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Study looks at Port Valdez wave problem University of Alaska Anchorage researchers recommend tactics to avoid weather-related disruptions in the loading of oil tankers Wesley Loy For Petroleum News
A new study suggests ways to avoid weather-related disruptions in oil loading at the tanker dock in Valdez.
The study, still in draft form, is the work of Maria Kartezhnikova, a graduate student in the University of Alaska Anchorage School of Engineering; her professor, Orson Smith; and Peter Olsson, Alaska state climatologist with UAA’s Environment and Natural Resources Institute.
Strong winds out of the east can be a serious problem at the Valdez Marine Terminal, where tankers arrive regularly to load Alaska North Slope crude oil.
The terminal operator, Alyeska Pipeline Service Co., deploys boom around tankers during loading as a precaution against spills.
Wind-driven waves can prevent safe deployment of boom, or overtop the boom. This can prevent or interrupt tanker loading, and ultimately can force the curtailment of oil production from the North Slope.
In November 2006, for example, high wind and waves forced a shutdown of the 800-mile trans-Alaska pipeline, which brings the oil to the Valdez terminal. The pipeline shutdown was necessary because tankers couldn’t load and the terminal’s storage tanks were full.
‘Wind and wave shelter’ The researchers looked at wind patterns at Port Valdez, and considered ways to reduce oil loading disruptions during sustained winds of 30 knots and waves of 2˝ feet.
They focused on Berth 4, one of the two active tanker loading berths at the Valdez Marine Terminal.
They recommend “operational experiments” such as deploying another length of oil boom upwind of the primary boom, or positioning a tug and barge with their hulls aligned across the wind to create a “wind and wave shelter” for Berth 4.
The researchers rule out installing a floating harbor breakwater, due in part to the navigational hazard it could pose.
The Prince William Sound Regional Citizens’ Advisory Council had a hand in the study, agreeing to provide up to $2,500 to cover travel expenses for the researchers to visit Valdez and the marine terminal.
Alyeska is supportive Alyeska spokeswoman Michelle Egan told Petroleum News on Dec. 12 that Alyeska hadn’t yet had an opportunity to review the wave research in depth.
“We support the UAA School of Engineering and value the opportunity to review its scholarly work and consider its application for our operation,” Egan said.
Weather is a factor for tanker loading and does cause delays, she said.
“Sometimes Port Valdez is closed due to weather and tankers wait outside the entrance,” Egan said. “If the port is open and tankers are at anchor, we put crews and equipment in the water to set boom. We won’t send crews out for that activity unless it is safe to do so.”
If boom is set and water is splashing over it, oil can’t be loaded onto tankers, she said.
Loading delays are common through the winter months, Egan said.
The “perfect storm” is when crude inventory is high at Valdez, weather is poor and tankers can’t load, she said.
At that point, “pressure mounts all the way up to the North Slope,” Egan said.
Oil producers must “prorate” or dial down their output until some inventory can be moved onto tankers.
“The further we prorate, the closer we get to a shutdown,” Egan said, which is highly undesirable in winter due to the potential for pipeline freeze-ups and other problems.
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