Ordovician Plays from the Arabian and Saharan Platforms: A Comparison

Neil McDougall¹, Didier Wloszczowski², and Khaled Sharky^2
1Spain Exploration Team, Repsol-YPF Exploration, Madrid, Spain
²EniRepSa Gas Ltd, Al-Khobar, Saudi Arabia

The Cambro-Ordovician is a major hydrocarbon play across the Saharan Platform of North Africa, producing significant quantities of both oil and gas. This is also increasingly the case in the Arabian Platform where the Ordovician sediments of the Sarah, Zarqa, Saq and Qasim Formations are well-developed both in the outcrop and in the subsurface. These are proven producing plays and offer a significant exploratory upside, especially for deep gas. Despite this, the Cambro-Ordovician plays of the Arabian Platform are not necessarily well-understood and their potential difficult to assess with confidence.

To better address this issue and help reduce risk, Repsol-YPF has undertaken comparative studies with the Ordovician successions of both Libya and Algeria, both of which are a major target for hydrocarbon exploration. In both cases there is an abundance of well-documented outcrop and subsurface data which serve to illustrate the development and architectures of the two key reservoir objectives for which detailed geological models have been developed. These models are used as a basis for comparison with the Ordovician both in outcrops and the subsurface of the Arabian Platform, with remarkable similarities noted between the following broad sequence packages: (1) the Saq Sandstone and the Hassaouna and Unit II Formations of Libya/Algeria, (2) the Qasim Formation and the successful Hawaz Formation play in the Murzuq Basin of SW Libya and also (3) the Upper Ordovician Zarqa and Sarah Formations which are directly comparable to the prolific Mamuniyat or Unit IV (Tamadjert) reservoirs in both Libya and Algeria. In the case of sequence packages (2) and (3) the plays are linked, associated with the erosional and depositional effects of a major end-Ordovician glacial event.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery