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By far the biggest riser on the stock market today is .

That partly reflects the Edinburgh-based oil explorer beating market expectations. But in the oil exploration business, the more important figures to watch are in reserves and future prospects.

There's good news on both, as Cairn seems to report quite regularly. Reserves in its gigantic Indian oil field are showing signs of being even bigger than expected, and the company wants permission from the Indian government to boost production by nearly a third.

Next stop: Greenland. Cairn now has a partnership with Petronas, and is bullish about the prospects there. It's hard to be sure what lies under the seabed, as there's been so little drilling west of Greenland before. The company will know more when its leased drill ships get to work this summer.

And it's taking a bit of care to make sure it keeps social and environmental concerns under a watchful eye, where tiny local communities face a big impact from the arrival of big oil.

Two figures in today's announcement from chief executive Sir Bill Gammell that ought to give pause for thought: chances of success off Greenland are put between 7% and 14%.

That's the thrill of the oil business. The upsides are immense, but so are the risks.