The collapse of the floating hotel rig that killed 123 Norwegian and British oil workers last week dramatized the dangers of drilling for oil in the hostile environment of the stormy North Sea. But it also reminded Britain and Norway of just how dependent on this risky business they have become.

After a decade of drilling and heavy startup costs, large amounts of oil money are flowing into the two countries' treasuries for the first time, Britain badly need this money to help rescue its deterioriating economy, while Norway has been counting on it to help maintain a high standard of living and full employment even though its traditional industries are shrinking.

To maintain the flow of money, still more oil rigs must be added to the 100 already scattered across the North Sea between the two countries and exploration must move into even deeper and stormier waters, despite what happened to the Alexander Kielland, the rig that capsized.

This realization is proving painful in Norway, where last week's disaster just inside the Norwegian sector of the North Sea oil field prompted an investigation into its cause and renewed debate about whether oil exploration should be allowed to move further north along the vast section of the Norwegian coast above the 62nd Parallel.

This is a symbolic threshold for fisherman, farmers and environmentalists who fear that expanding off-shore oil exploration will damage Norway's beautiful coastline and bountiful fishing grounds.

Test drillng north of the 62nd Parallel was postponed in 1977 after 150,000 barrels of oil spilled into Norweigian waters from a spectacular well blowout in the same Phillips Petroleum Ekofisk field where last week's accident occurred.

The Norweigian parliament decided two weeks ago, after heated debate, to allow test drilling in northern waters to finally go ahead next month. But it may now be delayed again, officials close to Prime Minister Odyar Nordli have suggested, to avoid a political confrontation that could endanger the rest of Norway's North Sea oil development.

In Britain, officials are cooperating closely with the Norwegian investigation of the Alexander Kielland's collapse and carrying out emergency inspections of "everything that floats" in the even busier British sector of the North Sea. But there is a more general acceptance here of the hazards of the North Sea oil exploration, which are mostly faced by willing off-shore oil workers who are exceptionally well-paid by British standards.

"As someone said to me, if there had been a similar accident at a nuclear power plant, our whole nuclear program might have been shut down," said Energy Secretary David Howell. "But everyone realizes that the North Sea is just a hell of a dangerous place. I doubt that last week's accident will have a major impact on our North Sea program."

At a time when the soaring price of imported oil has thrown into turmoil the economies of so many other countries, Britain and Norway this year will be the only Western industralized nations producing more oil than they consume.

Norway already produces five times as much as it needs and sells the rest, most of it to other European countries and the United States.Britain becomes self-sufficient in terms of volume in a few months, but already half of its high quality North Sea oil is exported for significantly more money than it costs to import lower grades of oil to make up the difference here.

The doubling and redoubling of oil prices during the 1970s has only increased the oil income of the British and Norwegian governments.

Last year's price jumps alone multiplied their take from oil taxes and royalities by two or three times the most optimistic forecasts made just a few months earlier. By the middle of the 1980s, Britain and Norway will be awash in oil money that could not have arrived at a better time.

In Britain, the sharp rise in the government's North Sea oil revenue from about $2 billion last year to well over $30 billion by 1984 is expected to underwrite Prime Minister Margaret Thatcher's monetarist plan for turning around the deterioriating British economy.

Just in time for the 1980 parliamentary election, she expects to be able to make big cuts in income taxes, shrink the government debt and reduce record-high interest rates, perhaps wiping out the memory of the intervening years of austerity. Members of her Cabinet also hope that oil money will replace reduced government subsidies as a stimulus for sagging British industry.

In smaller Norway, oil income already is turning budget and balance of payment deficits into surpluses. It also could easily pay off the big, once worrisome debt the government plunged into by borrowing against future oil revenues to prop up failing industries and maintain Norway's standard of living during the 1970s.

The rapid growth of the North Sea oil industry, which soon will account for a fourth of Norway's gross national product and half of the value of its exports, comes just in time to take up the slack of shrinking shipbuilding fishing, forestry and agriculture.

Norwegian oil industry employment has risen from just 35 people when exploration began in the late 1960s to nearly 40,000 today, in a country of only $4 million. Oil money is being used to develop new technology and jobs to replace dying industries.

"God must be a Norwegian," one economist decided after tracing how late industrialization with hydroelectric power and now oil wealth have lifted Norway during the 20th century from one of Europes's poorest nations to one of its richest.

What God has given the Norwegians, they are determined to make the most of -- with policies to maximize the long-run national gain from North Sea oil that resemble those of some OPEC countries, and which have been copied by Britain more than its present free market government likes to admit.

Ironically, Norwegian officials speak of their fear that their nation might become "another Kuwait," with its burgeoning oil industry destroying the rest of the economy and a traditional rural culture that has been better preserved, along with about 40 surviving local dialects, in the isolated valleys and fjords of mountainous Norway than those of the other Scandinavian countries.

From the beginning, Norway decided to limit oil production to what it could handle economically, environmentally and socially. Environmental and safety requirements it imposed on oil companies have kept production even lower and helped pace the development of future North Sea oil fields.

As a result, although production began in the Norwegian sector of the North Sea four years earlier than in the neighboring British sector, Norway's present annual production of about a million barrels a day is little more than half Britain's. While British officials worry about self-sufficiency could last only through the 1980s if they do not impose production controls, Norway's peak production should last at least until the end of the century.

"While the British went flat out, we were more cautious," said an official of Norway's government-owned oil company Statoil. "Norway is stretching out its oil reserves and phasing in one field after another."

Britain is only now working out an oil depletion policy, which Energy Secretary David Howell will soon discuss with the oil companies "to manage our resources over time so that our oil production doesn't just zoom way up and then right down again."

After allowing multinational oil companies to develop its first vast North Sea field, Ekofisk, where last week's accident occurred, Norway has been developing later fields with Statoil and other Norwegian companies. Statoil is now assured of between 50 and 80 percent ownership of new oil fields in the Norwegian sector of the North Sea and it intends to expand its refining capacity and start selling oil products outside Norway.

The multinationals must content themselves with smaller shares of the action and the role of "technical assistant" to Norwegian firms.To get that much, which still promises to be lucrative, they must employ as many as Norwegians as possible and invest in "industrial cooperation" projects to provide Norway with new technology to replace its older, dying industries.

Both Britain and Norway also have recently increased their oil taxes to confiscate between 70 and 80 percent of the profits North Sea oil companies make from oil prices.

While a left-of-center Labor government angered oil companies by proposing last month in Norway, it was Thatcher's Conservatives who increased the oil tax here at the same time.