Hilcorp finds 2-inch gash in leaking natural gas line in Cook Inlet

Repair divers inspecting a natural gas leak at a Hilcorp Alaska pipeline in Cook Inlet have found a gash that appears to have been caused by a boulder on the seafloor.

With the recent warm weather and the melting of Cook Inlet ice, Hilcorp was able to send contract divers to two locations — the leaking gas line, by Platform A, and an oil pipeline that was suspected of leaking crude near the Anna platform. After inspecting the Anna pipeline, Hilcorp said it was not the source of a small crude oil leak on April 1.

At the site of the leaking gas line, divers worked over the weekend to locate the hole and are preparing to install a temporary clamp to prevent further methane leaks. The gas is used to fuel operations at Platform A and three other platforms.

The gas leak was discovered Feb. 7 when a Hilcorp helicopter spotted roiling water. The leak site is located northwest of Nikiski, on an 8-inch steel pipeline running to Platform A.

The damaged area of pipe was about 2 inches in length, on the "very bottom of the pipeline resting on a boulder embedded in the seafloor," Hilcorp said in a statement issued Monday by Lori Nelson, the company's spokeswoman.

Two leaks on the same gas line in 2014 were repaired by the pipeline's previous operator, XTO Energy. Those were also blamed on rock abrasion.

Hilcorp said that once the temporary repair is completed, the company will further inspect the pipeline and permanently repair the leak.


The leak was initially reported as about 275,000 cubic feet of gas daily but was later reduced to 100,000 cubic feet of gas daily, on average, after oil production was stopped at the Middle Ground Shoal field.

Meanwhile, the company said a subsea pipeline off the Anna platform was not the source of oil sheens spotted on Cook Inlet's water on April 1. But that hasn't changed the view of a federal agency that ordered the company to take action addressing what it says was a crude oil leak from a pipeline.

"There's been no change to our approach," Darius Kirkwood, a spokesman with the Pipeline and Hazardous Materials Safety Administration, said on Monday.

Hilcorp has said that less than three gallons of oil spilled. The company continues to investigate the cause of the sheens, it said in the Monday statement issued by spokeswoman Nelson.

On Saturday, Hilcorp completed a pressure test of the 1.6-mile pipeline running between the Anna and Bruce platforms in western Cook Inlet. Divers also inspected it after sea ice was no longer a danger to divers' surface tethers.

The pipeline was found to be intact, without damage and in good working order, Hilcorp said.

The eight-hour hydrostatic test, using water in the pipeline and increasing the pressure beyond the pipeline's maximum operating pressure, was observed by state and federal agencies, the company said. The results of the test, the inspections and the small amount released confirm that the pipeline was not the source of the sheens, Hilcorp said.

Multiple sheens were spotted for a short period on April 1, as well as bubbling, after workers on the Anna platform felt a strong impact to the platform. The largest sheen was reported to be about 10 by 12 feet in size.

Suspecting the 8-inch pipeline, the company quickly shut it down. Hilcorp directed oil still in the pipeline to the Bruce platform, replacing it with filtered seawater.

PHMSA issued a corrective action order late last week to Hilcorp, requiring the pressure test, the visual inspection and other steps, in response to a crude oil release from the pipeline.

The order requires that Hilcorp submit a final report by July analyzing the root cause of the failure, including lessons learned.

Alex DeMarban

Alex DeMarban is a longtime Alaska journalist who covers business, the oil and gas industries and general assignments. Reach him at 907-257-4317 or