The Cyril Fault is the most interesting evidence I have ever seen for abiogenic hydrocarbons. I have drilled across the fault very deep and seen changes in gas units through the fault gouge. The earth above the fault is clearly altered. Gold said is is the evidence of oxides of hydrocarbons.
Most geologists recoil at the thoughts of Gold. I don’t I’ve just drilled in to many settings and found hydrocarbons where there shouldn’t be. White Tiger Field off Vung Tau comes to mind.
Most faults allow for migration both up and down through them. Some faults act as lateral seals and some leak across the fault so that you need something impermeable across it to form a trap. Even though oil and gas mostly rise towards the surface due to buoyancy, they can migrate down as well.