Study of Horizontal Fracture Network Formation Mechanism of Shallow Layer Reservoir

Yanchang Oil Field C6 oil layer has shallow burial depth (500-600m), compact reservoir, and natural fracture development with high rock brittleness, containing the condition of forming complex horizontal fracture network. However, as the formation mechanism of horizontal fracture network is unclear, the oil field development has experienced serious restriction. Based on continuous damage mechanics method, this thesis applied secondary development on user subroutine of AQAQUS, established numerical simulation model for simultaneous propagation of hydraulic fracture and natural fracture, simulated and analyzed the horizontal fracture network form and its formation condition of C6 Reservoir. Through numerical simulation, it is found that the main conditions of forming the fracture network includes: less stress difference, high-density natural fracture, high-angle natural fracture, cluster interval of around 30m, large discharge capacity 􁈺>12m³ /min), and low-viscosity slick hydraulic fracturing fluid. The study conducted in this thesis can provide guidance on horizontal fracturing network of similar shallow layer reservoir.