THAT OIL FIRE in Saudi Arabia is an unwelcome reminder of an extremely disquieting reality. Some 40 per cent of the world's oil flows out of the Persian Gulf countries. The economic - and political - stability of every major country in the world except Russia and China now depends on that flow. The fire has shut down a pipeline carrying some 6 million barrels a day, one-tenth of the world's total production. Was that fire an accident?

No one knows yet, least of all this newspaper. If it was merely an accident, and if it can be repaired within a week or two, there will be no effect at all on oil supplies around the world. With the coming of spring, in fact, there is currently an oversupply of oil in the Persian Gulf. A brief interruption can be easily absorbed. But there are other possibilities.

Last December the Saudis made themselves unpopular with the rest of the Organization of Petroleum Exporting Countries by refusing to go along with the full price increase that most of the others set. But the United States wanted the Saudis to keep prices down. The American connection is crucial to the Saudis because, in the last analysis, they haven't any other defender against their larger and more heavily armed neighbors. Since Saudi prices are now lower than those of the other major exporters, Saudi production is rising while most of the others' is flat or failing. The quarrel over prices is apparently being resolved, but in the meantime the Saudis have taken a larger share of the world market. You could draw up a long list of governments and political movements that have an interest in slowing down Saudi oil production.

It wouldn't be the first time that a pipeline in that part of the world suffered a political breakdown. In early 1970 the Trans Arabian Pipeline, carrying Saudi crude oil to the eastern Mediterranean ports, was ruptured in Syria. At first, the explanation was that a tractor had accidentally backed into it. But the Syrians refused to let it be repaired. The effect was to create a shortage in the Mediterranean market. That turned out to be greatly helpful to the new revolutionary government of Libya, which had just opened price negotiations with the major oil companies. Libya won a substantial increase. In retrospect, it is clear that the Libyan negotiations, and the ruptured pipeline, were the beginning of the astonishingly rapid process by which the Arab governments wrested control of pricing away from the oil companies.

But it's also very possible that the Saudi fire is only an accident after all. The Saudi production and delivery system is a thing of vast technical complexity and, as exports rise, it's under increasing strain. Accidents can happen - and they can be very big accidents.

Americans like to think that their government has control of energy policy. They assume, comfortably, that energy policy is something that President Carter proposes in a speech and that Congress spends the summer debating.But there's more to it than that. A lot of our energy policy is being made in Saudi Arabia. That fire in the pipeline sends a message. Translated, it says that we don't have all the time in the world to cut down our dependence on imported oil, and to diversify our sources of supply.