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Federal State Budgetary Educational Institution of Higher Education

"Saratov State Technical University named after Yu.A. Gagarin"

Faculty of Ecology and Service

Department of Geoecology and Engineering Geology

Course work

Discipline: "Geology of Oil and Gas"

On the topic: “Natural gas hydrates”

Completed by: 3rd year student gr. B-NFGDz31

Kutvin M.S.

Head: Reshetnikov M.V.

Saratov 2016

• Introduction
• 1. History of the study of gas hydrates
• 2. Properties of hydrates
• 3. Structure of hydrates
• 4. Gas hydrates in nature
• 5. Thermobaric conditions for the existence of gas hydrates
• 6. Gases capable of forming a hydrate form in the Earth’s lithosphere
• 7. Scientific research on gas hydrates
• 8. New methods for monitoring the formation of gas hydrates
• 9. Geography of distribution of gas hydrates
• 10. Areas of modern exploration for hydrates
• 11. The problem of industrial development of the gas hydrate form of hydrocarbon accumulation
• 12. Methods for extracting methane from hydrates
• 13. Other possibilities for using gas hydrates
• Conclusion
• Bibliography

Introduction

Hydrocarbons are special compounds of the widespread elements hydrogen and carbon. These natural compounds have been mined and used for thousands of years: in the construction of roads and buildings as a binding material, in the construction and manufacture of waterproof ship hulls and baskets, in painting, to create mosaics, for cooking and lighting. At first they were mined from rare outcrops, and then from wells. Over the past two centuries, oil and gas production has reached unprecedented levels. Now oil and gas are sources of energy for almost all types of human activity.

Natural gas hydrates are a special combination of two widely occurring substances, water and natural gas. If these substances come into contact at high pressure and low temperature, a solid mass similar to ice is formed. Huge volumes of sediments in the near-bottom layers of the ocean floor and in the polar regions are found in thermobaric conditions that allow the formation of hydrates.

Synonyms for the term hydrates are gas hydrates, methane hydrates or clathrates (from the Greek “framework”). The main structural element of hydrates is a crystalline cell of water molecules, inside which a gas molecule is located. The cells form a dense crystal lattice. The structure of hydrates is similar to the structure of ice, but differs from the latter in that the gas molecules are located inside the crystalline cells, and not between them. Externally, hydrates look like ice, although they are not often seen. However, they behave very differently from ice. If you put a match to them, they light up.

Someday, perhaps as early as the 21st century, traditional hydrocarbon reserves will no longer be able to supply energy to a growing economy and population. Then their place can be taken by so-called unconventional hydrocarbon reserves in the form of gas hydrates.

hydrate gas hydrocarbon methane

1. History of the study of gas hydrates

The first publication related to gas hydrates dates back to 1811, when the English chemist H. Davy, passing chlorine through water at atmospheric pressure and temperatures close to 0 ° C, obtained a yellowish precipitate in a glass flask - chlorine hydrate. The instability of the resulting compound and the level of instrumental research in those years did not allow him to study its properties in detail.

In 1823, Faraday carried out the first analyzes of the composition of chlorine hydrate, and in 1884, Roseboom proposed the formula for the composition of chlorine hydrate 8H 2 0-C1 2 . Between the twenties and eighties of the last century, almost no research was carried out on gas hydrates. Gas hydrate compounds were forgotten for many decades, and only in the eighties of the last century the second stage of studying gas hydrates began. Over the course of five decades, hydrates of most individual gases and some mixtures were obtained. During this period, the dependence of hydrate formation on pressure and temperature was studied, the composition of hydrates was approximately determined, and phase diagrams were constructed. The results of experimental studies were processed taking into account the achievements of thermodynamics of that time. However, all studies of gas hydrates carried out over 120 years, until the early thirties of the 20th century, were purely academic. Gas hydrates were not used in industry, they did not interfere with the technological processes of that time and did not find practical application. In the thirties, the rapidly developing gas production industry set researchers the task of seriously studying gas hydrates, primarily with the aim of developing methods for preventing their formation and accumulation in pipelines and apparatus during gas production and transportation.

During this period, Hammerschmidt’s work was published, which showed that complications in gas pipelines during the cold season are not associated with the freezing of water, as was assumed, but with the formation of hydrates of transported gases.

The third stage of research into gas hydrates has begun. The period of applied study of gas hydrates lasted more than 20 years. During this period, almost all known methods of combating hydrates were developed. In recent decades, research has been carried out on some of the properties of gas hydrates using modern instrumental methods, serious theoretical research has been developed, as a result of which not only methods of combating hydrates have been improved, but also methods have been developed for their practical use in various technological processes.

A special place in the study of hydrates is occupied by studies related to the discovery of gas hydrate deposits in the sedimentary cover of the earth's crust, made by a group of scientists: V. G. Vasiliev, Yu. F. Makogon, F. A. Trebin, A. A. Trofimuk and N. V. . Chersky.

In the 1940s, Soviet scientists hypothesized the presence of gas hydrate deposits in the permafrost zone (Strizhov, Mokhnatkin, Chersky). In the 1960s, they also discovered the first deposits of gas hydrates in the north of the USSR. At the same time, the possibility of the formation and existence of hydrates in natural conditions is confirmed in the laboratory (Makogon).

From this point on, gas hydrates begin to be considered as a potential source of fuel. According to various estimates, hydrocarbon reserves in hydrates range from 1.8×10 14 to 7.6×10 18 m. Their wide distribution in the oceans and permafrost zone of continents, instability with increasing temperature and decreasing pressure are revealed.

In 1969, the development of the Messoyakha field in Siberia began, where it is believed that for the first time it was possible (by pure chance) to extract natural gas directly from hydrates (up to 36% of total production as of 1990).

2. Properties of hydrates

Natural gas hydrates are a metastable mineral, the formation and decomposition of which depends on temperature, pressure, chemical composition of gas and water, properties of the porous medium, etc.

The morphology of gas hydrates is very diverse. Currently, there are three main types of crystals:

· Massive crystals. They are formed due to the sorption of gas and water on the entire surface of a continuously growing crystal.

· Whisker crystals. They arise during tunnel sorption of molecules to the base of a growing crystal.

· Gel crystals. They are formed in a volume of water from gas dissolved in it when the conditions for hydrate formation are reached.

In rock layers, hydrates can be either distributed in the form of microscopic inclusions or form large particles, up to extended layers many meters thick.

Due to its clathrate structure, a unit volume of gas hydrate can contain up to 160-180 volumes of pure gas. The density of the hydrate is lower than the density of water and ice (for methane hydrate, about 900 kg/m³).

Fig.1. Phase diagram of methane hydrate

As the temperature increases and the pressure decreases, the hydrate decomposes into gas and water, absorbing a large amount of heat. The decomposition of hydrate in a closed volume or in a porous medium (natural conditions) leads to a significant increase in pressure.

Crystalline hydrates have high electrical resistance, conduct sound well, and are practically impenetrable to free water and gas molecules. They are characterized by abnormally low thermal conductivity (for methane hydrate at 273 K it is five times lower than that of ice).

To describe the thermodynamic properties of hydrates, the van der Waals (grandson)-Platteu theory is currently widely used. The main provisions of this theory:

· The host lattice does not deform depending on the degree of filling with guest molecules or their type.

· Each molecular cavity can contain no more than one guest molecule.

· The interaction of guest molecules is negligible.

· Statistical physics is applicable to the description.

Despite the successful description of thermodynamic characteristics, the van der Waals-Platteu theory contradicts the data of some experiments. In particular, it has been shown that guest molecules are capable of determining both the symmetry of the hydrate crystal lattice and the sequence of phase transitions of the hydrate. In addition, a strong effect of guests on host molecules was discovered, causing an increase in the most probable frequencies of natural vibrations.

3. Structure of hydrates

Fig. 2 Crystal modifications of gas hydrates

In the structure of gas hydrates, water molecules form an openwork frame (that is, a host lattice), in which there are cavities. It has been established that the frame cavities are usually 12- ("small" cavities), 14-, 16- and 20-sided ("large" cavities), slightly deformed relative to the ideal shape. These cavities can be occupied by gas molecules (“guest molecules”). Gas molecules are connected to the water framework by van der Waals bonds. In general, the composition of gas hydrates is described by the formula M n H 2 O, where M is a hydrate-forming gas molecule, n is the number of water molecules per included gas molecule, and n is a variable number depending on the type of hydrate-forming agent , pressure and temperature.

The cavities, combining with each other, form a continuous structure of various types. According to the accepted classification, they are called KS, TS, GS - cubic, tetragonal and hexagonal structure, respectively. In nature, the most common hydrates are types KS-I, KS-II, while the rest are metastable.

4. Gas hydrates in nature

Most natural gases (CH 4, C 2 H 6, C 3 H 8, CO 2, N 2, H 2 S, isobutane, etc.) form hydrates, which exist under certain thermobaric conditions. The area of ​​their existence is confined to sea bottom sediments and to areas of permafrost. The predominant natural gas hydrates are methane and carbon dioxide hydrates.

During gas production, hydrates can form in well bores, industrial communications and main gas pipelines. By depositing on the walls of pipes, hydrates sharply reduce their throughput. To combat the formation of hydrates in gas fields, various inhibitors are introduced into wells and pipelines (methyl alcohol, glycols, 30% CaCl 2 solution), and also maintain the gas flow temperature above the hydrate formation temperature using heaters, thermal insulation of pipelines and selection of operating modes, providing the maximum temperature of the gas flow. To prevent hydrate formation in main gas pipelines, gas drying is the most effective - cleaning gas from water vapor.

5. Thermobaric conditions for the existence of gas hydrates

Each individual component has a certain critical temperature, above which hydrates of this component do not form. This temperature is determined by the point of intersection of the equilibrium curve of hydrate formation with the vapor pressure curve of a given component. Methane and nitrogen, as well as inert gases, do not have a critical temperature for hydrate formation, since the line of elasticity of their vapors ends at the critical point of the gas before contacting the curve of elasticity of hydrate vapors.

Rice. 3. Conditions for the formation of hydrates by individual components of natural gas components

Figure 3 shows that hydrogen sulfide has the highest critical temperature, which can form hydrates at a temperature of 29.5 ° C and a pressure of 21 atm. With an increase in the content of so-called non-hydrate-forming components in the gas (N 2, H 2 He 2), the pressure of hydrate formation increases and if they are present in the mixture more than 50%, the formation of hydrates of this mixture becomes impossible.

6. Gases capable of forming a hydrate form in the Earth's lithosphere

Back in 1811, the English chemist H. Davy, passing chlorine through water at atmospheric pressure and temperatures close to 273 K, obtained a yellowish precipitate in a glass flask - chlorine hydrate. As it turns out, this is far from the only gas capable of forming compounds with water. All lower homologues of methane, carbon dioxide, nitrogen, hydrogen sulfide, etc. form hydrates, which are formed under certain thermobaric conditions.

Favorable conditions for the formation of natural gas hydrates exist both on land (mainly in areas of permafrost) and almost throughout the entire area of ​​the World Ocean, which is due to a favorable combination of temperatures and pressures for their formation.

In most cases, natural gas hydrates are represented by methane and carbon dioxide hydrates.

7. Scientific researchGAzovXhydrateov

In recent years, interest in the problem of gas hydrates throughout the world has increased significantly. The increase in research activity is explained by the following main factors:

· intensifying the search for alternative sources of hydrocarbon raw materials in countries that do not have energy resources, since gas hydrates are an unconventional source of hydrocarbon raw materials, pilot industrial development of which may begin in the coming years;

· the need to assess the role of gas hydrates in the near-surface layers of the geosphere, especially in connection with their possible impact on global climate change;

· studying the patterns of formation and decomposition of gas hydrates in the earth's crust in a general theoretical sense in order to substantiate the search and exploration of traditional hydrocarbon deposits (natural hydrate occurrences can serve as markers of deeper conventional oil and gas deposits);

· active development of hydrocarbon deposits located in difficult natural conditions (deep-sea shelf, polar regions), where the problem of man-made gas hydrates is becoming more acute;

· the feasibility of reducing operating costs to prevent hydrate formation in field gas production systems through the transition to energy-resource-saving and environmentally friendly technologies;

· the possibility of using gas hydrate technologies in the development, storage and transportation of natural gas.

In 1970, the scientific discovery “The property of natural gases to be in a solid state in the earth’s crust” was entered into the State Register of Discoveries of the USSR under No. 75 with priority from 1961, made by Russian scientists V. G. Vasiliev, Yu. F. Makogon, F. G. Trebin, A. A. Trofimuk and N. V. Chersky. After this, geological studies of gas hydrates received a serious impetus. First of all, graphic-analytical methods for identifying thermodynamic zones of stability of gas hydrates in the earth's crust (ZSH) were developed. It turned out that the hydrate stability zone (HSZ) of methane, the most common hydrocarbon gas in the earth’s crust, covers up to 20% of the land (in areas where the permafrost zone occurs) and up to 90% of the bottom of the oceans and seas.

These purely theoretical results intensified the search for hydrate-containing rocks in nature: the first successful results were obtained by VNIIGAZ employees A. G. Efremova and B. P. Zhizhchenko during bottom sampling in the deep-sea part of the Black Sea in 1972. They visually observed inclusions of hydrates, similar to frost, in the cavities of the soil extracted from the bottom. In fact, this is the first officially recognized observation in the world of natural gas hydrates in rocks. The data of A. G. Efremova and B. P. Zhizhchenko were subsequently cited many times by foreign and domestic authors. Based on their research, the first methods for sampling submarine gas hydrates were developed in the United States. Later, A.G. Efremova, working on an expedition for bottom sampling in the Caspian Sea (1980), was also the first in the world to establish the hydrate content of bottom sediments of this sea, which allowed other scientists to carry out detailed studies in later studies (G.D. Ginsburg, V . A. Solovyov and others) to identify a hydrate-bearing province (associated with mud volcanism) in the Southern Caspian Sea.

A great contribution to geological and geophysical studies of hydrate-containing rocks was made by employees of the Norilsk complex laboratory of VNIIGAZ M. Kh. Sapir, A. E. Benyaminovich and others, who studied the Messoyakha gas field, the initial reservoir P, T-conditions of which practically coincided with the conditions of methane hydrate formation. In the early 70s, these researchers laid down the principles for recognizing hydrate-containing rocks using comprehensive well logging data. At the end of the 70s, research in this area in the USSR practically ceased. At the same time, in the USA, Canada, Japan and other countries they have been developed and methods for geophysical identification of hydrate-saturated rocks in geological sections based on complex logging data have now been developed. In Russia, on the basis of VNIIGAZ, one of the first experimental studies in the world on modeling hydrate formation in dispersed rocks was carried out. Thus, A. S. Shalyakho (1974) and V. A. Nenakhov (1982), by saturating sand samples with hydrates, established a pattern of changes in the relative gas permeability of rock depending on hydrate saturation (A. S. Shalyakho) and the maximum gradient shift of pore water in hydrate-containing rocks (V.A. Nenakhov) are two important characteristics for predicting gas hydrate gas production.

Important work was also carried out by E.V. Zakharov and S.G. Yudin (1984) on the prospects for searching for hydrate-containing sediments in the Sea of ​​Okhotsk. This publication turned out to be predictive: two years after its publication, a whole series of articles appeared on the detection of hydrate-containing sediments during seismic profiling, bottom sampling, and even during visual observation from underwater manned vehicles in various parts of the Sea of ​​Okhotsk. To date, Russia's hydrate gas resources in discovered submarine accumulations alone are estimated at several trillion m3. Despite the cessation of funding for research on natural gas hydrates in 1988, work at VNIIGAZ was continued by V. S. Yakushev, V. A. Istomin, V. I. Ermakov and V. A. Skorobogatov on a no-budget basis (research on natural gas hydrates was not included in official topics of the institute until 1998). A special role in organizing and conducting research was played by Professor V.I. Ermakov, who constantly paid attention to the latest achievements in the field of natural gas hydrates and supported this research at VNIIGAZ throughout his entire work at the institute.

In 1986--1988 two original experimental chambers were developed and constructed for the study of gas hydrates and hydrate-containing rocks, one of which made it possible to observe the process of formation and decomposition of hydrocarbon gas hydrates under an optical microscope, and the other - to study the formation and decomposition of hydrates in rocks of various compositions and structures thanks to a replaceable inner sleeve.

To date, similar chambers in a modified form for studying hydrates in the pore space are used in Canada, Japan, Russia and other countries. The experimental studies carried out made it possible to detect the effect of self-preservation of gas hydrates at negative temperatures

It lies in the fact that if a monolithic gas hydrate obtained under normal equilibrium conditions is cooled to a temperature below 0°C and the pressure above it is reduced to atmospheric pressure, then after the initial surface decomposition, the gas hydrate is self-isolated from the environment by a thin film of ice, which prevents further decomposition. After this, the hydrate can be stored for a long time at atmospheric pressure (depending on temperature, humidity and other environmental parameters). The discovery of this effect made a significant contribution to the study of natural gas hydrates.

Development of a methodology for obtaining and studying hydrate-containing samples of various dispersed rocks, refinement of the methodology for studying natural hydrate-containing samples, conducting the first studies of natural hydrate-containing samples raised from the frozen strata of the Yamburg gas condensate field (1987) confirmed the existence of methane hydrates in a “preserved” form in the frozen strata, and also made it possible to establish a new type of gas hydrate deposits - relict gas hydrate deposits, distributed outside the modern SGI.

In addition, the self-preservation effect has opened up new possibilities for storing and transporting gas in a concentrated form, but without increased pressure. Subsequently, the effect of self-preservation was experimentally confirmed by researchers in Austria (1990) and Norway (1994) and is currently being studied by specialists from different countries (Japan, Canada, USA, Germany, Russia).

In the mid-90s, VNIIGAZ, in collaboration with Moscow State University (Department of Geocryology - Associate Professor E.M. Chuvilin and co-workers), carried out studies of core samples from intervals of gas shows from the permafrost strata in the southern part of the Bovanenkovo ​​gas condensate field using the methodology developed earlier during research samples of permafrost from the Yamburg gas condensate field.

The research results showed the presence of dispersed relict gas hydrates in the pore space of frozen rocks. Similar results were later obtained in a study of permafrost in the Mackenzie River delta (Canada), where hydrates were identified not only using the proposed Russian method, but were also visually observed in the core. In recent years (after a meeting at OAO Gazprom in 2003), research on hydrates in Russia has continued in various organizations both through state budget funding (two integration projects of the Siberian Branch of the Russian Academy of Sciences, small grants from the Russian Foundation for Basic Research, a grant from the Governor of Tyumen, a grant from the Ministry of Higher Education of the Russian Federation) , and through grants from international funds - INTAS, SRDF, UNESCO (under the “floating university” program - marine expeditions under the auspices of UNESCO under the slogan Training Through Research), COMEX (Kurele-Okhosk-Marine Experiment) , CHAO (Carbon-Hydrate Accumulations in the Okhotsk Sea), etc.

In 2002--2004 Research on unconventional sources of hydrocarbons, including gas hydrates (taking into account the commercial interests of Gazprom OJSC), continued at Gazprom VNIIGAZ LLC and Promgaz OJSC with a small scale of funding. Currently, research on gas hydrates is being carried out at OAO Gazprom (mainly at OOO Gazprom VNIIGAZ), at institutes of the Russian Academy of Sciences, and at universities.

Research into geological and technological problems of gas hydrates began in the mid-60s by VNIIGAZ specialists. At first, technological issues of preventing hydrate formation were raised and solved, then the topic gradually expanded: the kinetic aspects of hydrate formation were included in the sphere of interest, then significant attention was paid to geological aspects, in particular the possibilities of the existence of gas hydrate deposits, and the theoretical problems of their development.

8. New methods for monitoring the formation of gas hydrates

Gas hydrates can be produced in the laboratory from gas and water, but the process is complex. Hydrates form very slowly, even if the temperature and pressure in the apparatus fully correspond to the thermodynamic conditions for the stability of hydrates. The process turns out to be largely self-regulating: as pressure increases and temperature decreases, a solid layer of hydrates forms on the contact surface of gas and water; if it is not exposed to external influences, it effectively prevents further hydrate formation. This hydration barrier can be destroyed by active stirring, and therefore many researchers place crushers in the apparatus to accelerate crystallization. And even with this approach, it takes several days to fill a small apparatus.

Early in 1996, a group of researchers led by Peter Brewer of the Monterey Bay Research Institute (MBARH), California, proposed a new way to study hydrate formation. These scientists found that not only the pressure and temperature necessary for hydrate formation exist near the seabed, but also additional conditions under which the continuous formation of natural hydrates is possible.

In the experiment, transparent plastic tubes filled with seawater or a mixture of sediment and seawater were delivered to the seabed using a remotely operated submersible vehicle (ROU). At the appropriate depth, methane from the container was supplied to the holes in the bottom of each tube. The researchers feared that in the 3-4 hours available to them, the reaction might not occur. However, to their surprise, within a few minutes a translucent hydrate mass formed.

The ROVs used in these studies were equipped with thermometers, pressure gauges, conductivity sensors, and navigational instruments. However, the main research tool was a video camera mounted on a ROV to monitor the formation of hydrates. The result was great graphics, but no quantitative information. Further experiments are planned to study the spatial structure and distribution of hydrates in sediments.

9. Geography of distribution of gas hydrates

Most of the hydrates are concentrated, apparently, on the continental margins, where the water depth is approximately 500 m. In these zones, the water carries out organic material and contains nutrients for bacteria, which produce methane as a result of their vital activity. The usual depth of occurrence of SLNG is 100-500 m below the seabed, although they have sometimes been found on the seabed. In areas with developed permafrost, they can be present at shallower depths, since the surface temperature is lower. Large SLNGs have been detected offshore Japan, in the Blake Ridge area east of the US maritime boundary, on the continental margin of the Cascade Mountains region near Vancouver [British Columbia, Canada], and offshore New Zealand. Evidence of SPGG from direct sampling is limited worldwide. Most of the data on the location of hydrates was obtained indirectly: through seismic studies, GIS, from measurements during drilling, from changes in the salinity of pore water.

So far, only one example of gas production from LNG is known - at the Messoyakha gas field in Siberia. This field, discovered in 1968, was the first field in the northern part of the West Siberian Basin from which gas was produced. By the mid-1980s, more than 60 other fields had been discovered in the basin. The total reserves of these deposits amounted to 22 trillion. M 3 or one third of the world's gas reserves. According to an assessment made before the start of production, the reserves of the Messoyakha field were equal to 79 million m 3 of gas, of which one third was contained in hydrates overlying the free gas zone.

Apart from the Messoyakha field, the most studied are the NGVs in the Prudhoe Bay-Kiparuk River region in Alaska. In 1972, hydrate-containing samples were collected in sealed cores at the ARC0 and Exxon 2 North West Eileen exploration well on the North Slope of Alaska. From pressure and temperature gradients in the region, the thickness of the zone of steady state or hydrate stability in the Prudhoe Bay-Kiparuk region can be calculated. River. According to estimates, hydrates should be concentrated in the range of 210-950 m.

10. Areas of modern exploration for hydrates

Specialists from the Geological Survey of Canada (GCSJ, the Japan National Petroleum Corporation (JN0CI), the Japan Petroleum Exploration Company (JAPEX1, the US Geological Survey, the US Department of Energy and several companies, including Schlumberger, conducted a study of the gas hydrate reservoir (GH) in the Mackenzie River delta ( Northwest Territories, Canada) as part of a joint project. In 1998, a new exploration well, Mallick 2L-38, was drilled near an Imperial Oil Ltd. well that encountered a hydrate accumulation. The purpose of this work was to evaluate the properties of the hydrates. in natural occurrence and evaluate the possibility of determining these properties using downhole wireline tools.

Experience gained during research at the well. Mallik, proved to be very useful for studying the properties of natural hydrates. JAPEX and its associated groups have decided to begin a new hydrate drilling project in the Nankai Trench offshore Japan. About a dozen areas have been assessed as hydrate prospects based on the presence of BSRs (bottom-like reflectors).

11. The problem of industrial development of the gas hydrate form of accumulationanglehydrogenates

Intra-permafrost deposits. From the very beginning, the development of fields in the north of Western Siberia faced the problem of gas emissions from shallow intervals of the permafrost zone. These releases occurred suddenly and led to work stoppages at wells and even fires. Since the emissions occurred from the depth interval above the gas hydrate stability zone, for a long time they were explained by gas flows from deeper productive horizons through permeable zones and neighboring wells with poor-quality casing. At the end of the 80s, based on experimental modeling and laboratory studies of frozen core from the permafrost zone of the Yamburg gas condensate field, it was possible to identify the distribution of dispersed relict (preserved) hydrates in Quaternary sediments. These hydrates, together with local accumulations of microbial gas, can form gas-bearing layers from which emissions occur during drilling. The presence of relict hydrates in the shallow layers of the permafrost zone was further confirmed by similar studies in northern Canada and in the area of ​​the Bovanenkovo ​​gas condensate field. Thus, ideas about a new type of gas deposits were formed -- intra-permafrost metastable gas-gas-hydrate deposits, which, as tests of permafrost wells at the Bovanenkovo ​​gas condensate field have shown, represent not only a complicating factor, but also a certain resource base for local gas supply.

Intra-permafrost deposits contain only a small part of the gas resources that are associated with natural gas hydrates. The main part of the resources is confined to the gas hydrate stability zone - that depth interval (usually the first hundreds of meters) where the thermodynamic conditions for hydrate formation occur. In the north of Western Siberia this is a depth interval of 250--800 m, in the seas - from the bottom surface to 300--400 m, in particularly deep-water areas of the shelf and continental slope up to 500--600 m below the bottom. It was in these intervals that the bulk of natural gas hydrates were discovered.

During the study of natural gas hydrates, it became clear that it is not possible to distinguish hydrate-containing deposits from frozen deposits using modern means of field and borehole geophysics. The properties of frozen rocks are almost completely similar to those of hydrate-containing rocks. A nuclear magnetic resonance logging device can provide certain information about the presence of gas hydrates, but it is very expensive and is used extremely rarely in geological exploration practice. The main indicator of the presence of hydrates in sediments is core studies, where hydrates are either visible by visual inspection or determined by measuring the specific gas content during thawing.

Seabed stability. The decomposition of hydrates can lead to disruption of the stability of bottom sediments on continental slopes. The base of the HGT may be the site of a sharp decrease in the strength of the sedimentary rock strata. The presence of hydrates can prevent normal compaction and consolidation of sediments. Therefore, free gas retained below the HRT may become under increased pressure. Thus, any technology for developing hydrate deposits can be successful only if additional reduction in rock stability is excluded. An example of the complications that arise from the decomposition of hydrates can be found off the Atlantic coast of the United States. Here the seabed slope is 5°, and with such a slope the bottom must be stable. However, many underwater landslide scarps are observed. The depth of these benches is close to the maximum depth of the hydrate stability zone. In areas where landslides have occurred, BSRs are less distinct. This may be an indication that the hydrates are no longer present because they have moved. There is a hypothesis according to which, when the pressure in the SPTT decreases, as it should have happened when the sea level dropped during the Ice Age, the decomposition of hydrates at depth could begin and, as a result, the sliding of sediments saturated with hydrates

Such areas were discovered off the coast of the North. Carolinas, USA. In the area of ​​a huge underwater landslide wide 66 km seismic studies revealed the presence of a massive SPTT on both sides of the landslide scarp. However, there are no hydrates under the ledge itself.

Subsea landslides caused by hydrates can affect the stability of offshore platforms and pipelines.

Many experts believe that frequently cited estimates of the amount of methane in hydrates are exaggerated. And even if these estimates are correct, the hydrates may be dispersed in sedimentary rocks rather than concentrated in large clusters. In this case, extracting them can be difficult, economically unprofitable and dangerous for the environment.

12. Methods for extracting methane from hydrates

Gas hydrates are a group of unconventional hydrocarbon sources that include coal bed methane, hydrocarbons contained in tar sands, and black shale. Some of these sources (which do not include hydrates) are already used on an industrial scale. In most cases, the transition from an unused unconventional source to a used one depends on the size of the investment and the level of technology development.

Until recently, the development of technologies for the extraction of methane from hydrates remained the prerogative of the gas industry and proceeded slowly. Three methods are currently being considered: pressure reduction, heating and injection of hydrate formation inhibitors. The first method involves reducing the pressure to a level sufficient to decompose hydrates. This method can only be applied where free gas can be sampled from the area adjacent to the 3GG. At the same time, the reservoir pressure in the ZGG decreases, as happened at the Messoyakha field.

If there is no free gas under the GGG, then heating to a temperature at which hydrates decompose may be a suitable solution. An example of the implementation of this method could be the injection of relatively warm sea water into a gas hydrate formation on the shelf.

Injection of inhibitors, such as methanol, leads to a change in the values ​​of the equilibrium parameters of hydrates (increase in dissociation pressure, decrease in dissociation temperature). As a result, hydrates decompose and methane is released.

The most acceptable method from a practical point of view is pumping warm water. However, gas hydrates can only be considered a potential source of hydrocarbons when it can be demonstrated that the resulting energy exceeds the energy required to release methane.

13. Other uses of gas hydrates

Regardless of whether natural hydrates become another global fuel source, the accumulated knowledge about hydrates opens up other possibilities for their use. Researchers at the Norwegian University of Science and Technology (NTNU1 in Trondheim) are studying the possibility of storing and transporting natural gas in the form of hydrates at atmospheric pressure. Experiments carried out at the university showed that the resulting hydrates do not decompose at atmospheric pressure if they are at a temperature of -15 degrees C or lower. This fact allows us to outline the following technologies:

· Associated gas from oil fields can be converted into a hydrate state and transported by tankers. The crushed hydrates can also be mixed with cooled oil and transported as a slurry by tankers or pipelines.

If pipelines cannot be used, frozen hydrates can be transported over long distances in the same way as liquefied natural gas (LNG)

· If the gas needs to be stored, it can be hydrated and stored refrigerated at atmospheric pressure.

· Nitrogen, carbon dioxide and hydrogen sulfide can be separated from methane by converting it into a hydrate state.

· The process of hydrate formation can be used to desalinate water and extract biological materials from it.

· Carbon dioxide can be extracted from atmospheric air and converted into a hydrated state for storage and subsequent burial in deep-sea zones.

The more countries stop flaring gas and the more mining companies want to find alternatives to building pipelines, the sooner the technology for converting gas into a hydrated state for transportation or disposal will develop.

Conclusion

Oil companies have not yet shown any interest in natural gas hydrates. At the same time, a new product will soon appear on the technology market, based on the property of natural gas to form solid compounds under certain conditions (by the way, until now this property has brought nothing but trouble and expense, since thanks to it, gas pipelines often have gas hydrate plugs). Several large companies are involved in the development of this product, including Gazprom, Shell, Total, Arco, Phillips and others. We are talking about converting natural gas into gas hydrates, which ensures its transportation without the use of a pipeline and storage in above-ground storage facilities at normal pressure. The development of this technology was a by-product of ten years of research into natural gas hydrates in Norwegian scientific laboratories. In the last two years, this research has taken the form of a commercial project supported jointly by the Research Council of Norway and multinational oil companies.

Considering gas hydrates as an energy source is certainly a very important development for the energy industry. With the annual increase in the consumption of hydrocarbon raw materials, interest in unconventional fuel sources will also increase. And a huge number of discoveries related to gas hydrates await us.

Bibliography

1. Makogon Yu.F. “Natural gas hydrates”, Nedra, 2008.

2. Bazhenova O.K., Burlin Yu.K. "Geology and geochemistry of oil and gas", Moscow State University 2007.

3. Chernikov K.A. and others. Dictionary of Geology of Oil and Gas, Nedra, 1988

4. Collet TS and Kuushraa VA: “Hydrates Сontain Vast Store of World Gas Resources,” Oil Gas Journal 96, no. 19 (May 11, 1998): 90-95.

5. Trofimchuk A.A., Chersky N.V., Tsarev V.P. Hydrates - a new source of hydrocarbons // Nature - 2010. No. 3.

6. Information was used from the site: geo.web.ru

Posted on Allbest.ru

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Gas hydrates are a relatively new and potentially abundant source of natural gas. They are molecular compounds of water and methane that exist at low temperatures and high pressure. Due to their external similarity, gas hydrates began to be called “burning ice.” In nature, gas hydrates are found either in permafrost zones or in deep water, which initially creates difficult conditions for their development.

In 2013, Japan was the first in the world to conduct successful experimental production of methane from gas hydrates at sea. This achievement forces us to take a closer look at the prospects for the development of gas hydrates. Can we expect a gas hydrate revolution after the “unexpected” onset of the shale revolution?

Preliminary estimates of gas hydrate reserves in the world indicate that they exceed reserves of conventional natural gas by an order of magnitude. But, firstly, they are very approximate; secondly, only a small part of them can be extracted at the current level of technology development. And even this part will require huge costs and may be associated with unforeseen environmental risks.

Nevertheless, a number of countries, such as the USA, Canada and countries in the Asian region, which are characterized by high prices for natural gas and growing demand for it, are showing great interest in developing the development of gas hydrates and continue to actively explore this area.

Experts note high uncertainty regarding the future of gas hydrates and believe that their industrial development will begin no earlier than in 10-20 years, but this resource cannot be overlooked.

Gas hydrates (clathrates) are solid crystalline compounds of low molecular weight gases, such as methane, ethane, propane, butane, etc., with water. Outwardly, they resemble snow or loose ice. They are stable at low temperatures and high pressure; If these conditions are violated, gas hydrates easily decompose into water and gas. The most common natural hydrate-forming gas is methane.

Technogenic and natural gas hydrates

There are man-made and natural gas hydrates.
Technogenic hydrates can form in conventional natural gas production systems (in the bottomhole zone, in well bores, etc.) and during its transportation. In the technological processes of production and transportation of conventional natural gas, the formation of gas hydrates is considered an undesirable phenomenon, which requires further improvement of methods for their prevention and elimination. At the same time, technogenic gas hydrates can be used to store large

gas volumes, in gas purification and separation technologies, for seawater desalination and in energy storage for refrigeration and air conditioning purposes.

Natural hydrates can form clusters or be in a dispersed state. They are found in places that combine low temperatures and high pressure, such as deep sea (bottom areas of deep lakes, seas and oceans) and permafrost zones (Arctic region). The depth of gas hydrates on the seabed is 500-1,500 m, and in the Arctic zone - 200-1,000 m.

Free gas. In this case, the development of gas hydrate fields occurs in a manner similar to conventional gas production. The production of free gas from the lower formation causes a decrease in pressure in the hydrate-saturated formation and destroys the boundary between them.

Gas produced from gas hydrates complements gas produced from the underlying formation. This is the most promising direction for developing gas hydrate deposits.

Free water. When there is water underneath a gas hydrate deposit, reducing the pressure in the hydrate zone can be achieved by extracting it. This method is technically feasible, but less economically attractive compared to the first.

No bottom layer. Prospects for the development of gas hydrate fields, surrounded below and above by impenetrable sedimentary rocks, remain vague

For example, the possible gas hydrate resources in the United States by type of deposit are shown in the Figure (in comparison with natural gas resources). The “gas hydrate pyramid” also reflects the potential for gas production from gas hydrate fields of various types. At the top of the pyramid are well-explored Arctic deposits close to existing infrastructure, such as the Mallick deposit in Canada. This is followed by less studied gas hydrate formations with similar geological characteristics (on the North Slope of Alaska), but requiring infrastructure development. Recent estimates place the technically recoverable gas hydrate resources of Alaska's North Slope at 2.4 trillion. cube m of gas. Following the Arctic reserves are deepwater fields of medium and high saturation. Since the cost of their development is potentially extremely high, the most promising region for this is considered to be the Gulf of Mexico, where oil and gas production infrastructure has already been created. The extent of these resources is not yet well known, but the US Minerals Management Service is studying them.

Fig. 1 “Gas hydrate pyramid”

At the foot of the pyramid (Figure 2) there are accumulations of gas hydrates, which are characterized by an extremely uneven distribution of fine-grained and undeformed sedimentary rocks in large volumes. A typical example of such an accumulation is a deep-sea field off the Blake Ridge (the coast of the American state of Carolina). At the current level of technology development, their development is not possible.

On an industrial scale

On an industrial scale, methane production from gas hydrate deposits is not carried out anywhere in the world, and it is planned only in Japan - for 2018-2019. However, a number of countries are implementing research programs. The most active here are the USA, Canada and Japan.

Japan has advanced the furthest in studying the potential for developing gas hydrate deposits. In the early 2000s, the country began implementing a program to develop gas hydrates.

To support it, by decision of government authorities, the MH21 research consortium was organized, aimed at creating a technological basis for the industrial development of gas hydrate deposits. In February 2012, Japan Oil, Gas and Metals National Corporation (JOGMEC) began test drilling in the Pacific Ocean, 70 km south of the Atsumi Peninsula, to produce methane hydrates. And in March 2013, Japan (the first in the world) began test extraction of methane from gas hydrates in the open sea. JOGMEC estimates that with existing reserves of methane hydrates on the country's shelf, Japan can cover its natural gas needs for 100 years into the future.

In the field of gas hydrate development, Japan is developing scientific cooperation with Canada, the USA and other countries. Canada has an extensive research program; Together with Japanese specialists, wells were drilled at the mouth of the Mackenzie River (Mallick field). US gas hydrate research projects are concentrated in the permafrost zone of Alaska and deep water in the Gulf of Mexico.

Less extensive, but nonetheless notable, research into gas hydrates is being carried out by countries such as South Korea, China and India. South Korea is assessing gas hydrate potential in the Sea of ​​Japan. Research has shown that the Ulleung deposit is the most promising for further development. India established its national research program on gas hydrates in the mid-1990s. The main object of her research is the Krishna-Godavari field in the Bay of Bengal.

China's gas hydrate program includes research on the South China Sea shelf near Guangdong Province and permafrost on the Qinghai Plateau in Tibet. A number of other countries, including Norway, Mexico, Vietnam and Malaysia, have also shown interest in gas hydrate research. There are also research programs for the study of gas hydrates in the European Union: for example, in the 2000s, the HYDRATECH (Methane Hydrate Assessment Technique on the European Shelf) program and the HYDRAMED (Geological Assessment of Gas Hydrates in the Mediterranean) program operated. But what distinguishes European programs is their emphasis on scientific and environmental issues.

Russia has its own gas hydrate deposits. Their presence has been confirmed at the bottom of Lake Baikal, the Black, Caspian and Okhotsk seas, as well as in the Yamburg, Bovanenkovskoye, Urengoyskoye, Messoyakha fields.

Gas hydrates were not developed in these fields, and their presence was considered as a factor complicating the development of conventional gas (if available). There are also assumptions, supported by theoretical arguments, about the presence of a large number of gas hydrate deposits throughout the entire area of ​​the Russian Arctic shelf.

Geological studies of gas hydrates began in the USSR back in the 1970s. In modern Russia, laboratory studies of gas hydrates are mainly carried out: for example, the creation of technologies to prevent their formation in gas transportation systems or the determination of their physical, chemical and other properties. Among the centers for the study of gas hydrates in Russia, we can note Moscow State University, the Siberian Branch of the Russian Academy of Sciences, Gazprom VNIIGAZ LLC, the University of Oil and Gas named after. Gubkina.
In 2003, applied research to assess the gas hydrate potential in Russia was initiated by Gazprom OJSC.

Preliminary estimates by Gazprom VNIIGAZ indicate the presence of gas hydrate resources in the country of 1,100 trillion. cube m. In mid-2013, information appeared that the Far Eastern Geological Institute of the Russian Academy of Sciences invited Rosneft to study the possibility of extracting gas hydrates on the Kuril Islands shelf, estimating their potential at 87 trillion. cube m. There are no specialized state programs for the research and production of gas hydrates following the example of the countries noted above in Russia. Gas hydrates are mentioned in the General Scheme for the Development of the Gas Industry until 2030

only once in the context of the expected directions of scientific and technological progress.

According to various estimates, the reserves of terrestrial hydrocarbons in hydrates range from 1.8·10 5 to 7.6·10 9 km³. Nowadays, natural gas hydrates are attracting special attention as a possible source of fossil fuels, as well as a contributor to climate change.

Formation of gas hydrates

Gas hydrates are divided into technogenic (artificial) and natural (natural). All known gases at certain pressures and temperatures form crystalline hydrates, the structure of which depends on the composition of the gas, pressure and temperature. Hydrates can exist stably over a wide range of pressures and temperatures. For example, methane hydrate exists at pressures from 2*10 -8 to 2*10 3 MPa and temperatures from 70 to 350 K.

Some properties of hydrates are unique. For example, one volume of water, upon transition to the hydrate state, binds 207 volumes of methane. At the same time, its specific volume increases by 26% (when water freezes, its specific volume increases by 9%). 1 m 3 of methane hydrate at P=26 atm and T=0°C contains 164 volumes of gas. In this case, the share of gas is 0.2 m 3, and water is 0.8 m 3. The specific volume of methane in the hydrate corresponds to a pressure of about 1400 atm. The decomposition of hydrate in a closed volume is accompanied by a significant increase in pressure. Figure 3.1.1 shows a diagram of the conditions for the existence of hydrate of some components of natural gas in pressure-temperature coordinates.

Figure 3.1.1 - Gas-hydrate formation curves for some natural gas components.

For the formation of gas hydrate, the following three conditions are necessary:

1. Favorable thermobaric conditions. The formation of gas hydrates is favored by the combination of low temperature and high pressure.

2. Presence of a hydrate-forming substance. Hydrate-forming substances include methane, ethane, propane, carbon dioxide, etc.

3. Sufficient amount of water. There should be neither too little nor too much water.

To prevent gas hydrate formation, it is enough to exclude one of three conditions.

Natural gas hydrates are a metastable mineral, the formation and decomposition of which depends on temperature, pressure, chemical composition of gas and water, properties of the porous medium, etc.

The morphology of gas hydrates is very diverse. Currently, there are three main types of crystals:

· massive crystals. They are formed due to the sorption of gas and water on the entire surface of a continuously growing crystal;

· Whisker crystals. Occur during tunnel sorption of molecules to the base of a growing crystal;

· gel crystals. They are formed in a volume of water from gas dissolved in it when the conditions for hydrate formation are reached.

In rock layers, hydrates can be either distributed in the form of microscopic inclusions or form large particles, up to extended layers many meters thick.

Due to its clathrate structure, a unit volume of gas hydrate can contain up to 160-180 volumes of pure gas. The density of the hydrate is lower than the density of water and ice (for methane hydrate, about 900 kg/m³).

The accelerated formation of gas hydrates is facilitated by the following phenomena:

· Turbulence. The formation of gas hydrates actively occurs in areas with high flow rates of the medium. When mixing gas in a pipeline, process tank, heat exchanger, etc. the intensity of gas hydrate formation increases.

· Crystallization centers. The crystallization center is a point at which there are favorable conditions for a phase transformation, in this case, the formation of a solid phase from a liquid one.

· Free water. The presence of free water is not a prerequisite for hydrate formation, but the intensity of this process in the presence of free water increases significantly. In addition, the water-gas interface is a convenient crystallization center for the formation of gas hydrates.

Structure of hydrates

In the structure of gas hydrates, water molecules form an openwork frame (that is, a host lattice), in which there are cavities. It has been established that the frame cavities are usually 12- ("small" cavities), 14-, 16- and 20-sided ("large" cavities), slightly deformed relative to the ideal shape. These cavities can be occupied by gas molecules (“guest molecules”). Gas molecules are connected to the water framework by van der Waals bonds. In general, the composition of gas hydrates is described by the formula M n H 2 O, where M is a hydrate-forming gas molecule, n is the number of water molecules per included gas molecule, and n is a variable number depending on the type of hydrate. forming agent, pressure and temperature.

The cavities, combining with each other, form a continuous structure of various types. According to the accepted classification, they are called KS, TS, GS - cubic, tetragonal and hexagonal structure, respectively. In nature, the most common hydrates are types KS-I (eng. sI), KS-II (eng. sII), while the rest are metastable.

Table 3.2.1 - Some structures of clathrate frameworks of gas hydrates.

Figure 3.2.1 - Crystal modifications of gas hydrates.

As the temperature increases and the pressure decreases, the hydrate decomposes into gas and water, absorbing a large amount of heat. The decomposition of hydrate in a closed volume or in a porous medium (natural conditions) leads to a significant increase in pressure.

Crystalline hydrates have high electrical resistance, conduct sound well, and are practically impenetrable to free water and gas molecules. They are characterized by abnormally low thermal conductivity (for methane hydrate at 273 K it is five times lower than that of ice).

The van der Waals-Platteu theory is currently widely used to describe the thermodynamic properties of hydrates. The main provisions of this theory:

· the host lattice does not deform depending on the degree of filling with guest molecules or their type;

· each molecular cavity can contain no more than one guest molecule;

· interaction of guest molecules is negligible;

· Statistical physics is applicable to the description.

Despite the successful description of thermodynamic characteristics, the van der Waals - Platteu theory contradicts the data of some experiments. In particular, it has been shown that guest molecules are capable of determining both the symmetry of the hydrate crystal lattice and the sequence of phase transitions of the hydrate. In addition, a strong effect of guests on host molecules was discovered, causing an increase in the most probable frequencies of natural vibrations.

Most natural gases (CH4, C2H6, C3H8, CO2, N2, H2S, isobutane, etc.) form hydrates, which exist under certain thermobaric conditions. The area of ​​their existence is confined to sea bottom sediments and to areas of permafrost. The predominant natural gas hydrates are methane and carbon dioxide hydrates.

During gas production, hydrates can form in well bores, industrial communications and main gas pipelines. By depositing on the walls of pipes, hydrates sharply reduce their throughput. To combat the formation of hydrates in gas fields, various inhibitors (methyl alcohol, glycols, 30% CaCl2 solution) are introduced into wells and pipelines, and the temperature of the gas flow is maintained above the temperature of hydrate formation using heaters, thermal insulation of pipelines and selection of an operating mode that ensures maximum gas flow temperature. To prevent hydrate formation in main gas pipelines, gas drying is the most effective - cleaning gas from water vapor.

Composition and properties of water

About 71% of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice) - 361.13 million km 2. On Earth, approximately 96.5% of the world's water is in the oceans, 1.7% of the world's reserves are groundwater, another 1.7% is in the glaciers and ice caps of Antarctica and Greenland, a small part is in rivers, lakes and swamps, and 0.001% in clouds (formed from particles of ice and liquid water suspended in the air). Most of the earth's water is salty, unsuitable for agriculture and drinking. The share of fresh water is about 2.5%, with 98.8% of this water located in glaciers and groundwater. Less than 0.3% of all fresh water is found in rivers, lakes and the atmosphere, and an even smaller amount (0.003%) is found in living organisms.

The role of water in the emergence and maintenance of life on Earth, in the chemical structure of living organisms, and in the formation of climate and weather is extremely important. Water is the most important substance for all living beings on planet Earth.

Chemical composition of water

Water (hydrogen oxide) is a binary inorganic compound with the chemical formula H 2 O. A water molecule consists of two hydrogen atoms and one oxygen atom, which are connected by a covalent bond. Under normal conditions, it is a transparent liquid, colorless (in small volumes), odor and taste. In the solid state it is called ice (ice crystals can form snow or frost), and in the gaseous state it is called water vapor. Water can also exist in the form of liquid crystals (on hydrophilic surfaces). It is approximately 0.05 times the mass of the Earth.

The composition of water can be determined using an electric decomposition reaction. Two volumes of hydrogen are formed per volume of oxygen (the volume of gas is proportional to the amount of substance):

2H 2 O = 2H 2 + O 2

Water is made up of molecules. Each molecule contains two hydrogen atoms connected by covalent bonds to one oxygen atom. The angle between the bonds is about 105º.

National Mineral Resources University Mining

Scientific supervisor: Yuri Vladimirovich Gulkov, Candidate of Technical Sciences, National Mineral Resources Mining University

Annotation:

This article discusses the chemical and physical properties of gas hydrates, the history of their study and research. In addition, the main problems that impede the organization of commercial production of gas hydrates are considered.

In this article we describe the chemical and physical characteristics of gas hydrates, the history of their study and research. In addition, the basic problems hindering the organization of commercial production of gas hydrates are considered.

Keywords:

gas hydrates; energy; commercial mining; Problems.

gas hydrates; power engineering; commercial extraction; problems.

UDC 622.324

Introduction

Initially, man used his own strength as a source of energy. After some time, the energy of wood and organic matter came to the rescue. About a century ago, coal became the main energy resource; 30 years later, its primacy was shared by oil. Today, the world's energy sector is based on the gas-oil-coal triad. However, in 2013, this balance was shifted towards gas by Japanese energy workers. Japan is the world leader in gas imports. The State Oil, Gas and Metals Corporation (JOGMEC) (Japan Oil, Gas & Metals National Corp.) was the first in the world to obtain gas from methane hydrate at the bottom of the Pacific Ocean from a depth of 1.3 kilometers. The trial production lasted only 6 weeks, despite the fact that the plan considered two-week production, 120 thousand cubic meters of natural gas were produced. This discovery will allow the country to become independent from imports and fundamentally change its economy. What is gas hydrate and how can it affect global energy?

The purpose of this article is to consider problems in the development of gas hydrates.

To achieve this, the following tasks were set:

• Explore the history of gas hydrate research
• Study chemical and physical properties
• Consider the main problems of development

Relevance

Traditional resources are not evenly distributed across the Earth, and they are also limited. According to modern estimates, oil reserves by today's consumption standards will last for 40 years, natural gas energy resources for 60-100. World shale gas reserves are estimated at approximately 2,500-20,000 trillion. cube m. This is the energy reserve of humanity for more than a thousand years. Commercial extraction of hydrates would raise the world energy sector to a qualitatively new level. In other words, the study of gas hydrates has opened up an alternative source of energy for humanity. But there are also a number of serious obstacles to their study and commercial production.

Historical reference

The possibility of the existence of gas hydrates was predicted by I.N. Strizhov, but he spoke about the inexpediency of their extraction. Villar first obtained methane hydrate in the laboratory in 1888, along with hydrates of other light hydrocarbons. Initial encounters with gas hydrates were seen as problems and obstacles to energy production. In the first half of the 20th century, it was established that gas hydrates cause plugging in gas pipelines located in Arctic regions (at temperatures above 0 °C). In 1961 the discovery of Vasiliev V.G., Makagon Yu.F., Trebin F.A., Trofimuk A.A., Chersky N.V. was registered. “The property of natural gases to be in a solid state in the earth’s crust,” which announced a new natural source of hydrocarbons - gas hydrate. After this, they started talking about the exhaustibility of traditional resources more loudly, and already 10 years later the first gas hydrate deposit was discovered in January 1970 in the Arctic, on the border of Western Siberia, it is called Messoyakha. Further, large expeditions of scientists from both the USSR and many other countries were carried out.

Word of chemistry and physics

Gas hydrates are gas molecules stuck around water molecules, like “gas in a cage.” This is called an aqueous clathrate framework. Imagine that in the summer you caught a butterfly in your palm, the butterfly is a gas, your palms are water molecules. Because you protect the butterfly from external influences, but it will retain its beauty and individuality. This is how the gas behaves in the clathrate framework.

Depending on the conditions of formation and the state of the hydrate former, hydrates appear externally as clearly defined transparent crystals of various shapes or as an amorphous mass of densely compressed “snow.”

Hydrates occur under certain thermobaric conditions - phase equilibrium. At atmospheric pressure, gas hydrates of natural gases exist down to 20-25 °C. Due to its structure, a unit volume of gas hydrate can contain up to 160-180 volumes of pure gas. The density of methane hydrate is about 900 kg/m³, which is lower than the density of water and ice. When phase equilibrium is disturbed: an increase in temperature and/or a decrease in pressure, the hydrate decomposes into gas and water with the absorption of a large amount of heat. Crystalline hydrates have high electrical resistance, conduct sound well, are practically impenetrable to free water and gas molecules, and have low thermal conductivity.

Development

Gas hydrates are difficult to access because... To date, it has been established that about 98% of gas hydrate deposits are concentrated on the shelf and continental slope of the ocean, at water depths of more than 200 - 700 m, and only 2% - in the subpolar parts of the continents. Therefore, problems in developing commercial production of gas hydrates are encountered already at the stage of developing their deposits.

Today, there are several methods for detecting gas hydrate deposits: seismic sounding, gravimetric method, measuring heat and diffuse flows over the deposit, studying the dynamics of the electromagnetic field in the region under study, etc.

Seismic sounding uses two-dimensional (2-D) seismic data; in the presence of free gas under a hydrate-saturated formation, the lower position of hydrate-saturated rocks is determined. But seismic exploration cannot detect the quality of the deposit or the degree of hydrate saturation of the rocks. In addition, seismic exploration is not applicable on complex terrain. But it is most beneficial from the economic side, however, it is better to use it in addition to other methods.

For example, the gaps can be filled by using electromagnetic exploration in addition to seismic exploration. It will make it possible to more accurately characterize the rock, thanks to the individual resistances at the points where gas hydrates occur. The US Department of Energy plans to conduct it starting in 2015. The seismoelectromagnetic method was used to develop the Black Sea fields.

It is also cost-effective to develop a saturated deposit using a combined development method, when the process of hydrate decomposition is accompanied by a decrease in pressure with simultaneous thermal effects. Reducing the pressure will save thermal energy spent on the dissociation of hydrates, and heating the pore medium will prevent the re-formation of gas hydrates in the near-wellbore zone of the formation.

Production

The next stumbling block is the actual extraction of hydrates. Hydrates occur in solid form, which causes difficulties. Since gas hydrate occurs under certain thermobaric conditions, if one of them is violated, it will decompose into gas and water; in accordance with this, the following hydrate extraction technologies have been developed.

1. Depressurization:

When the hydrate leaves phase equilibrium it will decompose into gas and water. This technology is famous for its triviality and economic feasibility, in addition, the success of the first Japanese production in 2013 rests on its shoulders. But not everything is so rosy: the resulting water at low temperatures can clog equipment. In addition, the technology is really effective, because... During a test production of methane at the Mallick field, 13,000 cubic meters were produced in 5.5 days. m of gas, which is many times higher than production at the same field using heating technology - 470 cubic meters. m of gas in 5 days. (see table)

2. Heating:

Again, you need to decompose the hydrate into gas and water, but this time using heat. Heat supply can be carried out in different ways: coolant injection, hot water circulation, steam heating, electrical heating. I would like to dwell on the interesting technology invented by researchers from the University of Dortmund. The project involves laying a pipeline to gas hydrate deposits on the seabed. Its peculiarity is that the pipe has double walls. Sea water, heated to 30-40˚C, the phase transition temperature, is supplied to the field through the inner pipe, and bubbles of methane gas along with the water rise upward through the outer pipe. There, methane is separated from the water, sent to tanks or into the main pipeline, and warm water returns down to the gas hydrate deposits. However, this extraction method requires high costs and a constant increase in the amount of heat supplied. In this case, the gas hydrate decomposes more slowly.

3. Introduction of inhibitor:

I also use the injection of an inhibitor to decompose the hydrate. At the Institute of Physics and Technology of the University of Bergen, carbon dioxide was considered as an inhibitor. Using this technology, it is possible to obtain methane without directly extracting the hydrates themselves. This method is already being tested by the Japan National Oil, Gas and Metals Corporation (JOGMEC) with the support of the US Department of Energy. But this technology is fraught with environmental hazards and requires high costs. The reaction proceeds more slowly.

Project name	date	Participating countries	Companies	Technology
Mallik, Canada		Japan, USA Channel, Germany, India	JOGMEC, BP, Chevron Texaco	Heater (coolant - water)
North Slope of Alaska, USA		USA, Japan	Conoco Phillips, JOGMEC	Carbon dioxide injection, inhibitor injection
Alaska, USA			BP, Schlumberger	Drilling to study the properties of gas hydrate
Mallik, Canada		Japan, Canada	JOGMEC as part of a private public consortium	Depressurization
Fire in Ice (IgnikSikumi), Alaska, USA		USA, Japan, Norway	Conoco Phillips, JOGMEC, University of Bergen (Norway)	Carbon dioxide injection
A joint project (JointIndustryProject) Gulf of Mexico, USA			Chevron as consortium leader	Drilling to study the geology of gas hydrates
Near Atsumi Peninsula, Japan			JOGMEC, JAPEX, Japan Drilling	Depressurization

Source - analytical center based on open source materials

Technologies

Another reason for the undeveloped commercial production of hydrates is the lack of technology for their profitable extraction, which provokes large capital investments. Depending on the technology, there are different barriers: the operation of special equipment for the introduction of chemical elements and/or local heating to avoid the re-formation of gas hydrates and plugging of wells; application of technologies that prevent sand mining.

For example, in 2008, preliminary estimates for the Mallick field in the Canadian Arctic indicated that development costs ranged from $195-230/thousand. cube m for gas hydrates located above free gas, and in the range of 250-365 dollars/thousand. cube m for gas hydrates located above free water.

To solve this problem, it is necessary to popularize the commercial production of hydrates among scientific personnel. Organize more scientific conferences, competitions to improve old or create new equipment, which could provide lower costs.

Environmental hazard

Moreover, the development of gas hydrate fields will inevitably lead to an increase in the volume of natural gas released into the atmosphere and, as a result, to an increase in the greenhouse effect. Methane is a powerful greenhouse gas and, despite the fact that its lifetime in the atmosphere is shorter than CO₂, the warming caused by the release of large quantities of methane into the atmosphere will be tens of times faster than the warming caused by carbon dioxide. In addition, if global warming, the greenhouse effect, or other reasons cause the collapse of at least one gas hydrate deposit, this will cause a colossal release of methane into the atmosphere. And, like an avalanche, from one occurrence to another, this will lead to global climate change on Earth, and the consequences of these changes cannot be even approximately predicted.

To avoid this, it is necessary to integrate data from complex exploration analyzes and predict the possible behavior of deposits.

Detonation

Another unsolved problem for miners is the very unpleasant property of gas hydrates to “detonate” with the slightest shocks. In this case, the crystals quickly undergo a phase of transformation into a gaseous state, and acquire a volume several tens of times greater than the original one. Therefore, reports from Japanese geologists very carefully talk about the prospect of developing methane hydrates - after all, the disaster of the Deepwater Horizon drilling platform, according to a number of scientists, including UC Berkeley professor Robert Bee, was the result of the explosion of a giant methane bubble that formed from bottom hydrate deposits disturbed by drillers.

Mining of oil and gas

Gas hydrates are considered not only from the energy resource side; they are more often encountered during oil production. Once again we turn to the death of the Deepwater Horizon platform in the Gulf of Mexico. Then, to control the escaping oil, a special box was built, which they planned to place above the emergency wellhead. But the oil turned out to be very carbonated, and methane began to form entire ice deposits of gas hydrates on the walls of the box. They are about 10% lighter than water, and when the amount of gas hydrates became large enough, they simply began to lift the box, which, in general, was predicted in advance by experts.

The same problem was encountered in the production of traditional gas. In addition to “natural” gas hydrates, the formation of gas hydrates is a big problem in gas pipelines located in temperate and cold climates, since gas hydrates can clog the gas pipeline and reduce its throughput. To prevent this from happening, a small amount of an inhibitor is added to natural gas or heating is simply used.

These problems are solved in the same ways as during production: by lowering the pressure, heating, introducing an inhibitor.

Conclusion

This article examined the barriers to commercial production of gas hydrates. They occur already at the stage of development of gas fields, directly during production itself. In addition, gas hydrates are currently a problem in oil and gas production. Today, impressive gas hydrate reserves and economic profitability require accumulation of information and clarification. Experts are still searching for optimal solutions for developing gas hydrate fields. But with the development of technology, the cost of developing deposits should decrease.

Bibliography:

1. Vasiliev A., Dimitrov L. Assessment of the spatial distribution and reserves of gas hydrates in the Black Sea // Geology and Geophysics. 2002. No. 7. v. 43.
2. Dyadin Yu. A., Gushchin A.L. Gas hydrates. // Soros educational journal, No. 3, 1998, p. 55–64
3. Makogon Yu.F. Natural gas hydrates: distribution, formation models, resources. – 70 s.
4. Trofimuk A. A., Makogon Yu. F., Tolkachev M. V., Chersky N. V. Features of detection of exploration and development of gas hydrate deposits - 2013 [Electronic resource] http://vimpelneft.com/fotogalereya/ 6-komanda-vymlnefti/detail/32-komanda-vympelnefti
5. Chemistry and Life, 2006, No. 6, p. 8.
6. The Day The Earth Nearly Died – 5. 12. 2002 [electronic resource] http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml

Reviews:

12/1/2015, 12:12 Mordashev Vladimir Mikhailovich
Review: The article is devoted to a wide range of problems related to the urgent task of developing gas hydrates - a promising energy resource. Solving these problems will require, among other things, the analysis and synthesis of heterogeneous data from scientific and technological research, which is often disordered and chaotic in nature. Therefore, the reviewer recommends that in their future work the authors pay attention to the article “Empiricism for Chaos”, website, No. 24, 2015, p. 124-128. The article “Problems of Gas Hydrate Development” is of undoubted interest to a wide range of specialists and should be published.

12/18/2015 2:02 Reply to the author’s review Polina Robertovna Kurikova:
I have read the article and will use these recommendations when further developing the topic and solving the problems covered. Thank you.

Gas hydrates (also natural gas hydrates or clathrates) are crystalline compounds formed under certain thermobaric conditions from water and gas. The name “clathrates” (from the Latin clathratus - “to put in a cage”) was given by Powell in 1948. Gas hydrates are non-stoichiometric compounds, that is, compounds of variable composition.

Gas hydrates (sulfur dioxide and chlorine) were first observed at the end of the 18th century by J. Priestley, B. Peletier and V. Carsten. The first descriptions of gas hydrates were given by G. Davy in 1810 (chlorine hydrate). In 1823, Faraday approximately determined the composition of chlorine hydrate, in 1829 Levit discovered bromine hydrate, and in 1840 Wöhler obtained H2S hydrate. By 1888, P. Villar obtained the hydrates CH4, C2H6, C2H4, C2H2 and N2O.

In the 1940s, Soviet scientists hypothesized the presence of gas hydrate deposits in the permafrost zone (Strizhov, Mokhnatkin, Chersky). In the 1960s, they discovered the first deposits of gas hydrates in the north of the USSR, at the same time the possibility of the formation and existence of hydrates in natural conditions was confirmed in the laboratory (Makogon).

From this point on, gas hydrates begin to be considered as a potential source of fuel.
According to various estimates, hydrocarbon reserves in hydrates range from 1.8×10^14 to 7.6×10^18 m³.
Their wide distribution in the oceans and permafrost zone of continents, instability with increasing temperature and decreasing pressure are revealed.

In 1969, the development of the Messoyakha field in Siberia began, where it is believed that for the first time it was possible (by pure chance) to extract natural gas directly from hydrates (up to 36% of total production as of 1990).

Gas hydrates in nature
Most natural gases (CH4, C2H6, C3H8, CO2, N2, H2S, isobutane, etc.) form hydrates, which exist under certain thermobaric conditions. The area of ​​their existence is confined to sea bottom sediments and to areas of permafrost. The predominant natural gas hydrates are methane and carbon dioxide hydrates.

During gas production, hydrates can form in well bores, industrial communications and main gas pipelines. By depositing on the walls of pipes, hydrates sharply reduce their throughput. To combat the formation of hydrates in gas fields, various inhibitors (methyl alcohol, glycols, 30% CaCl2 solution) are introduced into wells and pipelines, and the temperature of the gas flow is maintained above the temperature of hydrate formation using heaters, thermal insulation of pipelines and selection of an operating mode that ensures maximum gas flow temperature. To prevent hydrate formation in main gas pipelines, gas drying is the most effective - cleaning gas from water vapor.

Problems and prospects associated with natural gas hydrates
From the very beginning, the development of fields in the north of Western Siberia faced the problem of gas emissions from shallow intervals of the permafrost zone. These releases occurred suddenly and led to work stoppages at wells and even fires. Since the emissions occurred from the depth interval above the gas hydrate stability zone, for a long time they were explained by gas flows from deeper productive horizons through permeable zones and neighboring wells with poor-quality casing. At the end of the 80s, based on experimental modeling and laboratory studies of frozen core from the permafrost zone of the Yamburg gas condensate field, it was possible to identify the distribution of dispersed relict (preserved) hydrates in Quaternary sediments. These hydrates, together with local accumulations of microbial gas, can form gas-bearing layers from which emissions occur during drilling. The presence of relict hydrates in the shallow layers of the permafrost zone was further confirmed by similar studies in northern Canada and in the area of ​​the Bovanenkovo ​​gas condensate field. Thus, ideas have been formed about a new type of gas deposits - intrapermafrost metastable gas-gas-hydrate deposits, which, as shown by tests of permafrost wells at the Bovanenkovskoye gas condensate field, represent not only a complicating factor, but also a certain resource base for local gas supply.

Intra-permafrost deposits contain only a small part of the gas resources that are associated with natural gas hydrates. The main part of the resources is confined to the gas hydrate stability zone - that depth interval (usually the first hundreds of meters) where the thermodynamic conditions for hydrate formation occur. In the north of Western Siberia this is a depth interval of 250-800 m, in the seas - from the bottom surface to 300-400 m, in especially deep-water areas of the shelf and continental slope up to 500-600 m below the bottom. It was in these intervals that the bulk of natural gas hydrates were discovered.

During the study of natural gas hydrates, it became clear that it is not possible to distinguish hydrate-containing deposits from frozen deposits using modern means of field and borehole geophysics. The properties of frozen rocks are almost completely similar to those of hydrate-containing rocks. A nuclear magnetic resonance logging device can provide certain information about the presence of gas hydrates, but it is very expensive and is used extremely rarely in geological exploration practice. The main indicator of the presence of hydrates in sediments is core studies, where hydrates are either visible by visual inspection or determined by measuring the specific gas content during thawing.

Prospects for the use of gas hydrate technologies in industry
Technological proposals for the storage and transport of natural gas in a hydrated state appeared back in the 40s of the 20th century. The property of gas hydrates to concentrate significant volumes of gas at relatively low pressures has attracted the attention of specialists for a long time. Preliminary economic calculations have shown that sea transport of gas in the hydrated state is the most effective, and additional economic benefits can be achieved by simultaneously selling to consumers the transported gas and clean water remaining after the decomposition of the hydrate (when gas hydrates are formed, the water is cleared of impurities). Currently, the concepts of sea transport of natural gas in the hydrated state under equilibrium conditions are being considered, especially when planning the development of deep-sea gas (including hydrate) fields remote from the consumer.

However, in recent years, increasing attention has been paid to the transport of hydrates under nonequilibrium conditions (at atmospheric pressure). Another aspect of the use of gas hydrate technologies is the possibility of organizing gas hydrate gas storage facilities in equilibrium conditions (under pressure) near large gas consumers. This is due to the ability of hydrates to concentrate gas at relatively low pressure. So, for example, at a temperature of +4°C and a pressure of 40 atm, the concentration of methane in the hydrate corresponds to a pressure of 15 - 16 MPa.

The construction of such a storage facility is not complicated: the storage facility is a battery of gas tanks located in a pit or hangar and connected to a gas pipe. In the spring-summer period, the storage facility is filled with gas that forms hydrates; in the autumn-winter period, it releases gas during the decomposition of hydrates using a low-potential heat source. The construction of such storage facilities near thermal power plants can significantly smooth out seasonal unevenness in gas production and represent a real alternative to the construction of underground gas storage facilities in a number of cases.

Currently, gas hydrate technologies are being actively developed, in particular, for the production of hydrates using modern methods of intensifying technological processes (surfactant additives that accelerate heat and mass transfer; the use of hydrophobic nanopowders; acoustic influences of various ranges, up to the production of hydrates in shock waves, etc.).

http://ru.wikipedia.org/wiki/Gas_hydrates
http://en.wikipedia.org/wiki/Clathrate_hydrate

Russian Chemical Journal. T. 48, No. 3 2003. “Gas hydrates”
http://www.chem.msu.su/rus/journals/jvho/2003-3/welcome.html
http://www.chem.msu.su/rus/journals/jvho/2003-3/5.pdf

http://www1.eere.energy.gov/vehiclesandfuels/facts/favorites/fcvt_fotw102.html

http://marine.usgs.gov/fact-sheets/gas-hydrates/title.html

Gas Hydrate Studies - a part of the geophysics group

Gas Hydrate Stability Curve

Gas Hydrate Stability in Ocean Sediments

http://woodshole.er.usgs.gov/project-pages/hydrates/what.html

Since the 1970's, naturally occurring gas hydrate, mainly methane hydrate, has been recognized worldwide, where pressure and temperature conditions stabilize the hydrate structure. It is present in oceanic sediments along continental margins and in polar continental settings. It has been identified from borehole samples and by its characteristic responses in seismic-reflection profiles and oil-well electric logs. Beneath the ocean, gas hydrate exists where water depths exceed 300 to 500 meters (depending on temperature), and it can occur within a layer of sediment as much as ~1000 meters thick directly beneath the sea floor; the base of the layer is limited by increasing temperature. At high latitudes, it exists in association with permafrost.

Off the southeastern United States, a small area (only 3000 km2) beneath a ridge formed by rapidly-deposited sediments appears to contain a volume of methane in hydrate that is equivalent to ~30 times the U.S. annual consumption of gas. This area is known as the Blake Ridge. Significant quantities of naturally occurring gas hydrate also have been detected in many regions of the Arctic, including Siberia, the Mackenzie River delta, and the north slope of Alaska.