Marathon Petroleum Corp (MPC.N) signaled on Tuesday that a sustained rally in natural gas prices could take a toll on earnings, sending the largest U.S. refiner’s shares down 4%. The warning comes after U.S. natural gas prices soared more than 60% in the third quarter — translating into higher costs since natgas is used to power refining operations — as sky-rocketing global rates keep demand for U.S. liquefied natural gas exports elevated. “For every $1 change in natural gas prices, we anticipate there is an approximate $360 million impact to annual EBITDA to our R&M (Refining and Marketing) segment,” Chief Financial Officer Maryann Mannen said. “Based on current prices, we estimate that in the fourth quarter, higher natural gas prices have the potential to impact our business by an incremental $0.30 per barrel,” Mannen added. Marathon said there was still some uncertainty around supply-demand dynamics […]