At present oil is the most important source of energy and for some applications it is irreplaceable, but till when will it be able to satisfy the growing demand of energy? The day will come when the production of oil shall reach a peak, after which it shall inexorably decrease with a consequent increase in prices. The distribution of the main oil basins around the world is not uniform, however it is not even random. In fact it depends on the geological conditions that are necessary for the formation of large deposits and the difficulty encountered to explore and search for oil in isolated scarcely known areas, as for example areas characterized by environmental conditions that are particularly severe (vast areas in Siberia, the rain forest area in South America and deep offshore areas). The geological history of our country is very complex and has given the peninsula a complicated and not very “tranquil” structural and sedimentary order. This has not favoured the formation of large extensive oil basins but has created local situations that are favourable for the formation of a number of oil provinces that are quite important, even though their extension is not great.
Oil is a fossil fuel, just like coal and natural gas. Such fuels derive from the rests of plants and animals which died hundreds of million years ago, when mankind had not yet appeared on Earth. Those plants and animals, as it happens today, have accumulated the energy coming from the Sun and, after their death, have remained buried for millions of years until they have turned into oil and coal. Prehistoric animals and plants today return the solar energy they accumulated in the past as heat and electric energy. Great part of the energy we use today comes from fossil fuels, especially oil. However, it is a non-renewable energy source which is bound to depletion sooner or later.
Oil is a natural mixture of liquid hydrocarbons and other substances of fossil origin contained in sedimentary rocks and associated to smaller quantities of gaseous (natural gas) and solid (bitumen) hydrocarbons.
All the molecules of the existing hydrocarbons include two types of atoms only: carbon and hydrogen atoms. According to the quantity of carbon atoms included in the molecule, hydrocarbons can be in gaseous (up to 4 atoms), liquid (from 5 to 16 atoms) or solid state (over 16 atoms).
Origins of oil
The most favourable environment for the formation of new hydrocarbons includes areas marked by a limited circulation at the bottom and constant accumulation of debris by rivers (ancient seas or lakes), as well as sedimentary basins where the Earth’s crust is lowered gradually or quickly following natural geological processes.
What is for?
Many products can be obtained from oil, ranging from some of the most common fuels (petrol, gas-oil and other by-products of oil) to many of the plastic materials used by mankind. The simple hydrocarbons that compose oil are, in fact, the main raw materials needed to produce plastic materials with specific features: resilience, plasticity, hardness, flexibility, biodegradability, sturdiness, adherence, water-proof characteristics, malleability, etc.
Once it has formed, oil is squeezed out of the mother rock (compressed by the layers lying on top) and it first moves through the microfractures (primary migration) and then into the small channels in the permeable adjacent rocks (secondary migration). In some cases hydrocarbons reach the earth’s surface and disperse. In others, their migration is blocked by impermeable rocks.
A bit of history
For thousands of years, hunting and collecting vegetables were the main resources of mankind. Human beings could only consume energy, since they were unable to produce it.
Approximately 7000 years ago, mankind discovered agriculture and eventually learned how to produce energy: it was food and muscle energy (produced by human beings and animals helping them), wind and water power (wind and water mills).
When analyzing the list of major producers of hydrocarbons in the world, the differences in the various countries are immediately highlighted. However, it must be borne in mind that production is influenced by a vast series of factors, among which the potential of the reserves is only one of the main ones; technical factors can make extraction more or less difficult even in the presence of large reserves and economic factors may lead to an increase in the production depending on the demand. For example, the production of the USA is very high compared to the estimated reserves, while in the Middle East, which has enormous reserves, the production/reserves ratio is very low. Therefore, it is important not to confuse production with the size of the reserves. The largest producers are not necessarily the countries with the largest reserves. 50% of the oil reserves is localized in the Middle East. Most of the oil reserves are in Venezuela, accounting for 17.4%; the countries that follow are Saudi Arabia, Iran, Canada, Iraq, Russia, United Arab Emirates, Kuwait, Libya and United States.
Oil fields in the world
The distribution of the principal oil fields in the world is not uniform, but neither is it random, and it depends on particular geological conditions that are necessary for the formation of large reserves and the difficulty of exploring and researching oil in isolated areas that are not well known, such as areas characterized by particularly severe environmental conditions (the vast areas of Siberia, the areas of the rain forest in South America and the deep offshore areas). The more important oil fields have geological characteristics that are very different from each other, but they have some common elements.
Hydrocarbons in Italy
The geology of our country (Italy) is very complex and the peninsula consequently has a complicated sedimentary and structural order, that is not very calm. This has not favoured the formation of large and extensive oil fields, but has created local situations that are favourable for the formation of numerous oil provinces that are reasonably important, even though their extension is not great.
Our country can, from a tectonic point of view, be subdivided into 4 “districts”. These are all tied to the presence of the mountain ranges of the Alps and Apennines.
The reserves of that energy source are not distributed in a uniform way in the world; on the contrary, they concentrate in some countries: the Middle East alone has 50%, South and Central America has 19% (Venezuela has 17.4% of the world oil reserves), North America has 12%, Russia and Central Asia has 7%, Africa has 8%, Asia-Pacific has 3% and Europe only 1% (data referring to 2021).