The word petroleum is a Latin word and was used to describe petroleum crude oil by the Germans. Petroleum or petroleum crude oil is a dark oily liquid found under the earths crust. It is a naturally occurring complex mixture of large number of various hydrocarbons and hence, has no specific chemical formula. So it's very difficult to predict pin pointedly the characteristics of petroleum crude found at certain place. Hence the characteristics of petroleum crude are classified based on certain wide nature of criteria such as, wax content, sulphur content etc which more or less remains stable for a particular basket. Crude oil is formed from the biological decay of the organic materials over the ages under the earth.
There are numerous usages of petroleum in our modern world. But there are number of stages through which the crude oil passes, to reach the end users i.e. you and me. The first stage is exploration and extraction. Exploration is the task of geologists. Nowadays crude exploration is done by some sophisticated ways such as seismology, air wave, explosives etc. More than one method is used to firmly verify the existence of petroleum crude below certain stretch of ground. After exploration, in order to extract, the soil has to be dug up. There are some scientific methods available, which has to be followed in order to safely and efficiently execute the job of extraction.
The extracted crude oil has a very limited use as crude oil and hence, after extraction, the crude oil is sent to the refinery where it's refined and segregated into various refined forms. It's already noted above that crude oil is a mixture of various types of hydrocarbon; hence different hydrocarbon forms a different product. In some of the products, more than a single type of hydrocarbon may also be present.
The process used for segregation of different hydrocarbon is fractional ditillation. In this process, the crude is boiled and heated to evaporation. Since there are different hydrocarbons, hence evaporation points of those will also be different. Light hydrocarbons will be evaporated first and gradually heavy hydrocarbons will be evaporated with increase in temperature. The evaporated substances are allowed to flow upwards in a column. This column is known as distillation column. While moving upwards the temperature of the substance decreases and at a certain point it condenses to liquid. At that point it is collected from the column sidewise. While extraction of crude oil, some gaseous and semi-gaseous substances are also found. These components along with the lightest liquid components are evaporated first. These are collected at the top of the distillation column. As we go down the distillation column, the molecular weight of the finished product obtained, increases. In this way at different level/ height of the distillation column we obtain different finished products.
At the top we obtain the lightest products such as natural Gas and LPG. As we go down the distillation column, products such as petrol, naphtha, kerosene, diesel, fuel oil, bitumen etc. are obtained. So, it's obvious that these kind of finished products are a better use of crude. These products are then evacuated from the refinery and reach the customers.
Petroleum crude extraction and refining is a very risky and costly business. Petroleum and petroleum products are considered to be having explosive characteristics due to their highly inflammable behavior. While extraction, refining, storing, and distribution high safety measures are to be followed to avoid any disaster.
Even if it is a very risky and costly business, human civilization is committed to deal with petroleum and petroleum products. It's because human civilization, up to certain extent, is dependent on petroleum. Look at its usage. Starting from the petroleum jelly or the lipstick at the dressing table, up till the gasoline or diesel used to drive vehicles is produced from petroleum. Petroleum products are not only fulfilling individual human need but also fulfilling industrial needs. It is an excellent source of energy and hence human civilization is using it from last many decades.
Although, petroleum is a very useful resource, use of most of it causes carbon emission to the environment and hence during the last few years an awareness throughout the world is growing to stop use of combustible petroleum product as a source of energy. Use of alternate energy source such as, solar, wind, nuclear etc. are being thought on and are being practically tested and implemented to certain extent. Petroleum is being used so widely that it's not so easy to completely stop the use of it. Hope, in future some planning for healthy utilization of resource having environment friendly aspects will come up.