Do you happen to know what happens to the bulk of the actual oil and gas (rather than the financial proceeds) extracted from public land? Logic would suggest it gets refined and used within the US. It's my understanding that the US exports a fairly small amount of oil, but I don't know its origin.

Also, do you know whether the lease/royalty system is fixed in law, or could the government, at least in principle, retain (or regain) possession of the oil and gas under public land and pay companies to extract it?