醚类助溶剂在超临界二氧化碳中的浊点压力及对二氧化碳-C₁₆混相压力的影响

Cloud-point Pressure of Ether Cosolvents in Supercritical CO₂ and Their Effect on Miscibility Pressure of CO₂ -C₁₆

张 欢 宫厚健 孙君腾 张明明 吕 威 杨小珂

ZHANG Huan GONG Houjian SUN Junteng ZHANG Mingming LYU Wei YANG Xiaoke

助溶剂和CO2 对提高原油采收率有着协同增效作用。研究超临界CO2 -助溶剂体系的浊点压力和与原油的 混相压力，对于CO2 提高原油采收率及CO2 埋存有着重要意义。使用改进的CO2 相平衡实验装置，采用根据光敏 原理改进的测量方法，研究了3种助溶剂二乙二醇二甲醚（DDME）、三乙二醇二甲醚（TEDM）、四乙二醇二甲醚 （TGDE）在CO2 中的浊点压力，考察了温度、助溶剂加量、助溶剂类型的影响；然后将这3种醚类助溶剂和常见的 助溶剂乙醇对比，研究其降低CO2 -C16/sub> 混相压力的效果。结果表明，随着温度的升高，DDME、TEDM、TGDE的浊 点压力逐渐升高，且呈现出低临界会溶温度（LCST）相行为。随着加量的增大，DDME、TEDM、TGDE的浊点压 力逐渐升高，但增幅较小。DDME、TEDM、TGDE的极性越来越大，其与CO2 之间的分子间作用力逐渐减弱，导致浊点压力依次升高。在3种结构相似的醚类助溶剂中，DDME的浊点压力最低，TGDE的浊点压力最高。当 DDME的质量分数为3.0%、温度为60℃时，浊点压力仅为10.14MPa。DDME降低CO2 -C16 混相压力的效果最 好，在50℃时，1.0%DDME可使混相压力的降幅达到11.25%，高于乙醇的10.62%。在温度低于50℃时，TEDM 的作用效果优于乙醇，但高温下乙醇效果略优于TEDM和TGDE。DDME具有较低的浊点压力和较好的降低混 相压力的能力，与CO2 具有较好的配伍性，也适用于地层压力较低的油藏。

Carbon dioxide and cosolvents have synergistic effect on enhancing oil recovery. Measuring the cloud-point pressure and miscibility pressure is of great significance to improve oil recovery and CO2 sequestration. Based on the photosensitive principle， the cloud-point pressure of diethylene glycol dimethyl ether（DDME），triethylene glycol dimethyl ether（TEDM）and tetraethylene glycol dimethyl ether（TGDE）in CO2 and the effects of temperature，concentration and type of the cosolvents were obtained using the improved carbon dioxide phase equilibrium experimental device. Then the effects of cosolvents on decreasing the miscibility pressure of CO2 -C16 were investigated and compared with that of ethanol. The results showed that the cloud-point pressure of DDME，TEDM and TGDE all increased with the increase of temperature，and then the phase behavior of low critical solution temperature（LCST）was present. With the increase of cosolvent dosage，the cloud-point pressure of DDME，TEDM and TGDE all increased with a low increasing rate. Because the polarity became larger and larger in the order of DDME，TEDM and TGDE，the interaction force between cosolvent and CO2 became weaker and weaker，leading to the increase of cloud-point pressure. Among the three ether cosolvents with similar structure，DDME had the lowest cloud-point pressure，while TGDE had the highest cloud-point pressure. When the mass fraction of DDME was 3.0%，the cloud-point pressure was only10.14 MPa at 60 ℃. Moreover，DDME had the best effect to decrease the miscibility pressure between CO2 and C16 . DDME with the dosage of 1% could decrease the miscibility pressure with the decreasing degree of 11.25%，which was larger than that of ethanol（10.62%）at 50 ℃. When the temperature was lower than 50 ℃，the effect of TEDM was better than that of ethanol. At a higher temperature，the effect of ethanol was slightly better than that of TEDM and TGDE. DDME，with a low cloud-point pressure value，a high ability to decrease the miscibility pressure，and a good compatibility with carbon dioxide，was also suitable for the application in the reservoir with low formation pressure.

10.19346/j.cnki.1000-4092.2024.01.011