Geochemical and Mineralogical Sampling of the Devonian Shales in the Broadtop Synclinorium, Appalachian Basin, in Virginia, West Virginia, Maryland, and Pennsylvania

Abstract

Reconnaissance field mapping and outcrop sampling for geochemical and mineralogical analyses indicate that the Middle Devonian Marcellus Shale in the Broadtop synclinorium and nearby areas from southeastern West Virginia to south-central Pennsylvania has an organic content sufficiently high and a thermal maturity sufficiently moderate to be considered for a shale gas play. The organic matter-rich Marcellus Shale is present throughout most of the synclinorium, being absent only where it has been eroded from the crest of anticlines. Geochemical analyses of outcrop and well drill-cuttings samples indicate that variable levels of hydrocarbons have been generated and expelled from the kerogen originally in place in the mudstone. The mineralogical characteristics of the Marcellus Shale samples from the study area are conducive to a continuous resource play, but the Middle Devonian strata are folded, faulted, and moderately to heavily sheared in the Broadtop synclinorium.

The presence of conventional anticlinal gas fields in the study area that are productive from the underlying Lower Devonian Oriskany Sandstone suggests that an unconventional (or continuous) shale gas system may be in place within the Marcellus Shale in the study area. Results of this study indicate that the Marcellus Shale in the Broadtop synclinorium generally is similar in organic geochemical nature throughout its extent, and based on the sample analyses, there are no clearly identifiable high potential areas (or “sweet spots”) in the study area. This report contains analyses of 132 outcrop and well drill-cuttings samples.

First posted May 7, 2015