Libya has lost over 145 million U.S. dollars since the closure of a major oil field a month ago, the state-owned National Oil Corporation (NOC) said on Sunday.    "Al-Fil oil field, which produces more than 70,000 barrels of oil per day, is still closed as production remains stopped for the second month," a senior official of the corporation said.    Al-Fil was shut after the oil installation guards withdrew from the oil field in protest of their unpaid salaries, and the corporation then declared force majeure in it.    The official said on condition of anonymity that no solution was reached for now.    The "financial demands" of the guards and "the provision of the means to facilitate their work" are the responsibility of the government, not the corporation, the official added.    Located some 900 km south of capital Tripoli, the oil field is one of the most important fields of the Italian energy company Eni, which operates the field together with the NOC.    Libya, with Africa's largest oil reserves, used to produce about 1.6 million barrels per day before the 2011 armed uprising that toppled former leader Muammar Gaddafi.    The country's daily production of crude oil has returned to over 1 million barrels a day since the end of 2017, after production operations of all southern and eastern oil fields were resumed.    However, sudden closures of oil fields due to protests have caused Libya's oil production to fluctuate.