By Yereth Rosen ANCHORAGE, Alaska (Reuters) – More than 7.2 million cubic feet of natural gas escaped in a leak at a key Alaska oil field, forcing workers to evacuate and cutting production last month, operator ConocoPhillips and a state regulatory agency said. ConocoPhillips is working to seal off the leak at its Alpine field, the Alaska Oil and Gas Conservation Commission said in a report, as it determined the gas volume lost in the leak discovered a month ago that brought a cut in oil output. Overall daily Alpine production fell to a low of 36,851 barrels on March 13 from 51,700 on March 1 …