COS .... whats it mean?, page-25

Totally tongue in cheek comment.

To get a volumetric estimate of mean recoverable oil (i.e 825 mmbbls) one needs to make educated guesses of the least the following -
- gross reservoir volume from mapping and interpretation.
- porosity
- water saturation
- recovery factor
- expansion factor
- gas/oil ratio
- gas inerts, e.g. C02

Nortmally one would associate a guesstimate lognormal distribution to each item - but not always.

For example, we might say that porosity is distributed log normally with a 90% chance that it will exceed 12% and a 10% chance that it will exceed, say 80%.

We then take all the guesses and pass them through a huge Monte Carlo simulation that might have a few million randomized guesses according to each of the guesstimate distribution.

Then a PMean of 825mmbbls pops out and we say that’s our guess ...

Really it’s all about how accurate your input guesses are. While we might have some idea, we are still guessing until the dril bit speaks.