Print this pageAbstract: Oil and Gas from Submarine Channels in Great Valley, California
The Great Valley of California is comprised of the Sacramento basin, a dry-gas province at the north, and the San Joaquin basin, producing both oil and gas at the south.
A significant amount of the reserves discovered to date has been associated with submarine channels. These productive channels may be segregated into two major types. Destructive or erosional channels are primarily submarine canyons with a definite erosional base cutting into older sediments. These channels or "gorges" are common in the Sacramento basin. Minor gas accumulations are found in the channel fill, but significant production has been established adjacent to these channels in traps formed by truncation of the reservoir sandstones against shale fill in the gorges. Constructive or nonerosional channels contain a major part of the reserves in the San Joaquin basin. These are sublinear sandstone bodies controlled in part by seafloor topography. Generally, they follow paleoslope o basin gradient in the direction of depocenters. These turbidity channels commonly exhibit an incomplete Bouma cycle and are usually multilobed. These lobes meander laterally and vertically in a compensating pattern similar to delta-front deposition.
In the upper Miocene of the San Joaquin basin, this type of channel deposition formed conduits into the prolific source rocks enriched by the diatom blooms common to the deep-marine Monterey Shale. Hydrocarbons then accumulated where the channels crossed the large second-order drag folds associated with lateral shearing on the San Andreas fault. These combination structural and stratigraphic traps contain the major part of the upper Miocene reserves at Elk Hills, Asphalto, Buena Vista Hills, Paloma, Midway-Sunset, and the recent discoveries at Yowlumne, Tule Elk, Cal-Canal, and Rio Viejo.
In addition to these large accumulations in discrete channels, there are many smaller fields on the Bakersfield arch that produce from constructive channels that coalesce to form submarine fans. The most productive areas are in the high-energy channels within the upper fan deposits.
AAPG Search and Discovery Article #90962©1978 AAPG 2nd Circum-Pacific Energy and Minerals Resource Conference, Honolulu, Hawaii