Experimental and numerical simulation of gas injection for enhanced oil recovery in naturally fractured condensate gas reservoirsOA

Gas condensate reservoirs constitute important natural gas resources;however,their development is frequently hindered by condensate banking and complex multiphase flow behavior.Naturally fractured gas condensate reservoirs present additional challenges because their dualporosity and dual-permeability structure induces strong phase redistribution and nonuniform flow between matrix and fracture systems,thereby complicating reservoir characterization and compositional simulation.In this study,integrated laboratory experiments and numerical simulations were performed for a deep,rich,naturally fractured gas condensate reservoir.Depletion,diffusion,and core flooding experiments involving CO_(2),N_(2),and dry gas injection were conducted using fractured core samples.A dual-porosity and dual-permeability compositional model incorporating a five-spot well pattern was established to evaluate condensate liquid recovery and to quantify mass transfer between matrix and fracture networks.The effect of matrix-fracture permeability contrast on production performance was systematically analyzed.The results indicate that matrix permeability is a primary parameter controlling recovery in gas condensate reservoirs.The ratio of matrix-fracture permeability contrasts exerts a stronger influence on condensate liquid recovery than on natural gas recovery.Pressure maintenance through gas injection is critical for improving recovery performance.When reservoir pressure declines below the dew-point pressure,early gas injection is recommended to mitigate condensate accumulation in the near-well region.Among the injected gases evaluated,CO_(2) demonstrated superior pressure maintenance performance compared with N_(2) and dry gas.