Abstract The minimum miscible pressure is one of the key factors to realize miscible flooding. As the minimum miscible pressure in the research area is higher than the formation fracture pressure, miscible flooding cannot be formed. To address this problem, it is necessary to find a way to reduce the minimum miscible pressure. Citric acid isopentyl ester can not only be dissolved in crude oil, but also be dissolved in carbon dioxide. Therefore, citric acid isopentyl ester was chosen to reduce the minimum miscible pressure in this research. The effect of citric acid isopentyl ester on reducing the minimum miscible pressure was measured by the method of long slim tube displacement experiment. The minimum miscible pressure in the research area was 29.6 MPa. The experimental results show that the minimum miscible pressure could decrease significantly with increasing the injected slug size of citric acid isopentyl ester, but the decrease became smaller and smaller. The optimum injected slug size of the chemical reagent is 0.003 PV. Under the condition of the slug size, the minimum miscible pressure was 24.1 MPa. The reduction was 5.5 MPa. The reduction rate was 18.58%. The research results have important guiding significance for enhancing oil recovery in the research area.

中文翻译：

---

降低原油与二氧化碳最小混相压力的研究及注入柠檬酸异戊酯的混相驱实验

摘要 最小混相压力是实现混相驱的关键因素之一。由于研究区最小混相压力高于地层破裂压力，不能形成混相驱。为了解决这个问题，需要找到一种降低最小混相压力的方法。柠檬酸异戊酯不仅能溶于原油，也能溶于二氧化碳。因此，本研究选择柠檬酸异戊酯来降低最小混相压力。采用长细管置换实验法测定柠檬酸异戊酯对降低最小混相压力的影响。研究区最小混相压力为29.6 MPa。实验结果表明，随着柠檬酸异戊酯注入段塞尺寸的增加，最小混相压力显着降低，但降低幅度越来越小。化学试剂的最佳注入段塞尺寸为 0.003 PV。在段塞尺寸条件下，最小混相压力为24.1 MPa。减少量为5.5 MPa。减少率为18.58%。研究成果对研究区提高采收率具有重要的指导意义。