He will have tanker endorsement. Cannot obtain hazmat until 21. He is 18.
With a class b license he could move the workover rigs. They service the existing wells working on the tubing inside the cased well.
He might want to look at roughnecking to begim with or a frak crew.
They pay pretty good and give you a place to stay.
On the drilling rigs you can find a company that works 2 weeks on 2the weeks off...bringing home about $50000 a year