THE UPPER DEVONIAN RHINESTREET BLACK SHALE IN THE SUBSURFACE OF WESTERN NEW YORK AND NORTHWESTERN PENNSYLVANIA – A POTENTIAL CONTINUOUS RESERVOIR

More than 430 geophysical well logs from western New York and northwest Pennsylvania were used to define the subsurface stratigraphy and reservoir potential of the heavily fractured, low permeability Upper Devonian Rhinestreet black shale. In this study, the top of the Rhinestreet is arbitrarily picked at that level where average bulk density < 2.6 gr/cc (TOC>2.3%). The Rhinestreet thickens from ~ 54 m along the Lake Erie shoreline in northern Erie County, New York, to > 100 m in McKean County, Pennsylvania. Thickness diminishes to the east into Allegany County, New York, as radioactive black shale transitions laterally to organic-lean gray shale and siltstone. The most organic-rich interval of the Rhinestreet shale, defined by an average bulk density < 2.55 gr/cc (TOC>3.2%), attains a maximum thickness (locally >45 m) in two areas: Erie County and a larger region that extends from central Chautauqua County into Cattaraugus County, New York. The carbonaceous interval thins rapidly to zero near the Cattaraugus-Allegany county line and more gradually to the west. Sparse thermal maturity data suggest that the Rhinestreet shale attains a vitrinite reflectance of ~1.0% in northwest Warren County, Pennsylvania, where the organic-rich interval is ~ 20-28 m thick, increasing eastward to 1.2% in central McKean County. Increasing thermal maturity toward the southern tier is hinted at by regional trends in the resistivity of the Rhinestreet shale relative to that of the immediately underlying organic-lean Cashaqua gray shale. The key to successful exploitation of the Rhinestreet shale lies in finding that location where thermal maturity can be optimized but not at the expense of diminished TOC.