Two recent sources of evidence suggest there may be a non-biological origin for petroleum. One concerns this planet, Earth and the other the Saturnian moon, Titan. One study from the University of Washington has shown that hydrocarbons enriched in the isotope C-13 bubble-up from the ocean floor in the hypothermal "Lost City" field along the mid-Atlantic ridge in the middle of the Atlantic Ocean and 2,100 feet below the ocean surface. An excess of C-13 is believed to signify an abiotic origin, while a decrease in C-13 (compared to a mean natural isotopic abundance of around 1% for C-13, and 99% C-12) is associated with a biotic (biological) source. On Titan, there is evidence for the presence of more hydrocarbons than exist on Earth, where it is thought too cold for biological life to exist, and which thus cannot be invoked to explain their presence.
There are two theories for the origin of petroleum, the biotic and abiotic. The former is held mainly by geologists in the West and the latter is also known as the Russian/Ukrainan theory of Petroleum, which is where belief in it preponderates. The biotic theory holds that petroleum is the result of cooking animal and plant remains in near-surface regions of the Earth over millennia, while the abiotic theory is that petroleum is produced by the natural forces of geology, as a result of chemical processes within the Earth. One of the main proponents of the abiotic theory was the great Russian chemist, Mendeleev who devised the Periodic table of the Chemical Elements, and thought that petroleum was formed by the reaction of water with metal, principally iron, carbides deep within the Earth. Indeed, the renowned French chemist, Bertholet produced a hydrocarbon oil artificially by the action of acids on steel - which contains iron carbides.
In previous times, the matter would have been a mere scientific curiosity, but as conventional supplies of oil are believed to be about to peak and then run into short supply - the "Oil Dearth Era" - the prospect that more oil will be continually produced by the Earth itself, is very exciting and possibly reassuring. Perhaps Nature might snatch us from the jaws of a hungry energy crunch. However, it is the rate of recovery of oil that will decide this, and for example, if oil cannot be recovered at a rate equivalent to 30 billion barrels a year, as humanity uses presently, even if the abiotic theory is true, the facts of it will not be able to save us from the encroaching gap between supply and demand for oil. Future generations might be "blessed" as we were with a cornucopia of oil, but our own salvation and that of more immediate generations will depend on finding alternative ways to live which use far less oil.
Hydrocarbons may be classified as "energy minima", meaning they are stable molecules which might result from different kinds of processes - both biotic and abiotic. Thomas Gold thought that bacteria present at depths of down to ca 8 km could feed on hydrocarbons emanating from greater depth. He also proposed that natural gas and indeed coal, were created continually within the earth by intrinsic geochemical processes. I have heard that the Russians are sufficiently confident about the abiotic theory that they are undertaking deep-drilling projects to access petroleum that is present at depths of more than 3 km, and it is said that they are thus able to recover substantial quantities of the material in this way. If an alternative source of petroleum can be recovered in this way, and rapidly enough, both the event of peak oil might be staved-off, and considerable power placed in the hands of whoever can access it.
 "Discovery backs theory oil not 'fossil fuel'. http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=59991
 "Titan's Mysterious Methane Comes from Inside, Not the Surface." http://www.spaceref.com/news/viewpr.html?pid=18410
 "New tests could further undermine 'fossil fuels'. http://royaldutchshellplc.com/2008/02/04/
 "Results show fossil fuels are generated in ocean floor." http://appalachianforums.com/dcdb.pl?noframes;page=4;read=149000
 "New data: Maybe oil isn't from dead dinos." http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=56480