1. A multi-scale finite volume method for use in simulating a fine-scale geological model of a subsurface reservoir, the method comprising: (a) providing a fine-scale geological model of a subsurface reservoir associated with a fine-scale grid having a plurality of fine-scale cells; (b) defining a primary coarse-scale grid having a plurality of primary coarse-scale cells; (c) defining a dual coarse-scale grid having a plurality of dual coarse-scale cells, the dual coarse-scale grid defining a portion of the fine-scale cells as internal cells, edge cells, and node cells; (d) constructing a multi-scale matrix where blocks of the multi-scale matrix are ordered responsive to the internal cells, edge cells, and node cells; (e) computing pressure in the dual coarse-scale cells using a coarse-scale operator, the coarse-scale operator being a multi-diagonal block of the multi-scale matrix; (f) computing a conservative flux field responsive to the pressure in the dual coarse-scale cells while accounting for transverse fluxes between the dual coarse-scale cells wherein computing the conservative flux field utilizes a multi-scale inverse matrix; and (g) producing a display responsive to the conservative flux field.