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Hilcorp continues to monitor gas leak Company waiting for sea ice to clear before repairing damaged subsea pipeline; new environment monitoring program to go into action ALAN BAILEY Petroleum News
In preparation to conduct repairs, Hilcorp is continuing to monitor a leak in an eight-inch subsea pipeline that supplies fuel gas to the production platforms of the Middle Ground Shoal oil field in Cook Inlet. On March 14 the Alaska Department of Environmental Conservation gave preliminary approval to Hilcorp’s latest environmental sampling and monitoring program - the company anticipates implementing the program in several stages, as conditions allow, using marine vessels, buoys and other equipment, Hilcorp has announced.
Hilcorp says that its response team is ready to carry out repairs to the line, with the necessary equipment staged, ready for the repair operations. But sea ice conditions in the inlet continue to render diving conditions too dangerous to commence the repairs - Hilcorp anticipates sending divers down to the damaged pipeline to carry out the repairs. The company says that it anticipates it taking several days to complete the work, once the repair operation has started.
To minimize the leakage rate, the company has reduced the gas pressure in the line by shutting down non-essential operations on the offshore platforms. Hilcorp has said that it does not want to completely stop the gas flow through the line, lest residual crude oil that may exist in the line escapes to the sea. The line had previously been used for the carriage of oil.
Discovered Feb. 7 The leak was discovered on Feb. 7 after Hilcorp had noted abnormal gas pressure in the line and had sent a helicopter along the pipeline’s route to check for a problem. According to a letter sent to Hilcorp by the Pipeline and Hazardous Materials Safety Administration, proposing a May 1 deadline for completing the repair, pipelines of this type in Cook Inlet are susceptible to damage as a consequence of rock abrasion, at locations where a line is not supported by the seabed. A vortex effect as a consequence of tidal currents can cause a line to vibrate, with the vibrations resulting in the line moving relative to the rocks. Apparently this particular pipeline has suffered leaks twice in the past. Conducting repairs involved installing bolt-on, split-sleeve clamps, PHMSA said.
PHMSA, recognizing the problem of diving safety in sea ice conditions, also commented that a complete shutdown of the gas line at this point could cause problems with a subsea oil transportation line freezing, given current seawater temperatures, should the lack of fuel gas cause oil transportation to cease.
Hilcorp has previously said that no significant impacts to wildlife or the environment have been observed as a consequence of the leak and that the gas release does not pose a threat to the general public. The fuel gas that the leaking pipeline carries consists of almost pure methane.
ADEC has been involved in the response effort as part of the incident management team. In a situation status report issued by ADEC on March 14, ADEC confirmed that, weather permitting, Hilcorp will commence environmental sampling and monitoring when the necessary sampling platforms and sensors arrive on site.
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