From internal pipelines, drains are transported by external ...
Any gas fuel is a mixture of various simple combustible and ballast gases. The chemical properties of gas determine the properties of the mixture, i.e., gas fuel.
Alkanes, i.e., hydrocarbons of the limiting series, are the main components of the combustible part of natural and associated gases. Alkanes are often called paraffins or methane hydrocarbons. The general chemical formula of alkanes is CnH 2n + 2. The parent of a number of alkanes is methane - CH 4, then, as the number of carbon atoms in the molecule increases, ethane - C 2 H 6, propane - C 3 H 8, butane - C 4 H 10, pentane - C 5 H 12, hexane - C 6 H 14, etc.
The physical and chemical properties of the gas of saturated hydrocarbons naturally change as their molecular weight increases.
Under normal conditions, i.e., at a temperature of 0 ° C and a pressure of 760 mm Hg. Art., the first members of the series up to butane inclusive - gases that do not have color and odor, the next - liquids. All alkanes, except methane, have a density higher than air density.
Under the influence of high temperature, alkanes break down, pass into simpler and more stable compounds (for example, methane, as well as alkenes), releasing soot carbon and hydrogen. The resistance of alkanes to temperature decreases with increasing molecular weight.
Alkanes, as well as products of their complete combustion, are not poisonous. There is evidence that high molecular weight saturated hydrocarbons at high concentrations in the air have a weak narcotic effect.
Alkenes, or olefins, are present in appreciable amounts in the composition of artificial gases, especially liquid fuel cracking gases. The parent of a number of alkenes is ethylene. The general chemical formula of alkenes is C n H2 n - The first three members of this series are ethylene (ethene) C 2 H 4, propylene (propene) C 3 H 6 and butylene (butene) C 4 H 8.
Alkenes, which are unsaturated hydrocarbons, are valuable raw materials for the chemical industry.
The toxic effect of alkenes is similar to the action of alkanes, i.e., at high concentrations they have narcotic properties.
Hydrogen H 2 is available in all artificial gases. It is a flammable, odorless and colorless gas, non-toxic. Hydrogen is the lightest of gases, it is 14.5 times lighter than air, so the lower volumetric heat of its combustion is less than that of other components of gas fuel.
Hydrogen sulfide H 2 S is found in most artificial and some natural gases. It is a colorless combustible gas heavier than air (density - 1.54 kg / m 3), with a strong odor reminiscent of the smell of rotten eggs. Causes severe corrosion of metals.
Hydrogen sulfide is poisonous. It acts on the nervous system, as well as on the respiratory tract and eyes. At concentrations of hydrogen sulfide above 1 mg / l, fatal poisoning can occur almost instantly from paralysis of the respiratory centers. Its permissible concentration in the indoor air is set to not more than 0.01 mg / l, and in the gas supplied to the city networks, not more than 2 g per 100 m 3. High toxicity of hydrogen sulfide and stringent requirements for its content necessitate the purification of gas fuel before supplying it to consumers.
Carbon monoxide CO is contained in large quantities in generator gases, being, along with hydrogen, the main combustible component.
Carbon monoxide is a colorless, chemically resistant flammable gas. The density of CO (1.25 kg / m 3) is slightly lower than the density of air.
Carbon monoxide is a powerful poison; its concentration in air of 1% leads in 1-2 minutes to severe poisoning and death. The maximum concentration of CO in the air of the working area of \u200b\u200bthe workshops, according to existing standards, is not more than 0.03 mg / l for prolonged operation and not more than 0.05 mg / l for up to 1 hour in a gassed atmosphere.
Carbon monoxide is a product of incomplete combustion of carbon and can be found in the products of combustion of any fuel containing carbon or carbon compounds.
Carbon disulfide CS 2 in small quantities is part of the gases obtained by dry distillation of fuels containing sulfur. The boiling point of carbon disulfide is + 46 ° С, i.e., under ordinary conditions, it is a liquid. Carbon disulfide vapors are 2.6 times heavier than air. High concentrations of carbon disulfide vapors in the air lead to poisoning. The maximum permissible concentration in the working area is 0.01 mg / l.
Hydrogen cyanide HCN is the strongest poison contained in small quantities in dry distillation gases. The maximum HCN content in gases used for urban gas supply, Pe is above 0.05 mg / l, the maximum permissible concentration in the air of industrial enterprises is 0.0003 mg / l.
In addition to the above combustible gases and vapors, artificial gases contain a certain amount of resins, ammonia, naphthalene. These compounds, which are of great value for the chemical industry, are extracted from gas fuels in gas recovery or purification plants.
As ballast impurities in all gases, both natural and artificial, there are nitrogen N 2, water vapor H 2 O and carbon dioxide CO 2. Nitrogen and carbon dioxide are not toxic and not aggressive, i.e., they do not have corrosive properties. The presence of water vapor can lead to the formation of condensate, increased corrosion of pipelines and the formation of hydrate plugs during long-distance transport of natural gas. To avoid this, natural and associated gases are dried before being fed into the main pipelines, in which carbon dioxide is also removed.
Non-oil gas fuels
Petroleum gas fuels
Gas fuel classification
CONSPECT PLAN
LESSON LESSON № 10
Discipline - Refueling vehicles with fuel and lubricants
MDK 03.02. Organization of transportation, reception, storage and dispensing of petroleum products
Theme of the lesson. “Features of liquefied gases and their characteristics”
ñ liquefied petroleum gases
ñ compressed matching pairs
ñ compressed natural gas
ñ gas condensate fuel
ñ alcohols
ñ hydrogen
Gas fuelsare divided into
ñ low-calorie,
ñ medium calories
ñ high-calorie.
Low-calorie gas fuels include blast-furnace gas (10 000 kJ of heat are obtained from 1 m3).
Medium-calorie gas fuels include coke and smelting gases (out of 1 m3 of gas - 10,000 - 20,000 kJ of heat).
High-calorie gas fuels include natural gas (35,000 kJ), associated oil (45,000 kJ), liquefied (46,000 kJ), cracked (50,000 kJ).
Natural gashave no color, smell and taste.
Calorific value- this is the amount of heat that is released during the complete combustion of 1 m3gas. It is measured in kcal / m3.
Combustion temperature called maximum temperature, which can be achieved with complete combustion of the gas, if the amount of air required for combustion exactly corresponds to the chemical formulas of combustion, and the initial temperature of the gas and air is Combustion temperature of individual gases makes 2000 - 2100ºС.
Flash point this is the minimum initial temperature at which combustion begins. For natural gas, it is 645ºС.
Explosion limits The gas-air mixture in which the gas is:
up to 5% - not lit;
from 5 to 15% - explodes;
more than 15% - burns when air is supplied.
Flame propagation speed for natural gas - 0.67 m / s (methane CH4)
Combustible gases are odorless. To timely detect their presence in the air, quickly and accurately determine the places of leakage, odorize the gas (give an odor). Ethyl mercoptan (C2H5SH) is used for odorization. The odorization rate is 16 g of odorant per 1000 m3 of gas. Odorization is carried out at gas distribution stations (GDS). If there is 1% natural gas in the air, its smell should be felt.
Combustible gasesused as motor fuel for cars can be divided into three main types according to the conditions of the specifics of the content, affecting the possibility of use on different classes of cars (cars, trucks, buses):
1. Liquefied petroleum gases (CIS);
2. Compressed (compressed) natural gases (CNG);
3. Liquefied natural gases (LNG);
4. Hydrogen fuel.
The main components of liquefied gases (modern fuel for engines) are propane C3H8, butane C4H10 and mixtures thereof.
Get these hydrocarbons from gases, associated oil, when drilling wells and from gaseous fractions formed during various types of processing of petroleum products and coal.
Critical temperatures propane (97 ° С) and butane (126 ° С) are significantly higher than usual ambient temperatures; therefore, these hydrocarbons turn into a liquid state at a slight pressure (without cooling). At 20 ° C, propane is liquefied under a pressure of 0.716 MPa, and butane under a pressure of 0.103 MPa, i.e. LPG plants are medium pressure units.
Store liquefied gases in cylinders with a capacity of 250 l (162 ... 225 l of gas provide a range of up to 500 km), designed for a working pressure of 1.6 MPa. Under such conditions, even pure propane is in liquid form, which makes it possible to operate cars on liquefied petroleum gases (LPG) year-round (except for the southern regions in the summer, where the temperature is above 48.5 ° C).
Octane number propane 105, and normal butane and isobutane 94.
Octane Number (OCH) characterizes the antiknock properties of the gas and serves as a criterion for establishing the permissible degree of compression of the engine. OCH gas fuels is in the range of 70? 110. The higher the GF of the gas, the less prone to detonation combustion and the higher the permissible compression ratio of the engine and, consequently, its efficiency.
Liquefied gas density makes 510 ... 580 kg / m3, i.e. they are almost twice as light as water. Density (P, kg / m3) represents the mass enclosed in a unit volume of gas in a liquid or gaseous phase under certain external conditions (temperature and pressure).
Gas viscosity very small, which facilitates their transportation through pipelines. The volume expansion coefficient of the CIS is very large, i.e., with an increase in the outside temperature, they expand significantly, therefore, when filling the tanks, it is necessary to leave free space (approximately 15% of the capacity). In normal condition, the CIS is not toxic and odorless.
The CIS is half the price of gasoline and at the same time provide up to 10 ... 20% energy savings, i.e. for a car that spends 15 liters of high-octane gasoline per 100 kilometers, 13 liters of LPG is enough, and for a car with 11 liters of gasoline per 100 kilometers, 9.8 liters of CIS is enough.
GOST 27578 - 87 “Liquefied hydrocarbon gases for automobile transport” establishes the following CIS brands: PA - automobile propane for use in winter at temperatures from -20 ° to -30 ° C; PBA - automotive propane-butane for use at a temperature not lower than -20 ° C.
The named indicators are interconnected by the ratio:
Cetane number (CT) characterizes the flammability of the gas: the lower it is, the worse the ignition of the gas occurs and, therefore, the starting properties of the engine on this gas deteriorate.
Octane and cetane numbers are related by a linear relationship: the higher the OR, the lower the DH.
Flammability limits of gas characterize the boundary values \u200b\u200bof the gas content (in percent by volume) in the air, at which ignition of the combustible mixture is still possible. The flammability of a gas mixture is influenced by temperature, pressure and its turbulence (turbulence of gas flows). Overestimated and re-enriched gas mixtures do not ignite.
The knowledge of these limits is important both for the organization of the working process and regulation of fuel supply in engines, and for determining the explosion and fire safety of concentrations and the corresponding arrangement of premises for storage and maintenance cars.
Critical Temperature (Tcr) - the temperature at which the density of the liquid and its saturated vapor become equal and the interface between them disappears.
Saturated vapor pressure (Rkr) at critical temperature is called critical pressure.
The first indicator is the chemical formula.Methane and liquefied petroleum gas, which includes ethane, propane, butane and pentane, have neither lead in their composition nor in impurities, which makes the exhaust more environmentally friendly when burned than gasoline.
The molecular weight of gases is lower than that of gasoline, therefore, filling the cylinders with a combustible mixture, ceteris paribus, will be lower than gasoline. This is a minus, as it leads to a decrease in the power of the internal combustion engine.
The relative density of the gas phase in the air - the value necessary to calculate the mechanisms of mixture formation of the working fluid (gas-air mixture) and does not directly characterize the advantages or disadvantages of gas fuel over gasoline, but indicates that methane will rise upward when the gas leaks, and the LPG will accumulate below.
Fluid density - characterizes the volume of the vessel for storing the liquid phase of the fuel. We see that for the same mass, gasoline needs less volume than gas. This is a minus.
Critical temperature.Hydrocarbon gases having a critical temperature well above normal ambient temperatures (for example, propane 96.8 ° C and butane 152.0 ° C) are easily liquefied and stored in a liquefied state at a relatively low pressureand. They are stored in fairly light containers, allowing them to be used to power the engines of cars and light trucks.
And methane, at which the critical temperature is much lower (minus 82.1 ° C), will be at any pressure in the gaseous state, and for its use as gas fuel it is contained in cylinders under a pressure of 20 MPa.
Lower calorific value for all gases more than gasoline. This is an advantage of gas fuel and compensates for the reduced filling of the cylinders due to the low relative density of the gas.
The stoichiometric coefficient for gases is higher than for gasoline.
Octane numbergas is significantly higher than gasoline. This is a great advantage of gas, which allows you to save the engine from detonation, increase its power by increasing the compression ratio and reduce fuel consumption.
Flash point. Not in favor of gas. This will degrade the starting performance of the engine.
Flammability limits and excess air coefficient in favor of gas fuel. They say that the limits of regulation of internal combustion engines on gas fuel are wider than on gasoline.
Based on the considered physicochemical properties of gas fuels, it can be argued that they certainly surpass gasoline in the following parameters:
– allow achieving higher power and fuel-economic indicators than similar in the way of organizing the workflow gasoline engines. Specially designed gas engines surpass gasoline engines in specific power indicators, and are close to diesel engines in fuel efficiency;
– in terms of environmental performance, emissions significantly exceed gasolines.
PHYSICAL AND CHEMICAL PROPERTIES OF NATURAL GASES. Natural gases are colorless, odorless, and tasteless.
The main indicators of combustible gases that are used in boiler rooms: composition, calorific value, specific gravity, combustion and ignition temperature, explosive limits and flame propagation velocity.
Natural gases from purely gas fields consist mainly of methane (82 ... 98%) and other hydrocarbons. The heat of combustion is the amount of heat that is released during the complete combustion of 1 m3 of gas. It is measured in kcal / m3. They distinguish between the higher calorific value Qv when the heat expended on the condensation of water vapor in the flue gases and the lower Qn when this heat is not taken into account are taken into account - it is used in the calculations. In practice, gases with different calorific values \u200b\u200bare used.
For the equalization characteristic of fuel quality, the so-called conventional fuel is used, for the unit of which 1 kg of fuel is taken, having a heat of combustion Qн \u003d 7000 kcal / m3 (29300 kJ / kg). The combustion temperature is the maximum temperature that can be achieved with complete combustion of the gas, if the amount of air required for combustion exactly matches the chemical formulas of combustion, and the initial temperature of the gas and air is 0. The combustion temperature of individual gases is 2000 - 2100ºС. The actual combustion temperature in the boiler furnaces is lower than the heat productivity (1100 - 1400ºС) and depends on the combustion conditions.
Ignition temperature is the minimum initial temperature at which combustion begins. For natural gas, it is 645ºС. Explosion limits The gas-air mixture in which the gas is located: up to 5% - does not burn; from 5 to 15% - explodes; more than 15% - burns when air is supplied. The flame propagation velocity for natural gas is 0.67 m / s (methane CH4). Flammable gases are odorless.
To timely detect their presence in the air, quickly and accurately determine the places of leakage, odorize the gas (give an odor). Ethyl mercoptan (C2H5SH) is used for odorization. The odorization rate is 16 g of odorant per 1000 m3 of gas. Odorization is carried out at gas distribution stations (GDS). If there is 1% natural gas in the air, its smell should be felt.
The presence of more than 20% of gas in the room causes suffocation, its accumulation in an enclosed volume of 5 to 15% can lead to an explosion of the gas-air mixture, with incomplete combustion, carbon monoxide CO is released, which even at a low concentration (0.15%) is poisonous. 2.3
End of work -
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Natural gas composition
Physical properties
Pressure and temperature
For an objective assessment of bottomhole pressures and the possibility of comparing them, the concept of reduced pressure is introduced. The measured or calculated bottomhole pressures are reduced (recounted) to a conventional horizontal plane, which can be taken any plane within the reservoir, the absolute mark of which is known.
Usually, the plane passing through the initial oil-water contact, the absolute mark of which is determined during the exploration of the field, is taken as the reduction plane. If the borehole faces communicate through a permeable formation, then the same reduced static pressures are set in them.
The reduced temperature is the ratio of the thermodynamic temperature of a substance to its critical temperature
1) critical - the limiting temperature of the equilibrium coexistence of two phases (liquid and its vapor), above which these phases are indistinguishable
Physical properties of fluids in reservoir conditions
Water compressibility is a reversible change in the volume of water in reservoir conditions under pressure. The value of the compressibility coefficient ranges from (3-5) -104. The compressibility of water decreases with increasing salt concentration and increases with increasing dissolved gas content.
The volumetric coefficient of produced water Lb depends on mineralization, chemical composition, gas content, reservoir pressure and temperature. For the formation water of oil and gas fields Lb \u003d 0.8-1.2.
The density of water in reservoir conditions depends mainly on its salinity, pressure and temperature. In most cases, due to temperature, the density of water in reservoir conditions is 20% lower than in surface conditions.
The viscosity of formation water depends primarily on temperature, salinity and chemical composition. In most cases, the viscosity of the formation water of oil and gas fields is 0.2-1.5 MPa-s.
Concepts: oil field, reservoir, reservoir, development object
Oil and oil and gas fields are accumulations of hydrocarbons in the earth's crust confined to one or more localized geological structures, i.e. structures located near the same geographical point.
A reservoir is a natural local single accumulation of oil in one or more interconnected reservoirs, i.e. in rocks capable of containing and giving out oil during development.
An object of development is a geological formation artificially isolated within a developed field (reservoir, massif, structure, aggregate of reservoirs) containing industrial hydrocarbon reserves, the extraction of which from the bowels is carried out using a certain group of wells or other mining structures.
One, several or all layers of the field may be included in the development object.
The main features of the development object are the presence of industrial oil reserves in it and the specific group of wells inherent in this object with which it is developed.
Rational oil field development system
Rational is called a development system that provides the most complete extraction of fluids from formations at the lowest cost. It provides for compliance with the rules for the protection of the subsoil and the environment, takes into account the natural, industrial and economic features of the area.
Features of a multi-layer field development system
There are three systems for developing a multilayer oil field:
The bottom-up development system, in which oil reservoirs (deposits) are introduced into development sequentially: each overlying one after development of the underlying reservoir, and the reservoir from which development begins is called the base or reference horizon (reservoir). The base horizon is selected on the basis of its high productivity and oil grade, and the reservoir should be well studied over a large area and lay in conditions favorable for its quick drilling
The top-down development system, in which formations are introduced into development: each underlying one after overlying development. This system was widely used during the period when the shock method of drilling prevailed. Currently, the top-down development system is allowed as an exception when developing shallow-lying oil formations drilled by light mobile machines, provided that the upper formations are poorly permeable and, when subsequent wells pass them to the underlying formations, the absorption of the mud and the pack of the upper ones strata is developed according to the "bottom up" system.
The system for the simultaneous development of two or more layers (deposits) provides that each of the layers is drilled simultaneously with a separate grid of wells. This system is used under the condition that oil reservoirs are highly productive with a well-defined pressure mode, are drilled quickly and are operated while maintaining reservoir pressure.
Development System for Production Facilities
The field development system provides for the solution and implementation of the following measures:
1. The selection of production facilities (in a multifaceted field) and determining the order of their input into development. A production facility is a reservoir or group of reservoirs developed by an independent grid of wells while ensuring control and regulation of the process of their operation.
2. Determination of the number of wells, their placement at the production facility and the order of putting wells into operation.
3. The establishment of the operating mode of production (sometimes injection) wells (determination of their debtor or flow rate, bottom-hole pressure and changes in these indicators over time).
4. Regulation of the balance of reservoir energy in oil or gas deposits "by affecting the reservoirs as a whole.
Field development systems can be classified by the nature or order of implementation of these activities as follows.
Wellbore Theory
An enlarged well theory is most relevant for gas and gas condensate fields, since gas fields are developed in the mode of depletion of reservoir energy, and most gas condensate fields are also developed without maintaining reservoir pressure and sooner or later they switch to the mode of depletion of reservoir energy. In the case of oil fields, reservoir pressure is typically maintained. Therefore, the flow of circulating water is of subordinate importance. The development of oil fields under natural water pressure conditions usually takes place in the case of small initial oil reserves and good reservoir properties of the reservoir.
Basic concepts of the phase state of multicomponent systems
contain more than three components, which can be simple substances and (or) chemical compounds. Multicomponent systems in nature - ores, sea water, minerals, brines of salt lakes, oil, hydrocarbon gases, etc .; in technology - metal alloys, salt mixtures, aqueous solutions of salts, mixtures of organic compounds, etc.
In oilfield practice, there are various types of phase transitions of a substance — evaporation, condensation, melting, etc. The most common field engineer has to deal with phase transformations of solutions. In a system under conditions of any phase transition, two or several different phases can coexist in thermodynamic equilibrium simultaneously. The conditions for phase equilibrium are the equality of temperatures and pressures in all parts of the system. In addition, at constant temperature and pressure, the chemical potentials of the contacting phases must be equal. In multicomponent systems, phase equilibrium conditions occur when the chemical potentials of a given component in all phases of a system in equilibrium become equal to each other.
All phase transitions are divided into two types - the first and second kind.
The simplest examples of phase transitions of the first kind are evaporation, melting. During phase transformations of this kind, the volume of the system changes and the amount of heat, which is called the latent heat of transition, is absorbed (or released). The existence of a transition heat indicates a change in the entropy of the system. In the process of evaporation, the substance absorbs heat. Its entropy in the gaseous state at given pressure and temperature is greater than in the liquid state. Consequently, during a first-order phase transition, the volume Ii entropy of the substance changes. The first-order phase transition characteristic (equivalent to that described above) can be given using the Gibbs function
Question 33
Physical properties of natural gases
A significant difference between the physical properties of gas and the physical properties of oil, expressed mainly in its low density, high elasticity, and significantly lower viscosity, determines the specifics of the development of gas and gas condensate fields, which consists in the fact that gas is produced mainly by the fountain method. At the same time, the complex and extended system of gas supply from the reservoir to consumption is completely tight and represents a single whole.
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 fuel, its components are isolated from it for individual use.
Natural gas composition
Up to 98% of natural gas is methane; it also includes homologues of methane - ethane, propane and butane. Sometimes carbon dioxide, hydrogen sulfide and helium may be present. This is the composition of natural gas.
Physical properties
Natural gas is colorless and odorless (if it does not contain hydrogen sulfide), it is lighter than air. Combustible and explosive.
Estimated physical characteristics (depending on composition; under normal conditions, unless otherwise indicated):
Density: from 0.68 to 0.85 kg / m³ relative to air (dry gaseous); 400 kg / m³ (liquid). Auto-ignition temperature: 650 ° C; Explosive concentrations of a mixture of gas with air from 5% to 15% volume; Specific calorific value: 28-46 MJ / m³ (6.7-11.0 Mcal / m³); Octane number when used in internal combustion engines: 120-130. 1.8 times lighter than air, therefore, when leaking, it does not collect in the lowlands, but rises up
