CONNECTICUT GEOTHERMAL MAP SERIES: TOOLS FOR EXPLORATION AND DEVELOPMENT

The CT and MA Geological Surveys are collaborative partners in the National Geothermal Data Project funded by DOE through the Association of American State Geologists. The goal is to develop information to assist in locating State geothermal resources and provide data for better design of EGS systems in bedrock or unconsolidated sediments. The first 2 yrs of the investigation focused on data collection to explore the heat generating potential of CT bedrock and thermal conductivity (TC) properties of CT sediments. Rock chemistry, density, and TC were used to calculate heat production, heat flow, and thermal profiles at depth for >240 samples of 55 bedrock units. Heat production values (hpvs) were determined using concentrations of radiogenic (K, U, Th) and measured sample density. Heat flow values were determined using the calculated hpvs for the samples and hpvs of avg crustal material of New England (Rhodes, personal com., 2012). Thermal profiles at depths up to 6 km were generated using hpv, heat flow, and TC values for each sample. Results indicate that areas with highest heat flow values are in southeastern CT bedrock. 100 sediment samples were collected from 20 units targeted using the Surficial Materials and Quaternary Maps of CT. TC Measurements were made using a Decagon KD2-Pro Meter. Physical profiles of sediment (grain size, sand, silt, clay percent, bulk density, porosity) were created. Current efforts involve synthesis of calculated hpvs with direct heat flow measurements from existing geothermal installations to compile a geothermal resource map series. The series includes heat production, inferred heat flow, TC, and thermal profile maps for bedrock, and a TC map for sediments. These maps will assist geothermal contractors in site plan and system design. Heat production and inferred heat flow maps summarize model results for bedrock units. Thermal profile maps depict models of inferred temperature increases at depth, providing estimates for 3,4,5, and 6 km at specific locations, and provide depths needed to achieve desired temperature for either EGS or larger direct heat applications. TC mapping of sediments depict favorable areas for geothermal installations, and may be used in design of various ground source heat pump systems. All data and mapping is accessible via the National Geothermal Data System.