ABSTRACT

Woodbine-Eagleford reservoirs are productive over an area of about 55 sq. mi. (140 km²) in Kurten field. The Woodbine "C" sandstone is the most extensive reservoir and has an average net thickness of 30 ft (9 m). The "C" sandstone shows distinctive changes in rock type from south to north: (1) a cross-bedded dune facies consists of thin-bedded, quartzose medium grained (0.28 mm) sandstones; (2) a rippled facies consists of thinly interbedded shale and fine grained (0.17 mm) sandstone; and (3) a bioturbated facies consists of highly churned very fine grained (0.12 mm) sandstone. These facies result in permeabilities decreasing from an average 47 md in the south to 0.1 md in the north.

The "C" sandstone was deposited in a middle- to outer-shelf location, and sands were supplied by storm-driven or tidal currents from the "Harris delta" to the east. The south limit of the reservoir is controlled by a deep salt dome or ridge, called Hill Dome, that trends northeastward. The upper Woodbine-Eagleford section was truncated by erosion along this trend and unconformably overlain by lime muds of the Austin Chalk. Sandstone facies suggest that salt uplift during deposition created a high on the seafloor which was scoured by currents. Successively finer-grained sands were deposited to the north under conditions of decreasing current flow and increasing water depths.