Interfacial Interactions Of High-Pressure CO₂/Surfactant Solution/Fengcheng Heavy Oil System

In the process of surfactant solution-alternating CO2 gas injection(SAG),CO2 gas-water phase-oil phase are present in the system.The interfacial tension(IFT)between two phase has a significant impact on the flow pattern of fluid.In order to investigate the interfacial interactions in the system of Fengcheng heavy oil/surfactant solution/high-pressure CO2,the axisymmetric drop shape analysis(ADSA)technique was adapted to measure the IFT between CO2 and Fengcheng heavy oil at 50 ? and in the pressure range of(1.00-10.00)MPa.The IFT between Fengcheng heavy oil and surfactant solution with the presence of CO2 at 30? and 50 ? and in the pressure range of(0.10-10.00)MPa was measured.The emulsion performance of Fengcheng heavy oil was investigated too.The mechanism of displacing Xinjiang mixed crude oil by surfactant solution was studied through the microscopic visualization experiment apparatus.The results indicated that in the CO2/Fengcheng heavy oil system,when pressure lower than 3.00 MPa,CO2 made Fengcheng heavy oil swell.When pressure higher than 3.00 MPa,CO2 could extract the light component and led to the shrinkage of Fengcheng heavy oil.In the Fengcheng heavy oil/surfactant solution/CO2 system,IFT between Fengcheng heavy oil and surfactant solution was increased with the pressure increased.It was found that high-pressure CO2 can significantly reduce the IFT of pure water/Fengcheng heavy oil and sodium dodecyl sulfonate(SDS)solution/Fengcheng heavy oil.However,high-pressure CO2 increased IFT for the dodecyl trimethyl ammonium chloride(DTAC)solution/Fengcheng heavy oil system and decyl trimethyl ammonium bromide(DeTAB)solution/Fengcheng heavy oil system.It was also observed that the dissolution of CO2 into SDS solution improved the emulsifying power of SDS.However,the dissolution of CO2 into DTAC solution reduced emulsifying ability of DTAC.Pore-level experimental investigation of surfactant flooding showed that,the primary mechanism for DTAC solution to enhance Xinjiang mixed crude oil recovery was that DTAC should reduce the IFT between Xinjiang mixed crude oil and water and emulsify Xinjiang mixed crude oil.