POROSITY, PERMEABILITY AND PALEOTOPOGRAPHIC ANALYSIS: A GEOLOGICAL INTERPRETATION OF IN-SITU GEOTHERMAL RESERVOIR QUALITY AT CORNELL UNIVERSITY, ITHACA, NEW YORK

Cornell University is investigating deep geothermal energy to completely heat its main campus, which encompasses over 14 million square feet of buildings that require ~240,000 MW_th-hrs of heat. A reconnaissance fairway analysis was conducted in 2016 to survey the geothermal potential of the Appalachian Basin (https://bit.ly/2JHOiVH). This study revealed that, for Cornell, rocks with suitable natural permeability for geothermal reservoirs are likely found at 2.4 - 3 km depth, and rock temperatures at 3 km are expected to be 70 - 85^o C. The sedimentary units at these target depths span the Ordovician Trenton limestone to the Cambrian Potsdam sandstone that overlies the Precambrian basement. To assess the in-situ geological properties of these sedimentary units at Cornell, which is currently undrilled, geophysical well logs and reported cuttings lithologies from deep wells within 60 miles from the university are utilized as a primary data source. These data reveal the petrophysical and stratigraphic properties of the subsurface regionally across Central New York. Gamma, neutron and density logs are used to derive estimates of porosity, permeability, depths, and thickness of potential geothermal reservoirs at Cornell. Analyses revealed an interval of particular interest immediately beneath the Ordovician Knox Unconformity. To further analyze this interval, stratigraphic cross-sections from deep wells near Cornell are generated using Petra software to assess possible correlations of porosity with topography, such as paleohills and paleovalleys. To interpolate approximate depths to potential reservoirs, the stratigraphy derived from the wells are collated to construct isopach maps, and are coupled with log-correlations as a complementary analysis for increased accuracy. Preliminary results suggest that zones below Cornell that are more likely to have good geothermal reservoir properties include the bottom of the Ordovician Trenton Group limestone, the top of the Tribes Hill formation limestone or dolostone directly below the Knox unconformity, and a dolomitic interval at the bottom of the Galway formation, with depths of 2.3 km, 2.4 km, and 2.8 km +/- 0.2 km, respectively.