An article in yesterday's editions identified the Mobil Corp. as one of several U.S. firms that are conducting business in Libya. The New York-based corporation has not operated in Libya since 1982 and has no employes there, the company said yesterday. There is a local firm in Libya that has taken the name of Mobil.

Americans living and working in Libya said today they believe they have little to fear from the Libyans, but in some cases they are worried about reprisals against them by the U.S. government or against their families by Americans angry that they are working under the government of Muammar Qaddafi.

U.S. citizens working in Libya "are not hassled. On the contrary, they get special treatment," said one diplomat who knows several Americans working here. "Let's face it, [the Libyans] need them here: the oil industry, it's the Americans who still run it."

"I've never been hassled since I've been here," said a Texan oil company employe who asked that his name not be published. He expressed concern, however, that Washington might take action against the Americans who, in Washington's view, are working here illegally. He spoke before President Reagan's news conference.

Before December 1981, when Reagan issued an executive order for all Americans to leave the country, between 1,000 and 1,500 Americans were believed to be living here. [But administration officials said last week that their 1981 estimates had been far too low and that the number of Americans in Libya at that time may have been as high as 8,000.]

At present, the number of Americans here at any given time is unknown. But estimates by diplomats range from 600 to as many as 2,000. Only a handful have received the State Department waivers, for humanitarian or similar reasons, required by the U.S. government to work here.

The Libyans, to make things easier for American residents, no longer stamp their passports. Instead, Americans are given a slip of paper that they return on their departure so there will be no ready proof that they have ever been here.

[Reagan, in his news conference, said that Americans who violate his new orders to leave Libya will be subject to "appropriate penalties upon their return to the United States."]

Many of the Americans in Libya are rarely seen by Libyans, diplomats said, because they work and live in oil fields far out in the desert, where they are employed by companies such as Mobil Corp., Occidental Petroleum Corp. and Libya's own National Oil Co.

Those Americans in the field often work 30-day shifts followed by 10 days of leave, usually spent out of the country, these diplomats said. Those working in the cities live in comfortable seaside compounds with other white-collar employes from Egypt, India, Pakistan and Europe.

According to one authoritative source, not a single American employe here has been deported in recent years for any cause.

Today, before Reagan's news conference, reporters sought out Americans in front of Mobil's downtown office or in their tidy little company-supplied homes near the beach. These engineers, technicians and management specialists asked, first of all, that they not be quoted by name.

Even those eager to explain their position here were reluctant to be identified by company or job title lest they disturb the sensitivities of their employers -- including the Libyans -- or face prosecution when they return home.

"We don't know what the problems are going to be," said the Texan who has worked for oil companies from Venezuela to Brunei. "We don't know what the reprisals are going to be from the United States."

The Texan said that the idea that he may be helping support a government that his own government has labeled terrorist does not bother him. He made a distinction between the professionals he works with and the government and said he had nothing to do with the Libyan government.

But the life he described is one built on uncertainties and undertaken exclusively for money.

"I was unemployed in the United States for several months, so this is my survival," he said. "I'm 54 years old. I'm overqualified and overpaid, so I can't get a job."

A year ago he heard about an opening here from a friend in Europe and went for an interview with his prospective Libyan employers somewhere -- he wouldn't say where -- outside the United States.

"I took three resumes of other people along that don't have jobs in the United States," he said.

The Libyans prefer to hire Americans with at least 15 years' experience, he noted. In the United States men of his age often are thought too old to be hired.

But the sweetest incentive to work in Libya is the salary, which the Texan said is about twice what he would make at home "and that's tax free, too." Unlike other foreign workers here, who can send only 50 percent or less of their income home in hard currency, the Texan said he got a contract allowing him to send out 90 percent of his earnings.

He arrived in early December along with several other Americans in positions similar to his and said he had the impression there has been a new influx over the last six or seven months. "I call this hazardous duty," he said, because "that's how you're paid."

But the Texan admitted that "this is not a country for everybody. You have a language problem. You also have a food problem.

"You have to go hunting, I call it, for food," he said. On Friday, his one day off, the hunt takes him and his buddies to farmers selling chickens and vegetables along the roads outside Tripoli. In the capital, the shelves of supermarkets are virtually bare.

No liquor is allowed in this Moslem country, although some long-time residents brew their own beer.

But for all the sense of security he talked about, he explained the bare walls of his little two-bedroom house as a measure taken against disaster.

"You don't bring anything sentimental," he said. Although a few Americans have come with their families, he left his behind. "If I had to leave in 24 hours I could take two suits and a flight bag and be out." But for the moment, the military alert, the call-up of reserves and Qaddafi's threats to launch suicide squads against the United States have not touched the Americans here.

No unusual troop movements have been seen in the streets, according to diplomats. Despite reports of blackouts yesterday, the dimming of public lighting in a few parts of the capital was more likely the result of short circuits brought on by evening rains, foreign observers said today.

Tripoli is quiet and the oil company compounds are quieter. The Belgian Embassy, which handles American interests, is telling inquiring Americans to stay put. But, according to one embassy employe, only one American has called.

"I think it's all in Reagan's brain," an American here with Mobil said of the image Libya has in the United States at the moment.