How did petroleum form?

The opinion that has prevailed among scientists since the 1870's is called the biogenic theory. This "holds that biological debris¹ buried in sediments² decays³ into oil and natural gas in the long course of time and that this petroleum then becomes

concentrated in the pore⁴ space of sedimentary rocks in the uppermost layers of the Earth's crust." This process then produc­es petroleum, whose main components are hy­drocarbons – that is, hydrogen⁵ and carbon,⁶ However, since the 1970s this theory has at times been challenged by some scientists.

In the August 20, 2002, issue of Proceedings of the National Academy of Sciences, the arti­cle "The Genesis of Hydrocarbons and the Ori­gin of Petroleum" was published. The authors argue that the origin of natural petroleum must occur at depths that are "well into the mantle⁷ of the Earth" and not at the much shallower depths generally accepted. Physicist Thomas Gold has suggested some con­troversial theories and explains his reasons in detail in his book “The Deep Hot Biosphere – The Myth of Fossil Fuels”. He writes: "The theo­ry of the biological origin of hydrocarbons was so favoured in the United States and in much of Europe that it effectively shut out work on the opposing viewpoint. This was not the case in the countries of the former Soviet Union.” That was “probably because the revered Russian chemist Mendeleyev had supported the abiogenic (not biological) view. The arguments he presented are even stronger today, given the greatly expanded information we now have.” What is the abiogenic view?

Gold states: "The abiogenic theory holds that hydrocarbons were a component of the material that formed the earth, through accretion of sol­ids,⁸ some 4.5 milliard years ago." According to this theory, the elements of petroleum have been deep in the earth since the earth's formation.

¹ debris - (зд.) останки;

² sediment – осадочная порода;

³ decay - разлагаться;

⁴ pore - пустоты (в породе);

⁵ hydrogen - водород;

⁶ carbon - углерод;

⁷ mantle -мантия;

⁸ accretion of solids -(геол.) аккреция, нанос пород.

You are a Professor of chemistry. Tell your students about:

a) biogenic theory of the oil formation

b) abiogenic theory of the oil formation

Which theory would you think to be more reasonable?