Hydrocarbons Chemical compounds made up of carbon and hydrogen
They are mostly found in oil and gas. Hydrocarbons formed over many millions of years from organic materials: dead micro-organisms, plankton and algae that were deposited on the sea bed of ancient oceans and have slowly been covered by sediment. Cut off from the air supply, they were not able to fully decompose. Under high pressure and high temperatures bacteria then converted the sludge – and crude oil and natural gas formed.