CO₂/Water Emulsions Stabilized By Nanoparticles And Surfactants

With the development of the economy,the domestic demand of petroleum resources is increasing day by day.However,the reserves of conventional oil reservoirs are limited.Therefore,the exploitation of unconventional oil reservoirs is a key breakthrough to increase our country’s oil production.The construction of CO2/water(C/W)emulsion is a win-win solution to enhance oil recovery and to reduce CO2 emission as well.But the emulsion is thermodynamically unstable,and it is prone to get into the situation of demulsification and stratification.Therefore,improving the stability of C/W emulsion is very important for emulsion flooding.In this work,several kinds of nanoparticles and cationic surfactant dodecyl trimethyl ammonium bromide(DTAB)were used to construct C/W emulsions.And through the characterization of interfacial tension,Zeta potential and particle size,the effects of interaction between the components on the stability of emulsion were explored.The research results showed that the synergistic effect of nanoparticles SiO2 and DTAB can effectively improve the stability of C/W emulsion.When the concentration ratio of DTAB/SiO2 was 1.3,the emulsion reached the most stable state.As the concentration ratio continued to increase,the stabilization decreased and then remained a certain value.In the construction of C/W emulsion,the nanoparticles SiO2 could construct a three-dimensional viscoelastic particle network to improve the stability of the emulsion.Then,the stability of C/W emulsion constructed by nanoparticles SiO2,TiO2,and Al2O3 were also studied,and found that the synergy of nanoparticles SiO2 and DTAB showed the best stabilization ability,followed by nanoparticles TiO2 and Al2O3.And it turned out that when the concentration ratio of DTAB/SiO2 is 1.3,DTAB/TiO2 is 4 and DTAB/Al2O3 is 10,the stability of C/W emulsion was best,In addition,the aggregation structure of asphaltene molecules in C/W emulsion was studied by molecular dynamics simulation,and there were three different configurations of the asphaltene aggregation.Also,the aggregation was more intensive with increasing temperature.By adding some interface active components to the system,we found that the aggregation of asphaltene molecules could be effectively slowed down.