THERMAL CONDUCTIVITY, THERMAL GRADIENT, AND HEAT FLOW ESTIMATIONS FOR THE SMACKOVER FORMATION, SOUTHWEST ARKANSAS

Subsurface thermal conductivity, thermal gradient, and heat flow are significant parameters when determining the feasibility of utilizing a geologic unit to generate industrial geothermal power. Core samples from 18 wells of the subsurface Jurassic Smackover Formation in southwest Arkansas were analyzed at the Arkansas Geological Survey where estimated thermal conductivity, thermal gradient, and heat flow values were determined. Thermal conductance of several samples was obtained using a KD2 Pro Thermal Analyzer at room temperature. Thermal gradients were estimated from Smackover borehole temperatures, and estimated heat flow was calculated from thermal conductance and thermal gradient values. Average estimated thermal conductance values for the Smackover Formation are greatest in northeastern Lafayette County at 2.57 W/m·K followed by southern Columbia and western Calhoun Counties at 2.47 W/m·K each. Northwestern Columbia and northeastern Lafayette Counties exhibit the highest estimated thermal gradient and heat flow with values averaging 3.29°C/100m and 63.8 mW/m², respectively. Interpretation of these parameters suggests that this area exhibits the highest geothermal potential for the Smackover Formation in southwest Arkansas. Investigations further characterizing the Smackover Formation, including in situ thermal properties and borehole temperature measurements, are recommended for future geothermal feasibility studies.