Abstract
Wireline logs from 14 oil wells from the Nigerian sector of the Chad Basin were analyzed and interpreted to estimate the heat flow trend in the basin. Geothermal gradients were computed from corrected bottomhole temperatures while the bulk effective thermal conductivity for the different stratigraphic units encountered in the wells were computed from the sonic logs data. The heat flow values were then calculated. A corrected average geothermal gradient of 3.4 oC/100 m and a regional range of 3.0 to 4.4 oC/100 m were obtained. A porosity range of2 to 79 % and average of 35 % were computed for Chad Basin Nigeria. Also the thermal conductivities vary from 1.70 and 3.11 Wm-1 oC-1, with an average value of 2.35 Wm-1 oC-1 computed for the various wells in the basin. A large variation in heat flow was recorded within the basin. Mean heat flow values computed for the basin vary from 63.6 to105.6 mWm-2, with a simple average of 80.6 mWm-2. Although there is no distinct trend on heat flow within the basin, the computed heat flow values are relatively lower at the southwestern and northeastern axis of the basin. And the values obtained in this study compared favorably with those of other world sedimentary basins (including NigerDelta) that are of similar history with the Chad Basin, suggesting that the Nigerian Chad Basin is a possible petroliferous basin.
Highlights
The present day national petroleum reserves asset of about 32 billion barrels of oil and 170 trillion standard ft3 of gas (Obaje et al, 2004), are derived solely from the onshore and offshore of Niger Delta Basin
Though the available data vary in completeness and quality, this study has helped to increase our knowledge and understanding of the geology, petroleum prospect and potentials of the Chad Basin by establishing the thermal conductivity and heat flow values of the basin
The computed heat flow values for all the oil Wells in the basin suggests that its sediments should be thermally mature enough to generate hydrocarbons; with necessary exploration precautions being put in place future discovery of oil and/or gas in commercial quantity is possible in the Nigerian Chad Basin
Summary
The present day national petroleum reserves asset of about 32 billion barrels of oil and 170 trillion standard ft3 of gas (Obaje et al, 2004), are derived solely from the onshore and offshore of Niger Delta Basin. Though the available data vary in completeness and quality, this study has helped to increase our knowledge and understanding of the geology, petroleum prospect and potentials of the Chad Basin by establishing the thermal conductivity and heat flow values of the basin. Porosities in Chad Formation vary between 3.12 and 79.0% with an average value of 44.7%.
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