This article states that Scotland's oil and gas reserves and tax incomes are dwindling: http://www.theguardian.com/politics/2014/feb/07/scottish-independence-economic-implications-niesr
Scotland's immediate fiscal position would be in a worse state than the rest of the UK, partly because government spending per person is significantly higher in Scotland, mainly because of higher spending on public services rather than benefits. In 2011-12 this was more than matched by greater revenues from oil and gas, but over the longer term this will not be the case as oil and gas reserves – and the revenues they bring – dwindle.
Is this correct? I read somewhere else that there is plenty of oil left to extract on Scotland's seas and oil companies are just extracting the amount the market demands.
EDITED: Thanks OddThinking for your edited question:
Will Scotland's reserves reduce so much that the costs increase so much faster than prices so that profits (and tax revenues) will drop quick enough, in the next 30 years or so, to significantly affect Scotland's oil and gas current tax revenues?