The world’s remaining conventional proved oil reserves have been appraised at about 1.27 trillion barrels, including crude oil, condensate and natural gas liquids (but excluding heavy oil, oil shales, and the Canadian tar sands). The world has already consumed 1.2 trillion barrels.
Reserves estimates are always uncertain, and are sometimes subject to political considerations. OPEC proved reserves are a major concern, because their data is not transparent. Reserves numbers change up or down over time. Produced oil should always be subtracted from current estimates each year, just as new discoveries and growth in existing reserves are added back in, but many OPEC producers have claimed exactly the same reserves year after year despite their large production volumes.
It is unlikely that there will be agreement in the medium term about the size of the world’s proved reserves. For this reason, the peak oil perspective focuses on past production figures, current production directions, and anticipated production trends.
However, it is indisputable that the depletion of oil reserves eventually must be accompanied by declines in production rates. Moreover, putting new reserves into production, or full utilization of productive capacity, is affected by a variety of so-called “aboveground” factors, including OPEC policies, inflation in the oil industry that erodes investment, and geopolitical conflicts.
“Perspective on Oil Resource Estimates,” Ken Chew, IHS Energy. A presentation given to the AAPG Hedberg Research Conference, November, 2006.