Today's civilization depends on an abundant and relatively cheap supply of oil. It fuels most of our vehicles, aircraft, ships, and trains. It provides the raw material for fertilizer, some clothing fabrics, most plastics, and many chemicals. Oil heats many of our homes and businesses.
So when experts discuss when oil production will begin to decline, the world pays heed. The question now making the rounds in energy circles: Has production already peaked?
If it has - or if a peak lies only a few years away - the repercussions would be huge. It could intensify a scramble by oil importers to tie up existing reserves. Decline could lead to scarcity and higher prices, possibly recession, while prompting an urgent push to alternative fuels and conservation.
For at least one analyst, the scenario has already begun to unfold.
"World production is flat now," says Kenneth Deffeyes, a Princeton University geology professor.
But that's a controversial view. Other pessimists talk about 2010; many analysts see no change until 2035.
Of course, various "experts" have been predicting the end of the oil age for more than 100 years. And even now, no one really knows how much oil is left in the ground. Estimates involve guesses of not only future oil finds but future world economic output and oil consumption. These numbers are typically highly imprecise.
Even calculating current reserves is tricky. The Royal Dutch/Shell Group, one of the world's largest oil producers, shocked the financial community earlier this month when it announced it had overbooked its proven reserves by 20 percent - an indication of the fragility of such estimates.
The United States Geological Survey (USGS) puts yearly world consumption of oil today at about 30 billion barrels. That comes out of known or proven world reserves of 1.1 trillion barrels, according to IHS Energy, an oil and gas information-gathering group in Tetbury, England. By adding in Canada's oil sands, the Oil and Gas Journal in Houston raises proven reserves to 1.266 trillion.
"It is not an issue in which there are absolute answers," says Robert Tippee, editor of the Houston trade journal. Much depends on advancing technology and the economics of production, as well as how much oil the ground really holds.
Advocates of a production peak coming soon offer several pieces of evidence:
• Total world oil production reached 68 million barrels per day in 2003, according to a count by the Oil and Gas Journal. That's not much above the 66.7 million barrels per day. in 2001. Oil reserves estimated at 1.266 trillion are up only a bit from 1.213 trillion a year earlier.
• Production has peaked for more than 50 oil-producing nations, including the US (1970) and Britain (1999). China, second to the US in the consumption of oil, was a net exporter of oil until five years ago.
• The Department of Energy predicts world demand will reach 119 million b.p.d. in 2025, with huge increases in China, India, and other developing nations.
• In 2002, the world used four times as much oil as was newly found.
• The rate of discovery of worldwide oil reserves, after declining for 40 years, has slowed to a trickle. In 2000, there were 16 large discoveries of oil, eight in 2001, three in 2002, and none last year, notes James Meyer, director of the Oil Depletion Analysis Centre in London.
• All the giant fields, such as those in the Middle East, have already been discovered, some experts say. These giants are relatively easy to find. The last major oil field, Cantarell, off Mexico's shore, was discovered in 1976.
"The oil companies are drilling fewer and fewer wells," says Colin Campbell, founder of the Association for the Study of Peak Oil, a network of scientists, professors, and government experts. "There are fewer worthwhile prospects to test."
But optimists see another picture.
For example, with scientific advances, oil companies have boosted their drilling success, which means they don't need to drill as many wells. Last year, nearly 40 percent of exploration and wildcat projects located oil, gas, or gas condensate, according to IHS Energy.
Besides conventional oil, there are huge amounts in Canadian oil sands, Venezuelan heavy oils, and Rocky Mountain shale. If oil prices skyrocket, oil in deep offshore fields and in polar regions would become economically feasible to extract. And there's oil from natural gas, which experts see as lasting longer than conventional oil, outside North America.
The USGS added the oil sands to the world's reserves recently, making Canada the second-largest holder of reserves after Saudi Arabia. These sands are already being exploited. But they require the injection of hydrogen to make their tar oil light enough to flow in a pipe.
Meanwhile, estimates of oil reserves keep growing. For example, world oil reserves now are five times as great as at the end of World War II, says Thomas Ahlbrandt, chief of the USGS World Energy Project. And they grew 15 percent in the past five years - without adding in the Canadian oil sands - mostly by upgrading the proven reserves in existing fields.
The world has used up about 930 billion barrels of oil since the 1800s, and has left some 3 trillion in the ground. That estimate includes about 732 billion barrels of not-yet-discovered oil and an assumed growth in reserves in already discovered fields, the USGS reckons. So by now, the world has used up about 23 percent of its total available petroleum resource, Mr. Ahlbrandt calculates. Most people using USGS numbers figure world oil output will flatten in 2036-37, he adds. But non-OPEC oil output could peak between 2015 and 2020.
"I can see no peak for the next 20 or 30 years," says energy consultant Michael Lynch. Since Mr. Lynch has been a keen critic of such early-peak advocates as Mr. Campbell, setting even such a not-so-far-away date is seen as a concession of sorts.
In any case, major oil importers aren't waiting around to find out who's right. The US, Japan, Europe, and China, are scrambling to tie down petroleum resources in the Caspian Sea region, Russia, West Africa, Iraq, Iran, and Libya.
Japan and China are competing for access to Russia's little-tapped Far East oil resources. China, which expects a quintupling of its oil needs by 2030, wants a new pipeline to go from Angarsk in Russia to inland Daqing in its northeastern industrial heartland. Japan proposes the pipeline go rather to Vostochny, on the shore near Vladivostok. One reason Japan is sending 500 soldiers to Iraq this month is to stabilize Middle Eastern oil, the source of 90 percent of Japan's oil, Japan's defense minister, Shigeru Ishiba, told the Financial Times last month.
Pundits say the US has been especially interested in the recent election in Georgia to replace President Eduard Shevardnadze because that nation, though not having reserves itself, is the corridor for a $3 billion pipeline through which huge supplies in Azerbaijan, Turkmenistan, and Kazakhstan must pass through to reach the West. A Chinese oil firm last month embarked on its first international venture by buying a 50 percent stake in a Kazakhstan oil field.
The US has just extended trade preferences to Angola, where oil giants ChevronTexaco and ExxonMobil are preparing to spend billions of dollars on deep-water developments. Other US oil firms, such as ConocoPhillips, Occidental Petroleum, Marathon Oil, and Amerada Hess are looking carefully at their prospects for returning to Libya should the US government lift sanctions on that desert nation.
According to a New York Times report, a step that put Russian oil mogul Mikhail Khodorkovsky in jail was his plan to sell a major stake in his oil company, Yukos, to ExxonMobil. US oil firms would like to invest more in Russia's oil and gas reserves, if they can negotiate that country's legal and political minefield.
The competition for oil resources not fully under contract is expected to get rougher. It could be especially crucial for consumers in North America, who on average use up more than their body weight in crude oil each week.
Many experts suspect that oil was one reason, among others, the US invaded Iraq. America's longstanding concern with its oil supplies is nothing new. Newly declassified British documents suggest that President Nixon was prepared as a "last resort" to launch airborne troops to seize oil fields in Saudi Arabia, Kuwait, and Abu Dhabi to end the 1973-74 oil embargo on the US by the Arab nations.
Some countries - even some oil firms - have decided to invest in solar and wind energy. "This reflects the realization that exploring for large new sources of oil is not a realistic way to go," says Mr. Meyer.
Mr. Deffeyes says the US should have stepped up its research on alternative energies 15 years ago. But others don't see a crisis looming just yet. Certainly nations should be researching better sources of energy, says Mr. Lynch. "But it should not be based on imminent scarcity."