Non-Equilibrium CO2-Oil Interactions for Enhanced Oil Recovery

فاقد چكيده فارسي

In this study, we use a custom-designed visual cell to investigate non-equilibrium CO2-oil interactions under high-pressure and high-temperature conditions. We visualize the CO2-oil interface and measure visual cell’s pressure over time. We perform 5 sets of visualization test. The first three tests aim at investigating interactions of gaseous (g), liquid (l), and supercritical (sc) CO2 with the black reservoir oil. In the fourth test, in order to visualize the interactions at the bulk oil phase, we replace the opaque black oil with a translucent light oil (LO). Finally, we conduct N2(sc)-oil test to compare the results with those of CO2(sc)-oil tests. Results of the first three tests show that oil immediately expands upon injection of CO2 into the visual cell. CO2(sc) leads to the maximum oil expansion followed by CO2(l) and CO2(g). Furthermore, the rate of oil expansion in CO2(sc)-oil test is higher than that in CO2(l)-oil and CO2(g)-oil tests. We also observe extracting and condensing flows at the CO2(l)-oil and CO2(sc)-oil interfaces. Moreover, we observe density-driven fingers inside the LO phase due to the local increase in the density of LO. We do not observe neither extracting/condensing flows nor density-driven natural convection for N2(sc)-oil, explaining low expansion of oil in this test. The results suggest that the combination of density-driven natural convection as well as extracting/condensing flows enhance CO2(sc) dissolution into the oil phase, leading to fast oil expansion after CO2(sc) injection into the visual cell.