Natural gas is a combination of gases formed in the bowels of the earth by the anaerobic decomposition of organic matter. In general, it is an assortment of gaseous hydrocarbons (methane, ethane, propane, butane, etc.) that is formed in the earth’s crust and is extensively used as a highly economical energy source for power plants in the ferrous and nonferrous metallurgy, cement and glass industry, in the production of building materials and for general communal needs, in addition to raw material for many other organic compounds.
Natural gas is a natural resource. It is also often a byproduct gas in oil production. In gas reservoirs or gas cap in oil field, a free gas or dissolved in oil or water, Natural gas can be found in a gaseous state. It is gaseous in normal conditions at 0.101325 MPa and 20 ° C. Additionally to that, natural gas can be in the form of hydrates.
Methane (CH4) is the main part of natural gas (up to 98%). The composition of natural gas may also contain heavier hydrocarbons such as:
- Butane (compound) (C4H10),
- Propane (C3H8),
- Ethane (C2H6).
In addition to methane homologues and other non-carbonic substances:
- Hydrogen (H2),
- Hydrogen sulfide (H2S),
- Carbon dioxide (CO2),
- Nitrogen (N2),
- Helium (Ne2).
Natural gas is colorless and odorless. To determine the leakage by smell, an odorant is added to the gas before giving it to customers. This odorant is a substance having a definite penetrating odor. Usually an odorant may be the Etylmerkaptan (C2H5SH) or a mixture of natural mercaptans (C2H3P). Natural gas contains no odorant during transportation through the pipeline because it is an aggressive substance which may cause the pipe wall corrosion.
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In the earth Natural gas is at a depth from 1,000 meters to several kilometers. Natural gas in the earth is in microscopic cavities, called pores. Microscopic channels or cracks interconnected these pores with each other. Gas comes from the high-pressure pores to the low-pressure pores until it is caught in a chink through these channels. Natural gas is hauling out from the earth through wells. Chinks are placed evenly across the field. This is done for a identical reservoir pressure drop in the deposit or there is prospect of the gas interchange between deposits, in addition to premature deposit flooding.
Natural gas goes up because the pressure in the layer is considerably higher than atmospheric. Therefore, in the layer and collection system driving force is in the different pressure.