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Oil and Gas

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Almost all oil and natural gas are found deep underground in tiny holes in rocks. Millions of years ago a sea covered much of what is now dry land. In prehistoric times, tiny plants and animals lived in the sea. When these creatures died, they sank to the bottom of the sea, and got buried in layers of mud and sand. As the ages passed, this organic material sank deeper and deeper. The earth's crust changed its shape, and put intense pressure and heat on what was once only plants and tiny animals. Heat from the earth's interior and the weight of the overlying rocks gradually changed the energy-containing substances in the accumulated plants into hydrocarbon liquids and gases. As millions of years passed, these deposits turned into chemicals that are now called ‘hydrocarbons’.

Hydrocarbons are simple molecules made up of carbon and hydrogen atoms joined together in chains or in rings. These molecules, being light and mobile, migrated upwards through the rocks but eventually became trapped beneath impermeable rock structures in the earth's crust. That is where oil and natural gas come from. Some were created millions of years ago, some were created thousands of years ago, and some are being created right now!

Much of the oil and gas production now comes from underneath the sea-bed. As the technology for extraction continues to advance, production becomes possible from deeper and deeper waters. But the supplies are limited. Every drop of oil burnt adds to the monumental environment problems already created by pumping gases like carbon dioxide into the atmosphere. Many scientists worry that this continual release of carbon dioxide is an important cause of global warming.

Natural gas is usually found underground near an oil source. It is a mixture of light hydrocarbons including methane, ethane, propane, butane, and pentane. Other compounds found in natural gas include carbon dioxide, helium, hydrogen sulphide, and nitrogen. It is found around the world, but the largest reserves are in the former Soviet Union and the Middle East. This gas is lighter than air and is highly flammable, made up mainly of a gas called methane. Methane is a simple chemical compound that is made up of carbon and hydrogen atoms. Natural gas usually has no odour and cannot be seen. Before it is sent to the pipelines and storage tanks, it is mixed with a chemical that gives it a strong odour, almost like rotten eggs. The odour makes it easy to detect a leak.

Natural gas is the cleanest burning fossil fuel. When it is burned, it gives off less carbon dioxide than oil or coal, virtually no sulphur dioxide, and only small amounts of nitrous oxides. Natural gas is mostly composed of methane and other light hydrocarbons. Both the carbon and the hydrogen in methane combine with oxygen when natural gas is burned, giving off heat. Coal and oil contain proportionally more carbon than natural gas, therefore giving off more carbon dioxide per unit of energy produced. Natural gas gives off 50% of the carbon dioxide released by coal and 25% less carbon dioxide than oil, for the same amount of energy produced. Carbon dioxide is the most important greenhouse gas contributing to global warming.

To find oil and natural gas, companies drill through the earth to the deposits deep below the surface. The oil and natural gas are then pumped from below the ground by oil rigs. They then usually travel through pipelines.

At oil refineries, crude oil is split into various types of products by heating the thick black oil. The products include gasoline, diesel fuel, aviation fuel, home heating oil, oil for ships, and oil to burn in power plants to make electricity. Oil is used for transportation—cars, airplanes, trucks, buses, and motorcycles.

Oil is stored in large tanks until it is sent to various places to be used. Oil is also made into many different products—fertilizers for farms, clothes, toothbrush, plastic bottle, and plastic pen. There are thousands of other products that come from oil. Almost all plastic comes originally from oil. Oil is transported in huge pipelines and tanker ships to places where it is made into other products.

The origin of the oil industry in India can be traced back to the last part of the 19th century when petroleum was discovered in Digboi in north-east India. Thereafter large numbers of oil fields have been discovered both inland and off-shore. This has led to the setting up of refineries to process the oil and gas for use in various sectors.

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