Robert L. Hirsch's latest summation can be found @
Energy Bulletin: Commentary: Restrictions on world oil production$this->bbcode_second_pass_quote('', 'G')eology is the ultimate restriction. Oil is a finite resource. We will never produce more oil than nature provided over millions of years. All that's there is called the oil resource, but we can only produce what is called the "reserves," which is a fraction of the resource. Why? Because the geology associated with each oil deposit sets a practical limit on ultimate production. In a few cases, reserves can total up to half of a local resource. In others, reserves can amount to no more than a few percent of the resource. Typically, reserves are around 30% of the resource. If you think we should be able to do better than 30% on average, take some time to look at some oil reservoirs rock cores.
The complexity is often mind boggling. What's this all boil down to? Based on geology, many analysts have forecast the onset of the decline of world oil production in the next 2-5 years. Legitimate national interests, mismanagement, and political upheaval can only hasten that onset. To explain these and other energy issues we wrote the book entitled "The Impending World Energy Mess." Oil production is a very complicated activity. What happens in oil will impact all of us, so it's worth some study.