The remaining hydrocarbon potential of the UK Continental Shelf

The United Kingdom Continental Shelf (UKCS) has been a very successful exploration province in the last 38 years, with an average technical success rate of 31% from its 2150 exploration wells. Although the peak of exploration activity on the UKCS occurred during the 1980s and 1990s, there have been 41 technical successes from 82 wells in the last four years, representing an improved recent success rate of 50%. Estimates of undiscovered (yet-to-find) hydrocarbon volumes have been made from a database of prospects compiled over 20 years by the UK Government. This ‘bottom-up’ method provided an estimate of the yet-to-find resources at the end of 2002 of between 3.6 and 22.9 × 10 9 BOE recoverable. Methodology utilizing an inverse timescale to plot cumulative discovered volumes per year provides minimum estimates of between 4.5 and 9.5 × 10 9 BOE in place ( c . 2.5 to 4.4 × 10 9 BOE recoverable). Pool size distribution methodology predicts that 11.5 × 10 9 BOE of in-place ( c . 5.8 × 10 9 BOE recoverable) resources remain to be found on the entire UKCS. Geographically, the UK Central North Sea and Moray Firth area is predicted to contain the largest proportion of undiscovered resources (42%). Thirty-three per cent of the yet-to-find resources are judged to lie within the Atlantic Margin region. Eighty-three per cent of existing UKCS fields and discoveries are located within structural traps. The majority of stratigraphic and combination traps occur in association with syn-rift (Upper Jurassic) and post-rift plays. Many of the major discoveries in these traps were found serendipitously, and there has been relatively little direct exploration for stratigraphic plays. In the UK North Sea, there are few substantial remaining structural traps, except at considerable depth with attendant reservoir quality, high-pressure and high-temperature risks. The future of exploration is believed to lie with the search for subtle stratigraphic traps. Deep-water sandstone stratigraphic plays within the syn- and post-rift sequences offer the greatest potential for substantial new resources.