The origins of oil

Crude oil is a result of the transformation of organic (animal and vegetal) debris from marine populations, under great pressure and in the absence of oxygen. This waste, mixed with sediments and gradually buried by new layers which are deposited, undergoes molecular changes under the combined effect of an increase in temperature and pressure. It thus becomes a liquid or a paste made up essentially of hydrocarbons, molecules made of hydrogen and carbon assembled in chains which vary in their degree of complexity. As well as hydrocarbons, variable proportions of sulphur, nitrogen, oxygen and traces of various metals are present.

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The word petroleum comes from the latin petra (rock) and oleum (oil) meaning ‘rock of oil’.

Every crude oil is a unique blend of thousands of hydrocarbons. Crude oils vary not only from one reservoir to another, but also within the same reservoir. Hydrocarbons are mainly liquids which are lighter than water at atmospheric pressures and temperatures typical for human life.

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The origins of oil

 

 

The simplest hydrocarbon.
Methane molecule: CH4

Over time, from the moment it is formed, oil begins to migrate towards the surface of the earth. On its way, it meets porous rocks, known as reservoir rocks, where it accumulates and forms oil reservoirs.

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The origins of oil
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