[Carry_Okie]

There is an extant theory that holds that the earth's mantle is a gigantic reactor that stores and releases methane captured in the formation of the planet. That methane is then consumed by subsurface bacteria that excrete long chain hydrocarbons. In short, the theory states that the earth produces oil continuously. A number of drilling experiments have apparently confirmed the hypothesis. I am sorry, but I don't remember the name of the scientist who first proposed it.

[Ernest_at_the_Beach]

Gold has a book "The Deep Hot Bioshpere" but I don't know if the theory you referenced is his!

[HiTech RedNeck]

Well the question does need to be asked, why would we expect all or even most of the earth's carbon and hydrogen to be at the surface? It's not like anyone dug down, say, even a hundred miles and found none.

[HiTech RedNeck]

That methane is then consumed by subsurface bacteria that excrete long chain hydrocarbons.

But then where does all the excess hydrogen go? Why aren't we seeing a lot of free hydrogen in gas wells? (It would be interesting, perhaps, to feed some of this bacteria to cows. Instead of methane, they produce gasoline for the farm tractors. Cool. Don't smoke in the barn!)