Assessment Performance Tracking of Multiple Target Prospects - A Statistical Approach

Abstract

Systematic tracking of exploration results relative to pre-drill predictions is challenging, but important. It is a means both to motivate assessment quality and to improve the assessments produced by the exploration team. Unbiased, accurate and consistent assessments are key for effective exploration decisions. This paper deals with the case where a single well targets multiple zones, compartments or reservoirs in a prospect. Most companies handle the situation as a case of multiple distinct targets. However, while simple, this approach ignores to what extent assessment has handled estimation of risk dependencies and volume correlations between targets. A key challenge for tracking assessments of multiple target prospects is tracking the estimates of risk dependencies between the targets: single well results do not give clear feedback on this estimate. We present an exploration program-level statistical measure of the quality both at the level of aggregate risk dependency estimates and at the level of the individual chance (risk) factor dependency estimates. The procedure is demonstrated with a hypothetical, but illustrative drilling program. Implementation of multiple target prospect assessment performance tracking should both improve assessments of this class of exploration ventures and stimulate more robust, accurate and transparent estimation of prospect-scale risk dependencies.