Pyrolysis of heavy oil in supercritical multi-thermal fluid: An effective recovery agent for heavy oils

The Supercritical Multithermal Fluid Flooding Investigation: Experiments and Numerical Simulation for Deep Offshore Heavy Oil Reservoirs

“…As can be seen in Figure 3, in contrast to steam flooding, the SCW flooding resulted in an 18.51% increase in oil recovery (Figure 3(a)). The better oil production performance of SCW flooding should be ascribed to the following reasons: (1) in comparison to steam flooding, the heat front of SCW was uniform (Figure 3(b)), and high pressure difference period was longer (Figure 3(c)), indicating that the override phenomenon of SCW flooding is weak, and (2) the heavy oil upgrading in SCW can substantially increase oil mobility in contrast of that in steam, as described in a previous study [24].…”

“…This should be ascribed to two reasons: first, during the flooding process, the dissolution of scN 2 and scCO 2 was enhanced at rising pressure, which could increase oil mobility. Second, the increase in injection pressure can intensify the upgrading of heavy oil in SCMTF [24]. Therefore, the light oil mole fraction was increased in the model (Figure 9(d)).…”

“…The previous research revealed that heavy oil upgrading played an important role in oil production during SCMTF injection [24]. According to the oil property tests, product distribution, and gas product analysis presented by Sun et al [24], the following chemical reaction equa-…”

“…Moreover, the history-matched model was adopted to predict the SCW flooding process, and the experimental and simulation results shown in Figure 6 demonstrate a fair match (average errors of oil recovery is 3.83% and of pressure difference is 6.37%), further confirming the accuracy of the developed model. By the fact that the SCW dominate the heavy oil upgrading in SCMTF [24], only the heavy oil near the inlet underwent upgrading process, contributing to the aforementioned phenomena. In addition, scN 2 and scCO 2 promote more rapidly than SCW (Figure 7(c)), and the shape of low-viscosity area (Figure 7(c)) was similar to the gas distribution.…”

“…The increase in injection temperature could enhance the heat transmission, resulting in a decrease in viscosity. In addition, the increase in injection temperature could considerably intensify the heavy oil upgrading in SCMTF [24]. Therefore, the light oil mole fraction increased (Figure 8(d)), leading to a further decrease in oil viscosity.…”