A mixture of gases formed in the bowels of the earth during the anaerobic decomposition of organic matter.
Natural gas refers to minerals. It is often associated gas in oil production. Natural gas in reservoir conditions (conditions of occurrence in the earth's interior) 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 - it is a free gas, or in a dissolved state in oil or water (in reservoir conditions), and under standard conditions (0.101325 MPa and 20 °C) - only in the gaseous state. Natural gas can also be in the form of gas hydrates.
Chemical composition
The main part of natural gas is methane (CH4) - up to 98%. Natural gas may also contain heavier hydrocarbons: ethane (C2H6),
propane (C3H8),
butane (C4H10)
Methane homologues, as well as other non-hydrocarbon substances: hydrogen (H2),
hydrogen sulfide (H2S),
carbon dioxide (CO2),
nitrogen (N2),
helium (He).
Natural gas is colorless and odorless. In order to be able to detect a leak by smell, a small amount of mercaptans, which have a strong unpleasant odor, are added to the gas.
Physical Properties
indicative physical characteristics:
Density: = 0.7 kg/m (dry gaseous) or 400 kg/m (liquid).
Ignition temperature: t = 650 °C.
Calorific value: 16 – 35 MJ/m (for gaseous).
Octane number when used on combustion engines: 120 - 130.
Natural gas fields
Methane and some other hydrocarbons are widely distributed in space. Methane is the third most abundant gas in the universe, after hydrogen and helium. In the form of methane ice, it is involved in the structure of many distant planets and asteroids, but such accumulations are usually not classified as natural gas deposits, and they have not yet found practical application. A significant amount of hydrocarbons is present in the Earth's mantle, but they are also of no interest.
Huge deposits of natural gas are concentrated in the sedimentary shell of the earth's crust. According to the theory of the biogenic 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 at higher temperatures and pressures than oil. Consistent with this is the fact that gas fields are often deeper than oil fields.
Huge reserves of natural gas are possessed by Russia (Urengoyskoye field), the USA, Canada. Of other European countries, Norway is worth noting, but its reserves are small. Among the former republics Soviet Union Turkmenistan owns large gas reserves, as well as Kazakhstan (Karachaganak field)
In the second half of the 20th century at the University of 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.
Extraction and transportation
Natural gas is found in the ground at depths ranging from 1,000 meters to several kilometers. An ultra-deep well near the city of Novy Urengoy received gas inflow from a depth of more than 6,000 meters. In the bowels of the gas is in microscopic voids called pores. The pores are interconnected by microscopic channels - cracks, through these channels the gas comes from the pores with high pressure into lower pressure pores until it is in the well. The movement of gas in the reservoir obeys certain laws. Gas is extracted from the bowels of the earth using wells. Wells try to place evenly throughout the field. This is done for a uniform drop in reservoir pressure in the reservoir. Otherwise, gas flows between areas of the field are possible, as well as premature flooding of the deposit.
The gas comes out of the bowels due to the fact that in the reservoir it is under pressure many times higher than atmospheric pressure. Thus, driving force is the pressure difference between the reservoir and the collection system.
In 2005, Russia's natural gas production amounted to 548 billion m3. Domestic consumers were supplied with 307 billion m3 through 220 regional gas distribution organizations. There are 24 natural gas storage facilities in Russia. The length of Russia's main gas pipelines is 155,000 km.
Preparation of natural gas for transport
The gas coming from the wells must be prepared for transportation to the end user - a chemical plant, a boiler house, city gas networks. The need for gas preparation is caused by the presence in it, in addition to the target components (different components are targeted for different consumers), impurities that cause difficulties during transportation or use. Thus, vapors of water contained in gas, under certain conditions, can form hydrates or, condensing, accumulate in various places (a bend in a pipeline, for example), interfering with the movement of gas; hydrogen sulfide is highly corrosive gas equipment(pipes, heat exchanger tanks, etc.).
Gas is prepared according to various schemes. According to one of them, a complex gas treatment unit (CGTP) is being built in the immediate vicinity of the field, where gas is cleaned and dried. Such a scheme has been implemented at the Urengoyskoye field.
If the gas contains a large amount of helium or hydrogen sulfide, then the gas is treated at a gas processing plant, where helium and sulfur are isolated. This scheme has been implemented, for example, at the Astrakhan field.
Natural gas transportation
Currently, the main mode of transport is pipeline. Gas under a pressure of 75 atmospheres moves through pipes with a diameter of up to 1.4 meters. As the gas moves through the pipeline, it loses energy, overcoming frictional forces both between the gas and the pipe wall and between the layers of gas. Therefore, at certain intervals, it is necessary to build compressor stations (CS), where the gas is compressed to 75 atm. The construction and maintenance of the pipeline is very expensive, but nevertheless it is the cheapest way to transport gas and oil.
In addition to pipeline transport, special tankers are used - gas carriers. These are special ships on which gas is transported in a liquefied state under certain thermobaric conditions. Thus, in order to transport gas in this way, it is necessary to stretch a gas pipeline to the seashore, build a liquefied gas plant, a port for tankers, and the tankers themselves on the coast. This type of transport is considered economically justified when the distance of the consumer of liquefied gas is more than 3000 km.
In 2004, international gas supplies through pipelines amounted to 502 billion m3, liquefied gas - 178 billion m3.
There are also other gas transportation projects, for example, using airships, or in the gas hydrate state, but these projects have not been widely used due to various reasons.
Application
Natural gas is widely used in the chemical industry as a feedstock. It is also used as a fuel, for heating residential buildings, fuel for cars, power plants, etc.
Top ten gas producing countries
At the beginning of 2007, Russia initiated the process of creating a gas cartel following the example of OPEC. This issue was a key topic in the negotiations between Vladimir Putin and the king Saudi Arabia and Emir of Qatar.
see also
Oil
Marsh gas
Natural gas hydrates
Notes
There is a mixture of methane CH 4 with a small amount of nitrogen N 2 and carbon dioxide CO 2 - that is, that it is qualitatively identical in composition with the gas emitted from swamps.
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Natural gas. How it works?
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Natural gas, wax, fuel oil, gasoline from wood
No. 53. Organic chemistry. Topic 14. Sources of hydrocarbons. Part 1. Natural gas
Subtitles
Chemical composition
The main part of natural gas is methane (CH 4) - from 70 to 98%. The composition of natural gas may include heavier hydrocarbons - methane homologues:
- ethane (C 2 H 6),
- propane (C 3 H 8),
- butane (C 4 H 10).
Natural gas also contains other substances that are not hydrocarbons:
- helium (He) and other inert gases.
Pure natural gas is colorless and odorless. To facilitate the possibility of determining a gas leak, odorants are added to it in a small amount - substances that have a sharp unpleasant odor (rotten cabbage, rotten hay, rotten eggs). The most commonly used odorants are thiols (mercaptans), such as ethyl mercaptan (16 g per 1000 m³ of natural gas).
Physical Properties
Approximate physical characteristics (depending on the composition; under normal conditions, unless otherwise indicated):
Natural gas fields
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 at higher temperatures and pressures than oil. Consistent with this is the fact that gas fields are often deeper than oil fields.
Huge reserves of natural gas are possessed by Russia (Urengoyskoye field), Iran, most of the countries of the Persian Gulf, the USA, Canada. Of the European countries, it is worth noting Norway, the Netherlands. Among the former republics of the Soviet Union, Turkmenistan, Azerbaijan, Uzbekistan, and Kazakhstan (Karachaganak field) own large gas reserves.
Methane and some other hydrocarbons are widely distributed in space. Methane is the third most abundant gas in the universe, after hydrogen and helium. In the form of methane ice, it is involved in the structure of many planets and asteroids distant from the sun, but such accumulations, as a rule, are not classified as natural gas deposits, and they have not yet found practical application. A significant amount of hydrocarbons is present in the Earth's mantle, but they are also of no interest.
Gas hydrates
In science, it has long been believed that accumulations of hydrocarbons with a molecular weight of more than 60 are in the earth's crust in a liquid state, while lighter ones are in a gaseous state. However, in the second half of the 20th century, a group of researchers A. A. Trofimuk, N. V. Chersky, F. A. Trebin, Yu. solid state and form gas hydrate deposits. Later it turned out that the reserves of natural gas in this state are huge.
The gas passes into a solid state in the earth's crust, connecting with formation water at hydrostatic pressures up to 250 atm and relatively low temperatures (up to +22 °C). Gas hydrate deposits have an incomparably higher concentration of gas per unit volume of the porous medium than in ordinary gas deposits, since one volume of water, when it passes into the hydrate state, binds up to 220 volumes of gas. The zones of gas hydrate deposits are concentrated mainly in the areas of permafrost, as well as at a shallow depth under the ocean floor.
Natural gas reserves
Extraction and transportation
Natural gas is found in the ground at depths ranging from 1,000 m to several kilometers. An ultra-deep well near the city of Novy Urengoy received gas inflow from a depth of more than 6,000 meters. In the bowels of the gas is in microscopic voids (pores). The pores are interconnected by microscopic channels - cracks, through these channels the gas flows from the pores with high pressure to the pores with lower pressure until it reaches the well. The movement of gas in a reservoir obeys certain laws.
Gas is extracted from the bowels of the earth with the help of wells. Wells are trying to be placed evenly throughout the field, for a uniform drop in reservoir pressure in the deposit. Otherwise, gas flows between areas of the deposit are possible, as well as premature flooding of the deposit.
Gas comes out of the bowels due to the fact that in the reservoir it is under pressure many times higher than atmospheric pressure. Thus, the driving force is the pressure difference between the reservoir and the collection system.
World natural gas production in 2014 amounted to 3460.6 bcm. The leading position in gas production is occupied by Russia and the United States.
| A country | 2010 | 2006 | ||
| Mining, billion m³ |
Share of world market (%) |
Mining, billion m³ |
Share of world market (%) |
|
| Russia | 647 | 673,46 | 18 | |
| USA | 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 | |||
| Great Britain | 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 | |
Preparation of natural gas for transportation
The gas coming from the wells must be prepared for transportation to the end user - a chemical plant, a boiler house, a thermal power plant, city gas networks. The need for gas preparation is caused by the presence in it, in addition to the target components (different components are targeted for different consumers), also impurities that cause difficulties during transportation or use. Thus, water vapor contained in gas, under certain conditions, can form hydrates or, condensing, accumulate in various places (for example, a bend in a pipeline), interfering with the movement of gas; hydrogen sulfide causes severe corrosion of gas equipment (pipes, heat exchanger tanks, etc.). In addition to preparing the gas itself, it is also necessary to prepare the pipeline. Nitrogen plants are widely used here, which are used to create an inert atmosphere in the pipeline.
Gas is prepared according to various schemes. According to one of them, in the immediate vicinity of the field, a complex gas treatment unit (CGTP) is being built, where gas is cleaned and dried in absorption columns. Such a scheme has been implemented at the Urengoyskoye field. Gas treatment by membrane technology is also expedient.
To prepare gas for transportation, technological solutions are used using membrane gas separation, which can be used to separate heavy hydrocarbons (C 3 H 8 and above), nitrogen, carbon dioxide, hydrogen sulfide, and also significantly reduce the dew point temperature for water and hydrocarbons before being fed into GTS.
If the gas contains a large amount of helium or hydrogen sulfide, then the gas is processed at a gas processing plant, where sulfur is isolated at amine treatment plants and Claus plants, and helium at cryogenic helium plants (CGU). This scheme has been implemented, for example, at the Orenburg field. If the hydrogen sulfide content in the gas is less than 1.5% by volume, then it is also advisable to consider the membrane technology for natural gas treatment, since its use allows to reduce capital and operating costs by 1.5-4 times.
Natural gas transportation
Currently, the main mode of transport is pipeline. Gas at a pressure of 75 atm is pumped through pipes with a diameter of up to 1.42 m. As the gas moves through the pipeline, it, overcoming friction forces both between the gas and the pipe wall and between the layers of gas, loses potential energy, which is dissipated in the form of heat. Therefore, at certain intervals, it is necessary to build compressor stations (CS), in which the gas is usually boosted to a pressure of 55 to 120 atm and then cooled. The construction and maintenance of the pipeline is very expensive, but nevertheless it is the cheapest way to transport gas over short and medium distances in terms of initial investment and organization.
In addition to pipeline transport, special gas carriers are widely used. These are special vessels on which gas is transported in a liquefied state in specialized isothermal tanks at a temperature of -160 to -150 °C.
For liquefaction, the gas is cooled at high blood pressure. At the same time, the compression ratio reaches 600 times, depending on the needs. Thus, to transport gas in this way, it is necessary to stretch a gas pipeline from the field to the nearest sea coast, build a terminal on the coast, which is much cheaper than a conventional port, to liquefy gas and pump it into tankers, and the tankers themselves. The usual capacity of modern tankers is between 150,000 and 250,000 m³. This method of transportation is much more economical than pipeline, starting from distances to the consumer of liquefied gas more than 2000-3000 km, since the main cost is not transportation, but loading and unloading, but requires higher initial investments in infrastructure than pipeline. It also has the advantage of being liquefied gas much safer during transportation and storage than compressed.
Natural gas is a mineral of a group of sedimentary rocks, which is a mixture of gases. This resource arose as a result of the decomposition of organic matter in the bowels of the Earth. Ecologists recognize natural gas as the cleanest type of fossil fuel.
Characteristics and types of natural gas
The characteristic of natural gas depends on its composition. It is lighter than air by 1.8 times, auto-ignition temperature is 650°C. Dry gas has a density of 0.68 kg/m 3 to 0.85 kg/m 3 and liquid 400 kg/m 3 . A mixture of gas and air from 5% to 15% by volume is explosive. Specific heat of combustion from 8-12 kWh/m 3 . When using natural gas in internal combustion engines, the octane number is from 120 to 130.
Most natural gas is a mixture of gaseous hydrocarbons. The main part is methane (CH 4 - up to 98%), as well as heavy hydrocarbons - ethane C 2 H 6, propane C 3 H 8, butane C 4 H 10. The composition also includes other non-carbon substances: hydrogen H 2, hydrogen sulfide H 2 S, carbon dioxide CO 2, nitrogen N 2, helium He.
Pure natural gas is colorless and odorless. To make it easier to determine the location of the leak, odorants, substances with an unpleasant odor, are mixed into it.
Types of natural gas:
- liquefied (SUG);
- marsh;
- oil;
- carbonic;
- gas hydrates;
- slate;
- lighting;
- coke;
- compressed or compressed (CNG);
- associated oil;
- by tiers and sub-tiers of the earthen layer of the Cretaceous period, from where it is mined today - Turonian, Cenomanian, Valanginian, Achimov.
Natural gas field
Basically, natural gas deposits are located in the sedimentary shell of the earth's crust. Huge reserves of natural gas are owned by Russia (Urengoyskoye field), in Europe - by Norway, the Netherlands, most of the Persian Gulf countries, Iran, Canada, the USA, there are large deposits in Azerbaijan, Uzbekistan, Turkmenistan and Kazakhstan. Gas hydrates are present in large quantities at great depths under the seabed, as well as underground.
Natural gas production
Before mining, exploration is first carried out - gravitational, magnetic, seismic or geochemical. However, the only reliable way to find out if there is a supply of gas under you is to drill a well. Natural gas is located at a depth of one kilometer. In the bowels of the Earth, gas is located in microscopic pores, which are interconnected by channels - cracks, through them, under high pressure, this important resource penetrates into the pores more low pressure until it is inside the wells. All this is carried out in accordance with Darcy's law - the filtration of gases and liquids in a porous medium. Gas comes out of the bowels as a result of the fact that in the wells it is under pressure, which is several times higher than atmospheric pressure.
Gas is produced using wells, which are evenly distributed over the entire area of the field. This is done for a uniform drop in reservoir pressure in the deposit. The produced gas is prepared for transportation. Gas is transported by pipelines, special gas carriers, railway tanks.
Use of natural gas
Natural gas is used as a highly economical fuel for power plants, for the cement and glass industries, for ferrous and non-ferrous metallurgy, for the production of building materials, and for the production of various organic compounds. This important resource is used for and for household needs. The source of energy for megacities, motor fuel, paint, glue, vinegar, ammonia - all this we have thanks to natural gas.
Natural gas, the main part of which is methane (92-98%), is by far the most promising alternative fuel for cars. Natural gas can be used as fuel both in compressed (compressed) and liquefied form.
Methane- the simplest hydrocarbon, a colorless gas (under normal conditions) odorless, the chemical formula is CH4. Slightly soluble in water, lighter than air. When used in everyday life, industry, odorants (usually thiols) with a specific "gas smell" are usually added to methane. Methane is non-toxic and harmless to human health.
Extraction and transportation
The gas is located in the bowels of the Earth at a depth of one to several kilometers. Before the start of gas production, it is necessary to carry out geological exploration work, which allows to establish the location of deposits. Gas is produced using wells specially drilled for this purpose in one of the possible ways. Most often, gas is transported through gas pipelines. The total length of gas distribution pipelines in Russia is more than 632 thousand kilometers - this distance is almost 20 times the circumference of the Earth. The length of main gas pipelines in Russia is 162,000 kilometers.
Use of natural gas
The scope of natural gas is quite wide: it is used for space heating, cooking, heating water, the production of paints, glue, acetic acid and fertilizers. In addition, natural gas in compressed or liquefied form can be used as a motor fuel in vehicles, special and agricultural machinery, railway and water transport.
Natural gas - environmentally friendly motor fuel
90% of air pollution comes from vehicles.
Transfer of transport to environmentally friendly motor fuel - natural gas - allows to reduce emissions of soot, highly toxic aromatic hydrocarbons, carbon monoxide, unsaturated hydrocarbons and nitrogen oxides into the atmosphere.
When burning 1000 liters of liquid petroleum motor fuel, 180-300 kg of carbon monoxide, 20-40 kg of hydrocarbons, 25-45 kg of nitrogen oxides are emitted into the air together with exhaust gases. When natural gas is used instead of petroleum fuel, the release of toxic substances into environment decreases approximately 2-3 times for carbon monoxide, for nitrogen oxides - 2 times, for hydrocarbons - 3 times, for smoke - 9 times, and the formation of soot characteristic of diesel engines is absent.
Natural gas - economical motor fuel
Natural gas is the most economical motor fuel. Its processing requires minimal costs. In fact, all that needs to be done with gas before refueling a car is to compress it in a compressor. Today, the average retail price of 1 cubic meter of methane (which in terms of its energy properties is equal to 1 liter of gasoline) is 13 rubles. This is 2-3 times cheaper than gasoline or diesel fuel.
Natural gas is a safe motor fuel
The concentration* and temperature** flammability limits of natural gas are significantly higher than those of gasoline and diesel fuel. Methane is twice as light as air and quickly dissolves into the atmosphere when released.
According to the “Classification of combustible substances according to the degree of sensitivity” of the Ministry of Emergency Situations of Russia, compressed natural gas is classified as the safest, fourth class, and propane-butane - to the second.
* The formation of an explosive concentration occurs when the content of gas vapor in the air is from 5% to 15%. In open space, the formation of an explosive mixture does not occur.
** The lower self-ignition limit of methane is 650°C.
Natural gas - technologically advanced motor fuel
Natural gas does not form deposits in the fuel system, does not wash off the oil film from the cylinder walls, thereby reducing friction and reducing
engine wear.
The combustion of natural gas does not produce solid particles and ash, which cause increased wear of engine cylinders and pistons
Thus, the use of natural gas as a motor fuel makes it possible to increase the service life of the engine by 1.5-2 times.
The table below summarizes a few facts about CNG and LNG:
Natural gas, as we know, can be composed of anything, and often in its original form it is somewhat different from the gas that comes to us through pipelines. It is also clear that differences in the composition of gas from different fields
So, what are the properties of the individual substances that make up natural gas? Let's start with the most common methane. Its formula is CH4. A colorless gas that is lighter than air and has no odor. Therefore, sometimes it is necessary to add various fragrances-perfumes that smell very unpleasant to it: so that gas leakage and leaks in the cylinder are immediately noticeable. Methane has no color. And although methane is highly flammable, it can be stored and transported quite easily.
Next on our list is ethane. Its formula is C2H6. This gas is also odorless and colorless, but slightly heavier than air. Ethane is a combustible gas, but for some reason it cannot be used as a fuel.
But the well-known propane is used as a fuel. Its formula is C3H8. It is a poisonous gas, also without "rings" - smell or color. But propane has one very useful property. It can be liquefied at a relatively low pressure, and this makes it possible to easily separate propane from impurities on an industrial scale and further transport it.
Higher gas density butane. Its formula is C4H10. It is close enough in properties to propane, but it is heavier than air, about twice.
Carbon dioxide, with the well-known formula CO2 (for those who have forgotten chemistry, the formula for carbon monoxide is almost the same - CO). This gas has no smell, no color, but it has a taste - sour. And unlike other constituents of natural gas, carbon dioxide does not undergo combustion. Helium is also non-flammable. By the way, CO2 is considered one of the least dangerous and toxic gases among natural gases.
Helium it is also non-toxic, however, with a slight increase in pressure, it causes a state of anesthesia in humans, like many other inert gases. It is light, and is the second lightest after hydrogen, colorless, tasteless and odorless. As stated above, it is non-flammable. The formula for helium is He.
Another colorless gas, but with a rather pleasant smell in the natural composition, is ethylene. Its formula is C2H4. By their chemical and physical properties it is close enough to ethane, except that its density is less, and therefore combustibility.
Hydrogen sulfide (H2S). A heavy gas, colorless and with a characteristic odor of rotten eggs. Even at the slightest concentration, hydrogen sulfide can cause long-term paralysis of the olfactory nerve. Very poisonous: in slightly large doses it can kill!
And here acetylene with the formula C2H2 is not included in the composition of natural gas, however, it is similar to it in properties. It is extremely flammable and incredibly explosive. It can explode even with stronger compression. Therefore, it is not used in everyday life: the danger of an explosion or fire is too great. But it is used in metal welding.
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