Modeling of Hydraulic Fracture Propagation in Real Heterogeneous Conglomerates from the Mahu Oilfield using the Global Cohesive Zone Method

Hydraulic fracturing enhances production in unconventional reservoirs but is challenged by reservoir heterogeneity, which complicates fracture propagation and reduces the efficiency of conglomerate reservoir development. The Mahu area in Xinjiang, a major petroleum reservoir in western China, is rich in oil and gas but features highly heterogeneous geological structures that complicate hydraulic fracturing and hydrocarbon extraction. In this study, we analyzed both homogeneous and heterogeneous core samples from the Mahu area. Real pore structures and gravel compositions were obtained using Computed Tomography (CT) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN). The Global Pore-Pressure Cohesive Zone (GPPCZ) model was applied to study the impact of heterogeneity on fracture propagation, considering differences in the mechanical properties of the matrix, gravel, and interfaces. Results showed that fractures tend to propagate in regions with lower critical fracture energy. In heterogeneous cores, fractures were more likely to deflect around gravel and bifurcate, forming complex networks. Peak propagation velocity occurred at interface contacts, but homogeneous cores exhibited faster propagation under the same stress conditions. This work provides theoretical support for optimizing hydraulic fracturing strategies in heterogeneous conglomerate reservoirs such as the complex Mahu area.