Describe the process of formation of petroleum .

Explanation

Petroleum is a dark oily liquid. It is a mixture of various fractions. Petroleum was formed from organisms living in the sea. As these organisms died their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure and action of microorganisms, transformed the dead organisms into petroleum and natural gases. The layer containing petroleum and natural gas is above that of water. It is because oil and gas are lighter than water and do not mix with it.