Measuring inter-reservoir cross flow rate between adjacent reservoir layers from transient pressure tests

A measure of inter-reservoir cross flow rate between adjacent reservoir layers which are productive of hydrocarbons is determined. With passage of time, pressure differentials between reservoir layers can grow due to continuous production from an active layer. In addition, the flow area between an active layer and adjacent layers can grow with time for a given reservoir system. These changing pressure and flow conditions with time can contribute to substantial amounts of cross flow rates, which need to be accounted for when characterizing the commercial producibility of the active layer. The inter-reservoir cross flow rate is based on a measure of specific permeability and of cross flow rate within a reservoir layer which is obtained from pressure transient tests of the reservoir formations.