Influence of fractures on injection for low-permeability sandstone reservoir in Taizhao area, Daqing Oilfield

Based on the investigation of fracture distribution characteristics, the influence of fractures on injection was analyzed in Taizhao area, Daqing Oilfield. The results show that four sets of structural fractures with high dip angle were developed in Putaohua low-permeability sandstone reservoir, whose orientations respectively were east-west, northwest-southeast, south-north and northeast-southwest. Fractures have little reservoir capacity but make main roles on seepage. Affected by factors such as present stress field, the starting pressures of above fractures on the wellhead respectively are 15.1, 19.6, 27.8 and 28.0 MPa, which show the different starting sequence of the fractures. Now, the injection pressures in the study area basically exceed the starting pressure of east-west fracture, and the reflection characteristics of injection are quite clear. According to seepage characteristics of different sets of fractures, it is available to improve development effect by adopting linear injection well pattern, dynamic adjustment injection, cyclic injection, intermittent injection between layers and intermittent pumping after high water cut wells shut-in, and making further consummation injection-production system.