LAUSR

Abstract Molecular diffusion plays a vital role in production from fractured reservoirs in all stages of recovery, especially for fractured reservoirs with small matrix sizes and unfavorable wettability conditions. Molecular diffusion can only be simulated by compositional reservoir simulators, which have historically employed a decoupled phase equilibrium-mass transfer model. Regardless of having higher performance, such a model cannot properly simulate intra- and cross-phase molecular diffusion. In the current research, a compositional fractured reservoir simulator, called Osiris, has been developed in C++ using the coupled formulation. After presenting the primary equations and algorithms, the performance of Osiris has been evaluated through a series of case studies. Utilizing MPI, Osiris could keep its runtime reasonable, despite the high computational demand of coupled modeling. Additionally, the simulation results of Osiris clearly prove the precision of the coupled modeling; and considerable effects of diffusive mass transfer on fractured reservoir performance.