Active exploration started in 1953 after oil was discovered in neighboring Algeria. The first well was begun in 1956 in western Fezzan, and the first oil was struck in 1957. Esso (subsequently Exxon) made the first commercial strike in 1959, just as several firms were planning to give up exploration. The first oil flowed by pipeline from Esso's concession at Zaltan to its export facilities at Marsa al Burayqah in 1961. The rush was on, with other companies entering Libya and additional discoveries being made. . . . .
When early concessions to several large companies by Esso, which was the first to export Libyan crude in 1961, proved to be highly profitable, many independent oil companies from noncommunist countries set up similar operations in Libya. In 1969 about thrity-three companies held concessions. Concessionary terms were somewhat tightened during the 1970s, as the postrevolutionary government pursued a more active policy of nationalization. The vehicle for this policy was the revamped state NOC, which, as noted, was formed in 1970 from LIPETCO. In July 1970, NOC's jurisdiction was expanded by legislation that nationalized the foreign-owned Esso, Shell, and Ente Nazionale Idrocarbuno (ENI) marketing subsidiaries, and a small local company, Petro Libya, and transferred their operations to NOC. These operations included managing companies in the importing, distributing, and selling of refined petroleum products at subsidized prices in Libya. In 1971 the companies were merged into a single countrywide marketing enterprise called the Brega Company, which also marketed oil and gas abroad for the government.
The new government's nationalization campaign commenced in December 1971, when it nationalized the British Petroleum share of the British Petroleum-Bunker Hunt Sarir field in retaliation for the British government's failure to intervene to prevent Iran from taking possession of three small islands in the Persian Gulf belonging to the United Arab Emirates. It was not until late 1974 that a compensation agreement was reached between British Petroleum and the Libyan government over the settlement of these nationalized assets. In December 1972, Libya moved against British Petroleum's former partner Bunker Hunt and demanded a 50-percent participation in its operations. When Bunker Hunt refused, its assets were nationalized in June 1973 and turned over to one of NOC's subsidiaries, as had been done earlier with British Petroleum's assets.
In late 1972, a 50-percent participation had been agreed upon with the Italian joint company, ENI-AGIP, and in early 1973 talks began with the Occidental Petroleum Corporation and with the Oasis group. Occidental, accounting for about 15 percent of total production, was one of the major independent producers. In July 1973, it agreed to NOC's purchase of 51 percent of its assets. The Oasis group, another major producer, was one-third owned by the Continental Oil Company, one-third by Marathon Petroleum, and one- sixth each by Amerada Petroleum Company and Shell. The Oasis group agreed to Libyan 51-percent participation in August 1973. On September 1, 1973, Libya unilaterally announced that it was taking over 51 percent of the remaining oil companies, except for a few small operators.
. . . . More at
http://countrystudies.us/libya/60.htmCertain interests in the US who are now very influential in the UK and the US have historical claims to the oil fields.
I hope that those interests are prepared to pay for any military intervention costs the US might incur -- including the costs of veterans' benefits of all kinds that the US might incur as a result of a military intervention.