Americans are aware in general that the economies of the West are vulnerable to a cutback in oil deliveries from the OPEC countries. But they may be horrified to learn just how damaging such a disruption -- say, as the result of revolution in Saudi Arabia -- could be, despite current surplus supplies of crude.
Karim Pakravan, an economist doing research at the Hoover Institution, Stanford University, has made some calculations of the impact of oil delivery interruptions of various magnitudes. The results are not reassuring.
For instance, if there were a one-year disruption in 1983 of 9 million barrels a day -- approximately the production of Saudi Arabia -- it would prompt a recession nearly twice as bad as that in 1973-75. That recession was the worst since the Great Depression of the 1930s.
Mr. Pakravan's mathematical model indicates that losses in real gross national product (GNP) in the noncommunist industrial countries would amount to services produced in a nation or nations.
The United States, with huge production of its own and some emergency stockpiles, would suffer ''only'' a decline of $136 billion, or 4.8 percent in GNP. That would still be a serious recession.
Western Europe, which is so highly dependent on OPEC oil, would see its output drop $250 billion, or 12.8 percent. Under the International Energy Agency agreement, some of the available oil would be redistributed to those nations hit hardest. Nonetheless, such nations as West Germany, France, and Italy would suffer widespread plant closings and sharply rising unemployment. Presumably Britain and Norway, with their own oil sources in the North Sea, would be less hurt.
Japan, the Pakravan calculations show, would lose $127 billion, or 9.9 percent of its GNP.
Pakravan admits that his model does not give precise answers to the extremely complex situation arising from oil cutoffs. In fact, one economist listening to the Pakravan paper, given at a meeting here last week of the Middle East Economic Association, noted that similar ''econometric'' models badly underestimated the harm done by the quadrupling of oil prices by OPEC in 1973.
Nonetheless, Pakravan believes his work will give policymakers a better idea of likely effects from various degrees of oil cutoffs and thus offers some help in making policy decisions.
He figures that the costs associated with a one-year, 3 million-barrel-a-day interruption in oil deliveries would be limited. One reason is that OPEC as a whole still has excess production capacity. Western Europe, for instance, would lose $38 billion, or 2 percent of GNP, in 1983. The US would lose $22 billion, less than 1 percent of its GNP.
But if the Strait of Hormuz were blocked and all Persian Gulf oil deliveries stopped for a year, the results would be economically disastrous. Indeed, Mr. Pakravan tried to calculate on his model the impact of a year-long, 18 million-barrel-a-day interruption in oil delivery in 1983 and the results were such that he does not regard them as plausible. GNP in the US would decline 12.1 percent; in Western Europe, 37.5 percent; and in Japan, 37.3 percent.
The Pakravan paper offers other interesting conclusions from its tests of various assumptions:
* As the size of the oil delivery interruption got bigger, the damage to the economy would not increase proportionately; it would get worse even faster. For example, a tripling of the reduction in supplies from 3 to 9 million barrels daily in 1985 would increase the costs almost seven times for the noncommunist industrial countries (OECD) as a whole.
That's because the OECD nations can find substitute energy sources relatively easily at lower levels of disruption. But once those subsitute energy sources ran out, plants would simply have to be closed for lack of fuel.
* In the cases of 6 and 9 million-barrel-a-day disruptions, the relative costs to the industrial countries would decline as the decade advanced. That is because the industrial countries are still adjusting to the higher prices of oil and will make more progress in this regard as the years go on.
Pakravan notes that this has ''important political and strategic implications.'' It means the early 1980s will be the period of maximum military and political vulnerability for the West.
* The non-OPEC developing countries would not experience large losses as a group. That's because some of these nations produce oil and would benefit from windfall profits as the oil disruption raised prices dramatically.
* Delivery disruptions would result in further large transfers of income from oil importing nations to major oil exporters. For instance, a 9 million-barrel-a-day interruption would increase OPEC revenues as a whole by $ 395 billion in 1985. Mexico, which is not a member of OPEC, would gain by $59.6 billion. (Of course, if a member of OPEC could not deliver oil, it would lose out.) Such transfers would have ''possible major effects on the world monetary system and the economies of OPEC nations,'' Mr. Pakravan said.
World oil production (millions of barrels, daily) 1973 1980 OPEC Persian Gulf 20.60 18.00 OPEC-other 10.35 9.15 Total OPEC 30.95 27.15 Noncommunist developed 13.50 14.00 Noncommunist less developed 1.20 6.60 Total noncommunist non-OPEC 14.70 20.60 Communist economies 13.00 14.00 Total 58.65 61.75 Dependence ratios (percent) Noncommunist on OPEC-Persian Gulf 45.60 37.50 Noncommunist on OPEC 68.50 56.30 Source: Petroleum Economist