The Granite Wash formation in Oklahoma is made up of arkosic detrital material resting on older Precambrian rocks. It can range in age from Precambrian to Middle Pennsylvanian. Formed by erosion of uplifted segments, it is generally granitic in nature; it may also include large areas of reworked carbonate. This wash presents a very difficult log interpretation problem since reservoir consistency varies greatly from well to well. Magnetic resonance image logs were added to the logging program to establish additional parameters that could be used for reservoir description. The standard Coates permeability equation and its variations were applied to estimate permeability with little correlation to production. An observation was made that T2 bin distribution data tended to mirror production rates. Attempts were made to establish an algorithm that would directly establish permeability for this formation using measured T2 data. By matching actual production rates to observed T2 distribution data, we developed an equation to estimate permeability. This case study presents the results of using T2 bin information for estimating permeability and includes several Granite Wash wells.

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