A physically-consistent method is suggested for calculation of coexistent hydrocarbon phases' compositions in flow simulations with non-equilibrium phase transitions. The method preserves standard flow terms' formulation and can be incorporated in existing commercial simulators without principal modifications to flow simulation algorithms.

Through the analysis of laboratory experiments data and computational studies, we show that the necessity for non-equilibrium phase behavior model depends on simulation scale. We introduce an upscaling algorithm to estimate parameters of a non-equilibrium coarse grid model.

An algorithm is proposed to calculate non-equilibrium phase compositions with desired level of non-equilibrium behavior and model different speeds of relaxation of fluids' compositions to their equilibrium states. Relaxation dynamics is determined by pressure changing rate as well as initial phase compositions and pressure. These effects are essential for consistent history matching of a flow simulation model of an oil or gas-condensate reservoir with minimal number of matching parameters.

Examples of using the method to simulate non-equilibrium phase behavior of real oil and gas-condensate mixtures are presented.

Keywords:
Upstream Oil & Gas, transition, mass transfer, interphase mass transfer, Modeling & Simulation, gas-condensate mixture, Simulation, non-equilibrium phase behavior, composition, PVT measurement
Subjects:
Fluid Characterization, Reservoir Simulation, Phase behavior and PVT measurements
Copyright 2015, Society of Petroleum Engineers
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