Numerical and Experimental Simulation of Hydraulic Fracture Propagation Mechanism in Conglomerate Formation Based on Hybrid Finite-Discrete Element Method

Abstract

Hydraulic fracturing was the main technology to achieve the economic development of conglomerate reservoirs, knowing that the hydraulic fracture propagation mode was of great significance for improving the development of conglomerate reservoirs. This paper proposed a new method to understand the hydraulic fracture behavior based on a hybrid finite-discrete element method. The simulation indicated that a complex fracture network was created near the wellbore in the studied conglomerate reservoir, and hydraulic fracture propagation around the gravel layer was the main failure mode when the hydraulic fracture reached the gravel layer. From the simulations, it was shown that under small differences in horizontal stress and tensile strength, the hydraulic fracture propagated more easily around the gravel layer, while it could cross the gravel under large differences in horizontal stress and tensile strength. Greater tensile strength differences can reduce the complexity of the fracture network. In addition, higher pumping rates and viscosities of fracturing fluid contribute to the complex fracture network and also can produce more gravel crosses when the hydraulic fracture is met. The main reason was that a higher pumping rate and higher viscosity of fracturing fluid can obtain a higher net pressure, which can ensure the hydraulic fracture crosses the gravel layer.