Reporting the expected exploration outcome: When, why and how the probability of geological success and success-case volumes for the well differ from those for the prospect

Some petroleum explorers and exploration companies do not distinguish the probability of geological success (PoS) and the success-case volumes estimated and reported for the prospect from those for an exploration well. This may mislead decision-makers and investors and may result in disappointments with drilling outcomes. When the well is positioned downdip from the highest closure point(s) of explored segment(s) (also called target(s) or zone(s)) in a prospect in order to penetrate larger than the minimum assumed petroleum column(s), the geological PoS for the well is smaller than the geological PoS for the prospect. Conversely, the expected success-case volumes for such a downdip well are larger than for the prospect. This paper discusses a simple fictitious prospect with three segments and the exploration well that penetrates these segments downdip from highest closure points. The results demonstrate the key differences in geological PoS and success-case volumes between the well and the prospect. Proper reporting of the expected exploration outcomes from planned exploration wells will result in better-informed drilling decisions. Modeling outcomes of drilling the well at various locations within the prospect would help to understand if the well can discover the minimum economic field size, estimate the volumes that may remain untested updip, and maximize the expected monetary value of the exploration project. During postmortem evaluations (look-backs), it is important that well outcomes are compared with relevant pre-drill well assessments.