Abiogenic Petroleum Origin
The abiogenic hypothesis argues that petroleum was formed from deep carbon deposits, perhaps dating to the formation of the Earth. Supporters of the abiogenic hypothesis suggest that a great deal more petroleum exists on Earth than commonly thought, and that petroleum may originate from carbon-bearing fluids that migrate upward from the mantle. The presence of methane on Saturn's moon Titan and in the atmospheres of Jupiter, Saturn, Uranus and Neptune is cited[1] as evidence of the formation of hydrocarbons without biology.[2]The linked article in Wikipedia has perhaps the most balanced review of this topic. But beware, there is a lot of wack-job opinion masquerading as fact on this topic.