If you trust OPEC, then peak oil will happen around 2030
If you trust the Seven Sisters that ran ran OPEC's oil fields before the 1970s, then it is around 2010.
If you believe the Seven Sisters had reasons to over-estimate their oil reserved in those same fields, then 2005.
No one trusts OPEC's reserve numbers, all of them went up drastically in the 1980s for the simple reason OPEC set a member's export quota based on their oil reserves. For that reason every OPEC member had a reason to push up the numbers.
Thus more people trust the data the Seven Sisters had on those same fields, but the Seven Sisters had a problem, in the 1930s Mexico took over Mexican oil fields and only offered to pay what the Oil Companies were claiming was the value of their oil fields. Under normal accounting rules, any asset is kept at the "Lower of Cost or Market" (I know the banks are ignoring this rule right now, but we are talking the 1950s, 1960s and 1970s when SEC actually enforced the law as to following the "Lower of Cost or Market" .
Iran, did the same thing in 1954, just before we over threw the Government and made the Shah an absolute dictator of Iran.
Thus the Seven Sisters had great incentive to over-state the value of their assets, just in case another country did what Mexico and Iran had done. The Stock Market, and Anti-Trust Department of the Department of Justice and the SEC would NOT have liked such over-statements (We are talking about the 1960s) but I see all of them accepting it as a cost of doing business overseas.
Thus do you believe that the Seven Sisters were more afraid of a takeover of their overseas oil fields OR more afraid of the SEC, the Anti-trust section of the Department of Justice and Stock Market own regulations? If you believe the seven sisters were more afraid of the US Regulators, then they numbers are correct and peak should occur within a couple years of 2010. On the other hand if you believe Wall Street was more afraid of having to sell those same fields for the value of those fields as reported on their books, then those books value were over-stated and Peak Oil occurred around 2005.
Those are the Theories, and it looks more and more like not only is OPEC lying, so had the Seven Sisters.