Stoker, Susan J.¹, P. Haile¹, Joy C Gray², Ian J Andrews¹, T. D. Cameron¹, M. Cave¹ 
(1) British Geological Survey, Edinburgh, United Kingdom 
(2) UK Department of Trade and Industry, London, 

ABSTRACT: Predicting the Remaining Hydrocarbon Resources of the UK Continental Shelf: 'Top-Down' vs. 'Bottom-Up' Methods

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 2,150 exploration wells. Though the peak of exploration activity on the UKCS occurred during the 1980s and 1990s, there have been 41 discoveries made during 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 x 10⁹ BOE recoverable. ‘Top-down’ methods tend to produce more pessimistic predictions. Using an inverse time scale to plot cumulative discovered volumes per year provides minimum estimates of between 4.5 and 9.5 x 10⁹ BOE in place (c. 2.5 to 4.4 x 10⁹ BOE recoverable). Pool size distribution methodology predicts that 11.5 x 10⁹ BOE of in-place (c. 5.8 x 10⁹ BOE recoverable) resources remain to be found on the entire UKCS. 
The major currently active plays and basin areas are analysed to determine the principal plays and basins for the future. Geographically, the UK Central North Sea, including the Moray Firth, is predicted to contain the largest proportion of undiscovered resources (42%). Thirty-three percent of the yet-to-find resources are judged to lie within the Atlantic Margin region. The expectation is that sufficient reserves remain to sustain exploration well into the 21st century.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.