Hilcorp Alaska LLC curbed pipeline pressure on an underwater gas pipeline that has been leaking for months and shut in nearby offshore oil production dependent on the line's gas, the company announced March 27.
The Hilcorp Energy Co. subsidiary reduced pressure on the breached line to the minimum safe pressure of 65 pounds per square inch. The company said the reduced leak rate is estimated to be 85 Mcf/d to 115 Mcf/d, and it noted that the pipe needs at least that level of internal pressure to prevent water from entering the pipe and creating additional problems.
The company has reduced the pressure a few times in March, down to 145 psi as of March 13, at which point the leak rate was estimated at 193 Mcf/d to 215 Mcf/d.
The leaking eight-inch pipeline brings processed gas to offshore oil production platforms in the Cook Inlet for fuel, while a nearby line carries crude oil from those platforms to shore. With the offshore production halted, pumps are circulating filtered sea water through the adjacent oil pipeline to reduce the risk of freezing in the line, according to the company.
"Production will be restored when Hilcorp, along with federal and state regulators, confirm that it is safe to do so," the company said in a March 27 email. "Based on current weather forecasts and ice conditions Hilcorp expects to mobilize equipment and deploy divers to begin repair operations within the next 10 days."
Hilcorp said conversations with the Alaska governor and state Department of Environmental Conservation prompted the company's decision to shut in offshore oil production and reduce the gas pipeline pressure. The leak was discovered and reported in early February but may have been ongoing since December. Cold and ice have prevented the company from being able to access the subsea pipeline to make repairs or to safely stop oil flow through the second pipeline.
The fishery division of the National Oceanic and Atmospheric Administration has expressed concerns about the flow of gas into Cook Inlet water, including the methane's potential impact on endangered beluga whales. The U.S. Pipeline and Hazardous Materials Safety Administration has given Hilcorp a May 1 deadline to get the gas leak under control.