Yesterday's Wikileaks release of a confidential 2007 State Department message on Saudi oil can be summarized as follows:
The actual Saudi oil resource (oil-in-place) is not the publicly claimed 700 billion barrels but roughly 400 billion barrels. With an optimistic recovery of 50%, that means reserves were roughly 200 billion barrels. Saudi production-to-date is around 100 billion barrels, so Saudi oil production is near its reserves midpoint, after which production will begin to decline. If that is indeed the situation, the world oil production outlook is congruent with the forecast of many (Hirsch et al, DOD, others) of near-term world oil production decline and the DOE forecast is "less informed."
Sadad al-Husseni is an outstanding geologist and petroleum engineer and has had more access to Aramco and Middle East oil data than virtually anyone ever.
The full Wikileaks release can be found at http://www.wikileaks.la/us-embassy-cables-saudi-oil-company-oversold-ability-to-increase-production-embassy-told/ It's a little confused in places but still quite clear.