Murzuq Basin Source Rocks

Malvin Bjorøy and Peter B. Hall
Geolab Nor AS, Trondheim, Norway

Several hundred source rock samples and a number of oils from the Murzuq Basin in southern Libya have been analysed. All routine organic geochemical techniques were employed in the study, including, saturated and aromatic GC and GC-MS (SIR) and stable carbon isotope analysis.

Four potential Palaeozoic source rocks, Marar, Awaynat Wanin, Tanezzuft and Hot Shale Formations are recognized. From the standpoint of oil potential the Carboniferous Mrar Fm. appears to be mainly poor and gas prone, while the Devonian Awaynat Wanin Fm. has some oil potential in parts of the basin. The Silurian Tanezzuft Fm. has mostly poor to fair oil potential while the Silurian Hot Shale sequences have good to rich oil potential.

In the north-west, the depth of the oil window is considerably influenced by the Gargaf Uplift and the oil window in this area is mostly very shallow. This oil window was only effective prior to the Jurassic. From the the central part of the basin northwards there is an increase in maturity of the Hot Shale from early mature-early oil window mature in the south to late mature-condensate window mature in the north. In the south-east there has been little of the Jurassic uplift experienced in the north and the Tanezzuft/Hot Shale is mostly within the oil window.

The main characteristics of the different source rocks and oils are discussed with emphasis on the biomarker and isotopic composition.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery