There is no shortage of natural gas in the United States.

A consensus of studies by federal and private groups is that more than 40 years of natural gas resources are available given current rates of production, current technology and current price control by the Federal Power Commission.

New technology and an end to interstate price controls might provide even more natural gas and the nation also can anticipate substantial quantities of synthetic gas in future years - particularly through conversion of coal to gas.

"The gas industry has reserves, proved and potential, to carry it well into the 21st century," according to Washington Gas Light Co. Chairman Paul E. Reichardt, whose distributing firm supplies natural gas throughout metropolitan Washington and other areas of Virginia, West Virginia and Maryland.

What the nation faces today, he said, "is a shortage of readily available supply."

Although some energy experts would quarrel with Reichardt's optimistic forecast about future natural gas resources , there is no question that adequate supplies exist today.

However, nothing can be done by Congress in the next few days or weeks to convert those supplies into natural gas readily available for shipment in the nation's 200,000-mile system of interstate pipelines.

And next winter could be a carbon copy, if the weather is just as cold. Even if all controls on the price of newly discovered natural gas are lifted this year, as proposed for many years by industry, the time involved in searching for new supplies will delay appreciably increases in available gas for at least a year, according to government and industry estimates.

In addition, most newly discovered natural gas in recent years has been channeled to markets within the state of discovery, where it has been sold at prices much higher than the federally regulated interstate market.

At best, emergency legislation proposed by President Carter will permit the use of some higher-priced intrastate gas to augment supplies in hard-pressed regions over the next few months, as well as reallocation of gas from some regions where supplies are relatively plentiful to other parts of the country.

If there is a consensus about actual resources and an inability to increase dramatically the available natural gas for the next year or so, there is no such agreement on why supplies currently are inadequate.

In the simplest terms, the gas industry says it is not profitable enough to conduct extensive drilling for gas aimed at the interstate market when prices in the intrastate markets are much higher.

Critics have stated that the gas producers deliberately have reduced exploration and kept their discovered natural gas out of the interstate market for the very purpose of forcing the government to change its pricing policies and to create greater profits if and when price controls are ended.

Under a controversial decision by the Federal Power Commission last year, the price ceiling on newly discovered natural gas was tripled to $1.42 a thousand cubic feet. Despite a challenge by consumer and labor organizations filed with the U.S. Court of Appeals here, the higher price now is in effect under bond - which means that refunds must be made if the rates are found to be illegal.

At the same time, natural gas is being sold today in intrastate markets at $2.25 to $2.50 per thousand cubic feet. The price differential has led to a reversal in the percentage of newly discovered gas going to intrastate markets over the past decade - from 68 per cent in 1966 to 13 per cent in 1975.

In planning for the current winter, many gas distribution firms expected to buy some of the higher-priced intrastate gas on an "emergency" basis, with special permits from the FPC. And even though the FPC has been liberal in granting such permits distributing firms are finding that extra gas is hard to buy at any price.

Producers in the key gas states - Texas, Louisiana and Oklahoma - say they don't have enough gas to meet contractual obligations within their own states because of the cold weather.

"The producers are withholdings gas from the market. There is absolutely no question about it," James C. Cotham, executive vice president of Nashville Gas Co., said last week.

But Reichardt, the Washington Gas chairman, said, "There is no hard evidence any gas is being withheld." It would be "criminal" if any producers are engaged in such an effort, he added.

Reichardt said that in instances where producers have been accused of withholding already discovered natural gas from the nation's marketplace, independent studies have found "good reasons" why the gas is not flowing.

A recent example was a charge presented to the FPC, alleging that Shell Oil Co. closed off wells with more than 2 trillion cubic feet of gas in 1974. The company provided evidence to the commission that showed the 2 trillion cubic feet figure to be accurate - but also that 31 per cent of that amount was awaiting new production plants, that 25 per cent was in reservoirs that couldn't be tapped until deeper supplies were first depleted, that 19 per cent was in newly discovered fields not drilled sufficiently for commercial sales and that 25 per cent was awaiting pipeline construction or final sales agreements.

According to the Federal Energy Administration, about 30 per cent of all energy in the United States comes from natural gas and 95 per cent of these gas supplies comes from this country, a percentage expected to decrease in the next decade with imports of liquefied gas from abroad. Gas heats 40 million residences and 3.4 million commercial buildings and is used in 193,000 factories - many of which must have gas for production.

The reason why these homes and factories face a shortage today (aggravated by the weather) is a reduction in drilling for new gas over the last decade. John D. Moody, president of the American Association of Petroleum Geologists, said exploratory drilling for new oil and natural gas fields declined from a high of 8,742 wells in 1956 to a low of 4,463 in 1971.

Large oil companies, who also are major producers of gas, ofter discovered gas while searching for oil. Since the oil firms have switched their search for new petroleum to other regions of the world, they are not finding natural gas as an adjunct and do not find it profitable enough to search only for gas, industry officials said.