What is natural gas?

what is natural gas

What is natural gas?

The term “natural gas” actually describes a mixture of several different naturally occurring gases.  While natural gas is typically made up mostly of methane, it can contain small percentages of other materials, including ethane, butane, propane, and pentane.  The unifying factor among these different gases is that they are all hydrocarbons.  This simply means that these molecules are entirely made up of the elements carbon and hydrogen.  Energy is stored in the bonds between these elements and can be released and harvested through the combustion, or burning, of the hydrocarbon.

Where does natural gas come from?

As apparent in its name, natural gas is the product of naturally occurring processes.  All natural gas in use today began with living organisms.  Living plants, animals, and microbes store energy as complex organic carbon molecules within their bodies.  When these organisms die and decompose, these complex carbon molecules are broken down to eventually form the simpler organic molecules that make up oil and gas.  Certain microbes even produce natural gas as a byproduct of metabolism.  The activity and growth of these organisms gives rise to two main types of natural gas: thermogenic natural gas and biogenic natural gas.

Biogenic natural gas:

Biogenic natural gas occurs as a result of the growth of microorganisms near the surface of the earth.  Certain microbes called methanogens produce methane as a metabolic byproduct–much as humans exhale carbon dioxide.  As these methanogens live and grow, methane accumulates in their underground habitat.  This biogenic natural gas is composed almost purely of methane and can be found in bodies of fine grained sediment  at depths of 10-300 feet underground.

Thermogenic natural gas:

Thermogenic natural gas is the result of chemical reactions that occur without the presence of microorganisms.  These decomposition reactions are instead triggered by the application of extreme heat and pressure.  Due to the depths needed to achieve these extreme conditions, thermogenic natural gas  is typically produced over 3,000 feet underground.  Thermogenic  gas contains higher percentages of non-methane hydrocarbons and is the form of natural gas targeted by drilling operations.

Source Rock vs Reservoir-002

Thermogenic Gas. A diagram of conventional and unconventional gas production techniques.

Thermogenic gas originates in fine grained rock formations with limited permeability, deep underground.  Some common thermogenic gas sources are coal beds, “tight” limestones, and shales.  Inevitably, gas seeps from these less permeable source rocks into conventional reservoir rocks, which include sandstones, sands, fissured limestones , and dolomites.   Gas present in conventional reservoir formations can then be accessed using standard drilling procedures.  While gas trapped in source rocks was previously inaccessible, the advent of fracking technology has made it possible and economical to extract thermogenic gas from source formations such as shales.

How is natural gas used ?

Natural gas has a wide variety of uses and applications that have become an integral component of the modern world economy and lifestyle.  Industrially, natural gas is used as a raw material in the manufacture of everyday items such as fertilizers, plastics, paints, photographic film, dyes, and even pharmaceuticals.

Those same industrial processes often also use electricity produced using natural gas.  Natural gas is a major player in current electricity production, largely replacing coal as the power source for turbines and generators.  In fact, early 2012 saw coal use in electricity production drop to an all-time low of just 34% in the United States.

US Natural Gas Usage

Finally, natural gas is a nearly ubiquitous presence in private residences.  Approximately half of private homes in the US are heated using natural gas combustion.  Natural gas can also be found in common household appliances such as water heaters, clothes driers, and stoves.

 Why is natural gas important?

 Use of natural gas is currently at an all time high.  Approximately one quarter of energy consumed in the US in 2011 was produced using natural gas.  Worldwide demand for liquid natural gas (LNG) doubled in the first decade of the 2000s alone, and is on its way to eclipsing coal and oil as the one of most influential world energy sources.

Aside from simply creating high demand for natural gas, this energy source shift has created repercussions that are keenly felt in the worldwide economic and political spheres.  Historically, the Middle East has been the hub of the fossil fuel industry due to the region’s abundance of oil reserves.  Of the top 10 oil producing nations across the globe, 5 are Middle Eastern states.  Other top producers include Russia, Nigeria, and Libya, with only one North American nation—Canada—ranking among the top 10.  The rise of natural gas as a high demand fuel emphasizes the importance of shale gas and reserves.  Unlike oil reserves, shale gas formations are more common in North America than in any other area of the world aside from China.  The US is also far and away the highest producer of natural gas in the world, giving rise to speculation that North American countries—specifically the United States—could surpass Middle Eastern nations as the leading suppliers in the fossil fuel economy if current trends continue.

The increased production and use of natural gas also carries weighty environmental implications.  In comparison to other fossil fuels, natural gas is a clean burning fuel.  The burning of natural gas results in significantly less emission of carbon dioxide than does the burning of coal or oil.  As coal use in the United States dropped to a record low in the spring of 2012, national CO2 emissions as measured by the Energy Information Administration surpassed the lowest recorded level in the past decade.  However, it is important to note that, while it is an improvement on coal and oil, natural gas is still a carbon based fuel source and combustion will always lead to CO2 production.  Although natural gas use may provide short term environmental relief, the boom in supply of cheap, easy fossil fuel may also cripple research into alternative sources by removing the motivators of urgency and necessity.












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