On the possibility of fast modern generation of oil and gas

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

Back in 1993, Russian scientists proved that oil and gas are renewable resources. And you need to extract no more than is generated as a result of natural processes. Only then can the prey be considered non-barbaric.

It is generally accepted in some comparisons to use the image of two sides of the same medal. The comparison is figurative, but not entirely accurate, since the medal also has a rib that determines the thickness. Scientific concepts, if we compare them with a medal, have, in addition to their own scientific and applied aspects, one more - psychological, associated with overcoming the inertia of thinking and revising the opinion that had developed by that time about this phenomenon.

The psychological obstacle can be called the syndrome of scientific dogmatism, or the so-called "common sense". Overcoming this syndrome, which is a noticeable brake on scientific progress, consists in knowing the origins of its appearance.

The ideas about the slow formation and accumulation of oil and gas and, as a consequence, about the depletion and irreplaceability of hydrocarbon (HC) reserves in the Earth's interior appeared in the middle of the last century along with the rudiments of oil and gas geology. They were based on the speculative concept of oil generation as a process associated with the squeezing of water and hydrocarbons during immersion and the increasing compaction of sedimentary rocks with depth.

Slow subsidence and gradual heating, taking place over many millions of years, gave rise to the illusion of very slow oil and gas formation. It has become an axiom that the extremely low rate of formation of hydrocarbon deposits is incomparable with the rate of oil and gas extraction during field operation. Here, there was a substitution of ideas about the rates of chemical reactions during the destruction of organic matter (OM) and its transformation into mobile gas-liquid hydrocarbons, the rates of subsidence of sedimentary strata and their catagenetic transformation due to slow, mainly conductive, heating. The huge rates of chemical reactions have been replaced by the relatively low rates of evolution of sedimentary basins. It is this circumstance that underlies the concept of the duration of oil and gas formation, and, consequently, the exhaustion, irreplaceability of oil and gas reserves in the foreseeable future.

The views on slow oil formation received universal recognition and were used as the basis for both economic concepts and theories of oil and gas formation. Many researchers, when assessing the scale of hydrocarbon generation, introduce the concept of "geological time" into the calculation formulas as a factor. However, apparently, based on new data, these views should be discussed and revised [4, 9−11].

A certain departure from tradition can be seen already in the theory of the staging of oil formation and the idea of the main phase of oil formation (GEF), proposed in 1967 by NB Vassoevich [2]. Here, it is shown for the first time that the generation peak falls on a relatively narrow depth and, therefore, a time interval determined by the time the parent stratum is in the temperature zone of 60–150 ° C.

Further study of the manifestation of staging showed that the main waves of oil and gas formation break up into narrower peaks. So, S. G. Neruchev et al. Established several maxima for both the GFN zone and the GZG. The corresponding generation peaks correspond in power to intervals of only a few hundred meters. And this indicates a significant reduction in the duration of the generation of shock waves and, at the same time, a significant increase in its rate [6].

High rates of HC generation also follow from the modern model of this process. Oil and gas formation in the sedimentary basin is considered as a self-developing multistage chemical process, expressed by the alternation of decomposition (destruction) and synthesis reactions and proceeding under the action of both the "biological" (solar) energy stored by organic compounds and the energy of the endogenous heat of the Earth, and, as shown by the results of superdeep drilling, most of the heat enters the base of the lithosphere and moves in the lithosphere by convection. The share of heat associated with radioactive decay accounts for less than one third of its total amount [8]. It is believed that in zones of tectonic compression, the heat flow is about 40 mW / m², and in zones of tension its values reach 60−80 mW / m²… The maximum values are established in the mid-ocean rifts - 400-800 mW / m²… Low values observed in young depressions such as the South Caspian and the Black Sea are distorted due to ultra-high sedimentation rates (0.1 cm / year). In fact, they are also quite high (80-120 mW / m²) [8].

Decomposition of OM and synthesis of hydrocarbons as chemical reactions proceed extremely rapidly. The reactions of destruction and synthesis should be considered as revolutionary turning points leading to the appearance of oil and gas, followed by their concentration in the reservoir against the general background of slow evolutionary subsidence and heating of the sedimentary strata. This fact was convincingly confirmed by laboratory studies of kerogen pyrolysis.

Recently, to describe the rapidly occurring phenomena of the transformation of a substance from one state to another, the term "anastrophe", proposed by the Swedish chemist H. Balchevsky, has begun to be used. The formation of hydrocarbon compounds from decomposing organic matter, which occurs in a jump at a tremendous speed, should be classified as anastrophic.

The modern scenario of oil and gas formation is drawn as follows. The organic matter of the sedimentary strata of the subsiding basin undergoes a series of transformations. At the stage of sedimentogenesis and diagenesis, the main groups of biopolymers (fats, proteins, carbohydrates, lignin) decompose and various types of geopolymers accumulate in the sediment and create kerogen in sedimentary rocks. Simultaneously, there is a rapid synthesis (geoanastrophy) of hydrocarbon gases, which can accumulate under the first seals, create gas hydrate strata in the bottom layer or permafrost areas, and form natural gas outlets on the surface or at the bottom of reservoirs (Fig. 1).

Rice. 1. Scheme of gas hydrate formation in the Paramushir part of the Sea of Okhotsk (according to [5]): 1 - sedimentary layer; 2 - consolidated layers; 3 - forming gas hydrate layer; 4 - gas concentration zone; 5 - direction of gas migration; 6 - bottom gas outlets. Vertical scale in seconds

At the stage of catagenetic transformation of sedimentary rocks, thermodestruction of geopolymers and thermocatalytic anastrophy of petroleum hydrocarbons from oxygen-containing fragments of lipid and isoprenoid compounds released from kerogen forms of dispersed organic matter take place [31]. As a result, liquid and gas hydrocarbons are created, which form migrating hydrocarbon solutions, passing from the parent strata into reservoir horizons and fluid-conducting faults.

HC solutions that saturate natural reservoirs, either concentrate in their raised parts in the form of individual accumulations of oil and gas, or when moving upward along tectonic faults, they fall into zones of lower temperatures and pressures and there they form deposits of various types, or, with a high intensity of the process, they come out on the day surface in the form of natural oil and gas manifestations.

An analysis of the location of oil and gas fields in the CIS basins (Fig. 2) and the world unequivocally indicates that there is a global level of 1-3 km of concentration of oil and gas accumulations and about 90% of all hydrocarbon reserves are associated with it.

Rice. 2. Depth distribution of oil and gas reserves in the CIS basins (according to A. G. Gabrielyants, 1991)

while the sources of generation are located at depths from 2 to 10 km (Fig. 3).

Rice. 3. Typification of basins according to the ratio of the main zone of oil formation and the main interval of concentration of oil and gas deposits (according to A. A. Fayzulaev, 1992, with changes and additions)

Pool types: I- disunited; II - close; III - united. Pools name: 1 - South Caspian; 2 - Vienna; 3 - the Gulf of Mexico; 4 - Pannonian; 5 - West Siberian; 6 - Perm, 7 - Volga-Uralsky. Vertical zoning: 1 - upper transit area: 2 - the eye zone of oil accumulation: 3 - lower transit zone; 4 - GFN (oil generation centers); 5 - GFG (gas generation centers); 6 - direction of migration of hydrocarbons; 7 - the area reflecting the geological reserves of hydrocarbons or the number of deposits,%

The position of the generation centers is determined by the temperature regime of the basin, and the position of oil and gas deposits is primarily determined by the thermobaric conditions of condensation of hydrocarbon solutions and the loss of energy of migration movement. The first condition is individual for individual pools, the second is generally universal for all pools. Thus, in any basin, from the bottom up, several genetic zones of HC behavior are distinguished: the lower or main zone of HC generation and HC-solutions formation, the lower HC-solution transit zone, the main HC-solution accumulation zone in the reservoir and the upper HC-solution transit zone, and their exit to the day surface. In addition, in deep-water marine sedimentary basins and basins located in the subpolar regions, a zone of gas hydrates appears at the top of the basin.

The considered scenario of oil and gas formation makes it possible to quantify the rate of HC formation in oil and gas basins that are experiencing intense subsidence and, therefore, are under conditions of intensive modern HC formation. The most striking indicator of the intensity of oil and gas formation are natural oil and gas shows in modern sedimentation basins. Natural seepage of oil has been established in many parts of the world: off the coast of Australia, Alaska, Venezuela, Canada, Mexico, USA, in the Persian Gulf, the Caspian Sea, off the island. Trinidad. The total volumes of oil and gas production are significant. So, in the sea basin of Santa Barbara off the coast of California, up to 11 thousand l / s of oil comes from only one section of the bottom (up to 4 million tons / year). This source, operating for more than 10 thousand years, was discovered in 1793 by D. Vancouver [15]. Calculations carried out by FG Dadashev and others showed that in the area of the Apsheron Peninsula, billions of cubic meters of gas and several million tons of oil per year come out on the surface of the day. These are products of modern oil and gas formation, not trapped by traps and permeable, water-filled formations. Consequently, the expected scale of HC generation should be increased many times.

The enormous rates of gas formation are unambiguously evidenced by the thick strata of gas hydrates in the modern sediments of the World Ocean. More than 40 regions of gas hydration distribution have already been established, containing many trillions of cubic meters of gas. In the Sea of Okhotsk, A. M. Nadezhny and V. I. Bondarenko observed the formation of a gas hydrate layer with an area of 5000 m²containing 2 trillion m³ hydrocarbon gas [5]. If the age of the deposits is considered 1 million years, then the gas flow rate exceeds 2 million m³/ year [5]. Intense seepage occurs in the Bering Sea [14].

Observations at the fields of Western Siberia (Verkhnekolikeganskoye, Severo-Gubkinskoye, etc.) showed a change in the composition of oils from well to well, explained by HC inflow along hidden cracks and fractures (Fig. 4) from a deeper source of HC generation, which unambiguously indicates the presence of in the zones of hydrocarbon transit, faults and cracks of a hidden nature (ghost-faults), which, however, are quite well traced on time seismic lines.

Rice. 4. Model of the formation of an oil reservoir in the BP formation₁₀, Severo-Gubkinskoye field (Western Siberia)

I - profile section; II - generalized chromatograms of oil samples. Oil deposits: 1 - "primary"; 2 - "secondary" compositions; 3 - direction of motion of hydrocarbons from the generation source; 4 - number of wells; 5 - crack; 6 - chromatograms (a - n-alkanes, b - isoprenoid alkanes). WITH - the amount of carbon in the molecule

Oil samples from wells located in the zone of disturbances have a lower density, a higher yield of gasoline fractions and higher values of the pristane-phytane isoprenanes ratio than samples from the central part of the reservoir, which is in the zone of less influence of the ascending fluid flow and reflecting oils of earlier influx. The study of modern forms of hydrothermal and hydrocarbon seepage on the seabed allowed V. Ya. Trotsyuk to single them out into a special group of natural phenomena, which he called “structures of fluid breakthrough” [13].

The high rate of hydrocarbon formation is unambiguously evidenced by the existence of gigantic deposits of gas and oil, especially if they are confined to traps formed in the Quaternary.

This is also evidenced by the gigantic volumes of heavy oils in the Upper Cretaceous layers of the Athabasca field in Canada or in the Oligocene rocks of the Orinoco Basin of Venezuela. Elementary calculations show that 500 billion tons of heavy oil from Venezuela required 1.5 trillion tons of liquid hydrocarbons for their formation, and when the Oligocene lasted less than 30 million years, the hydrocarbon inflow rate should have exceeded 50 thousand tons / year. It has long been known that oil production was restored after a few years from abandoned wells at old fields in the Baku and Grozny regions. Moreover, there are active wells in the exhausted deposits of the Grozny fields of Starogroznenskoye, Oktyabrskoye, Malgobek, the total oil production of which has long exceeded the initial recoverable reserves.

The discovery of the so-called hydrothermal oils can serve as evidence of high rates of oil formation [7]. In a number of modern rift depressions of the World Ocean (the Gulf of California, etc.) in Quaternary sediments under the influence of high-temperature fluids, manifestations of liquid oil have been established, its age can be estimated from several years to 4000-5000 years [7]. But if hydrothermal oil is considered an analogue of a laboratory pyrolysis process, the rate should be estimated as the first figure.

Comparison with other natural fluid systems experiencing vertical movement can serve as indirect evidence of high rates of movement of hydrocarbon solutions. The enormous rates of the outpouring of magmatic and volcanogenic melts are quite obvious. For example, the modern eruption of Mount Etna occurs with a lava velocity of 100 m / h. It is interesting that during calm periods, up to 25 million tons of carbon dioxide seeps into the atmosphere from the surface of the volcano through hidden disturbances during one year. The outflow rate of high-temperature hydrothermal fluids of the mid-ocean ridges, which occurs for at least 20-30 thousand years, is 1-5 m³/With. The formation of sulfide deposits in the form of so-called "black smokers" is associated with these systems. Ore bodies are formed at a rate of 25 million tons / year, and the duration of the process itself is estimated at 1–100 years [1]. Of interest are the constructions of OG Sorokhtin, who believes that kimberlite melts move along lithospheric cracks at a speed of 30–50 m / s [11]. This allows the melt to overcome rocks of the continental crust and mantle up to 250 km thick in just 1.5–2 hours [12].

The above examples indicate, firstly, significant rates of not only the generation of hydrocarbons, but also the movement of their solutions through the transit zones in the earth's crust along the systems of hidden cracks and disturbances in it. Secondly, the need to distinguish between very slow rates of subsidence of sedimentary layers (m / mln years), slow heating rates (from 1 ° С / year to 1 ° С / mln years) and, conversely, very fast rates of the hydrocarbon generation process itself and moving them from the source of generation to traps in natural reservoirs or to the day surface of the basin. Third, the very process of transformation of OM into HC, which has a pulsating character, also develops for a rather long time over millions of years.

All of the above, if it turns out to be true, will require a radical revision of the principles of development of oil and gas fields located in modern, intensively generating hydrocarbon basins. Based on the rates of generation and the number of fields, the development of the latter should be planned in such a way that the rate of withdrawal is in a certain ratio with the rate of HC input from the sources of generation. Under this condition, some deposits will determine the level of production, while others will be on natural replenishment of their reserves. Thus, many oil-producing regions will operate for hundreds of years, providing a stable and balanced production of hydrocarbons. This principle, similar to the principle of forest land exploitation, should become the most important in the development of oil and gas geology in the coming years

Oil and gas are renewable natural resources and their development should be built on the basis of a scientifically grounded balance of hydrocarbon generation volumes and the possibility of withdrawal during field operation

See also: Silent sensation: oil is synthesized by itself in spent fields

Boris Alexandrovich Sokolov (1930-2004) - Corresponding Member of the Russian Academy of Sciences, Doctor of Geological and Mineralogical Sciences, Professor, Head of the Department of Geology and Geochemistry of Fossil Fuels, Dean of the Faculty of Geology (1992-2002) Moscow State University named after MV Lomonosov, laureate of the IM Gubkin Prize (2004) for a series of works "Creation of an evolutionary-geodynamic concept of a fluid-dynamic model of oil formation and classification of oil and gas basins on a geodynamic basis."

Guseva Antonina Nikolaevna (1918−2014) - candidate of chemical sciences, petroleum geochemist, employee of the Department of Geology and Geochemistry of Fossil Fuels of the Geological Faculty of Moscow State University. M. V. Lomonosov.

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