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Major types of natural gas

EBR Staff Writer Published 09 March 2018

Consisting mainly of methane, natural gas is a naturally occurring hydrocarbon gas mixture. The fossil fuel is formed as a result of exposure of layers of decomposing plant and animal matter to intense heat and pressure under the surface of the Earth over millions of years.

Natural gas is extracted by drilling wells into the ground. Later, it is transported to treatment facilities, where impurities such as hydrogen sulfide, helium, carbon dioxide and others are removed from the extracted natural gas. Ethane, propane, butanes and pentanes are some of the by-products of natural gas processing.

The fossil fuel is finding an increased usage in power generation in recent years.  It is also becoming a popular in combined cycle technology used to generate electricity.  It is used as fuel in vehicles and a chemical feedstock in the production of plastics. Besides, it is used as a source for heating and cooking. By using gas to liquids (GTL) technologies, natural gas can also be converted into other liquid products such as liquefied natural gas (LNG).

Found in deep underground rock formations, natural gas is often discovered near petroleum reserves. More than two-thirds of the world's total proven natural gas reserves are located in ten countries. Russia, Iran, Qatar, the US and Saudi Arabia are the major natural gas reserves holding countries. Natural gas that can be easily extracted from the ground is conventional gas. On the other hand, natural gas that is difficult to extract is called as unconventional gas.

Here are the major types of natural gas:

Shale gas: Produced from shale formations, it is an unconventional gas as difficult processes are required to extract it. The techniques followed to extract this type of gas include hydraulic fracturing and horizontal drilling. Shale gas wells rely on fractures to allow the flow of gas to the surface. Hydraulic fracturing is widely used to create fractures in the shale gas extraction process currently. In the US and Canada, shale gas has now become an important source of natural gas.












Image: Natural gas coming out of the ground in Taiwan. Photo courtesy of User: (WT-shared) Naplee12 at wts wikivoyage/Wikipedia.

Deep Natural Gas: It is an unconventional gas that is found deep under the Earth’s surface. While conventional gas is found in deposits that are present a few thousand meters below the ground, deep natural gas is present at the depth of 15,000 meters. Extraction of deep natural gas is found to be economically not feasible in all the cases despite many innovations have been made to improve the techniques in drilling the gas.

Tight gas: It is another type of unconventional natural gas that is found underneath an impermeable rock formation. The location of its reserves makes the process of extracting it difficult. Extraction of tight gas involves high costs and complicated techniques, including fracking. Acidizing is also used to extract tight gas. The tight rock that blocks the flow of gas is broken by injecting acid in the natural gas well.












Image: Natural gas is being drilled from the Marcellus Formation. Photo courtesy of Gerry Dincher from Hope Mills, NC/Wikipedia.

Methane hydrates: It is another type of unconventional natural gas that was discovered in ocean sediments in recent times. Low temperatures and high pressure are required for the formation of methane hydrates. In July 2017, China produced natural gas from methane hydrate in pilot project in the South China Sea. The country’s Ministry of Land and Resources said that a drilling platform deployed off the coast of the southeastern Chinese city of Zhuhai produced 309,000 cubic metres of natural gas, Reuters reported. The drilling platform was installed for 60 days to produce that amount of natural gas.

Coalbed methane: Mostly found in coal beds, Coalbed methane (CBM) is another type of unconventional natural gas. Heavy hydrocarbons such as propane and butane are found in very little quantities in this type of natural gas. Gas contained in coalbed methane mainly consists of methane. As the natural gas found in coal does not contain hydrogen sulphide, it is neither sweet nor sour.

Also, the gas extracted from the coal beds requires minimal processing. It is currently considered as a key source of energy in US, Canada, Australia, and other countries. In Alberta, Canada, the remaining established reserves of CBM are estimated to be nearly two trillion cubic feet, according The Alberta Energy Regulator (AER). In 2016, CBM production in the US stood at 1.02 trillion cubic feet (TCF). Rocky Mountain states of Colorado, Wyoming, and New Mexico are the major CBM producing areas.