There is a subtle, but important difference between data distributions and uncertainty distributions that is often overlooked, and mis-understood in Quantitative Prospect Evaluation.

In Quantitative Prospect Evaluation we need to estimate properties of several variable (like thickness, porosity, Net-to-Gross etcetera). While doing that we realize that all these estimates have uncertainties, for which reason we create Uncertainty Distributions of all these parameters. These uncertainty distributions are then used as input distributions for a Probabilistic Volume Calculation.

Then what is the distinction between Data Distributions and Uncertainty Distributions?

I like to explain that with a simple analog. In this example I try to estimate the height of girl with the blocked shirt in this class photo We are in the fortunate situation that we know the height of all the other persons in this photo. So, by comparison we can estimate the height of this girl. Now the question is what is the Uncertainty of this estimate? The distribution of all the data-points tells us something about the population (the Data distribution), but it tells us nothing about the uncertainty of the estimate of this girl (the uncertainty distribution). The latter depends on the method and shortcoming of how me made that estimate

This happens to be a common misunderstanding in Quantitative Prospect Evaluation. I think the cause of that misunderstanding is twofold:

• Several software products perpetuate this misunderstanding and use “The Distribution” without specifying what type of distribution it is.

• Lack of training in Quantitative Prospect evaluation and the associated MonteCarlo methods to create probabilistic volumes. Many geologists are just given a piece of software, without the proper instruction on how to use it.