What is it?

Oil is a fossil fuel, just like coal and natural gas. Such fuels derive from the remains 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.
More specifically, 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). Hydrocarbons make up a wide range of substances, since carbon can easily link to other carbon and hydrogen atoms to form open chains (linear or ramified), closed chains (ring, cyclic hydrocarbons like benzene have only one ring) or mixed chains (with open and ring structures).
There are thousands of hydrocarbons with different molecular structures and the same chemical composition. There are hydrocarbons with single bonds (alkanes or saturated hydrocarbons, such as methane), double bonds (alkenes such as propylene) or triple bonds (alkynes, such as acetylene). By means of a hot treatment in the absence of air (a process called cracking), the bond of heavier hydrocarbons can be broken to obtain lighter and more flexible molecules making up the infinite range of petrochemical products.

Special reports

  • 18 January 2016

    Ten years of oil demand

    Eni has recently published the 14th edition of the 2015 World Oil and Gas Review...

    23 October 2013

    Carbon Footprint

    A very special footprint...

    13 May 2013

    Small steps, great footprints

    Have you ever wondered how much space is taken up by an apple or a steak?...

  • 10 January 2012

    Shale gas

    Unconventional gas: shale gas

    15 September 2008

    Natural gas

    Natural gas has been the last fossil fuel to assert itself on a global scale...

    2 May 2006

    Enrico Mattei

    Enrico Mattei reminds us of a tenacious and brave man...

  • 6 September 2009

    Oil fields beneath the ice

    Con la graduale scomparsa del ghiaccio marino in seguito al...

    27 September 2012

    Over 7 billion people on Earth

    Demographers have estimated that on 31 October 2011 world population...

    22 May 2012

    Green chemistry

    Chemistry accompanies man from that day long ago...

  • 18 January 2016

    Ten years of oil demand

    Eni has recently published the 14th edition of the 2015 World Oil and Gas Review...

    23 October 2013

    Carbon Footprint

    A very special footprint...

  • 13 May 2013

    Small steps, great footprints

    Have you ever wondered how much space is taken up by an apple or a steak?...

    10 January 2012

    Shale gas

    Unconventional gas: shale gas

  • 15 September 2008

    Natural gas

    Natural gas has been the last fossil fuel to assert itself on a global scale...

    2 May 2006

    Enrico Mattei

    Enrico Mattei reminds us of a tenacious and brave man...

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Facts

  • Orimulsion

    In order to improve supply security, and therefore the diversification of sources to produce electric energy...

    Cracking operations

    At the end of the fractional distillation, long hydrocarbon molecules can be transformed into lighter molecules by means of more…

    Where does energy come from?

    Every day the Earth receives enough solar energy to satisfy the global energy need...

  • Electricity and electrons

    In all electric plants, excluding photovoltaic solar plants, mechanic energy is transformed into electric energy through the same basic procedure...

    Peat and peat-bogs

    The age of coal starts towards the mid 1600s, stimulated by the need for finding an alternative energy source to…

    Geographical distribution of energy

    Every day the Earth receives enough solar energy to satisfy the global energy need. Unfortunately we cannot exploit all this…

  • Some curiosities about methane hydrates

    The melting of the ice cells, not only brings about the release of methane gas, but it also produces another…

    Hydrogen from the sugar cane

    The Centro di Ricerca Interuniversitario per lo Sviluppo Sostenibile (CIRPS) carried out a study in Peru...

    Hydrogen from biomass

    Hydrogen is an energy carrier that allows to generate energy in an environmentally sustainable way...

  • 2 March 2011

    Orimulsion

    In order to improve supply security, and therefore the diversification of sources to produce electric energy...

    Cracking operations

    At the end of the fractional distillation, long hydrocarbon molecules can be transformed into lighter molecules by means of more…

  • Where does energy come from?

    Every day the Earth receives enough solar energy to satisfy the global energy need...

    Electricity and electrons

    In all electric plants, excluding photovoltaic solar plants, mechanic energy is transformed into electric energy through the same basic procedure...

  • Peat and peat-bogs

    The age of coal starts towards the mid 1600s, stimulated by the need for finding an alternative energy source to…

    Geographical distribution of energy

    Every day the Earth receives enough solar energy to satisfy the global energy need. Unfortunately we cannot exploit all this…

  • Orimulsion

    In order to improve supply security, and therefore the diversification of sources to produce electric energy...

  • Cracking operations

    At the end of the fractional distillation, long hydrocarbon molecules can be transformed into lighter molecules by means of more…

  • Where does energy come from?

    Every day the Earth receives enough solar energy to satisfy the global energy need...