Bolton field produces oil from numerous lenticular, Lower Cretaceous sandstones at depths ranging from 8,350 to 11,800 ft (2,545 to 3,596 m). The field is on an elongated, faulted anticline in the northwest part of the Mississippi salt basin. It was discovered in 1954 as a result of seismic mapping. Two years after its discovery it had produced 1,475,179 bbl of oil. A core of the Lower Cretaceous Paluxy sandstone, and electric logs from the field area, were studied to determine the environment of deposition and reservoir morphology.

The Paluxy sandstones were deposited within a fluvial system. Primary rock properties observed in the core indicate a braided stream deposit. Bedsets are thin, ranging from 0.5 to 9 ft (.15 to 2.74 m) in thickness. Sedimentary structures within bedsets consist of inclined laminae in the lower part to parallel laminae and ripples in the upper part, indicating deposition

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from decreasing flow regime. This sequence of bedding, together with the vertical decrease in grain size observed, is typical of a fluvial sandstone. Sandstones (quartzarenite) are characterized by a high quartz content (85 to 98%), moderate matrix (5 to 10%), and a small amount of minor constiuents (muscovite and calcite).

Electric log cross sections reveal lateral variation in sandstone thicknesses. Sand bodies are lenticular and discontinuous, characteristic of intermittant braided stream deposition. Reservoir sandstones have porosities ranging from 12 to 22% and permeabilities of up to 500 md. Recognition of the vertical sequence of primary rock properties is indicative of braided stream deposits, and the associated electric log characteristics may aid in future exploration and production efforts for similar reservoirs.

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