A. M'Rabet1,
M.Hedi Acheche1,
F. Belkhadi1,
N. Gharieni1
(1) Etap, 1002 Tunis, Tunisia
Abstract: Upper Jurassic-Mid Cretaceous Petroleum Systems
in the
south Gulf of Gabes Peri-Alpine Basin, Tunisia, North Africa
The Upper Jurassic to Mid-Cretaceous sandstones and carbonates are exploration targets in the South Gulf of Gabes Basin, a wide subsiding Mesozoic basin in southeastern Tunisia that resulted from Early Mesozoic rifting and having been affected by Mid-Late Cretaceous to Tertiary Alpine compressional stresses, with significant strike slip movements.
In the South Gulf of Gabes
Basin, at least three fields (Ezzaouia, El Biban and Robbana) are producing
oil, indicating the existence of active petroleum systems
including proven
clastic and carbonate reservoirs, good mature source rocks and a variety of
trap
types
. Clastic reservoirs include the Upper Jurassic M'Rabtine and the
Neocomian Meloussi sandstones. The pay zones, tens of meter thick, are
represented by shallow marine fine grained sandy intervals exhibiting fair to
excellent reservoir properties. The seals are provided by intraformational
shales and anhydrites. Carbonate reservoirs correspond to the Cenomanian Zebbag
bioclastic limestones and dolomites, having fair to good porosities and sealed
by intra-Zebbag evaporites or Upper Cretaceous-Paleocene shales. Source rocks
are the Callovian shales and the Aptian marls, in addition to organic-rich
shale interbeds within the Late Liassic and Triassic organic-rich carbonates.
Thermal modelling indicates that these source rocks have expelled most of their
oil charge during Tertiary times; vertical migration from the generative areas
being provided by deep seated faults.
Trap
types
especially include
fault blocks, faulted anticlines and salt related structures. Most of these
traps originated during Late Cretaceous compressional stresses. Reactivation
that occurred during Tertiary tectonic events have not affected the
trap
integrity.
Large portions of the South Gulf of Gabes Basin remain under-explored including both awarded exploration concessions and open acreage areas.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana