Natural gas is a raw material, not a finished fuel. General information about natural gas
Dead living organisms sank to the bottom of the sea and found themselves in conditions where they could not disintegrate either as a result of oxidation (there is practically no air and oxygen at the bottom of the sea) or under the influence. As a result, these organisms formed muddy sediments.
Under the influence of geological movements, these sediments sank to ever greater depths and penetrated into the bowels of the earth. For millions of years, sediments have been subjected to high pressures and temperatures. As a result of this impact, a process took place in these sediments in which the carbon they contained was converted into compounds called hydrocarbons.
High molecular weight hydrocarbons (with large molecules) are liquid substances. From them oil was formed. But low molecular weight hydrocarbons are gases. It is from the latter that it is formed natural gas. Only higher temperatures and pressures are required to form gas. Therefore, there is always natural gas in an oil field.
Over time, oil and gas deposits went to greater depths. Over millions of years they were covered by sedimentary rocks.
Natural gas is a mixture of gases, not a homogeneous substance. The main part of this mixture, about 98%, is methane gas. In addition to methane, natural gas includes ethane, propane, butane and some non-hydrocarbon elements - hydrogen, nitrogen, carbon dioxide, hydrogen sulfide.
Where is natural gas located?
Natural gas is found in the bowels of the earth at a depth of about 1000 m and deeper. There it fills microscopic voids - pores that are connected by cracks. Through these cracks, gas in the ground can move from the pores with high pressure into pores with low
Gas can also be located in the form of a gas cap above an oil field. In addition, it can also be in a dissolved state - in oil or water. Pure natural gas is colorless and odorless.
Gas production and transportation
Gas is extracted from the ground using wells. Due to the fact that the pressure is greater at depth, gas escapes from the wells through the pipe.
To facilitate transportation and storage, natural gas is liquefied by low temperatures at high blood pressure. Methane and ethane cannot exist in liquid state, so the gas is separated. As a result, only a mixture of propane and heavier hydrocarbons is transported in cylinders.
Natural gas is a mixture of gases that are formed in the bowels of the earth during the decomposition of various organic matter. Of course, the composition of natural gas should be determined adjusted for specific samples. However, all natural gases undoubtedly have many common substances and chemical elements in structure, and any natural gas has approximately the same physical composition and properties as others. This is what we will talk about.
General information
Natural gas is one of the most important minerals actively used in industry and in everyday life. Under in situ conditions (or, as gas workers say, in reservoir conditions), natural gas is found exclusively in a gaseous state, either in the form of a so-called “gas cap” in general oil and gas fields, or in the form of gas deposits (that is, individual accumulations), either in dissolved form - in water or oil. True, under certain conditions, natural gas can be found not only in a gaseous state, but also in a solid state in the form of crystals.
Chemical composition of natural gas
As for the main substances that make up natural gas, they are methane (CH 4), carbon dioxide (CO 2) and nitrogen molecules (N 2). Almost any natural gas, whether mine or swamp, consists of these substances and elements. As for the composition of natural gas in percentage, the main substance included in the composition of natural gas is certainly methane. Its share ranges from 90 to 98%, depending on the gas field. Natural gas also includes substances such as butane, propane, ethane (hydrocarbons, also called methane homologues, since they consist of the same chemical elements, differing only in the number of carbon and hydrogen atoms and, accordingly, in the structure of the molecules). Of the non-hydrocarbon components of natural gas, we note, in addition to the already described nitrogen and carbon dioxide (carbon dioxide), hydrogen (H 2), helium (He) and hydrogen sulfide (H 2 S).
Physical properties of natural gas
First of all, we note that natural gas, in its pure form, is colorless and odorless. In order to detect a gas leak, so-called odorants or substances that have a sharp and rather unpleasant odor are added to it in small quantities: for example, thiols, among which ethyl mercaptan occupies a leading place. Usually no more than 15-16 g of ethyl mercaptan is added per 1000 cubic meters of natural gas. The density of natural gas in the gaseous state is on average 0.75 kg per cubic meter. In the crystalline state, the density reaches 400 kg per m 3. Natural gas ignites spontaneously only when very high temperature- about 650 degrees Celsius. At a certain concentration of natural gas in the air (approximately 5-15%) explosions can occur. Also known specific heat combustion of natural gas, averaging 35 MJ/m? or 9 Mcal/m?. When used in various internal combustion engines, the octane rating of natural gas ranges from 120 to 130. Finally, natural gas is approximately 1.8 times lighter than air, so when it leaks, it rises to the top rather than collecting in low areas.
Application of natural gas
First of all, natural gas in modern world used as fuel and fuel. Thus, in many apartment buildings and private buildings, people use natural gas for cooking, heating water, and heating. As for other uses of natural gas as fuel, lately it is actively used not only as fuel for various thermal power plants and boiler houses, but also as fuel for fuel systems some cars. In addition, modern engineers and designers have even launched the production of vehicles powered by natural gas - for example, buses. IN chemical industry Natural gas is used as a raw material for the manufacture of all sorts of substances - for example, various plastics and plastics. And at the dawn of its production in many European and North American cities, natural gas was used as street lighting and it was used even in the very first traffic lights.
Natural gas, which we are all so accustomed to in our kitchens, is a close relative of oil. It consists mostly of methane with admixtures of heavier hydrocarbons (ethane, propane, butane). In natural natural conditions it also often contains impurities of other gases (helium, nitrogen, hydrogen sulfide, carbon dioxide).
Typical composition of natural gas:
Hydrocarbons:
- Methane – 70-98%
- Ethane – 1-10%
- Propane – up to 5%
- Butane – up to 2%
- Pentane – up to 1%
- Hexane – up to 0.5%
Impurities:
- Nitrogen – up to 15%
- Helium – up to 5%
- Carbon dioxide – up to 1%
- Hydrogen sulfide – less than 0.1%
Natural gas is extremely widespread in the depths of the earth. It can be found in the thick earth's crust at depths from a few centimeters to 8 kilometers. Just like oil, natural gas, in the process of migration in the earth's crust, falls into traps (permeable layers limited by impermeable rock layers), resulting in the formation gas fields.
Five largest gas fields in Russia:
- Urengoyskoe (gas)
- Yamburgskoe (oil and gas condensate)
- Bovanenkovskoe (oil and gas condensate)
- Shtokmanovskoe (gas condensate)
- Leningradskoe (gas)
Natural (hydrocarbon) gas is a frequent companion oil fields. It is usually found in oil in dissolved form, and in some cases accumulates in the upper part of fields, forming a so-called gas cap. For a long time, the gas released during oil production, called associated gas, was an undesirable part of the extraction process. Most often it was simply burned in torches.
Only over the past few decades has humanity learned to fully utilize all the benefits of natural gas. This delay in the development of this extremely valuable type of fuel is largely due to the fact that gas transportation and its use in industry and everyday life require a fairly high technical and technological level of development. In addition, natural gas, when mixed with air, forms an explosive mixture, which requires increased safety measures when using it.
Gas Application
Some attempts to use gas were made back in the 19th century. Lamp gas, as it was then called, served as a source of illumination. Gas fields were not yet being developed at that time, and gas produced along with oil was used for lighting. Therefore, such gas was often called petroleum gas. Such petroleum gas, for example, for a long time Kazan was illuminated. It was also used to illuminate St. Petersburg and Moscow.
Currently, gas plays an increasingly significant role in the world's energy sector. The range of its application is very wide. It is used in industry, in everyday life, in boiler houses, thermal power plants, as motor fuel for cars and as a feedstock in the chemical industry.
Gas is considered a relatively clean fuel. When gas is burned, only carbon dioxide and water are produced. At the same time, carbon dioxide emissions are almost two times less than when burning coal and 1.3 times less than when burning oil. Not to mention the fact that when oil and coal are burned, soot and ash remain. Due to the fact that gas is the most environmentally friendly of all fossil fuels, it occupies a dominant position in the energy sector of modern megacities.
How gas is produced
Just like oil, natural gas is produced using wells that are distributed evenly throughout the entire area of the gas field. Production occurs due to the difference in pressure in the gas-bearing formation and on the surface. Under the influence of reservoir pressure, gas is pushed through the wells to the surface, where it enters the collection system. Next, the gas is supplied to a complex gas treatment plant, where it is purified from impurities. If the amount of impurities in the produced gas is insignificant, then it can be immediately sent to a gas processing plant, bypassing the complex treatment plant.
How is gas transported?
Gas is transported primarily through pipelines. The main volumes of gas are transported by main gas pipelines, where gas pressure can reach 118 atm. Gas reaches consumers through distribution and in-house gas pipelines. First, the gas passes through a gas distribution station, where its pressure is reduced to 12 atm. Then it is supplied through gas distribution pipelines to gas control points, where its pressure is again reduced, this time to 0.3 atm. After that, the gas reaches our kitchen through gas pipelines inside the house.
This entire huge gas distribution infrastructure is truly a big picture. Hundreds and hundreds of thousands of kilometers of gas pipelines, entangling almost the entire territory of Russia. If this entire web of gas pipelines is stretched into one line, then its length will be enough to reach from the Earth to the Moon and back. And this is only the Russian gas transportation system. If we talk about the entire global gas transportation infrastructure, then we will be talking about millions of kilometers of pipelines.
Since natural gas has neither odor nor color, in order to quickly detect gas leaks, it is artificially given bad smell. This process is called odorization and occurs at gas distribution stations. Sulfur-containing compounds, such as ethanethiol (EtSH), are usually used as odorants, that is, unpleasant-smelling substances.
Gas consumption is seasonal. In winter, its consumption increases, and in summer it decreases. To smooth out seasonal fluctuations in gas consumption, underground gas storage facilities (UGS) are being created near large industrial centers. These may be depleted gas fields, adapted for gas storage, or artificially created underground salt caves. In summer, excess transported gas is sent to underground gas storage facilities, and in winter, on the contrary, a possible lack of pipeline system capacity is compensated by taking gas from storage facilities.
In world practice, in addition to gas pipelines, natural gas is often transported in liquefied form through special vessels - gas carriers (methane carriers). In liquefied form, the volume of natural gas is reduced by 600 times, which is convenient not only for transportation, but also for storage. To liquefy the gas, it is cooled to its condensation temperature (-161.5 °C), causing it to turn into a liquid. It is transported in this chilled form. The main producers of liquefied natural gas are Qatar, Indonesia, Malaysia, Australia and Nigeria.
Prospects and trends
Due to its environmental friendliness and the constant improvement of equipment and technologies, both in the production and use of gas, this type of fuel is becoming increasingly popular. BP, for example, predicts faster growth in demand for gas compared to other types of fossil fuels.
The growing demand for gas leads to the search for new, often unconventional, sources of gas. Such sources may be:
- Gas from coal seams
- Shale gas
- Gas hydrates
♦ Gas from coal seams Mining began only in the late 1980s. This was first done in the USA, where the commercial viability of this type of mining was proven. In Russia, Gazprom began testing this method in 2003, starting trial production of methane from coal seams in Kuzbass. Gas production from coal seams is also carried out in other countries - Australia, Canada and China.
♦ Shale gas. The shale revolution in gas production that occurred in the United States in last decade, does not leave the front pages of periodicals. The development of horizontal drilling technology has made it possible to extract gas from low-permeability shale in volumes that cover the costs of its extraction. The phenomenon of rapid development of mining shale gas in the USA spurs other countries to develop this direction. In addition to the United States, active work on shale gas production is underway in Canada. China also has significant potential for developing large-scale shale gas production.
♦ Gas hydrates. A significant part of natural gas is in a crystalline state in the form of so-called gas hydrates (methane hydrates). Large reserves of gas hydrates exist in the oceans and in permafrost zones of continents. Currently, estimated gas reserves in the form of gas hydrates exceed the combined reserves of oil, coal and conventional gas. The development of economically feasible technologies for the extraction of gas hydrates is being intensively pursued in Japan, the USA and some other countries. Japan, which is deprived of traditional gas reserves and is forced to purchase this type of resource at extremely high prices, pays particular attention to this topic.
Natural gas has a great future as a fuel and source of chemical elements. In the long term, it is considered as the main type of fuel that will be used during the transition of the world energy sector to cleaner, renewable resources.
Natural gas combustion
Natural gas is a mineral in a gaseous state. It is used very widely as a fuel. But natural gas itself is not used as a fuel; its components are separated from it for separate use. It is often an associated gas during oil production. Natural gas in reservoir conditions (conditions of occurrence in the bowels of the earth) is in a gaseous state in the form of separate accumulations (gas deposits) or in the form of a gas cap of oil and gas fields - this is free gas; either in a dissolved state in oil or water (in reservoir conditions), and in standard conditions- only in gas state. Natural gas can also be in the form of gas hydrates.
Almost 90% of it consists of hydrocarbons, mainly methane (CH 4). It also contains heavier hydrocarbons - ethane, propane, butane, as well as mercaptans and hydrogen sulfide (usually these impurities are harmful), nitrogen and carbon dioxide (they are basically useless, but not harmful), water vapor, beneficial impurities of helium and other inert substances gases
Chemical composition
The main part of natural gas is methane (CH 4) - up to 98%. Natural gas may also contain heavier hydrocarbons - homologues of methane:
- ethane (C 2 H 6),
- propane (C 3 H 8),
- butane (C 4 H 10),
- and other alkanes - from C 5 and above
As well as other non-hydrocarbon substances:
- A more thorough analysis made it possible to detect small amounts of helium (He) in natural gas.
Physical properties
Approximate physical characteristics(depending on the composition):
- Density:
- from 0.7 to 1.0 kg/m 3 - dry gaseous, at n. u.
- 400 kg/m 3 - liquid.
- Heat of combustion of one m 3 of natural gas in a gaseous state at normal conditions: 28-46 MJ, or 6.7-11.0 Mcal.
- Octane number when used in internal combustion engines: 120-130.
- The concentration limits of ignition (explosion) of natural gas (methane) are in the range from 5 to 15%. Outside these boundaries, the gas-air mixture is not capable of spreading flame. During an explosion, the pressure in a closed volume rises to 0.8... 1 MPa.
- Pure natural gas is colorless and odorless. To be able to detect a leak by smell, a small amount of odorants (most often ethyl mercaptan is used as an odorant) that have a strong unpleasant odor are added to the gas; these are odorants.
- Natural gas quickly evaporates and disperses into the atmosphere, which is important from a safety point of view.
Natural gas reserves
Map of natural gas reserves in the world
Methane and some other hydrocarbons are widespread in space. Methane- the third most common gas in the universe, after hydrogen and helium. In the form of methane ice, it participates in the structure of many planets and asteroids far from the sun, but such accumulations, as a rule, are not classified as natural gas deposits, and they have not yet been found practical application. A significant amount of hydrocarbons is present in the Earth's mantle, but they are also not of interest.
Huge deposits of natural gas are concentrated in the sedimentary shell of the earth's crust. According to the theory of the biogenic (organic) origin of oil, they are formed as a result of the decomposition of the remains of living organisms. It is believed that natural gas is formed in the sedimentary shell when high temperatures and pressures than oil. Consistent with this is the fact that gas fields are often located deeper than oil fields.
Russia (Urengoyskoye field), USA, Canada have huge reserves of natural gas. From others European countries Norway is worth noting, but its reserves are small. Among former republics Soviet Union Turkmenistan, as well as Kazakhstan (Karachaganak field), own large gas reserves.
In the second half of the 20th century at the University. I.M. Gubkin discovered natural gas hydrates (or methane hydrates). Later it turned out that the reserves of natural gas in this state are huge. They are located both underground and in a slight depression under the seabed.
| Country | 2010 | 2006 | ||
| Extraction, billion cubic meters | Share of world market (%) | Extraction, billion cubic meters | Share of world market (%) |
|
| Russian Federation | 647 | 673,46 | 18 | |
| United States of America | 619 | 667 | 18 | |
| Canada | 158 | |||
| Iran | 152 | 170 | 5 | |
| Norway | 110 | 143 | 4 | |
| China | 98 | |||
| Netherlands | 89 | 77,67 | 2,1 | |
| Indonesia | 82 | 88,1 | 2,4 | |
| Saudi Arabia | 77 | 85,7 | 2,3 | |
| Algeria | 68 | 171,3 | 5 | |
| Uzbekistan | 65 | |||
| Turkmenistan | 66,2 | 1,8 | ||
| Egypt | 63 | |||
| United Kingdom | 60 | |||
| Malaysia | 59 | 69,9 | 1,9 | |
| India | 53 | |||
| UAE | 52 | |||
| Mexico | 50 | |||
| Azerbaijan | 41 | 1,1 | ||
| Other countries | 1440,17 | 38,4 | ||
| World gas production | 100 | 3646 | 100 | |
Natural gas production and processing
Gas fields
An oil or gas reservoir is an accumulation of hydrocarbons that fill the pores of permeable rocks. If the accumulation is large and its exploitation is economically feasible, the deposit is considered industrial. Deposits occupying significant areas form deposits.
Gas drying
The moisture content of gas during its transportation often causes serious operational difficulties. Under certain external conditions(temperature and pressure), moisture can condense, form ice plugs and crystalline hydrates, and in the presence of hydrogen sulfide and oxygen cause corrosion of pipelines and equipment. To avoid these difficulties, the gas is dried by reducing the dew point temperature by 5...7 °C below the operating temperature in the gas pipeline.
Gas purification from hydrogen sulfide and carbon dioxide
In flammable gases used for gas supply to cities, the hydrogen sulfide content should not exceed 2 g per 100 m 3 of gas. There are no norms limiting the carbon dioxide content, but for technical and economic reasons in the transported gas it should not exceed 2%.
Gas odorization
Natural gas is odorless. Therefore, in order to detect gas leaks in a timely manner, they give it a smell - the gas is odorized. Ethyl mercaptan (C 2 H 5 SH) is used as an odorant. In terms of toxicity, it is qualitatively and quantitatively identical to hydrogen sulfide and has a sharp, unpleasant odor.
Transportation
The main type of gas transport currently is pipeline. Gas moves through large diameter pipes under a pressure of 75 atmospheres (7.5 MPa). As gas moves through the pipeline, it loses energy; it is spent on overcoming the frictional force both between the pipe wall and the gas, and between the layers of the gas itself. In order for the pressure in the pipeline to be maintained at a given level, it is necessary to have compressor stations (CS) at a certain distance from each other, which must maintain the pressure in the pipeline at a level of 75 atmospheres. Maintaining and constructing a pipeline costs a lot of money, but, nevertheless, the pipeline is the cheapest way to transport oil and gas.
Another way to transport gas is to use special tankers - gas carriers. These are specially equipped ships for transporting gas in a liquefied state under certain conditions. To transport gas using this method, it is necessary, in addition to the tankers themselves, to carry out a number of preparatory measures to enable their use. It is necessary to extend a gas pipeline to the seashore, build a port for tankers, a gas liquefaction plant, and the tankers themselves. However, this type of gas transportation is economically feasible when the consumer is more than 3,000 km away from the production sites.
Natural gas synthesis
There are many ways to obtain natural gas from other organic substances, such as agricultural waste, wood processing and food industry etc.
A mixture of hydrocarbons, a subject of religious cult, scientific dispute and the most important raw material resource. It is invisible and odorless. There is more of it in Russia than anywhere else in the world.
What does natural gas consist of?
The basis of natural gas is methane (CH 4) - the simplest hydrocarbon ( organic compound, consisting of carbon and hydrogen atoms). Usually it also contains heavier hydrocarbons, homologues of methane: ethane (C 2 H 6), propane (C 3 H 8), butane (C 4 H 10) and some non-hydrocarbon impurities.
Natural gas can exist in the form of gas deposits located in certain rock layers, in the form of gas caps (above oil), and also in dissolved or crystalline form.
Smell of gas
Interestingly, none of these gases have either color or odor. The characteristic unpleasant odor, which almost every person has encountered in everyday life, is artificially given to gas and is called odorization. Sulfur-containing compounds are usually used as odorants, that is, unpleasant-smelling substances. A person can smell one of the most common odorants - ethanethiol - even if one part of this substance is in 50 million parts of air. It is thanks to odorization that gas leaks can be easily identified.
Odorant addition step
with an unpleasant odor.
Odorless natural gas
Natural gas
with an unpleasant odor
Scientists' dispute
There is still no consensus among scientists regarding the origin of natural gas (as well as oil). Two main concepts - biogenic and mineral - claim various reasons formation of hydrocarbon minerals in the bowels of the Earth.
Mineral theory
The formation of minerals in rock layers is part of the process of degassing the Earth. Due to the Earth's internal dynamics, hydrocarbons located on great depths, rise to the zone of lowest pressure, resulting in gas and oil deposits.
Biogenic theory
Living organisms that died and sank to the bottom of reservoirs decomposed in airless space. Sinking deeper and deeper due to geological movements, the remains of decomposed organic matter were transformed under the influence of thermobaric factors (temperature and pressure) into hydrocarbon minerals, including natural gas.
Invisible pores
Quite common misrepresentation that the gas is located underground in certain voids, from which it is easily completely extracted. In fact, there may be gas inside rock, which has a porous structure so fine that it cannot be seen by the human eye. Holding in his hands a piece of sandstone extracted from enormous depth, it is quite difficult to imagine that natural gas is contained inside.
Gas Worship
Humanity has known about the existence of natural gas for a long time. And, although already in the 4th century BC. e. in China they learned to use it for heating and lighting; for a long time, a bright flame that leaves no ashes was the subject of a mystical and religious cult for some peoples. For example, on the Absheron Peninsula (modern territory of Azerbaijan) in the 7th century, the temple of fire worshipers Ateshgah was erected, services in which took place until the 19th century.
By the way, not far from the Ateshgah temple in 1859, the first attempt in Russia (rather short-lived) to use natural gas for industrial purposes was made - at an oil refinery in Baku.
Thermal lamp and the first gas in Russia
The history of the Russian gas industry begins in 1811. Then the inventor Pyotr Sobolevsky created the first installation for producing artificial gas - thermal lamps. Having made a report on this at a meeting of the All-Russian Society of Lovers of Literature, Sciences and Arts, by decree of Alexander I, Sobolevsky was awarded an order for his invention. A few years later, in 1819, the first gas lamps were lit on Aptekarsky Island in St. Petersburg. Thus, the history of the gas industry in Russia began almost 200 years ago - in 2011 it celebrated its anniversary.
In the mid-20s of the 20th century, 227.7 million cubic meters of gas were produced throughout the USSR. In 2010, the Gazprom Group produced 508.6 billion cubic meters of gas.
Russia ranks first in the world in terms of natural gas reserves. Gazprom's share in these reserves is about 70%. Thus, Gazprom has the world's richest natural gas reserves.
With the advent of the 20th century it began active development Russian gas industry: gas fields were developed for the first time, associated (petroleum) gas was utilized.
Russian ingenuity
However, until the 20th century in Russia, natural gas was a by-product of oil production and was called associated gas. Even the very concepts of gas or gas condensate fields did not exist. They were discovered by chance, for example, when drilling artesian wells. However, there is a known case when, while drilling such a well, a resourceful Saratov merchant, seeing a flame instead of water, built a glass and brick factories. Industrialists gradually began to realize that natural gas could be extremely useful.