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  • Writer's pictureSarah Whiteford

How do oil pipelines work?

Updated: Aug 23, 2020

We probably know the main avenues for oil to travel: trucks, trains, ships, and pipelines. The first three are easy to visualize, load up the oil and drive it somewhere via land or water. But what about pipelines? According to The World Factbook, there are about 2,175,000 miles (3,500,000 km) of pipelines around the world, but how do they work? Do they just flow, are they pressurized? How efficient are they in transporting oil? You’re about to find out – it’s Fun Fact Friday!

How big is the pipeline network?

We know there are 2,175,000 miles of pipelines around the world, but what portion is oil and gas? According to, in the United States, “There are 218,970 miles of U.S. oil, refined products and natural gas liquids pipeline. This includes over 80,000 miles of crude oil pipelines, over 70,000 natural gas liquids pipeline miles and over 62,000 miles of petroleum products pipeline.” These pipes can transport crude oil to refineries as well as finished or near-finished products to processing, airports, gas stations, or businesses. Due to increased energy demand, oil pipelines have grown 30% in the last 5 years from 2013 to 2017.

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What about natural gas?

Almost 220,000 miles of liquid pipelines is a lot, enough to circle the Earth more than 8 times. Many cars don’t make that kind of trek over their whole lives. But natural gas pipelines are even more ubiquitous. The United States has more than 2.5 million miles of natural gas pipelines, which could circle the Earth more than 100 times! These pipes transfer gas from production to processing centers, then to purification. Smaller distribution lines then move the gas along to homes and businesses. As you can see from the map below, even the major pipelines have a farther reach than oil.

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How big are the pipes?

The size of the pipes varies widely. They are usually between 4 and 48 inches in diameter, made of steel or plastic. Although many photos usually show above-ground pipelines, most pipes are buried 3 to 6 feet under the surface of the Earth. Since damage and corrosion are concerns, they are protected with wood slats, concrete, and sand padding, among other methods. Burying pipelines keeps them safer and out of the way compared to leaving them above ground. You may be wondering about natural gas pipelines, they are similar, but made of carbon steel, and can vary in size from 2 inches all the way up to 60 inches!

Image Credit: Wall Street Journal

How does oil move through the pipe?

Usually, centrifugal pumps are used to pump oil through a pipeline. Depending on topography and the specific type of pipeline, every 20 to 100 miles a pump provides pressure to keep it moving. The pumps operate with electric motors, or in some cases, diesel engines or gas turbines.

Computers control all aspects of the pipeline. Supervisory Control And Data Acquisition (SCADA) systems provide continuous information about the flow, pressure and speed. This continuous flow of data is important since most pipelines run 24 hours a day, 365 days a year. Now, you might be wondering about speed. How fast does oil flow through a pipeline? Oil pipelines are the most efficient way to move oil, but it does take a while. As above, it depends on the terrain, size of pipe, and pressure, but it moves at around 3 to 8 miles per hour, according to Allegro Energy Group. That means oil from Houston, Texas takes 14 to 22 days to get to New York City.

How do companies decide where to build their pipelines?

The best way to start figuring out where to build is following the path of existing pipelines or power sources. This minimizes the impact to the environment and surrounding communities. Balancing the factors of existing right of ways, stakeholders, and environment are all taken into account. Avoiding populated areas as well as areas of cultural significance narrow down the build sites. Then, environmental impact studies are done to ensure no negative effects. Bodies of water are actually tunneled under with horizontal directional drilling, or HDD to keep them at least 100 feet under the bottom of any water.

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Since pipelines travel so far, they cross under creeks, rivers, roads, fields, and parks. Easement agreements are understandings between pipeline companies and property owners concerning the building of a pipeline on private property. The construction area around the pipe can be 25-150 feet, but permanent rights-of-way can be much less. Pipeline companies are responsible for maintaining their right-of-way to protect the environment and people.

How are these pipelines actually built?

As you might imagine, there are a lot of guidelines and laws in place for pipeline construction. But there’s a pretty straightforward process to follow. The first step is to notify regulators and get the proper permits and approvals to build or expand pipelines. Once that is done, the right-of-way is cleared and construction begins. Either a trench is dug to lay the pipe in or a hole is bored if the line needs to go under roads or waterways. Pipe connections are welded together and checked for consistency with x-rays or an ultrasonic scan. Anti-corrosive coating is applied to the welds, and an electric current is installed on the pipe to further protect it from corrosion, called cathodic protection.

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All pieces of a pipeline undergo testing before they go into service. Water is pumped into the pipe and pressurized to check for leaks or other problems. This ensures all valves, flanges and fittings are ready for service.

And that’s it! We want to thank for some fantastic information on the construction of pipelines as well as the maps. They also had the following pipeline construction sequence that explains the stages of building a pipeline very well.

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Happy Friday!

PS – Honorable mention to About Pipelines and their Myth vs. Fact section where they answer a ton of questions about pipelines. It’s definitely worth checking out!


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