--> Abstract: Tectonic and Paleotopographic Controls on Compartmentalization of Turbidite Reservoirs, Miocene Stevens Sandstone, San Joaquin Basin, CA, by M. S. Clark, R. K. Prather, and J. D. Melvin; #90928 (1999).

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CLARK, MICHAEL S., RICK K. PRATHER, and JOHN D. MELVIN
ARCO Western Energy.

Abstract: Tectonic and Paleotopographic Controls on Compartmentalization of Turbidite Reservoirs, Miocene Stevens Sandstone, San Joaquin Basin, CA.

Yowlumne is a giant oil field, with 103 MMBO of production, that produces from the Yowlumne sandstone—a fan-shaped, layered, prograding turbidite complex deposited as seven lobe-shaped reservoir compartments along the tectonically active southern margin of the San Joaquin basin, CA. This sandstone is one of several that make up the Stevens, a deep-marine elastic facies of the Miocene Monterey Formation with significant remaining petroleum reserves swept by waterflooding against distal fan margins and isolated in unswept reservoir pockets.

Pressure, 3D-seismic, and well log data indicate correlation of stacked reservoir compartments to shale-bounded, lobate sandstone layers depositionally confined to a subtle paleotopographic low. Left-stepping geometries resulted from Coriolis forces which effected preferential buildup of overbank shales on the right margin of the fan, thus forcing onlap of lobe/channel sandstones against a growing paleohigh on the left margin. Basinward-stepping geometries resulted from decreasing accommodation and increasing sediment flux. Some compartments are bounded by shales that prevent fluid communication. Others represent separate permeability pathways, in pressure communication over geologic time, that become compartmentalized during rapid reservoir draw down.

Compartmentalization results from clinoform geometries in which horizontal permeabilities exceed vertical permeabilities. Apparently, hydrocarbons move easily along permeability pathways corresponding to Bouma sequences that parallel clinoform surfaces. By contrast, flow across clinoforms is impeded by shales, slumped intervals, and cemented zones. Oil backs up behind these barriers to create adjacent pools, with separate fluid contacts, occupying progressively higher structural levels in the fluid migration direction—thereby giving the incorrect impression of a tilted oil-water contact.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas