1. A method of history matching a simulation model, comprising: (a) defining regions exhibiting similar rule based behavior in said model thereby generating said model having a plurality of regions, each of the plurality of regions including grid cells and exhibiting a similar rule based behavior wherein the defining comprises Self-Organizing Map-based clustering of grid cells, recalling the identity of those grid cells within each cluster which has similar rule based behavior, and grouping together grid cells into groups each group defining a region exhibiting similar rule based behavior according to the clustering; (b) introducing historically known input data to said model; (c) generating output data from said model in response to said historically known input data; (d) comparing said output data from said model with a set of historically known output data to determine an error; (e) adjusting said model when said output data from said model does not correspond to said set of historically known output data, the adjusting step including the step of arithmetically changing grid cells in one or more each of the regions of said model based at least in part on the error; and (f) repeating steps (b), (c), (d), and (e) until said output data from said model does correspond to said set of historically known output data.