Five oriented cores from the Cities Service Co. enhanced oil-recovery project, Madison Block (Unit B) of the Seeley-Wickfield, were analyzed. Primary production, air, and water drives in the Middle Pennsylvanian Bartlesville Sandstone (Cherokee Group) have produced 12.5 million bbl of oil with 18.6 million bbl remaining.

Six depositional facies are recognized in the cores. The

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facies are, in ascending order, a prodelta shale and siltstone facies, a distributary channel sandstone facies, an overbank shale and siltstone facies, an interdistributary bay and splay channel facies, an estuarine sandstone, shale, and siltstone facies, and a lagoonal sandstone and siltstone facies. This genetic vertical sequence package, typical of fluvial-deltaic sediments, is typified by an upward change in the scale of sedimentary structures, an increase in radioactivity of the gamma ray log, a decrease in grain size, a decrease in permeability, and a subsequent increase in the amount of interstitial clay matrix.

Permeability is primarily controlled by packing, sorting, the presence of ductile rock fragments, and the amount of clay matrix. Permeability of the distributary channel sandstone facies, the primary reservoir, decreases from 60 to 100 md in trough cross-bedded sandstones to 20 to 60 md in rippled sandstones and siltstones. Low permeability values (0 to 20 md) are characteristic of facies containing siltstone and shale.

The distributary channel sandstone facies (28 to 62 ft or 8 to 19 m thick) is continuous across the pilot project area and varies in thickness in a predictable manner. Dip directions of trough cross-beds observed in four oriented cores suggest that the distributary channel flowed to the west-southwest across the project area. The overbank shale and siltstone facies and the interdistributary bay and splay channel facies are not continuous across the project area and are interpreted to have been deposited in the topographically low area adjacent to the distributary channel.

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