In the first public hearing on the natural gas leak at its Alpine field more than a year ago, officials with ConocoPhillips said an effort to pump freeze-prevention fluids into a disposal well increased pressure in the well and initiated the leak.
ConocoPhillips, the largest oil producer in Alaska, also identified other problems, including a delayed recognition that allowed the leak to continue uncontrolled for days, and the faulty expectation that a shallow underground zone did not contain significant amounts of gas.
The U.S. Environmental Protection Agency is also investigating the leak, said Erica Livingston, a wells chief engineer with ConocoPhillips in Alaska, at the meeting.
The company detected the gas leak at the CD1 drill site on March 4 last year, though the freeze-protection operation that initiated the leak began on Feb. 27, according to a timeline of events provided by ConocoPhillips for the meeting.
Over several days, 7.2 million cubic feet of natural gas was released into the atmosphere before ConocoPhillips directed the escaping gas to the Alpine gas processing facility where it was captured.
The leak caused the temporary removal of 300 personnel, alarmed residents in the nearby village of Nuiqsut, and halted oil production from the drill site. It also led to the investigation by the Alaska Oil and Gas Conservation Commission, the state agency that held Thursday’s public hearing and oversees oilfield operations in the state.
ConocoPhillips has provided many of the details it outlined in the meeting previously, including in a nine-page incident report provided by ConocoPhillips last year to the commission. In that report, the company said the leak occurred as part of an operation to pump 170 barrels of diesel fuel into the well. The diesel provides protection from freezing that can damage the well.
The freeze-protection effort caused a component of the well to fail, leading to the gas leak, ConocoPhillips officials said at the meeting.
The hearing was a chance for citizens and commissioners to learn more about the incident from ConocoPhillips in a public forum, Chair Brett Huber said at the start of the meeting.
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The leak was a “significant event” that offered a learning opportunity for ConocoPhillips, Livingston said at the meeting. She said no gas was detected beyond the CD1 drilling site, and no wildlife or people were harmed by the release.
ConocoPhillips officials provided new technical details in the meeting. They discussed measures the company took to bring the leak under control, as well as actions to prevent the problem in the future.
They said pressure increases in the well weren’t recognized and addressed from March 1 to March 3, which allowed more gas to escape.
The well used a design that has been used many times before without problems, officials said.
The well was not cemented in the area of the gas zone where the leak occurred, because the zone was not expected to contain gas. Cementing the well in that area, about a half mile underground, would have prevented the gas release, Livingston said.
Among other corrective measures, the company has increased monitoring of pressure at wells and developed a standard freeze-protection operation document laying out pressure limits and solutions when limits are exceeded.
Two members of the public spoke by phone at the hearing, including Rosemary Ahtuangaruak, the mayor of Nuiqsut.
She said the community of about 550 hopes to learn more about the leak in order to prevent future accidents, especially now that federal regulators have approved the large Willow oil project 35 miles west of the village. Ahtuangurauk had opposed Willow.
People worry about the impact that thawing permafrost, as a result of climate change, is having on oil field activities on Alaska North Slope, she said.
“This event gave our community members much concern,” she said. “We want to fully understand to prevent this from happening at the new development that will be nearby our community.”
Asked what role permafrost thawing due to global warming may have played in the incident, Rebecca Boys, a spokeswoman for ConocoPhillips, said “none due to climate change.”
The commission will prepare a final report that could include enforcement measures, Huber said, without describing what form those measures might take.
Huber said there’s no timeline for the report’s release. He declined to additional answer questions, saying he would do so after the report’s release.
The oil and gas agency had previously set the hearing for October. But two of three commissioners had left the agency at that time, leaving it without a quorum, Huber has said. Huber, one of the new commissioners, is a former senior policy adviser to Gov. Mike Dunleavy, who appointed him.
Huber said the public can deliver comments about the issue until 4:30 p.m. on Friday. They can be hand-delivered to the commission’s offices at 333 W. Seventh Ave. in Anchorage, or emailed to firstname.lastname@example.org, he said.