The energy resource referred to as natural gas is mainly made up of methane. This molecule has one carbon atom and four hydrogen atoms. When found in its natural state, there are many other gases present that must be removed before the consumer can use it. The other gases are ethane, propane, butanes, and pentanes, along with other larger molecules. It is part of the process of this gas and then sulfur dioxide in small quantities is added. This is done because methane is a colorless, odorless gas and the t-butyl mercaptan is added so a leak of this gas can be recognized because of the explosive nature of the gas.
Natural gas can be found in many places where other energy sources are found because they all rely on the decaying of organic matter for them to materialize. This is evident from the many coal mine explosions when a pocket of this gas is found and leaks into the mine shafts.
Nearly all oil wells have this gas present in the oil itself. In the 1800s and the early 1900s, this gas was not generally sold because the linguistics of transporting and storing it was not cost efficient. As a result, most of this gas was just burnt off at the oil well itself. These types of deposits are called fossil natural gas or associated. Non-associated deposits are referring to deposits of this gas that are isolated from other energy deposits.
Other types of deposits where gas is found are referred to as resource gases. These include sour gas, shale gas, tight gas and, of course, coal bed methane.
The shale gas is the most common source other than the associated gas that is found in the Marcellus shale deposit in the Appalachian Basin. In 2008, there was an estimated 500 trillion cubic feet of natural gas deposits to be present just waiting to be extracted. This is a great domestic energy resource that our country is taking advantage of in a positive manner.