Heat flow analyses over Bornu Basin and its environs, Northeast Nigeria, using airborne magnetic and radiometric data: implication for geothermal energy prospecting

Abstract

ThestudypresentstheresultsoftheanalysesofheatflowforgeothermalenergyexplorationonareconnaissancebasiswithintheBornu Basinanditsenvironsusinganairbornemagneticandradiometricdataset.Thestudyareaisboundedwithlatitude11.00–13.00°Nand longitude 11.00–14.00°E with an estimated total area of 72,600 km2. The residual of the total magnetic field of the study area was subdividedintoseventy-one(71)overlappingspectralblocksof55×55and110×110km2 windows.SpectralanalysisbyfastFourier transform was performed on each overlapping block, and centroid depth and depth to the top of the magnetic source were obtained fromtheplotsofthelogofenergyagainstwavenumber.Theresultsshowedthatthecentroiddepthforthetwowindowsrangesfrom 6.28to17.70kmand7.83kmto23.50km,respectively.Similarly,thedepthtothetopofthemagneticsourceforthetwowindowsalso ranges from 1.66 to 6.12 km and 2.27 km to 6.37 km. The Curie point depth obtained for the two windows ranges from 8.78 to 32.69kmand10kmto42km,respectively.Theheatflowobtainedusinganaveragethermalconductivityof2.54Wm−1°C−1 ranges from 55.36 to 161.18 mWm−2 and 34.30 to 126 mWm−2 for the two windows, respectively. The maximum heat flow of 80 to 100 mWm−2 indicatesthatageothermalpotentialsourcewasfoundatthesoutheasternpartofthestudyareacorrespondingtoGwozaand Galdekore. The results of radiogenic heat flow (RHP) range from 0.80 to 2.47 μWm−3. The maximum RHP of 2.2 to approximately 2.5 μWm−3 is considered as radiometric signatures signifying probable geothermal potential sources, which could be found at the southeasternpartofthestudyareacorrespondingtoGwozaandGaldekore.Theagreementbetweenthetwoheatflowsobtained from the analysisofairbornemagneticandradiometricdatasetsisanindicatorthatthesoutheasternpartofthestudyareaisaviablesource for potential geothermal energy exploration.