The rugged and capricious North Sea today frustrated repeated attempts to seal off the Bravo platform's runaway well that is pouring 4,000 tons of oil daily into the icy waters and threatening an ecological catastrophe.

Waves of up to 20 feet high drove back the expert team from Houston that is trying to seal the gusher.

They will try another landing on the oil and gas-soaked Bravo platform Tuesday. But weather forecast here offers little cheer. Winds of up to 40 knots threaten another day of high waves that could cause further delay.

The ill winds, however, did blow some good, attacking the hugh oil slick already formed by the gusher. Tonight, a high Norwegian official said it was "highly unlikely" that the gooey mess would ever spoil any shoreline.

The official, Hans Christian Bugge, director of Norway's Environmental Protection Agency, flew out to Ekofisk, the field in which Bravo is the biggest producer. He came back with this description:

The slick has now broken in two and both masses are being driven northward toward the Arctic Circle. One part is about 15 miles long and up to 5 miles wide. The other is about 5 miels by a 1/2 mile.

These bodies, moreover, have been further fractured by the winds into smaller masses, up to 1,000 yards square.

"There is very small chance the oil will reach the coast of any North Sea state," Bugge said. "We let the nature work."

So far, the sea has been to rough even to use skimming boats that sweep up and suck in the oil. Under pressure from Norway's fishermen, the authorities have also refused to attack the slick with chemicals. Like the oil, they are deadly for fish.

But Bugge's optimistic reading assumes that the oil outpour soon will be capped, something that is far from certain.

Moreover, even if the Norwegian, Danish and British shorelines are spared from catastrophe, the oil has already done some unmeasured damage to the mackerel, herring and bream in these waters. All these stocks are overfished in any event, according to experts, and the toxic film of oil, up to one-third of an inch thick, will take a further toll.

(A British marine biologist said Monday that there is a possibility that fish stocks could be wiped out for at least three yhears, the Associated Press reported from London.

(The scientist, Fred Holliday, said the oil may kill the billions of fish eggs now floating on the surface of the North Sea. "It has happened at the worst time," he said, adding that stocks of flounder, sole, haddock, whiting and herring are threatened.)

Bugge's good weather was bad weather for Phillips Petroleum, the Bravo operator, and the team from the Red Adair Oilwell Fire and Blowout Co. of Houston, Tex.

The Adair team, led by Asgar (Boots) Hansen, is trying to maneuver the barge Choctaw close enough to Bravo to lift aboard the heavy capping equipment. The waves stopped them today.

At best, Hansen and his crew will work under extremely dangerous conditions. The Bravo is buried in oil and envelope in gas fumes. One spark and the platform could be turned into a raging inferno.

Attached to the runaway well is a large stack, a blowout protector. It was while this was being bolted into place that the well blew on Friday night. The Hansen team will spend their first day abroad finishing the task of bolting the protector in place. They will then need another day or two to complete the tash of "killing the well" with two "blind rams," equipment armed with sliding metal sleeves to close the hole.

The cause of the blow-out is still unknown. But Gordon Goering, a Phillips vice president, tonight acknowledged that the company believes a human fault was responsible.

The likeliest theory holds that one of the 112 crewmen aboard the Bravo dropped a tool down the well and it broke a safety valve below. So when the so-called Christmas tree of topside valves was removed for a routine inspection, pressure from the oil below blew out a temporary seal of clay and chemcials before the protector could be completely put in place.

There are many questions in Stavanger, headquartes for Norway's North Sea oil industry, over the lack of adequate safety equipment for the rigs. Every North Sea operator here is said to be short of the fire-fighting and other emergency ships needed.

Just three weeks ago, Paul (Red) Adair, boss of the firm whose crew is trying to avert further disaster, warned that a fearsome accident in the North Sea was inevitable.

"Sooner or later it catches you," he told Michael Buerck in a BBC interview. "It'll catch you with (your trousers) down. It really will."

"If there was a real blow-out," in the North Sea, he warned, "you don't have anything. You have a few little pistols - things that will squirt water."