It was at a political fundraiser; people there are supposed to be US citizens are have a green card (or be working as staff). So it was probably mainly the US oil companies, but they actively cooperate with overseas ones to push up prices.
To be fair, this is an investigation of a solicitation for a bribe which happened 15 days ago, and was reported by the Washington Post the morning after it happened.
The Senate can’t do charges — that takes the House impeaching him or the Justice Department filing criminal charges. A senate committee can however, gather evidence, and then pass it to the Justice Department with a recommendation that they prosecute. That’s what’s going on here.
Probably can’t do one new set of crimes per day (the Senate doesn’t move that fast) but it’s definitely happening.