Exploration history on the Norwegian Continental Shelf, 1990–2002: expectations and results

Abstract

The exploration activities on the Norwegian Continental Shelf during the period 1990–2002 were analysed; 300 wildcat wells were drilled and 134 discoveries made. A dataset consisting of 240 wildcat wells and 83 discoveries was studied. The volumetric in-place prognosis of the prospects were compared with the actual exploration results. The analysis indicates that exploration appears to have been determined by the chance of finding oil and that there is no obvious correlation between prospect volume, proximity to infrastructure and probability of discovery. Comparison of the prognosed and the discovered volumes shows that, in total, the prognosis is double the actual discovery volumes. This is mainly due to overestimation of oil prospects, as discovered gas tends to match the prognosis. The volume of discoveries smaller than 100 × 10 6 Sm 3 oil equivalents (OE) corresponds to the prognosis, whereas prospects larger than this are overestimated. The best match is found for prospects in the 50 – 100 × 10 6 Sm 3 OE size category. Exploration of prospects is undertaken with too great a risk and there is no relation between prospect size and probability of discovery, except for the very large prospects which have lower probability than the rest of the prospects. There is no evidence for better performance in mature areas and overestimation is characteristic for most companies. The match between prognosis and actual volume is good for fields (approved for development), whereas discoveries in the planning phase are significantly higher than prognosed. The disappointing discoveries are either still unclarified or unlikely to be recovered. Results of exploration activity constitute an important part of the QC of prospects reported to NPD when these data are used for the evaluation of the undiscovered resources. NPD uses modelled prospects for calculation of the undiscovered resources.