Abstract: Lithofacies of Upper Pennsylvanian Lansing-Kansas City Groups in Northwest Kansas-Southwest Nebraska
W. Lynn Watney
Lithofacies of the subsurface Upper Pennsylvanian Lansing-Kansas City Groups in northwestern Kansas have been determined from well cores and cuttings. Prediction of trends in the porous facies is essential to minimizing risk in exploration for oil and gas in these rocks.
The Lansing-Kansas City Groups comprise cyclic sequences of limestones and shales consisting, from base to top, of: (1) thin, "transgressive," fusulinid wackestone or packstone; (2) gray or green, fossiliferous, marine shale; (3) thicker, "regressive," lime bioclastic wackestone and oolitic or bioclastic lime packstone or grainstone; and (4) red, nonmarine shale or siltstone. The best reservoir rocks most commonly are at the tops of the "regressive" limestones in a shallow lagoon or on a tidal flat. Primary intergranular porosity in these limestones is enhanced by dissolution and nontectonic fracturing formed during subaerial exposure and by partial dolomitization or recrystallization of micritic matrix.
Automated analysis of well logs and computer mapping of log-derived parameters aid in extending trends recognized in cores and samples. Specialized cross plots are used to examine possible relations between log measurements and facies characteristics.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC