The National Agency for the Valorization of Hydrocarbon Resources "ALNAFT"

Non conventional

Shales reservoir

The plays shales identified at the scale of all the basins of the Saharan domain are as follows:

Mother rock architecture in the Saharan basins.

The Silurian play

The Silurian is represented on the scale of the entire Saharan platform, by an important clayey formation of a distinctly marine  environment, little agitated and reducing, and whose thickness can reach 1000 meters, in places; its richness in organic matter is regionally characterized from good to very good, with a residual TOC sometimes reaching 5%

- Silurien Basal or “Silurien Hot Shale”: the thickness at the scale of all the basins of the Saharan domain varies from around thirty meters, until reaching 300 meters in places, the measured TOC values ​​are in the 2-6% fringe, with a state of maturity varying from overmature in the western basins to the gas phase going east.

- Silurien Hot Shale 2: The thickness of this interval varies from about 40 to 100 meters, with a TOC oscillating from 2 to 4% and a state of maturity varying from the oil phase to dry gas.

silurian_thickness_map_61b1dc2a7ff585.69874997.jpg

Silurian thickness map (Alnaft study, carried out by Beicip-Franlab).

 

 The Devonian play: represented by the Frasnian-Famennian interval

 The Frasnian is represented by internal marine platform deposits passing to deep marine and varying in thickness from a few meters; at the level of the Tindouf and Reggane basins and the center and south of the Illizi basin a few hundred meters in the In Salah region, to reach 300 meters north of the Berkine basin; this evolution suggests a setting up of prograding criniforms, isolating muddy carbonate systems, passing to an open marine domain, more clayey.

This interval has a useful height oscillating from 50 to 200 meters depending on the basin, with measured TOC varying from 2 to 8% and a state of maturity ranging from immature on the West / North-West part of the Berkine basin, reaching the oil phase to the east of it, while it evolves into a dry gas phase (up to oil) in certain places of the Timimoun and Ahnet basins.

carte_epaisseur_du_frasnien_radioactif_61b1dcb3b6fae1.37449317.jpg

Carte d’épaisseur du Frasnien radioactif (étude Alnaft, réalisée par Beicip-Franlab).

 

Tights reservoirs:

The compact reservoirs at the scale of the Saharan basins are mainly attributed to the Cambrian and Ordovician intervals, where they are predominantly clastic; as well as the compact Devonian reservoirs, of variable nature (clastic and carbonate); mainly present in the basins of western Algeria.

 

The Cambro-Ordovician :

corresponds to periglacial deposits, however the Terminal Ordovician corresponds to glacial deposits

- The Periglacial is represented by fluvial deposits evolving towards fluvio-deltaic tidal influence and whose thickness can reach 400 meters at the level of the central northern deposits of Berkine, Oued Mya ..., this one is reduced to less 50 meters in places, following the tectonic replay of the blocks or the Hercynian Discordance; this interval has average porosity values oscillating between 2 and 9%.

- The glacial represented by the Late Ordovician, occurs mainly in quartzites from glacial valleys, and whose average porosity is of the order of 3%, which can reach 9%.

 

The Devonian :

which exhibits great variability both in thickness and in terms of facies, corresponds to river-estuarine groups dominated by swell, connected to an open marine domain; the average porosity of the intervals of interest oscillating between 4 and 7%.