Drilling an exploration prospect downdip: Quantifying the trade-offs between chance of success and associated resource potential

A common method for choosing an exploration prospect drilling location is to drill the crest of the structure.This tends to maximize the chance of discovering a conventional hydrocarbon accumulation.However, the discovered resource volumes may not justify development due to a limited proven area and thus require additional downdip appraisal drilling, adding appraisal costs and delaying possible development.An alternative approach is to drill downdip, where a discovery has a high chance of exceeding the minimum commercial field size needed to justify development.In practice, the prospect should be assessed using its full probabilistic resource distribution before selecting the drilling location.A downdip discovery smaller than the minimum commercial field size may lead a decision maker to drill another well further downdip.A dry hole drilled downdip with a thick, porous reservoir may lead a decision maker to sidetrack updip.This paper describes the reduction in the chance of success as the well location moves downdip and quantifies the resource distributions for the updip and downdip volumes relative to the drilling location.Although the overlap of updip and downdip resource distributions may be significant, using this approach allows the technical team to present an optimal location that maximizes value and quantifies the trade-off between a lower chance of success and increased resource potential.