PETROLEUM NOTES

What is petroleum?

Petroleum also known as crude oil is a fossil fuel comprising a complex mixture of hydrocarbons. Its composition varies, depending on where in the world it is found, it generally contains alkanes, cycoalkanes and aromatic hydrocarbons.

Crude oil is non-renewable (finite) and it cannot be replaced. It was formed:

  • From the sea, the sea contains many tiny animals and plants called plankton, they get their energy to live and multiply from sunlight. When they die they sink to the bottom of the sea. Those that died millions of years ago, form oil and gas which are the main sources of fuel.

  • The Dead Sea creatures were buried by sand and mud at the bottom of the sea. It is thought the sun's energy was stored in the bodies of the dead creatures and plants. The dead bodies started to decay.

  • Over millions of years the dead animals and plants were buried deeper and deeper. The squashed creatures turned into oil and gas. The pressure and temperature deep underground turned the chemicals from the decaying animals and plants into crude oil and gas.

How do we get the crude oil out of the ground?

  • Oil and gas can get trapped in pockets underground such as where the rocks are folded into an umbrella shape.   Oil and gas can move through the porous rocks (rocks with gaps between the grains). The oil and gas move upwards from the source rock where they were formed. When they met a layer of cap rock (a rock with no spaces between the grains) the oil and gas are trapped.
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  • A well is drilled so that the crude oil and other liquids travel up the bore hole. When it comes to the surface the crude oil has to be moved closer to where it is needed.

Finding oil and gas trapped deep         underground and drilling a well is very         complicated and expensive. It costs         millions of pound to drill a well and only a few are successful. The liquids found underground can be a complicated mixture of water, crude oil and gas. The crude oil and gas need to be separated before they can ...

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