The geological static models of realistic contexts are described with high resolution meshes (HRM) and cannot be directly used as input lor fluid flow reservoir simulators due to memory and/or running time constraints. The pragmatic approach consists in averaging the high resolution petrophysical values to assign to a low resolution mesh (LRM) used to perform reservoir simulations Hence, predictions made with these coarser meshes are inevitably less accurate than those that would have been obtained on HRM For compositional modelling, the loss of accuracy due to upscaling processes will come not only for the component displacements but also from the solution of the thermodynamic and/or geochemical equilibrium equations. For example, a chemical reaction of an acid on carbonated rock may highly depends on its concentration. Therefore, our main motivation here is to keep an HRM for calculating those chemical equilibriums. We propose to name this innovative approach "Compositional Dual Mesh Method" (CDMM). The CDMM is a formulation with two different meshes: The pressure equation is solved on a LRM using upscaled properties and the transport equation and chemical equilibrium are solved on a HRM.
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