What is Natural Gas?
How dead stuff came to run the world
What does the world run on? Love? Well … okay, maybe you have a point there, so let’s try this again. What do all the world’s cities, machines, vehicles, equipment, tools and electronic devices run on?
You got it … ENERGY!
And for most of the world, fossil fuels are the main source of energy. These include oil, gasoline, diesel, natural gas, and coal. You know what a fossil is, don’t you? It’s the remains of a prehistoric creature that have been preserved in rock over long periods of time.
This is a fossil.
So is this.
But guess what. If you really think about it, these are fossils, too.
That’s right; most of the world’s energy is made from dead stuff, living things that died millions of years ago and were converted into something else.
I’ll have ten litres of dinosaur, please!
You’ve probably already heard that fossil fuels come from dinosaurs, and that’s partially true. But there’s more to it than that. Millions of years ago, dinosaurs were on top of the food chain. They were kings of the planet. And somehow, they all died out, although nobody really knows why for sure.
And some dinos probably did end up in our gas tanks, but there were never enough of them to have been converted into the trillions of tons of fossil fuels that lie beneath the earth. They had lots of help from every other life form that has ever swum, crawled or walked upon the surface of the Earth.
And most of this took place millions of years before the dinos even turned up!
Here’s how it happened
Most scientists believe that the earth is several hundred million years old. Long before mammals evolved — and yes, that includes humans — the Earth was teeming with life. There were dense prehistoric forests, and the sea was filled with microscopic creatures, shellfish, worms, or even larger fish and sea animals. Primitive land animals roamed the earth, and fought, hunted and lived out their lives.
And like all living things, they eventually died. They sank to the sea bed and the bottoms of rivers. They fell to the ground.
Over time, they were covered with mud and silt. And that’s just the start.
Oh, the heat! Oh, the pressure!
Century after century, flood after flood, the layers of mud covering these billions of creatures built up. The layers became heavier, and deep in the earth the temperature rose. In addition, the earth was crawling with bacteria that lived on the decaying material.
What perfect conditions for the formation of fossil fuels!
The heat, pressure, and bacterial activity over enormous spans of time changed the decaying plant and animal matter into oil, natural gas, and coal, among a few other substances.
How fossil fuels are found
It would be easy if there were lakes of fossil fuels out there, and we could just hook up pumps and pipelines and suck out all that great, valuable stuff to use. But the layers of silt and mud have hardened over time to solid rock. And in many cases, these pockets of oil are hundreds of feet under the sea or land.
So we need to look for them. We explore, just like travellers searched for gold or buried treasure. Exploration is very expensive, because it requires sophisticated equipment and knowledgeable engineers, geologists and technicians.
Boom, boom, boom!
Exploration for fossil fuels is usually done by seismic survey. It can be done on land using a truck, or on the sea using a boat. Equipment is used to send waves of sound, loud BOOMS, into the earth. The way the sound moves, and how it echoes, tells technicians what type of material lies below the surface. For example, sound moves in rock differently from how it moves in oil or water.
This way, they can actually draw “sound maps” that show in great detail what types of material lies buried deep below the surface. This is how we identify deposits of oil and gas.
Sometimes, the search reveals that there isn’t enough fuel in a deposit to make the cost of digging worth it. Sometimes, it’s too difficult to get to. Sometimes, there isn’t anything valuable there at all. Millions of dollars spent on exploration are lost.
But sometimes, we get lucky! If the survey results say that there may be large amounts of fuel in an area, the next step is to get samples of the rock for analysis. If the results are positive, we go drilling.
How natural gas is brought to the surface
Natural gas and oil can be found together in the same reservoir, or in separate deposits. We call gas that is found together with oil “wet gas” and gas that is found on its own “dry gas”. Both are valuable fossil fuels.
To get to the gas, companies build huge towers called platforms. There are many of them out in the sea off the south-east coast of Trinidad, near Guayaguayare, and off the north-west coast, if you care to look. At night, the lights twinkle like stars!
Companies use huge drills to penetrate deep into the earth, creating wells. Once the well reaches gas, the gas moves up through pipes to the surface. It is pumped into large pipelines.
Many other companies drilling in the area send their gas on to NGC’s platforms, and into their pipelines. These pipelines lie across the ocean floor for miles, until they come to shore at Beachfield, near Guayaguayare.
Because the gas has spent such a long time deep in rock, it is usually mixed with dirt, mud and water. If it is sent directly to NGC’s consumers, who use gas in their factories, those impurities would ruin their expensive equipment.
So NGC has a huge facility at Beachfield where the gas is “scrubbed”. This means that all impurities are removed. The mud and dirt are safely discarded, but there are also liquid fossil fuels that are sent to separate tanks, and then sold.
So now we have clean, dry gas in our pipelines. What do we do next?
Phoenix Park Gas Processors Limited
Surprise, surprise; natural gas isn’t just a single gas. It is made up of many different gases, such as methane, ethane, butane, propane, and pentane. All of these are made up of the same two atoms, hydrogen and carbon, so they are all called hydrocarbons. But the atoms are arranged in different numbers and shapes.
(images of hydrocarbons)
Gases are termed “heavy” or “light” depending on how many atoms make up each type of molecule. As you can see, pentane is much heavier than methane.
Phoenix Park Gas Processors Limited (PPGPL) is a gas processing plant located on the Point Lisas Industrial Estate in Couva. It is owned by NGC and some other companies. At PPGPL, each of the gases that make up the natural gas stream is separated and removed.
How gas is separated
How do you split up a number of gases when they are all mixed together, and all look the same? It’s easy if you understand that each gas turns to a liquid at a different temperature.
At PPGPL, the gas is sent to a huge refrigeration chamber, where the temperature is lowered to the point at which the heaviest gas turns to a liquid. This liquid falls to the bottom of the chamber, and is removed and stored in a tank.
The temperature is lowered again, and the next heaviest gas becomes a liquid. It is removed and stored.
PPGPL sells liquid gasoline and the heavier gases such as butane and propane, to consumers. The gas that is left is mainly methane and a little ethane. It goes back into NGC’s pipeline. If you’d like to know more about the journey of the gas through NGC’s pipelines, click on Natural Gas Safety.
What happens next to the gas?
We’re glad you asked. The companies on the Point Lisas Industrial Estate, and those on smaller industrial estates, appreciate the fact that the gas is now free of impurities and heavier gases. They use the gas to produce chemicals such as ammonia, methanol and urea, and for heating of furnaces to process iron and steel.
A large percentage of natural gas goes to electricity generation plants in Port of Spain, at Union Industrial Estate at La Brea, and at the Cove Estate in Tobago.
Smaller companies also use natural gas for baking, heating water, and in their air conditioning systems.
Liquefied Natural Gas (LNG)
Trinidad and Tobago is a large exporter of natural gas. Natural gas travels across the country via pipeline, but what do you do if you wanted to sell gas to companies in North America or Europe? Would you build thousands of kilometres of pipeline across the ocean?
That would be next to impossible to accomplish, and way too expensive even if we could. The solution is to transport the gas by ship. But gas is like air; a little of it takes up a lot of space. You would probably use more energy shipping a tank full of natural gas to another country than the amount you could put into the tank!
The solution is to freeze the natural gas until it becomes a liquid. This way, you can fit 600 times more natural gas into a tanker! That’s certainly worth the trip.
Large amounts of gas are liquefied at Atlantic LNG in Point Fortin. It is pumped into tanks and sold overseas. The tanks that are kept at very low temperatures throughout the journey so the gas remains liquid.