High Plateaux Basin30 Nov 2018 23:45
Overview
The High Plateaux Basin, 20 036 km² is limited by the Mechkakour Lineament to the west and stretches eastward to Morocco-Algeria borders. The SBK-1 gas discovery well in Talsint area has given a real boost to the exploration of the untapped reserves of this vast zone.
Data base
Since 1974, a total of 4 110 km of 2D seismic lines has been acquired in the area. In the year 2004, 498 km² of 3D seismic was shot on the Tendrara structure. During 1963-2016 period, six core drills were achieved for stratigraphic purpose and nine exploratory wells were drilled.
Tectonic and Sedimentary Evolution
Tectonic Evolution
The High Plateaux Area, like its surroundings, underwent three main orogenic phases:
The Hercynian Phase with thrusting and magmatic intrusives.
The Triassic - Jurassic extension phase with normal faulting.
The Alpine compressive Phase causing the inversion of the Atlas and halo kinesis, especially in the southern part of the area.
Sedimentary Evolution
The Siluro-Ordovician, and the Devonian periods are represented by shales, quartzites, carbonates, sandstones, and claystone. The Carboniferous is composed of claystone and siltstone of Visean-Namurian age. Coal-bearing clastics of Westphalian age are present in the north, in Jerada coal mine,and in OSD-1 well in Missour Basin. The Triassic series are composed of TAGI overlain by salt beds and basalt. Jurassic formations are mostly carbonates and dolomites of Liassic-Bathonian age. The Cretaceous and the Cenozoic are characterized by conglomerate, limestone, shales and anhydrite deposits.
Petroleum Systems
Hydrocarbon Occurrences
SBK-1, TE-6 and TE-7 wells, spudded between 2000 and 2016 in the Tendrara & Talsint areas, revealed gas and condensate accumulation in the TAGI reservoir. Tests are ongoing
Source rocks
Paleozoic source rocks: Visean- Namurian source rock analysis from Tendrara wells revealed gas prone type III shale with a TOC value of 0.5 to 1.5 %, and a maturation rate of 1 to 1.3 per cent Ro.
Mesozoic source rocks: Lower Jurassic black shales, encountered the surrounding High and Middle Atlas belts, reveal rich oil prone type II black shales (TOC is up to 8% in the Middle Atlas trough (Issouka area) and up to 2% in the High Atlas).
Reservoir rocks
For the Triassic, the TAGI Formation is the main reservoir in the basin. He revealed gas and condensate in Essaouira Basin and in the High Plateaux (Tendrara & Talsint). This reservoir is also considered the main objective in some fields in Algeria. The TAGI is 400 m thick in RR-1 well. The porosity varies from 6% to 15% in some wells and could reach 25% in outcrops. The Visean and Devonian Carbonate (reef constructions) are also known in the High-Plateaux basins as reservoirs.
Traps
Structural traps: reverse fault- related features such as thrust sheets, half grabens, tilted blocks, rollover anticlines, and salt- related traps.
Tratigraphic traps: pinch outs, reefs and sand lenses.
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