A novel approach for automatic grid generation for multi-phase flow simulators: A robust computational framework for mass transfer at bubble point pressure

Coarsening from fine geological model to dynamic coarse scale is an essential task in reservoir simulation. In this paper a new approach is introduced to create a coarse dynamic model based on effective parameters of fluid flow in porous media. In this technique, the effects of fine scale permeability map, key flow paths (streamlines) and well location are considered to build a coarse dynamic model from a fine geological one. An exact element size map is generated by comparing all the mentioned effective parameters and making the element size indicator by selecting the maximum value. This element size map (background grid) is applied to build an unstructured mesh for discretization of the reservoir. Afterward, this intelligent mesh generator was employed in three-phase flow simulation. Moreover, a novel computational framework is developed for the evaluation of bubble point pressure to prevent divergence of the solution when the reservoir conditions change. To evaluate the performance of the developed model, the fluid flow rate obtained by this model is compared to that obtained by the uniform grid model. It is found that the proposed method provides more accurate results for fluid flow rate compared to the uniform grid model. Moreover, it is faster and computationally less expensive than the fine model. This model can be applied in reservoir simulators and provides more accurate and reliable results in less CPU time compared to the traditional mesh generation techniques. In addition, the proposed model solves the problem of divergence of the solution at the bubble point pressure.