If we want to fly big into unproven resource potential, then let's fly to a moon, (where hydrocarbons are formed that are not sedimentary BTW).
Titan's Surface Organics Surpass Oil Reserves on Earth
On any planet or moon where there is Hydrogen and Carbon without sufficient Oxygen, the molecule eventfully revert to their lowest energy state. That is what you get. But it is tough to use a hydrocarbon as fuel without oxygen. On earth, when those complex molecules from algae and the like get trapped away from oxygen, they also decompose to similar states. We can harvest oil directly from fresh algae but it has been difficult to make it economic.
The more thermally mature, the more they have broken down to the lowest entropy state like Methane, if there is enough Hydrogen. If not, you get the heavier hydrocarbons like ethane, propane, etc. Just a matter of time, heat, pressure and the ratio of the available atoms in the molecules.
Same process we use every day in crackers, cokers, and the like in refineries and similar process units.