Details emerge on potential cause of gas leak on Alaska’s North Slope (2024)

Details emerge on potential cause of gas leak on Alaska’s North Slope (1)

New details emerged this week about what may have caused a natural gas leak on Alaska’s North Slope that began nearly a month ago.

ConocoPhillips said Thursday although gas is still percolating up from the ground in small amounts, the leak had been stopped at the source.

The company hasn’t confirmed a specific cause, but ConocoPhillips said it drilled through an area it didn’t expect to contain significant amounts of gas. Because it didn’t expect much gas to be in that area, it also did not take a step that an expert says should have prevented gas from escaping.

ConocoPhillips says it is still investigating what went wrong at its Alpine field, where the gas leak discovered on March 4 led to the temporary removal of 300 personnel, alarmed residents in the nearby village of Nuiqsut, and halted oil production from the drill site.

As of Thursday, ConocoPhillips continues to detect “intermittent small amounts” of gas at the surface of the CD1 pad where the release occurred, said Rebecca Boys, a spokeswoman with the company. But the company had stopped the release at the source, she said.

Several questions remain unanswered, including an estimate of the leak’s size.

When the leak was discovered, a rig had been drilling a new waste disposal well planned to extend two miles deep, according to the company and permitting documents for the well, filed with the Alaska Oil and Gas Conservation Commission.


In public updates early this week, ConocoPhillips said recent data indicates the leaking gas originated from sands in a shallow gas formation.

The formation is located about a half-mile below the ground, according to permitting documents filed with the state.

The company did not install a layer of cement around the well as the well passed through the formation, ConocoPhillips said in updates on its response website this week.

That’s an important detail about what could have gone wrong, said Mark Myers, a petroleum geologist and former Alaska natural resources commissioner.

During drilling operations, oil companies place cement around the casing, or thick steel pipe, to prevent any hydrocarbons, such as natural gas, from escaping the well, Myers said.

ConocoPhillips said this week that it did not consider the formation to be “a significant hydrocarbon bearing zone.”

For that reason, cement was not required in that zone, the company said, citing Alaska administrative code.

ConocoPhillips cemented and sealed the well in deeper areas known to produce hydrocarbons, said Myers, who reviewed the well permitting documents.

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Asked Thursday if the lack of cementing caused the leak, Boys said the cause remains under investigation.

If ConocoPhillips had cemented the well in the shallow formation, gas would not have escaped there, Myers said.

“That would have sealed it,” he said.

It appears that gas escaped from the well and later spread across a broad area, percolating through the ground in multiple spots at the CD1 drill pad, Myers said.

The oil and gas commission issued the permit to drill the well on Jan. 4.

ConocoPhillips told the commission it did not expect to find gas in shallow areas near the formation where the leak originated, according to its drilling application. It said that four wells previously drilled near the disposal well had not “encountered any significant indication of shallow gas.”

Lois Epstein, a consultant with LNE Engineering and Policy who has been hired by a conservation group to track the response, said it’s surprising that ConocoPhillips wasn’t aware about the gas in the shallow zone.

CD1 is the oldest drill site at Alpine and was finalized in 2000. Dozens of wells have been drilled along the well row, a strip of land that’s about 500 feet long.


“Why did it happen if they drilled lots of holes very close there and they didn’t have any problems before?” Epstein said.

Throughout the release, gas was detected coming up through the ground across a broad area, at seven wells and at cracks in the surface near the rig that are also under investigation, according to the commission.

Boys maintained, as the company has throughout the leak, that natural gas has not been detected off the CD1 pad, located about 8 miles north of Nuiqsut.

State regulator struggled to get information

Also this week, emails emerged showing a state regulator with the Alaska Department of Environmental Conservation struggling to get information from ConocoPhillips during the leak’s early days.

The state released the emails following a records request by Adam Federman, a reporting fellow with Type Investigations, a nonprofit news organization based in New York City.

Kimberly Maher, northern region manager for the department’s Prevention, Preparedness and Response Program, told a ConocoPhillips employee in a March 7 email, three days after the release was discovered, that the company was required to report the release to the conservation department.

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The uncontrolled release of a hazardous substance through the ground for multiple days is reportable to the agency, Maher said.


Ari Haunschild, an environmental coordinator for ConocoPhillips, replied early on March 8 that ConocoPhillips did not view the release as a “reportable event” under its view of the agency’s regulations.

ConocoPhillips on its website Tuesday said it immediately reported the release to the oil and gas commission. It said the commission, a quasi-independent state agency, has jurisdiction over this type of leak.

The company said it also proactively informed Jason Brune, the DEC commissioner, about the event. As a courtesy it also notified other agencies, ConocoPhillips said.

“We determined a report to the Alaska Department of Environmental Conservation (ADEC) and other agencies was not required because the event was a natural gas release that did not meet ADEC criteria for a reportable event,” the company said on its website.

Despite the disagreement, ConocoPhillips provided a spill report to the conservation department after noon on March 8, Maher said in an in interview on Wednesday.

ConocoPhillips also filed a report with the conservation department after 600 gallons of salty water flowed out of three well houses at CD1 on March 9, the company says.

Still, nearly a week after the leak was discovered, Maher’s emails continued to show that she wasn’t getting the information she wanted from the company.

On March 10, Maher told Kate Dodson, an environmental engineer with ConocoPhillips working on the response, that she still needed more information about what was being done to identify and control the leak.

Maher on Wednesday said the early days of the release were a dynamic situation, and there’s always room for better communication with each emergency response. The communication soon improved, leaving her satisfied now, she said. ConocoPhillips began providing daily updates and attended an agency meeting that Maher called on March 11, she said.

Brune said in the leak’s first days that the department understood that the event was a subsurface release. In that context, it was the purview of the commission, he said.

But as the uncontrolled release through the ground continued, it was clear that the Department of Environmental Conservation had a key role to play.

“When we learned more about it, we got engaged, we got boots in the ground, and are remaining engaged,” he said.

Details emerge on potential cause of gas leak on Alaska’s North Slope (2024)


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