Summary

Production from the Devonian Thirtyone Formation at Dollarhide Field has been a function of variations in reservoir facies within structural compartments. The Dollarhide Devonian Unit produces from two porous intervals, an upper dolomite and a lower chert separated by nonporous limestone. The lower chert reservoir consists of laminated tripolitic chert and burrowed chert/carbonate. The upper dolomite reservoir and the burrowed chert/carbonate have highly variable porosity and permeability which resulted in moderate primary, secondary, infill and tertiary (CO₂ flood) recovery. The laminated tripolitic chert has very high porosity and relatively uniform permeability, which resulted in moderate primary recovery, excellent waterflood production, and poor infill production. Reservoir compartments vary in size laterally from <20 to 640 acres and play a critical role in designing secondary and tertiary recovery projects. Lateral compartmentalization has resulted from faults with throws of greater than 40 feet, erosion of reservoir intervals on the crest of the structure, and by pinchouts of porous facies. A 3D seismic survey greatly improved the mapping of reservoir compartments by (1) delineation of high porosity areas from variations in seismic amplitude, (2) accurately locating previously identified faults and (3) recognition of many “new” faults.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah