INTRODUCTION
1.1 General provisions
1.1.1 The course project (gas supply to the village of Kinzebulatovo) was developed on the basis of the general plan of the settlement.
1.1.2 When developing the project, the requirements of the main regulatory documents are taken into account:
– updated version of SNiP 42-01 2002 “Gas distribution networks”.
– SP 42-101 2003 “General provisions for the design and construction of gas distribution systems made of metal and polyethylene pipes.”
– GOST R 54-960-2012 “Block gas control points. Gas reduction points are cabinet-mounted.”
1.2 General information about the locality
1.2.1 There are no industrial or municipal enterprises on the territory of the settlement.
1.2.2 The settlement is built up with one-story buildings. The settlement does not have centralized heating or centralized hot water supply.
1.2.3 Gas distribution systems throughout the territory of the populated area are made underground from steel pipes. Modern gas distribution systems are a complex set of structures consisting of the following main elements of gas ring, dead-end and mixed networks of low, medium, high pressure, laid in the territory of a city or other populated area inside blocks and inside buildings, on mainlines - on mainlines of gas control stations (GRS).
CHARACTERISTICS OF THE CONSTRUCTION AREA
2.1 General information about the locality
Kinzebulatovo, Kinzebulat(bashk. Kinyebulat) - a village in the Ishimbaysky district of the Republic of Bashkortostan, Russia.
Administrative center of the rural settlement "Bayguzinsky Village Council".
The population is about 1 thousand people. Kinzebulatovo is located 15 km from the nearest city - Ishimbay - and 165 km from the capital of Bashkortostan - Ufa.
It consists of two parts - a Bashkir village and a former oil workers’ village.
The Tairuk River flows.
There is also the Kinzebulatovskoye oil field.
Agribusiness - Association of Peasant Farms "Udarnik"
CALCULATION OF CHARACTERISTICS OF NATURAL GAS COMPOSITION
3.1 Features of gas fuel
3.1.1 Natural gas has a number of advantages compared to other types of fuel:
– low cost;
– high heat of combustion;
– transportation of gas through main gas pipelines over long distances;
– complete combustion facilitates the working conditions of personnel and maintenance gas equipment and networks,
– the absence of carbon monoxide in the gas, which makes it possible to avoid poisoning in the event of a leak;
– gas supply to cities and towns significantly improves the condition of their air basin;
– the ability to automate combustion processes to achieve high efficiency;
– less emission of harmful substances during combustion than when burning solid or liquid fuels.
3.1.2. Natural gas fuel consists of combustible and non-combustible components. The larger the combustible part of the fuel, the greater the specific heat of combustion. The combustible part or organic mass includes organic compounds, which include carbon, hydrogen, oxygen, nitrogen, and sulfur. The non-combustible part consists of the room and moisture. The main components of natural gas are methane CH 4 from 86 to 95%, heavy hydrocarbons C m H n (4-9%), ballast impurities are nitrogen and carbon dioxide. The methane content in natural gases reaches 98%. The gas has neither color nor odor, so it is odorized. Natural flammable gases according to GOST 5542-87 and GOST 22667-87 consist mainly of methane hydrocarbons.
3.2 Combustible gases used for gas supply. Physical properties of gas.
3.2.1 Natural artificial gases are used for gas supply in accordance with GOST 5542-87; the content of harmful impurities in 1 g/100 m 3 of gas should not exceed:
– hydrogen sulfide – 2g;
– ammonia – 2g;
– cyanide compounds – 5;
– resin and dust – 0.1g;
– naphthalene – 10g. in summer and 5g. in winter.
– gases are clean gas fields. Consist mainly of methane, are dry or lean (no more than 50 g/m3 of propane and above);
– associated gases from oil fields contain a large amount of hydrocarbons, usually 150 g/m 3, are rich gases, a mixture of dry gas, propane - butane fraction and gas gasoline.
– gases of condensate deposits, this is a mixture of dry gas and condensate. Condensate vapor is a mixture of heavy hydrocarbon vapors (gasoline, naphtha, kerosene).
3.2.3. The calorific value of gas, pure gas fields, is from 31,000 to 38,000 kJ/m 3 , and associated gases of oil fields are from 38,000 to 63,000 kJ/m 3 .
3.3 Calculation of the composition of natural gas from the Proletarskoye field
Table 1-Composition of gas from the Proletarskoye field
3.3.1 Lower calorific value and density of natural gas components.
3.3.2 Calculation of the calorific value of natural gas:
0.01(35.84* CH 4 + 63.37 * C 2 H 6 + 93.37 * C 3 H 8 + 123.77 * C 4 H 10 + 146.37 * C 5 H 12), (1 )
0.01 * (35.84 * 86.7+ 63.37 * 5.3+ 93.37 * 2.4 + 123.77 * 2.0+ 146.37 * 1.5) = 41.34 MJ /m 3.
3.3.3 Determination of gas fuel density:
Gas = 0.01(0.72 * CH 4 + 1.35 * C 2 H 6 + 2.02 * C 3 H 8 + 2.7 * C 4 H 10 + 3.2 * C 5 H 12 +1.997 *C0 2 +1.25*N 2); (2)
Gaza = 0.01 * (0.72 * 86.7 + 1.35 * 5.3 + 2.02 * 2.4 + 2.7 * 2.0 + 3.2 * 1.5 + 1.997 * 0 .6 +1.25 * 1.5)= 1.08 kg/N 3
3.3.4 Determination of the relative density of gas fuel:
where air is 1.21–1.35 kg/m3;
ρ rel 
, (3)
3.3.5 Determining the amount of air required for combustion of 1 m 3 of gas theoretically:
[(0.5СО + 0.5Н 2 + 1.5H 2 S + ∑ (m +) С m H n) – 0 2 ]; (4)
V = ((1 + )86.7 + (2 + )5.3 +(3 + )2.4 +(4 + )2.0 +(5 + )1.5 = 10.9 m 3 /m 3;
V = = 1.05 * 10.9 = 11.45 m 3 / m 3.
3.3.6 We summarize the characteristics of gas fuel determined by calculation in Table 2.
Table 2 - Characteristics of gas fuel
| Q MJ/m 3 | Gas P kg/N 3 | R rel. kg/m 3 | V m 3 / m 3 | V m 3 / m 3 |
| 41,34 | 1,08 | 0,89 | 10,9 | 11,45 |
ROUTING OF GAS PIPELINE
4.1 Classification of gas pipelines
4.1.1 Gas pipelines laid in cities and towns are classified according to the following indicators:
– by type of transported natural, associated, petroleum, liquefied hydrocarbon, artificial, mixed gas;
– by gas pressure of low, medium and high (category I and category II); – by field relative to land: underground (underwater), aboveground (overwater);
– by location in the planning system of cities and towns, external and internal;
– according to the construction principle (gas distribution pipelines): looped, dead-end, mixed;
– according to the material of the pipes: metallic, non-metallic.
4.2 Selection of gas pipeline route
4.2.1 The gas distribution system can be reliable and economical when making the right choice routes for laying gas pipelines. The choice of route is influenced by the following conditions: distance to gas consumers, direction and width of passages, type of road surface, presence of various structures and obstacles along the route, terrain, layout
blocks. Gas pipeline routes are selected taking into account the shortest route for gas transportation.
4.2.2 Inlets are laid from street gas pipelines into each building. In urban areas with a new layout, gas pipelines are located inside the blocks. When routing gas pipelines, it is necessary to maintain the distance of gas pipelines from other structures. It is allowed to lay two or more gas pipelines in one trench at the same or different levels (in steps). In this case, the clear distance between gas pipelines should be sufficient for installation and repair of pipelines.
4.3 Basic principles when laying gas pipelines
4.3.1 Gas pipelines should be laid at a depth of at least 0.8 m to the top of the gas pipeline or casing. In those places where the movement of transport and agricultural machinery is not provided, the depth of laying steel gas pipelines is allowed to be at least 0.6 m. In landslide and erosion-prone areas, the laying of gas pipelines should be provided to a depth of at least 0.5 m below the slip surface and below the predicted boundary destruction site. In justified cases, it is allowed to lay gas pipelines on land along the walls of buildings inside residential courtyards and neighborhoods, as well as on white sections of the route, including sections of crossings through artificial and natural barriers when crossing underground communications.
4.3.2 Above-ground and above-ground gas pipelines with embankment can be laid in rocky, permafrost soils, in wetlands and other difficult soil conditions. The material and dimensions of the embankment should be taken based on thermal engineering calculations, as well as ensuring the stability of the gas pipeline and embankment.
4.3.3 Laying gas pipelines in tunnels, collectors and canals is not permitted. Exceptions are the laying of steel gas pipelines with a pressure of up to 0.6 MPa on the territory of industrial enterprises, as well as channels in permafrost soils under roads and railways.
4.3.4 Pipe connections should be permanent. Connections between steel pipes and polyethylene pipes can also be detachable in places where fittings, equipment and instrumentation are installed. Detachable connections of polyethylene pipes with steel pipes in the ground can only be provided if a case with a control tube is installed.
4.3.5 Gas pipelines at the points of entry and exit from the ground, as well as gas pipeline entries into buildings should be enclosed in a case. The space between the wall and the case should be sealed to the full thickness of the structure being crossed. The ends of the case should be sealed with elastic material. Gas pipeline entries into buildings should be provided directly to the room where the gas-using equipment is installed, or to adjacent rooms connected by a covered opening. It is not allowed to enter gas pipelines into the premises of the basement and ground floors of buildings, except for the introduction of natural gas pipelines into single-family and blocked houses.
4.3.6 A shut-off device on gas pipelines should be provided:
– in front of detached blocked buildings;
– to disconnect the risers of residential buildings above five floors;
– in front of outdoor gas-using equipment;
– in front of gas control points, with the exception of the gas distribution center of the enterprise, on the gas pipeline branch to which there is a shut-off device at a distance of less than 100 m from the gas distribution center;
– at the exit from gas control points, with looped gas pipelines;
– on branches of gas pipelines to settlements, individual microdistricts, blocks, groups of residential buildings, and when the number of apartments is more than 400, to individual houses, as well as on branches to industrial consumers and boiler houses;
– when crossing water barriers with two lines or more, as well as with one line when the width of the water barrier at a low-water horizon is 75 m or more;
- when crossing railways of the general network and highways of categories 1–2, if the shut-off device ensures that the gas supply is stopped at the crossing section, located at a distance from the roads of more than 1000 m.
4.3.7 Shut-off devices on above-ground gas pipelines,
laid along the walls of buildings and on supports, should be placed at a distance (in radius) from door and opening window openings of at least:
– for low pressure gas pipelines – 0.5 m;
– for medium pressure gas pipelines – 1 m;
– for high-pressure gas pipelines of the second category – 3 m;
– for high-pressure gas pipelines of the first category – 5 m.
In areas of transit laying of gas pipelines along the walls of buildings, the installation of disconnecting devices is not allowed.
4.3.8 The vertical (clear) distance between the gas pipeline (case) and underground utilities and structures at their intersections should be taken taking into account the requirements of the relevant regulatory documents, but not less than 0.2 m.
4.3.9 At places where gas pipelines intersect with underground communications, collectors and channels for various purposes, as well as at places where gas pipelines pass through the walls of gas wells, the gas pipeline should be laid in a case. The ends of the case must be brought out at a distance of at least 2 m on both sides from the outer walls of the crossed structures and communications, when crossing the walls of gas wells - at a distance of at least 2 cm. The ends of the case must be sealed with waterproofing material. At one end of the case, at the upper points of the slope (with the exception of places where the walls of the wells intersect), a control tube should be provided that extends under the protective device. In the interpipe space of the case and the gas pipeline, it is allowed to lay an operational cable (communications, telemechanics and electrical protection) with a voltage of up to 60V, intended for servicing gas distribution systems.
4.3.10 Polyethylene pipes used for the construction of gas pipelines must have a safety factor in accordance with GOST R 50838 of at least 2.5.
4.3.11 Laying gas pipelines from polyethylene pipes is not allowed:
– on the territory of settlements at pressure above 0.3 MPa;
– outside the territory of settlements at pressure above 0.6 MPa;
– for transporting gases containing aromatic and chlorinated hydrocarbons, as well as the liquid phase of LPG;
– when the temperature of the gas pipeline wall under operating conditions is below –15°C.
When using pipes with a safety factor of at least 2.8, it is permitted to lay polyethylene gas pipelines with pressures above 0.3 to 0.6 MPa in settlement areas with predominantly one- to two-story and cottage residential buildings. In the territory of small rural settlements, it is permitted to lay polyethylene gas pipelines with a pressure of up to 0.6 MPa with a safety factor of at least 2.5. In this case, the laying depth must be at least 0.8 m to the top of the pipe.
4.3.12 Calculation of gas pipelines for strength should include determination of the thickness of the walls of pipes and connecting parts and the stresses in them. At the same time, for underground and above-ground steel gas pipelines, pipes and connecting parts with a wall thickness of at least 3 mm should be used, for above-ground and internal gas pipelines - at least 2 mm.
4.3.13 Characteristics of limit states, safety factors for responsibility, standard and design values of loads and impacts and their combinations, as well as standard and design values of material characteristics should be taken in calculations taking into account the requirements of GOST 27751.
4.3.14 When constructing in areas with complex geological conditions and seismic impacts, special requirements must be taken into account and measures must be taken to ensure the strength, stability and tightness of gas pipelines. Steel gas pipelines must be protected from corrosion.
4.3.15 Underground and above-ground steel gas pipelines, LPG tanks, steel inserts of polyethylene gas pipelines and steel casings on gas pipelines (hereinafter referred to as gas pipelines) should be protected from soil corrosion and stray current corrosion in accordance with the requirements of GOST 9.602.
4.3.16 Steel casings of gas pipelines under roads, railways and tram tracks during trenchless installation (puncture, punching and other technologies permitted for use) should, as a rule, be protected by means of electrical protection (3X3), when laying in an open way - with insulating coatings and 3X3.
4.4 Selecting material for the gas pipeline
4.4.1 For underground gas pipelines, polyethylene and steel pipes. Steel pipes should be used for ground and above-ground gas pipelines. For internal low pressure gas pipelines, it is allowed to use steel and copper pipes.
4.4.2 Steel seamless, welded (straight seam and spiral seam) pipes and connecting parts for gas distribution systems must be made of steel containing no more than 0.25% carbon, 0.056% sulfur and 0.04% phosphorus.
4.4.3 The choice of pipe material, pipeline shut-off valves, connecting parts, welding materials, fasteners and others should be made taking into account the gas pressure, diameter and wall thickness of the gas pipeline, the design temperature of the outside air in the construction area and the temperature of the pipe wall during operation, ground and natural conditions, the presence of vibration loads.
4.5 Overcoming natural obstacles with a gas pipeline
4.5.1 Overcoming natural obstacles by gas pipelines. Natural obstacles are water barriers, ravines, gorges, and gullies. Gas pipelines at underwater crossings should be laid deep into the bottom of the water barriers being crossed. If necessary, based on the results of floating calculations, it is necessary to ballast the pipeline. The elevation of the top of the gas pipeline (ballast, lining) must be at least 0.5 m, and at crossings through navigable and floating rivers - 1.0 m below the predicted bottom profile for a period of 25 years. When carrying out work using directional drilling - no less than 20 m below the predicted bottom profile.
4.5.2 At underwater crossings the following should be used:
– steel pipes with a wall thickness 2 mm greater than the calculated one, but not less than 5 mm;
– polyethylene pipes having a standard dimensional ratio of the outer diameter of the pipe to the wall thickness (SDR) of no more than 11 (according to GOST R 50838) with a safety factor of at least 2.5.
4.5.3 The height of the above-water passage of the gas pipeline from the calculated level of water rise or ice drift (high water horizon - GVV or ice drift - GVL) to the bottom of the pipe or span should be taken:
– at the intersection of ravines and gullies - not lower than 0.5 m and above the GVV 5% security;
– when crossing non-navigable and non-floating rivers - at least 0.2 m above the water supply and water supply line of 2% probability, and if there is a grub boat on the rivers - taking it into account, but not less than 1 m above the water supply line of 1% probability;
- when crossing navigable and raftable rivers - no less than the values established by the design standards for bridge crossings on navigable rivers.
4.5.4 Shut-off valves should be placed at a distance of at least 10m from the transition boundaries. The transition boundary is considered to be the place where the gas pipeline crosses the high water horizon with a 10% probability.
4.6 Crossing artificial obstacles by a gas pipeline
4.6.1 Gas pipelines crossing artificial obstacles. Artificial obstacles include roads, railways and trams, as well as various embankments.
4.6.2 The horizontal distance from the places where underground gas pipelines intersect tramways, railways and highways must be no less than:
– to bridges and tunnels on public railways, tram tracks, roads of categories 1 – 3, as well as to pedestrian bridges, tunnels through them – 30 m, and for non-public railways, roads of categories 4 – 5 and pipes – 15m;
– to the switch transportation zone (the beginning of the points, the tail of the crosses, the points where suction cables are connected to the rails and other track intersections) – 4 m for tram tracks and 20 m for railways;
– to the contact network supports – 3 m.
4.6.3 It is permitted to reduce the specified distances in agreement with the organizations in charge of the crossed structures.
4.6.4 Underground gas pipelines of all pressures at intersections with railway and tram tracks, highways of categories 1 - 4, as well as main city streets should be laid in cases. In other cases, the issue of the need to install cases is decided by the design organization.
4.7 Cases
4.7.1 Cases must meet the conditions of strength and durability. At one end of the case there should be a control tube extending under the protective device.
4.7.2 When laying inter-settlement gas pipelines in cramped conditions and gas pipelines on the territory of settlements, it is allowed to reduce this distance to 10 m, provided that an exhaust candle with a sampling device is installed at one end of the case, placed at a distance of at least 50 m from the edge of the roadbed (the axis of the outermost rail at zero marks). In other cases, the ends of the cases should be located at a distance:
– at least 2 m from the outermost rail of tram tracks and railways, 750 mm potassium, as well as from the edge of the roadway of streets;
– at least 3 m from the edge of the drainage structure of roads (ditch, ditch, reserve) and from the outermost rail of non-public railways, but not less than 2 m from the bottom of the embankments.
4.7.3 The depth of laying the gas pipeline from the base of the rail or the top of the road surface, and if there is an embankment, from its base to the top of the casing must meet safety requirements and be no less than:
– when performing open-cut work - 1.0 m;
– when carrying out work using the method of punching or directional drilling and panel laying – 1.5 m;
– when performing work using the puncture method – 2.5 m.
4.8. Intersection of pipes with roads
4.8.1 Pipe wall thickness steel gas pipeline when crossing public railways, it should be 2 - 3 mm more than the calculated one, but not less than 5 mm at distances of 50 m in each direction from the edge of the roadbed (the axis of the outer rail at zero marks).
4.8.2 For polyethylene gas pipelines in these sections and at the intersections of highways of categories 1 - 3, polyethylene pipes of no more than SDR 11 with a safety factor of at least 2.8 should be used.
4.9 Anti-corrosion protection of pipelines
4.9.1 Pipelines used in gas supply systems are usually made of carbon and low-alloy steels. The service life and reliability of pipelines is largely determined by the degree of protection against destruction upon contact with environment.
4.9.2 Corrosion is the destruction of metals caused by chemical or electrochemical processes during interaction with the environment. The environment in which metal is subject to corrosion is called corrosive or aggressive.
4.9.3 Most relevant for underground pipelines is electrochemical corrosion, which obeys the laws of electrochemical kinetics, is the oxidation of a metal in electrically conductive media, accompanied by the formation and occurrence of electric current. In this case, interaction with the environment is characterized by cathodic and anodic processes occurring in different areas of the metal surface.
4.9.4 All underground steel pipelines laid directly into the ground are protected in accordance with GOST 9.602–2005.
4.9.5 In soils of average corrosiveness in the absence of stray currents, steel pipelines are protected with insulating coatings of a “very reinforced type”; in soils of high corrosiveness and the dangerous influence of stray currents - by protective coatings of a “very reinforced type” with the mandatory use of 3X3.
4.9.6 All provided types of corrosion protection are put into operation when underground pipelines are put into operation. For underground steel pipelines in areas dangerously influenced by stray currents, 3X3 is put into effect no later than 1 month, and in other cases later than 6 months after laying the pipeline in the ground.
4.9.7 The corrosive aggressiveness of soil towards steel is characterized in three ways:
– specific electrical resistance m of soil determined in the field;
– electrical resistivity of the soil, determined in laboratory conditions,
– the average density of the cathode current (j k), necessary to shift the potential of steel in the soil by 100 mV more negative than the stationary one (corrosion potential).
4.9.8 If one of the indicators indicates high aggressiveness of the soil, then the soil is considered aggressive, and the determination of other indicators is not required.
4.9.9 The dangerous influence of stray direct current on underground steel pipelines is the presence of a displacement of the pipeline potential that varies in sign and magnitude relative to its stationary potential (alternating zone) or the presence of only a positive displacement of potential, usually varying in magnitude (anode zone) . For the pipelines being designed, the presence of stray currents in the ground is considered dangerous.
4.9.10 Hazardous effects alternating current on steel pipelines is characterized by a shift in the average potential of the pipeline in the negative direction by at least 10 mV relative to the stationary potential, or the presence of an alternating current with a density of more than 1 MA/cm 2 . (10 A/m 2.) on the auxiliary electrode.
4.9.11 The use of 3X3 is mandatory:
– when laying pipelines in soils with high corrosiveness (protection against soil corrosion),
– in the presence of the dangerous influence of direct stray and alternating currents.
4.9.12 When protecting against soil corrosion, cathodic polarization of underground steel pipelines is carried out in such a way that the average value of metal polarization potentials is within the range of –0.85V. up to 1.15V on a saturated copper sulfate electrode for comparison (m.s.e.).
4.9.13 Insulation work in route conditions is carried out manually when insulating prefabricated joints and small fittings, correcting damage to the coating (no more than 10% of the pipe area) that occurred during transportation of pipes, as well as when repairing pipelines.
4.9.14 When repairing damage to factory insulation on site and laying a gas pipeline, compliance with the technology and technical capabilities of coating application and quality control must be ensured. All repair work on the insulating coating is reflected in the gas pipeline passport.
4.9.15 Polyethylene, polyethylene tapes, bitumen and bitumen-polymer mastics, fused bitumen-polymer materials, rolled mastic-tape materials, compositions based on chlorosulfonated polyethylene, polyester resins and polyurethanes are recommended as the main materials for the formation of protective coatings.
DETERMINATION OF GAS CONSUMPTION
5.1 Gas consumption
5.1.1 Gas consumption by network sections can be divided into:
travel, transit and dispersed.
5.1.2 Travel flow rate is a flow rate that is evenly distributed along the length of a section or the entire gas pipeline and is equal or very close in value. It can be selected through identical in size and for ease of calculation it is evenly distributed. Typically, this flow rate is consumed by gas appliances of the same type, for example, capacitive or instantaneous water heaters, gas stoves and so on. Concentrated flows are those that pass through the pipeline, without changing, along the entire length and are collected at certain points. The consumers of these expenses are: industrial enterprises, boiler houses with constant consumption over a long period of time. Transit costs are those that pass through a certain section of the network without changing and provide gas flow, being a route or concentrated flow to the next section.
5.1.2 Gas consumption in a populated area is travel or transit. There are no concentrated gas costs, since there are no industrial enterprises. Travel expenses consist of the costs of gas appliances installed at consumers, and depend on the season of the year. The apartment is equipped with four burner stoves of the Glem UN6613RX brand with a gas flow rate of 1.2 m 3 / h, a Vaillant type instantaneous water heater for hot flow with a flow rate of 2 m 3 / h, and capacitive water heaters Viessmann Vitocell-V 100 CVA- 300" with a flow rate of 2.2 m 3 / h.
5.2 Gas consumption
5.2.1 Gas consumption varies by hour, day, day of the week, month of the year. Depending on the period during which gas consumption is assumed to be constant, they are distinguished: seasonal unevenness or unevenness by month of the year, daily unevenness or unevenness by day of the week, hourly unevenness or unevenness by hour of the day.
5.2.2 The unevenness of gas consumption is associated with seasonal climatic changes, the operating mode of enterprises during the season, week and day, the characteristics of the gas equipment of various consumers, and to study the unevenness, stepwise gas consumption is built over time. To regulate seasonal unevenness in gas consumption, the following methods are used:
– underground gas storage;
– the use of consumers of regulators that discharge excess in the summer;
– reserve fields and gas pipelines.
5.2.3 To regulate the unevenness of gas consumption during the winter months, gas is withdrawn from underground storage facilities and, during short periods of the year, pumped into underground storage facilities. To cover daily peak loads, using underground storage facilities is not economical. In this case, restrictions are imposed on the gas supply to industrial enterprises and peak coverage stations are used, in which gas liquefaction occurs.
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Chemical composition natural gases is heterogeneous and depends on the conditions of their formation and location in the sedimentary layer.
The chemical composition of natural gases is so simple that obtaining their substitutes, which have not only the corresponding characteristics, but also an almost identical composition, does not require special technical solutions and excessive capital costs. The exception to this rule is hydrogen, a gas that could in the future replace dwindling natural gas reserves. Since the purpose of gasification of fossil fuels is to produce methane, in the absence of hydrocarbon fuels, hydrogen, from which all natural gases mainly consist, could become an acceptable substitute for natural gas, which has a number of additional valuable characteristics.
The chemical composition of natural gases is measured by an automatic gas chromatograph. The accuracy of these measurements is such that it makes it possible to calculate the main physical characteristics with a small error, which, thus, can be determined not directly, but by recalculation.
The chemical composition of natural gas received by cement factories from main gas pipelines can change not only for the above reasons, but also due to the fact that main gas pipelines coming from different fields are interconnected.
The chemical composition of natural gas is the same as indicated on page.
The chemical composition of natural gases is not the same, but their main component is methane. Saratov gas contains 94 3%, Kuibyshevsky - 74 6%, Dashavsky - 98%; in gases from different regions of Dagestan, Kerch, Baku, Melitopol, Ukhta - from 80 to 98% methane. The content of higher hydrocarbons is insignificant: from fractions of a percent to several percent. The composition of gases in some areas may be different in different layers, as, for example, in the gases of the Maikop and Dagestan fields.
The effect of the chemical composition of natural gas on its combustion temperature was described in Chapter I. An increase in the temperature of the air entering the rotary kiln significantly increases the flame temperature, but to a lesser extent than the amount of air heating.
If differences in the chemical composition of natural gases accumulated in different traps in a basin are determined mainly by the ability of each trap to retain more or less mobile gas components, then determining the carbon isotope composition of methane from these gases can be a valuable means of better assessing the conditions of gas trapping in various reservoirs .
The fractional composition of limestone from the Elenovskoe deposit and the chemical composition of natural gas are given on page.
Gas chromatography is one of the main methods for studying the chemical composition of natural gases, oils and condensates. The use of this effective and highly sensitive method allows not only to evaluate gas, oil, condensate as chemical raw materials, but also to obtain new geochemical indicators characterizing oil-producing rocks and oil formation zones.
Gases, 1 m3 of which contains more than 100 g of heavy hydrocarbon gases (ethane, propane, etc.), are called rich, and less than 100 g are called dry. The chemical composition of natural gases depends on the type of deposit.
Natural gases, depending on the deposits, can be dry or gas condensate. The chemical composition of natural gas from different fields is not the same.
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COMPOSITION AND PHYSICAL AND CHEMICAL PROPERTIES OF NATURAL GASES
Natural gases are substances that are gaseous under normal (n.s.) and standard (s.s.) conditions. Depending on the conditions, gases can be in free, adsorbed or dissolved states.
In reservoir conditions, gases, depending on their composition, pressure and temperature (thermobaric regime in the reservoir), can be in different states of aggregation - gaseous, liquid, in the form of gas-liquid mixtures.
Free gas usually located in the elevated part of the formation and is located in the gas cap. If there is no gas cap in an oil reservoir, then all of the gas in the reservoir is dissolved in the oil.
The pressure at which the gas present in the reservoir begins to be released from the oil is called saturation pressure. The saturation pressure of oil with gas in reservoir conditions is determined by the composition, amount of oil and gas, and reservoir temperature.
Dissolved gas, as production pressure decreases, is released from the oil. He's called associated gas. Under reservoir conditions, all oils contain dissolved gas. The higher the reservoir pressure, the more gas can be dissolved in the oil. In 1 m 3 of oil, the content of dissolved gas can reach 1000 m 3.
Natural gases extracted from gas, gas condensate and oil fields consist of hydrocarbons (HC) of the methane series CH 4 – C 4 H 10: methane, ethane, propane, isobutane and n-butane, as well as non-hydrocarbon components: H 2 S, N 2, CO, CO 2, H 2, Ar, He, Kr, Xe and others.
Under normal and standard conditions, only hydrocarbons of composition C 1 – C 4 exist thermodynamically in the gaseous state. Hydrocarbons of the alkane series, starting from pentane and above, under these conditions are in a liquid state, the boiling point for iso-C 5 is 28 o C, and for n-C 5 → 36 o C. However, hydrocarbons C are sometimes observed in associated gases 5 due to thermobaric conditions, phase transitions and other phenomena.
The qualitative composition of gases of petroleum origin is always the same (which cannot be said about gases from volcanic eruptions). The quantitative distribution of components is almost always different.
The composition of gas mixtures is expressed as mass or volumetric concentration of components in percentages and mole fraction X.
where Wi is the mass of the i-th component; ΣWi is the total mass of the mixture.
, (2.16)
where Vi is the volume of the i-th component in the mixture; Σ Vi is the total volume of gas.
where ni is the number of moles of the i-th component in the mixture; Σpi is the total number of moles of gas in the system.
The relationship between the volumetric and molar concentrations of components follows from Avogadro's law. Since equal volumes of any gases at the same temperature and pressure contain the same number of molecules, the volume of the i-th component of the mixture will be proportional to the number of moles of the i-th component:
where K is the proportionality coefficient. Hence
, (2.19)
i.e., the concentration of a component in percent by moles (% mol.) in a mixture of gases at atmospheric pressure practically coincides with the volumetric concentration of this component in percent (% vol.).
At high pressures liquid hydrocarbons dissolve in the gas phase (gas solutions, gas condensates). Therefore, at high pressures, the gas density can approach the density of light hydrocarbon liquids.
Depending on the predominance of light (methane, ethane) or heavy (propane and higher) hydrocarbons in oil gases, gases are divided into dry and oily.
Dry called gas natural gas, which does not contain heavy hydrocarbons or contains them in small quantities.
Bold gas is a gas containing heavy hydrocarbons in such quantities that it is advisable to produce liquefied gases or gas gasoline from it.
Gases produced from pure gas deposits contain more than 95% methane (Table 2.2) and represent the so-called dry gases.
