The shutdown of a satellite field on Alaska's North Slope will not stop BP PLC from beginning the process of cleaning out a corroded transit line in the largest US oil field.
"We're going to start a series of maintenance pigs [pipeline inspection gauge] this weekend," spokesman Steve Rinehart said on Friday.
On Thursday, BP shut down a satellite Prudhoe Bay oil field after workers detected natural gas leaking into a manifold building, a key control facility. BP closed the Lisburne production center that processes crude oil and gas coming from the Lisburne field and the neighboring Point MacIntyre oil field.
The shutdown of Lisburne, a satellite field that feeds into the Prudhoe production stream, sent production down by 25,000 to 30,000 barrels per day, about 4 percent of North Slope output.
Methane gas from a high-pressure 35cm pipeline somehow filled the unoccupied manifold building Thursday morning at Drill Site L2 along the shore of Prudhoe Bay, Rinehart said.
The gas had dissipated by late Thursday night.
"There's no estimate at this point of when production will return," Rinehart said. "We're kind of moving on two priority fronts: to complete the investigation and safely return to production."
The shutdown was a setback in what had been a gradually improving oil production picture since the eastern side of Prudhoe Bay ceased production Aug. 10, a few days after a leak was discovered in a corroded transit line.
The western side of the field kept producing after the company determined it could be operated safely. Its output is about 200,000 barrels a day.
For the last several days, BP had been restarting wells on the eastern side.
And starting this weekend, the company will send a pig "that doesn't fit too tight" down an 8km segment of the eastern transit line, Rinehart said.
In the following days, the size of the maintenance -- or cleaning -- pigs will become sequentially larger to clean out any deposits.