Alaska oilfield gas leak estimated at 7.2 million cubic feet

The company said it was placing cement to isolate the source of the gas.

ANCHORAGE — More than 7.2 million cubic feet of natural gas escaped in a leak at a key Arctic Alaska oilfield, 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.

[ConocoPhillips says Alaska leak is in a ‘shallow gas zone’]

Overall daily Alpine production fell to a low of 36,851 barrels on March 13 from 51,700 on March 1 before the discovery, the state’s revenue department said, though latest figures show output has since recovered to more than 50,000 barrels a day.

As site remediation work continues, Conoco said it was placing cement in multiple steps to isolate the shallow geologic formation identified as the source of the gas. Then it will plug the source, the company said on its incident website.

Last week it also received a permit for seismic surveys of the affected area, a drill site called CD1, the oldest in the Alpine field on the western North Slope.

ConocoPhillips did not respond to a request for comment.

Discovery of the leak led to the temporary evacuation of about 300 of the roughly 400 workers at the field.

There has been no detectable gas outside the structures enclosing the wells, though “fluctuating” low levels of gas have been reported inside the wellhouses, the regulatory agency said.