AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Analogues that help decrypting the Irish Dunquin carbonate play, Porcupine Basin

Abstract

Over the past few years there has been an upswing in the exploration momentum offshore Ireland which is currently at its highest ever level as reflected not only by the number of exploration authorizations, but also in the amount of seismic data acquired. However, Ireland still remains underexplored, a total of just under 160 exploration and appraisal wells have been drilled offshore since 1971, this is a very small number when compared to nearby countries such as UK and Norway. The Porcupine Basin is a relatively under-explored rift basin located on the continental shelf 200 Km west of Ireland. Water depths range from 300-600 m in its northern part to 3500 m in the south, where it opens southwestwards onto the abyssal plain. The Irish platform is a broad, gently sloping shelf, bounded by the 500 m bathymetric contour. It is bound to the north by the Slyne Ridge, to the east by the Irish mainland, and by the Goban Spur basin to the south. The basin contains up to 9 km of Mesozoic and Tertiary sediments and is bound on three sides by shallow basement of Lower Paleozoic age. Proved hydrocarbons are present in reservoirs of Middle and Late Jurassic, Early Cretaceous and Paleocene age. The play identified in FEL 3/04 consists of Lower Cretaceous shallow marine carbonates of mid-Aptian to Albian age. The Dunquin play consists of two isolated carbonate platforms: Dunquin North and South with structural 4-way closures. Dunquin North prospect was drilled in 2013 (P&A), the well drilled a total thickness of 250 meters of massive porous carbonate reservoir and confirmed 44 meters of residual oil column, interpreted as a resulting seal breach. The presence of a paleo-oil column suggests an oil prone source rock present in the basin. The other elements of the petroleum system are also confirmed with the well. Reduced knowledge of the carbonate build-ups of Porcupine basin has led to an impact in the economics of this type of projects. A better understanding in internal carbonate morphological distribution, porosities, permeabilities, recovery factor, drilling knowhow and well productivities will decrease the associated risk. The study of appropriate analogues would provide more information, especially if taken into account that Dunquin North and South may possibly have its own unique characteristics unveiling potential differing genetic associations with tectonism and base level changes. The scope of this study is to provide a key insight into the history and a basin development of the South Porcupine Basin and discuss the different worldwide analogues that can give a hint on the main parameters that might profoundly impact the petroleum potential of this vast and underexplored NW European Atlantic Margin frontier basin. Having a better prediction in operating expenses is a critical factor for MEFS calculations and optimal investment.