Ordovician shallow-marine tidal sandwaves in Algeria – the application of coeval outcrops to constrain the geometry and facies of a discontinuous, high-quality gas reservoir

A high-quality, discontinuous gas reservoir interval in the Tiguentourine field of Algeria's Illizi Basin has been characterized through comparison with coeval outcrops in Tassili n'Ajjer. The study reveals that this thin (<12 m), shallow-marine sandstone unit—unresolvable on seismic data and variably developed subsurface—exhibits tidal sandwave geometries with wavelengths >100 m, documented via Landsat imagery and outcrop analysis. These findings explain the reservoir's patchy distribution and high exploration risk by linking facies variations to modern marine analogs. The research bridges subsurface reservoir modeling with surface exposures, offering critical insights for predicting this challenging target in Ordovician proglacial settings.

Hirst, J. P. P. (2016). Ordovician shallow-marine tidal sandwaves in Algeria – the application of coeval outcrops to constrain the geometry and facies of a discontinuous, high-quality gas reservoir. Geological Society, London, Special Publications, 436(1), 135–150. https://doi.org/10.1144/sp436.11