Analysis of Diffusion Models in Eclipse 300
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Molecular diffusion could be an efficient recovery mechanism in many applications in reservoir engineering. Proper modelling of diffusion in hydrocarbon mixtures at the reservoir conditions is not a simple task and requires reliable diffusion coefficients for accurate diffusion flux calculations.The main objective of this study is to analyse diffusivity models for a wide range of experimental conditions, so that to examine diffusion performance driven by concentration and chemical potential gradients. We simulate the diffusion experiments in the porous media, considering mixing in the binary system composed of C1 and C2 components. The commercial compositional simulator Eclipse 300 with fully implicit solution method is used for simulation study. In the all run cases, the system is assumed to be isothermal. The study was restricted to diffusion in the single gas phase, unless the cross-phase diffusion was under investigation.This work is also directed to determine diffusion coefficients from simulated diffusion experiments. The conventional approach to estimate diffusion coefficients from laboratory experiments is adopted to determine mass transfer coefficients from simulation results. It has been proved that numerical solution is a result of pure diffusion transfer and unequal bulk flows of C1 and C2 particles. The effect of mixture molar density variation with composition on diffusion behavior has been studied. It will be shown that fluctuations of mixture volumetric properties create convective bulk fluxes, which can either intensify or oppose mass transfer by pure diffusion flow.The study of the effect of molar density variation on diffusion performance considering a simple binary mixture, however, provides a basis for a better understanding of more realistic situations in which the mixture consist of more than two components.