Extraction and Its Effects on Crude Oil Properties During CO2 Flooding

Abstract

In this article, using the high-temperature and high-pressure pressure, volume, and temperature experimental equipment to simulate the CO2 extraction process of the crude oil, the effects of pressure and gas injection volume on extraction, and the extraction effects on oil properties were studied by measuring the CO2 volume extraction ratio as well as the composition and viscosity of the oil. The experimental results show that the CO2 extraction ratio increases with the increase of the pressure and the CO2 can enhance the oil recovery by 59.3% through the extraction under the pressure of 46 MPa. At the same pressure, the CO2 extraction ratio is 5–10 times as large as that of the hydrocarbon gas. The heavy component content and viscosity of both extracted oil and residual oil after the extraction increase as the pressure increases, meanwhile the extracted oil viscosity is smaller than that of the original oil, and the residual oil viscosity can reach 10 times as large as that of the original oil. Within the experiments, as the CO2 injection volume increases, the extraction ratio of the oil increases slightly, and the composition and viscosity of the extracted oil remains basically unchanged, but the heavy component content and viscosity of the residual oil increase greatly. The viscosity can reach 8.3 times as large as that of the original oil. Thus, it can be seen that when the CO2 injection volume is bigger than that of the oil, the increase of it has a very limited effect on the extraction ratio, but can make the residual oil viscosity increase greatly.