Everyone knows that oil is hydrocarbons. But where did it come from? Is it true that of the dinosaurs? And how many millions of years is the oil from which gasoline and hundreds of other important things around us are made today? We figure out what oil reserves lie in Russia and how many of them remain, why they have not yet been extracted, and also how this is related to creatures that lived millions of years ago.
Paleozoic oil: the oldest in Western Siberia
The oldest oil on Earth was formed three billion years ago, but in most parts of the planet the continental crust of such antiquity simply has not survived - almost all really old deposits have already sunk into the mantle.
Usually "Paleozoic" refers to the period in the history of the Earth, which lasted from 541 to 252 million years ago. In this era, life on the planet was abundant and exotic - by the standards of later eras, including ours. The key element of the fauna was trilobites - aquatic animals, in structure closer to very large insects than to the usual mollusks and crustaceans. These arthropods reached a meter in length and were the main aquatic animal until the Great Permian extinction, 252 million years ago, that is, just the entire Paleozoic era.
This article can be listened to as a podcast.
In geology, oceans, seas and other bodies of water are the most important component of all processes. It is there that all rocks are born that will contain oil in the future. It was there that ancient rivers from all continents carried tons of sedimentary material every day throughout the history of the planet. In the conditions of the ancient warm seas, rich in nutrients, the abundance and diversity of algae, zooplankton, various living ancient organisms and plants were enormous. More details about these geological processes can be seen in a video lecture by Alexander Butorin, an expert at the Gazprom Neft Science and Technology Center.
Oil of the "times of the trilobites" arose mainly not from them, but from the remains of algae. But next to this oil from the very beginning there were many hard rocks - formed from the shells of trilobites and molluscs. The fact is that, like modern lobsters, trilobites threw off their extremely dense shell, consisting of biocarbonates, annually, at each completion of the growth cycle.
Therefore, there are a lot of them, and these shells themselves are found in Russia today from St. Petersburg to stone pillars on the Lena, in Yakutia. This entire area was then a warm shallow sea water, and very actively accumulated organic remains - the present oil "Paleozoic". Carbonates were formed from them - very durable sedimentary rocks, whose density is higher than the reinforced concrete from which skyscrapers are built.
According to experts, the geological resources of the Paleozoic can reach 26 billion tons of hydrocarbons. For comparison, in 2019, Russia produced a total of 560 million tons. So why is the Paleozoic oil of Western Siberia still underground and so far practically not produced? Because it is located at a depth of 4.5 km and until now has practically not been studied, since oilmen had access to reserves closer to the Earth's surface.
The deposits of Paleozoic oil in Western Siberia are often found in strata lying at large angles to the plane - not horizontal, but also not completely vertical.
This means that they can not be developed with either vertical or horizontal wells - inevitably, you will have to "branch" the wellbore, just like branches branch off from a tree. It's good that this is technically possible. It is these wells that are remotely constructed from the GeoNavigator Drilling Control Center located in St. Petersburg. You can learn more about his work in this video.
Florida Grabovskaya, Project Manager "Paleozoic", Center for Industrial Integration "Gazpromneft-Technological Partnerships":
“The Paleozoic complex of rocks forms the foundation of the West Siberian plate, which is represented by mountain-folded structures buried under a thick stratum of sedimentary cover. The surface of the basement is complicated by a system of projections and depressions, intersected by numerous faults, and the strata of the basement rocks, in contrast to the sedimentary cover located above, are strongly dislocated and crumpled into folds of various shapes, with steep angles of incidence of layers."
Among the West Siberian assets of Gazprom Neft, there are several fields with proven prospective oil reserves in Paleozoic formations. For several years now, successful development of deposits in these rocks has been going on at the company's fields in the Tomsk region - Archinsky and Urmansky. It is planned to create an integrated technology for forecasting the oil-bearing capacity of sediments of the pre-Jurassic complex by 2022. In 2023, it will be tested at prospecting sites and its effectiveness will be assessed. In 2024–2025, it is planned to start replicating the new approach in new search zones.
What do experts think about the prospects for the development of these reserves? Read in the informational project "Paleozoic".
Domanik oil: the most unexplored
Domanik deposits come to the surface in the Komi Republic on the Domanik stream (it is from this stream that they got their name), although at a depth they are located almost throughout the Volga-Ural and Timan-Pechora basins. The deposits appeared in the Upper Devonian - 383–359 million years ago. They were formed in sea conditions. And the land in the Upper Devonian - part of these lands was not then covered with water - was already inhabited by the first amphibians.
By the way, it was in the Komi Republic in 2019 that the oldest known quadruped vertebrate - permastega - was found. It lived 372 million years ago in the Upper Devonian. Then, not only she lived in the local warm swamps, but also sea scorpions of huge sizes - up to a couple of meters in length. Unlike modern scorpions, they were not believed to be venomous, and the victims were killed with a serrated tail with a long, sharp spike at the end.
At that time, insects of various shapes and sizes lived on this territory in shallow water and swamps, and in addition, there were also giant predatory centipedes. Unlike modern specimens (small, albeit poisonous), they reached several meters in length and were truly dangerous even for the largest animals of that time.
Domanic rocks contain dense skeletons of mollusks, fish, fragments of algae and bitumen, and very small unbound pores can contain oil or gas, which formed in situ from organic matter, mainly algae. Domanica oil is often green, most likely due to the presence of chlorophyll
The host rocks contain not only carbonates, but also silica - forms of the outer skeleton of ancient tentaculite and radiolarian shells. Domanik reserves can be found at depths from 1350 to 3550 meters, which is about six Ostankino TV towers down.
According to experts, the geological resources of the Domanik deposits contain from 60 billion to a whopping 200 billion tons of hydrocarbons. So why hasn't anyone else won such a huge prize?
It's all about the geological structure of the Domanik rocks. The permeability of these rocks, that is, the ability to transmit oil or gas, is very low - less than 0.01 millidarci. For comparison: traditional oil fields can have rocks with a permeability of tens of millidarcy, which is several orders of magnitude greater. That is, oil is literally trapped in super dense rocks. We talked about permeability in detail in our article about stereotypes related to oil.
What other difficulties are there? For example, Domanik reserves are not one layer, but a whole set of small areas located one above the other at different depths. And to get oil out of them, you need to collect them all somehow. Standard methods are not suitable for such a task.
There is good news, too. All these reserves are distributed in the Volga-Ural and Timan-Pechora oil and gas provinces, where there is already a developed infrastructure for oil production and transportation. In addition, these territories have a milder climate than in Western Siberia, and field work can be carried out almost all year round.
Julia Zagranovskaya, Reserve Assessment Expert at the Gazprom Neft Science and Technology Center:
“Although Domanik deposits are widespread over a large territory of the Volga-Ural and Timan-Pechora oil and gas provinces, most often they remained unexplored. Previously, rock samples (cores) were not purposefully taken from these deposits, since it was believed that we would not find large accumulations of mobile hydrocarbons in the source rocks. Geochemical and petrophysical studies are very important for the study of Domanik deposits. The structure of the pore space has not yet been studied in detail. To date, 240 meters of core have already been taken from the Domanik sediments, as a result of studying which we will get answers to many questions."
You can learn about what a core is and how it helps oilmen in research in a video lecture by Oksana Melnikova, an expert at the Gazprom Neft Science and Technology Center.
Gazprom Neft has been studying Domanik reserves since 2018 at two license areas in the Orenburg Region - Savitsky and Pokhvistnevsky. In 2020, the company drilled the first prospecting and appraisal well in the Savitsky license area, and also completed seismic exploration there. All the information collected will help oilmen to more accurately assess the prospects for Domanik oil. Technologies for the profitable development of these reserves are planned to be created by 2027.
More information about Domanik oil and other complex reserves can be found here
Achimov strata: oil from the depths of ancient seas
The Achimov strata is located in Western Siberia in a huge area of 920 thousand km2. These are practically two territories in Spain or four in Great Britain.
Its reserves were formed at the beginning of the Cretaceous period, about 145 million years ago. It was then that the continents began to take on the outlines we were accustomed to. The supercontinent Pangea split into Laurasia and Gondwana, which also began to split into smaller parts. This process significantly affected the climate, leading to a rise in ocean levels. According to scientists, then it was as much as 200 meters higher than it is now.
Pangea
At that time, the Earth was dominated by dinosaurs and gymnosperms. True, the widespread phrase "oil is the remains of dinosaurs" is not entirely true here, as, in fact, for other fields. In the planetary biomass, all vertebrates taken together occupy no more than a percent, and the situation was exactly the same then. More than 90% of all biomass is accounted for by plants - and it was they that made up the vast majority of hydrocarbons, even in the Cretaceous period.
Where did so much oil come from in Western Siberia? The fact is that just in the Cretaceous period, almost throughout this territory there was a sea that accumulated organic matter for millions of years. It is these reserves that have given us today more than 800 oil and natural gas fields in Western Siberia. But not all oil reserves in this area are equally good for development.
Most of the studied deposits in Western Siberia were formed in the relatively shallow waters of the ancient sea. But the Achimov strata is not one of them.
Its deposits were formed from sedimentary rocks that "rolled" from the shallow shelf to the very depths. During this sliding, sedimentary rocks were repeatedly mixed and interbedded. Therefore, the result was not traditional homogeneous hydrocarbon deposits, but separate oil "fragments" scattered at a depth of 1500 to 4000 meters. These cannot be assembled not only with a vertical well, but even with a high-tech horizontal one.
And there really is something to collect. The resource potential of the Achimov strata of the West Siberian oil and gas basin is up to 66 billion tons of hydrocarbons.
In addition to heterogeneity, the Achimov reservoirs have one more feature - very high pressure. You should not try to extract such oil with conventional equipment, because it simply cannot withstand a whopping 600 atmospheres. This is about 300 times more than the pressure in a car tire, and even at such values it ruptures methane cylinders. Therefore, oilmen require ultra-reliable equipment and technologies to work with such reserves.
Azamat Timirgalin, expert of the Gazprom Neft Science and Technology Center:
“If you understand why there is such a high pressure in the Achimov reservoirs, then there are two main reasons. The first is the great depth of the Achimovka. There is a normal gradient of reservoir pressure change - approximately every 10 meters, the pressure increases by 1 atmosphere and, for example, at a depth of 4000 meters, it will be about 400 atmospheres.
The second reason is the abnormal pressure behavior in the north of Western Siberia. Because of this, at a depth of 4000 meters, the pressure is higher, reaching 600 atmospheres. The reasons for the abnormally high reservoir pressure are not fully understood, but there are some hypotheses - this is due to the compaction of clay deposits, the transformation of rocks and substances contained in them under the influence of high pressures and temperatures, and so on. In addition, the Achimov strata has a special structure of deposits, which contributes to the retention of excess pressure. Its reserves are in isolated lenses, similar to a sealed vessel."
Finding technologies for the profitable development of Achimov oil is a difficult task. To solve this problem, Gazprom Neft opened 5 years ago the Bolshaya Achimovka competence center, where several dozen technological projects are being implemented. Including in 2018, the world's first digital model of this type of reserves was created, in fact - a digital twin of a territory of more than 1.5 million square meters. km. This required an analysis of the industry's largest array of geological information. The digital model is a detailed model of several regions, consisting of more than 150 maps, which takes into account the geological data of almost 4 thousand wells. Such a virtual map will help oilmen identify the most promising zones for further study and development of the Achimov strata.
Gazprom Neft is pinning great hopes on the Achim technology center that is being created in the Yamalo-Nenets Autonomous Okrug. It is planned that it will become an industry-wide platform for combining the resources and competencies of the state, oilfield service companies, the scientific community and business. All with the same big goal - to jointly find tools for commercially effective access to the Achimov reserves.
More interesting information, infographics and expert opinions on the prospects for the development of Achimov oil can be found in the special projects Achimov Horizons and Achimovka. Oil of the future”.
Bazhenov Formation: Oil of the Dinosaur Age
The Bazhenov Formation is a fairly thin layer of sedimentary rocks spread over a million square kilometers in Western Siberia. Depending on the location, its thickness varies and averages about 30 meters. It is also the world's largest source of "hard" oil.
The Bazhenov Formation was formed in a deep sea basin in the late Jurassic and early Cretaceous periods about 145 million years ago. What is its difference from the Achimov strata, which we talked about above?
First, the Bazhenov Formation was formed from deep sea silt, and the Achimovka - from sandy-argillaceous deposits, which were carried to a depth from the shallow shelf. The Achimovskaya strata, in fact, are traditional layers of a more complex structure with low porosity and permeability, the deposits in which are formed according to well-known laws. The Bazhenov Formation is something completely different, an unconventional natural reservoir, where light oil can be contained in practically impermeable rocks, and which cannot be described using established scientific approaches. Both types of complex reserves are located close to each other, within a few tens of meters.
Bazhen is formed by the remains of marine organisms (mainly plankton) and their waste products, which were not processed by bacteria, but buried under the overlying rocks. In the process of geological development, these organic remains first formed a solid organic matter - kerogen, which is a kind of coal. Then, when the deposits of the Bazhenov formation sank to a great depth, complex organic compounds of kerogen, hitting the conditions of high temperature and pressure, began to decompose into simpler hydrocarbon molecules. In other words, under the influence of high temperature and pressure, oil began to form from kerogen. Therefore, the Bazhenov Formation is referred to as oil source rocks.
The process of the transition of solid organic matter (kerogen) into liquid is accompanied by an increase in its volume, which causes an increase in reservoir pressure. Because of this, a micro fracture of the rock occurs, as a result of which the newly formed hydrocarbons first "saturate" the practically impermeable rocks of the Bazhenov Formation, and then along faults and other channels in the earth's crust migrate to other layers, forming deposits. Most scientists admit that the Bazhenov Formation is the main source of hydrocarbons in Western Siberia.
The deposits of the Bazhenov Formation accumulated very slowly, approximately 8 million years. During this time, many events took place, the life cycles of marine life, their species composition changed, even large volcanic eruptions took place. Each event manifested itself in the form of a separate thin layer, as a result of which the deposits of the Bazhenov formation acquired a shale character. Deep processes taking place in the depths left their imprints, which only complicated its already complex structure. Thus, the history of geological development has made a “layered cake” of the Bazhenov Formation, where clays can coexist with interlayers of silica, carbonate rocks, volcanic ash and other deposits.
The complex geological structure, the lack of a reliable scientific and methodological base and the presence of several possible sources of hydrocarbons (light oil and kerogen not yet converted into hydrocarbons) have become the reasons for high uncertainties in assessing the resource base of the Bazhenov formation. The range of estimates is so great that it makes sense to indicate only their range from 600 million to 175 billion tons of conventional oil equivalent. Each time it is necessary to clarify what kind of resource in what type of rocks is meant.
Technologies for the development of reserves of the Bazhenov formation
Bazhenov oil is very unpredictable. In some areas, during development, it itself beats with a fountain, while in others it cannot be obtained even with the use of the most modern technologies. For the first time, geologists received an oil gusher from the Bazhenov formation back in the early 1960s at the Salym field in the Khanty-Mansi Autonomous Okrug, but already in the mid-1970s it became clear that such a development of events was rather a rare exception than the rule. The main volume of Bazhenov oil is contained in very small pores, which practically do not communicate with each other, that is, the oil is literally squeezed in microscopic isolated rock cells.
Alexey Alekseev, expert at Gazpromneft Technological Partnerships:
“Oil from the Bazhenov formation is often called an analogue of American shale oil, which is not entirely true. It should be noted that the term “shale oil” itself is more commercial than geological, and is applied to oil produced from oil and gas source rocks, which include the Bazhenov Formation and all American “shale” formations. We can say that the production of shale oil in Western Siberia began in the 1970s, 30 years before the official start of its production in the United States."
The prospects for the Bazhenov Formation are gigantic. But for its cost-effective development, technologies are needed that must take into account its features. Large reserves of bazhen are located in already developed fields with a developed infrastructure, and there is no need to build everything from scratch. And the oil itself is of very high quality. It is light, low-sulfur and low-viscosity.
The Bazhenov Formation, like other sources of difficult oil, can give a second life to the oil-producing regions of Russia, where the production of traditional hydrocarbon reserves is declining. Therefore, one of the key goals of Bazhen's development is to extend the life of existing fields by loading the already existing developed infrastructure. In addition, the request for the development of technologies for its development forms a high-tech industrial order from the creation of new materials to electronics and heavy engineering.
Gazprom Neft has been involved in bazheni since 2013. To research and test the methods of its development, the company is creating a technological testing ground in the Khanty-Mansi Autonomous Okrug, where it works together with partners. In 2017, the Bazhena development project was given the status of a national one. In 2020, due to the development of domestic technologies, Gazprom Neft reduced the cost of producing oil from the Bazhenov formation from 30 thousand rubles per ton at the start of the project to 13 thousand rubles per ton. Commercial oil production from the Bazhenov formation is expected to begin by 2025.
You can read more about promising technologies for bazhen here.
And here you can also go on a virtual journey to the layers of the Bazhenov formation!
Let's summarize. There is still a lot of oil in Russia. And not all of it is dinosaur. Oil industry workers are seriously targeting its gigantic, but hard-to-recover reserves, which in Russia today are two-thirds of all explored reserves in general. Simple calculations show that at their expense, oil production can be maintained at the current level for another century or two. "What happens next?" - the reader will ask. There is a high probability that new technologies will appear that will make it possible to get to new energy resources.
The partner material was prepared jointly with the Gazprom Neft Science and Technology Center.