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WHAT IS NATURAL GAS?

Natural gas, in itself, might be considered a very uninteresting gas – it is colourless, shapeless, and odourless in its pure form. Quite uninteresting – except that natural gas is combustible, and when burned it gives off a great deal of energy. Unlike other fossil fuels, however, natural gas is clean burning and emits lower levels of potentially harmful byproducts into the air. We require energy constantly, to heat our homes, cook our food, and generate our electricity. It is this need for energy that has elevated natural gas to such a level of importance in our society, and in our lives.

Natural gas is a combustible mixture of several hydrocarbon gases, including methane (between 70 % and 90 %), ethane, propane, butane and pentane, as well as carbon dioxide, nitrogen and hydrogen sulphide. The composition of natural gas can vary widely, depending on the gas field. Natural gas is referred to as “wet” when hydrocarbons other than methane are present, “dry” when it is almost pure methane, and “sour” when it contains significant amounts of hydrogen sulphide.

Ethane, propane, and the other hydrocarbons commonly associated with natural gas have slightly different chemical formulas, which are outlined in a chart below.

In its purest form, such as the natural gas that is delivered to your home, it is almost pure methane. Methane is a molecule made up of one carbon atom and four hydrogen atoms, and is referred to as CH₄.

Natural gas has many uses: it is used for residential, commercial and industrial purposes. Found in reservoirs underneath the earth, natural gas is frequently associated with oil deposits. Production companies search for evidence of these reservoirs by using sophisticated technology that helps to find the location of the natural gas, and drill wells in the earth where it is likely to be found. When brought from underground, the natural gas is refined to remove impurities like water, other gases, sand, and other compounds. Other impurities are also withdrawn, like hydrogen sulphide (the refining of which can produce sulphur).

Some hydrocarbons are separated and sold individually, including propane and butane. After refining, the clean natural gas is transmitted through a network of pipelines. From these pipelines, natural gas is distributed to its points of use.

Natural gas can be measured in a number of different ways. As a gas, it can be measured by the volume it takes up at normal temperatures and pressures, generally expressed in cubic feet. Production and distribution companies measure natural gas in thousands of cubic feet (Mcf), millions of cubic feet (MMcf), or trillions of cubic feet (Tcf).

While measuring by volume is useful, natural gas can also be measured as a source of energy. Like other forms of energy, natural gas is commonly measured and expressed in British thermal units (Btu). One Btu is the amount of natural gas that will produce enough energy to heat one pound of water by one degree at normal pressure. To give an idea, one cubic foot of natural gas contains about 1,027 Btus. When natural gas is delivered to a residence, it is measured by the gas utility in “therms” for billing purposes. A therm (a unit of heat equal to 1.055 056 × 108 joules) is equivalent to 100,000 Btu’s, or just over 97 cubic feet, of natural gas.

10.Письменно ответьте на вопросы по тексту.

1. What are the advantages of using natural gas?

2. What are the properties of natural gas? What is the composition of natural gas?

3. How does the composition of natural gas vary? When is it called dry, wet, sour?

4. What stages does natural gas go through after being lifted (to the surface)?

5. What are the ways to measure natural gas? Name them.

6. How is natural gas measured being a form of energy?