The oil revenues are more than likely, millenial. (In fact, huge reserves are known and untouched, and many other areas look promising.) The cash the oil and gas generate is not.
The model is Saudi Arabia, in which the cash generated a population explosion, which no amount of oil revenue can afford to support in socialistic luxury. While I do not expect a Norwegian population explosion, their immigrant population, mostly Muslim, is growing by leaps and bounds. Not being culturally given to enthusiastic labor, these folks will demand the same gravy train as received by Norwegian Norwegians. That'll bust'em!
I definitely recommend that the Norwegian Royal Family lead the nation in demanding an entrance exam for all Muslims ... part of which is to consist of eating pork roast, rye crackers and lutefisk, and washing it all down with Akvavit. Survivors who then accept Lutheran doctrines, may be eligible to apply for residency, if good looking enough.
Survivors who accept Lutheran doctrines, may be eligible to apply for residency, if good looking enough and able to name all the parts of the running rigging of a Colin Archer Ketch, in Norwegian of both the Bergen and Oslo varieties.