LONDON—U.K. independent oil and gas explorer Heritage Oil PLC Tuesday became the first new foreign firm to strike a deal to enter the Libyan oil sector following the war through its acquisition of a Benghazi-based oil services company.

Although incumbent majors like Total SA and ENI SpA have resumed some production in Libya, new oil companies are salivating at the prospect of joining them in exploring the country with the largest oil reserves in Africa following the fall of Col. Moammar Gadhafi in August.

Heritage...