A PRELIMINARY EVALUATION OF THE GEOTHERMAL ENERGY POTENTIAL FOR SOUTH CAROLINA

With the continued rising cost and scarcity of fossil fuels and concerns about global climate change, states are re-evaluating the potential for and feasibility of geothermal sources of energy. This study focused on the geothermal potential of Early Paleozoic felsic gneisses of the Inner Piedmont and Middle Paleozoic granitoids of the Carolina terrane of South Carolina. Determining the geothermal potential of these felsic rocks required knowledge of surface heat, heat flow, heat production potential, and the volume of rock at depth from geophysical information. Surface heat and heat flow are known for the region and the heat production potential was calculated based on abundance of radioactive elements and rock density. The volume at depth of the rocks investigated remains undetermined. Published analyses of U, Th, and K from the geologic literature for the Carolina terrane and unpublished data for the Inner Piedmont (Ranson, pers. com.) of South Carolina were used to calculate heat production values and associated temperatures. Temperature values assume these rocks, all of which are allochthonous, are floored at a depth of 7.8 km, which is the regional depth to basement. For the Carolina terrane heat production potential for the Liberty Hill-Kershaw granite range from 1.56 to 4.22 μW/m³ with corresponding temperatures from 128 to 159°C. Values for the Winnsboro granite range from 1.93 to 4.46 μW/m³ with corresponding temperatures from 133 to 162°C. An example from the Inner Piedmont is the Table Rock gneiss, which has heat production potential ranging from 0.60 to 7.41 μW/m³ with corresponding temperatures from 127 to 196°C. Uncertainties in the temperatures result from lack of detailed geophysical data regarding the volume of the rock body and its homogeneity at depth. Our results compare favorably with those previously measured or calculated for South Carolina. In conclusion, preliminary results for felsic igneous and metamorphic rocks from South Carolina, based on the current available drilling and heat mining technology, show there is insufficient heat to provide a significant commercial geothermal resource. Continued research will be directed at 1) understanding the volume of rock masses with the highest heat production potential from geophysical data; and 2) granitic basement beneath the coastal plain.