Comparison of solution schemes for black oil reservoir simulations with unstructured grids Original Research Article

This paper presents comparative results of the fully implicit, iterative IMPES, and sequential solution schemes for black oil reservoir simulations with unstructured grids. These schemes are verified and compared for field-scale models of both saturated and undersaturated reservoirs. The comparative results show that: (a) The fully implicit scheme is most stable and robust for both reservoirs, but has the highest memory and computational cost. (b) The sequential scheme takes much less memory and computational cost than the fully implicit scheme to reach the same precision for the undersaturated reservoirs, when the same iterative control parameters are used; however, for the saturated reservoirs, the sequential scheme must use stricter iterative control parameters to reach the same precision. (c) The iterative IMPES scheme is not a good choice for the black oil reservoir simulation.