After a brief lull in the first half of 1980, world oil prices will take off again, with OPEC's present $24 base soon hitting $30 a barrel, several oil experts predicted today.

"To my view, a base price around $30 a barrel is likely to be achieved by the end of 1980, an increase of another 23 percent on top of the current OPEC average price," Anthony Copp, an energy specialist with Salomon Brothers, New York investment bankers, told a session on oil pricing at the annual meeting of the American Economic Association.

"I have no quarrel at all with that forecast," M. A. Adelman of MIT, a world oil market expert, declared.

Several members of the Organization of Petroleum Exporting Countries announced price hikes last week, with Libya going all the way to $34 a barrel. Saudi Arabia, which produces nearly one-third of OPEC oil, is selling its oil for $24 a barrel, up from $18 a few weeks ago.

Even with the latest round of OPEC increases, economist William Prast of Columbia University said he expects a far smaller increase in refined product prices during 1980 than the 60 percent or so jump this year. Part of the reason will be "flat demand" for energy in the industrial nations.

If Prast is right, profit margins for refiners, distributors and retailers of petroleum products, which increased sharply this year, will be squeezed.

An encouraging note was a prediction of declining spot market prices for crude oil in the new year's early months. "Barring unforeseen events," Copp said, "a higher contract price . . . will reduce the attractiveness of paying close to $40 a barrel for spot crude. In the short run higher official-based prices will bring down spot prices.

"My concern is that the short run may last for only about half a year. By the end of 1980, it is possible to witness another jump in the spot rates."

If spot prices do come down early next year, that will offset a significant part of the latest round of OPEC increases. In November, according to Carter administration energy officials, about 20 percent of crude oil imports was bought at spot market prices. Should spot prices drop to the $32-to-$35 range, that would be an $8-to-$10 drop for that one-fifth of imported crude.

For the longer run, none of the economists on the panel had anything but gloomy words for oil consumers.

David Nissen of Chase Manhattan Bank said a combination of high inflation and an expected slower pace of economic development in oil-exporting nations has produced a situation in which the exporters' best investment opportunity may well be leaving the oil in the ground. If so, they can be expected to produce only enough to cover current cash needs, Nissen said.

Copp predicted that "nominal prices of between $50 and $75 per barrel are likely to be achieved long before the end of the coming decade. Such a pricing outlook has enormous implications for the international monetary system, the debt problems of less developed countries, not to mention the political difficulties in the United States of coping with $2.50 to $3 per gallon prices for motor gasoline."

Albert Danielson, a University of Georgia economist, also predicts the Saudis "to adjust their price upward to the $30 range" by the end of next year. Danielson said OPEC's power is so great that it can raise prices even as demand from the industrial nations is dropping because of slower economic growth, higher oil prices, and the fact that most of the world's storage tanks are full.

At previous meetings of the American Economic Association, as Chase Manhattan's Nissen noted, energy economists regularly were predicting that oil prices would eventually decline in real terms -- that is, they would be going up less than other prices. Today no economist wanted to climb out on that limb.