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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 551

Last Page: 551

Title: East Brentwood Gas Field: A Paleotopograhic Trap: ABSTRACT

Author(s): Richard W. Boyd

Article Type: Meeting abstract

Abstract:

The East Brentwood gas field is located about 45 mi (72 km) east of San Francisco, California. The discovery well was drilled in 1978 by Depco, Inc. and completed in the Upper Cretaceous Third Massive sand at a depth of 8,050 ft (2,454 m). The Third Massive sand is a progradational sequence of sands with thin shale interbeds, interpreted to have been deposited in a nearshore, open-sea environment. The reservoir sand is dramatically truncated by the Meganos Gorge, a shale-filled fossil channel of Paleocene age. Faunal assemblages indicate that the cutting and filling of the gorge were submarine rather than subaerial.

The East Brentwood gas field is primarily controlled by the truncation of the basal part of the Third Massive sand by the Meganos Gorge shale fill with lateral closure afforded by several normal faults which divide the field into at least four separate producing blocks. Exploration mapping techniques, including seismic and well control, concentrate on the relation of the Massive sands to the basal Meganos Gorge configuration, the intersection of which essentially represents a buried paleotopographic surface. Exploration for updip sand termination against the shale-filled erosional gorge feature should result in the discovery of additional natural gas accumulations. Nine wells are presently completed in the gas field in which the better wells have over 250 ft (76 m) of net gas sand. Th field has produced 19 bcf of 1,080 Btu gas and 50,000 bbl of 46° API gravity condensate since discovery. Field ultimates are expected to be in excess of 40 bcf and 100,000 bbls of condensate.

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