Organic Geochemistry of the Ypresian source rock and oil seeps from thrust belt zones in the central southern Tethys: Northern Tunisia

Abstract

The thrust belt area of North Africa is an important hydrocarbon province in the Mediterranean Sea, Sicilian area and northern Tunisia. In spite of the long history of exploration in northern Tunisia, few geochemical investigations were performed until now. The generative potential, depositional environments, thermal maturity and oil seeps of the Ypresian Bou Dabbous organic-rich facies of northern Tunisia thrust belt system was characterized by both Rock Eval and molecular analyses. The present study demonstrates that the Bou Dabbous formation display variable source rock characteristics within the different Tellian units, outcropping south of the nappes zone, Nefza tectonic window and along the major thrust contacts such as Cap Serrat-Ghardimaou Master Fault. The paleo-tectonic units in the area show some similarities with equivalent facies in Mediterranean Sea and Sicilian. Organic matter content and petroleum potential are poor to fair (up to 1.95% and 6 kg of HC/t of rock respectively) and marine type II kerogen. An increasing SE-NW maturity gradient is well documented in the study area. In deed, the Bou Dabbous facies are : (1) marginally mature in the front of the nappes (Tellian Unit of Kasseb domain), (2) mature to late mature within Nefza-Ain Allega tectonic windows and (3) overmature a long the Cap Serrat-Ghardimaou Master Fault. In addition, Oil/Oil and Oil/source rock correlations based on biomarker and carbon isotopic composition shows a positive genetic correlation between the oil seeps and the Bou Dabbous source rock.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015