CB&I's NatGas Station

Natural Gas Background

Natural gas is an odorless, colorless, nontoxic and noncorrosive methane-based gas. It is one of the world's most important fuel sources.

Milestones of Natural Gas

Natural gas was formed millions of years ago, but it took some time before people began to figure out what natural gas actually was and how to obtain and use it.

Early Civilization - Natural Gas as a Mystery

Back in early civilization, when natural gas seeped up from the ground, lightning would sometimes strike it, causing the natural gas to ignite and appear as though fire was coming out from the rocks. This led to superstition, myth, and in some cases, the flame was believed to be from the divine. Around 500 BC the Chinese found where the gas was seeping from the ground and using bamboo shoots as a pipeline, transported the gas and used it to boil seawater.

LNG Background

Liquefied natural gas (LNG) has been around for almost 100 years, and since it is an environmentally safe resource that can be transported safely over long distances, it is becoming an increasingly important fuel source to meet rising global demand for energy.

What is LNG?

To transport and store natural gas more efficiently, it is temporarily converted into a liquid as liquefied natural gas or LNG. LNG is still natural gas, but the key thing is its volume has been reduced by a factor of 600 to 1. This volume reduction increases the fuel's energy density and makes it easier to transport from remote areas where natural gas is found to areas where natural gas is in demand.

Milestones of LNG

Although people have been using natural gas for thousands of years, the technology to liquefy natural gas did not exist until 200 years ago. It took another 100 years for a LNG plant to be put into operation.

1800's - Beginnings of LNG

Although people have been using natural gas for thousands of years, it took until the 1820s when British chemist and physicist, Michael Faraday, was able to liquefy natural gas. The next major technological advancement came in 1873 when German engineer Karl Von Linde built the first compressor refrigeration machine. Using Linde's technology, the first LNG plant was built in West Virginia in 1912. The first commercial LNG plant was built about 30 years later in Cleveland, Ohio, where LNG was stored under atmospheric pressure.

Exploration

So how do we go about finding natural gas? We know that natural gas is found beneath the earth's surface, but what is the best way to predict where natural gas deposits will be located? Geologists and geophysicists are the people who can best determine where to drill.

Other tests to confirm natural gas resources

Seismic testing -- where geologists send shock waves or vibrations through the earth's surface and interpret the waves that are reflected back to determine geological properties
Magnetometers -- which measure small changes in the earth's magnetism that could be caused by oil or natural gas
Gravity meters -- which measure small changes in the earth's gravitational field that could be caused by oil or natural gas
2-D, 3-D, and 4-D Seismic Imaging -- which create computer images of what the underground geology might look like based on the previous tests

What happens after an area is thought to contain natural gas?

All of these tests are very useful for predicting where oil and natural gas might be, but the only way to determine whether there actually is natural gas beneath the earth's surface is to drill an exploratory well so geologists can study the layers of rock and know for certain if natural gas is present. This is the most costly method and is done only after all the prep-work is completed and there is a high probability of natural gas in the area.

Unconventional Natural Gas

Traditionally, conventional natural gas has been the easiest and most cost effective to recover, but as technology improves and more unconventional gas is discovered, unconventional gas is becoming more economical to extract and therefore it is playing a bigger picture in the natural gas portfolio. No matter how natural gas is extracted, whether from conventional, unconventional, from tight or deep gas, all natural gas is processed in the same way.

What is Deep Gas?

Deep gas is natural gas that typically lies 15,000 feet below the surface, which is beyond the scope of conventional drilling methods. However, in recent years with advances in exploration and drilling technology, deep gas is becoming more obtainable, although the cost still remains high.

What is Tight Gas?

Tight gas is natural gas that is trapped in impermeable, hard rock, sandstone or limestone with low porosity and low permeability. Because of the tight formations, conventional drilling methods do not work, therefore more expensive fracturing and acidizing techniques must be used. Although natural gas from tight formations is costly, tight gas represents a significant portion of the natural gas portfolio.

What are methane hydrates?

The newest natural gas discovery is methane hydrates or crystallized natural gas. Methane hydrates are methane molecules which have been trapped in a frozen water lattice. It is unclear how many of these hydrates exist, what effect they have on the natural carbon cycle, or on the environment, but research is continuing on whether methane hydrates could be a useful unconventional natural gas resource.

What is Coal Bed Methane?

Similar to natural gas and oil being found together, often times natural gas is present with coal deposits within the coal seams or in the nearby rock. When coal is mined, natural gas is released from the rock but stays trapped underground. Having the gas in the mines is a hazard and dangerous for coal miners. So in the past, to make the mines safer, natural gas was vented to atmosphere. Today, coal seam methane, or coal bed methane is extracted and is another type of unconventional natural gas.

What is Coal Bed Methane?

Similar to natural gas and oil being found together, often times natural gas is present with coal deposits within the coal seams or in the nearby rock. When coal is mined, natural gas is released from the rock but stays trapped underground. Having the gas in the mines is a hazard and dangerous for coal miners. So in the past, to make the mines safer, natural gas was vented to atmosphere. Today, coal seam methane, or coal bed methane is extracted and is another type of unconventional natural gas.

What is Biogas?

Biogas is gas produced when organic matter, such as sewage or plants, breaks down without oxygen forming methane and carbon dioxide. Biogas can be harnessed from swamps, marshes, landfills or sewage treatment plants. When biogas combusts or oxides with oxygen it releases energy and can be used as a fuel. Like natural gas, it can also be liquidized. The methane within biogas can be upgraded to meet standards similar to natural gas and possibly entered into local natural gas distribution networks.

What is Geopressurized Zones?

Of all the unconventional gas reserves, it is estimated that geopressurized zones hold the most gas. Geopressurized zones are layers of clay and sandstone or silt located 10,000 to 25,000 feet underground. These areas are under such high pressures that water and natural gas are compressed out of the clay and enter into more porous rock such as sandstone. Due to the high pressure and the depth of geopressurized zones, natural gas extraction from these areas becomes costly and complicated.

Conventional Natural Gas

Traditionally, natural gas has been discovered in reservoirs below the earth's surface. This type of natural gas is called conventional natural gas. No matter how natural gas is extracted, whether from conventional, unconventional, associated, or non-associated methods, all gas is processed in the same way.

Where is conventional natural gas found?

Conventional natural gas is found underground trapped in porous rock formations. There are two main types of conventional natural gas, associated and non-associated. Associated natural gas is found in reservoirs that also contain oil. Non-associated natural gas fields are simpler and contain only natural gas.

How do we extract natural gas from offshore sources?

Conventional natural gas can also be found offshore, often miles below sea level. Offshore drilling requires an artificial platform or drilling rig to provide a base for the underwater drilling. Factors like where and how deep the drilling site is as well as what type of well will be constructed affect the type of platform that will be built. The platform can float on top of the water, be partially submerged or fixed to the sea bottom.

Environmental

When using fossil fuels, environmental issues are a concern. To decrease environmental impacts, the natural gas industry has put into place initiatives and technology advancements to reduce its carbon footprint. The natural gas industry is constantly developing new technologies to improve efficiency, lower cost, and lessen environmental impacts.

Transportation

Natural gas is often found in remote areas or in areas where natural gas is not in demand. To transport natural gas most efficiently, there are expansive pipeline networks in place throughout the world as well as LNG carriers, or tank ships, to transport natural gas across waterways. In addition, LNG can also be transported by tanker truck or railway if a pipeline system does not exist in a particular area.

How is natural gas transported from wellhead?

Natural gas is extracted from wellheads, sent through gathering pipelines, and then taken to a gas processing facility. In the former Soviet Union, Europe, and North America, there are extensive pipeline systems that take processed natural gas under high pressure to areas with high natural gas demand, usually urban areas. There are many safety features in place throughout the pipelines such as valves, metering stations, and compressor stations to make sure the natural gas is flowing at a safe pressure throughout the pipes. If the natural gas is going to the gas distribution network and to local stations, mercaptan -- the source of the rotten egg smell -- is added to natural gas as a safety feature, so consumers can detect leaks more easily.

Shale Gas

An unconventional gas source that is becoming more economically viable to extract is shale gas. After natural gas is extracted from the shale, it is processed the same way as all other natural gas from conventional and unconventional sources.

Why the recent interest in shale gas?

Although geologists have known of shale gas for years, it has only been recently that advances in hydraulic fracturing and horizontal drilling have made shale gas drilling economical. Horizontal drilling from the surface looks like vertical drilling but has legs underground that can extend up to a mile long and tap multiple gas reserves. This leads to minimal surface disturbances and lowers the drilling's environmental impact.

What is hydraulic fracturing?

Hydraulic fracturing or fracking has been the key to making shale drilling economical because it makes the shale rock more porous and creates channels for natural gas to flow freely. The first step is to drill down to the natural gas reservoir where shell casings are inserted 1,000 to 3,000 feet below the surface. The space between the casings and the drilling holes is filled with cement and then the process is repeated up to 10,000 feet. Once the drilling is complete, water with sand and additives is pumped into the well at high pressures. This creates cracks in the rocks and natural gas can flow upward.

Uses

Natural gas has come a long way from the early days of heating water directly to lighting street lamps to the Bunsen burner. Today, natural gas is used across all sectors. The development of advanced technology and more efficient natural gas transportation has led better economical, environmental, and efficient ways of using natural gas.

Commercial

The commercial sector has very similar natural gas uses as the residential sector. Offices, churches, restaurants, and privately and publically owned businesses use natural gas mainly for space heating, water heating, air conditioning and cooking. Non-heating applications of natural gas are expected to increase because of technological innovations such as natural gas driven cooling processes for commercial cooling, and temperature control for cooking. Heating applications are also being improved with combined cooling heating and power systems which harness heat released from electrical generators and use it to run space or water heaters.

Industrial

The primary industries that use natural gas include the refining, chemical, metal, food processing, pulp, stone, clay, glass, and plastic industries. This sector has very similar uses for natural gas -- lighting, heating, cooling, and cooking -- but also uses natural gas as a feedstock, for drying, dehumidifying, waste treatment, food processing, glass melting and metals pretreating among others. Methanol can also be produced from natural gas which can further be used to produce formaldehyde, methyl tertiary butyl ether (MTBE) – a gasoline additive to raise the octane number, or as a fuel source for fuel cells. Other ways natural gas is being used in industry include:
-- Infrared units to quickly heat materials especially in the metals industry
-- Co-Firing technology which uses natural gas with other fuels such as wood to improve efficiency and reduce emissions
-- Combined cooling heat and power systems like the commercial industry
-- Direct contact water heaters which use energy from natural gas combustion to heat water and achieve up to 99% efficiencies

Electrical

To decrease the level of pollutants released into the air from power plants, natural gas is becoming an alternate fuel choice to generate electricity. Most often, natural gas generates electricity with either a steam generation unit, a gas turbine and combustion engine, or a combination of the two in a combined cycle unit. In a combined cycle unit, hot gas generated from burning natural gas turns a turbine to generate electricity while the waste heat from the process also generates electricity by a steam unit. This process increases the efficiency from 35% to 60%. Distributed generation produces electricity on-site rather than at a power plant. This is done with on-site generators with gas fired turbines, microturbines, fuel cells or gas fired reciprocating engines. Combined heating and power systems can also be tied in with distributed systems to increase efficiency by harnessing heat that would otherwise be wasted.

Transportation

Natural gas is a very important fuel source for the transportation sector, with over 12 million natural gas vehicles (NGVs) in 2009. This number is expected to rise to more than 50 million NGVs within the next 10 years. The majority of these vehicles are part of fuel intensive vehicle fleets such as taxis, buses, and waste collection vehicles. Most NGVs run on compressed natural gas or a combination of compressed natural gas with LNG or gasoline. The benefits of NGVs are a cheaper, cleaner burning fuel that meets stringent environmental standards. Natural gas is also a safer fuel since in the event of an accident, the fuel dissipates into the air instead of leaving a flammable pool on the ground. On the down side, NGVs have a higher initial cost and there are limited refueling stations. Due to the limitations, NGVs are mainly used with large fleet vehicles since they are centrally maintained and fueled. However, with improved technology and more fueling stations, use of NGVs will increase.

Residential

In the residential sector, natural gas is mainly used for heating, cooling, lighting, and cooking. Although there are an increasing number of homes using natural gas, the amount of natural gas consumed in the residential sector hasn't proportionally increased because new technology has led to 80-90% efficiency for natural gas appliances. Some of these appliances, such as air conditioners, have a higher initial cost but are cheaper to run, require less maintenance, and last longer.

Gas Processing

Natural gas used by consumers is a colorless, nontoxic, noncorrosive, methane-based gas. It's much different from the gas that is extracted from the ground or offshore. Raw natural gas contains contaminants and heavier hydrocarbons that must be removed before the gas can be sent into pipelines for delivery to consumers. Gas processing plants perform the necessary steps to prepare raw gas for consumer and industrial use.
Depending on what the composition of the raw natural gas is, the gas processing plant may contain conditioning facilities to remove water, carbon dioxide, hydrogen sulfide, nitrogen, helium and other rare gases. In addition, gas processing facilities remove natural gas liquids (NGLs) which are heavier hydrocarbons that can be sold as separate products. The NGLs are separated into different components in a fractionation facility that can be located at the gas processing plant or at another site. Once the heavies and contaminants are removed, the natural gas is stored, transported by pipeline, or sent to a liquefaction or peak shaving facility.

Liquefaction

LNG is natural gas that has been processed in a liquefaction plant where it is cooled to cryogenic temperatures (approximately -160°C or -256°F) at atmospheric pressure (14.7 psia), converting the vapor to a liquid and reducing its volume by a factor of 600. This process makes it easier and more economical to transport by ship over long distances. Natural gas is delivered by pipeline to a gas liquefaction plant near the producing field.
The liquefaction plant typically has several processing units in addition to a large refrigeration plant that cools and condenses the gas into a liquid. The additional processing units along with ancillary facilities are necessary to:
Manage any associated heavy hydrocarbon liquids
Remove naturally occurring contaminates from the natural gas such as carbon dioxide, hydrogen sulfide, water, and mercury.
Recover ethane, propane, butane and heavier components in the gas to meet LNG specification, produce refrigerant make-up, or produce additional products.
Accumulate and export products.
Provide cooling, heating, utilities, and power.
Protect people and assets.
Provide housing for plant personnel in remote areas.
In some instances the LNG plant may also treat and export natural gas for domestic consumption, requiring additional processing facilities.
Within the natural gas liquefaction plant, several processing units grouped together are referred to as an "LNG train". These units typically include acid-gas removal, dehydration, mercury removal, NGL recovery, liquefaction (including refrigeration systems), heating and cooling systems, and utility distribution. In some plants, the fractionation unit, as well as an end-flash unit may be included within the train.

Regasification

Regasification plant, import terminal, revaporizer: these are all terms often used to describe facilities that receive LNG from a tanker, temporarily store and regasify the LNG and then send it into a pipeline for distribution. These facilities are located in countries where natural gas demand exceeds supply.

Peak Shaving

Local natural gas distribution companies, pipeline operators and natural gas suppliers are required to meet not only the base load supply needs of their customers but also the peak demands as well.
Peak demands are usually seasonal and can be multiples of the normal gas demand. It is both uneconomical to subscribe pipeline capacity for peak demands and also impractical to size natural gas transmission systems for gas demands that may occur only a few days per year. LNG provides a cost effective solution.
Where the geology is not suitable for underground gas storage, LNG peak shaving plants provide a viable alternative. LNG peak shaving plants provide a means of both meeting the peak demands in periods of high usage and mitigating higher prices of natural gas during these periods. This is done by liquefying natural gas purchased at low cost during periods of low demand, storing, and vaporizing it during the period of high demand.
Rather than producing LNG on site, peak shaving can be done by trucking LNG from a remote source. This type of facility that off-loads, stores and vaporizes LNG is called a satellite facility. Import terminals supplied by ship and peak shaving plants with liquefaction capacity can provide LNG to these satellite facilities.