Numerical Simulation Study on Oil Displacement Processes Under Different Fracture Morphologies in Conglomerate Reservoirs

ABSTRACT: The conglomerate reservoir exhibits strong heterogeneity, and its pore-permeability conditions are complex due to the influence of gravel and cementation surfaces. The relationship between fracture morphology generated by hydraulic fracturing and oil displacement efficiency remains unclear. In this study, based on the fluid-solid coupling numerical simulation method, an artificial fracture network containing main fractures and branch fractures in the conglomerate reservoir was established, and the shut-in and displacement processes under specific fracture morphologies were investigated. The results demonstrate that the aqueous phase in the fracture system can spontaneously displace the crude oil in the pores after fracturing, and the displacement efficiency is significantly controlled by the fracture morphology. During the water flooding process, the crude oil exhibits a distinct selective flow characteristic, first flowing from the matrix pores into the fracture system and then being produced through the fracture network. This study clarifies the influence mechanism of fracture morphology on oil displacement efficiency, providing a theoretical basis for optimizing fracturing parameters, including selecting displacement media to reduce interfacial tension, optimizing pumping procedures to construct complex fracture networks, and rationally planning shut-in time. The research results have important guiding significance for reducing construction costs and improving oil recovery, and can provide scientific reference for on-site fracturing and production operations.