Study On The Interfacial Tension Of CO₂-hydrocarbons Systems For CO₂ Enhanced Oil Recovery

CO₂ capture,transport,utilization and storage(CCUS)is a cutting-edge technology for mitigating global climate change.CO₂ Enhanced Oil recovery(CO₂-EOR)is one of the important means to seal CO₂ while enhancing Oil recovery.The interfacial properties of components can be changed when CO₂ is dissolved in crude oil.Therefore,the interfacial tension(IFT)data of CO₂-hydrocarbons in crude oil system are important basic data of CO₂ oil extraction technology.At present,there are plenty of experimental interfacial tension data of CO₂-n-alkanes system.But the experimental interfacial tension data of CO₂-cycloalkanes/aromatic hydrocarbons system are not sufficient yet and cannot meet the requirements of CO₂-EOR.Therefore,it is of great significance for the development of CO₂-EOR technology to study on the interfacial tension data of CO₂-cycloalkanes/aromatics.In this work,the experimental equipment for measuring surface tension by pendant drop method at high temperature and high pressure was used.The equipment was designed and set up by the research group.The interfacial tension data of CO₂-(n-C11)system at 80?were measured by the equipment.The experimental data were evaluated and the experimental equipment was proved validity.262 groups of the interfacial tension values of CO₂-cycloalkane/aromatics binary systems were determined by this device.A large number of interfacial tension experimental data of binary CO₂-hydrocarbon systems were collected from the literature,including 611sets of CO₂-(n-alkanes),40 sets of CO₂-cycloalkanes and 19 sets of CO₂-aromatics.The interfacial tension values were analyzed and correlated as a function of temperature,pressure,carbon atom number,acentric factor and critical temperature.The correlation coefficient(R²)was 0.962,the root mean square error(RMSE)and the mean relative deviation(AARD)were 1.08 and 10.6%,respectively.In addition,166 sets of the interfacial tension data of CO₂-(n-hexane+cyclohexane)and CO₂-(n-hexane+toluene)ternary systems were also measured.The ternary interfacial tension data can be correlated as a simple linear summability model of the interfacial tension data of the relevant binary systems.The calculated results are good,with R² of 0.991 RMSE and AARD being 0.440 and 6.84%,respectively.Finally,the linear gradient theory is combined with the PR equation of state was used to calculate the interfacial tension values of the six binary systems for CO₂-cyclopentane/cyclohexane/cyclooctane/toluene/ethylbenzene/ethylcyclohexane.The AARD were 6.89%,10.5%,10.4%,8.46%,12.0%,and 11.6%,respectively.All the interface tension data and the models of CO₂-hydrocarbon systems provided in this study are important support for CO₂-EOR technology.