Evaluating Conceptual Plays
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remain unanswered: How many anomalies were not detected
by the current orientation and density of seismic lines? What
is the maximum number of prospects that could exist in this
play? How many prospects would there be at a 50% chance?
The answers to these questions provide us with information
needed to construct probability distributions for the prospects.
Other values at various upper percentiles can also be used.
For each probability distribution, values of the four upper percentiles (1.0, 0.5, 0.02 or 0.01, and 0.0) are the minimum requirement for
constructing a distribution. The process commences by fi tting a lognormal distribution to these four values and then generates all other
upper percentiles. Assessors can either (1) enter the four upper percentiles and let the shape of a lognormal distribution generate other percentiles or (2) enter all percentiles and examine the difference between
the input percentiles and the lognormal approximation.
Table 5.12 presents a sample format for tabulating a probability
distribution. Samples for tabulating exploration risks (Table 5.13) and
numbers of prospects and pools are also presented (Table 5.14).