Oil's salient feature is (or, at least was) its high EROI - energy returned or made available per unit of energy invested to achieve that. At first, you would just stick a pipe in the ground and the stuff would gush out under pressure. The EROI was 10000%. The energy profit was used to build the modern world. Fossil fuel EROIs for new projects (deep water, tar sands) are now in the 200-300% range, and they are only going to head lower (on average over total production). At some point we aren't going to be able to sustain modern society. People joke that that's just fine with them, but really it's a horror (lack of cheap fertilizer = mass starvation), particularly since it is avoidable.

Fission and fusion are our main hope for returns to high EROI. Renewables are worthless in this respect, which is probably why the neo-luddites love them. Fusion appears to be a pipe dream. Uranium based fission gives us a couple of hundred years before we hit "peak Uranium", but Thorium based fission gives us millenia (the amount of Thorium appears similar to the amount of Uranium until you realize that we can only use a tiny fraction of naturally occurring Uranium).

Once you have high EROI you can do stupid things like suck CO2 out of the air and turn it back into liquid fuel if you really want to. But without high EROI, the Malthusians just might get to say "I told you so."