A novel and pragmatic technique has been proposed to quantify the non-equilibrium phase behaviour together with physical properties of foamy oil under reservoir conditions. Experimentally, constant-composition expansion (CCE) experiments at various constant pressure decline rates are conducted to examine the non-equilibrium phase behaviour of solvent-CO2-heavy oil systems. Theoretically, the amount of evolved gas is firstly formulated as a function of time, and then incorporated into the real gas equation to quantify the non-equilibrium phase behaviour of the aforementioned systems. Meanwhile, theoretical models have been developed to determine the time-dependent compressibility and density of foamy oil. Good agreements between the experimentally measured volume-pressure profiles and calculated ones have been achieved, while both amounts of evolved gas and entrained gas as well as compressibility and density of foamy oil were determined. The time-dependent effects of entrained gas on physical properties of oleic phase were quantitatively analyzed and evaluated. A larger pressure decline rate and a lower temperature are found to result in a lower pseudo-bubblepoint pressure and a higher expansion rate of the evolved gas volume in the solvent-CO2-heavy oil systems. Apparent critical supersaturation pressure increases with either an increase in pressure decline rate or a decrease in system temperature. Physical properties of the oleic phase under non-equilibrium conditions follow the same trends as those of conventionally undersaturated oil under equilibrium conditions when pressure is higher than the pseudo-bubblepoint pressure. However, there is an abrupt increase of compressibility and decrease of density associated with pseudo-bubblepoint pressure instead of bubblepoint pressure due to the initialization of gas bubble growth. The amount of dispersed gas in the oleic phase is found to impose a dominant impact on physical properties of the foamy oil. Compared with CCE experiment at constant volume expansion rate, a rebound pressure and its corresponding effects on physical properties cannot be observed in the CCE experiments at constant pressure decline rate.
Synthesis of Metastable or Non-Equilibrium Phased Oxides and Their Physical Properties
