The real turning point in humanity's relationship with this viscous substance came with the beginning of industrial production nearly two centuries ago, sparking scientists' curiosity about the origin of this dark treasure. Since then, the question of its origin has preoccupied geologists and chemists, with numerous theories and hypotheses reflecting the mystery surrounding this issue. In 1912 alone, the scientist Hans Hoover compiled more than one hundred different hypotheses attempting to explain the formation of oil, confirming that the matter remains unresolved and continues to be the subject of extensive scientific research and debate to this day.
Throughout history, prevailing ideas about the origin of oil have evolved. School geography curricula once linked oil formation to the remains of giant dinosaurs, but this idea has since been replaced by the more likely explanation of smaller organisms—zoonophores, phytoplankton, and algae—as the organic source. A remarkable discovery in 2021 further strengthened the role of algae: a strain of round planktonic algae was found in the Chukchi Sea in the Arctic, capable of producing oil from water and carbon dioxide. These organisms possess a biological wisdom: they produce oil because its lower density than water allows them to remain floating on the surface. However, this doesn't solve the whole mystery. The sheer volume of oil discovered and extracted worldwide raises a fundamental question: can all these vast quantities truly be the product of the decomposition of microorganisms? Especially since no one has yet accurately compared the size of oil reserves with the necessary volume of biological waste in ancient sedimentary reservoirs. Even more strangely, studies indicate that organic matter in those ancient times did not decompose as expected, perhaps due to the absence of microorganisms specialized in decomposition at that time, adding another layer of complexity to the traditional theory.
Scientific theories today regarding the origin of oil are concentrated in two main schools: the organic or biological theory and the inorganic or organic theory. The organic theory, which is more widely accepted in traditional scientific circles, posits that oil was formed from the remains of living organisms, primarily plankton and algae, that inhabited ancient seas and oceans. After their death, their remains accumulated on the seabed in oxygen-poor environments, where they were partially decomposed by anaerobic bacteria. This resulted in the formation of a carbon-rich solid called kerogen, which was buried under layers of sediment. With increasing depth, it was subjected to immense pressure and high temperatures, transforming over millions of years into liquid and gaseous hydrocarbons—that is, oil and natural gas.
Proponents of this theory base their arguments on strong evidence, most notably the presence of "biomarkers" in oil—complex organic molecules that could only have a biological origin. Furthermore, most commercial oil fields lie in sedimentary rocks that were once rich marine environments. Additionally, the ratio of carbon isotopes in oil matches that of living organisms and differs from that of inorganic carbon
The inorganic theory posits that oil originated deep within the Earth, in the mantle or crust, through purely geochemical processes, devoid of any biological origin. These processes occur under extremely high temperatures and pressures, leading to the reaction of primary carbon and hydrogen compounds to form hydrocarbons. Proponents of this hypothesis cite the presence of oil in crystalline igneous or metamorphic rocks unrelated to organic deposits, as well as its occurrence near areas of volcanic and tectonic activity. Furthermore, some laboratory experiments have demonstrated the possibility of synthesizing heavy hydrocarbons similar to oil by simulating the harsh conditions found deep within the Earth
This view is supported by field observations, such as the replenishment of some depleted oil fields, as occurred in the Caucasus, suggesting the possibility of new oil flows from untapped depths. However, the inorganic theory remains unable to explain the presence of biosignatures, nor does it offer a convincing explanation for the specific geographic and stratigraphic distribution of most oil reservoirs, which the organic theory better explains through the study of sedimentary layers and faults.
In fact, the truth may not be confined to a single theory. A growing number of scientists are leaning toward the idea of multiple pathways, or the "mixed" theory, which accepts contributions from both organic and inorganic sources in the formation of oil. Deep underground processes may have provided primary hydrocarbons or contributed to the acceleration and transformation of buried organic matter. This approach aligns with the complexity of geological systems and the vastness of the Earth
Looking to the future, geologists like the Russian academician Alexander Lobosev assure us that the Earth's hydrocarbon reserves remain enormous. In addition to conventional reserves, there are deep wells yet to be drilled, and vast unexplored areas, such as those deep in Siberia and the Arctic. Lobosev notes that average extraction from existing fields is only 30 to 40 percent of the oil present in the reservoir, and that the remaining percentage awaits advanced technologies to make its extraction economically viable.
This academic concludes the optimistic picture with a philosophical vision, stressing that oil, like everything in this world, is limited, but its depletion, which is linked to major geological transformations of the earth, is something that will happen billions of years from now, not in the near future as some believe
Thus, the origin of oil remains an open scientific story, combining traditional evidence with perplexing complexities. From the tar of ancient ships to the fuel of the industrial age and its future, this wondrous substance compels us to contemplate the depths of the earth and the secrets of its distant history, and the possible collaboration between life and inanimate matter, between microscopic plankton and immense geological forces, to produce this liquid that has shaped the face of modern civilization
