With the ink hardly dry on his hard-fought bill giving natural gas producers higher prices for their product, President Carter is facing an awkward prospect; a natural gas glut.

The glut may be brief - that depends to a certain extent on how the new law works out in practice - but a wide range of experts now believe it could be lengthy.

"One of the prospects we seriously face is a natural gas glut," said Jay Kennedy, head of ELCON, a Washington coalition of major industrial energy users.

At the Energy Department, one of the administration's top policymakers said, "We have a gas glut now that could run on for three or four years."

Oil industry executives bristle at the term "glut," particularly since during the debate over the gas bill they had maintained that without higher prices the nation would face a long-term shortage.

"I prefer to call it a bubble," said Bud Lawrence, president of the American Gas Association (AGA). And in Houston, one of the nation's top natural gas analysts is calling it "an over-deliverability situation."

How long the glut lasts depend on the effects of the complicated natural gas measure Carter signs into law and whether the tantalizing prospects of major gas imports from Mexico and Canada come on stream.

By any name, however, there has been a dramatic change in the nation's gas outlook. Up until a few months ago most gas companies were not allowing new industrial hookups, and as recently as two years ago papers such as The New York Times and The Washington Post carried headlines warning "Gas Shortage A Fundamental Long-Term Economic Threat to U.S."

This idzzying shift from shortage to glut has left consumers, to say nothing of some members of Congress who just finished the often acrimonious legislative battle, confused.

"There are some real contradictions here that have to be worked out," said ELCON's Kennedy when asked about the supply outlook.

It is, however, cheering news for the oil industry.

"This is going to put us back in the marketing posture again," said AGA's Lawrence. A former Exxon executive, Lawrence added that gas pipeline companies and producers will have to convince industrial gas users to reverse their trend of shifting from gas to oil and coal.

More important for the industry, the glut situation will enbale companies such as Exxon, the nation's leading gas producer, to make the most of the higher prices available under the Carter-backed gas bill.

Another little-known but critical factor is that, on an energy-equivalent basts, the industry produces more gas each year than it does oil. This also will add to profits.

This, is short, is how the glut came about and how it could continue:

Because of disparities in regulations, gas prices in unregulated markets within producing states such as Texas had risen to over $2 per 1,000 cubic feet, sometimes a dollar or more higher than in regulated interstate markets. Some producers held back gas, hoping the government would raise prices in the interstate market. In the meantime, many industrial users switched to oil and coal because of high gas prices and insecurity over supplies.

Higher gas prices under the Carter bill will bring much of those "shut-in" supplies - up to 0.8 trillion cubic feet a year or more - onto the market now, according to Energy Secretary James R. Schlesinger.

Since the quadrupling of oil prices in 1973, oilmen have drilled more wells and have found more gas in the process, especially in new exploration areas such as the so-called Overthrust Belt in Wyoming. This new production is just beginning to find its way to the market.

Canada and Mexico have made major natural gas finds in recent years and both are eyeing the possibility of sharply increasing gas exports to the United States. Canada now provides 5 percent of U.S. gas consumption, and Mexico much less. Some oil experts, however, say that new discoveries in Alberta, Canada, and in Mexico's Reforma fields could raise that amount to as much as 10 percent if political hurdles can be cleared.

So far, applications for increased Canadian exports are awaiting approval by Ottawa's National Energy Board, and a major Mexican gas deal - possibly the first of several - is being held up because Schlesinger has balked at pegging gas prices to heating oil. The price, starting at about $2.60 per 1,000 cubic feet, would be the highest paid in the world for conventional natural gas flowing across borders.

That in turn will be a function of price. The more prices rise, the more industries will turn to alternative fuels and the longer the surplus will last.

The major question about how long the long-supply situation lasts hinges in large measure on the rate at which industrial users shift on the and off gas.

Carl Bagge, head of the National Coal Association, says that the so-called incremental pricing provisions in the Carter gas bill that could make industrial users pay higher gas prices will force some industrial customers to shift to coal or oil.

Key to the interpretation of the bill's pricing provisions are the rate decisions that state utility commissions and the Federal Energy Regulatory Commission make regarding industrial gas prices.

AGA's Lawrence says this could be a problem, though "we think the legislation is sufficiently flexible where none of our industrial gas will be priced out of competition with foreign oil."

Privately, other oil executives say that, if necessary, the industry will press for "cleanup" legislation to soften the incremental pricing provisions that could raise industrial gas prices.

Elsewhere, industrial users say that last summer Schlesinger gave them private assurances in exchange for support for the controversial gas measure that industrial gas prices would remain attractive.

Nevertheless some oilmen such as John Beckley vice president of New England Petroleum Co., say that "the big utilities and industrial users will continue to switch to double fuel-burning capacity in place of just gas."

The result is that if industrial users don't use more gas, as energy planners say, to "black out" oil, oil imports will rise and gas supplies will be more abundant - or more glut.

One thing that is certain about the suddenly abundant gas supply outlook is that it has taken the gleam off some new high-cost energy projects.

FERC Commissioner Don Smith said, "it may slow down some coal gasificiation projects, as well as some liquefied natural gas projects." Coal gasification is a high-cost method to convert coal to pipeline quality gas. LNG costs, which require expensive shipping, are about twice the highest cost of conventional gas now sold in U.S. markets.

One of the biggest questions could face the proposed 4,800-mile, $14 billion Alaska gas pipeline.

"I think the Alaskan gas pipeline could be in jeopardy, at least for a while," said one top Energy Department official adding that given the choice of gas from Canada or Mexico at less than $3 per 1,000 cubic feet, $4.50 gas from Alaska looks less attractive.

Arlon Tussing, former Senate Energy Commission chief economist, goes further, saying, "Alaskan gas will probably cost more than oil and can only come into the market where Mexican and Canadian gas are restricted."

John McMillian, head of the Northwest Pipeline consortium that is pressing for the Alaskan line, conceeds that "Alaskan gas will be more expensive . . . but it is domestic gas and we will have less outflow of dollars for foreign sources of energy.