Oil fields

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. In this case the hydrocarbons are trapped and they accumulate. An accumulation of hydrocarbons, in a quantity that can be exploited economically is known as a field.
A trap consists of two elements: below, a reservoir rock that holds the petroleum and above, a cap rock that forms a barrier. Cap rocks are convex on the upper side and are impermeable, so that they prevent the hydrocarbons from escaping. On the contrary the reservoir rocks must be permeable and porous like sponges in order to enable the hydrocarbons to move within, and to make the extraction procedures easy. The size of a deposit depends on the amount of the original reserve – from the over 11 billion tons in the Ghawar deposit (Saudi Arabia) to a few hundred tons in the smaller fields.

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?...

  • 22 May 2016

    Green chemistry

    Chemistry accompanies man from that day long ago...

    10 January 2012

    Shale gas

    Unconventional gas: shale gas

    27 September 2012

    Over 7 billion people on Earth

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

  • 18 May 2011

    Artificial photosynthesis

    The history of science and technology is packed with discoveries and inventions inspired by nature...

    14 July 2021

    Italy’s renewable sources

    Renewable energy sources in Italy The Energy Services Operator (GSE) periodically publishes data and statistics on the renewable energy sources…

    10 September 2020

    A simple and ingenious invention

    There are objects so simple and ordinary that we forget their existence when we don't need them. Their presence is…

From the Multimedia section

  • energy

    Classification of reservoirs

    Look

    energy

    World oil reserves at 2018

    Look
  • energy

    Laying of a pipeline

    Look

    energy

    Pipeline under construction

    Look
  • energy

    Men at work

    Look

    energy

    Drilling of wells

    Look
  • energy

    Classification of reservoirs

    Look
  • energy

    World oil reserves at 2018

    Look
  • energy

    Laying of a pipeline

    Look

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...