Petroleum is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds. The word petroleum literally means rock oil. It is best known for being the substance from which a number of industrial products and fuels are made, such as gasoline, kerosene, diesel, asphalt, and lubricating oils.
There are two theories that support the origin of petroleum. First, the biogenic theory implies that petroleum made by the fossils of animals and plants from thousands years ago. Many geologists believe that petroleum is created by the remains of plants and animals that slowly decay under layers of rock. The abiogenic theory implies that carbon was present before human life on Earth. The discovery of methane supports the abiogenic theory strongly. 
biogenic theory supports that petroleum was made by the rotted fossils of animals and plants from the prehistoric age. Then, fossils have lay under layers, and mixed with dirt, which makes the fossil hardened and get stiff with hydrocarbons. The consequence of this process, fossils get harden by the high pressure and heat, and fossils get stiff with hydrocarbon, produce oil and gas. In addition, the pressure and heat can change the mixture of chemical compounds into three different types of petroleum. If the pressure and temperature were small, then the petroleum would change into a black substance, also known as asphalt. If the pressure and temperature were average, then the petroleum would change into a natural state of oil, also known as crude oil. If the pressure and temperature were large, then the petroleum would make a colorless gas, methane.
Abiogenic theory, which is contrary to biogenic theory, purports that petroleum was formed from carbon sources other than lifeforms. A few scientists, such as Thomas Gold, have provided some support for the theory, but most question the validity of the theory.
In ancient times, before human used petroleum in automobiles, human used petroleum in plastering walls and framework. For example, Native Americans used petroleum in medicine, also known as Seneca oil. Its ability and the effect of the medicine was good; therefore European people bought it. The first distribution of petroleum was began in 1815, and during 19th century, the production and manufacturing of petroleum was started by E. L. Drake. He was the American oil founder. After machines and automobile invented, the petroleum could be used broadly. In these days, oil and gas are using in almost everything in the world, because petroleum gives energy to materials to make power. There are three types of oil in the world, asphalt, crude, and methane. Typically, crude oil is the main type of oil that we use in ordinary times. Because, crude oil is blended with petroleum solution and different types of gas. The oil can be divided into three levels; lower value, medium value and higher value by products' refinement. Moreover, many people think that the oil industry began in nineteenth century, but it is wrong. Because, in fifteenth century, King Edward IV started to drill oil and gases, then, he made a standard measurement of oil. For example, he set 42 gallons as 1 barrel in about 500 years ago, and we still use that measurement.
People, in these days, uses petroleum in everything, such as, automobiles can work by petroleum, houses need petroleum to make an energy for light and electricity, and even in toys, because, petroleum is needed to create plastic. Not only gas is the product of petroleum, asphalt is also the product of petroleum. People use asphalt in road (asphalt concrete), and tires. The main uses of petroleum is fuel and oils that make substance shinny. There are about five different types of fuels from petroleum. For example, when people go to gas station, then they could see gasoline and diesel, those are the two main fuels that people usually use. Not only them, there are fuel oils, kerosene, and LPG are the other examples of fuels. Other products of petroleum are alkenes, lubricants, wax, sulfur, tar, asphalt, and paraffin wax. Alkene is the main component to make plastics. Lubricant is a substance that goes on the exterior of the machine to make smooth. Wax is a shiny substance that made out of oil and it usually use to make candles and container of frozen food. Bulk tar is a massive black substance that use in making roads. Asphalt is working similar to bulk tar, because it is also black substance that use in making tires and asphalt concrete. Paraffin wax, also known as coal oil, use in making candle, cloth, film, paint, furniture, and artificial manure. 
Before extracting petroleum, gas extractors should make a plan that shows where is the best place to start, and how are they going to extract. For example, they should see the geographic map before they start, because, they should know the position of water. After, they done with plans, then they should start the construction with drill down the ground. Usually, oil is extracted through petroleum wells, which is a deep hole that help oil to get out of the ground. For extracting oil, need many machines, are needed not only drills, such as gravimeter, magnetometer, and seismograph. The gravimeter is a machine that can measure the force of gravity in special region. The magnetometer is a machine that can measure the force and course of the magnetic line. The seismograph is a machine that can measure the force or power of the terrestrial tremor.  However, while the extraction, people have to be careful, because, when the pressure to the oil storing pond is adequate, then the oil will shoot up to the ground. Then, they connect the valve with the storage, to send oil from the underground to the oil storage. 
Petroleum can be separated by its consistency, which means, if compound includes carbon and hydrogen, then it is hydrocarbon. If compound include oxygen and metals, then it is non hydrocarbon. Refining of petroleum can make about six different types of oil, such as gasoline, diesel, benzene, naphtha, kerosene, and two different heating oils by its weight. Heating oil is including methane, ethane, butane and propane, because these are the lightest gases, which means the boiling points are low. During the refining system of petroleum, the degree of strength or intensity can make the color lighter and darker. Gasoline is the lightest product of its refinement and asphalt is the darkest product of its refinement. Gasoline is made by high pressure and heat to split up the massive molecules into tiny molecules. However, asphalt, the darkest outcome of the refinement of petroleum, would need small pressure with small heat to make darker color. Consequently, this is why gasoline is more expensive than asphalt or diesel.  
After the industry and development petroleum began, the environment is getting worse and worse than before. The oil makes serious effect on the community and environment with extreme construction, which makes the earthquake, drilling and boring, and air pollution. Many scientists, environmental engineers and geologists indicate that extraction of petroleum makes a trouble within the nautical environment, such as drilling could kill all living things in the sea, and sinking of the oil by the accident can make destruction of the plants and animals living area.  Because, oil includes a lot of harmful components, such as tar, could attack no matter what it is and how big it is.  Not only, drilling and oil spills, combustion of oil would cause the environmental problem. Because, after it burned it takes oxygen out and puts carbon dioxide into the world, and it caused the global warming. Therefore, the glacier and icebound river are going to be melted and the percentage of oxygen will be lower than before. Consequently, all living things, even the human, going to destroy in a moment.  However, we can stop the global warming by practicing in little things. For example, use a bike for the vehicle, but if it is a long distance, then use bus, car pool, or car with hybrids that could lower the oil combustion. Instead of using fuels, people should use renewable energies, such as solar heat, water-power or hydraulic power, wind velocity, and nuclear energy.
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