Nick Schofield, Lena Broadley, David Jolley

The UK Rockall Basin is one of the most underexplored areas of the UK Continental Shelf (UKCS) with only 12 exploration wells drilled since 1980, in a basin area that is equal in size to the entire North Sea hydrocarbon province (NNS, CNS & SNS). With only one discovery, made in 2000 (Benbecula South 154/1-1 Gas discovery), the general view of the basin from an exploration viewpoint has not been traditionally positive. The overriding aim of this document is to allow an accessible introduction to the exploration history and hydrocarbon prospectivity of the Rockall region, while at the same time highlighting some of the recent advances in understanding of the basin. Importantly, this report highlights that although the ratio of 1 discovery to 11 dry wells can be interpreted as indicating a basin with little to no viable petroleum system, this statistic is misleading. As of 2019, based on the assessment in this report, we would argue that the discovery to dry hole ratio is closer to 1:6 (rather than 1:11), due to five wells being drilled on invalid geological targets, as a result of lacking subsurface knowledge and/or poor quality seismic data. In addition to this, there is a lack of deep well penetrations with the UK Rockall, with only one well reaching sedimentary strata older then the Cretaceous, meaning that the detailed stratigraphy of the area is still largely unknown.
The exploration narrative of the UK Rockall should be placed in context in regard to the rest of the UKCS, where from the years 1965-2007, a total of 22681 exploration wells were drilled (compared against the 12 drilled in the UK Rockall from 1980-2006). Therefore, it must be argued that, as of 2019, not enough subsurface geological information currently exists within the UK Rockall to assess the viability of the petroleum system.