ConocoPhillips' massive Willow project would emit 284 million metric tons of carbon dioxide over its 30-year lifetime.

Set against the austere peaks of the Western Brooks Range, the lake, looked like it was boiling. Its waters hissed, bubbled and popped as a powerful greenhouse gas escaped from the lake bed.

The release was first detected last month at one of the company’s North Slope drill sites. A report from the Alaska Oil and Gas Conservation Commission, dated Friday, listed the cause of the release as under evaluation and said that future plans included a continuation of “source remediation operations.”

The leak was detected early Friday at the drill site CD1, 8 miles north of the village of Nuiqsut. “There are no reports of injury or environmental impact to the tundra or wildlife,” the company’s statement said. “Air quality continues to be monitored and no natural gas has been detected outside of the CD1 pad.” The gas leak happened below gravel, and its cause and scale are under investigation, Conoco said. The company said it is using natural gas detection monitors at the CD1 pad, and conducting infrared surveys from the air.