Central
Tunisia and Related Petroleum Systems
Derbel Damak,
Fayrouz1 (1) Entreprise Tunisienne d'Activités Pétrolières, Montplaisir, Tunisia
Central Tunisia belongs to the foredeep domain.The studied
region lies especially on the Central Tunisian Atlas.It's
characterized by a relatively important subsidence during Mesozoic.Since
Lower Cretaceous, an alignement
of horsts took place. A raising of the whole region
began in the Uppermost Cretaceous. This structural evolution led to an
alternating silicoclastic deposits and carbonate
platforms that allowed several Mesozoic and Cenozoic petroleum systems in the
region. We can distinguish proven reservoirs as the reefal
Aptian Serj producing oil
at Douleb, Semmama and Tamesmida fields, the bioclastic Vraconian limestones F2B unit
producing at Tamesmida oil field. Potential
reservoirs in this area are the Upper Jurassic Nara limestones,
the Upper
Valanginian to Hauterivian
dolomitic Douleb 101, the Turonian Bireno carbonates, the Coniacian oolithic and dolomitic Douleb limestones, the Campano-Maastrichtian
turbiditic Abiod limestones and the Ypresian Nummilithic El Garia limestones. Most reservoirs are sourced by Cenomano-Turonian laminated and organic rich Bahloul limestones and/or Late Albian(ss) Mouelha marls and/or Fahdene Albian shales. Neocomian Melloussi to Mrhila deposits,Senonian Aleg, Upper Maastrichtian to
Lower Paleocene El Haria and Oligo-Mio-Pliocene
deposits are mostly overspread and constitute a good seals for the cited
objectives. The NE-SW oriented surface anticlines and syclines
in the Central
Atlassic Tunisia show outcrops from
Triassic to recent deposits.These features are
seemingly truncated by conjugated NW-SE trending grabens.
Thus, several interesting trap styles are recognized in this area: in the grabens, in the horsts located at the borders of the grabens and in the eventually prospects corresponding to
the surface anticlines with more or less geometric similarities. Basin modeling
indicates a Tertiary expulsion that's in good timing with prospect ages. These
good attributes associated with more seismic acquisition should better the
exploration succes ratio in the region.