Oil is a fossil energy, just like coal or natural gas. Currently, fossil fuels represent 80% of the energy used in the world, whether for heating, transportation or lighting, both individually and on an industrial scale. Oil is often mentioned in the news, since our economy relies heavily on the price of the barrel. But what do we really know about oil? Where does oil come from? For many of us, the answer to this question is a mystery. This is why we suggest you learn a little more about the formation of oil, this black gold so hated but still so essential!
Where does oil come from?
Oil comes from a long and complex transformation process.
Sedimentation
Initially, it is a question of sediments. Or rather an accumulation of organic, marine and terrestrial sediments, the oldest of which are buried several hundred kilometers deep, in the bowels of the Earth. As a reminder, sediments are formed through the erosion of minerals and rocks. Microorganisms, such as plankton and phytoplankton, are added. Over time, a sedimentary layer forms.
The bedrock
Several tens of millions of years are then necessary for the transformation to take place. Little by little, the lower layer of sediment compacts into bedrock. It is then the organic matter trapped in the source rock which is at the origin of the formation of oil. The more they are present in quantity, the greater the formation of hydrocarbon.
Kerogen
The organic materials trapped in the cavities of the bedrock find themselves subjected to high geothermal pressures and temperatures, which will lead to the formation of kerogen. The birth of this intermediate compound occurs at a minimum depth of one kilometer under the ocean floor, where the temperature reaches 60°C and the pressure is around 250 bars. The pressure increases with depth, as does the temperature, which increases by approximately 3° per 100 meters. Anaerobic bacteria found in organic matter absorb nitrogen and oxygen. What then remains is a solid material, mainly made up of carbon and hydrogen, present in threads among the sediment strata, and constituting kerogen. The kerogen present at a depth of 2,000 to 3,000 meters mainly produces oil.
Oil exploitation
Human intervention is then necessary to make this crude oil usable. From its extraction to its complete transformation, oil goes through many stages.
Extraction
Oil extraction involves very sophisticated techniques, such as:
- The creation of wells, intended to mesh the site on which the reservoir is located;
- The installation of offshore platforms designed for offshore drilling;
- The injection of water or gas, intended to replace the extracted oil and thus maintain a constant pressure;
- The transportation of oil to the refinery by pipelines or by sea, stored on board huge tankers.
Refining
Our dependence on oil to this day remains preponderant, although we now know all the harms. It is also the keystone of our economic system, based on the price of oil. Black gold is essential in transport, as much for our mobility as for our supply. It is also used in the composition of plastic, and oil is thus indirectly used in the manufacture of many everyday items, such as furniture, toys, household appliances and even clothing and cosmetic products. Declining demand for oil will likely be the first sign that our needs, and indirectly our dependence, are diminishing.
The objective of refining is to transform crude oil into different petroleum products. During this process, crude oil is fed into a furnace and then sent to a distillation column. As the temperature increases, the different components form. This is how light products, such as liquefied petroleum gas or gasoline, intermediate products such as diesel, and heavy products such as fuel oil are formed. Refining also makes it possible to obtain kerosene or bitumen, as well as many other products.
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