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What caused an Alaska oil well blowout?

Alex DeMarban

Was it really a blowout when drilling mud and methane shot from Repsol's North Slope well on Wednesday?

Could just be a matter of semantics. But given the negative images conjured up by the term "blowout" -- the burning Macondo rig, lost lives, spewing oil -- an Alaska oil and gas official said she's calling Wednesday's incident "a loss of well control."  

"I hesitate to call it a blowout," said Cathy Foerster, a commissioner with the Alaska Oil and Gas Conservation Commission. "I call it a loss of well control because that does less to terrorize people."

Repsol, a Madrid-based oil major starting its first winter of exploratory drilling in Alaska, apparently hit a "shallow-gas hazard," or a pocket of high-pressure gas, that was unexpected but not totally out of line with North Slope drilling operations, said Foerster. No oil was spilled, workers were evacuated safely, and the rig was quickly shut down to avoid ignition.

Workers from Wild Well Control Inc. of Houston, Texas, reached the drilling pad at 5:30 a.m. Thursday and found gas levels low enough for its team to work safely.  “Air monitoring shows that the flow of gas from the well is minimal,” according to a morning update from the Department of Environmental Conservation. Small amounts of methane and water still flowed from the well Thursday afternoon but not drilling mud. 

Questions remain about whether human error was at play.

The well, called Qugruk 2 or Q2 was one of two being drilled by Repsol on the North Slope seeking oil. It's located about 75 miles northwest of Deadhorse. The company's other well is called K1, Kachemach 1. Being drilled by Repsol contractor Nabors Drilling, it's located about 30 miles southeast of Q2.  

The so-called Q2 "gas kick" began about 9 a.m. Wednesday. With the drill at about 2,500 feet, methane and 42,000 gallons of drilling mud were released from a diverter pipe 75 feet from the rig, with some spewing on the snow-covered tundra and the ice pad, said Jan Sieving, a Repsol spokeswoman. By Wednesday night, continuous flow of gas had ended and the well produced a moderate flow of water that began to diminish significantly, she said Thursday morning.  

Drillers use a mixture of minerals and water to lubricate the drill, remove cuttings from the bore and help control formation pressure underground, Sieving said.  

"Sometimes you encounter unexpected pockets of gas," Sieving said. "The well safety prevention mechanism operated as designed. No one was hurt. No oil was spilled, and we'll clean up all the drilling mud that was spilled."

"(Wild Well Control is) assessing it and hopefully by tonight or tomorrow the well will be controlled. Once well is controlled, the cleanup begins," Sieving said.

She said Repsol has begun its own investigation and is working with Nabors.  "(Nabors has) been very cooperative in working with us to get the well controlled," she said.  

It was the 11th gas-kick in North Slope history, Foerster said. It was the first time since 1994, where an incident occurred at the Endicott Unit in the Beaufort Sea, said an official with the state's Division of Oil and Gas. 

Oil reached the surface in only one of those 11 incidents: In 1950 at Cape Simpson during exploration drilling.

Industry response to the Wednesday morning incident generally went as designed, with Repsol following the steps outlined in the company’s contingency plan, said Foerster.

"We fine people for making bad decisions and doing things that aren't part of their approved plans, but we have nothing to indicate that they did anything outside their approved plans," she said. 

One big question is why wasn't the drilling mud, at 9.3 pounds per-gallon, heavy enough to keep the well from releasing, Foerster said.  "That's fairly heavy for a surface hole," she said. "It should have been plenty."

Repsol will also be investigating that question, Sieving said.

Before the drilling began, Repsol conducted the required shallow-gas hazard survey, a seismic test to search for potentially dangerous gas pockets.

"They looked at the seismic data, we looked at it, and we didn't identify it," said Foerster. "But that said, the technology is not perfect. Things can happen."

The commission requires operators to have blowout preventers. During exploration, that's a diverter. The Q2 diverter was installed near the rig to divert any gas release away, said Foerster. Diverters undergo weekly inspections by the commission, and this diverter passed its latest inspection some 36 hours before the release.

It did the job: "They engaged the diverter, and it worked," she said.

The company was also right to shut down all possible ignition sources and evacuate the rig, she said.  

"They did all those things, they did them right and everything worked," she said.

Contact Alex DeMarban at alex(at)alaskadispatch.com