Not any more than you are taxed on your gross income, corporations, people, and trusts are taxed on their net income, not there gross. I know from which I speak. And I also know that big oil is using every accounting trick available to beat their income down to the tiny little amount that it is! Equipment is written off at a rate much faster than is the actual life span for that equipment. I am not saying that they are cheating, those are the rules as they are written but don't think for a second that they aren't doing every thing they can to beat those profits down.
"Profit" is what is left over after paying expenses. By the way, taxes are an expense -- a HUGE one in this example. Corporate dividends are paid on profits and does anyone out there seriously think dividends are paid on the pre-tax figures?
And another thing: if you take a serious look at the numbers, the by far lion's share of an oil company's gross income is in the upstream (crude oil) side of the business in this current market environment and NOT in the downstream (refining & marketing) side of the business. And thanks to the envirojerks, not very much of that crude oil is being produced inside the United States. So guess where that means the bulk of the oil company's money is being earned? You got it: foreign investments. And since they are not allowed to explore for oil in a meaningful way at home, it is the foreigners who are cashing in on all that investment.
So your big liberal politicians are hosing you two ways: taxes, both directly on you and indirectly on all the things you buy, and again by running industry out of the country and all their good-paying jobs with them.