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COBURN, GARY W., and KENNETH E. BEENEY, Tatham Offshore, Inc., Houston, TX

ABSTRACT: West Delta Block 35: Rediscovery of a 23-Year-Old Field

The federal leases on the continental shelf, offshore Gulf of Mexico, are mature in terms of development. Many fields are reaching their productive and/or economic limits as defined by their operators, and are being released, resulting in excellent opportunities for independents who recognize the importance of modern technology and apply it to their evaluation process.

West Delta Block 35 originally was divided into two leases. The southern three-quarter-block lease was released in 1991 having produced 92.3 bcf and 3.5 million bbl since 1970. The northern one-quarter-block lease was released in 1983 having produced 64.3 bcf and 0.25 million bbl since 1974. The northern one-quarter was subsequently leased in 1985 and expired in 1991 with no activity having transpired. The northern one-quarter and the southern three-quarters were combined and the entire block was available at the 1992 lease sale.

The West Delta Block 35 was evaluated using the following methods: history (leases, companies involved, and changing economic conditions); well records (production, tests, recompletions, previous permits, and related activity); well-log evaluation, including (1) correlation, (2) analysis using PC-based software with user-defined saturation equations and multiple models to determine hydrocarbon-bearing zones, and (3) integration with all other available data; seismic evaluation, including (1) interpretation using workstation technology, (2) modeling various horizons using well data, (3) integration with well-log data; reservoir evaluation (pressure data, sand parameters, volumetrics, etc.).

Workers determined that significant reserves remained in an updip position on the northern one-quarter of the block in two reservoirs, with an additional reservoir having been penetrated but never produced. Workers also recognized additional potential on the southern part of the block.

The lease was acquired in the 1992 lease sale and the northern prospect was drilled in late 1992 and early 1993. The well found pay in three sands. Two sands were tested (prior to acidization) for a combined rate of 12.8 MMCFD, with the well still cleaning up. The well proved significant reserves in two previously produced reservoirs and added a new field pay.

AAPG Search and Discovery Article #90989©1993 GCAGS and Gulf Coast SEPM 43rd Annual Meeting, Shreveport, Louisiana, October 20-22, 1993.