Natural gas is found underground. It is usually found near petroleum and was probably formed at the same time. Natural gas misture of gases that contains mainly methane, which is chemically related to gasoline. Wherever possible, natural gas is used for heating and cooking because it is the cheapest of the gaseous fuel. Enrichedwater gas is sometimes used when natural gas is not available. Natural gas supplies nearly 20 percent of the energy used the world. Deposits are usually found in the same areas as petroleum deposits. Like petroleum, natural gas is a rapidly disappearing resource.