Radioactivity and hydrocarbon generation potential of sediments, Gongola Basin, Nigeria

Samples taken from Well Kolmani-1 in the Gongola Basin in the Upper Benue Trough of Nigeria were studied to estimate the radiogenic heat generated and to analyze the possible impact of radiogenic heat on hydrocarbon generation potential of the sediments. Thirty-eight samples taken from the different formations at intervals of 73.2 m including sand, shale, coaly shale, sandy shale, and shaly sand were analyzed for 40K, 238U, and 232Th using the well calibrated NaI (Tl) Gamma Ray detector System. The results showed that the activity concentrations of the radio-nuclides varied significantly within the sediments. The 40K concentrations were the highest. The radiogenic heat produced ranges widely from 228.44 pW/kg to 1 412.82 pW/kg. In Well Kolmani-1, sands and sandy shale are low heat production sediments, while the shale, coaly shale and silty sands are medium heat production sediments, the potential source rock (shale and coaly shale) medium in heat production (750 pW/kg to 1 500 pW/kg), can produce liquid and gaseous hydrocarbons. It is estimated that the radiogenic heat from the sediments contributed about 10.9% to 20.9% to the total surface heat flux in the basin. Therefore, the radiogenic heat generated by the sediments contributed significantly to the total surface heat flux, and should be taken into consideration in the simulation of basin thermal evolution.