A Guide to Oil and How it is Formed

Jul 17 2018

One of the most valuable resources on earth is oil as it is used in homes, cars, and a range of other products. On average, in the United States, people use more than 19 million barrels of oil per day. Given the large amounts of oil used every year, it is essential to understand the process of making it so that it can be used in a sustainable way.

What is Oil?

Oil is defined as a fossil fuel that is made from hydrogen and carbon. Oil takes an extremely long time and highly specific conditions to form, and most of it that is used presently began forming millions of years ago.

Approximately 10% of the oil that is harvested currently was formed during the Paleozoic age, which fell between 541 and 252 million years ago. The majority of oil was formed during the Mesozoic era, which occurred between 252 and 66 million years ago. The last 20% formed during the Cenozoic age, around 65 million years ago.

How is it Formed?

How is oil really formed? It begins with ancient shallow oceans and the tiny organic matter that called those oceans home — zooplankton, phytoplankton, and algae as well as the bacteria that flourished in those warm shallow waters. When the organisms died, they floated to the ocean’s bottom and combined with the clay-like material that constituted the ocean and river beds of the era.

This mud, which is rich in organic matter, covers the dead organic matter, preventing it from decomposing. After millions of years, this mud layer is compressed and becomes a sedimentary rock. The organic material changes into the so-called organic shale.

If the shale is sufficiently deep, between 1 and 2.5 miles below the earth’s surface, it begins to get warmer and experiences more pressure. This pressure transforms the organic shale into oil shale, also called kerogen. At this stage, it gets a little bit complicated. If the temperatures are between 90 and 160 °C, the kerogen turns into natural gas and oil. If temperatures are above 160 °C, only graphite or natural gas is formed.

This temperature range is called the oil window. After escaping from the oil shale, the oil rises toward the water above and forms a reservoir. Prospectors look for this situation when searching for new regions to drill — reservoirs that can be safely tapped without causing any damage to the environment.

How is it Obtained?

When a prospector locates a sealed reservoir, they can drill into it and place pipes into the reservoir so as to draw the oil up to the surface where it can be sent to a refinery for processing. These deposits can be brought closer to the surface by geological changes such as earthquakes, thus making it easier for humans to access the oil.

How is it Used?

People might just think of oil as gasoline for their cars, but it is used in a range of other products as well. A chief component in petrochemical feedstocks is crude oil, which is used to manufacture plastics. In addition, crude oil is a major component in several different fuels, such as jet fuel, kerosene, and aviation gasoline.

It's even under the tires of vehicles — the roads and highways crisscrossing the landscape are created using road oil and asphalt in which petroleum is the primary component.

Is There Enough Oil to Last Forever?

If oil is continuously being formed by the pressure and heat of the earth's mantle, is there sufficient oil to last forever?

The short answer is no. All the accessible oil in the earth's crust is rapidly being used up by humans, and it will take millions of years for more to form. In the present situation, people may run out of oil sometime in the next century, which means that it is up to them to save the remaining oil. A good place to start is to use less gasoline, which has a lower energy content when compared to other types of fuel, such as heating oil, and also accounts for almost half of the oil usage.

Being a species, humans need to start using oil in a more responsible manner. The planet might be making more of it, but the world isn’t getting any smaller.