Lotfi Fourati¹, Fraj Hammouda², Chokri El Maherssi², Moncef Saidi²

(1) ETAP, Tunis, Tunisia
(2) ETAP, 1002 Tunis, Tunisia

ABSTRACT: Ypresian Bou Dabbous Formation: an Active Petroleum System Within the Thrust Belt Zone in Northern Tunisia- North Africa

In Northern Tunisia, the Ypresian Bou Dabbous limy Formation is one of the main exploration targets. It is generally well sealed by the overlying Late Eocene Souar shales. It produced oil in the Belli field (Cap Bon area) and the recent Al Manzah discovery confirms its potential. During the Ypresian, the tectonic activity has controlled the sedimentation resulting in several carbonate lithofacies, from the platform in the south into the basin in the northwest. The basin facies consists of dark gray to black organic rich Globigerina limestones. It appears to be a good source rock formation with a good petroleum potential (up to 16kg/t of rock) and high T.O.C. contents (up to 3.5%). The organic matter is particulary well preserved and of type II origin. The maturity level is ranging betwen oil and gas windows; the peak oil generation was reached during the Late Serravalian to Early Tortonian and the main hydrocarbon expulsion phase took place at the same period and appears to be directly related to the thrusting event. The platform facies corresponding to the bioclastic limy wackestone to packstone texture, displays a good reservoir quality with well developed primary depositional matrix micropores, associated with secondary moldic and vuggy porosities. The measured porosity values range from 8 to 16% and the permeability is greatly improved by fracturing/faulting reaching locally 4.5 Darcies in Belli Field. More intensive exploration activity in this area, may confirm the Ypresian Bou Dabbous as an important hydrocarbon play in northern Tunisia.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado