Geology of the Rockall Basin and adjacent areas

The deep-water Rockall Basin extends from southwest Ireland to north-west Scotland and constitutes the exploration frontier for oil and gas on the continental margin to the west of the British Isles. Up to the present time, oil company interest has focused on shallower areas of the UK continental shelf and west of Shetland. Hence the Rockall Basin has not been extensively explored and geological understanding of the basin is limited. Whereas over 10 000 commercial wells have been drilled on the UK continental shelf as a whole, only 12 of these have been drilled within, or on the margin of, the Rockall Basin. The earliest pioneering exploration of the basin was undertaken in the late 1960s and early 1970s. Exploration was encouraged by the UK government designating ownership of the Hebrides Shelf in 1971 and of the Rockall Trough and Rockall Bank in 1974. This provoked the acquisition of commercial nonexclusive ‘speculative’ seismic datasets. The first hydrocarbon exploration licence was granted in 1974 and the first deep well, a stratigraphical test, was drilled in 1980. The first potential oil well was drilled in 1988. Most exploration was concentrated on the eastern side, or eastern flank, of the basin. It wasn’t until the British Geological Survey (BGS) established the Rockall Continental Margin Consortium in 1992, comprising BGS and eight sponsoring oil companies, that a systematic basin-wide multidisciplinary exploration programme was developed. Since 1992, and with more companies involved, various geophysics, seabed sampling and shallow drilling cruises have been undertaken and the interpretation and analysis of the data collected have formed the basis for this report. The basin is currently sediment starved and underexplored. Volcanism during the Palaeogene has added to the difficulty of data interpretation but hydrocarbon discoveries, on the eastern margin of the basin in both UK and Irish waters, demonstrate a working petroleum system and suggest that further exploration is warranted. This report aims to provide a comprehensive summary of the geoscientific knowledge of the Rockall Basin area and we envisage this will be a useful resource for industry, government and academia.