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Abstract: Petroleum Systems In the Sacramento Basin, California, USA

Leslie B. Magoon, Zenon C. Valin, Paul G. Lillis

The Sacramento Basin, a north-trending forearc basin that contains Late Jurassic to Holocene sedimentary rocks which thicken to the south, is primarily a gas province with minor occurrences of oil, comprising four petroleum systems, two of gas and two of oil.

The Dobbins-Forbes(?) gas system, which contained about 2.25 tcf (1012 ft3) of recoverable gas, underlies the Winters-Domengine(?) gas system, which contained about 6.89 tcf of recoverable gas. Gas migrated laterally to the north as far as 200 km in the Dobbins-Forbes(?) system, whereas in the Winters-Domengine(?) system, gas first migrated vertically and then crossed the Midland Fault to the east for as far as 40 km. In both systems, depth of gas production is less than 3 km.

On the basis of petroleum geochemistry of the oils, two unnamed oil systems have been identified. Oil recovered from cinnabar mines, a gold mine, seeps, and a few wells along the northwest flank of the basin are all similar and constitute one oil system. The provenance of this oil type is a Cretaceous source rock. The oil from the Brentwood and Livermore Oil Fields at the south end of the province, which constitute the other oil system, is thought to originate from the Kreyenhagen Formation of Eocene age.

By applying the petroleum-system concept and available information about the geology and geochemistry of this province, our study provides a new testable hypothesis for the origin, migration, and accumulation of petroleum in the Sacramento Basin.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela