Canada, which clamped a tight lid on foreign energy sales following the 1974 Arab oil embargo, is now moving toward a major boost in its natural gas exports.

The abrupt turnaround reflects a growing sense in Ottawa that predictions of a dire energy shortage in Canada were off the bank.

Potentially massive gas reserves have been discovered in Alberta, the principal oil-producing province. The discoveries are so large that some oilmen say they could more than triple Canada's gas reserves - enough to allow for the increased exports and still meet domestic needs.

Oil executives on both sides of the border are confidently predicting that gas export applications now before Canada's National Energy Board will be approved.

"I think we can see as much as 1 billion cubic feet a day in increased exports by next spring, and after that steadily rising exports," says James Grey, vice president of Canadian Hunter Ltd., an Alberta oil company.

The NEB has not approved a major new gas, export contract since 1970.

In Washington a senior Energy Department official sums up the outlook by saying: "Let's face it, Canada has a lot of gas and is under a lot of pressure to export it."

Not the least of these pressures is the saggling Canadian dollar, now trading at its lowest lovel in 45 years. Increased gas exports, oilmen argue, could add $8 billion to $10 billion to Canada's trade accounts.

One irony is that these new supplies from Canada, if they are delivered, will be coming on stream when the U.S. domestic gas market is glutted.

Today Canada supplies about 5 percent of U.S. gas consumption. Currently Canadian oil companies have government-approved contracts to ship 11 trillion cubic feet of gas here by the early 1990s.

Oilmen such as David Q. Martin, Amoco Canada's vice president for exploration, say that Canada could export an additional 18 trillion cubic feet of gas in the years ahead.

U.S. gas consumption averages 20 trillion cubic feet a year.

Pressing for the Canadian exports on both sides of the border are the backers of the proposed 4,800-mile pipeline that would carry gas from the North Slope of Alaska to the lower 48 states.

"Canadian gas exported can pave the way for the pipeline," says John M-Millian, president of Northwest Pipeline Co.

Joined by Canadian exports on both sides of the border are the backers of the proposed 4,800-mile pipeline that would carry gas from the North Slope of Alaska to the lower 48 states.

"Canadian gas exports can pave the way for the pipeline," says John M-Millian, president of Northwest Pipeline Co.

Joined by Canadian oilman and entrepreneur S. Robert Blair, president of Alberta Gas Trunkline, McMillian is trying to put together a syndicate to finance the $14 billion project, starting with increased Canadian gas shipments.

The proposed Alaska gas pipeline will be an inverted "Y", heading southward across Canada's Northwest Territories and forking near Edmonton, Alberta, southeast and southwest toward the U.S. border.

"We are going to prebuild our eastern and western legs starting in 1979 and will have our first gas delieveries in the early 1980s," says McMillian.

So far the Canadian government, largely for internal political reasons, has been publicly cautions about increasing exports. Energy Minister Alastair Gillespie said in October that prospects for approval were still not clear.

Some Canadian officials suggest in private that oilmen operating in what is sometimes referred to in Canada as "the Sheikdom of Alberta" may have inflated their recent discoveries to win NEB approval for exports to the United States.

Canadian oil companies most of which are dominated by American firms such as Texaco, Exxon and Amoco, also stand to take in more from gas exports (about $2.16 per thousand cubic feet) than from domestic sales (about $1.70).

Canadian Hunter's Grey discounts this, saying. "It is going to be more and more politically acceptable to export our gas as we add to our reserves."

Canadian gas reserves are set at 65 trillion cubic feet, compared with about 200 trillion cubic feet for the United States.

For years geologists have been saying that Canada has the same potential for oil and natural gas that the United does, but that only one tenth as many wells have been drilled.

Because of higher prices available to Canadian oilmen since 1974, drilling has increased.

Amoco Canada's exploration of chief says they find gas in one out every two wells drilled, compared with about one out of five here.

The largest discoveries in Canada are the so-called "Deep Basin" field in Alberta and British Columbia - actually a cluster of smaller adjoining fields. Canadian Hunter's President John Masters says the Deep Basin alone could contain 50 trillion cubic feet of gas. This is twice the estimated gas reserves on Alaska's North Slope.

"That gas is going to find its way to the states." say Grey. "From an American standpoint, production from Canada has to be viewed with more security than imports from any other country in the world."

Reflecting on the shift in Ottawa's energy outlook, one Canadian official says. "It's awfully hard to react to such an abrupt turnabout to what the industry has been telling us for years. Just a few years ago these same companies were saying they needed higher prices to meet domestic Canadian needs."