Exxon Mobil Corp. ’s Canadian subsidiary on Tuesday said it has resumed production at one of its largest oil sands mines “to pre-shutdown levels” after it halted operations in November due to a mechanical problem. Imperial Oil Ltd. suspended production three weeks ago after detecting a vibration issue in the mine’s core ore-crushing machinery used to extract heavy oil. That forced it to forgo output, which had averaged 92,000 barrels of crude a day in the third quarter excluding a 14-day maintenance window. “Repairs to the crusher unit have been completed,” and the company is still looking into the cause of the equipment malfunction, Imperial spokesman Pius Rolheiser said. The Kearl plant cost 13 billion Canadian dollars ($11.4 billion) and started production in April 2013 after a series of delays and cost overruns. Construction of an C$8.9 billion expansion to produce an additional 110,000 barrels a day […]