The question seems straightforward, simplistic even. But just a cursory glance at the state of the world's remaining oil leads one to think otherwise.
It is a truism to say that oil is the most vital energy source currently known to man. And yet, surprisingly, the foundations of the commodity's "reserve" figures are built on geopolitical sand.
Throughout the age of oil, it has suited both governments and corporations to mislead the public, investors, each other and the marketplace on such a regular basis that now no one analyst can know the truth.
Indeed it appears most of the governments and corporations no longer know it themselves, so often have figures been manipulated.
Geologist and oil statistician Jean Laherrere is one of the leading industry figures who casts doubt on government and corporate figures. He says, "What is needed for reserve definitions is good practice and good rules, to which every country in the world agrees."
Nearly half of the world's oil rests
in five Middle Eastern countries
We may be waiting a while for that to happen.
Take two straightforward examples. The first is Royal Dutch Shell. One of the three super majors, this year Shell, as is well known, shed 23% of its reserves almost overnight. Around 4.48 billion barrels.
Just over 20% was in fact discarded in one day. If Shell were to pump their oil at the rate they are doing today, and if they were to discover no more oil in that period, Shell would run out of oil in a decade.
Shell is not alone. El Paso of Houston Texas revised its reserves down by an amazing 43% on 31 December 2003. Forest Corps, which had announced a new field of 49 million barrels, Redoubt Shoal in Alaska, revised it down to just eight million a year later.
The industry is hampered by lack
of reliable oil production data
There are many others. Corporations are of course often listed on stock markets, big announcements boost share prices. They also hate leaking information to competitors. Eventually this creates gross market uncertainty.
Fatih Birol of the International Energy Agency regards today's high prices as a problem companies and governments can overcome. Yet even he told us that "the need for more transparent and comprehensive data is obvious. Investment in new fields is also paramount".
Our second example is a nation state, OPEC member Kuwait. The government says Kuwaitis "hold 10% of the world's total reserves". Yet in 1985 they were faced with a quandary.
OPEC decided to allow member countries to pump only a certain percentage of their reserves. The obvious point being the more reserves you said you had, the more you could pump. The more you could pump, the more money you earned.
So, overnight Kuwaiti reserves near doubled.
"[Kirkuk in Iraq] is a very old field and the idea that suddenly Iraq can produce five or six million barrels per day is just a joke. It's goofy"
Chairman, Simmons & Co
Again, Kuwait currently reports its reserves at 94 billion barrels. Yet it has reported its reserves at 94 billion barrels since 1992. Unchanged, each and every year. This is despite daily production and no significant new finds.
Of course Kuwait, like Shell, is not alone. Iraq's reserves are still those quoted by former president Saddam Hussein. In response to the 1985 Kuwaiti increase in 1987 Saddam announced that Iraq's oil reserves were not in fact 47.1 billion barrels but "reserves of 100 billion barrels".
Not only did production and a leaking infrastructure fail to dent these figures, in fact the opposite occurred. Today they are actually quoted at 112 billion barrels.
Energy investment banker Matthew Simmons, Chairman and CEO of Simmons and Co, a contributor to the Bush-Cheney energy plan, puts it this way.
"We still do not have any reliable data on (Iraq's) two great fields. The most famous one is Kirkuk and we have no new data on that at all. It is a very old field and the idea that suddenly Iraq can produce five or six million barrels per day is just a joke. It's goofy."
Yet OPEC's quota-based income stream has meant that Abu Dhabi (31-92bn), Venezuela (25-56bn), Iran (48.8-92.9bn) and Saudi Arabia (170-257.5bn) have also done the same.
Market reaction has a big role in
shaping policies of big oil firms
And while Saudi Arabia's national oil company Saudi Aramco claims to have 257.5 billion barrels, its recently retired executive vice president Sadad Al Husseini has said there is in fact "130 billion barrels of proven reserves".
Geologist Laherrere says, "OPEC will not change their reporting as long as quotas will be in force. Only when the supply becomes short and quotas useless will OPEC accept to report real estimates."
So who is one to believe? The best bet is to choose 'none of the above'. As well as corporate malpractice and OPEC quotas, political considerations further confuse the situation.
Take the Venezuelanas as an example. They are the fifth biggest exporter to the world market, supplying around 13% of the daily needs of the US. They are one of OPEC's members who are currently welcoming the high oil prices.
"OPEC will not change their reporting as long
as quotas will be in force. Only when the supply becomes short and quotas useless will
OPEC accept to report real estimates"
Jean Laherrere, geologist and oil statistician
This seems to be mainly down to the economic difficulties Hugo Chavez's government is experiencing. So an implied scarcity of reserves, a belief that they are overestimated, may actually suit Venezuela short term.
Others like Saudi Arabia desire price stability and are more complicit with the consumer nations. But then of course if oil reserve figures did prove overestimated, then market prices would spike, a recession would occur, demand would fall and OPEC countries would suddenly find themselves earning less money.
Non-OPEC producer Russia is also a major supplier on the world stage. One company alone, Yukos, pumps around 2% of the world's total daily demand. Yet many of their reserve figures are from the Soviet era.
Political instability in Nigeria has
contributed to price fluctuations
Since the collapse of the Soviet Union, the Russian reserve estimate has fallen by around 30%. It was as long ago as 1993 that a Russian oil minister described his country's reserves as "strongly exaggerated due to inclusion of reserves and resources that are neither reliable nor technologically or economically viable".
Simmons, the energy investment banker, puts it more bluntly: "I don't trust the current Russian figures at all. Globally there needs to be an audit of oil companies. Trouble is there would be a lot of write-downs. A lot. So no one would agree to that."
So, the five big Middle Eastern countries do hold around half the world's remaining oil, of that we can be pretty sure. But how much there really is of it, how much everyone else has and how long it is going to last, may be anybody's guess.