The younger Permian carbonates have been prolific producers over the years. The San Andresand Grayburg dolomites, which are productive in nearly all areas of west Texas, are ol particular note. Although traditional log analysis has been generally successful in ihese reservoirs, the presence ol gypsum in many has created difficulties. Gypsum tends to result in overly optimistic porosity calculations and also tends to restrict permeability by plugging the pore throats.

This paper exjfiains some ol the difficulties encountered when using traditional log analysis techniques in gypsiferous reservoirs and shows how the ELAN* log interjmetation program has been used to give superior results.

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