Eni said it will run initial tests of 3 million cubic meters worth of gas a day during the preliminary phase, but could not immediately say how long that would be.
Greenstream transported 9 billion cubic meters worth of gas a year to Italy before fighting in Libya forced Eni to shut down the pipeline in February. That's about 12 percent of Italy's annual needs.
Eni called the restart of Greenstream "a milestone." Eni operates Greenstream with the Libya's state-rung National Oil Corporation.
The gas is being produced by the Wafa field, around 300 miles southeast of Tripoli. Eni said the field continued to produce gas during the conflict to make electricity for local consumption.
Eni and Noc are aiming to restart gas production in November from the offshore platform of Sabratah, located 110 kilometers off the Libyan coast, along with the associated treatment and processing facilities at the Mellitah Complex.
On the oil side, Eni has reached full production at the Abu-Attifel oil field with 70,000 barrels a day. Production restarted in late September at around 40,00 barrels a day.
Eni has been active in Libya, a former Italian colony, since 1959 and is the largest foreign player there in terms of hydrocarbon production. Before full-scale civil war erupted in February, Eni was producing 273,000 barrels of oil equivalent per day in Libya.