A STRATIGRAPHIC AND PETROPHYSICAL STUDY OF IN-SITU GEOTHERMAL RESERVOIR QUALITY OF THE CAMBRO-ORDOVICIAN STRATA IN THE SUBSURFACE AT CORNELL UNIVERSITY, ITHACA, NEW YORK

Abstract

Geothermal energy is an attractive energy source which may significantly offset fossil fuels because of its potential to produce sustainable, widespread, and affordable heat. Cornell University is exploring the subsurface at its Ithaca, New York campus to access the naturally hot deep rocks and produce geothermal fluids for direct use as a thermal source with which to heat campus buildings. A reconnaissance fairway analysis of the geothermal potential of the Appalachian Basin revealed that rocks with suitable natural permeability and heat for geothermal reservoirs are likely to be at 2.3 - 3 km depth. This study investigates the in-situ geological properties and geothermal reservoir potential of the Cambro-Ordovician limestones, dolostones and sandstones underlying the Knox Unconformity at ~2.3 km to 2.8 km depth in Ithaca, New York. This new evaluation is based on repurposing geophysical well logs, drill cuttings and core reports, supplemented by new cuttings analyses, from 78 pre-existing hydrocarbon industry boreholes in central and western New York. Gamma ray, neutron porosity hydrogen index, density and photoelectric factor logs are utilized to derive estimates of the lithologies and porosity of the Cambro-Ordovician strata. Coupled with the logs are cuttings reports and analyses for the interpolation of depths and thickness through the construction of cross-sections and isopach maps. Three intervals of strata are identified as potential reservoirs: the zone at which the basal Ordovician Little Falls Formation limestone or dolostone is interbedded with the upper Galway Formation sandstone known as the Rose Run member in New York; the interbedded sand and dolomite beds of the Galway Formation informally labeled in this study as the Yellowjacket member in New York; and the feldspathic sandstones of the basal Ausable member of the Potsdam Formation. These occur at depths below Ithaca of roughly 2.55 km, 2.7 km and 2.8 km +/ 0.2 km, respectively.