The term is cognitive dissonance. They invent ways to make it feasible. Most of the comments below explain the specific reasons. Interestingly, I had a boss who was an extremely devout, born again Christian, but who also held a doctorate in theoretical chemistry (quantum mechanics and such included). His argument for why the Earth was not 6000 years old was that he didn't believe an omnibenevolent God would make the Earth appear really old when it wasn't, because that's tantamount to lying. I never had the heart to explain to him that he was likely wrong, because you can't assume God would follow human logic. Not to mention he believed in standard theodicies, which means he'd believe God might use something like this to ensure a better outcome in the long run, one which we as humans could never predict.

My brother, who has a Phd, thinks the earth is 6000 years old - I asked him about how he can look at the Grand Canyon and see the millions of years of geological evidence and say that - he claims God made it that way. I don't try to convince him of anything.

I regret to say that is a silly question. They account for the oil and gas in exactly the same way they account for the fossil record, for the stratigraphic evidence, and for the light arriving today for stars which are millions of light years away - that is how god created it! I don't believe it, but I'm not prepared to say it's impossible.