The price of a barrel of West Texas Intermediate (WTI) crude oil has fallen from more than $100 a barrel in late June to less than $60 a barrel. While the broad outline of the reason for the drop is simple — supply is outstripping demand — the devil, as always, is in the details.

Demand is dropping largely because global economic growth has slowed. The emerging economies of Brazil, Russia, India and China have faltered or gone into reverse. The developed economies of Europe are teetering on the edge of another recession, and U.S. economic growth, though better, is erratic. Add to this lower demand for transportation fuel as automakers build more fuel-efficient vehicles.

On the supply side, North American shale oil has dramatically changed the picture. U.S. crude oil production is at a 40-year high and shows little sign of slowing down. OPEC has said it will not cut production as it fights to keep market share, and Russia needs to produce and sell as much oil as it can to keep its economy from collapsing. Thus, no cut in supply, at least not yet.

That potential supply is filled by global proved oil reserves that totaled 1.635 trillion barrels in January 2013. At the current global consumption rate of about 90 million barrels a day, those global reserves will last about 50 years.

Of the top 10 countries holding portions of those reserves, only Canada does not have a national oil company, and the nine that do control 1.23 trillion of the world’s total proved reserves. That is about 75% of the world’s proved reserves that are off-limits to private oil companies.

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By comparison, the portion of the world’s total proved reserves owned by the 10 largest oil companies is about 75.23 billion barrels, or 4.6%.

The world’s largest oil companies are in something of a bind. Most made investment decisions several years ago that did not take into account the impact that shale oil would play. In 2009, North Dakota produced just 218,000 barrels of crude a day. Today it produces more than a million barrels a day.

The big oil companies had begun making investments in large and costly offshore oil and gas projects and in Canada’s oil sands, because that is where the best opportunities appeared to be. Horizontal drilling and hydraulic fracturing (fracking) had not yet proven their effectiveness. As a result, none of the top 10 companies is much of a factor in the North American shale bonanza.

The massive costs of many of these huge offshore and oil sands projects were justified by an assumption that oil would sell for more than $90 a barrel. Until June that was still true. Now, however, the situation is different, and Big Oil may run into some cost problems. Still, they do have one big positive — their proved reserves.

Even the largest unconventional producer in the United States, Continental Resources Inc. (NYSE: CLR), claims less than a tenth the proved reserves of the largest of the Big Oil companies. If they must, the top companies can just leave the oil in the ground until the price rises. Many smaller shale producers may have to sell or even file for bankruptcy if prices fall below $50 a barrel.

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What follows is a look at the top 10 oil companies in the world based on proved reserves. Proved reserves, by definition, are those that have a “reasonable certainty” of being extracted at current economics. That certainty is often quantified as 90%. Of course, the proved reserves total will rise and fall with new discoveries, production and, obviously, market price. If it is economically feasible to pump a barrel at $90, it may not be economically feasible at $50, for example.

The companies in our list are all at least partially publicly traded on a U.S. exchange, even though a couple are controlled by their country’s governments. Company data were gathered from S&P Capital IQ. Reserves and production figures do not include natural gas or non-oil liquids.

Here are the top 10 oil companies in the world based on proved reserves of oil.

10. Canadian Natural Resources
> Proved Oil Reserves: 3.513 billion barrels
> 2013 Oil Production: 151 million barrels
> Enterprise Value: $44.24 billion
> Revenues: $16.482 billion
> Net Profit: $2.812 billion

Canada’s bitumen deposits (oil sands) have pushed the country’s proved reserves to the third highest total in the world, 173.1 billion barrels, behind only Venezuela (297.6 billion) and Saudi Arabia (267.9 barrels). This company’s crude reserves include about 2.7 billion barrels of bitumen and synthetic crude; the rest is conventional crude. The company’s CEO has already said that Canadian Natural Resources Ltd. (NYSE: CNQ) would reduce capital spending in 2015 and that he thinks crude oil prices will stabilize in the $70 to $75 range. Most of the company’s reserves are located in Canada, but it also has assets in the North Sea and offshore of West Africa.

9. ConocoPhillips
> Proved Oil Reserves: 4.779 billion barrels
> 2013 Oil Production: 258 million barrels
> Enterprise Value: $94.09 billion
> Revenues: $57.461 billion
> Net Profit: $9.395 billion

ConocoPhillips (NYSE: COP) spun off its refining and marketing business to Phillips 66 (NYSE: PSX) in 2012 and is now a pure-play exploration and production (E&P) company. Of its total proved reserves, about 2.75 billion barrels are crude oil and 2 billion are bitumen in the Canadian oil sands. Conoco has already announced a cut in 2015 capital spending, most of which will come in its unconventional (shale) plays outside North Dakota and Texas. The company has operations in Alaska, the Lower 48, the North Sea, the Middle East and South Asia.

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8. Suncor Energy
> Proved Oil Reserves: 4.372 billion barrels
> 2013 Oil Production: 193 million barrels
> Enterprise Value: $46.665 billion
> Revenues: $36.475 billion
> Net Profit: $2.735 billion

Suncor Energy Inc. (NYSE: SU) is the leading producer of synthetic crude from bitumen in the Canadian oil sands. All but about 330 million barrels of Suncor’s reserves are one of these two types. The company also has assets off the east coast of Canada and in the North Sea, as well as onshore assets in North America, Libya and Syria. The company also owns and operates the largest biofuels plant in Canada, making 400 million liters of ethanol a year.

7. Total
> Proved Oil Reserves: 5.413 billion barrels
> 2013 Oil Production: 426 million barrels
> Enterprise Value: $149.675 billion
> Revenues: $212.723 billion
> Net Profit: $11.56 billion

About 20% of Total’s reserves are bitumen from its operations in Canada, but the majority of the France-based company’s reserves are in the African nations of Angola, Gabon, Nigeria and Congo. Total S.A. (NYSE: TOT) also holds reserves in the North Sea, Canada, Argentina, Venezuela, the Middle East and Asia. Total is a 50/50 partner with ConocoPhillips in phase two of the Surmont project in Alberta’s oil sands. Neither company has revealed the cost of the project, but an estimate in 2010 when the project was announced put the price tag at $3.3 billion.

6. Chevron
> Proved Oil Reserves: 6.345 billion barrels
> 2013 Oil Production: 632 million barrels
> Enterprise Value: $210.71 billion
> Revenues: $204.024 billion
> Net Profit: $20.7 billion

Chevron Corp. (NYSE: CVX) has less exposure to the Canadian oil sands than many other companies on this list. Of its proved reserves total, only about 750 million barrels are bitumen. Of the remaining 5.6 billion barrels, 1.33 billion are located in the United States, 1.1 billion are in Africa and the rest are counted in Asia, Australia and Europe. Chevron has little exposure to shale oil at present, but it does hold leases in the Permian Basin.

5. Royal Dutch Shell
> Proved Oil Reserves: 6.621 billion barrels
> 2013 Oil Production: 564 million barrels
> Enterprise Value: $222.906 billion
> Revenues: $437.974 billion
> Net Profit: $16.06 billion

Royal Dutch Shell PLC (NYSE: RDS-A) has been shedding assets all year and postponing expensive projects in an effort to improve shareholder returns. The company plans to sell $15 billion in assets by the end of next year and has already parted with about $12 billion. The company’s E&P head said in late November that the company tests all its projects at a crude oil price of $70 to $110 a barrel and that Shell had no plans to increase its divestitures. Oil was priced at around $80 a barrel then. Now that crude has fallen to around $60 a barrel, the Anglo-Dutch giant may be rethinking its plans. About 2.15 billion barrels of Shell’s reserves are located in the Canadian oil sands.

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4. BP
> Proved Oil Reserves: 10.07 billion barrels
> 2013 Oil Production: 733 million barrels
> Enterprise Value: $133.556 billion
> Revenues: $373.783 billion
> Net Profit: $9.229 billion

Since the April 2010 explosion at the Macondo well in the Gulf of Mexico that killed 11 workers and spilled millions of barrels of crude into the sea, BP PLC (NYSE: BP) has sold more than $43 billion worth of refining, transportation and production assets. The U.K.-based company plans to sell another $10 billion worth of assets, but it may find current low crude prices to be a serious headwind. BP expects to begin production on its first oil sands project this year and has two more in the works. The company is also a non-operating partner in a few Eagle Ford and Anadarko shale plays.

3. PetroChina
> Proved Oil Reserves: 11.314 billion barrels
> 2013 Oil Production: 932.9 million barrels
> Enterprise Value: $362.749 billion
> Revenues: $379.553 billion
> Net Profit: $21.236 billion

PetroChina Co. Ltd. (NYSE: PTR) is the one of two companies on this list that is controlled by its government. The Chinese government owns about 86% of the company’s stock through its ownership of China National Petroleum Company, PetroChina’s parent. More than 60% of the company’s proved crude oil reserves are located in China. The company has been a purchaser of foreign assets for about two years, and it is expected to spin off parts of two of its Chinese operating companies next year as part of a plan to dilute government ownership of the company.

2. Petrobras
> Proved Oil Reserves: 11.04 billion barrels
> 2013 Oil Production: 715.4 million barrels
> Enterprise Value: $142.534 billion
> Revenues: $146.297 billion
> Net Profit: $9.083 billion

Petroleo Brasileiro S.A. (NYSE: PBR), or Petrobras as the company is widely known, hit the big time in oil reserves with the discovery of deepwater assets that have jumped the country’s total proved reserves to 15th in the world with 13.15 billion barrels, of which Petrobras holds about 85%. The Brazilian government owns 48% of the company’s stock and controls virtually every decision the company makes. Petrobras added 1.22 billion barrels to its proved reserves in 2013, but the company’s problem is not how much oil it has, rather how much it does or doesn’t produce and the price that the government will allow the company to charge for its refined products. Debt levels are climbing too as the cost for developing the company’s offshore assets is massive.

1. Exxon Mobil
> Proved Oil Reserves: 11.76 billion barrels
> 2013 Oil Production: 709 million barrels
> Enterprise Value: $401.5 billion
> Revenues: $392.843 billion
> Net Profit: $34.3 billion

Like all but a few of the companies on this list, Exxon Mobil Corp. (NYSE: XOM) holds a good-sized piece of the action in Canada’s oil sands. The portion of the company’s reserves that are down to bitumen and synthetic crude totals about 4.2 billion barrels. Like its mega-sized peers, operations are spread around the globe. Also like essentially all of its peers, the company has been a late-comer to the shale oil explosion. Still, it is not too late for Exxon and the others to catch up, and the falling price of crude could help them with that.

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