Petroleum formation and extraction
Petroleum formation and extraction
Car fuel, a plastic bag, aspirin, and bubble gum — what do they have in common? They are all modern products made from something ancient — petroleum! Petroleum, also known as crude oil, is a complex mixture made up mostly of hydrocarbons. Petroleum’s many uses make it a very valuable resource. Not only is it used to make fuels, plastics, and other products, but it also serves as one of the world’s main energy sources.
Where does this precious substance come from? To find out, we need to go back in time hundreds of millions of years… It all starts in the warm, shallow ocean, where tiny organisms called plankton float. Dead plankton sink to the ocean floor. There, they mix with sand and mud forming a sediment. Over time, more and more layers of sediment pile up.
The weight of the new layers of sediment and the ocean water above exerts enormous pressure on the buried material. This, in turn, creates heat. Over millions of years, pressure and heat gradually turn these layers of sediment into rock, and turn the organic matter buried in them into petroleum and natural gas. The petroleum gets trapped under layers of non-porous, impermeable rock, such as marble or granite. It forms vast underground reservoirs, where those ancient oceans used to be millions of years ago.
As time passes, land masses shift and the shape of the Earth’s surface changes. This causes petroleum to rise up to the surface in some places. But most of the time, petroleum is trapped underground or under the ocean floor. So, how do you find petroleum and extract it? Finding petroleum reservoirs is a job for geologists and geophysicists.
They study terrain, surface rock, and soil types to predict areas where there might be a petroleum reservoir. They also use modern technology to measure changes in Earth’s gravitational or magnetic field. These might indicate a reservoir underground. Another common method is seismology, which uses an artificial shock wave directed at the layers of rock. As the shock wave travels through the layers of rock, it changes speed and gets reflected differently, depending on the type of rock it passes through.
A special device reads the signal, which scientists can use to determine whether there is petroleum between the layers. What happens when petroleum is found? First, scientists assess how much petroleum there is, how deep it is buried, and how difficult it would be to extract. It must also be decided what impact extraction will have on the environment, and who has the right to extract the oil. If everything goes well and all issues are resolved, a company can start extracting the petroleum.
This process is oil drilling. On land, petroleum is drilled using machinery known as an oil rig. First, a rotating drill bit powered by an engine cuts into the rock. This drills an oil well. Then pumps are used to bring the oil up to the surface.
Drilling oil under the ocean floor uses similar techniques, but it’s more complicated and expensive. A large, sturdy structure called an oil platform must be built first. Drilling and pumping equipment is installed there. The oil platform is used to store oil as it is extracted. It also houses people working on the drilling project.
Since oil drilling is a very costly operation, when a reservoir is found, it’s fully exploited. The operation goes on 24 hours a day for as long as extraction is possible. This can be several decades! How does all that petroleum become a source of energy or get turned into other products? That's a story for next time!