Natural gas represents a gases mixture that can be found in the ground and is created by the way of organic substances decomposition of anaerobic character. Typically, this type of gas is a mix of gaseous hydrocarbons, such as butane, ethane, methane, propane, etc., which is found in the earth's crust. It is broadly utilized as a fuel of very economical kind for various power plants in the glass and cement industry, nonferrous and ferrous metallurgy, building materials production and for household needs. It is also used as raw component for various organic compounds.
This type of gas is a mineral deposit that is often a by-product gas at oil production. When in reservoir conditions (conditions of occurrence in the bowels of the earth), it is in the gaseous state as separate clusters or in oil-gas fields as gas cap – it is dissolved in oil or water (in situ) or a free gas, and in standard conditions (0.101325 MPa and 20° C) – only in the gaseous state.
Natural gas has neither color nor odor. In order to have a possibility to identify a leak by means of smell, there is odorant added to it before serving to consumers – substance having a pungent specific odor. Ethyl mercaptan can be used as odorant – C2H5SH or a mix of natural mercaptans – C2H3P. In gas pipelines gas without odorant is transported, as the latter belongs to corrosive materials, causing corrosion of pipe walls.
Physico-chemical properties, parameters that characterize gas (condensate) under reservoir pressure and temperature: density, viscosity, moisture content, solubility, reverse condensation, critical temperature and pressure, volumetric coefficient, compressibility factor and others.
Natural Gas Production
It is found in the ground at the depth ranging from 1000 meters to several kilometers. At such a depth, gas is contained in the microscopic voids (pores). The pores have connections among them in the form of cracks – microscopic channels (Paltsev et al., 2011). By the cracks, gas goes from the pores of high pressure to the pores of lower pressure till it is in the wellbore. Motion of gas in the reservoir is subject to certain laws. Gas exits from the interior due to the fact that the reservoir is pressurized above atmospheric repeatedly. Thus, the driving force is the difference between the pressures in the reservoir and the collection system.
Wells are used to extract gas from the earth. Well is excavation of circular cross-section from the ground surface or underground excavation without human access at any angle to the horizon, with a diameter no more than two meters. Wells are usually placed uniformly throughout the field. It is performed for uniform drop in formation pressure reservoir. Otherwise, there may be flowing gas field between areas, and premature flooding of deposits.
Gas from the wells should be prepared for transportation to the end user – chemical plant, boiler, thermal power plants, city gas networks. The need for preparing gas exists due to the presence in it, except for the target components (target for different users are different components), of impurities that cause difficulties during transportation or use. Thus, water vapor contained in the gas, under certain conditions, can form hydrates or condense, accumulate at various locations (e.g., bending of the pipeline), hindering movement of gas; hydrogen sulfide is highly corrosive for gas equipment (pipes, heat exchangers, tanks, etc.). In addition to preparation of the gas itself, pipeline also needs to be prepared. Wide application herein have nitrogen units that are used to create an inert environment in the pipeline.
Gas is prepared under various schemes. According to one of them, in the immediate vicinity of the deposit there is constructed comprehensive gas treatment unit (GTU), which performs gas cleaning and drying. If gas contains a large amount of helium or hydrogen sulfide, the gas is processed at the gas processing plant where helium and sulfur are recovered (Colborn et al., 2011).
Possible Uses of Natural Gas
- Natural gas is used as fuel in multi-residential and private homes for cooking, heating and hot water. It can also be used as fuel for cars and boiler.
- Methane is used as a feedstock in the chemical industry for a variety of organic substances, for example, plastics.
- Natural gas is used for refillable gas lamps that are used to illuminate. Methane itself is used as a raw material for the production of acetylene, ammonia, methanol and hydrogen cyanide.
- At the same time, natural gas is the main source of raw materials in the production of ammonia. Almost three-quarters of ammonia is used for the production of nitrogen fertilizers (Mokhatab & Poe, 2012).
- Hydrogen cyanide obtained from ammonia along with acetylene serve as the original raw materials used for production of various synthetic fibers. Acetylene can produce different strata-kata, which are widely used in industry and at home. Also, acetate silk is produced from it.
- Chemical methane is used not only to produce a variety of plastics, but also for the production of rubber, organic acids and alcohols. It is with the use of natural gas that it has become possible to produce many of the chemicals, which do not exist in nature, e.g., polyethylene.
- Natural gas is one of the best fuels that are used for industrial and domestic needs. Its value as a fuel is also that it is one of quite pure mineral fuels environmentally. When burned, there are emitted much less harmful substances when compared to other fuels. That is why natural gas is one of the main sources of energy in all human activities.
Environmental effects
Direct impacts on soil associated with the preparatory earthworks and are expressed as follows:
- violation of the existing forms of natural relief as a result of various types of excavation (trenching and other recesses, dumping mounds, planning, etc.);
- deterioration of physical, mechanical, chemical and biological properties of soil;
- destruction and damage of crops and grasslands;
- cluttering soil with wastes of building materials, forest residues, etc.
- microrelief disturbances caused by multiple passage of heavy construction equipment.
The negative impacts on land resources during the operation of gas facilities include (Burnham et al., 2011):
- direct loss of land fund seized by placing permanent surface structures;
- inconvenience in land use due to the division of farmland slopes utilities and roads;
- reduction in agricultural production associated with long-term withdrawal of arable land and fertile soil, properties deterioration in the temporarily allocated lands.
Sources of air pollution during construction are:
- the exhaust gases of construction machinery, vehicles, and mobile power boiler on liquid and gaseous fuels;
- smoke from the engine, burning wood waste and construction materials;
- hydrocarbons from a fuel depot, petrol stations, fuel tanks;
- welding fumes from the pipe welding and manual welding installations.
Sources of contamination of water bodies during construction are domestic, industrial and stormwater from residential settlement sites for temporary objects from the sites of technological objects.
In use gas is one of the most ecologically-friendly fuels, as when burning its emissions are not so dangerous for people and ecology as other types of fuels.
Pros and Cons of Use
Positive sides of combustible gases are known to almost all users. Gas is very practical in handling it in everyday life: quickly and easily ignited, burns without residue, does not produce ash and soot, does not require the construction of special warehouses around houses and cottages, as it is necessary for other types of fuel. At any time, you only need to bring a lighted match, open the valve of the gas appliance and you can immediately get a heat source, on which it is easy to cook food or heat or boil water for domestic purposes or bath. The gas does not need to preform, and during the combustion emits large amounts of heat.
But along with the positive aspects of combustible gases, there are also inherent negative features, such as follows: in case of illiterate use or security breach, it can cause irreparable human tragedies, as well as poisoning and suffocation, explosions and fires. It is worth noting that in themselves natural and liquefied petroleum gases used for domestic purposes, are not poisonous and do not have toxic effects on humans and animals, and dangerous only because they displace the air leakage from the premises (ISSU, 2013). With significant concentrations of these gases in the room a person in it begins to feel the lack of oxygen. A buildup of natural or liquefied gases in room air for more than 10% can cause death by suffocation. Thus, we can conclude that both natural and liquefied gases, not being toxic, have asphyxiating endowed properties.
References
Burnham, A., Han, J., Clark, C. E., Wang, M., Dunn, J. B., & Palou-Rivera, I. (2011). Life-cycle greenhouse gas emissions of shale gas, natural gas, coal, and petroleum. Environmental science & technology, 46(2), 619-627.
Colborn, T., Kwiatkowski, C., Schultz, K., & Bachran, M. (2011). Natural gas operations from a public health perspective. Human and Ecological Risk Assessment: An International Journal, 17(5), 1039-1056.
ISSU, H. (2013). Methane emissions associated with natural gas production in the United States. PNAS, 110(44), 17601-17602.
Mokhatab, S., & Poe, W. A. (2012). Handbook of natural gas transmission and processing. Gulf Professional Publishing.
Paltsev, S., Jacoby, H. D., Reilly, J. M., Ejaz, Q. J., Morris, J., O’Sullivan, F., & Kragha, O. (2011). The future of US natural gas production, use, and trade. Energy Policy, 39(9), 5309-5321.
