Under current law and regulations, it would be much easier to build a new nuclear plant in the US than it would be to build a new refinery. In fact, the US Government has offered incentives for the power industry to build new nuclear plants. There is no such offer on the table for new refineries.
I'm sure the oil companies would love to build new refineries if for no other reason than to utilize new technology to lower their marginal costs per barrel of product. But no one in the industry is stupid enough to play "bet your corporation" on projects that under existing rules would never get past endless court cases. If you think $10 billion would build a refinery (probably less than $2 B would do it) then double or tripple that cost for the effect of endless construction delays and compounding interest charges resulting from those delays which can be instigated by one single "concerned citizen" and one idiot Federal judge.
The oil industry saw what the idiotic legal/regulatory system did to the nuclear industry back in the 70s and 80s, and they aren't going to make the same mistake. They will build refineries, but they won't be in the US unless something changes.
Well, if you're right about a refinery costing about $2 billion, then Exxon could use the other $8 billion it made last quarter lobbying Congress for environmental law reform.
Exxon would still have the other 9 months of the year to show as profit.
$8 billion would definitely buy some votes...
Heck, they could use the $8 billion to raise a small army and take over one of the islands in the Caribbean (Haiti?) for the refinery, if they wanted to.