It's not just about the tax either
its the infrastructure - part of the $55 per barrel will go to local service companies, who then spend the money locally, where more tax is, and more infastructure drips down to the taxi driver, hairdresser etc etc etc
Aberdeen is now a centre of excellence - so even without Oil in the North Sea there would still be folk in the North East involved in the Oil Industry taking back money to spend there.
Joke in the Oil Industry, that people i know/meet dont realise Aberdeen is only 240,000 given the amount of Aberdonians they meet