Nested gridding and streamline-based simulation for fast reservoir performance prediction

Detailed reservoir models routinely contain 10(6)-10(8) grid blocks. These models often cannot be used directly in a reservoir simulation because of t he time and memory required for solving the pressure grid on the fine grid. We propose a nested gridding technique that efficiently obtains an approxi mate solution for the pressure field. The domain is divided into a series o f coarse blocks, each containing several fine cells. Effective mobilities a re computed for each coarse grid block and the pressure is then found on th e coarse scale. The pressure field within each coarse block is computed usi ng flux boundary conditions obtained from the coarse pressure solution. Str eamline-based simulation is used to move saturations forward in time. We te st the method for a series of example waterflood problems and demonstrate t hat the method can give accurate estimates of oil production for large 3D m odels significantly faster than direct simulation using streamlines on the fine grid, making the method overall approximately up to 1,000 times faster than direct conventional simulation.