With more than 18,900 miles of pipeline, MichCon delivers natural gas to 1.3 million homes and businesses in its service area throughout Michigan.

What is Natural Gas?

Natural gas is a combustible, gaseous mixture of simple hydrocarbon compounds that is usually found accumulated inside deep underground reservoirs formed by porous rock. Natural gas is a fossil fuel composed almost entirely of methane although it does contain small amounts of other gases.

Facts About Natural Gas

• It has a flammability range of five to 15 percent. That means that any mixture containing less than five percent or greater than 15 percent natural gas to air would not support combustion.
• It has no color, odor or taste. Mercaptan, which smells like rotten eggs,  is added to natural gas during distribution to give natural gas a distinct unpleasant odor. This acts as a safety device by allowing it to be detected in the atmosphere.
• It has a hydrocarbon molecular structure, which means that almost all components found in natural gas contain only the elements hydrogen and carbon.
• Natural gas is the cleanest burning of all fossil fuels. It burns with a blue flame when completely combusted which produces water and carbon dioxide.
• Natural gas is the ideal fuel. Its production doesn't disturb the surrounding area, and the site is quickly restored to its original state once production ends. Natural gas contains very few pollutants as it is extracted from the ground and the small amount of pollutants that do exist are removed before the gas enters the pipeline.

Sources of Natural Gas

There are two theories about how natural gas is formed:

Scientific Theory

This theory states that natural gas was formed millions of years ago when plants and tiny sea animals were buried by sand and rock. Layers of mud, sand, rock, plant and animal matter continued to build up until the pressure and heat from the earth turned them into a tar-like substance called kerogen.

As temperatures continued to increase and the kerogen continued "cooking," more complex compounds of carbon and hydrogen known as oil were formed. Natural gas was generated at the same time as oil. However, peak generation occurs when oil begins to break down because of high geothermal temperatures (greater than 400 degrees Fahrenheit).

As natural gas molecules form, they migrate from the shale "source rock" into more porous areas such as sandstone. They continue moving to either the earth's surface where they escape into the atmosphere or are trapped when their path is blocked by nonporous rock. In the latter case, the impermeable rock layers cause natural gas accumulation to occur.

The Deep Gas Theory

In 1979, Thomas Gold of Cornell University developed the "deep gas theory" in contrast to the scientific theory  of natural gas's origin. He contended that "on Earth, as in other planets, most hydrocarbons were formed from non-biological sources."

His theory proposes that the earth is made up of primordial materials that combined in space billions of years ago when the basic structure of the earth evolved. The materials are believed still buried far below the earth's crust where they have been trapped for 4.5 billion years.

Cracks and fissures in the earth's crust allow the gases to migrate into reservoirs and to the surface. In this manner, it is believed the supply of hydrocarbons produced from the primordial material was instrumental in the creation of the earth's atmosphere.

The deep gas theory further proposes that oil molecules are capable of surviving greater temperatures and pressures beneath the earth's surface and that many of the hydrocarbons that migrate up to the two- to three-mile depths do break up into methane gas. This would explain the presence of both oil and gas found at two- to three-mile depths. It also supports the theory that a much greater supply of oil is present in "deep wells" that range in depth from 50,000 to 60,000 feet below the earth's surface.

Unconventional Sources of Natural Gas

In the U.S. alone, there are estimates of trillions of cubic feet of potentially recoverable natural gas resources to be found in unconventional sources. These reserves have been largely excluded from the estimates of potential natural gas supplies in U.S. since their recovery has not been reasonably demonstrated.  Our DTE Gas Resources subsidiary is successfully producing unconventional gas from Texas Barnett Shale.

How Natural Gas is Located

To locate natural gas and remove it from the earth, geologic mapping, surveys, and aerial photographs are used. However, recent technology is helping find natural gas more accurately. Some of these methods include:

• Magnetic Measurement — a measure of the magnetic field of base rock to determine how much sediment is lying above it.
• Satellite Imagery — helps identify surface structures and patterns that aid in the search for probable underlying hydrocarbon deposits.
• Gravity Mapping — determines the thickness of the basin or sedimentary rock layer and helps identify base rock topography.
• Seismic Sound Wave Reflection — measures the time to various rock units that reflect acoustic energy.

Processing and Delivery

Natural gas is delivered to about 175 million American consumers through a 1.3 million-mile network of underground pipe. A total of 285,000 natural gas wells, 125 natural gas pipeline companies, and more than 1,200 gas distribution companies provide gas service to all 50 states.

Natural gas reprocessing plants are used to turn hundreds of thousands of cubic feet of unrefined, wellhead natural gas into high-quality commercial natural gas.

1.  Production

Before natural gas is distributed, it first must be sent to a processing or "stripping" plant where it is cleaned and separated. At the processing plant, the natural gas is sent through a separator where secondary byproducts (including oils and impurities) and heavier hydrocarbons (including butane, ethane, and propane) are removed. Most of these byproducts are reprocessed, packaged, and sent to market.

2.  Transmission

As natural gas leaves the processing plant, it enters a compressor station where it is pressurized for transmission. As the pressure is increased, the volume of natural gas is reduced and more natural gas can be filled into the same unit space while the pressure needed to move natural gas through pipelines is achieved.

As natural gas travels through pipelines, some pressure is lost due to fluid friction caused by the natural gas rubbing against the inside walls of the pipes. This loss of pressure is made up at compressor substations located every 50 to 100 miles along the transmission pipelines.

3.  Distribution

Upon reaching a major metropolitan area, some natural gas is diverted through a "city gate" where its pressure is reduced, measured, and sold to the local gas company. From the city gate, the natural gas company distributes the natural gas through an underground network of smaller pipelines called "mains." Smaller lines called "services" connect with the mains and go directly to end-users.

Natural Gas Storage

In summer months when the demand for natural gas is low, natural gas companies can store their excess supply in a number of ways. The most common method is to pipe the natural gas into depleted oil or natural gas reservoirs where it can be stored indefinitely and withdrawn as needed.

Underground storage is used to meet peak winter demand when the capacity of the pipelines cannot deliver what is needed. There are more than 380 underground storage systems operated by 80 companies in 26 states. More than half of the total underground storage systems are located in Illinois, Michigan, Pennsylvania, Ohio, and West Virginia.

Another storage method is converting natural gas to liquid. By reducing its temperature to -259 degrees Fahrenheit, natural gas can be condensed into liquefied natural gas (LNG) which takes up only 1/600th of the space it does as a gas. When LNG is ready to be used, it can be easily converted back to a gaseous form simply by increasing the temperature.