North Dakota's tax commissioner says the state's oil revenues could top $3.5 billion.
Lawmakers only expected to get just over $2 billion when they wrote the state's current two-year budget.
The first year of collections is in, and oil tax revenues total almost $1.7 billion.
Tax Commissioner Cory Fong says prices have stayed close to what the Legislature forecast.
But oil production is higher.
The Legislature forecast that North Dakota oil producers would pump up to 425,000 barrels of oil a day. In May, the average daily output was almost 640,000 barrels.