All the oil and gas were once biological material. That what the tell me, there is no such thing as abiogenic petroleum .
Still, make methane from stellar carbon and hydrogen. 'sorb into/onto rock, bury it deep enough or run molten lava over it and it starts breaking down, lose a hydrogen meet another methane that's lost a hydrogen, and you get ethane. Keep baking off hydrogens you get ethylene, volatile liquids, oils, paraffins and all matter of abiotic "organics" hydrocarbons, and eventually even coal...