OPEC'S MEETINGS are always a useful reminder of the political geography of oil -- where it comes from and how its price is set. Currently it's being set by OPEC's limits on production -- limits that the member governments, remembering last year's price collapse, are now observing much more carefully than has usually been their custom. The meeting that ended last weekend was remarkably short and serene. The final agreement was a compromise between Iran's demands for higher prices and Saudi Arabia's lower-price strategy -- and once again the compromise has been tilted slightly in favor of Iran. It is calculated to raise the price slowly from the present $18 a barrel as winter comes and demand rises.

In the view from Washington, the striking thing about this meeting is that neither the OPEC governments nor the infinitely sensitive oil markets seem to fear that the flow of oil through the Persian Gulf might be cut off. President Reagan is talking about going to great lengths to ensure freedom of navigation in the Gulf. But the Gulf countries don't appear greatly concerned by the danger to shipping.

One reason is that all of them have been at work building pipelines to reduce their dependence on the Gulf. Iraq is about to open a large new line that runs through Turkey to the Mediterranean. Iran, according to The Wall Street Journal, is working on a line to carry its oil overland around the Strait of Hormuz to a port on the open sea.

There's good reason to keep American naval ships in the Persian Gulf. But the reason is to give visible support to the Arab states, now under pressure from Iran. The degree of that pressure is accurately measured in the OPEC meetings. The Saudis lost the initiative there last summer in part because of Iran's gains in the war. The Arabs are now avoiding open quarrels with Iran and are prepared to accommodate Iranian interests by pushing oil prices cautiously upward.

The most imminent threat to Persian Gulf oil supply is not that Iranian planes and missiles will shut off tanker traffic but that Iranian political influence will induce the neighboring Arab states, with their huge capacity, to cut production and force up prices. That would be very good for oil-exporting countries with limited reserves, such as Iran. And it would be very bad for the rest of the world.