Existing exploration-discovery models are generally characterised by equations describing the behaviour of exploration, success rates, and discoveries. The present paper adds two equations describing the behaviour of finding costs and exploration efficiency. The model was disaggregated along regional lines. Applying the model to UK Continental Shelf data over the period 1964-2002 produced results that supported the new approach. Analysis of the model dynamics and simulation forecast reveals similarities, but also important differences in the responsiveness of activity in the regions to policy multipliers, implying that uniform policy instruments will produce unequal responses in areas with different levels of maturity.