Publisher: Bachudo Science Co. Ltd

Effects of Lithology On Geothermal Gradient In The South-East Niger Delta, Nigeria.

Etim D. Uko, Arobo R. C. Amakiri, Kingsley D. Alagoa
KEYWORDS: Subsurface temperature, lithology, temperature gradient, thermal conductivity, basin, fluid flow.


A study of the effects of lithologic formations on geothermal gradients is carried out in the south-east Niger Delta, Nigeria, using continuous temperature and lithologic log data from closely-spaced petroleum wells. The gradient profiles obtained for the deep wells, logged to depths between 6500 ft (1981m) and 8500ft (2591m), were observed to have markedly different geothermal gradients with corresponding vertical lithologic units. For the upper sandy lithology, the Benin Formation, the temperature gradient ranges between 0.80 °F/100 ft (1.456 °C/100ry,) and 1.22 °F/100 ft (2.220 °C/100m) with an average of 1.03 °F/100 ft (1.875 °C/100m). For the paralic shaly Agbada Formation segment, the temperat_ure gradient ranges between 0.92 °F/100 ft (1.674 °C(1-00m) and 1.87 °F/100ft (3.403 °C/100rn) with an average of 1.40 °F/100ft (2.548 °C/100m). The depths of Benin Formation were observed to vary between 4200ft (1280 m) and 5400ft (1879 m) Geothermal gradients are thus observed to increase with depth and shale units.   

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