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Petroleum News: Shell: proven techniques

Vol. 12, No. 39  Week of September 30, 2007

Given the amount of research being done on Arctic oil spill response, Petroleum News asked Shell, a participant in the SINTEF Arctic oil spill response joint industry program, to comment on the viability of the techniques and technologies that the company has specified in its oil discharge prevention and contingency plan for its proposed Beaufort Sea drilling program off Alaska.

For example, Shell sees in-situ burning of spilled oil as a particularly valuable part of its arsenal of response tactics. But, has in-situ burning actually been demonstrated to work in Arctic waters or in sea ice?

Absolutely, said Al Allen, Shell’s oil spill response consultant. Allen has amassed 40 years of experience in oil spill response and was at one time the manager of Absorb, the organization that later became Alaska Clean Seas, the North Slope oil spill response cooperative.

There have been dozens of situations where people have burned spilled oil in cold climates, and with ice and snow, Allen said. Some current research focuses on expanding knowledge of the limitations of burning, but the technique has been proven to work, he said.

“I’ve done it several times myself,” Allen said. “… When you see the results at high (recovery) efficiencies, you just come away knowing that this is fact. … I know it works. It can be a very effective tool, especially in cold climates.”

Allen was also involved in some tests of in-situ burning, done in sea ice at the West Dock at Prudhoe Bay, in the late 1970s and early 1980s.

“We did a series of tests over about a three-year period,” Allen said. “The spill sizes would vary from just a few gallons to five to 10 drums at a time.”

Skimmers

And what about recovering oil from ice-laden water using skimmers?

Sea ice tends to trap the oil on water surface, so that the oil becomes concentrated in a limited area, rather than spreading out to form an extremely thin layer over a wide expanse of open water, Allen said. Skimmers work best when the oil is concentrated rather than spread out. But brush skimmers and rope mop skimmers have been thoroughly tested in the recovery of limited pockets of oil.

“Rope mops (for example) — I’ve used them in a lot of actual spills in cold climates and you can get 95 percent (recovery) efficiencies,” Allen said. “… There are many situation where skimming in ice, handled properly, can be very efficient.”

In fact, the effectiveness of a particular skimming operation depends primarily on the knowledge and experience of the skimmer operators, Allen said.

Allen also emphasized that determining a spill response strategy in a particular situation involves evaluating tradeoffs between the likely recovery effectiveness and potential disadvantages in the use of different techniques such as burning or skimming in that situation.

—Alan Bailey

See also…

Petroleum News: Protecting Arctic waters

http://www.petroleumnews.com/pnads/581959853.shtml

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