Natural gas is one of the most widely used fuels in the world. Its advantages include automatic delivery, perfect heat control, and freedom from dust, ashes, and smoke as well as from the labor and complicated machinery needed to handle solid or liquid fuels. Its principal disadvantage is that it is difficult to store under pressure and is therefore not a suitable fuel for automobiles, locomotives, ships, or airplanes.
Natural gas is composed principally of methane, the lightest of the hydrocarbons, but includes small quantities of propane and butane, also other hydrocarbons of higher molecular weight. Natural gas, obtained from wells in the same manner as petroleum, is found both in petroleum wells and in many wells that contain only gas.
Natural gas is widely distributed throughout the world. The largest natural-gas deposits in the United States are in the Southwest and the Great Plains (Texas, Louisiana, Oklahoma, and Kansas), the western Appalachians and the upper Ohio Valley (Pennsylvania, West Virginia, Kentucky, and Ohio), and in California. A huge pipeline system carries gas from these producing areas to all other parts of the country. Some gas, called dry gas, may be fed directly from the wells into the pipelines; other gas, called wet gas, must first be specially treated. When gas wells produce more gas than may currently be needed, the excess is stored for future use in huge underground reservoirs.
Bottled gas, which can be stored in tanks and is often used in rural areas that are not connected to natural-gas pipelines, is a product of petroleum refining and therefore does not have the same composition as natural gas, which comes directly from wells.
