I don't believe everything I was taught in school. I do hold everything I have been taught up to the light of skepticism. Taking the stance of devils advocate for a moment I will assume everything I have been taught is wrong and I must come up with a new explanation.

So....

How would nature get all that carbon underground?

Carbon dioxide is slightly soluble in water, anyone who drinks soda pop can attest to that. So when it rains there are millions of gallons water seeping into the ground carrying who knows how many tones of carbon dioxide with it. I think man has a minuscule capability of sequestering carbon dioxide compared to nature.

I have heard that Russia has a technology to turn carbon dioxide back into long carbon chains, or fuel. That brings me to my next question; How could nature do the same thing?

If we have water carrying carbon dioxide deep underground we would then need some way to strip the oxygen from the carbon in order for the carbon to bond with other carbon. Perhaps a catalyst of some kind could be used... Wait a minute, underground there are all sorts of minerals of almost every type. Not to mention electricity that flows through the ground (Granted the electric flow through the ground is minuscule but it is there and it could do some thing, to one degree or another). Catalyst would be plentiful in that situation.

What if there are pure metals, like calcium, that would strip oxygen from the carbon dioxide and let the carbon concentrate in small pockets in those deep underground water ways. That to me would make more sense of how the carbon gets deep underground rather than having miles of dirt being thrown on top of a forest or something.

I have heard of oil fields being sucked dry of oil only to have someone come back decades latter to check it and find even more oil in the previously depleted well.

So perhaps an oil cycle is sitting on top of the water cycle and is renewable, depending on whether other elements underground are consumed or not. If something like calcium metal, for instance, were oxidized then the supply of it could be consumed and be nonrenewable.

As for bio markers, I don't doubt that some kind of algae could live in underground waterways. Or, perhaps as the water seeps through the surface soil it picks up soluble products of decomposition. I'm sure bacteria could contribute also.

I don't know for sure. I am not claiming to know what actually happens underground. I do claim that we don't really know for sure yet. Hell, we act like we just came out of the dark ages or something.

check out nitrogen fixation

Oil is made internal by the earth, it than floats to the surface and breaks down to make water and everything else organic.

 yes  hydrocarbons are not fossil fuels as fossil fuels exist on titan, a moon in our solar system...this this theory has more merit than most .the question remains at what rate hydrocarbons are renewed in the sustainable cycle of energy creation....

We consume too much oil to ever get it from above the surface. Or we'd have to give up eating. There is not enough land surface on the Earth to house 7 billion, farm their food AND their oil.
Burning oil is so 1900. It's inefficient and wasteful. CO2 being the exception to the rule, plants can do good things with that.

I never understood the pressure supposedly creating our oil. But the BP rig obviously just puled the plug from a very large high pressure chamber. Perhaps the oil being of lower density than the material it was formed of, is creating this pressure, rather than the deposites of millions of years of vegetation.

If oil were to be found renewable (they do keep finding and finding new fields), that'd be bad news. Even more reason to suppress new fuel technologies, or even engines that actually take out a majority of the energy stored in the oil. Cars have not significantly improved fuel economy over the past decades. It's not like the car engine is set in stone like the basic bicycle. The double triangle can barely be improved upon, but the car engine, is like a Fred Flintstone device...

We consume too much oil to ever get it from above the surface. Or we'd have to give up eating. There is not enough land surface on the Earth to house 7 billion, farm their food AND their oil.

Oh well there is enough place, just want to remind you that USA alone produces a huge amount of cereals not only for themselves but enough for other continents too. And so you can do with plants for oil extraction. I agree however that we consume too much, therefore my suggestion was to remove at least 80% of personal cars and automobile industry because they are used mostly on useless occasions. And there we go: 1) you need much less oil and 2) the remaining is for public/trains/bus and industral purpose. It would be enough...