HYDROCARBON SOURCE ROCK POTENTIAL OFLATEST ORDOVICIAN – EARLIEST SILURIAN TANEZZUFT FORMATION SHALES FROM THE EASTERN KUFRA BASIN, SE LIBYA

G. Meinhold1,2,*,  A. G. Whitham1, J. P. Howard1,  J. C. Stewart1, Y.  Abutarruma3 and B. Thusu4

1 CASP, University of Cambridge, West Building, 181A Huntingdon Road, Cambridge CB3 0DH.

2 Dept. of Sedimentology and Environmental Geology, University of Göttingen, Goldschmidtstrasse 3, D-37077 Göttingen, Germany.

3 Mellitah Oil & Gas B.V., Dat Al Imad Complex Tower 5, Floor 13, P.O. Box 91651, Tripoli, Libya.

4 Maghreb Petroleum Research Group, Dept. of Earth Sciences, University College London, Gower Street, London WC1E 6BT.

* Corresponding author, email: guido.meinhold@geo.uni-goettingen.de

This paper summarizes the results of Rock-Eval pyrolysis data of 43 shale samples collected from the latest Ordovician – earliest Silurian (Tanezzuft Formation) interval in the CASP JA-2 well at Jebel Asba on the eastern margin of the Kufra Basin, SE Libya. The results are supported by analysis of cuttings samples from an earlier well of uncertain origin nearby, referred to here as the UN-REMSA well. The Tanezzuft Formation succession encountered in the JA-2 well can be divided into three intervals based on Rock-Eval pyrolysis data. Shales in the shallowest interval (20 – 46.5 m depth) are altered probably by weathering and lack significant amounts of organic matter. Total organic carbon (TOC) contents of shales from the intermediate interval (46.5 – 68.5 m depth) vary between 0.19 and 0.75 wt%. Most samples in this interval have very limited source rock potential although a few have Hydrogen Index (HI) values up to 378 mg S/2g TOC. Tmax values of 422 – 426°C indicate the organic matter is immature. Shales from the deepest interval (68.5 – 73.9 m depth) are diagenetically altered, perhaps by fluids flowing along a nearby fault or along the contact between the Tanezzuft Formation and the underlying Mamuniyat Formation and apparently lack any organic matter. Cuttings samples from the UN-REMSA well have TOC contents of 0.48–0.87 wt%, HI values of 242–252 mg S2/g TOC, and Tmax values of 421–425°C. These results offer little support for the presence of the basal Silurian (Tanezzuft Formation) source rock which is prolific elsewhere in SW Libya and eastern Algeria and, together with the overall immaturity of the equivalent section, reduces the probability of finding major oil reserves in the eastern part of the Kufra Basin.:

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