Coupling of Modified Equation of State and Percolation Theory to Study Static and Dynamic Non-Equilibrium Phase Behavior of Heavy Oil in the Presence of Porous Medium

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Non-equilibrium thermodynamic phase behavior normally exists for high viscous crude oil during the primary depletion process. Previously, phase behavior studies for heavy oil were generated in the bulk phase; however, it cannot represent a similar situation in the presence of porous medium, which creates cause for concern as to the accuracy of the information. In this research study a systematic and comparative workflow is proposed to combine experimental and numerical approaches to the study of the static and dynamic non-equilibrium phase behavior of live heavy oil in the porous medium. For the experimental part, the high temperature and high pressure phase tests will be performed for heavy oil systems in a sand-pack filled physical model connected to a visual pressure cell, and the self-designed and manufactured micromodel. The injected recombined live oil will go through the pressure depletion processes, and the fluid phase non-equilibrium and equilibrium will be controlled by varying the depressurization rate. At each pressure, the total fluid volume, evolved gas phase, and the interfacial properties such as interfacial tension and interfacial area, capillary pressure, etc. will be determined and analyzed directly or indirectly. The sand-pack model will be scanned by using an ultrasonic apparatus to determine the fluid phase distribution at the test conditions. The remaining liquid phase will be further depressurized to continue the "differential liberation test". The aforementioned sand pack and micromodel tests will be repeated in the scenario of dynamic condition. The numerical simulation will begin by developing a modified EOS which incorporates the classical statistical mechanical potential formulae and grand canonical partition function considering the molecule-molecule interactions. A combination of modified thermodynamic EOS with the material/energy balance and percolation theory is presented to facilitate the accurate description of non-equilibrium heavy oil systems. At each time step under different depressurization rate, the mass, momentum and energy balance of bulk phases and the interfacial material exchanges will be combined into the overall calculation matrix with appropriate initial and boundary conditions. It will be solved with fully implicit and Newton-Raphson methods. The component distribution in each phase and respective fluid properties will be determined. The experimentally measured data is compared to the formulated mathematical models of the non-equilibrium heavy oil system. In general, a new methodology will be developed to describe the phase behavior and property changes of non-equilibrium states in the presence of bulk phase by combining the equation of state with the percolation theory. This particular study captures the full journey of fluid phase transition from non-equilibrium to equilibrium at both macroscopic and microscopic levels for heavy oil systems in the presence of porous medium.