Design And Preparation Of Surfactants For CO₂EOR

The main problem of CO2flooding in China is the difficulty to achieve the miscibleflooding under reservoir conditions. By injection of light hydrocarbon in actualmining process, oil recovery could be enhanced slightly, but the corresponding cost isunacceptable because of the huge slug. In this paper, in order to get satisfactory oilrevovery, we systemically analyzed the principle of the processs of CO2flooding anddesighed a way to reduce the interfacial tension of CO2/oil by addition of CO2/oilsurfactant to the slug. We made up and optimized five surfactant molecules of twospecies, four of them fluorine-containing and one hydrocarbon. Furthermore,combining molecular dynamics and dissipative particle dynamics, we developed amethod to simulate the particle distribution of different molecules(including CO2, oiland surfactant) under multiple conditions of temperature and pressure, and bycalculating the order parameter we could speculate the MMP. Comparing the phasestate of CO2/fluorine surfactant/oil system and CO2/acetyl glucose ester/oil system,we found that OAc group is quite competitive with fluorine atom in CO2affinity.After that we synthesized the target molecules and the relative interfacial tension testsindicated that BC6F4was the most CO2-philic. Both theoretical and experimentalevidence showed that the molecule structure of CO2/oil surfactants influenced thephase state greatly, and one should analyze specific component of oil in practicalconcern.