This is more a story about reputational risk than environmental risk.
The oil on the Kulluk potentially threatens populations of salmon, sea lions and sea otters. But the amount of fuel - about 140,000 gallons - is tiny compared with the big Arctic spill of the Exxon Valdez in 1989, which poured tens of millions of gallons into the sea.
Shell says its record in the Arctic is good. It says it will investigate the incident and learn from it.
But the firm's offshore Arctic programme has already suffered from delays and regulatory problems. And environmentalists are saying the incident proves that it is too risky to drill in the far North.
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