How Does Oil Form?

Oil products power the modern world. You probably use gasoline every day to get around town, and the products you buy were almost certainly shipped to your location by diesel-powered vehicles. Without this fuel source, the world would be a very different place.

But how does oil, also called petroleum, form? Learn more about how this natural resource is created.

Oil begins as organic matter, meaning that it was once living plants and animals, though the animals were of the microscopic type. Millions of years ago, plants and algae thrived in bodies of water, taking in energy from the sun and storing it in their bodies, the same way that we store energy in our bodies when we eat food.

As each plant or microorganism died, it sank to the bottom of the body of water. Over the years, whole layers of these dead organisms piled up, with the bottom layers getting compacted by the pressure from all the weight on top of them. These layers of dead organic material also would get forced beneath layers of rock when tectonic plates shifted, burying the material deep within the earth.

As layers of rock and more organic matter accumulated over the decaying organisms, the pressure crushed them, which also made the temperature rise. Slowly, over millions of years, the heat and pressure changed the chemical composition of the material.

Proteins and other types of organic matter break down in these conditions, leaving only lipids, or fats, intact. These broken-down materials then reform into a substance called kerogen, which combines with the fats to make what will eventually be petroleum.

If the heat and pressure keep up, eventually even the kerogen will break down into simple hydrocarbon molecules. However, the kerogen layer has to be buried one to three miles deep, and the temperature needs to be 120 to 300 degrees Fahrenheit for this process to finish. Even with these conditions, it still takes millions of years for organic matter to become petroleum.

While the original organic matter was solid, oil is a liquid once fully formed. As such, it takes up more space than the solid organic matter, making the pressure on it even harder.

If the oil can move, it will—essentially, the pressure around the liquid squeezes it away. Often, if the rock above where the oil formed is permeable like sandstone, the oil will move upwards. Some oil will make it to the surface, where it will evaporate. However, some oil will run into a barrier that it can’t cross, like a stone structure that isn’t permeable.

When geologists look for new oil reserves, they often find them by searching for structures that could act as oil traps, like underground rock formations that look like an upside-down bowl. Geologists know that if the area was covered with water millions of years ago, there’s a possibility that oil could have formed, and if they check under these formations, they may find oil deposits trapped there.

Once oil has been found, oil companies can extract it by using enormous drilling machines. Petroleum is used for gasoline, but it’s also used to make many other products, including life jackets, tires, anesthetics and refrigerators. However, once the oil has been fully extracted from the oil reserve, the company must move on—since oil needs very specific conditions and millions of years to form, it won’t come back.

You need oil to get around, so depend on the best for your vehicle. Whether you’re a residential or commercial customer, rely on Biltman Oil for your fuel products. Call us today for more information.