Natural gas safety world > The travels of natural gas

Get small

Want to know where natural gas comes from? Well, you'll have to use your imagination and get really small. Pretend you're a tiny natural gas molecule, hanging out in a gas trap with other natural gas molecules several miles beneath the earth's surface.

Start Underground

It's dark in there. Luckily, you don't need to breathe because there isn't any air to speak of, just a lot of methane plus some carbon dioxide, butane, ethane, propane, pentane, nitrogen, hexane, heptane and water vapor. You and the other gas molecules have been in this one spot for a very long time—millions of years, in fact.

 

Travels of gas through underground pipelines

Whoosh!

You're cozy and content in your little home. Then one day, out of the blue, you hear a loud roar and whoosh!—you're sucked up through a well and into a huge pipeline.

You and your little gas buddies are pumped through this pipeline to a processing plant. There, you say goodbye to the water vapor, carbon dioxide and other molecules considered impurities. These are removed in a treatment process called "sweetening" the gas.

Next, you are pumped into a network of steel transmission pipes that range in size from 20 to 42 inches in diameter. If you could make a sound, you would probably be able to hear it echo inside these big pipes.

Under pressure

About every 50 to 60 miles you pass through a compressor station. Compressor stations compress (squeeze) you to push you to the next station along the line.

The compressor station works kind of like a hand around a tube of toothpaste. Squeezing the bottom of the tube causes the toothpaste to flow out the top. And the harder it's squeezed, the faster it flows. Likewise, the harder the compressor stations pressurize you, the faster you flow.

You and the other gas molecules are tightly packed together now, and you feel as if you are being pushed quickly through the pipes from behind. Compressing a gas reduces its volume, so many more of you now fit into a smaller space. Not much elbow room left, so it's lucky you don't have elbows!

Travels of gas through underground pipelines

A fork in the road

You continue traveling through the pipeline until you reach a fork—a place where the pipe splits off in different directions. Some of your friends are sent down one fork of the pipeline to distribution companies, where they are put into storage tanks for future use. The rest of you move on to a natural gas utility—a company that delivers natural gas to homes and businesses.

Once you reach the gas utility, your pressure is reduced and a chemical called mercaptan is added to you. You had no odor before, but now you can barely stand your own smell. Mercaptan contains sulfur and makes you smell like rotten eggs. It's added so people will be able to tell if natural gas is leaking from their natural gas pipes or appliances.

Under the street

From the gas utility, you travel through small pipes called distribution mains. These pipes are between 2 and 24 inches in diameter and run below the streets. You zip along under the street, hearing the rumble of traffic overhead.

All of a sudden, the pipeline you were in gets smaller, and smaller again. Now you are in a service line that leads from the distribution main to a house. You are about to go through a gas meter! You're about to be used in someone's home! The gas meter measures the amount of gas used in the home, just as an electric meter measures electricity usage. The gas company uses this information to figure out how much to charge on people's gas bills.

Travels of gas to appliance

Journey's end

Before entering the meter, you go through a gas pressure regulator where your pressurization is reduced. Then, you whiz through the meter and into gas lines—pipes that are an inch wide or less. You can relax a little now, because you're not under as much pressure. But you continue to bounce around with excitement, eager to find out which appliance you'll serve. Will it be the gas range in the kitchen? The gas clothes dryer? The water heater? The furnace? Whichever it is, you hope you'll be put to good use.

Molecule. The smallest part of a substance that has all of the chemical properties of that substance.
Gas Trap. An arrangement of three types of rock that geologists look for when searching for natural gas: the source rock that produces the natural gas, the porous reservoir rock that holds the natural gas, and the cap rock that keeps the gas from escaping.
Methane. A hydrocarbon gas that is the main ingredient in natural gas. Methane molecules each contain one carbon atom and four hydrogen atoms.
Carbon dioxide. A colorless, odorless, nonpoisonous gas that is a normal part of the air we breathe. Carbon dioxide is exhaled by humans and animals, and is absorbed by green growing things and by the sea. Carbon dioxide molecules each contain one carbon atom and two oxygen atoms.
Butane. A hydrocarbon gas that is one of the ingredients in natural gas. Butane molecules consist of four carbon atoms and ten hydrogen atoms.
Ethane. A hydrocarbon gas that is one of the ingredients in natural gas. Ethane molecules each contain two carbon atoms and six hydrogen atoms.
Propane. A hydrocarbon gas that is one of the ingredients in natural gas. Propane molecules each contain three carbon atoms and eight hydrogen atoms.
Pentane. A hydrocarbon gas that is an ingredient of natural gas. Pentane molecules each contain five carbon atoms and twelve hydrogen atoms.
Nitrogen. A gas that is an ingredient of natural gas. Nitrogen molecules each contain two nitrogen atoms.
Hexane. A hydrocarbon gas that is an ingredient of natural gas. Hexane molecules each contain six carbon atoms and fourteen hydrogen atoms.
Heptane. A hydrocarbon gas that is an ingredient of natural gas. Heptane molecules each contain seven carbon atoms and sixteen hydrogen atoms.
Processing plant. A place where natural gas is treated to remove impurities.
Transmission pipes. A network of large steel pipes that carries natural gas from processing plants to utilities.
Compressor station. A place where natural gas is pressurized to be sure it flows effectively through pipes.
Volume. The amount of space taken up by something.
Storage tanks. Large aboveground or underground tanks used to store natural gas for future use.
Utility. A company or other organization that provides a public service, such as supplying electricity, natural gas, or water.
Mercaptan. A chemical added to natural gas that makes it smell like rotten eggs so people will know if natural gas is leaking.
Distribution main. Underground pipelines that carry natural gas from utilities to homes, businesses, and schools.
Service line. A pipeline that carries natural gas from a distribution main up to the gas meter at a building.
Gas meter. A device that records how much natural gas is being used in a building.
Gas lines. Small pipes (1/4 to 1 inch in diameter) that carry natural gas to home appliances.
Appliance. A device used in the home to perform domestic chores, such as a clothes dryer, dishwasher, refrigerator, toaster, etc.
Well. A hole drilled or bored into the earth to bring up water, sulfur, natural gas, or petroleum.

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