Biostratigraphy, Facies Models and Reservoir Architecture of Tin-Fouye Filed (Illizi Basin, Algeria)

By

 Henniche Messaouda¹, Rémi Eschard², Hamel Aîcha³, Jean-Noël Proust⁴

(1) SONATRACH, Boumerdès, Algeria (2) Institut Français du Pétrole, Paris, France (3) SONATRACH, Algiers, Algeria (4) Géoscience-Rennes-1, Rennes, France

 The "F6" reservoir dated Upper Silurian-Lower Devonian is a major reservoir unit in the Tin-Fouye field. A new sedimentological and biostratigraphical study based on core and outcrops description will be presented here:

This biostratigraphical study prove:

1-     the existence of Pridoli (Upper Silurian) in the Tin-Fouye area which is the equivalent of the "Talus à Tigilittes" formation in the Tassilis outcrops.

2-     the occurrence of a major unconformity on top of reservoir eroding the Emsian shale. The Givetian shales overlay directly Lower Devonian units.

The sedimentary facies models of the Silurian sequences correspond to: offshore shales, progradational wave and tide dominated ramps, braided, straight and meandering fluvial systems and tidal complexes. The Devonian sequences are principally related to straight and meandering fluvial systems evolving upward to coastal plain complexes ("C2" unit equivalent to "Trottoir" formation). The coastal plain consists of floodplain shales with isolated ribbon channels. Roots are frequent and are related to earliest development of vegetation. The Lower Devonian fluvial reservoir ("C1" unit, equivalent to "Barre moyenne" formation in the Tassili outcrops) makes a continuous but heterogeneous fluvial sand sheets with an irregular basal erosional surface. Thickness variation suggest the occurrence of a main SE/NW channel axis.