ABSTRACT

The Rharb Basin is situated in northwestern Morocco and extends westward into the adjoining offshore area of the Atlantic Ocean. It is a Tertiary foredeep that separates the Rif fold-thrust belt from its foreland. The Rharb Basin was a part of a strait about 500 km long and up to 100 km wide that connected the Atlantic to the Mediterranean. After the closure of the strait in the Late Miocene, the basin became a large Atlantic gulf.

Most of the basin is underlain by a giant oilstostrome known as the Pre-Rif Nappe. The very complex morphology of the top of the Nappe and its temporal variations were very important controls on depositional processes, whereas the structure of the supra-Nappe sequence was affected, to a high degree, by the movements of the oilstostrome and its rheological properties. Three unconformities have been recognized within the supranappe section, the most important being the Messinian unconformity.

Although the first discovery was a small oil field, the Rharb Basin is considered as predominantly a gas-prone area. A number of relatively small, but commercial, accumulations of early diagenetic gas have been discovered in very fine grained, mostly silty and/or shaly sands in the Globorotalia dutertrei biozone. Gas entrapment is predominantly controlled by stratigraphic factors, but commonly the contribution of structural factors is not negligible. The most difficult exploration problem is to predict the areal distribution of reservoir rocks, which depends on both depositional processes and provenance. An attempt has been made to develop a predictive depositional model based on the integrated interpretation of all available outcrop, well and seismic data.

End_of_Record - Last_Page 178-------