Fundamentals of Petroleum Engineering: The Origin of Hydrocarbons

One of the best way to understand petroleum industry is by understanding the basic principles underlying behind the hydrocarbons.

Petroleum is found in the form of gas or liquid phases in porous rock structure and the word Petroleum itself is derived from the Latin words for rock (petra) and oleum (oil). 

Now that we know the origin of the word Petroleum, let's dive deeper...

Petroleum Hydrocarbon

Petroleum or Petroleum hydrocarbon is the mixture of organic components consisting of carbon and hydrogen. Petroleum hydrocarbons are available in the sub-surface of the Earth in the porous rock also known as sedimentary basins. 

In majority of the basins, oil coexist together with gas and water with methane gas at the cap. Methane is also available in large quantities from the coal bed and hydrates under the sea bed in the Arctic region. 

Generally, crude petroleum oil was formed from decaying plants, vegetables and dead animals that are converted to the oil by the action of high pressure and high temperature under the earth's surface, and by the action of the biological activities of micro-organisms. 

Organic matter are gradually buried and trapped under the surface of the earth and thus forming layer after layer in the earth's crust and rock.alert-success

Rocks that have these organic layers are called sedimentary rocks and decayed organic sediments that can be found several kilometers below the earth's surface will have a mass known as kerogen. This mass has a very high percent of organic-to-inorganic ratio favorable for the conversion to hydrocarbon.

The temperature of Earth increases with depth and at the kitchen depth which is in the range of 4-5 km from the surface of the earth, the kerogen is converted to hydrocarbon oil under very high pressure of rocks and soil. On the other hand, methane is formed thermogenically along with biogenic methane before the formation of the crude oil.

Migration of Oil and Gas

Next, migration of oil with gas occurs within the rock layers by the pressure gradient form high to low pressure zones. 

The formation of crude oil can be found in the sedimentary porous rock layers trapped under the hard and impervious igneous rock layers. Traps are usually anticline, domed or faulted areas covered by impermeable rock layers. Such an area that traps oil and gas is known as reservoir or basin. alert-info

Source rock, migration, and reservoir are the common terms used in the petroleum exploration and production. The area where oil and gas are stored is known as the formation and oil reserves are classified into three categories; proven, probable, and possible reserves. The commercially viable formation is also known as pay zone.

Understanding the basic principles of hydrocarbons will help to provide an idea on what kind of reservoir is commercially viable to be recovered. Thus, this will help petroleum engineers to determine the best method to recover the oil.

REFERENCES

Chaudhuri, U. R. (2011, July 11). Fundamentals of Petroleum and Petrochemical Engineering. Retrieved August 21, 2018 code-box