The Growing gap
This graphic is worth careful study. It shows oil discoveries and oil consumption since 1930 to 2008. The black line shows oil consumption. Notice the peak in consumption in 1979 corresponding to the first oil crisis. The subsequent 5 year decline in oil consumption is attributed to more fuel efficient transportation and a slowing world economy. The grey bars show oil discoveries. Notable grey bar features include Kuwait's big oil field, Burgan, which was discovered in the late 30s and Ghawar, the world's largest oil field, which was discovered in 1948. Note that the discovery rate peaked around 1966. Note also that consumption exceeds discoveries every year since 1984. Now there is a large gap between discoveries and production. None of this is controversial--it is only history.
What happens after 2008 is extrapolation and speculation. The EIA  (Energy
Information Agency) has projected a 1.6% annual growth in oil demand which is shown in
red. Developed countries, for example the USA,
Germany and Japan are not expected to increase consumption. In fact, consumption might
decrease because of efficiency gains. But China and India both have booming economies.
Automobile ownership increased by 37% in China and 17% in India in 2007.
The yellow bars represent a guess about yet-to-find oil. The yellow bars show no declines in the discovery rate until 2021. That seems optimistic given the declining discovery rate in the previous decade.
Note the growing gap between discoveries and production!
Oil discovered 40 years ago is the basis of current oil production. The search for oil
continues but projected oil discoveries will contribute little to projected oil
production in 2030. The declining rate of oil discoveries makes it painfully
obvious--most of the oil has already been discovered. The technology for finding oil
has improved greatly since the major discoveries, yet little oil has been found in
recent years. THe heyday of oil discovery was from 1950 to 1980. It is difficult to
avoid the conclusion--most of the oil has been found.
There is a growing gap between discoveries and production.
World oil production is running flat out. Only the Saudis claim to have the ability to produce more though some dispute this. It is not a simple matter of turning a spigot or pumping faster. Oil fields can be permanently damaged by attempting to produce too fast.
Soon there will be a gap between production and demand.
It Gets Worse
According to BP (British Petroleum) world oil reserves stand at 1238 billion
barrels. At present (2008) yearly world oil production stands at 31 billion barrels.
There is enough oil to last 40 years if production holds constant and no new oil is
found. According to BP, the Middle East has 61% of the world's oil reserves. Africa
has 9.6% and the Russian Federation has 6.4%. The two countries sharing borders with
the United States, Mexico and Canada, together have only 3.2%. Venezeula, a short
distance away via oil tanker, has 7%
The United States possesses 2.6% of the worlds oil reserves while it consumes 24% of the world's oil production.
Although the United States has only 2.4% of the world's oil, it produces 9.2%. If the production rate could be maintained, the oil will be gone in 11 years. The figures for Canada are the same and they are worse for Mexico. The Middle East has enough oil to last 88 years at present production rates. Africa has 33 years. Clearly the United States will be increasingly dependent on oil imported from those places. It is impossible to consider oil independence in light of these numbers.
The majority of the world's oil comes from old oil fields. For example, Kuwait still supplies 3% of the world's oil from a 70 year old field. The world's largest oil field, Ghawar, a 57 year old oil field, still supplies 5% of the world's oil. The North Sea (discovered in 1963) was exploited very quickly and is now in steep decline. Alaska's Prudhoe Bay (discovered in 1968) is now a trickle.
Oil varies greatly in quality. Some oil is so light and sweet (low in sulfur) it can be pumped directly into the fuel tank of a Diesel truck. Some oil is more like tar and it may contain sulfur. It's hard to transport and natural gas may be needed to refine it into useful fuel. The oil from Manifa, a large oil field in Iran, is an extreme example. It contains so much sulfur and vanadium it can't be refined using today's technology. The average quality of oil is declining because the best quality was produced first.
Oil varies greatly in accessibility. It is convenient to access Kuwaiti oil. Oil tankers in the Persian Gulf load from nearby Kuwaiti oil wells. It is inconvenient to access oil from the north slope of Alaska. It was necessary to build an 800 mile pipeline over mountains and permafrost to reach the oil in Prudhoe Bay. Oil drilling platforms can reach oil in mile deep water but only at great expense in money terms and in energy terms. There is oil in the arctic but oil drilling platforms will have to deal with ice and deep water to access it.
The remaining oil will be expensive and difficult to produce, refine and transport.
ASPO (Association for the Study of Peak Oil & Gas Ireland) publishes a monthly
newsletter which is well worth reading. It always contains this graphic which is
updated yearly. The colored parts have been added.
 http://www.bp.com/ British Petroleum
(BP) publishes the annual Statistical Review of World Energy. The Review is
widely referenced because it is convenient, complete, colorful and very well done.
However, the data do not reflect the company's own assessments--it is simply
republished data from other sources. One major source is the Oil & Gas Journal
but its sources are suspect as well. They get their numbers by simply asking
government officials. The numbers for the United States are probably reliable because
the oil companies are regulated by the SEC (Securities and Exchange Commission.) The
numbers for Norway and Britain are probably reliable as well. However, the numbers for
the Middle Eastern countries are whatever the countries say they are. They treat oil
reserve numbers as state secrets. The bad news is that the Middle Eastern countries
have reasons to overstate their reserves. Planetforlife takes these numbers at face
value mainly for expediency and convenience.
 http://www.eia.doe.gov/ This is "official information from the U.S. government."