Hilcorp shuts two Alaska Cook Inlet oil platforms on gas leak

Anchorage — Hilcorp Energy has shut down two Cook Inlet oil production platforms amid another natural gas leak from a decades-old submerged pipeline that has leaked before, the Alaska Department of Environmental Conservation, or ADEC, said in a situation report issued April 5.

The pipeline supplies fuel gas to platforms A and C in the Middle Ground Shoal field in the inlet.

The leak was detected April 1 when a helicopter pilot noticed bubbles on the surface of the water while making a supply delivery, according to the state environmental agency. Hilcorp Energy, the owner and operator of Cook Inlet oil and gas production, shut down the pipeline April 3 by closing block valves to isolate the leaking section. The 8-inch pipeline is in 80 feet of water.

Hilcorp said it would begin sonar scans April 6 to locate the source of the leak, ADEC said in a situation report, and diving operations will begin as soon as ice conditions permit to determine the cause and to plan repairs.

The quantity of gas being leaked is unknown, but the pipeline operated at 190 psi prior to the gas release, the agency said.

Hilcorp was not available for comment.

Natural gas is defined as hazardous by the ADEC, and because of that Hilcorp could be subject to fines.

Hilcorp dealt with problems with the same pipeline in 2017, and gas leaked for several months until ice and water conditions were safe enough to do repairs.

Bob Shavelson, director of Cook Inlet Keeper, an environmental organization that monitors industry activity in the inlet, said the same pipe had experienced leaks in 2014.

Most of Cook Inlet's oil and gas production infrastructure, including offshore platforms and submarine pipelines, was built in the 1970s. The inlet now produces about 13,000 b/d, according to Alaska Department of Revenue data.

Operating companies do not have pressure-monitoring equipment in place to be able to detect a gas leak or oil spill, and rely mostly on observers like pilots, vessel operators or fishermen to report gas or oil in the water.

"We issued a report several years ago on the condition of offshore infrastructure in the inlet, and there were several improvements that came from that," Shavelson said in an interview. "However, there's only so much you can do with a 55-year old undersea pipeline."

"We're dealing with dinosaur technology here," he said.

Platforms A and C are two of 10 oil production platforms in the inlet, but not all are operating. Platorms B and D, also in the Middle Ground Shoal, were shut down several years ago, although Hilcorp has conducted studies on restarting one of them.

The bulk of the inlet's oil production comes from North Cook Inlet, while most natural gas production comes from onshore fields on the Kenai Peninsula and at Beluga on the inlet's west side. There are two offshore platforms that produce gas, however.