Home > Abiogenic petroleum origin
The theory of abiogenic petroleum origin states that petroleum is produced by non-biological processes deep in the Earth. This stands in contrast to the more widely held view that it is created from the fossilization of ancient organic matter. According to this theory, petroleum is formed by non-biological reactions deep in the Earth's crust. The constituent precursors of petroleum (mainly methane) are commonplace and it is possible that appropriate conditions exist for oil to be formed deep within the Earth.Although this theory has support by a large minority of geologists in Russia, where it was intensively developed in the 1950s and 1960s, it has only recently begun to receive attention in the West, where the biogenic theory is still believed by the vast majority of petroleum geologists. Although it was originally denied that abiogenic hydrocarbons exist at all on earth, this is now admitted by Western geologists. The orthodox position now is that while abiogenic hydrocarbons exist, they are not produced in commercially significant quantities, so that essentially all hydrocarbons that are extracted for use as fuel or raw materials are biogenic.
A variation of the abiogenic theory includes alteration by microbes similar to those which form the basis of the ecology around deep hydrothermal vents.
One prediction of this theory is that other planets of the Solar system or their moons have large petroleum oceans, either from hydrocarbons present at the formation of the Solar system, or subsequent chemical reactions.
That this theory is receiving increasing attention from Western geologists is indicated by the fact that the American Association of Petroleum Geologists scheduled a conference to meet in Vienna in July 2004 entitled "Origin of Petroleum—Biogenic and/or Abiogenic and Its Significance in Hydrocarbon Exploration and Production". The conference had to be canceled, however, due to financial considerations. Instead, AAPG will be holding a one-day session on the topic at the June 2005 annual meeting in Calgary, Alberta.
1 Comparison of theories
There are two theories on the origin of carbon fuels: the biogenic theory and the abiogenic theory. The two theories have been intensely debated since the 1860s, shortly after the discovery of widespread petroleum. There are several differences between the biogenic and abiogenic theories.
1.1 Raw material
- Biogenic: remnants of buried plant and animal life.
- Abiogenic: deep carbon deposits from when the planet formed or subducted material.
1.2 Events before conversion
- Biogenic: Large quantities of plant and animal life were buried. Sediments accumulating over the material slowly compressed it and covered it. At a depth of several hundred meters, catagenesis converts it to bitumens and kerogens.
- Abiogenic: At depths of hundreds of kilometers, carbon deposits are a mixture of hydrocarbon molecules which leak upward through the crust. Much of the material becomes methane.
1.3 Conversion to petroleum and methane
- Biogenic: Catagenesis occurs as the depth of burial increases and the heat and pressure breaks down kerogens to form petroleum.
- Significant advances in the understanding of chemical processes and organic reactions and improved knowledge about the effects of heating and pressurePressure (symbol: p is a measure of force per unit area. where p is the pressure F is the force A is the area Often F is taken to be the of the magnitude of the mean vector force normal to the surface of area A upon which it exerts; the "surface" not nece during burial and diagenesisIn geology, diagenesis refers to all the chemical, physical, and biological changes undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering). These changes happen at relative of organic sediments support biogenic processes.
- Abiogenic: When the material passes through temperatures at which extremophileAn extremophile is an organism, usually unicellular, which thrives in or requires "extreme" conditions. The definition of "extreme" is anthropocentric, of course. To the organism itself its environment is completely normal. Non-extremophilic organisms are microbes can survive some of it will be consumed and converted to heavier hydrocarbons.
