AAPG Middle East Region Geoscience Technology Workshop, Rift Basin Evolution and Exploration

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Characterizing Recent Successful Post-Rift Deep-Water Turbidite Plays of the Atlantic Basin

Abstract

For the last 20 years the global exploration community has regarded Africa as the continent with the most remaining frontier exploration potential. Five areas have emerged in the last 12 years to justify this optimism, namely, the Tano basin of West Ghana, the Ruvuma delta of Mozambique, the Kwanza basin of Angola, the Senegal-Mauritanian basin and, most recently, the Outeniqua basin off the southern coast of South Africa. The first of these to emerge and the only one with a giant oil discovery currently in production is the Tano basin, situated along the West African Transform Margin. In 2007, Kosmos Energy and partners discovered the Jubilee field with their wild-cat Mahogany-1 well located in 1350m water-depth [1]. Billions of dollars have been spent by our industry attempting to replicate this DW exploration success and many more will likely follow in the years ahead, encouraged not least by EXXON’s and partners run of recent successes in Guyana. A look-back at the exploration history of West African Transform margin [2] reveals the challenges that E&P companies face when making investment decisions for exploration rights in a competitive market place following a spectacular new oil discovery. It provides a stark lesson in how a ‘gold-rush’ of exploration activity can destroy corporate value. Our industry needs to identify more prudent strategies to adopt for long-term efficient exploration in complex emerging DW basins faced with similar competitive challenges following a commercial break-through. The first step along this path is characterizing why some plays work and others don’t, and this is the motivation for this paper on Atlantic margin post-rift deep-water turbidite plays. Giant headline-grabbing wildcat turbidite discoveries such as Mahogany-1, Liza-1 (Guyana), SNE-1 (Senegal), Tortue-1 (Mauritania), Barquentine-1 (Mozambique), and Brulpadda-1AX (S. Africa), are all situated above Mesozoic-age rifted continental margins with significant Neogene overburden. Moreover, all tested traps with a stratigraphic component. This means they all have at least one effective stratigraphic lateral seal contributing to the formation of the hydrocarbon trap. Improving the predictability of this type of seal/trap is regarded as a prime factor in improving exploration success rate in this play type and a workflow for doing this developed by Shell will be described in this paper. REFERENCES [1] Dailly, P., Henderson, T., Hudgens, E., Kanschat, K., and Lowry, P., Exploration for Cretaceous stratigraphic traps in the Gulf of Guinea, West Africa and the discovery of the Jubilee Field: a play opening discovery in the Tano Basin, Offshore Ghana, in Mohriak, W.U., Danforth, A., Post, P.J., Brown, D.E., Tari, G.C., Nemcok, M., and Sinha, S.T., eds., Conjugate divergent margins: Geological Society, London, Special Publications, no. 369, pp 235–248, 2013. [2] Grant, C.J., Ghosh, S., Thompson, P., Staples, R. & Antonin, A. Deep-water Exploration along the West Africa Transform Margin: A Retrospective and an Outlook. 2018. Abs., Conjugate Margin Conference, Halifax.