I understand how reserves are defined and how they are...

I understand how reserves are defined and how they are calculated by modelling.

You are right that P50 means there is a 50% chance of these reserves being recovered under known conditions. But remember, that also means there is a 50% chance that they won't be recovered.

I am not for or against AED, I am just pointing out the fact that many recent offshore oil field developments have not lived up to their promise and have had (in some case massive) reserve and production downgrades.

In any case, good luck to all that hold.