The Preparation And Performance Evaluation Of Low Interfacial Tension Carbon Dioxide Foam System

For prolonged water flooding and polymer flooding development in Daqing Oilfield,there is so many channeling-paths and low and non-effective circulation layers is one of important challenges of high efficient oilfield development.How to effectively plug large pore path,and displace the residual oil at small pore,has become one of the problems to be settled urgently for matured oilfield.So the low interfacial tension CO₂foam system was studied for the purpose of enhancing oil recovery in oil reservoirs with big channel,which can expand spreading volume and improve displacement efficiency.On the other hand,it is a win-win method for both economic and environmental benefits because it may not only storage CO₂ underground but also improve oil recovery.In this paper,CO₂-EOR and carbon dioxide sequestration of Daqing oil fields was evaluated firstly.According to the characteristics of target reservoir,the surfactant mixture was developed as foaming agent.Based on the investigation of the influences of different polymers for foam system’s properties,the foam stabilizer was determined to further enhance foam stability.And then,the optimal formulation of the foam system was determined.Finally,the performance evaluation,such as ageing resistance,salt tolerance and foam on high temperature and pressure,was carried out for the optimal foam system.The evaluation results of CO₂-EOR and carbon dioxide sequestration in Daqing oil fields show that the EOR potential is 326.94Mt,and the CO₂ storage potential is807.22Mt.And then,the research results shows that both SDS/DHPB and SDS/DHPB/CTAB combined systems have significant synergistic effect.The rheometer is applied to measure the rheology behavior of polymer solution and viscoelasticity of foam to select foam agent.By studying the effect of different compound proportion and foam agent on performance of foam combination system,The formula of foam flooding system was determined as follow:4000mg/L（SDS/DHPB=1:1.5）+500mg/LXC and4000mg/L（SDS/DHPB=1:1）+300mg/LCTAB+500mg/LXC,both of which have good foaming performance and interfacial activities with 10^-3mN/m.Experimental evaluation of indoor basic properties shows that they have good anti-aging performance and stable foaming performance under 20000mg/L of NaCl and 500mg/L of CaC1₂.Foam stability evaluation on high temperature and pressure have verified that both low temperature and high pressure are in favor of foam stability.This study provides references and bases for further improving oil recovery of Daqing and other matured oilfields.