Hydrocarbon Traps within a Seismic Sequence Framework, Stevens Turbidites, Southern San Joaquin Valley, CA
HEWLETT, JAMES S., and DOUGLAS W. JORDAN, ARCO Oil and Gas Company, Plano, TX, and TERRY J. CREBS and THOMAS P. MOOREFIELD, ARCO Oil and Gas Company, Bakersfield, CA
Interpretation of the seismic sequence framework and log and lithologic character of upper Miocene Stevens turbidites on the Bakersfield arch has led to an improved understanding of the expression of stratigraphic trapping that should reduce exploration risk in this basin, and may aid exploration efforts in similar sand-rich systems globally.
These deepwater sandstones are contained within three lowstand turbidite systems (LTS) that were deposited in a narrow deepwater basin adjacent to the ancestral Sierra Nevada. The oldest LTS, the Coulter, was transported through several submarine canyons incised into the Fruitvale Shale. In contrast, numerous smaller scale erosional features located on the high-relief slopes of the highstand Santa Margarita deltas, fed the overlying Gosford and Bellevue LTS. The systems consist of sandy, high-density (primarily) and low-density turbidites that were deposited within channel-lobe complexes. Each LTS is stacked in a compensatory manner and is bounded by regionally extensive siliceous shales (condensed sections).
On the arch, 472 MMBO and 1.3 tcf have been produced from four seismically detectable traps with strong stratigraphic components: (1) sandstone permeability changes within turbidite wedges that thin rapidly onto structure (e.g., Upper Western zone, North Coles levee), (2) confined (channelized) turbidites that lap out on a structure (e.g., F-1 sand, South Coles levee), (3) channelized turbidites that pinch out within slope gullies (e.g., 28-22 sand, English Colony), and (4) depositional (compaction) anticlines occurring in conjunction with low-gradient regional structure (e.g., 73X sands, Strand). Condensed section sediments form regional and reservoir-scale seals. Rapid lateral facies changes and grain size variations provide additional seal facies.
AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)