Hilcorp shuts down Anna platform, purges line after small oil leak

Hilcorp Alaska has been dealing with a fuel gas leak at its Middle Ground Shoal field in Cook Inlet since early February, has reduced flow from the leaking line and is awaiting safe conditions in the inlet for divers to do an inspection and make repairs.

On April 1 the company shut down crude oil production from the Anna platform in its Granite Point field after personnel on the platform felt an impact and observed a sheen and bubbles near one of the platform legs where an 8-inch crude gathering line is located.

The first situation report from the Alaska Department of Environmental Conservation’s Division of Spill Prevention and Response said Hilcorp shut-in the Anna platform and reduced pressure to the line, which runs between the Anna and Bruce platforms, from 70 psi to 5 psi. DEC said the 8-inch pipeline is some 75 feet below the water surface.

A unified command - the U.S. Coast Guard, DEC and Hilcorp - was established in response to the sheen and said in an April 2 statement that three flyovers were conducted April 1 with several sheens spotted some 3 miles downstream from the platform during the first flyover, but no sheens sighted during two later flyovers.

Since the suspected source of the release was the oil pipeline between the Anna and Bruce platforms, platform crews displaced the oil in the line with seawater.

In addition to USGS and DEC personnel observing the displacement operation from the platform, a vessel from Cook Inlet Spill Prevention and Response was on scene.

The unified command stood down April 3 after a final flyover that morning confirmed no sheen.

The command said Hilcorp had displaced all of the crude oil from the suspected leaking pipeline with filtered seawater and that a diving crew was assembling in the region with appropriate support vessels and the divers would investigate and do repairs as soon as it was safe to do so.

The command said the exact cause of the release is unknown and remains under investigation.

In an April 3 situation report DEC said the 8-inch crude line between the Anna and Bruce platforms had been isolated and the pressure reduced to zero psi, with a pigging operation to displace the crude oil completed the evening of April 2. The crude oil was displaced with 490 barrels of filtered sea water which was pumped behind the pig from the Anna platform.

DEC said the amount of crude oil released was estimated to be less than 10 gallons.

In an April 3 release Hilcorp said all oil had been removed from the line and there was no indication of further release.

“Based on standard calculations for the number and size of the initial oil sheens and the amount of oil recovered from the line, Hilcorp estimates the total volume of this spill to be less than three gallons of oil,” the company said.

Hilcorp said the 8-inch line is 1.62 miles in length and was acquired by Hilcorp in January of 2012. The company said an inline inspection of the entire line was conducted last June along with visual inspections of certain exterior portions of the line.

Hilcorp spokeswoman Lori Nelson told Petroleum News in an April 5 email that no specific date had been set yet for divers to inspect the line.

- KRISTEN NELSON