Improving oil recovery in the CO2 flooding process by utilizing nonpolar chemical modifiers

Abstract

By means of experiments of CO2 miscibility with crude oil, four nonpolar chemicals were evaluated in order to enhance the miscibility of CO2 with crude oil. Through pre-slug injection and joint injection of toluene in CO2, crude oil displacement experiments in the slim-tube were conducted to investigate effects of the toluene-enhanced CO2 flooding under simulated subterranean reservoir conditions. Experimental results showed that toluene can enhance extraction of oil into CO2 and dissolution of CO2 into oil with the increment of 251% and 64% respectively. Addition of toluene can obviously improve the oil recovery in either pre-slug injection or joint injection, and the crude oil recovery increased with the increase of the toluene concentration. The oil recovery can increase by 22.5% in pre-slug injection with the high toluene concentration. Pre-slug injection was recommended because it can consume less toluene than joint injection. This work could be useful to development and application of the CO2 flooding in the oil recovery as well as CO2 emission reduction.