Interfacial Tension Simulation Of CO₂-Monomer Hydrocarbon System

Carbon dioxide?CO₂?is usually used as a fluid reservoir to improve the oil recovery process.The interfacial characteristics of CO2-crude oil system are the basis for understanding CO₂ displacement.The essence of CO₂ injection includes three aspects:reduction of crude oil viscosity,the oil volume expansion and the change of the interfacial properties of crude oil system.Reliable interfacial tension data can be used to predict the minimum miscible pressure required for CO₂ miscible phase displacement.According to the group composition,alkanes,cyclones,aromatic hydrocarbon and colloid asphalt are the main compositions of crude oil.Systems of CO₂-n-alkane and CO₂-alkyl benzene were discussed in this work,and suitable interfacial tension model for CO₂-monomer hydrocarbon system was established in this work.The main contents of this work are as follows:?1?Establishing the interfacial model:The linear gradient theory?LGT?proposed by Zuo Youxiang was applied into this work to calculate the interfacial tension.Based on Fortran program,the constant of interfacial tension influence parameters was adjusted to improve the calculation accuracy of interfacial tension.?2?Calculating the gas liquid density by PT EOS:Based on the group contribution,CO₂ group was added to calculate the binary interaction parameters(k_ij)of CO₂-monomer hydrocarbon system.Volume correction C_i was fitting by the saturated liquid density data of eleven n-alkanes(C₁₀-C₂₀)and five n-alkyl benzenes(C₆-C₁₀).Therefore,the prediction of liquid density was adjusted to improve the accuracy of this model.?3?Calculating interfacial tension influence parameters c:Parameters?c_i?of pure substance were fitting by the interfacial tension data of pure alkane,pure n-alkyl benzene and pure CO₂.The appropriate mixing rule was used to calculate the influence parameters of mixture.The interfacial tension model applied the linear gradient theory was established to calculate interfacial tension of eleven binary systems?CO₂ and n-alkane?and ten binary systems?CO₂ and n-alkyl benzene?.The calculated results were in good agreement with experimental results.Obviously,this thesis verified the accuracy of the interfacial tension model.