Hi all,

 I am basically working for oil Industry and hence just wanted to give some basics on formation of oil and how it gets collected under the surface.

 Oil and gas are hydrocarbons that were formed from the remains of plants and other organisms between layers of sediment around 300 million years ago. These liquid hydrocarbons gradually seeped through porous rock until they reached an impervious layer and became trapped,
forming an oil or gas field.

The plants and organisms after their death get de-composed due to hige pressure and temperature. They become crude oil in future.

1. Source Rocks - These contain organic material from plants or algae which are buried and cooked below the earth’s surface for millions of years
2. Reservoir - The oil or gas will flow until it collects in a reservoir rock, which has pores (holes) that acts like a sponge
3. Trap - To trap the oil and gas the reservoir rock needs to have an impermeable rock, called a ‘caprock’ above it and around it.   This caprock will not allow oil or gas to travel through it. See a sample Trap below.

 Hole is drilled and then the oil is taken which is still a bigger process in Oil Industry. So, if the oil is taken out from the surface can we directly use it as it is ? No way!!!!!  That's when refineries come into picture. The components are extracted in refineries and the fuel which we use is transported to the respective locations. That's how we get our petrol in petrol pumps. The rest of the components are used for other purposes like asphalt can be used for road construction.

We also have oil beneath the oceans. Obviously we have organisms living in the sea which also die and hence will also get de-composed under high temperature and pressure to become oil. Structures called 'Rigs' are installed in the sea as well as in the land to retrieve oil to the surface. There are companies like Transocean which provide equipments like rigs for taking oil out. They work in sync with the oil companies to get the oil to the surface. Each area in Oil industry needs a specialization to be worked upon.  

It is a non-renewable source of energy and having a look at all the hard work that people put in to bring it for usage lets use it wisely !