Carbon dioxide injected into the ground to push out stranded oil bubbled into a stream within a central Wyoming oil field this summer and may have been responsible for killing six ducks and polluting the stream, state regulators say.
The Wyoming Department of Environmental Quality ordered Anadarko Petroleum, the operator in the field, to identify and control a carbon dioxide leak into Castle Creek, according to an agency notice of violation and order posted in August.
The agency also ordered the company to monitor the acidity of the stream until three consecutive tests indicated normal levels.
The agency first investigated the area in July, after Anadarko reported finding six dead ducks in the creek. While visiting the site later, officials discovered carbon dioxide gas bubbling into the water.
Company officials said the gas may have come from a carbon dioxide injection well nearby, according to the violation notice.
Anadarko operates the Salt Creek Field near Midwest, where the company rejuvenated the field’s sagging oil production by injecting carbon dioxide. The gas is injected into formations in order to free oil not brought to the surface using other techniques.
A follow-up water quality test showed the acidity level of the creek was below standards. Changes in water’s pH level can kill fish and other organisms, according to the agency.
The U.S. Fish and Wildlife Service collected the ducks for testing. Results of an investigation into the ducks’ cause of death were not available Thursday.
Anadarko has yet to determine where the leaked gas came from, company spokesman Dennis Ellis said Thursday.
A call to the Wyoming Department of Environmental Quality was not returned.
Ellis said Anadarko continues to monitor the area “without incident.”
“We will continue to work with [the Wyoming DEQ] until the cause is determined and any issues are resolved,” he said.