oa Prediction of Hydrocarbon Generation from Lower Silurian Hot Shale Source Rocks by Using Bulk and Compositional Kinetics Results in the Murzuq Basin, SW Libya

Organic-rich “hot shales” of the Lower Silurian Tanezzuft formation are regarded as the principal<br>source rocks for Palaeozoic oil fields in North Africa. Thus, the evolution of the petroleum system of the<br>Murzuq basin, Southern Libya, is largely controlled by the lateral extension, thickness, organic<br>geochemical characteristics and maturity of the Tanezzuft hot shale. In this context the petroleum<br>generation potential of Tanezzuft hot shale samples from the Murzuq basin was studied by geochemical<br>and petrological methods and a numerical modelling study was performed taking into account the<br>structural evolution and thermal history of this basin[1].<br>Core and cutting samples of the Lower Silurian interval were selected from two wells of the northern<br>and central part of Murzuq basin. High TOC contents and HI-values from Rock-Eval pyrolysis indicate<br>organic-rich source rocks with moderately hydrogen-rich organic matter, classified as Type II kerogen,<br>at different maturity levels.<br>To enhance the geochemical source rock characterisation as well as to predict hydrocarbon phases and<br>generation [2], bulk and phase kinetics were performed by open system- and closed system pyrolysis.<br>The bulk kinetic analysis confirmed the early to mid mature level for the northern part and immature to<br>early mature level for the central part of the basin. The activation energy distribution for the samples is<br>characterised by a smooth bell-shaped, Gaussian-like distribution, typical of marine type II kerogen.<br>Temperature and timing of petroleum generation were calculated using activation energies and<br>frequency factors with a linear geological heating rate of 3.3 K/my [2].<br>The compositional kinetic analysis was performed to assess the composition of generated petroleum.<br>The results show that 75 % of hydrocarbons is generated as oil and 25 % as gas fraction. The gas-oil<br>ratio was calculated and found to increase with increasing the maturity.<br>[1] Belaid, A., B. Krooss and R. Littke, 2009, Thermal history and source rock characterization of a<br>Palaeozoic section in the Awbari Trough, Murzuq Basin, SW Libya, Marine and Petroleum Geology, doi:<br>doi:10.1016/j.marpetgeo.2009.06.006.<br>[2] di Primio, R., Horsfield, B., 2006, From petroleum type organofacies to hydrocarbon phase<br>prediction. AAPG Bulletin, v. 90, no. 7, p.1031 - 1058