The Repsol exploration well that blew out Wednesday from pressure from a shallow gas pocket remained out of control Thursday but was leaking only small amounts of gas and water, state and company officials said.
An emergency crew from Wild Well Control Inc., based in Houston, arrived about 5 a.m. Thursday at the Qugruk No. 2 wellsite on the Colville River delta, about 18 miles from the village of Nuiqsut. Repsol-North America spokeswoman Jan Sieving said the Wild Well team believed it could kill the well Thursday evening or today, rendering it safe.
Ty Keltner, spokesman for Alaska Department of Environmental Conservation, said cleanup crews were standing by, awaiting an all-clear sign from Wild Well.
About 42,000 gallons of drilling mud shot out of a diverter outlet Wednesday, some of it landing on tundra. No oil came out of the well, officials said.
Commissioner Cathy Foerster of the Alaska Oil & Gas Conservation Commission revised an earlier report that the Nabors Alaska drilling crew was withdrawing the drill string from the well bore at the time. The Nabors crew was actually drilling through the 2,525-foot level of a projected 7,000-foot hole when they hit the unexpected high-pressure gas pocket, Foerster said.
The threat of explosion from the uncontrolled gas leak forced evacuation of the drilling rig. No fire occurred and no one was hurt.
In a situation report issued at 2 p.m. Thursday, the DEC said officials from the commission were conferring with Wild Well and Repsol on a plan to control the well. Air monitors showed the flow of gas from the well "is minimal" and the drilling pad safe for the Wild Well team, the DEC said.
Repsol, a relatively new player on the North Slope, is based in Spain, with U.S. headquarters in Texas. It had developed an aggressive exploration plan for this winter on recently acquired leases in Alaska.
"Once the well is secured, we'll assess the condition to determine if it's salvageable and will determine future plans based on that assessment," Sieving said.
Foerster, a petroleum engineer, said shallow gas is a common hazard in drilling. Repsol was required to analyze the geologic structures for shallow gas but missed the pocket.
"The technology is not perfect," Foerster said. "It did not show up on the seismic."
The well is the second one Repsol drilled in the area. The first didn't encounter the gas pocket, she said. Reviewing historical data, Foerster said the layer of gas might have been connected to a well called Cirque No. 1 that blew out in 1992. That well is about 24 miles south-southeast of Qugruk No. 2.
As part of its investigation, the AOGCC will review the shallow gas analysis for flaws and to learn how the blowout might have been prevented, she said. It will also look at procedures for drilling the early stages of a well, she said.
Though it was about a half-mile deep, the Repsol well was still considered a "surface hole," which has fewer protections against blowouts than the later stages of a drilling operation.
A standard blowout preventer -- the heavy mechanical device with valves, shears and other tools designed to contain a blowout -- can't be used on a surface hole because there's no pipe case in the ground to attach to, just a borehole through rock. Foerster said Repsol still had another 200 feet or so to go before pulling the drill from the well and inserting and cementing the steel casing. Once that was done, drilling would resume inside the casing with the blowout preventer at the surface.
In place of the heavy preventer, drillers are required to use a diverter, a pipe system to route gas from a blowout away from the rig to reduce the risk of explosion.
The diverter is tested weekly and a state inspector had just reviewed its functioning about 36 hours before the blowout, Foerster said. When drillers hit the unexpected gas pocket, "the diverter worked -- it did what it's supposed to do," she said.
As part of its review of the incident, the AOGCC may require wells to be cased at a shallower depth, she said.
Though no one was hurt, no equipment wrecked and pollution apparently minimal, a blowout is considered a serious incident because control of the well is lost.
"At this point, we're all scratching our heads going, why did this happen? We would not have expected them to take a kick on this well they were drilling," Foerster said. "We're looking to understand what happened so that we can prevent it from happening again."
The Repsol well was the 11th blowout on the North Slope and the 19th overall in Alaska since 1949, according to the commission, which regulates drilling for safety and conservation.
The blowout has been seized on by environmental organizations as a reminder of what can go wrong, especially if offshore drilling begins in the Arctic Ocean.
"This is yet another wake-up call for the Obama administration that oil and gas activities are risky business," said Susan Murray, a senior director of Oceana based in Juneau. "We are incredibly lucky this is not an oil well blowout offshore in the Arctic Ocean; because the nation is not prepared to deal with an accident like that in offshore Arctic waters where the ability to respond is limited at best, and impossible at worst."