Not unusual to see a serious topic fracture into 15 more/less related topics, but that's Mudcat...

Pied Piper asked "...how long it takes the CO2 produced by burning hydrocarbons to be sequestered back as hydrocarbons and Carbonate rocks"(?)

ans: It probably doesn't matter. The shear size of planet Earth will enable us to utilize oil and natural gas until mankind dies out. That will not come from the usual model presented for global warming. The CO2 is largely consumed by plants which convert it back to O2, more/less the reverse of the burning process that created CO2 and water. Here is a real danger: as the Earth's population soars, trees are cut down and land becomes covered by houses, schools, public buildings and roads. Result is that CO2 formation exceeds the ability of the remaining plant to convert it back to O2.

Again from PP: "The point about Bio fuels is that the Carbon cycle time is very short (a few years tops) oil takes millions of years to form or if it's "exuded" from non-organic sources of Carbon then the cycle time is infinite! "

ans: Not exactly. The oil and gas being produced are very deep. The Earth's core is a molten, super-heated mass and the ingredients of the fuel are being pushed outward toward the Earth's surface. It probably travels as gas, maybe as liquid. Carbon-containing rocks near the surface have little to do with the process. Also, the material we can reach started it's journey long ago, maybe millions of years.

By the way, If you are willing to drill a 40,000 foot deep oil well, you can probably do so on any piece of land on the planet and find a significant amount of oil.