The World's Endowment of Conventional Oil and its Depletion


... as of end 1999 ...
Produced 820
Reserves 827
Discovered 1647
Yet-to-find 153
Yet-to-produce 980
Ultimate 1800
Depletion rate 2.2%/yr
Depletion midpoint 2003
Estimates Made
in Prior Years
The assessment of the world's oil endowment is a sensitive subject with political implications and many vested interests. Some published reserve numbers are spurious, and lax definition has led to misconceptions. Study of the world's oil endowment involves the elements listed in the table. Reserves are defined as Median Probability reserves in which the risks of the estimate proving above or below the actual are evenly matched. They are about 180 Gb below published reserves, which in many cases include the above-mentioned spurious numbers. The numbers refer to Conventional oil, namely that which has supplied more than 95% of all oil to date and which will continue to dominate supply until well after peak, much of it free-flowing from giant fields found long ago. The estimate of Yet-to-Find takes into account discovery rates and the results of exploration drilling. It also recognizes that the world has now been thoroughly explored, meaning that few, if any, major new provinces await discovery. Adding 500 Gb to the Ultimate, which is itself implausible given the time and number of wells required on present trends, would delay the midpoint of depletion, which approximates to the peak, by only ten years. About half the Yet-to-Produce lies in just five Middle East countries. Their share of world production has risen from a low of 16% in 1985 to 27% in 1996, and is set to continue to rise in the absence of any new major province. The rising share will give an increasing control of the market that is expected to lead to a radical increase in oil price before the world midpoint of depletion is reached. In any event, by the end of the first decade of the 21st Century, production will have commenced its inevitable long term decline from resource constraints. Gas and non-conventional oil output will increase after peak, but it will not be a seamless transition dut to the very different characteristics and depletion profiles of these hydrocarbons.

comments by C.J.Cambell, October, 1997

1997 October