Good question. If you have a Scribd account, download this pdf from Oil Price and read pages 7 - 10.  File size is too big for me to attach.   Here's the text of page 7:   THE THREE P’s: PROVED, PROBABLE, POSSIBLE The three Ps are probably some of the most misunderstood terms in the industry. They have changed and evolved, and they can often be the downfall of a new investor. Oil and gas reserve
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