First BP Exploration Alaska will complete the cleanup of a spill at the Lisburne drill site on Alaska’s North Slope, then it will dig up the pipe.
An estimated 2,100 to 4,200 gallons of methanol, water and crude oil spilled early Saturday onto a gravel pad and into a tundra pond at the production facility, said Alaska Department of Environmental Conservation (DEC) officials.
The spill occurred as crews tested newly installed valves by pressurizing a section of pipe that crosses beneath a road.
The valves held up but the pipe failed, said Tom DeRuyter of the DEC’s Spill Prevention and Response Division.
“It obviously ruptured. We know that part. Why it ruptured, we don’t know yet and we won’t for a while,” DeRuyter said. “They want to have the response to this completed and the spill cleaned up prior to going out and excavating that line.”
The pipe was an 8-inch line used almost continuously to move fluids from wells on the pad. The purpose of the pipeline is to divert production from individual wells to a test separator that measures the flow of oil, gas and water as required by the state, BP spokeswoman Dawn Patience said.
The section under the road, about 50 feet or less, gets protection from vehicles by structural casing. “It’s like a pipe within a pipe,” DeRuyter said.
BP partially drained the inner pipe for the work replacing valves, where they did find corrosion. Workers added fluid to the pipe as part of a leak test, and when pressure reached 949 pounds per square inch, the pipe failed. Fluids released flowed from both ends of the structural casing. BP said they detected the spill immediately.
“The test was terminated and spill response was initiated,” the company said.
Hydrostatic pressure testing is a common and accepted method for integrity testing and is one of the ways an operator ensures safe and reliable pipeline operations, the company said.
Vacuum trucks by Monday had recovered more than 600 gallons of methanol and produced fluids. Spill responders were using “flush and recovery” on the spill, DeRuyter said, gently flooding the spill area with fresh water to dilute the mix, and recovering the rinse water. Methanol, he said, mixes easily with water, but crude oil is stickier.
“It takes repeated flooding to get that off,” he said.
The company expects to have the area cleaned before freeze-up in the fall. DeRuyter called that realistic.
The Lisburne Production Facility had been down more about a month as part of planned maintenance. DeRuyter said cleanup crews would take a break Tuesday as the facility partially comes back online.