Petroleum systems offshore western Ireland in an Atlantic margin context

Abstract

Abstract The Rockall, Slyne, Erris and Porcupine basins on the Atlantic margin off Ireland belong to a family of geologically similar basins stretching from offshore mid-Norway to offshore Newfoundland. Jurassic sequences act as reservoir and source rocks in many of the basins. Cretaceous extensional faulting was widespread and major subsidence affected several basins. Cretaceous submarine fan and shallow marine sandstones and Paleocene submarine fan sandstones often provide reservoir targets. Cretaceous and Paleocene to Eocene volcanic rocks are widespread and Eocene to Recent net subsidence has resulted in water depths which generally exceed 200m and reach over 2000m in the south. Passive uplift affected the land areas to the east in Neogene times. Proven Jurassic-sourced petroleum systems occur in six basins from the Halten Terrace to the Jeanne d’Arc Basin, including the northern Porcupine Basin and the Slyne-Erris basins. In the latter the Jurassic petroleum system has been destroyed by uplift, but a Carboniferous petroleum system has proved successful there for gas. West and northwest of these proven basins, on the ‘outboard’ side of the Atlantic margin, are large frontier areas. Recent gas discoveries in the deep Vøring Basin prove the existence of petroleum systems there but the source is not known. On both margins of the Rockall Basin and in the southern Porcupine Basin petroleum systems may exist but are not yet proven.