The invisible winners in President Carter's energy message may be the nation's oil companies.

In a series of technical decisions that have gone largely unnoticed in this week of presidential television appearances, the oil industry has won from the administration what one senior industry official described as "a lot of pluses."

These pluses would add up to hundreds of millions of dollars in additional revenues for the industry by 1980, mostly in the form of subtle price increases that would occur from relaxations of oil price controls.

There would be no federal tax rebates to compensate the paying public for those increases, which would show up in higher prices for gasoline and all other products made from oil.

The oil companies and industry trade associations such as the American Petroleum Institute have had an intense lobbying effort under way. It began before Carter's inauguration, and reached saturation level in recent weeks. One aide to presidential energy adviser James R. Schlesinger said, "We've been under carpet bombing by lobbyists of every stripe."

The lobbying continued even last weekend, as final details of the energy plan were being wrapped up. One decision of tremendous potential importance to the industry had to do with a definition - the substitution of the words "two and a half miles" for "five miles" in one part of the President's proposals. The President apparently did not finally decide to make this change sought by the industry until sometime Monday.

Under federal price controls, there are two basic categories of oil produced in the United States - old oil and new oil. New oil is essentially oil from wells drilled after 1972.

The price of old crude oil is frozen at $5.25 a barrel. New crude oil can be sold for as much as $11.28 per barrel.

What the Carter plan does for the industry - perhaps the most important thing - is quietly create a third category which would not be subject to price controls at all, and could rise to the so-called "world" or uncontrolled price of more than $13 a barrel.

A second important plus for the industry is a provision under which the price of new oil would automatically rise each year with inflation, and the annual price increases would not be subject to congressional veto, as they are currently.

A third technical change involves the "decontrol" of gasoline prices, which are currently tied by law to the controlled price of crude oil. Experts estimate this gasoline decontrol could result in a 3-cent-a-gallon jump in gasoline prices when it takes effect, which under the President's plan it would do this coming fall.

Another aspect of the President's proposals was important to the industry and the subject of lobbying, even though it did not involve immediate or measurable advantage. This involved so-called horizontal divestiture - proposals to make oil companies give up their extensive interests in other fuels such as coal and uranium.

Carter indicated during last year's campaign that he favored this concept, but in his message to Congress Wednesday night he said he had decided to drop it for now, and instead have the oil companies give a greater public accounting of their holdings and activities.

A senior administration official yesterday defended the various changes in the oil pricing system as essential to stimulate increased production.

The changes "shift the incentive to go find new oil. It makes it more profitable for the companies," this official said.

The President's plan describes two kinds of oil that would not be subject to present price controls. One is oil produced from offshore oil tracts on which drilling rights are leased from the federal government after April 20 of this year - last Wednesday, the day Carter spelled out his plan to Congress. The other is oil from any well drilled from now on that is at least 2 1/2 miles from the 5 miles that had earlier been contemplated.

"Somebody tapped somebody on the shoulder," one senior industry official said, explaining how the administration position was turned around.

Another industry source said that "input sent by the National Petroleum Council" was the major factor. The National Petroleum Council is an industry-government advisory body headed by Kenneth E. BeLieu. BeLieu, according to NPC staff members has known Schlesinger well for years.

According to documents obtained by The Washington Post, administration experts believe that by 1980 the industry could be producing an additional 1.1 million barrels of oil a day from uncontrolled wells.

This production alone could result in $1 billion in added revenues for the producers, according to the administration estimates.

Despite Carter's eleventh-hour decision to walk back the limits from 5 miles to 2 1/2 miles, oilmen are still chafing at the impact the definition will have on new production.

During an intense series of meetings over the past week the Independent Petroleum Association of America argued that any kind of a regulatory limit would depress production. A.V. Jones, IPAA President, said that he stressed in sessions with the Carter energy planners that as recently as 1974, 90 per cent of new oil discoveries were within 2 miles of producing wells.

Jones and other industry leaders have already launched a lobbying effort with key members of Congress to strike the distance provision altogether, knocking out controls on all new wells.