Woodbine Reservoir Facies, Kurten Field, Brazos County, Texas: ABSTRACT

Abstract

Woodbine-Eagle Ford reservoirs are productive over an area of about 55 mi2 (140 km2) in Kurten field. The Woodbine C sandstone is its 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 dune facies, which consists of thin-bedded, medium-grained (0.28 mm) quartzose sandstones; (2) a rippled facies, which consists of thinly interbedded shale and fine-grained (0.17 mm) sandstone; and (3) a bioturbated facies, which consists of highly churned, very fine-grained (0.12 mm) sandstone. These facies result in decreasing permeabilities from an average 17 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 southern limit of the reservoir is controlled by a deep salt dome or ridge, called Hill dome, that trends northeastward. The upper Woodbine-Eagle Ford 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 bathymetric high on the sea floor that was scoured by currents. Successively finer grained sands were deposited to the north under conditions of decreasing flow regime and increasing water depths. End_of_Article - Last_Page 141------------