Thermal Maturity History and Source-Rock Characterization of a Palaeozoic Section in the Awbari Trough, Northern Part of the Murzuq Basin, SW Libya

Abdulmonem Belaid, Ralf Littke, and Bernhard M. Krooss
RWTH Aachen University, D-52056 Aachen, Germany

In some areas of the Murzuq basin, SW Libya, the Lower Silurian member comprises highly radioactive shales (hot shales) which are regarded as most significant factors controlling petroleum generation in the Murzuq basin. In this context, it was the goal of our project to study distribution and maturity of the Hot Shale in the framework of basin evolution. Organic geochemical, organic petrological and basin modelling methods were used to obtain a more thorough understanding. Four wells from the northern and central part of the Awbari Trough have been selected for this study. The Hot Shale contains mainly Type II kerogen with high TOC values ranging from 3 to 23 % which is considered as an indication for excellent source rock properties. A good petroleum potential is further supported by Hydrogen Indices varying between 220 and 380 (mg HC/g TOC). Numerical 1D basin modelling was performed for four wells in order to assess the thermal maturity of the Tanezzuft hot shale and its evolution through time. Mean random vitrinite reflectance results using vitrinite-like particles for Lower Silurian hot shale, pyrolysis Tmax values and fluorescence colours indicate that the hot shale is immature to early mature in the south and clearly more mature in the north of the basin. Other potential source rocks from Silurian Tanezzuft, Upper Devonian Awaynat and Lower Carboniferous Marar formations were analysed. Thermal history modelling indicates that the present-day geothermal gradients and heat-flows vary at different locations. The hot shale source rocks entered the oil window during mid-Cretaceous.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece