CUSCO, Peru (Reuters) - Peru's state energy firm Petroperu is considering using bank loans, debt sales or pension funds to raise the estimated $1.7 billion needed to double output at its main refinery, the company's president said on Saturday. Petroperu chief Humberto Campodonico said the design of the financing mechanism is being evaluated by French bank Societe Generale, but that it would be made up of 80 percent debt and 20 percent from company resources. "Our estimate is that we'll need at least $1.7 billion," he said during a meeting of business leaders in the Andean city of Cusco. "For the financing, there could be bonds, contributions from pension funds, foreign banks, export credit agencies. There are a number of possibilities." The state energy company plans to double production at its Talara refinery in northern Peru to 90,000 barrels per day as part of a broader expansion, Campodonico said. Petroperu, which is involved in refining, retailing and storage, previously estimated the required investment at $1.3 billion but new units have been added to the expansion plan. The company, which competes with Spain's Repsol , stopped production and exploration work in the 1990s, but the expansion plan envisions a return to production. Campodonico said Petroperu wanted a 20 or 30 percent stake in a project to build a natural gas pipeline in the south of the country. "We're trying to reach an agreement before the end of the year," he said. "A bill will be presented (to Congress) that lays out the need to have the gas pipeline and for Petroperu to participate."