The onshore Gharb basin is located in the external zones of the Rif folded belt. This basin, covering an approximate area of about 7 394 Km², extends from the city of Sidi Kacem to the South East to Moulay Bousselham village in the North West. To the West, it’s limited by the Atlantic Cost line between Moulay Bousselham and Kenitra cities.

The Gharb basin is a foreland to fore deep basin type developed at the front of the Rifain Chain. Sedimentary evolution led to the deposit of more than 3000 m of Upper Miocene clastic sediments above the complex of nappes. A very thick series of Eocene and Oligocene turbidites and Early to Middle Miocene continental molassic sediments are developed within the infranappe sequence overlying the Mesozoic carbonates and clastics.

The Gharb is a biogenic gas producing basin. Methane is early expelled from Upper Miocene type III or I source rocks (mainly shale and marls) and trapped within surrounding sand lenses. In the central part of the basin, at depths greater than 1600 m, Cretaceous source rock, located within the complex of nappes would be mature and would generate oil or cathagenic gas.

Reservoir rocks have been deposited during Tortonian and Messinian times, series with turbiditic sandy lenses were developed under fall of sea level conditions. Recorded porosities are very high and could reach 33% in some cases with an average of 25 to 30%. Permeabilities are also good to very good permitting a very good productivity such as the case of OLB-1 well (calculated permeability = 400 mD).

In the Gharb basin, objectives are presents in combined stratigraphic (sand lenses) and structural traps (faulted and folded blocs).

The developed play concepts lie to the presence of amplitude anomalies within the supra-nappe sequence in the central and southern parts of the basin. Many amplitude anomalies have been identified, drilled anomalies have produced or being produced from objectives located at shallow depths (700 to 1300 m).

 

In the central part of the basin, at depths greater than 1600 m, Type II and I source rocks would be mature and would generate oil. This increases also the probability of generation from the complex of nappes. As far as liquid hydrocarbons are concerned, the deeper parts of the basin, which are practically unexplored, may contain potential objectives.

 

In the north and the north-eastern parts of the basin, recent studies have shown the presence of various zones of interest within the supra-nappe sequence. Objectives are shallow (between 100 and 700m) and are visible on seismic as amplitude anomalies related to gas caps over oil accumulations. In this area, the nappes complex (Ouezzane and Prerif nappes) may also provide good reservoirs within Eocene, Oligocene and Lower Miocene sandstone and conglomerate.

Exploration conducted so far in the Gharb basin has demonstrated the presence of important hydrocarbon potential within the Tertiary depositional system. Defined prospects are small in size but they are economically interesting for the following reasons:

The Gharb basin has produced oil in the Ain Hamra and biogenic gas from many small fields located within the central and southern parts of the basin. The total production of oil reached 0.1 MMbbls. The cumulative gas production is around 35 Bcf.

Basin	Gharb
Basin type	Foreland basin
Area	7 394 Km²
Exploratory wells	53
Gas discoveries	Biogenic gas
2D Seismic/3D Seismic	5.855,00 Km of 2D / 145,00 Km² of 3D
Source Rocks	Upper Miocene (III or I); Cretaceous
Reservoir Rocks	Turbiditic sandy lenses from Tortonian and Messinian times
Seal Rocks	Marls from the Tortonian and the Messinian times
Hydrocarbon type	Biogenic Gas