1 ) Overview
The Abda-Doukkala basin is located between Oum errabia and Tensift rivers, and covers an exploration area of 11 682 Km².
A number of Oil and Gas shows were reported in the Permo-Triassic sands and Devonian carbonates. The Permo-Triassic sandy and conglomeratic objectives were not drilled in structurally favorable positions and Devonian carbonates were only considered in structural trap not as stratigraphic objectives. This may explain the lack of success.
2 ) Data base
3 694.40 Km of 2D seismic profiles were acquired in the Abda-Doukkala basin starting in 1976. From 1964 to 1987, 11 exploratory wells were drilled in the basin with Paleozoic and Triassic target. Oil and gas shows were recorded in six wells.
3 ) Tectonic and Sedimentary Evolution
The Abda-Doukkala basin belongs to the Moroccan western Meseta which is a Paleozoic continental block that was deformed during Hercynian consolidation of Eurasia and Gondwana then faulted during Early Mesozoic break up of Pangea. Atlasic/Alpine Orogeny was not recorded in the basin. The basin is composed of gently deformed Lower and Middle Paleozoic foreland shelf strata and overlain by a wedge of Mesozoic and Quaternary sediments. The sediment pile reaches 12 Km in thickness, with a faulted and folded Palaeozoic section unconformably overlain by a Mesozoic section.
4 ) Petroleum system
4-1 ) Hydrocarbon Occurrences
A number of Oil and Gas shows have been seen in the Permo-Triassic and Devonian. The Permo-Triassic sands are producing in the Meskala field of the neighboring Essaouira basin and have been tested in the recent Talsint discovery.
4-2 ) Source rock
Well data indicate Silurian and Devonian ‘hot’ shales source rock intervals with fair to good TOC values, ranging from 1 % to 5 %. Geochemical analyses carried out indicate mixed type II and III source rocks that are within the oil window.
4-3 ) Reservoir Rocks
Two main reservoirs constituted by Permo-Triassic sandstones with porosity ranging from 7 to 16 % nad the Middle Devonian carbonates and reefal build ups, with porosities varying from 1 to 14%.
4-4 ) Seals
Middle and Upper Devonian shale intervals are thick enough to provide a seal for Middle Devonian reservoirs. The Permo-Triassic-Liassic salt section is a good seal for the Permo-Triassic reservoirs. The Jurassic-Cretaceous anhydrites are an extra seal.
4-5 ) Traps
Concerning the Permo-Triassic objectives, large anticlines and simple structural traps have been interpreted in the 2 D seismic. For the Middle Devonian the trap is stratigraphic which has been seismically delineated as a reefal complex.
5 ) Play Concepts
Two main plays concepts were developed in the basin: Permo-Triassic sands and Middle Devonian carbonates and reef complexes.
6 ) Prospects and leads
Considering the two main targets, it seems that they have not been explored under the best conditions. The suggested new Triassic prospective area lies in sag between coastal shallow Palaeozoic and an inland Hercynian front. The Middle Devonian reefal complex is located at the same area of Triassic sag.
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Basin
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Abda-Doukkala
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Basin type
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Triassic Rift – Paleozoic basin
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Area
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11 682 Km²
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Exploratory wells
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11
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2D Seismic/3D Seismic
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3 694.40 Km of 2D
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Source Rocks
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Potential mature source rocks are the classic Silurian (Lower Llandoverian) ‘hot’ shales of North Africa and a ‘hot’ shale in the Devonian (Frasnian).
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Reservoir Rocks
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Devonian reefs and Triassic clastics
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Seal Rocks
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Middle and Upper Devonian shale intervals.
The Triassic-Liassic salt section.
The Jurassic-Cretaceous marles as an extra seal.
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