We have all been taught the story. Oil and natural gas are "fossil fuels" because they are the transformed remains of ancient life. Marine organisms died, accumulated in sediments, were buried for millions of years and, under suitable conditions of pressure and temperature, became kerogen and eventually petroleum and natural gas.
It is one of those scientific explanations that has become so familiar that most people scarcely realise that it is a theory about the origin of petroleum rather than something anybody has directly watched happening over geological time.
There is, however, a competing school of thought. The abiogenic theory proposes that at least some hydrocarbons originate deep within the Earth through non-biological chemical processes and subsequently migrate upward through fractures and faults until they become trapped in geological reservoirs.
The controversial question is not whether abiotic hydrocarbons exist. They do. The serious dispute concerns scale. Are they geological curiosities contributing relatively little to the world's petroleum, as mainstream petroleum geology generally holds, or could deep-Earth hydrocarbon formation account for a much larger proportion of oil and gas deposits?
A recent TKP article by Peter F. Mayer (linked below), presents the strongest version of the latter argument, declaring the conventional biogenic theory scientifically untenable.
One argument concerns thermodynamics. Researchers associated with the Russian-Ukrainian abiogenic tradition have argued that complex hydrocarbons can form spontaneously under the enormous pressures and temperatures existing deep inside the Earth. Laboratory experiments have indeed demonstrated hydrocarbon formation under conditions intended to reproduce parts of the upper mantle. Vladimir Kutcherov and colleagues have argued that such experiments demonstrate a physically plausible pathway by which deep hydrocarbons could be generated without ancient plants or microorganisms.
This is important because it establishes that biology is not necessary for the existence of hydrocarbons. We already know that much from elsewhere in the Solar System. Methane exists on planets and moons where nobody seriously proposes that ancient forests were buried. Hydrocarbon chemistry is not inherently biological chemistry. Carbon and hydrogen can combine through abiotic processes under appropriate physical conditions.
But this does not by itself prove that the petroleum filling Saudi Arabian, American or Australian reservoirs was produced that way. Demonstrating that a process can occur is different from demonstrating that it produced a particular geological deposit.
Another challenge concerns petroleum found in crystalline basement rocks. The conventional image has oil accumulating in sedimentary formations associated with organic-rich source rocks. Yet petroleum and gas have also been discovered in fractured granite, metamorphic rocks and other crystalline basement formations.
Advocates of the deep-Earth theory ask an obvious question: if the rock itself never contained the biological material supposedly required to produce the petroleum, where did the oil come from?
Their answer is vertical migration. Hydrocarbons generated at great depth travel upward along fractures and faults until they encounter structures capable of trapping them. On this interpretation, the reservoir rock tells us where petroleum ended up, not necessarily where it originated.
That is an important distinction, although conventional petroleum geology has an answer as well. Oil can migrate considerable distances from organic-rich source rocks into completely different reservoir formations. Finding petroleum in granite therefore does not automatically establish that it came from the mantle. The critical question is whether the oil can be geochemically connected with nearby sedimentary source rocks.
Then there are very deep hydrocarbon deposits. Supporters of abiogenic petroleum point to oil and gas found at depths and temperatures beyond the traditional "oil window" normally associated with the conversion of organic material into petroleum. Kutcherov's review cites more than a thousand petroleum deposits at depths of roughly five to ten kilometres and argues that their existence presents difficulties for simplistic versions of the conventional model.
Perhaps the most intriguing claim involves apparently replenishing oil fields. Some producing fields have yielded more petroleum than earlier reservoir estimates suggested, or have shown evidence of hydrocarbons migrating into producing formations. Eugene Island in the Gulf of Mexico is frequently invoked in abiogenic-oil discussions. The abiogenic interpretation is that petroleum is migrating upward from deeper sources and replenishing the reservoir.
One of the strongest arguments for biological petroleum is the presence of biomarkers. Petroleum contains steranes, hopanes, porphyrins and other complicated organic compounds whose structures can be related to molecules associated with living organisms. Carbon-isotope ratios in many petroleum deposits also resemble those expected from biological carbon.
If you want to overthrow the conventional theory, this is the mountain that must be climbed. Abiogenic theorists reply that biomarkers may not necessarily prove that the petroleum itself originated biologically. Hydrocarbons migrating through kilometres of biologically active sediment could acquire biological material along the journey. Reservoirs themselves contain microbial communities. Finding biological molecules in petroleum might therefore demonstrate contact with life rather than prove that the bulk petroleum was manufactured from life.
The Earth may produce hydrocarbons in more than one way. Biological material unquestionably participates in hydrocarbon formation. Abiotic hydrocarbon synthesis also unquestionably occurs in nature. The unresolved issue is how quantitatively important the latter process is to commercially exploitable petroleum.
That question has enormous implications. If significant quantities of hydrocarbons are continuously generated deep within the Earth and migrate upward, petroleum would look less like a fixed inheritance of ancient biological material and more like part of an active planetary carbon system. That would not make individual oil fields inexhaustible. A reservoir can still be pumped faster than hydrocarbons enter it, just as a groundwater basin can be depleted despite continuing rainfall.
There is an excellent scientific test here. Do not settle the question politically. Drill, sample and measure. Examine helium isotopes and carbon isotopes. Analyse biomarkers. Compare petroleum with proposed source rocks. Investigate hydrocarbons emerging from mantle-associated geological environments. Determine migration pathways. Reproduce proposed reactions experimentally at realistic pressures, temperatures and chemical compositions. As covered in another blog piece the Russians are doing deep drilling now to test the theory:
https://www.youtube.com/watch?v=oBUKzeb-c8Y.
If the deep abiogenic theory identifies petroleum deposits in locations where the conventional model predicts they should not exist, and drilling repeatedly confirms those predictions, the theory deserves increasing weight.
Hydrocarbons are not intrinsically biological substances, abiotic hydrocarbon formation inside the Earth is physically possible, and experiments have demonstrated production of complex hydrocarbons under high-pressure conditions. The interesting scientific question is therefore no longer whether nature can manufacture hydrocarbons without fossils. It can. The question is how much of the oil beneath our feet it manufactured that way.
https://tkp.at/2026/08/10/fossile-brennstoffe-die-biogene-theorie-wissenschaftlich-am-ende-teil-1/