Recognition of Paleoenvironments in Muddy Sandstone of Buffalo Creek Area, Sheridan County, Wyoming: ABSTRACT

Abstract

In 1983, Hershey Oil Company drilled the 1-10 Buffalo Creek well in the NW 1/4, NE 1/4, Sec. 10, T56N, R78W, Sheridan County, Wyoming. The primary target was a Paleozoic reservoir. The Lower Cretaceous Muddy Sandstone was penetrated and tested a minor amount of oil, which prompted a more detailed examination of the Muddy Sandstone. Exploration techniques used for the Muddy Sandstone included a series of sequential isolith maps based on data from the few widely spaced wells in the area. The top of the subjacent Skull Creek Shale and the bottom of a superjacent bentonite marker were used as boundaries. This method revealed the apparent transgressive nature of the remnant Muddy Sandstone. No cores were taken over the Muddy interval, so all petrographic and lithologic data were obtained from cuttings and open-hole logs. A paleoenvironmental study was done using the High Resolution Dipmeter Tool. The data were processed to obtain detailed Cluster and Geodip plots. The dipmeter information defined a remnant northeast-southwest-trending, transgressive barrier bar overlying a tidal-channel sequence oriented northwest-southeast. The length of the tidal channel would be relatively short, but due to channel migration, could be nearly as wide as the barrier bar is long.