GEOTHERMAL GRADIENT ESTIMATIONS FOR THE ARKOMA BASIN IN NORTHWESTERN ARKANSAS

As a part of the National Geothermal Data System (NDGS) project, bottom hole temperature (BHT) and depth information was collected from over 1600 well logs created in the Arkoma Basin. This area of northwestern Arkansas is part of the Fayetteville shale gas play. Geothermal gradients for the area of interest were estimated using this BHT and depth data, and digital gradient maps were produced. Geothermal gradient is an important measurement when considering the feasibility of large scale geothermal energy production.

Estimations show that there is a potential area of higher geothermal gradient located in southwestern Sebastian County extending into northwestern Scott County. Geothermal gradient values in this area are estimated to range from 6.46^oC/100m to 10.23^oC/100m with depths ranging from 200ft to 2000ft. These values are significantly higher than those of the surrounding area, which were estimated to range from 2.48^oC/100m to 5.46^oC/100m and depths ranging from 200ft to 20000ft.

This increased geothermal gradient indicates that the area of study may be a potentially viable source for geothermal energy production. Further exploration of thermal conductivity values of the geologic formations in the area is recommended to clarify this potential.