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Alaska operator shuts production at two platforms over gas leak, discovers new oil leak

03 April 2017

On April 1, Hilcorp Alaska said it had discovered a crude oil leak from an undersea pipeline near the Anna production platform in the Cook Inlet southwest of Tyonek. The oil leak is on the west side of the inlet and is unrelated to the company's ongoing natural gas leak on the eastern side of the basin near Nikiski.

Stock image
Stock image

Oil and gas production was temporarily suspended a week earlier on both the Anna Platform and the nearby Bruce Platform because of the gas leak.

The oil leak was noticed after workers on the Anna Platform "felt an impact" and spotted an oil sheen, according to the Alaska Department of Environmental Conservation (DEC).

"In looking over the side of the platform to see what was going on, personnel observed sheen and bubbles coming up from near one of the platform legs where the 8-inch line is located," the state agency said in a situation report issued. "Personnel confirm that the bubbles or sheen were not observed the day prior."

On an overflight, Hilcorp staff observed six sheens on the water, according to DEC’s report. An hour later, during another flyover, no sheens were observed.

The company’s response contractor, Cook Inlet Spill Prevention and Response, Inc., sent a ship out to the Anna Platform but did not see any sheens. CISPRI is also serving as the Incident Command Post for a Unified Command in response to the spill, with representatives from Hilcorp, the US Coast Guard and DEC, according to the report.

Kristin Ryan, director of DEC's Spill Prevention and Response division, said she was not sure if the incident had been caused by ice, and did not know the extent of the leak.

The Anna Platform was originally constructed in 1965 by Amoco and has changed hands several times. Chevron was the last owner before Hilcorp took over.

Infrastructure on and supporting the platform has had regular failures. When BP forced air into a pipeline to the Anna platform in 2002, it sprung several leaks, causing crude oil to leak and create sheens as large as 200 yards wide and five miles long. Eight years later, in 2010, Chevron chose to suspend crude oil operations from the Anna platform after the US Pipeline and Hazardous Material Safety Administration refused a waiver to allow a corrosion-damaged pipeline to be used.

Hilcorp took over the platform in 2011 after Chevron pulled out of operations in Cook Inlet. The company bought up the area’s ageing infrastructure as other companies withdrew and is now the Cook Inlet’s dominant producer.

On April 2, Alsaka Governor Bill Walker issued a statement saying the DEC was keeping him updated on the situation.

"It has been less than a week since Hilcorp agreed to temporarily shut down oil and gas production as part of its response to a leaking gas supply line," he said in the statement. "Now, Hilcorp has reported a separate leaking oil line — which is significantly more harmful than natural gas. I am deeply concerned about the potential impact to the environment."

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