Ordovician proglacial sediments in Algeria: insights into the controls on hydrocarbon reservoirs in the In Amenas field, Illizi Basin

Ordovician proglacial sediments in the Tassili n'Ajjer region of Algeria serve as significant gas reservoirs in the In Amenas field, Illizi Basin. The study identifies that these deposits, characterized by poorly sorted argillaceous sandstones and high-density turbidity sandstones, were formed through catastrophic outflows from subglacial lakes, which incised subglacial tunnel networks and delivered sand to turbidite outwashes. The research developed depositional models using core data and analogous outcrops, revealing a lobate geometry for subsurface composite turbidites and indicating high-energy, stable outflows during ice retreat. This stability was likely due to grounding over the In Amenas granitic palaeohighs, which influenced the location of outwash fan apices and feeder channels. The study provides critical insights into the controls on hydrocarbon reservoirs in this region.

Hirst, J. P. P. (2012). Ordovician proglacial sediments in Algeria: insights into the controls on hydrocarbon reservoirs in the In Amenas field, Illizi Basin. Geological Society, London, Special Publications, 368(1), 319–353. https://doi.org/10.1144/sp368.17