BP pipe rupture caused by external corrosion
A preliminary investigation into the Sept. 29 rupture of an eight-inch high-pressure pipeline on the North Slope points to external corrosion as a likely cause, BP and state officials say.
The pipe was carrying carrying gas to a Prudhoe Bay field production pad.
Allison Iverson, director of the state Petroleum Systems Intergrity Office, said BP’s initial investigation indicated the presence of external corrosion, but other factors may have also been involved.
Iverson said the state is working with BP on reviewing maintenance and operations procedures for flow lines serving production pads in the Prudhoe field.
“Fortunately no one was hurt and there was no fire, but this could have been a very serious incident,” Iverson said.
The gas line was operating at 1,600 pounds per square inch and was carrying gas to be used in gas-lift equipment in the producing wells.
BP spokesman Steve Rinehart said no one was near the pipe when it ruptured but there were workers on the pad at the time.
“Our safety systems worked as intended, including pressure-sensitive automatic valves. The pad operator notified the central field controllers, who shut down the facility,” Rinehart said.
A preliminary report on the incident showed the presence of external corrosion on the pipe where insulation had been removed and water had accumulated, Rinehart said, but there may be other factors, such as problems in metallurgy, which are still being investigated.
BP is now carrying out inspections of other flow lines in the field where similar circumstances may be present.
Two Prudhoe production pads, Y Pad and P Pad, remain shut down as the investigation continues and repair work is done, BP spokesman Steve Rinehart said. About 5,000 barrels per day of production is affected by the shutdown, he said.
Iverson said oilfield flow lines are under the regulatory jurisdiction of the state PSIO, a division within the state Department of Natural Resources. Federal pipeline safety regulators have jurisdiction over larger field pipelines that carry crude oil from processing facilities to the Trans-Alaska Pipeline System.
However, federal regulators are providing technical assistance to the state under an agreement between state and federal agencies, Iverson said.
BP is meanwhile continuing a project to replace major field crude oil pipelines that were damaged by internal corrosion and taken out of service in 2006. Rinehart said construction of four pipeline sections is complete and two segments are in operation with the other two expected to go into service by the end of the year.