--> Abstract: Growth Patterns of a Turbidite Complex in an Active-Margin Basin, Yowlumne Field, San Joaquin Basin, California, by M. S. Clark, J. Melvin, and M. Kamerling; #90958 (1995).

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Abstract: Growth Patterns of a Turbidite Complex in an Active-Margin Basin, Yowlumne Field, San Joaquin Basin, California

Michael S. Clark, John Melvin, Marc Kamerling

The Yowlumne sandstone represents a lobate, northward-pro grading turbidite complex that was deposited, during the late Miocene, in eight or more stages along the tectonically active southern margin of the San Joaquin basin, California. This sandstone, which has produced most of the 100 MMBL of oil attributed to Yowlumne field, is one of several different, discontinuous reservoirs that make up the Stevens sandstone, a deep-marine clastic facies of The Miocene Monterey Formation. The Yowlumne reservoir is a lens-shaped, complex-layered sandstone body with evidence of channeling and erosion within the body. However, because seismic markers bounding the body are not truncated and merge on the margins of it, the body itself does not incise underlying strata.

Pressure data, 3D-seismic, and detailed well log correlations indicate lens-shaped, lobate sandstone layers within the Yowlumne reservoir that downlap to the north and are separated by thin shales. These layers represent separate permeability pathways that are in pressure communication over geologic time (thousands of years) but become weakly compartmentalized during rapid reservoir draw down (tens of years). Two layers form a left-stepping (westward), shingled complex that resulted from lateral shifting of turbidite depositional lobes. A second, younger, left-stepping complex of five-layers is located basinward (northward) from the first and represents a basinward shift of deposition. A third, even younger complex may be located basinward from the second. Most likely, left-stepping g ometries represent lobe switching influenced by Coriolis forces, whereas basinward-stepping geometries represent progradation controlled by accommodation.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California