The Yanbu oil pipeline will stretch from the Abqaiq oil field near the Persian Gulf to a port on the Red Sea opposite southern Egypt. The 750-mile line, 48 inches in diameter, will rival the Trans-Alaska pipeline as a work of petroleum engineering.

For Saudi Arabia, the pipeline will provide a substantial boost to the kingdom's concern for the Red Sea.

From the Saudi viewpoint this pipeline-sea-pipeline route for exports provides two types of security for oil.

Sumed, the Egyptian pipeline that parallels the Suez Canal, is considered relatively safe.

In any future Arab-Israeli war, the chances of disruption of Sumed are much less than another closure of the Suez Canal. And of more concern to Saudi Arabia, Yanbu will free the kingdom of its current reliance on the Persian Gulf for all of its oil exports.

Relations between the shah of Iran and the kings of Saudi Arabia have never been very cordial. Despite what some observers see as Iranian-Saudi common interests with respect to the events in Afghanistan and the Horn of Africa, the Saudis still harbor a degreeof suspicion toward the shah.

The Saudis remember his occupation of the Tumbs Island made one day after the British withdrawal in 1971 from the United Arab Emirates. They are unhappy with what they see as a permanent station for 5,000 Iranian troops in Oman now that the insurrection in that country is over. Their long-standing - and now dormant - claim to Bahrain also caused friction.

Saudi Arabia today has better ties with Iraq and its radical Baathist leaders than it enjoys with Iran. This is understandably disputed elsewhere, but Iraq is definitely in league with Saudi Arabia in the desire for Arab solidarity against Israel and any other perceived enemies of Islam.

The recent riots in Iran are no consolation to the Saudis, either, since they involve their religious and ideological allies of orthodox Islam against the shah's strides toward modernization.

Apart from the obvious concern with Soviet ambitions toward the Gulf, the Saudis are anxious to see an alternative oil route in the Red Sea to avoid disruptions by Iran. With Yanbu, they can develop some limited alternatives.