redinvest: Yes, it would certainly be interesting to see valuations based on probable and possible reserves.
If proven reserves are valued at $15 per barrel, I would think probable reserves may be valued at around $3 to $5 per barrel.
Even using the most conservative of numbers ($3 per barrel for probable reserves, 500M probable barrels), that would give us a share price of $2.
Then using more realistic numbers ($5 per barrel and 750M probable barrels) would equate to a share price of $5.
Mike