Triassic of Meseta Oranaise its Bordering Areas, North Algeria

The ‘Meseta Oranaise’ is located in the north-western part of Algeria. This area is between the Tellian basin to the North and the Atlasic basin in the South. The northern border is affected by faults network and folds. The southern border is characterized by a major fault “ Northen Atlasic Fault”. This area was structured as a horst since the Palaeozoïc. Stratigraphically, this area is characterized by reduced sedimentary layers, which consist of clastic and carbonate deposits(Silurian to Tertiary). The Triassic is mostly developed in the north-eastern part of the study area. In the ‘Meseta’, the Triassic reservoirs are shally sandstone, These sandstones are generally sourced from erosion of Palaeozoïc highs. These formations are continental depositional system, they are often associated with basalt, deposited in fluvial environment, with tidal influence. These reservoirs consist of fine to medium grained sandstone with low angle cross stratifications, coarse sandstone to conglomerate. The reservoir quality is relatively medium (porosity 2 to 5 %, permeability is about 2 md). The diagenetic effects are mainly represented by calcite and anhydrite cement in fractures. In regard to petroleum aspect, the Triassic reservoirs have revealed encouraging gas shows in some wells (CED-1 and CC-1).