Application of reservoir characterization and advanced technology to improve recovery and economics in a lower quality shallow shelf carbonate reservoir. Quarterly progress report, August 1995--December 1995

Abstract

West Welch Unit is one of four large waterflood units in the Welch Field located in the Northwestern portion of Dawson County, Texas. The Welch Field was discovered in the early 1940`s and produces oil under a solution gas drive mechanism from the San Andres formation at approximately 4800 ft. The field has been under waterflood for 30 years and a significant portion has been infill drilled on 20-ac density. A 1982-86 Pilot CO{sub 2} injection project in the offsetting South Welch Unit yielded positive results. The recent installation of a CO{sub 2} pipeline near the field allowed the phased development of a miscible CO{sub 2} injection project at the South Welch Unit. The reservoir quality is poorer at the West Welch Unit due to its relative position to sea level during deposition. Because of the proximity of a CO{sub 2} source and the CO{sub 2} operating experience that would be available from the South Welch Unit, West Welch Unit is an ideal location for demonstrating methods for enhancing economics of IOR projects in lower quality SSC reservoirs. This Class 2 project concentrates on the efficient design of a miscible CO{sub 2} project based on detailed reservoir characterization from advanced petrophysics, 3-D seismic interpretations and cross wellbore tomography interpretations. During the quarter, progress was made in both the petrophysical analysis and the tomography processing. The final geologic model is dependent upon the petrophysical analysis and the seismic and tomography interpretations. The actual reservoir simulation has started using the base geologic model, with which, all the preliminary simulation work is being done. Progress was also made in understanding the abnormal fracture wing orientation obtained in well 4807 and the cyclic CO{sub 2} demonstration results.