Abnormality of geothermal gradients in Iraqi western desert inferred from borehole temperatures

Abstract

Abstract Geothermal gradient is an important tool in petroleum exploration and critical to several reservoir evaluations. Borehole Temperature data from 14 wells are utilized to find the geothermal tendency of the Western Desert in Iraq. The discrepancies in geothermal gradients throughout the area are a consequence of variability of sediment’s thermal conductivity, direction of groundwater flow, fault pattern, and heat generation. High value converts liquid hydrocarbon to dry gas and low value will not help organic matter to reach maturity level. The lowest gradient within the units above Palaeozoic Era’s section is 12.2 °C/km for well KH-9/7 in the eastern part of the area and the highest is 31.3 °C/km for well KH-5/4 in the middle part of the region. Whereas, the highest geothermal gradient which is 61.0 °C/km within the Palaeozoic section is recorded within Akkas Formation in 2100-2350 m subsurface. The mean geothermal gradient in Western Desert is 26 °C/km within the units younger than the Palaeozoic, but this average rises up to 40 °C/km within Palaeozoic units due to existence of Silurian hot shales and heat flow from the Proterozoic section especially from Halaban Group andesites.