The world faces possible oil shortages as early as 1981 and is certain to lack adequate energy supplies around the turn of the century if drastic action is not taken immediately, according to an international study released yesterday.

The Workshop on Alternative Energy Strategies, a 15-nation group backed by the Massachusetts Institute of Technology, went further than President Carter's outline of the problem and painted an even bleaker picture than most previous studies.

Only measures "imparalleled in peacetime" will bridge the looming gap long enough for renewable energy sources such as the sun and nuclear fusion to take over in the next century, when oil, coal and gas run out, the study said.

"This is not a doomsday report. It's a time bomb," said project director Dr. Carroll L. Wilson of MIT at a news conference. "We've tried to pin down ways in which it will explode if the free world doesn't act soon enough."

The shortage of energy around the year 2000 will occur even if coal production more than doubles, oil demand growth rates are halved, nuclear power use is increased 25 times and oil prices rise by 50 per cent, the report warned.

"If the world just drifts along . . . the gaps will cause increasing competition for decreasing energy supplies, with all the political and price effects that might produce," the report said.

The worst-case scenario of the three-year study suggests that Saudi Arabia, the world's largest oil exporter, could trigger a world oil shortage as early as 1981 by deciding that its vast oil reserves are worth more in the ground than new floods of money which it already finds difficult to spend.

Demand will start pushing oil production ceilings in 1981 unless Saudi Arabia increases its output beyond the current 9 million to 10 million barrels a day, the report continued. If offered no hope that alternative energy supplies and current demand patterns might change much by then no matter what is done.

The report discusses scenarios assuming international economic growth at 3.5 per cent, described as low, or 6 per cent, called high, in 1985. The range used for 1985-2000 is 3 per cent to 5 per cent, but many nations have historically fallen short of even the lower limit.

The report also assumes crude oil prices rising by no more than 50 per cent, to $17.25 per barrel, before 2000. The level was "chosen arbitrarily," the report said, although real prices have risen more than 300 per cent in the last four years.

A combination of lower international growth rates and higher oil prices than the report uses would presumably stimulate production to meet demand so "that there would be no prospective gaps in any fuel, and that the peak in oil supply would not occur until after the end of the century," the report said. "We did not analyze this case in full detail . . . it is only a delay, not a solution."

"The book is written already" on the situation in 1985, said Thornton F. Bradshaw, president of the Atlantic Richfield Co. and one of five workshop participants from the United States. "We can't change lifestyles by 1985 and can't even change too much be the year 2000, but we can set things in motion," he said.

The workshop report, complied by 35 academicians, industrialists, scientists and government advisers from 15 nations, rejected the idea that nuclear power or coal power alone could solve the problem.

"Even if all lights turned green very soon and all over" for nuclear power plant construction and all environmental objections suddenly evaporated, Wilson said, supply and startup times are such that nuclear power could meet only 9 per cent of projected world energy demand by 198 and only 21 per cent by the year 2000.

At the same time, oil demand in 2000 will outstrip supply by 15 million to 20 million barrels a day, or as much as the current daily U.S. consumption even if oil production is at its maximum, the report said.

"Once again, coal may have to sustain industrial production and economic development throughout the world," it said. To meet the demand, the United States with half the non-Communist world's known coal reserves, would have to more than triple coal production to 2 trillion tons annually.

Meeting the demand also will require massive world nuclear power production, intensive energy conservation efforts, new oil discoveries and gradual conversion to renewable fuel sources such as solar energy, all at the same time, the report said.

President Carter's energy program "defined the problem and set us off in the right direction," Bradshaw said, "but I don't by any means think he's gone far enough."