Zheng Zhang, Zhongtao Yuan, Nianjie Kuang, Mengyu Wang, Jianbang Wu, Wenfeng Lv, Meng Wang, Yuxiang Zhang, Shenglai Yang, Shuai Li, and Xisheng Zhang
In order to cope with the global climate crisis, carbon capture, utilization, and storage are the key technologies to achieve carbon neutrality, and it is an elegant geological utilization method for the oil and gas industry to improve the recovery rate of crude oil by using CO2. However, in practical applications, the problem of low miscibility of CO2 and crude oil, resulting in low oil displacement efficiency, cannot be avoided. Thus, finding an appropriate method to increase the utilization rate of CO2 is a worth in-depth study. In light of this, this paper carries out the study on improving the CO2 flooding efficiency by using oil and gas amphiphilic surfactants. First of all, according to the molecular structure theory and the solubility experiment of surfactants in CO2, five kinds of surfactants and two kinds of additives with good performance of oil and gas were selected. Then, three experiments were conducted to explore the mechanism of the selected surfactants. The main mechanism of promoting the miscibility of CO2–crude oil is to reduce the interfacial tension of the oil and gas phases, followed by increasing the volume expansion of crude oil and reducing the viscosity of crude oil. Finally, through the slim tube displacement experiment, the oil displacement efficiency effect of adding the compound systems of SPO5/n-pentanol was simulated. The results show that the oil displacement efficiency is significantly higher than that of pure CO2 flooding, and the pressure of miscibility reduces at the same time. The selected reagents have a good effect of promoting miscibility. Therefore, this is an effective method to improve the geological utilization of CO2.