Those who have expressed views about "ownership" of the North Sea on this thread should click
http://www.bbc.co.uk/news/uk-scotland-scotland-politics-20042070 and scroll down to the map.
I don't think that Scotland's residents will vote for independence next year but, if they do, the map shows pretty accurately the sea areas that would "belong" to Scotland and England separately. As regards the Shetland Isles, just look at the map and note how much of the blue sea-area would belong to
them, even in the unlikely event of their becoming independent!
The oil and gas in the English part...ie the western half of the southern North Sea...are dwindling fast, whereas the Scottish part to the north is where new discoveries are still being made. Cameron was up in Aberdeen a few months ago 'celebrating' one.
More to the point perhps is the fact that future prospects of oil discovery are far more likely in the North Atlantic than in any part of the North Sea. England, having no coastline abutting the relevant part of the Atlantic, would have no claim whatsoever there. Accordingly, revenues from oil companies operating in these northern waters would flow into the Scottish - not the UK - treasury in the event of Scottish independence.