Reducing the minimum miscibility pressure of CO2 and crude oil using alcohols

The establishment of a miscible phase between CO2 and crude oil can significantly improve CO2 flooding efficiency. However, the minimum miscibility pressure (MMP) between CO2 and crude oil is usually higher than the fracture pressure of the formation, how to reduce the MMP between CO2 and crude oil is very important, and there are fewer related studies. Our inspiration for reducing MMP comes from the unique dispersion characteristics of CO2 in alcohol, the intermolecular force of crude oil may decrease due to the existence of alcohols. In this paper, the CO2 solubility and the oil volume expansion with adding a variety of alcohols (1-butanol, 1-pentanol and 1-hexanol) were measured by a visible high temperature and high pressure cell from 7 MPa to 20 MPa at 343.15 K. The MMP between CO2 and crude oil is predicted by measuring the interfacial tension (IFT) between CO2 and crude oil from 2 MPa to 43.3 MPa at 343.15 K. The results showed that the CO2 solubility in crude oil and the oil volume expansion were greatly improved due to the addition of alcohols. Especially 1-butanol, 1-pentanol and 1-hexanol were mixed by 8:1:1(volume ratio), 5% (volume ratio) alcohols mixture was added to the crude oil, the CO2 solubility in crude oil increased by 28.74% at 345.15 K and 19 MPa, and the volume expansion coefficient of crude oil also increased by 4.45% at 345.15 K and 14 MPa. It is encouraging to note that the MMP between CO2 and crude oil decreases by 9.21% after adding 5% alcohols mixture into crude oil. This article is able to provide a new technique for reducing the MMP between CO2 and crude oil in the field of enhanced oil recovery.