Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM

The Hydrocarbon Habitat of the Agadir Basin
Offshore Morocco
Daniel M. Trümpy
Scott C. Reeve
Shell International Exploration and Production, Inc
Deepwater Services
P.O. Box 576
Houston, Texas 77001
e-mail: dmtruempy@shellus.com
Abstract
The Agadir basin is situated off the Moroccan Atlantic coast and the Canary Islands. It comprises some 80,000 sq
km of shelf and deep water acreage, and has been explored by 16 wells, all drilled on the shelf margin. The deep water
basin remains undrilled at present.
In 1998, Shell acquired 2,000 km of 2D seismic in the Agadir deep water basin, where previous exploration had
revealed the presence of a mobile salt substratum in an area characterised by the presence of a world-class source rock
(the Albian -Turonian Tarfaya Shale). On the Jurassic carbonate and Cretaceous clastic shelf, significant oil shows
had been discovered during the seventies.
Key results of the 1998 to 2000 Agadir Basin exploration are:
1. The basin is highly structured, due to interaction of the Atlas compression with passive margin extension and
halokinesis. This structuring creates a large number of potential traps.
2. An Atlas-sourced fluvial system delivers Tertiary turbidites to the basin. Late Cretaceous and Palaeocene sandstones
appear to be derived from the Moroccan Meseta. A Jurassic to Cretaceous delivery system from a more
southerly source is expected to shed older turbidites into the Agadir basin. Erosional scours originating on the
platform confirm that the Cretaceous shelf sands have been transported into the basin.
3. Reservoir quality is a possible concern in an area where carbonate rocks abound in the source area. The main
objective in the northern part of the Agadir basin is a Late Cretaceous to Paleogene reservoir play, which ties back
to shelf and fluvial sandstones outcropping onshore in the Souss valley and predates the formation of the High
Atlas range. Secondary objectives occur in the Neogene and in the Lower Cretaceous to Jurassic intervals.
4. Geochemical modelling supported by the shows in platform wells and the abundance of oil slicks suggests that an
active oil charge system is working in the basin. The world-class Tarfaya Shale is likely to be mature over large
areas. Older source rocks are likely to further contribute to oil (and gas) charge. They comprise Oxfordian and
Liassic shales, but also more speculative Westphalian coals and Silurian shales.
5. Halokinesis is active over the entire area, but increasing in intensity and becoming progressively younger towards
the northern part of the Agadir permit, where compressional activity has focused. Locally therefore trap integrity
and/or charge timing may form an issue for truncation plays against piercing salt domes. Other play types in the
Agadir basin consist of anticlinal closures over deep-seated salt swells, fault-related structures and stratigraphic
traps.
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