Study On Surfactant-Carbonated Water Flooding To Enhance Oil Recovery In Ultra-Low Permeability Reservoirs

Aiming at the problems of low pressure level,low recovery rate and difficult exploitation in the development process of ultra-low permeability reservoirs in Ordos Basin,taking the ultra-low permeability reservoirs in Ordos Basin as the object,the physical displacement experiments and numerical simulation of Carbonized water,surfactant and Carbonized water-surfactant are carried out.The research results provide theoretical guidance for the reference of surfactant and Carbonized water in ultra-low permeability reservoirs in Ordos Basin,and have important guiding significance for the study of enhanced oil recovery in ultra-low permeability reservoirs in Ordos Basin.The experimental results show that:(1)The interfacial tension,emulsification performance,compatibility with formation water,viscosity and contact angle of three different surfactants were compared.The preferred surfactant solution was cetyl hydroxypropyl sulfobetaine(THSB)solution;the interfacial tension,emulsifying properties,viscosity and core damage properties of THSB solutions with different mass concentrations were compared.Considering the cost saving,the preferred THSB solution concentration was 0.3%.The test results of crude oil expansion performance,interfacial tension,crude oil viscosity reduction,wetting angle and core damage performance of carbonized water with different concentrations were compared.The preferred carbonized water concentration was 0.4mmol/cm~3.(2)After water flooding of 1.5PV,carbonized water flooding increased the recovery rate by 9.44%.After water flooding of 1.5PV,surfactant flooding increased the recovery rate by 9.43%.After the surfactant displacement of 1.5PV,the carbonized water flooding increased the recovery rate by 21.39%.After 1.5 PV of carbonized water flooding,the surfactant flooding increased the recovery rate by 13.41%.(3)According to the numerical simulation prediction results of 24 schemes,the optimal carbonized water injection concentration is 0.4mmol/cm~3,the carbonized water injection-production ratio is 1.2,and the surfactant injection mass fraction is 0.3%.The best surfactant injection volume is5m~3/d.After comparison,the experimental results are consistent with the numerical simulation results.