Natural gas is a combustible mixture of hydrocarbon gases.
It is abundant and when burned, gives off a great deal of energy with fewer emissions than many other sources. Compared to other fossil fuels, natural gas is cleaner burning and emits lower levels of potentially harmful byproducts into the air.
It is formed primarily of methane, it can also include ethane, propane, butane and pentane. It is a fossil fuel used as a source of energy for heating, cooking, and electricity generation.
Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates.
Petroleum is another resource and fossil fuel found in close proximity to and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments.
Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material. (1,2,3)
When wet natural gas is produced, it must be processed to separate the different components it contains, such as water and hydrocarbons.
Natural gas liquids (NGLs), such as butane, ethane (ex. used to make plastics) and propane, are other forms of hydrocarbons, which can be used for many different products.
Butane is commonly known as the flammable liquid in handheld lighters, propane is often used for heating in homes or as a fuel source for grills and propane is a chemical building block found in many different kinds of plastic products we use every day.
Also, the propane and other lighter compounds found in the LNGs may be marketed as liquefied petroleum gas (LPG), and heavier hydrocarbons may be made into gasoline (petrol).
The average American citizen will come into contact with at least one product each day which can trace its roots back to wet natural gas.
Everything from phone cases to food containers to tires to gasoline to fibers inside every kind of carpet is derived in part from a natural gas liquid. (4,5)
Dry natural gas is essentially made up entirely of methane, and not much else. This means that the methane will burn at correct temperatures for use in things like our stoves, in vehicles and in manufacturing processes.
Dry natural gas can also be used on our area of extraction to power vehicles, drilling rigs and other operations involving the industry, which reduces the need for using other fuels like gasoline and diesel.
After minimal processing, dry natural gas flows into pipelines which are strategically placed across the country delivering it to homes, businesses, manufacturers, agricultural centers and power generation plants.
The methane separated from the wet gas mixture also flows into these pipelines.
Natural gas recently overtook coal as the largest source of electric production in the United States, which in turn has helped to decrease our country’s carbon emissions to levels not seen in decades. (4,5)
Main Components of Natural Gas
Natural gas is stripped down to methane before being used by consumers. It is the most rich component of pure natural gas, which is highly combustible and can be used for a wide range of energy purposes.
The chemical formula of methane is CH4 with molecular weight of 16 gram/mole.
Before methane can be burned, it first has to be stripped from the natural gas that’s found in oil wells, gas wells and condensate wells. Once processed from the natural gas, it is used for generating electricity through gas and steam turbines.
It is also sent to homes through pipelines where it’s used for cooking, heating, air conditioning and other important home activities.
The chemical formula of methane is C2H6 with molecular weight of 30 gram/mole. Ethane is the next most abundant component of energy found in natural gas. It is a hydrocarbon and a byproduct of petroleum refining.
With a higher heating value than methane, it is used in several ways after being isolated from natural gas.
Once separated from natural gas, ethane is often used to produce ethylene and polyethylene products. In turn those are used to produce packaging, trash liners, insulation, wire and other consumer products.
Propane is an abundant energy source found in natural gas and is processed in gas or liquid form. The chemical formula of methane is C3H8 with molecular weight of 44 gram/mole.
Often found in pipeline gas, propane can be used for a variety of purposes.
Frequently, it is used for fueling engines, cooking with stoves and for central heating within the home or larger buildings. Propane is also used for many barbecue grills due to its high-energy output and portability.
Some buses and larger vehicles are fueled on propane, and many homes also use the gas for fueling the furnace, water heaters and other essentials.
Butane is found in natural gas, butane is not as abundant as other hydrocarbons, but it is still a viable energy source and can be used for a variety of purposes.
The chemical formula of methane is C4H10 with molecular weight of 58 gram/mole. Isolated during natural gas processing, butane makes up around 20 percent of natural gas composition.
It is often a component in automobile gas. Refrigeration units and lighters also use a large amount of butane as fuel. Aerosol cans use butane as a propellant, but this has been flagged as harmful to the environment.
Where is natural gas found?
Natural Gas is mainly extracted from the petroleum deposits deep beneath the earth. In fact, it occurs just above the layer of crude oil, as gases are lighter than oil. It is formed through the same process through which petroleum is formed.
High temperatures and pressure leads to the conversion of the remains of plants and animals buried under the earth into naturally occurring gas along with petroleum and coal. Gas reservoirs differ greatly, with different physical variations affecting reservoir performance and recovery.
In a natural gas (single-phase) reservoir it should be possible to recover nearly all of the in-place gas by dropping the pressure sufficiently. If the pressure is effectively maintained by the encroachment of water in the sedimentary rock formation, however, some of the gas will be lost to production by being trapped by capillarity behind the advancing water front.
Therefore, in practice, only about 80 percent of the in-place gas can be recovered. On the other hand, if the pressure declines, there is an economic limit at which the cost of compression exceeds the value of the recovered gas.
Depending on formation permeability, actual gas recovery can be as high as 75 to 80 percent of the original in-place gas in the reservoir. Associated gas is produced along with the oil and is separated at the surface. (3)
Unconventional gas reservoirs
Substantial amounts of gas have accumulated in geologic environments that differ from conventional petroleum traps.
This gas is termed unconventional gas and occurs in “tight” (i.e., relatively impermeable) sandstones, in joints and fractures or absorbed into the matrix of shales, and in coal seams.
Unconventional gas sources are unconventional only in the sense that, given current economic conditions and states of technology, they are more expensive to exploit and may produce at much slower rates than conventional gas fields.
However, as technology changes or as conventional sources become relatively expensive, some unconventional gas becomes easier and relatively cheaper to produce in quantities that can fully complement conventional gas production.
Such has been the case with tight gas, shale gas, and coal-bed methane.
Tight gas occurs in either blanket or lenticular sandstones that have an effective permeability of less than one millidarcy (or 0.001 darcy, which is the standard unit of permeability of a substance to fluid flow).
These relatively impermeable sandstones are reservoirs for considerable amounts of gas that are mostly uneconomical to produce by conventional vertical wells because of low natural flow rates.
However, the production of gas from tight sandstones has been greatly enhanced by the use of horizontal drilling and hydraulic fracturing, or fracking, techniques, which create large collection areas in low-permeability formations through which gas can flow to a producing well.
Shale gas was generated from organic mud deposited at the bottom of ancient bodies of water. Subsequent sedimentation and the resultant heat and pressure transformed the mud into shale and also produced natural gas from the organic matter contained in it.
Over long spans of geologic time, some of the gas migrated to adjacent sandstones and was trapped in them, forming conventional gas accumulations.
The rest of the gas remained locked in the nonporous shale. In the past the production of shale gas was generally too slow to be profitable, but now wells can be drilled horizontally for long distances through the shale beds, and the formations can be stimulated by hydraulic fracturing to enhance gas production greatly.
About 25 percent of the gas produced in the United States comes from shales, and that proportion is expected to rise to 50 percent before the mid-21st century.
Considerable quantities of methane are trapped within coal seams. Although much of the gas that formed during the initial coalification process is lost to the atmosphere, a significant portion remains as free gas in the joints and fractures of the coal seam; in addition, large quantities of gas are adsorbed on the internal surfaces of the micropores within the coal itself.
Since coal is relatively impermeable, the existing fracture systems of seams that contain rich reserves of methane are sometimes stimulated by fracking in a manner similar to shales and tight sandstones.
Geo-pressured fluids and methane hydrates
Geo-pressured reservoirs exist throughout the world in deep, geologically young sedimentary basins in which the formation bear a part of the overburden load. The fluid pressures can become quite high, sometimes almost double the normal hydrostatic gradient.
Methane hydrates have been found in sandstones from polar regions and in sand and mud sediments from continental margins. Techniques for extracting the methane in an economically viable and environmentally sustainable manner are under exploration. (2,3)
World’s largest natural gas producing countries
The largest natural gas fields are the super giants, which contain more than 850 bcm (30 tcf) of gas, and the world-class giants, which have reserves of roughly 85 to 850 bcm (3 to 30 tcf).
Super giants and world-class giants represent less than 1 percent of the world’s total known gas fields, but they originally contained, along with associated gas in giant oil fields, approximately 80 percent of the world’s reserves and produced gas.
Following countries are producing most of the gas of the world. Natural gas production in 2017, by country. (3,9)
1. United States of America 734.5 billion cubic meters
2. Russia 635.6 billion cubic meters
3. Iran 223.9 billion cubic meters
4. Canada 176.3 billion cubic meters
5. Qatar 175.7 billion cubic meters
6. China 149.2 billion cubic meters
7. Norway 123.2 billion cubic meters
8. Australia 113.5 billion cubic meters
9. Saudi Arabia 111.4 billion cubic meters
10. Algeria 91.2 billion cubic meters
Natural Gas Storage
Natural gas, like most other commodities, can be stored for an indefinite period of time. The exploration, production, and transportation of natural gas takes time, and the natural gas that reaches its destination is not always needed right away, so it is injected into underground storage facilities.
These storage facilities can be located near market centers that do not have a ready supply of locally produced natural gas. Traditionally, natural gas has been a seasonal fuel. That is, demand for natural gas is usually higher during the winter, partly because it is used for heat in residential and commercial settings.
Stored natural gas plays a vital role in ensuring that any excess supply delivered during the summer months is available to meet the increased demand of the winter months.
Natural gas in storage also serves as insurance against any unforeseen accidents, natural disasters, or other occurrences that may affect the production or delivery of natural gas. (2,3)
Base Load vs. Peak Load Storage
There are basically two uses for natural gas in storage facilities: meeting base load requirements, and meeting peak load requirements. As mentioned, natural gas storage is required for two reasons: meeting seasonal demand requirements, and as insurance against unforeseen supply disruptions.
Base load storage capacity is used to meet seasonal demand increases. Base load facilities are capable of holding enough natural gas to satisfy long term seasonal demand requirements.
Types of Underground Storage
Underground natural gas storage fields grew in popularity shortly after World War II. At the time, the natural gas industry noted that seasonal demand increases could not feasibly be met by pipeline delivery alone. In order to meet seasonal demand increases, the deliverability of pipelines (and thus their size), would have to increase dramatically.
However, the technology required to construct such large pipelines to consuming regions was, at the time, unattainable and unfeasible. In order to be able to meet seasonal demand increases, underground storage fields were the only option. As mentioned, there are three main types of underground natural gas storage facilities.
Characteristics of depleted reservoirs, aquifers, and salt caverns
Depleted Gas Reservoirs: The first instance of natural gas successfully being stored underground occurred in Weland County, Ontario, Canada, in 1915.
This storage facility used a depleted natural gas well that had been reconditioned into a storage field. In the United States, the first storage facility was developed just south of Buffalo, New York.
By 1930, there were nine storage facilities in six different states.
Prior to 1950, virtually all natural gas storage facilities were in depleted reservoirs. The most prominent and common form of underground storage consists of depleted gas reservoirs.
Depleted reservoirs are those formations that have already been tapped of all their recoverable natural gas.
This leaves an underground formation, geologically capable of holding natural gas. In addition, using an already developed reservoir for storage purposes allows the use of the extraction and distribution equipment left over from when the field was productive.
Aquifers: Aquifers are underground porous, permeable rock formations that act as natural water reservoirs. However, in certain situations, these water containing formations may be reconditioned and used as natural gas storage facilities.
As they are more expensive to develop than depleted reservoirs, these types of storage facilities are usually used only in areas where there are no nearby depleted reservoirs.
Aquifers are the least desirable and most expensive type of natural gas storage facility for a number of reasons. First, the geological characteristics of aquifer formations are not as thoroughly known, as with depleted reservoirs.
A significant amount of time and money goes into discovering the geological characteristics of an aquifer, and determining its suitability as a natural gas storage facility.
Salt Caverns: Underground salt formations offer another option for natural gas storage. These formations are well suited to natural gas storage in that salt caverns, once formed, allow little injected natural gas to escape from the formation unless specifically extracted.
The walls of a salt cavern also have the structural strength of steel, which makes it very resilient against reservoir degradation over the life of the storage facility.
Essentially, salt caverns are formed out of existing salt deposits. These underground salt deposits may exist in two possible forms: salt domes, and salt beds.
Salt domes are thick formations created from natural salt deposits that, over time, leach up through overlying sedimentary layers to form large dome-type structures.
Shipping and Transportation
The transportation of liquefied natural gas(LNG) refers to any movement or shipping of natural gas while in its liquid form. The two major methods of transporting LNG are by pipeline and vessel.
LNG flows efficiently through pipelines so is a preferred method of transporting natural gas. Most LNG pipeline infrastructure takes the LNG between liquefaction facilities and storage facilities, from storage facilities to tankers, and from tankers to re-gasification facilities.
LNG is much denser than compressed natural gas (CNG). This means that much higher amounts of gas are able to be transported for the same volume flow.
The downside is that LNG pipelines are difficult and costly to construct. As LNG requires a temperature of -160°C (-260°F) to remain in its liquid form, significant insulation must be incorporated into LNG pipelines in order to maintain this low temperature and ensure no re-gasification occurs.
This normally includes a combination of mechanical insulation, for example glass foam and a vacuum layer. This complex insulation system makes LNG pipelines significantly more difficult and expensive to manufacture than standard natural gas pipelines. (3)
Liquefied natural gas vessels
The majority of worldwide LNG exports take place at an intercontinental level, meaning that shipping LNG across the ocean is often required. This is done with the use of an LNG vessel or LNG ship, which transports large quantities of LNG between export and import terminals.
Several types of LNG vessels exist in the industry today, with the main one being referred to as an LNG tanker.
Advantages of Natural Gas
a) The largest single application for natural gas is as a fuel for electric power generation. Power generation is followed by industrial, domestic, and commercial uses—mainly as a source of energy but also, for instance, as a feedstock for chemical products.
Several specialized applications have developed over the years.
The clean-burning characteristics of natural gas have made it a frequent choice as a nonpolluting transportation fuel. Many buses and commercial automotive fleets now operate on compressed natural gas.
Carbon black, a pigment of colloidal dimensions, is made by burning natural gas with a limited supply of air and depositing the soot on a cool surface.
It is an important ingredient in dyes and inks and is used in rubber compounding operations.
Natural Gas was used mainly for street and household lighting in the 19th and 20th century. Now, it has a lot more uses in the homes and industrial applications.
b) It is used to turn turbines for wind and solar energy generation. This fossil fuel is used for the production of ammonia which itself is used for making fertilizers. It is a domestic fuel as well. It fires stoves in our houses and also runs heaters, ovens, boilers, etc.
c) Compressed Natural Gas or CNG, that is gas stored at high pressure, is also used in some households for heating and cooking purposes. CNG is also a cheap and environment friendly alternative for a transportation fuel used in low load vehicles requiring high fuel efficiency.
Liquefied Natural Gas or LNG is used to power vehicles such as off-road trucks and trains.
d) Natural Gas is a cleaner fuel. It is less harmful to the environment than coal, petrol or diesel as it has less carbon dioxide emissions. It can be easily stored and transferred through pipelines. It is relatively more abundant than other fossil fuels i.e. coal and petroleum.
e) It is also a safer fuel, as it is lighter than air and dissipates rather than exploding. It provides instant energy, which is why it is used in oven cooking, as it does not require pre-heating
f) More than half of the world’s ammonia supply is manufactured via a catalytic process that uses hydrogen derived from methane. Ammonia is used directly as a plant food or converted into a variety of chemicals such as hydrogen cyanide, nitric acid, urea, and a range of fertilizers.
g) A wide array of other chemical products can be made from natural gas by a controlled oxidation process—for example, methanol, propanol, and formaldehyde, which serve as basic materials for a wide range of other chemical products.
Methanol can be used as a gasoline additive or gasoline substitute. In addition, methyl tertiary butyl ether (MTBE), an oxygenated fuel additive added to gasoline in order to raise its octane number, is produced via chemical reaction of methanol and isobutylene over an acidic ion-exchange resin.
Disadvantages of Natural Gas
Despite its numerous uses, natural gas does have some disadvantages. (6,7)
a) Gas Leaks: Gas line leaks in commercial and residential settings don’t happen too often, but when they do, they pose a significant threat. When a large amount of gas collects in an enclosed area, it may lead to an explosion.
Additionally, individuals exposed to the buildup may become ill. Before distributing it to consumers, natural gas suppliers add a scent to the odorless gas. Regular inspections and proper gas line installation help prevent gas leaks from occurring.
b) Carbon Monoxide Poisoning: Malfunctioning natural gas furnaces may emit poisonous carbon monoxide gas. When individuals inhale carbon monoxide it deprives them of necessary oxygen. Sustained exposure to carbon monoxide will incapacitate, and eventually kill, an individual.
Have a licensed repair technician inspect your natural gas-burning heaters and appliances every year to ensure the gas is burning properly. Install carbon monoxide detectors throughout your home, and check often to make sure they are functioning properly.
Avoid heating your house with a gas oven or your bedroom with a gas or kerosene space heater. These preventative measures will reduce your risk of carbon monoxide exposure from natural gas heaters and appliances.
c) Air Pollution: While natural gas doesn’t emit the same amount of greenhouse gases as other fossil fuels, it does release carbon dioxide, a greenhouse gas. An excess of greenhouse gases in the atmosphere further expedites the rate at which the planet grows warmer, according to the Environmental Protection Agency (EPA).
In addition to its negative effect on the atmosphere, natural gas production, storage and shipping poses a threat to the environment. Small amounts of methane, another greenhouse gas, may escape during these processes.
d) Water Pollution: In recent years, studies have shown that the process gas companies use to drill may contaminate nearby water sources. The process, known as hydraulic fracturing, injects highly pressurized sand and drilling fluid into the ground.
In a 2009 study, the EPA found that 11 out of 29 wells located near a natural gas drilling site in Wyoming contained traces of harmful materials, including heavy metals, oil and gas. In March 2010 the EPA announced it would begin an extensive study of the impact hydraulic fracturing may have on the environment and on human health.