Influence of Anticlinal Growth on Upper Miocene Turbidite Deposits, Elk Hills Field, Kern County, California

REID, STEPHEN A., Bechtel Petroleum Operations, Inc., Tupman, CA, and GEORGE S. MCJANNET, U.S. Department of Energy, Tupman, CA

Growth of subsea anticlines during deposition of the upper Miocene 24Z and 26R sandstones at Elk Hills caused the development of several sinuous, lenticular sand bodies. Later structural growth enhanced the trap characteristics of these sandstones. Both sandstones are in the uppermost portion of the Elk Hills Shale Member of the Monterey Formation and contain channel-fill and overbank deposits of sand-rich turbidite systems. At the onset of turbidite deposition, low relief subsea anticlines separated broad basins which progressively deepened to the northeast. Channel-fill deposits of coarse-grained sand generally followed the axes of these northwest-southeast-trending basins. At several sites, channel-fill deposits also spilled north across anticlinal axes into the next lower basins. ide bands of overbank sand and mud were deposited at sand body edges on the flat basin floors. Midway through turbidite deposition, a period of anticlinal growth substantially raised subsea relief. Channel-fill deposits continued in narrower basins but passed north into deeper basin only around well-defined sites at the anticlines' downplunge termini. Narrow basin shapes and higher anticline relief prevented significant overbank deposition. With Pliocene to Holocene uplift of the late Miocene structural trends, stratigraphic mounding of the north-directed channel-fill deposits helped create structural domes at 24Z, 2B and Northwest Stevens pools. In sand bodies lacking significant overbank deposits prevented oil entrapment in sand bodies deposited at times of low anticlinal relief.

AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)