Experimental study of CO2 solubility on the oil recovery enhancement of heavy oil reservoirs

The sufficient energy to transfer the crude oil to the surficial wellbore facilities would be reduced dramatically which was done by CO2, especially for heavy and super-heavy oil reservoirs. The objective of this comprehensive study is to measure the considerable influence of CO2 solubility on the recovery factor, density, viscosity at different pressures and temperatures. According to the results of this study, recovery factor at the pressure of 0.2 MPa and 0.5 MPa experienced the lowest recovery factor among other pressures. They were about 38.37% and 43.81% after the injection of about 15 pore volumes of CO2. For the pressures of 1 MPa, 2 MPa, 3 MPa, and 4 MPa, at the first stages of CO2 injection (up to 3 pore volumes of CO2 injection), the recovery factor experienced the same value. Since then, by the increase in pressure from 1 to 4 MPa, the recovery factor was increased slightly. Moreover, recovery factor at the temperature of 333 K was measured about 34.5%. The measured recovery factor for other temperatures was 40.17%, 47.68%, 51.97%, 58.42%, and 63.54% at the temperature of 363 K, 393 K, 423 K, 453 K, and 483 K, respectively. On the other hand, the density of heavy oil which was saturated with CO2 was decreased with the increase in pressure and temperature and the higher temperatures caused the lower effect on the viscosity and density of heavy oil. Consequently, the dissolution of CO2 had decreased the heavy oil viscosity in the higher temperatures and pressures, and due to the increase in pressure and temperature, the heavy oil recovery factor was increased. Furthermore, the recovery factor for the 70 mL min−1 of CO2 injection was lower than the 700 mL min−1 of CO2 injection.