Assessment Measures: Describing Uncertainty Accurately, Clearly and Unambiguously

Sykes, Mark A.; Hood, Kenneth C.; Setterdahl, Stephan I.
ExxonMobil Exploration Company, ExxonMobil Corporation, Houston, TX.

The history of the petroleum industry has clearly and repeatedly demonstrated that geologists and engineers cannot precisely predict or calculate hydrocarbon volumes potentially contained in a prospect or actually contained in a discovered field. The only moment at which this value is precisely known is the day after the final day of production. However, to optimize exploration strategy in a basin, or to manage development and production of a field, useful estimations of hydrocarbon volumes are essential. This must involve estimates, not only of the best estimate hydrocarbon volume, but also an appropriately characterized range of uncertainty. This uncertainty can then be tracked, managed, and used to optimize decision-making as the asset progresses through its lifecycle from prospect to producing field.

Several issues hamper this process. Firstly, terms used to describe uncertainty in the petroleum industry such as "mean", "most likely", "maximum", etc., are in common use in the English language, and their dictionary definition and vernacular meanings are not the same as their intended meaning when describing hydrocarbon volumes. This necessitates that both scientists and decision-makers understand the common lexicon of these terms to avoid confusion and to facilitate a rapid, effective and accurate transfer of information between these two groups.

Secondly, graphical renditions of hydrocarbon volume assessment results are often times interpreted in different ways by different people. These interpretations often conflict, causing confusion during technical discussions. This can complicate and retard an effective decision-making process based on these results.

A common schema of "Assessment Measures" is here proposed to clearly and simply ensure that all petroleum industry personnel carry consistent definitions of each volumetric term, and that visual inspection of, and conclusions drawn from, graphical representation of hydrocarbon volumes and their uncertainty is consistent within the same group of scientists and executives.

When scientists and managers share a common understanding of these definitions, decision-making processes are accelerated and optimized. Assets can now be evaluated and discussed without encumbering the process with misunderstandings regarding terminology and descriptors.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012