October 19, 1986

In an unexpected shift, Saudi Arabia today dropped its demand for a major overhaul of OPEC's production-sharing system. The move, in which the Saudi Oil Minister, Sheik Ahmed Zaki Yamani, acceded to the position of a group led by the Iranian Oil Minister, Gholam Reza Aghazadeh, paved the way for the extension of a temporary accord, now in force, that is intended to block a collapse of oil prices. Despite the breakthrough in the 13-day-old talks here, the shift meant that oil ministers from the Organization of Petroleum Exporting Countries fell short of their declared goal of setting permanent production quotas, based on objective economic criteria, for all 13 members. The effect of the move could be a steadying of oil prices worldwide, at least in the short term.

ALL along, the plot had been too good to be true: Tom Seaver returning to Shea Stadium with the Boston Red Sox to pitch against the Mets in the World Series that opened last night. And on the day last June when the 41-year-old right-hander was traded to the Red Sox, he understood the odds against that possibility. ''If it does happen, I'd want to beat the Mets badly,'' he said then. ''But first, a lot of other things have to happen.''

THE race for State Senate in the 36th District centers on the question of whether the incumbent, Suzi Oppenheimer, a Democrat, ''gets the job done,'' as she says, or whether, as her Republican opponent, Willis H. Stephens Jr., asserts, the salary paid her is a ''waste of taxpayers' money.'' Mrs. Oppenheimer, 51 years old and a former four-term Mayor of the village of Mamaroneck, is completing her first term in the State Senate in the central Westchester district. As Mr. Stephens, 30 years old and a resident of Port Chester, sees it, Mrs. Oppenheimer has been ineffective for two main reasons: she is a Democrat in a State Senate that is controlled by the Republicans, and she ''doesn't have the respect of the Republican leadership.'' ''She's basically just occupying a seat,'' Mr. Stephens said recently. ''The record is very clear that a lion's share of the legislation introduced under her name has not been passed.''

Thirty years ago, in the bayous of Louisiana and the cotton fields of Mississippi and other Southern states, it was unthinkable that a black would run for a seat in Congress - never mind stand a chance of winning. And few would have believed that the day would come when blacks, who were by and large barred from voting by well-enforced Jim Crow laws, would be in a position to help determine who wins or loses an election. But it has come down to this: Not only do Louisiana blacks have an opportunity to elect this state's first black Representative since Reconstruction, but they could also be the decisive factor, if the vote is close, in whether Louisiana will elect its first Republican Senator in more than a century or keep the seat at stake in Democratic hands as the Democrats drive for control of the Senate. Allegations of Intimidation Today, black candidates in Louisiana, Mississippi and several other states are running strong in contests for an assortment of political offices. Moreover, black voters are being courted as never before by Republicans as well as Democrats. History has shown that blacks turn out heavily when there are black candidates.

Roberto Benigni, whose comic performance as an Italian tourist is one of the highlights of Jim Jarmusch's ''Down By Law,'' spoke only one word of English before he arrived in New Orleans for the filming. Since the word was ''goodbye,'' it didn't help much until he was ready to leave. He never read the full script of the movie, he could hardly communicate with the other actors and he barely understood his own lines. Why? ''They were in English,'' he said with a heavy Italian accent, crammed with vowels, ''I no spoke-a the Engaleesh.'' But Mr. Benigni doesn't seem to need words to communicate. Charming and effusive, with thinning long black hair that has a tendency to stand out around his head as though charged with his own electricity, the 34-year-old actor and director from Tuscany speaks with his eyes, his body and his hands. He leans forward, reaches out, smiles, making his points with a gesture or a touch. He speaks with the same careful, slow enunciation of his screen character, in an Italian accent so familiar from parody as to almost seem artificial -an Italian imitating an Amerian trying to sound Italian - like a film negative of Chico Marx, one of Mr. Benigni's favorite comedians.