Experimental and numerical studies of non-equilibrium solvent exsolution behavior and foamy oil stability under quiescent and convective conditions in a visualized porous media

摘要

Non-equilibrium solvent exsolution and foamy oil stability in a visualized porous-media have been investigated. Two flow conditions were applied, namely, Static Constant Composition Expansion (SCCE) and Continuously Convective Flowing (CCF) schemes. The two schemes were aimed to study foamy oil non-equilibrium phase behavior deviating from the vapor-liquid-equilibrium under quiescent and convective condition, respectively. Two SCCE schemes, by both continuous and step-wise pressure depletion, were conducted. The non-equilibrium vapor phase volume ratio of the system was recorded, quantified and compared with the equilibrium state. Certain percentages from 5 to 35% of vapor-phase-ratio deviation from the equilibrium state were consistently found at multiple differentials from live oil saturation pressure. CCF tests up to 20 differentials from live oil saturation pressure were conducted to study non-equilibrium exsolution behavior under convection. Vapor phase volume ratio in CCF tests was always found to be 5-40% lower than that of the SCCE tests at the same operating pressure. Numerically, a MATLAB optimization module was developed to couple with CMG STARS reservoir simulator to study the non-equilibrium solvent exsolution behavior. Pseudo-chemical reaction kinetics representing non-equilibrium interphase mass transfer were applied. Gassy-liquid (compressible dispersed phase in a pseudo-single phase flow) and non-gassy-liquid (two-phase flow) schemes were implemented to history match the vapor phase volume ratio. The simulation results verified the phase-volume-ratio deviation from the equilibrium state in both SCCE and CCF schemes. Consistent to the experimental findings, the optimized kinetic reaction rate frequency factors indicated higher foamy oil stability under convective condition than that of quiescent condition.