Reservoir Description of a Sand-Rich Submarine Fan Complex for a Steamflood Project: Upper Miocene Potter Sandstone, North Midway Sunset Field, California

G. Shanmugam, C. A. Clayton

Nearly 650 m of cores from the upper Miocene Potter sandstone in Mobil's Alberta/Shale property, North Midway Sunset field, California, were examined to determine depositional facies, sand-body geometry, and reservoir quality for a proposed steamflood project. The Potter represents a sand-rich submarine fan complex with braided-channel, meandering-channel, levee, and crevasse-splay facies. The braided-channel facies (gravel and coarse sand) is thick (up to 100 m), sheetlike (> 500 m wide), and highly permeable (10,000+ md). The meandering-channel facies (coarse to medium sand) is up to 20 m thick, over 400 m long, lenticular in geometry, and exhibits an upward decrease in permeability (e.g., 9,000 to 500 md) related to grain size that fines upward. The levee facies (in bioturbated sand) is up to 21 m thick, shows variable geometry, and is generally low in permeability (100-1,500 md). The crevasse splay (medium sand) is up to 12 m thick, sheetlike (> 300 m wide), and shows moderately high permeability (2,000-8,000 md). The braided-channel facies was a product of density-modified grain flows, and the remaining three facies were deposited by turbidity currents. Steamflooding of the Potter reservoir should perform extremely well because the entire reservoir is composed of relatively clean sand and the reservoir lacks both horizontal and vertical permeability barriers.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.