Militants sympathetic to al-Qaida in the Islamic Maghreb stormed the In Amenas natural gas facility in eastern Algeria in January. Foreign workers with BP and Norwegian energy company Statoil were among the dead in the attack.
Oil services provider Petrofac said it temporarily pulled its staff out of the country in response to the attack.
"We expect to recommence full site operations during the second half of 2013," the company said in a statement.
Algeria has the 10th largest natural gas deposits in the world and is the third-largest supplier to Europe. Its exports have been in decline, however, because of lagging foreign investments.
A country report updated in May by the U.S. Energy Department's Energy Information Administration reports Algerian natural gas production has been in decline since 2005 because of field maturation. There have been several new projects discussed but few have gone on stream.
Petrofac said it expects "modest" growth in its economic performance for 2013.