ConocoPhillips prepares drilling rig to investigate and stop weekslong natural gas leak

ConocoPhillips is preparing a drilling rig in an effort to pinpoint the cause of a natural gas leak that began at its Alpine development more than two weeks ago, and which the company says has largely been stopped, according to the most recent update on its response.

The rig, Doyon 142, was drilling a waste disposal well on March 4 when the leak was discovered at the CD1 drilling site at Alpine, about 8 miles north of the village of Nuiqsut.

The subsurface gas leak prompted the company to halt the drilling and led to the temporary removal of about 300 non-essential personnel. The company says no one was injured and gas has not been detected outside the drill pad.

The released gas was originally detected from the ground at a wellhouse — a shack-like structure covering the top of a well. Since then, ConocoPhillips has reported that occasional and small amounts of gas have been detected at numerous wells and locations along the well row at CD1, including from tiny cracks in the surface.

The well row is a roughly 500-foot-long strip of about 50 wells.

The leak has prompted a broad investigation by ConocoPhillips, which has used ground-penetrating radar and other means to confirm that the drill pad itself is stable.

Oil production remains shut down at CD1, and output has been reduced at Alpine by about 9,000 barrels of oil daily, state data shows.

Some gas is being produced to control the release, according to reports from the Alaska Oil and Gas Conservation Commission and the company.

ConocoPhillips said it has reduced the gas that was being released at the surface by producing natural gas from the well that was being drilled, and by flowing gas through through another well, according to its updates.

“The release has largely ceased, and there are only intermittent low levels of natural gas being detected along the CD1 well row,” the company said Monday.

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ConocoPhillips also recently determined that the leak likely originated in a low-pressure formation of gas below the ground, not the deeper formation that ConocoPhillips targets to produce oil and gas.

Still, many details remain unknown, including an estimate of the amount of gas released.

CD1 is the oldest drill site at Alpine and was finalized in 2000.

It’s unusual for gas to be released at the surface across a large area, rather than at just one well, said Mark Myers, a petroleum geologist and former state natural resources commissioner.

“This is a mystery,” he said. “I’m really curious to see what the finding is. I’m scratching my head about how it’s coming to the surface broadly, and I don’t get why they didn’t know (the formation) was there.”

ConocoPhillips has said it’s leading the response but has hired some experts to help, including Wild Well Control out of Houston, Texas, a company that helps stop out-of-control wells.

“When Alaska operators have to get experts from Texas, that’s a big deal,” said Lois Epstein, a consultant with LNE Engineering and Policy who has been hired by a conservation group to track the response.

It’s unusual for the cause to remain unidentified so long after the discovery of a gas leak, Epstein said.

“It’s certainly troubling, and I’m sure it’s troubling to ConocoPhillips and everyone involved, that here we are over two weeks from the identification of the problem and they haven’t been able to figure out what’s going on,” Epstein said.

Dennis Nuss, a spokesman with ConocoPhillips, said the company is carefully taking steps to determine exactly what has happened, identify the cause, and find solutions.

“We have to make sure everything we do is done with safety top of mind and that’s why this takes time,” he said.

Some of the families that left Nuiqsut after the leak began have not yet returned, in part because so much remains unknown, according to Rosemary Ahtuangaruak, the village’s mayor.

“Some have returned,” Ahtuangaruak said. “Some have stated that they’re not sure if they are ready to come back.”

North Slope Borough Mayor Harry Brower, in a March 10 statement, had cautioned Nuiqsut residents that ConocoPhillips is monitoring the leak, while the oil and gas commission saw no threat to public safety. Brower’s statement, posted by ConocoPhillips on its response site, said “there’s no need” for people to leave Nuiqsut and an evacuation of residents was not considered.

ConocoPhillips has been confident since the start of the event that the community of Nuiqsut is safe, Nuss said.

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“We’ve also been confident about safety at our CD1 site, which is the reason we have brought a number of personnel back.”

Rebecca Boys, a ConocoPhillips spokeswoman, said in an email Monday that ConocoPhillips has regularly communicated with the village since the release was detected. She said outreach liaisons are also available in Nuiqsut with office hours, including over the weekend.

“There are no safety concerns outside of the CD1 immediate area and no natural gas has been detected outside the CD1 area,” Boys said. “The ambient air monitoring readings indicate normal air quality.”

Ahtuangaruak maintained on Monday that communication from ConocoPhillips has not been sufficient.

In addition to the initial observation of the leak at a single well house, about 600 gallons of salty water also flowed out of three well houses at CD1, the company has reported.

ConocoPhillips and the oil and gas commission are describing the situation as a gas “release,” rather than a leak.

“Here is why – the natural gas release was first observed from the ground at the wellhouse of well CD1-05. Release appropriately captures ‘from the ground,’ ” Boys said. “A leak would be more representative terminology if the natural gas (or hydrocarbon) was leaking” from say, process piping or similar equipment.

Minute amounts of gas have also been observed in cracks in the surface along the well row, and near the Doyon 142 rig, the company has also said. The cracks, up to a quarter of an inch wide, were observed at the pad on March 7, the company says.

“Flowing gas is not present,” ConocoPhillips said of the cracks.

ConocoPhillips has also reported to the oil and gas commission that “low levels of natural gas” have been detected at seven wells, but not outside the wellhouses, Boys’ email said.

The oil and gas commission said in a statement that state regulators inspected spill-prevention equipment on the Doyon 142 rig over the weekend. Safety inspections are required before the rig can begin conducting diagnostic work in the well. The commission said Tuesday the rig has begun well work required before “well diagnostics” can begin.

The rig will be used to help identify the leak’s cause, the company says. Future work on the well that was being drilled may be needed to “permanently seal the gas release source,” the company said in an update on Monday.

“Once the gas source is pinpointed, it will be targeted and sealed off with cement,” the company says.