Petroleum Accumulation: Conditions, Distribution and Origin
Petroleum is an essential resource in modern society, and has been the backbone of the global economy for centuries. Petroleum has its origins in prehistoric organisms that lived in the ocean depths and were buried in thick layers of sediment. Over time and with geological pressure, these organisms were transformed into hydrocarbon molecules, which are major components of petroleum. As a result, petroleum accumulates when certain conditions are met, and its distribution varies greatly around the world.
Petroleum is formed by the breakdown of ancient organic matter and is composed of up to ninety-four different hydrocarbons broken down into condensates (gases) and other liquid hydrocarbons called crude oil. Petroleum is expected to form after millions of years of burial, high temperature, and pressure, which convert the organic matter. This process is described as maturation or cooking of organic material in features known as source rocks.
For petroleum to accumulate in a region, there must be an uptake of organic matter, a source rock, and a trap. Organic matter must be present as precursor material in an area composed of marine sedimentary rocks, soils, or other environments. Common components of organic matter include algae, diatoms, plankton, bacteria, warms, animals, and vegetal debris. As organic material sinks, it is collected on the ocean floor where it accumulates and becomes a source rock. Due to specific geological circumstances and pressure, the source rock undergoes thermal maturation and turns into petroleum.
For the accumulation of petroleum, a trap must be present – a geological formation caused by the movement of the Earths tectonic plates. These traps work like caps, containing the petroleum within the region and preventing its passage. Common traps are anticlines, sagbasins, faults, stratigraphic traps, domes, shelf margins, and salt/shale diapirs. After the organic matter has undergone maturation and a trap is present, petroleum is ready to be located in the specific area.
Petroleum’s distribution varies greatly around the world, and is primarily located in supergiant fields with extraordinary high volumes. Current estimates show the top three countries with the highest petroleum reserves are Venezuela, Saudi Arabia, and Canada. While the majority of petroleum is located in the Middle East, there are certain global trends in terms of its distribution. Firstly, the majority of discoveries are located in emerging market countries. Oil reserves are also located in areas such as off-shore oceanic basins, contact organic-rich sedimentary rocks in marginal platforms, humid, tropical environments which support high levels of organic matter production and deposition, and certain tectonic regions. Additionally, certain geological and geochemical characteristics of landscapes determine the nature of petroleum accumulation and distribution.
In conclusion, petroleum is an essential resource and its formation is the result of millions of years of prehistoric organic material becoming buried in the Earth and undergoing maturation. In order for petroleum to accumulate in a region, the right conditions must be present. These conditions include organic matter, a source rock, and a trap. Petroleum has a wide distribution across the world with the majority located in the Middle East. Global trends in petroleum distribution are determined by factors such as the nature of the landscape, atmosphere and geography.
Petroleum is a vital resource that has been and continues to be an integral part of the global economy. Petroleum is formed from the breakdown of prehistoric organic material that undergoes maturation over millions of years. In order for petroleum to accumulate in a region, organic matter, a source rock, and a trap must be present. Petroleum’s distribution is extremely varied, however, it is primarily located in the Middle East and emerging market countries. Global trends are determined by the nature of the landscape, atmosphere, and geography of regions. Overall, petroleum is a valuable resource that has its origins in ancient organisms, and its accumulation and distribution are determined by specific Earth conditions.
