Numerical Investigation of Hydraulic Fracture Propagation in Cemented Naturally Fractured Reservoirs

Cemented natural fractures are widely developed in unconventional reservoirs and play a key role in controlling hydraulic fracture propagation and fracture network evolution. However, their mechanical effects are often oversimplified in conventional numerical models, limiting the reliability of fracture prediction. A numerical framework was established to investigate hydraulic fracture propagation in reservoirs containing cemented natural fractures. Cementation effects are quantitatively characterized using two parameters—cementation degree (Cd) and cementation strength (Cs)—representing the filling condition and interfacial resistance of natural fractures. Based on this formulation, both single-fracture and multiple-fracture models are constructed to analyze the influence of cementation properties and fracture density on fracture propagation. The results show that Cd mainly controls fracture activation and propagation mode. Lower Cd promotes fracture diversion and branching, whereas higher Cd favors fracture penetration through the interface. Cs governs interfacial resistance, with higher Cs leading to more stable propagation. Increasing fracture density enhances fracture network complexity but also intensifies stress interference, affecting propagation stability and connectivity. These findings provide mechanistic insights into the role of cemented natural fractures in hydraulic fracturing and may support a more reliable interpretation of fracture propagation behavior in naturally fractured reservoirs.