Seal Risking Reinvented Using 300 Year Old Math

Seal constitutes a primary geologic risk within petroleum exploration. Historically, translating seal analyses into risk commonly utilized risk matrices or tables, which combine measures of confidence and risk severity to reach a Chance of Success (COS). Unfortunately, pitfalls abound in the seal risking process, including failure to consider historical success rates, confusion between confidence and risk severity, poorly calibrated ‘gut-checks’, and DHI adjustments. These complications often resulted in inconsistent seal risking, an inability to distinguish more-risky from less-risky prospects, and poorly prioritized exploration portfolios. We present a new seal risking method – the Risking V – which helps to mitigate these obstacles. The method starts with calibrated base rates and explicit Lines of Evidence (LOEs) that address seal risk. Each LOE has clearly articulated confidence and risk criteria, defined by subject matter experts, which lead to Chance of Validity (COV) values. The risking minimum hurdle is a specified hydrocarbon column height. The user works through the LOEs, then applies sequential Bayesian updating to derive a robust COS specific to the characteristics of the prospect being evaluated. This new method results in a clearly documented and consistent seal COS and avoids many of the traditional risking pitfalls.