A ton of oil they sell, but don't spend the money from. The oil money is simply invested. They're one of the largest funds in the world. The government of Norway can spend 3% per budget year under certain rules, but rarely do. The first time it ever happened was in 2016.
When the oil runs out or demand for oil disappears, Norway won't plummet into poverty unlike a lot of other oil rich countries. The oil certainly made them rich initially, but their reluctance to spend money derived from oil will keep them rich.
