elyomYour description of the P10, P50 and P90 system is probably...

elyom

Your description of the P10, P50 and P90 system is probably correct, but I think of it (as a former scientist) more the other way around. That is, when calculating the size of a potential reservoir a certain degree of certainty can be applied to the estimate based on the data available. The geos would then state the "probability" of each estimate as being eg P90 = a 90% chance of this estimate being found to be correct (and only a 10% chance that there could be less) - i.e they are 90% confident of this estimate. Likewise for P50 = a 50% probability of this estimate being correct, and P10 = only a 10% chance of this estimate being correct. So by my interpretation its about the degree of confidence they have in each estimate (called in statistical speak "the confidence interval").

Just my penny's worth and happy to be wrong if its different in petro science (or have I just restated what you said?).

Cheers

H