Acta Physico-Chimica Sinica ›› 2020, Vol. 36 ›› Issue (10): 1907034.

Special Issue: Frontiers in Colloid and Interface Chemistry

• Article •

### Polyesters-based Oil-CO2 Amphiphiles: Design and Miscible Promoting Ability

Peilong Liao1, Zeyu Liu1, Kaerdun Liu1, Cheng Ma1, Zhiyang Zhu1, Siyu Yang2, Wenfeng Lü2, Yongzhi Yang2, Jianbin Huang1,*()

1. 1 College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
2 Research Institute of Petroleum Exploration and Development (CNPC), State Key Laboratory of Enhanced Oil Recovery, Beijing 100083, P. R. China
• Received:2019-07-10 Published:2020-06-11
• Contact: Jianbin Huang E-mail:JBHuang@pku.edu.cn
• Supported by:
the National Oil and Gas Major Project of China(2016ZX05016-001)

Abstract:

Miscibility between oil and supercritical carbon dioxide (scCO2) phases has attracted significant attention in the field of oil recovery because it can be utilized in miscible gas displacement of oil, achieving nearly 100% recovery efficiency. The high recovery efficiency of miscible CO2 flooding originates from the valuable heavy components of oil and CO2 gas phase forming a homogenous phase with high mobility in the oil-scCO2 miscible system. However, the high pressure required for oil-scCO2 miscibility is a nontrivial obstacle for practical applications of scCO2 flooding recovery. Therefore, it is important to develop assist-miscible agents to lower the necessary miscibility pressure. In oil and water systems, well-developed amphiphiles (such as surfactants) have shown great promise for reducing the interfacial tension and maintaining the stability of the emulsion system. Therefore, "oil-CO2 amphiphiles" that can assist the miscibility between oil and scCO2 have been proposed. Among potential oil-scCO2 amphiphiles, a series of polyester-based oil-CO2 amphiphiles with esters as the CO2-philic groups and long carbon chains as the oil-philic groups were prepared. The polyester-based oil-CO2 amphiphiles, acting as assist-miscible agents, showed great ability to lower the needed miscibility pressure. A visualized miscible method was used to examine the efficiency of the assist-miscible agents with white oil and kerosene as the oil phase. The height of the oil phase inside the chamber was measured through a glass window to monitor the miscibility with increasing CO2 pressure. When the height of the oil reached the top of chamber, the oil filled the entire space, indicating miscibility. Using this method, the following conclusions could be drawn: First, amphiphiles with more ester groups exhibited stronger CO2-philicity, providing stronger ability to dissolve carbon dioxide. Second, amphiphiles with hydrocarbon chain lengths of 16 carbons exhibited the optimal assist-miscible efficiency. Third, greater differences between the oil and scCO2 phase showed more obvious differentiation among amphiphiles, showing the leveling and differentiating effect of oil. The temperature range of 50–80 ℃ did not influence the assist-miscible efficiency of the polyester-based amphiphiles. The best miscibility-assisting performance was obtained with CAA8-X, which contains eight ester groups and a palmitic acid chain. CAA8-X at a concentration of 1% (w, mass fraction) lowered the miscibility pressure in the white oil-scCO2 system by 16.04%. Amphiphiles with polyether (PEO) groups also showed excellent assist-miscible efficiency. The findings presented herein extend the concept of "amphiphilicity" from oil-water phases to oil-scCO2 phases and have the potential to guide future studies regarding scCO2 flooding in actual CO2 flooding oil recovery. Moreover, for other two-phase systems, according to the general amphipathic law and particular system parameters, it should be possible to design the optimal "amphiphiles".

MSC2000:

• O648