How are oil and gas formed?

Oil and gas are important fossil fuels formed from the decomposition and pressurisation of algae, plankton and other organisms.

This process forms hydrocarbons. These are compounds consisting entirely of hydrogen and carbon that form powerful combustible fuels.

When algae, plankton and other organisms die, they sink to the bottom of the sea and lakes, as well as rivers that wash them into seas and lakes.

These low-lying areas are parts of “sedimentary basins” that are filled up over tens of millions of years by fragmented material that hardens into rock layers – including sandstones, shales and coal seams.

Organic material (mostly plankton and algae) in these rock layers breaks down to hydrocarbons (oil and gas) that are trapped in the rocks.