--> Abstract: Devonian Play Attributes In Southern Tunisia, Ghadames Basin, North Africa, by M. H. Acheche, A. M'rabet, R. Ghenima, and H. Ghariani; #90928 (1999).

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M. H. ACHECHE, A. M'RABET, R. GHENIMA and H. GHARIANI
ETAP, Tunis, Tunisia

Abstract: Devonian Play Attributes in Southern Tunisia, Ghadames Basin, North Africa

The Devonian play is under-explored in the Tunisian part of Ghadames Basin, although oil and gas shows were encountered in several wells and one an oil discovery was made The Emsian Ouan Kasa Formation is the principal pay zone in the Devonian play. it consists of quartzitic sandstones, fine grained and deposited in shallow marine environment. It exhibits fair to good reservoir quality and is well sealed by Late Devonian thick shales. Additionnal reservoir horisons are provided by the Siegenian Tadrart and Strunian Tahara sandstone Formations. Geochemical fingerprinting indicates that oil and gas discovered in the Ghadames Basin originated from two major sources rocks : the Frasnian and basal Silurian hot shales. Their regional extent is controlled by the Hercynian-aged unconformity and associated erosion with a wider distribution of the Silurian source. Both sources have excellent generative capacity with TOC ranging from 2 to 15 % and HI between 400 and 700 mgHC/g TOC. Burial, thermal and petroleum generation models are constructed by ID Basin modeling for more than 25 wells and pseudo-wells. It indicates that generative areas moved trough time from the south to the north. Silurian source began generation in the Carboniferous with two significant episodes in the Jurassic and Cretaceous whereas the Devonian source yielded oil in the Middle Jurassic and achieved peak oil generation in Cretaceous to Tertiary. The generation generally postdates the trap development. Traps are faulted anticlines and pinch out.

In sum, the Devonian play has favorable attributes. The maturity levels and migration pathways together with seismically well defined traps are the keys of successfull exploration and new oil and gas discoveries in southern Tunisia.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas