Oil formation

In 1906, G. P. Mikhailovsky dealt with issues of the origin of Caucasian oil ^[2] , he defended the following main provisions ^[3] :

1. the initial organic substance for the oil was mixed (plant and animal);
2. his burial occurred in clay silts (but not in sandy sediments, as many geologists of those years believed);
3. the initial stage of transformation of maternal organic matter is due to the activity of bacteria, both aerobic and anaerobic; subsequent stages of the process are physicochemical, in which the main acting factors are pressure and temperature;
4. primary oil is born diffusely dispersed;
5. the accumulation of oil in the reservoirs is a secondary process;
6. the formation of oil deposits is the result of tectonic disturbances, in particular the consequence of the formation of anticlines .

He is considered one of the founders of the concept of oil source formations . Many similar Soviet and foreign scientists began to develop completely similar thoughts 15-25 years later than Mikhailovsky. Moreover, the general picture painted by G.P. Mikhailovsky was shown in the book "The Doctrine of Oil" ( Gubkin , 1932).

Two concepts have become widespread: organic (biogenic) and inorganic ( abiogenic ) origin of oil, with most of the scientific evidence in favor of biogenic origin (ie from the remains of ancient living organisms); oil exploration and production are carried out in accordance with the predictions of biogenic theory ^[4] .

• According to Yu. I. Pikovsky, there is no consensus on the origin of oil ^[5] .
• According to M. V. Rodkin, the effective conversion of nutrients to oil occurs under the influence of factors traditionally proposed by proponents of abiogenic hypotheses ^{[6] [ specify ]} .

Biogenic origin

During fossilization (burial) of organic matter ( zooplankton and algae residues) of the sapropel type , its gradual transformation occurs in water-sedimentary deposits. In conditions of ancient warm seas rich in nutrients, organic matter entered the bottom faster than it could decompose. When sediments are immersed to a depth of 3-6 km with an increase in temperature above 50 ° C, organic matter ( kerogen ) undergoes thermal and thermocatalytic decomposition of polymer-lipoid and other components, which can form liquid hydrocarbons, including low molecular weight (C ₅ -C ₁₅ ). Liquid petroleum hydrocarbons have increased mobility, and micro-oil can migrate from source rocks through reservoirs, collecting in traps. As a result of the movement of the continents, some traps may remain on the territory of the continents or the shelf , however, most of the organic sediments during the movement of the oceanic crust fall into the subduction zone.

When studying the molecular composition of hydrocarbons, chemofossilia , molecular structures of a biogenic nature, were discovered.

The process of oil formation took from 50 to 350 million years ^[7] .

The following stages of oil formation are distinguished:

• Sedimentation - the remains of living organisms fall to the bottom of water basins;
• biochemical phase of oil formation ( diagenesis ) - processes of compaction, dehydration and biochemical processes in conditions of limited access of oxygen;
• protocatagenesis - lowering the reservoir of organic residues to depths of up to 1.5 - 2 km with a slow rise in temperature and pressure;
• mesocatagenesis (the main phase of oil formation (GFN)) - lowering the reservoir of organic residues to a depth of 3 to 4 km when the temperature rises to 150 ° C. In this case, organic substances undergo thermocatalytic degradation , resulting in the formation of bituminous substances , which make up the bulk of the micro-oil . Further, the oil is distilled off due to the pressure drop and the emigration of micro-oil to sand reservoirs, and traps through them;
• apocatagenesis of kerogen (the main phase of gas formation (HFG)) - lowering the reservoir of organic residues to a depth of more than 4.5 km when the temperature rises to 180-250 ° C. In this case, the organic matter loses the oil generating potential and realizes the methane generating potential.

Since the 1930s, I. M. Gubkin has been a supporter of biogenic oil production ^[8]

In the 1970s, the USSR officially supported the theory of the organic origin of oil ^[9] .

Abiogenic Origin

The abiogenic (inorganic) origin of oil is the theory of the primacy of oil deposits. There are several hypotheses on the inorganic origin of oil from inorganic matter at extra-deep depths under tremendous pressures and high temperatures from inorganic carbon and hydrogen and hydrocarbons common in space .

Abiogenic hypotheses of oil formation became popular in the Soviet Union in the middle of the 20th century ^{[10] [11]} .

Inorganic theories did not allow making effective forecasts for the discovery of new oil fields ^[12] .

• Bakirov A. A., Vassoevich N. B. , Weber V. V. et al. The Origin of Oil / Ed. M.F. Mirchinka. M .: Gostoptekhizdat, 1955.448 s.
• Weber VV The problem of oil formation in the light of paleogeography data of oil-bearing basins // The origin of oil and natural gas: current status of the issue. M .: TsIMTneft, 1947.S. 28-38.
• Weber V.V., Ginzburg-Karagicheva T. L., Glebovskaya E. A. et al. Accumulation and conversion of organic matter in modern marine sediments. M .: Gostoptekhizdat, 1956.343 s.
• Weber V.V. Diagenetic stage of oil and gas formation. M .: Nedra, 1978. 143 p.
• Weber V.V. Initial stages of oil formation // Geology of oil and gas. 1986. No. 5. P. 35-37.
• Weber V.V. Main ways of oil genesis. M .: Nauka, 1989.63 p.
• Speight JG An Introduction to Petroleum Technology, Economics, and Politics - Wiley-Scrivener, 2011, ISBN 978-1-118-01299-4 , pp. 35-35 "2.1 The formation of Oil", "2.2 Reservoirs"
• Kalinko M.K. Inorganic origin of oil in the light of modern data (critical analysis). M .: Nedra, 1968.338 s.
• Problems of the origin of oil and gas. Moscow: Science, 1994.

• Organic origins - Geochemistry Research, United States Geological Survey (USGS )
• Oil (TSB)
• A microprinciple of modern oil reserves , September 7, 2010. Translation of Broad W. , Tracing Oil Reserves to Their Tiny Origins , NYTimes, AUG. 2, 2010