How were oil fields formed?

Crude oil is a liquid mineral which is primarily a mixture of natural liquid, gaseous and solid hydrocarbons. In addition, it contains small admixtures of oxygen, nitrogen, sulfur and inorganic pollutants. Its properties are of great importance to the world economy. First of all, because it is an important raw material for the chemical industry, but above all for the energy industry. How exactly is it made? What is necessary in the process of its creation? Please see the article below for information.

How is crude oil produced?

Crude oil is produced as a result of thermal and biochemical transformations of organic matter, which comes from both animal and plant remains. Therefore, an appropriate mass of organic material is necessary to start the process. Its accumulation takes place when the accumulation of sediments prevails over erosive processes. The best environments for this type of process are seas and lakes. The greatest amount of organic sediments is deposited in reservoirs, which are characterized by high eutrophication of bottom sediments and primary production, but low environmental hydrodynamics and / or water stratification. A large supply of nutrients to the photic zone causes an acceleration of primary production, which results in flowering of phytoplankton. First of all, marine algae, which are the most important supplier of marine organic matter.

In the next stage, when a supply of phytodetritus reaches the bottom of the water reservoirs, the amount of oxygen in its upper and lower parts is reduced. This is the effect of decomposing organic matter in which oxygen plays an important role. Deposition is also taking place at the same time, especially of clay and dust resources. This process results in the detachment of the previously deposited organic layer, which is enriched with the bacteria active there. Thus, matter loses contact with external factors, especially the access of oxygen is limited. This process is called anoxia, which results in anaerobic decomposition of the mass. The presence of anaerobic bacteria and an increase in redox fronts (the level of sulphate and nitrate reduction) result in the production of hydrogen sulphide in the higher parts of the sludge. His presence is not insignificant.It inhibits the deep activity of the drilling fauna, i.e. the penetration of oxygen into the sediment in the bioturbation process. The effect of all these activities, along with the continued sedimentation of clay minerals, is complete isolation of the organic layer from the oxygenated zone. Thus, remineralization processes take place only under anaerobic conditions.

What is the diagenesis stage?

In the process of decomposition of organic materials, aerobic and anaerobic changes take place, which initiate the second stage of oil formation, i.e. diagenesis. Complete oxygen depletion is the period when a new stage in the formation of this deposit begins. Eating anaerobic bacteria initiate chemical reactions that result in new chemicals. If certain conditions are met, they will later become crude oil. A side effect of their processing is, for example, biomethane.

Due to the complexity of the process, the large mass of dead organic material as well as the anaerobic bacteria operating in it is not a sufficient factor. Both components necessary for the production of crude oil must be deprived of oxygen and other environmental factors. To achieve this goal, the accumulated layers of dead animal and plant organisms are covered with a solid layer of silt and clay. What is the task of this layer? The accumulated sediment shows mainly insulating properties. At the same time, the minerals contained in it act as a catalyst for chemical reactions that enable the processes of producing crude oil.

The importance of temperature in the process of creating crude oil

The oily mixture of dead organisms undergoes changes in the anaerobic process and then is isolated with layers of silt and loam. As a result, valuable oil deposits may be created in the future. In subsequent years, decades and hundreds of years, successive layers of silt and dust are deposited, in which various chemical reactions take place. As time passes, matter becomes heavier and heavier, so it sinks deeper into the Earth. This in turn causes the pressure to rise due to the pressure of the weight of the accumulated layers. As the sludge settles down and increases pressure, the temperature also rises. One kilometer below the Earth’s surface it is 30 ºC, which is still not a sufficient result. It is only at a depth of 2 kilometers that the desired changes begin to take place. There the temperature is 60 ºC,which are ideal conditions for further transformations of the accumulated organic matter. The mass undergoes further chemical changes which inevitably lead to the formation of crude oil.

In summary, the process of producing crude oil requires certain environmental conditions to be met. It runs in the aquatic environment under the influence of anaerobic bacteria in organic matter.