In the old days, oil was usually extracted where it was in the form of natural sources, coming to the surface through cracks and faults in rocks. However, by the middle of the 19th century, the question arose before the industrialists: how to look for oil, which is located outside the places of direct exposure to the surface?
In search of oil deposits
Initially, land was the space for prospecting and exploration of oil fields. It turned out that hydrocarbons are contained where sedimentary rocks have accumulated for a long time. Therefore, thick layers of the sedimentary cover began to be considered the most important feature in the search for oil. However, these places are rich in oil only where they are formed in the form of folds and are torn apart by movements of the earth's crust. Dome-shaped and swell-like faults and bends of formations turned out to be the most favorable for oil prospecting.
The researchers subsequently found that oil prefers porous rocks that are permeable.
Search stage
Hunting underground oil deposits can be very expensive. To reduce the cost of search work, they are carried out in two stages.
The first stage includes the direct search for oil. To begin with, experts are looking for the so-called "traps", that is, identify the most promising areas. To do this, when searching from the surface of the earth, special devices are used, they listen to the thickness of the planet's layers with seismic waves. This stage includes geological and geophysical studies, during which wells are drilled - reference, exploration and parametric ones.
Based on the data obtained, maps are compiled and sections of the earth's crust are drawn. Formation bends appear on these diagrams. When, as a result of the preliminary analysis, something similar to a hydrocarbon "trap" appears, the specialists proceed to the next stage - the exploration of potential deposits.
Exploration of oil fields
The second stage of oil prospecting activities also involves drilling. But now the purpose of the survey is to find out whether there is oil at a given depth. And if there is oil, then what are its reserves. When it is established with more or less accuracy what the oil reserves in a given area are, calculations of the field's profitability are carried out. If the calculations show that the production of hydrocarbons here is economically profitable, they proceed to the direct development of the field.
When drilling rigs appeared, the circle of countries involved in oil production expanded greatly. Now oil is being produced all over the world - with the exception of Antarctica. Significant volumes of hydrocarbons have been rising since the days of the seas.
It has been found that oil is distributed very unevenly around the planet. Of the three tens of thousands of known deposits, only one hundredth contains approximately 75% of the world's valuable hydrocarbon reserves.
Most of the oil is explored in the Near and Middle East, in Kazakhstan and Western Siberia, in North Africa. There is also oil in the Americas.
