Abstract

The Bend conglomerates of north Texas are lithologically diverse Lower Pennsylvanian sandstones and conglomerates deposited by a variety of depositional systems. In southeast Foard County, the basal Bend conglomerates form oil-productive sandstone bodies morphologically identical to both ancient and modern coastal marine bars.

A basal Bend shale isopach map of southeast Foard County delineates the paleotopography of the eroded Mississippian surface over which the Early Pennsylvanian sea transgressed. Its contours parallel paleostrike and ancient shoreline positions. Wells within a narrow 20-ft interval of this map penetrated a thin sand at the base of the basal Bend shale. These sandstones form elongate, lenticular bodies that parallel isopach contours and an ancient shoreline.

This critical isopach interval is interpreted as representing the depositional strike of a coastal marine bar system developed during a stillstand of the encroaching Early Pennsylvanian sea. These small, narrow bars are beyond the resolution of the sparse well control in the study area. Super-imposition of known basal Bend bars on the basal Bend shale isopach, however, allows the projection of these narrow stratigraphic traps along an ancient shoreline into undrilled prospective areas.

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