Numerical Simulation of Fractured Wells in Low-Permeability Oil Reservoirs and Study on Remaining Oil Distribution: A Case Study of the Nanpu 4-3 Oil Reservoir

The Nanpu 4-3 Oil Reservoir is a deep ultra-low permeability reservoir characterized by challenges such as low reserve recovery efficiency, rapid production decline, high water injection pressure, and limited production cycles. Following long-term waterflooding development, the complex distribution patterns of remaining oil have hindered precise residual oil exploitation and the formulation of development adjustment strategies. To address issues including intricate geological structures of ultra-low permeability reservoirs, significant threshold pressure gradients, and strong heterogeneity in artificial fracture networks, this study employs numerical simulation techniques coupled with threshold pressure gradient modeling to quantify the impact of seepage resistance on waterflooding efficiency under low-permeability conditions. Furthermore, through systematic studies integrating 3D dynamic characterization methods for artificial fracture networks—including refined reserve recalculation, grid optimization modeling, zonal fluid property constraints, hydraulic fracturing parameter inversion, dynamic production data verification, and history matching—the waterflooding characteristics and remaining oil enrichment patterns across different sublayers in both lateral and vertical dimensions were clarified. These findings provide theoretical support for optimizing injection-production parameters, iterating fracturing designs, and formulating comprehensive adjustment plans, offering critical guidance for the reservoir’s efficient development.