At today's prices. Do you really think oil demand will continue for the next 50-100 years at this level with all this investment in renewables? We're currently at a price slump close to pricing from two decades ago.
Its a little presumptuous to think oil will continue to have this value.
Wikipedia says it's a mixture of equities (60%), government bonds (25%), corporate bonds (10%) and real estate (5%). If (when) oil profits vanish, these investments will still be there. In fact, since they are legally unable to withdraw more than 4% of the fund's value each year (and typically make more than that), it should continue to grow indefinitely.
The fund has a really interesting set of ethical guidelines--they won't invest in tobacco companies, companies causing severe environmental damage, or those involved in nuclear weapons or cluster munitions, for example.
The Norway sovereign fund isn't the valuation of their oil businesses, it consists of 1T investments in non-oil businesses, including renewables, that have been funded by oil that's already sold at yesterday's prices. If oil become worthless tonight, they'd still have the 1T fund and it's ongoing proceeds.
Norway also has a state pension fund that is the largest in Europe at slightly over USD700B, bigger than California's pension fund.
Even if things turned bad Norway would still have USD250k~300k per citizen in state funds (if things turned out rosy it would be nearly USD650k per capita). Compare this to the USG of nearly USD9k per capita. In PPP terms Norway has little to worry about.