Geophysical Characterisation of Hydrothermal Systems for Geothermal Energy Development in Nigeria

This study develops an original geophysical characterisation framework for identifying, imaging, and evaluating hydrothermal systems in Nigeria, with the aim of advancing the country's geothermal energy resource knowledge from a near-zero base. Nigeria's geothermal energy potential is poorly characterised despite the presence of volcanic fields on the Jos Plateau, elevated heat flow in the Chad Basin, and numerous hot spring occurrences. Developing geothermal energy, particularly for direct-use heating and small-scale power generation in rural areas, requires systematic geophysical investigation of potential hydrothermal systems. This study develops an integrated multi-method geophysical characterisation workflow combining MT, gravity, magnetic, and seismic methods specifically optimised for hydrothermal reservoir detection in Nigerian geological contexts. The workflow is applied at three target sites: the Wikki Warm Springs in Bauchi State, a potential volcanic hydrothermal system on the Jos Plateau, and a high heat flow anomaly in the Chad Basin. At each site, combined MT (18 stations), ground gravity (35 stations), magnetics (250 stations at 25-metre spacing), and active seismic (2 profiles) data are acquired and jointly interpreted. Geochemical sampling of thermal waters provides temperature and geochemical constraints. Findings reveal at the Wikki Springs site a combined geophysical anomaly pattern (conductive MT anomaly, gravity low, magnetic low, low seismic velocity) consistent with a partially sealed, hot, saline hydrothermal reservoir system at 200 to 800 metres depth. Temperature gradient well modelling predicts temperatures of 80 to 120 degrees Celsius at 500 metres, suitable for binary cycle power generation. The study contributes an original geophysical characterisation framework for Nigerian geothermal exploration and recommends targeted temperature gradient drilling at the Wikki Springs site.

Keywords: geothermal energy, hydrothermal systems, geophysical characterisation, Nigeria, volcanic geothermal.