Lundin Petroleum AB suffered its biggest ever quarterly loss as the collapse in oil prices forced the Swedish explorer to book impairment charges. The loss widened to $493 million in the fourth quarter from $436 million a year earlier, the Stockholm-based company said in a report on Wednesday. The company booked an impairment charge of $296 million and a foreign exchange loss of $129 million. The shortfall for all of 2015 was $862 million, its biggest annual loss since the company was formed and listed in 2001, according to data compiled by Bloomberg.