Title: Deposition of the Woodbine-Eagleford Sandstones, Aggieland Field, Brazos County, Texas
Abstract: ABSTRACT Sandstones of the Upper Cretaceous Woodbine-Eagleford interval produce oil and gas from a stratigraphic trap at Aggieland field. The reservoir has an overall north-south trending, ovate morphology and is composed of two elongate bodies that are 3 mi (4.8 km) long by 1.5 mi (2.7 km) wide. The sandstones are thin and have an average net thickness of 16 ft (4.9 m). Grain size ranges from 0.15 mm (fine grained) to 0.30 mm (medium grained). The sandstones are classified as lithic graywackes, with a composition of 48 percent quartz, 42 percent matrix and 10 percent rock fragments. Due to the high percentage of matrix and pore filling shale clasts, permeability values are low averaging 0.10 md. Porosity ranges from 2.5 to 22 percent. Based on sedimentary structures, texture and composition, two main facies can be defined: (1) a lower massive, clast facies, which contains numerous shale clasts and oolites; (2) a sandstone facies, which exhibits bioturbated, rippled and crossbedded intervals and contains mainly monocrystalline quartz and a clay matrix. The sandstones are encased within marine shales and were transported to a middle- to outer-shelf location by a combination of tidal and storm driven marine currents. The eastern edge of the reservoir is truncated and unconformably overlain by the Austin Chalk. This truncation resulted from submarine erosion over a deep-seated salt uplift, which also influenced the paleotopography and deposition of the sandstones. The lower massive, clast facies was deposited in topographic lows by debris/gravity flows, followed by the upper sandstone facies, which was deposited by marine currents.
Publication Year: 1988
Publication Date: 1988-01-01
Language: en
Type: article
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Cited By Count: 2
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