After the first important Saharan stratigraphic test (Berriane) had shown encouraging results, S.N. REPAL intensified its reconnaissance studies. Seismic refraction and reflection, carried out together with field geology, located the structure of Hassi er R'mel, about 60 mi southwest of Laghouat oasis. In 1956 the HR-1 well was spudded, and led to the discovery of the gas field of Hassi er R'mel.

Located on the Cretaceous high zone of the M'zab area, the structure of Hassi er R'mel is a part of a zone which has been stable tectonically since the Cambrian.

Above the granitic basement, are Cambrian and Ordovician formations, which are covered by Silurian where pre-Triassic erosion was less important.

The oldest Mesozoic deposits lying unconformably on the Paleozoic, consist of Triassic sandstones, which are, from base to top: (1) a lower series (with andesite flows) which fills the topography of the pre-Triassic erosion surface. The top of the lower series is the C reservoir, which exhibits important lateral variations; and (2) two separate sandstone reservoir zones: B (noncontinuous) and A (continuous). Above the reservoirs are the salt-bearing Triassic (1,300 ft thick), Jurassic, (3,000-3,300 ft), and Cretaceous.

The structure at the top of the Triassic reservoir is anticlinal and has a north-northeast-south-southwest axis; its areal extent is about 1,000 sq mi.

An oil-water contact is at 5,016 ft (below sea level). Oil shows and minor production have been found in the Ordovician quartzites and Triassic sandstones. It is possible that there is a very narrow oil ring but so far this is unproved.

Though the structure is old, evidence has been found that the gas was trapped definitely during the Early Cretaceous.

Operated by SEHR (a subsidiary of S. N. REPAL and CFP[A]), the gas field of Hassi er R'mel has produced 380 Bcf of condensate gas since 1958. The reserves are now estimated at 70 trillion cu ft. Production could be increased considerably should the market requirements for gas be increased; because of the limited use for the gas at present, only five wells are now producing.

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