Investigation of low enthalpy geothermal resources in the transitional geological environment: a pathway to Nigeria's...

Nigeria faces a significant energy deficit (61.2% electricity access), hindering progress toward SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action). Despite geothermal potential, comprehensive assessments of low-enthalpy resources (that is, subsurface temperatures below 100 ℃) in transitional geological environments (TGEs) - basement-sedimentary contact zones with mixed conductive-advective heat transfer - remain underexplored. This study uses high-resolution aeromagnetic data interpretation with statistical modeling to delineate geothermal potential within the Egbako-Share axis of North-Central, Nigeria. Spectral analysis adopting centroid depth technique from 40 overlapping blocks was employed to estimate Curie Point Depths (CPD), geothermal gradients (GTG), and heat flow (HF). Statistical modeling - including correlation analysis, multiple regression, PCA, and spatial autocorrelation (Moran's I, Getis-Ord Gi*) - provided a robust framework for resource assessment and risk evaluation. The analysis revealed significant geothermal resources with CPD ranging from 26 to 46 km (mean: 38 ± 6 km), GTG of 13-23 °C/km (mean: 16 ± 2 °C/km), and HF values of 31-57 mW/m² (mean: 39 ± 6 mW/m²). Strong negative correlations between CPD and both GTG (r = -0.892, p < 0.001) and HF (r = -0.891, p < 0.001) were established, with the regression model explaining 79.5% of HF variance. PCA identified 12 high-potential geothermal zones for low-enthalpy development. Under a conceptual scenario assuming full development of all 12 zones, modelled capacity could range from approximately 15 to 25 MW, with scenario-based annual CO₂ emission reductions of 85,000-140,000 t/year (subject to confirmatory drilling and feasibility studies), supporting Nigeria's SDG 7, SDG 13, and related development targets.