Abstract: Two Petroleum Systems in the Sacramento Basin, California--A Basis for New Discoveries
L. B. Magoon, J. R. Castano, P. Lillis, N. H. Mackevett, N. Naeser
The Sacramento basin is a north-trending fore-arc basin that contains Late Jurassic to Holocene sedimentary rocks that become thicker to the south and are overpressured at depth. The basin fill is about 300 km long, 80 km wide, and as much as 16 km thick.
Two petroleum systems occur in the Sacramento basin. The Dobbins-Forbes(?) gas system, which contained about 2.25 tcf (1012 ft3) of recoverable gas, underlies the Winters-Domingine(?) gas system, which contained about 6.89 tcf of recoverable gas. Gas migrated laterally and to the north as much as 200 km in the Dobbins-Forbes(?) system, whereas in the Winters-Domingine(?) system, gas first migrated vertically and then crossed the Midland fault to the east for up to 40 km. For both systems, depth of gas production from reservoir rocks of Late Cretaceous to Oligocene in different trap types is less than 3 km.
By applying the petroleum-system concept and information about the geology and geochemistry available for this province, this study- provides a new testable hypothesis for the origin, migration, and accumulation of gas in the Sacramento basin. By reinterpreting some of the natural gas information, gas wetness, gas-oil ratio, vectors of migration, hydrocarbon volume, and thermal history, two petroleum systems are identified. Understanding of the origin of known accumulations in this province provides a basis for new plays that should lead to discoveries with substantial reserves.
AAPG Search and Discovery Article #90981©1994 AAPG Pacific Section Meeting, Ventura, California, April 27-29, 1994