How much oil would make Shell’s controversial Arctic bid profitable? What would be the impact of a catastrophic oil spill? And can the venture succeed as the world adapts to climate change?

As Shell’s Polar Pioneer rig whirrs through the Chukchi sea bedrock this week, there’s a lot riding on what it finds.

This is the first time the Anglo-Dutch giant’s star-crossed Arctic programme will drill deep enough to hit oil. The company has reportedly spent $7bn (£4.5bn) on getting to this point, including replacing its prize Kulluk rig after it ran aground off Alaska in 2012. For them to gain any of this back, a number of things need to happen.

Related: Ann Pickard: the little-known executive leading Shell’s gamble on Arctic oil

Related: The new cold war: drilling for oil and gas in the Arctic

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