Abstract: The cyclic carbon dioxide injection technology to improve heavy oil production after steam soak was studied by physical simulation. The mechanisms of cyclic carbon dioxide injection were investigated. The results show that injection of carbon dioxide into heavy oil reservoir in the late steam soak period can increase expansion energy and decrease oil viscosity and also demulsify the emulsion formed in the steam soak process. In general, carbon dioxide dissolved in the heavy oil can reduce oil-water surface tension and result in breakdown of emulsion. Also, the injected carbon dioxide can change oil-water relative permeability and lower the remaining oil saturation. The field pilot test shows that cyclic carbon dioxide injection after steam soak is successful in technology and has the economic benefits. Both physical simulation and pilot test show that cyclic carbon dioxide injection technology is economically feasible to improve the development results after multi-cycle steam soak for heavy oil reservoir.

Key words: heavy oil reservoir, physical modeling, steam soak, cyclic carbon dioxide injection technology, oil recovery mechanism, field test

摘要： 利用物理模拟技术,对蒸汽吞吐后期的稠油油藏转注CO₂吞吐技术以改善其开采效果的机理进行了研究,结果表明,蒸汽吞吐后期油藏转注CO₂吞吐开采:1增加了弹性驱能量;2CO₂溶解于稠油中,使原油粘度降低;3乳化液破乳:高轮次吞吐使原油物性变差,粘度大幅度增高;而CO₂溶解于稠油和水中降低了油水界面张力,使原油粘度大幅度下降;4油水相对渗透率曲线特征得到改善,残余油饱和度降低.实验研究及现场试验结果表明,稠油油藏蒸汽吞吐后期转注CO₂吞吐开采在技术上和经济上都是可行的.该技术改善了稠油油藏蒸汽吞吐后期的开发效果.

关键词: 稠油油藏, 物理模拟, 蒸汽吞吐, 二氧化碳吞吐技术, 油藏开采机理, 现场试验