缝洞型油藏气水驱替渗流规律实验研究OA

As a significant component of unconventional oil and gas resources,fractured-vuggy reservoirs are characterized by complex connectivity between fractures and cavities,as well as strong heterogeneity.These factors lead to elusive flow patterns and intricate mechanisms of residual oil formation during reservoir development.Using custom-designed artificial fractured-vuggy cores,this study revealed the influences of fracture occurrence,drainage pressure,and cavity filling on flow patterns during water and gas injection.Moreover,fluid distributions in fractures and cavities were systematically analyzed through visualization experiments,and variations of displacement efficiency were quantitatively described.Experimental results demonstrate that vertical fractures connected to cavities tend to form more residual oil,gravitational differentiation decreases the sweep range in fractures during water and gas injections,and horizontal fractures significantly enhance displacement efficiency.Drainage pressure has no effect on displacement efficiency;however,a single-phase flow was observed during low-pressure displacement,a two-phase oil-gas flow occurred during gas injection under high pressure.Furthermore,the efficiency of water displacement was notably higher than that of gas injection.The presence of cavities filled with particles decreases the water displacement efficiency due to the occurrence of complex flow pathways and two-phase flows.Visualization experiments further indicate that wider fracture openings,larger cavity diameters,and higher injection velocities hinder displacement front accumulation in the vertical direction.However,the displacement efficiencies in fractures and cavities increase significantly with higher oil viscosity.