Enhanced oil recovery mechanisms of active fluid high-pressure flooding in ultra-low permeability oil reservoirs
Active fluid high-pressure flooding refers to a technique of injection of active fluid slugs for enhanced oil recovery(EOR).In this study,the characteristics and EOR mechanisms of the active fluid high-pressure flooding were investigated by conducting a series of experiments combined with interface properties,electrical properties,and capillary number theory.The results indicate that,after water flooding,active fluid high-pressure flooding can increase oil recovery by 4.9%-13.4%,and reduce injection pressure by 17.6%-51.3%.The molecules of the active fluid can be adsorbed at the oil-water inter-face,which can reduce the interfacial tension,increase the stability of emulsified oil droplets,intensify the microscopic sweep efficiency,and improve oil recovery of ultra-low permeability cores.When the mass concentration of the active fluid is increased from 0.05%to 0.5%the injection flow rate can be increased from 0.5 mL/min to 3 mL/min,the capillary number can be increased by 2 orders of magnitude,and the residual oil saturation can be reduced up to 20.8%.Meanwhile,the ad-sorption of the active fluids on the pore surface can weaken the hydrophilicity of rock surface and reduce the flow friction of water phase.There is a proper injection rate range for the active fluid high-pressure flooding.Excessive or high injection rate can increase the inertial resistance of the displacement fluid flow and weaken the pressure reduction effect.A field pilot test shows that,with an active fluid slug injection,a daily oil increment of 0.4 t was achieved in a single well.
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维普
