Effect of temperature on crude oil extraction by SC-CO₂ at 40–70 °C and 40–60 MPa

The extraction process of crude oil by supercritical CO₂ was simulated in a high pressure extractor at 40, 50, 60 and 70 °C, and at 20, 40 and 60 MPa in order to investigate the effect of temperature on oil recovery. The total recovery of oil increased by 30–40% at the pressure increase from 20 MPa to 60 MPa. The temperature effect on the total recovery at 40, 50 and 60 °C was insignificant while the total recovery increased by 10% as the temperature rose from 40 °C to 70 °C. The vapor recovery did not change substantially with the temperature and pressure increase at temperatures higher than 40 °C. The isotherms of liquid recovery formed a concave surface because of higher extraction results at 40 °C and 70 °C indicating a crossover pressure phenomenon. The fingerprints of the extracted oil fractions obtained by GC–MS chromatography at various pressures and temperatures exhibited a variety of shapes. A correlation was obtained between liquid oil recovery and sums of selective specific single carbon number groups. Lighter hydrocarbons of C₇-C₁₀ group were representative at 20 MPa, intermediate hydrocarbons of C₁₅-C₁₉ group at 40 MPa, and heavier hydrocarbons of C₂₃-C₃₁ group at 60 MPa.