Abstract

A facies model of the subsurface Bartlesville Sandstone in Sallyards field, Greenwood County, Kansas, was developed from well core descriptions, petrographic analysis, electric log examination, and construction of maps and cross-sections.

Subsurface mapping indicates that the Bartlesville Sandstone is narrow and elongate in plan view and lenticular in cross-section. It displays an asymmetrical convex-down base, thickens at the expense of the underlying shales, and is a multi-storied sandstone body. Self-potential logs usually show an abrupt basal contact and a blocky or an upright bell-shaped curve. A structure map at the top of the pre-Pennsylvanian surface indicates that deposition of the Bartlesville Sandstone was influenced by underlying structure.

The sandstones are mineralogically and texturally immature with abundant metamorphic rock fragments, micas, clays, angular tourmaline, and feldspar grains. The amounts of clays and micas increase and grain size decreases upward in the sandstone as shown by thin-section measurements. Biogenic material includes abundant wood fragments and organic matter in the conglomerate zones.

Core studies reveal a vertical sequence for the Bartlesville Sandstone consisting of a sharp basal contact, large-scale cross-bedding, massive bedding or conglomerate zones, unidirectional current ripples, and a gradational or sharp contact with overlying siltstone. The scale of sedimentary structures decreases upward. The laterally associated facies consist of dark gray to black shale, greenish gray shale, ironstone, underclay, coal, and limestone.

Comparison of the above facies model with process-response models of modern depositional environments indicates that the Bartlesville was deposited as a perennial, fine-grained, meandering, alluvial stream following lows on the eroded pre-Pennsylvanian surface. The associated facies were deposited in a delta-plain to shallow-marine environment. Enclosure of the sandstone bodies in oil-rich shale and later structural movement led to favorable conditions for the development of combination structural-stratigraphic traps.

Previous regional work, checked by log correlations across Kansas, suggests that the Bartlesville Sandstone in Sallyards field is laterally equivalent to the surface Bluejacket Sandstone.