ESTIMATION OF POTENTIALLY EXPLOITABLE GEOTHERMAL RESOURCES IN THE BIDA BASIN, NIGERIA

Abstract

Geothermal resources are diverse, and they occur in a wide range of geologic settings. They are identified and exploited based on application of several different geological, geochemical and geophysical exploration methods. Direct measurements of subsurface temperature enable the estimation of key thermal parameters, including the geothermal gradient, heat flow, and geothermal energy resources. Thermal data from three primary sources: groundwater temperature, mean annual ground surface temperature (air temperature), and the thermal conductivity of rock samples; were analyzed to provide an updated assessment of subsurface thermal characteristics in the Bida Basin. Groundwater temperatures from 79 boreholes, combined with borehole depth and mean annual ground surface temperature, were used to construct a geothermal gradient map of the basin. The results reveal anomalies, with an average gradient of 3.58 °C/100 m, a maximum of 5.33 °C/100 m, and a minimum of 1.10 °C/100 m. Thermal conductivity values, measured from 24 unaltered hand samples representing the basin’s lithologies, range from 0.7839 W m⁻¹ K⁻¹ to 2.491 W m⁻¹ K⁻¹. The arithmetic mean heat flow is estimated at 57.17 mW m⁻². At different depth interval the amount of total geothermal energy varies from 231 GJ/m² to 1,073 GJ/m². The differentiation in accessible geothermal energy resources distribution is due to the different values of the geothermal gradients and subsurface temperature. The observed geothermal anomalies appear to be associated with the structural and tectonic influences of the Bida Basin. Mapping indicates that temperatures suitable for geothermal applications can be reached at economically viable drilling depths across significant portions of the basin, particularly in areas with above mean heat flow. These zones represent priority targets for further exploration and potential development.