THERMAL AND BURIAL HISTORIES OF NORTHERN DEPOBELT IN THE NIGER DELTA NIGERIA USING WELL-LOG DATA
Journal: Pakistan Journal of Geology (PJG)
Author: Chika Vincent Okorocha, Stephen Olushola Oladosu, Raphael Ehigiator -Irughe
This is an open access journal distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Well-log data from four wells located in Northern Depobelt in the Niger Delta were used for the interpretation of Thermal properties, burial history, and subsidence rate, using Petromod and Excel softwares. The geothermal gradients in wells -1, -2, -3 and -4 are 1.247oC/100m, 1.792oC/100m, 2.232oC/100m and 1.862oC/100m respectively, based on an average surface temperature of 27°C. The average geothermal gradient 1.767oC/100m for the field of study. Thermal conductivity values were highly variable with depth with values of 2.36Wm-1K-1, 2.27Wm-1K-1, 2.35Wm-1K-1, and 2.55Wm-1K-1for Wells 1, 2, 3 and 4 respectively. The heat flux obtained for the wells are accordingly 30.73mWm-2, 40.57mWm-2, 50.53mWm-2, and 42.19mWm-2. There was the general trend of the massive sandstones in the upper layers, characteristics of the Benin formation into an alternation of both sandstone and shales characteristic of the Agbada formation, followed by an increase in shale percentage down the series. The bottom of the Benin/top of Agbada boundaries for the four wells are about 1524.0m, 1066.8m, 1981.2m and 1371.6m for Wells 1, 2, 3 and 4 respectively. The burial gradient decreases with age. Rapid subsidence episode took place between the Middle Pliocene at 3.5Ma which lasted till the Early-Pleistocene creating accommodation for the deposition of sediments with an average thickness of 1066.57m.