Investigation on the influences of gravel characteristics on the hydraulic fracture propagation in the conglomerate reservoirs

Abstract

To explore the influences of gravel characteristics on hydraulic fracture propagation in conglomerate formations, the real rock fracture process analysis software was used under specific stress conditions: including gravel particle size, gravel volume content, and gravel strength. Based on the numerical simulation results, the fracture propagation process under different conditions was investigated and the type and evolution of fractures were described. The results showed that larger gravel particle sizes led to stronger shielding and induction effects on the fractures. With the increasing gravel particle size, the propagation model of the fractures changes gradually from by passing gravel to passing through gravel or embedding in gravel particles. When the gravel particle sizes are constant, with increasing gravel volume content, the conglomerate reservoir becomes more heterogeneous and the fractures become more easily shielded and inducted by the gravel particles. Therefore, the fractures become more dispersed and the fracture propagation laws become more complex, which allows the formation of a hydraulic fracture network. The greater the difference in the ratio of the strength parameters of the gravel to the strength parameters of the matrix, the more strongly the fractures are blocked by the gravels and the propagation model of fractures changes from passing through gravel to by passing gravel.