More than 1,000 well logs from the Niger delta sedimentary basin were examined for temperature-data quality. Most measurements were made within 4 to 8 hours of cessation of mud circulation. Such nonequilibrium temperatures were corrected to approximately true formation values by applying a numerical solution to a modified Lachenbruch-Brewer's equation. The subsurface temperature distributions based on both the raw and corrected temperature data, when presented as geothermal gradient maps, show that values are lowest over the center of the Niger delta, approximately 0.7 to 1.0°F/100 ft, and they increase to about 3°F/100 ft in the Cretaceous rocks on the north.

The geothermal gradient map in the Niger delta could be used in the application of the hydrocarbon liquid-window concept for oil exploration. It reveals that theoretically there is a considerable thickness of potentially hydrocarbon-bearing interval in the delta region that is unexplored by current drilling programs.