Oil was once organic plant life. Just like coal. Once it is gone, it is gone.
"Abiotic oil" is one of the stupidest claims ever made. It was stupid when the Soviet Union invented the concept, and it's stupid now that the 6,000 year creationist cretins in the US use it.
Oil is finite. And half the world's oil has already been used. Get used to the idea of oil costing $200 per barrel.
If it comes from old plants and animals, then it would seem infinite.
Things are constantly becoming "old". Things are older as time goes on. So if it's made of old plant/animal matter, and things are always becoming considered "old", it's an "infinite" resource.
At current consumption, viable oil reserves will be exhausted in less than 50 years. It is not a sustainable resource.
From what I've read it appears there are several ways oil is created, but the most common large deposits we've been using are mostly old life. They tend to provide the best quality oil. It's possible to create synthetic oil in the lab and do so even cheaply but, again, its just not the same quality.
I truly feel no one knows the answer to this question.