to cut through gravels rather than propagate around gravels. Consequently the propagation of primary fractures appears discrepancy and a lower breakdown pressure is needed. The higher the gravel volume content is, the worse the heterogeneity is. With the increasing of gravel volume content, the interaction between gravels and fractures is more evident. The higher gravel volume content needs a higher breakdown pressure. For the cases with a constant gravel volume content, the fracture initiation is mainly influenced by the stochastic distributing of gravels, consequently a gently higher breakdown pressure is required for the larger gravels.

Key words: glutenite, hydraulic fracturing, numerical simulation, propagation process, fracture