Palynofacies Analysis of Selected Organic-rich Shales from Libyan Sahara: Implication to Palaeoenvironment and Hydrocarbon Source Rock Potential

Abstract

Palynofacies analysis was carried out on three (3) packages of shale-cutting samples derived from a well drilled within Gadames Basin. These included: the upper package (Carboniferous at 5,530 ft), the middle package (Carboniferous/Devonian at 5,600 ft and 5,780 ft), and the lower package (Devonian at 6,700 ft). Two palynofacies were identified: "P-1", involving the upper and middle packages (Carboniferous/Devonian), and "P-2", involving the lower package (Devonian). P-1 and P-2 were considered to form one "palynofacies association" located at a mud-dominated oxic shelf (distal shelf) and are analogous to other palynofacies from other countries that are characterized by the dominance of terrestrial upon marine palynomorphs and moderate to low phytoclasts and AOM respectively that typically deposited within a shoreline zone (probably fluvial-deltaic source or marginal marine environment). Spore color index "SCI" evaluation for source rock and thermal maturation, in turn, indicates early mature oil/gas prone (kerogen type II>III) to post mature kerogen type III>IV "gas prone" for the studied cutting sample packages.