RIYADH, Saudi Arabia – Exxon Mobil Corp. is no longer the biggest oil company (that would be Saudi Aramco). It is no longer the richest oil company (PetroChina). It is not even the leader among the international oil companies in replacing production with new reserves (ConocoPhillips, a U.S. firm, at least).

Dr. Subroto, a former OPEC secretary general from Indonesia, said this month that the future no longer belongs to the Exxon Mobils of the world.

Seventy-eight percent of the world's proven oil reserves are in OPEC countries, which have their own oil companies develop those often inexpensive-to-produce reserves.

Exxon, BP, Chevron and Shell work in parts of the world with far fewer, more expensive reserves – on the periphery of the Arctic, the distant offshore of Africa and the deepwater of the Gulf of Mexico.

From these costly projects they help squeeze about 60 percent of global oil production, and it is difficult to see how that share will do anything but decline.

"You can make the calculations very easily," Dr. Subroto said. "The role of the national oil companies will be growing greatly while the international oil companies more and more will be diminishing into the background."

If Dr. Subroto is correct, the consequences go beyond Exxon.

National oil companies, from Gazprom in Russia to Pemex in Mexico to the National Iranian Oil Co., are doing a poor job of investing in production. They are setting up the world for a slowdown in economic growth when oil demand exceeds the supply controlled by the national oil companies.

A recent report by the U.S. Congressional Research Service ("The Role of National Oil Companies in the International Oil Market") found little the United States could do about this. Curbing oil consumption led the list of recommendations.

Rex Tillerson, Exxon's chairman and chief executive, spoke at the World Energy Congress in Rome this month with a plea for the governments that own oil reserves and national oil companies to open up.

"At a time when we should open doors to trade, resource nationalism closes them. At a time when we should be building bridges of international partnership, resource nationalism builds walls," he said.

So what does the Irving behemoth have going for it? Company managers argue that nobody does oil and natural gas better than Exxon Mobil. The company's technologies, engineers and managers work to the standard that no other company will get more oil out of a field than Exxon.

Reservoir management is certainly important in a world where new reserves are hard to find. Even here, though, Exxon has challenging times ahead.

Alan Kelly, an Exxon vice president who led a recent National Petroleum Council study of the future of oil and natural gas, told an OPEC symposium here that the oil companies don't see where the oil will come from to meet demand.

The council, which advises the federal government about petroleum issues, put out an alarming report in July called "Facing the Hard Truths About Energy."

The report includes a consensus forecast among international oil companies that projects world oil supply will reach 107 million barrels a day by 2030 (up from the current production of 86 million barrels a day).

That forecast is a good 10 million barrels a day less than demand forecasts from the U.S. Energy Information Administration and the International Energy Agency.

The oil company forecasts point up the consequences of barring the door for exploration and production in resource-rich nations, whether those keeping others out are members of OPEC or not.

Russia, Mexico and Bolivia, all outside of OPEC, have large reserves of oil and gas and excellent prospects for giant discoveries. Under current laws in those countries, however, the participation of an Exxon in exploration and production is problematic, if not banned.

OPEC members generally have a similar disregard for the private oil companies. Exxon is investing heavily in offshore Africa, with large fields in production off Nigeria and Angola, and more such projects in the works.

Last week, the company signed a deal with Libya to explore for oil 110 miles off the Libyan coast.

This is tough, expensive oil to produce. The low-hanging fruit gets plucked by the national oil companies.