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How Coal and Petroleum are Formed?

The branch of geology that holds the greatest economic importance worldwide is the study of fossil fuels. Do you know that the petroleum products that we use today were formed over millions of years from the remnants of dead organisms? In this blog, our science assignment help experts have discussed the scientific processes involved in the formation of coal and petroleum. Take a look:

Coal-forming environments

Areas that had once thick vegetation is thought to be the best site for coal formation. Over time, the vegetation might get broken down by flood, earthquake, and grazing animals. And, microbial decomposition of plants allowed the formation of peat(a brown material which consists partly decomposed vegetable matter). The waterlogged areas are the primary site for the formation of thick layers of peat called mires. Swamp environments and flowing water produce the best-quality coal as it brings in clay, silt and sand particles. However, if the water is saline, it will lead to the formation of sulphides (typically iron pyrite) in the coal. This type of coal is considered to be of low-quality as sulphur dioxide is emitted when it is burnt. Sulphur content and ash are the two primary factors that are considered when assessing the quality of coals, as the lower they are, the higher the grade. Coals that originate as peat deposits are known as humic coals, but not all coals have the same origin. Sapropelic coals are deposits of aquatic algae that might accumulate in the bottoms of lakes. Although they are less common, they are significant because they can be source rocks for petroleum oils.

Formation of coal from peat

Now you know that the initial stage of coal formation is the breakdown of plant tissues to form peat. But peat is a low calorific fuel, and it becomes coal only when it is buried under hundreds of metres of other sediments and subjected to high temperature. As the peat faces high temperature, it loses its water content and releases volatile compounds such as methane and carbon dioxide. As the oxygen, hydrogen, and nitrogen compounds are lost through evaporation, the proportion of carbon increases from 60% to 90%, and hence the calorific value of the coal increases. The higher the carbon content of the coal, the better its calorific value is.

Formation of oil and gas

Petroleum oil and gas are principally made up of hydrocarbons(compounds of carbon and hydrogen). These compounds originated from organic matters such as plants and animals that get accumulated within sedimentary rocks. The process involved in the formation of natural gases and oils is called hydrocarbon maturation which takes place in a series of stages. These chemical procedures involved in this step eliminate oxygen from kerogen(the solid part of organic compounds that is insoluble in organic solvents). There are three types of kerogen:

  1. Type 1- They are formed from amorphous organic matter and planktonic algae.
  2. Type 2- They are derived from mixed marine and continental organic materials.
  3. Type 3- They originates from terrestrial woody matter.

At a very high temperature( exceeding 400° C) and at a depth of just 1000 metres below the earth’s surface, kerogen gets transformed into liquid petroleum. When the temperature reaches 1500°C, the liquid petroleum changes into gas. Generation of oil by the organic maturation of kerogen takes millions of years. At higher temperature and burial depths only methane is produced, a stage known as metagenesis. Besides temperature, another factor that affects the formation of natural oil and gases is the type kerogen. Type 1 kerogen is the best for the formation of petroleum oil. And, type 3 kerogen is a good source of natural gases formation. The next important factor is that the organic matter must be buried at the right depth as if it lies too deep, then only methane gas will be released.

Hope now you are well aware of the process involved in the formation of coal, petroleum, and natural gases. Geologists study the rocks and analyse the depositional history of the area to determine whether the land is suitable for the exploration of petroleum reserves.

If you desire to learn more about the topic, then refer to good books and journals on petroleum science and engineering. Visiting to a mining site will also turn to be useful. However, if loads of assignments are impending you from the same, then seek help from the experts of Instant Assignment Help Australia. We have set a benchmark as the best online assignment help provider in Australia.

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