Introduction

Oil is a natural substance extracted from geological formations within the Earth's crust, where it may accumulate through a slow transformation process of organic materials that has lasted for ages and relatively long epochs. Chemically defined, oil is a complex mixture of hydrocarbons. Its appearance, color, and composition vary significantly depending on the extraction location, and it is considered a natural raw material. When extracted from beneath the Earth's surface, it is also referred to as crude oil.

Crude oil undergoes a refining process to obtain various types of petroleum products. This involves a fractional distillation technique, which separates it into a range of blends distinguished by their boiling points in a distillation tower. These blends are commonly referred to as "fractions." Classified as a fossil fuel, oil forms beneath the Earth's deep layers from significant quantities of extinct organisms (fossils) such as plankton, algae, and other marine life. The organic matter is buried under sedimentary rocks, undergoes decomposition due to the absence of oxygen, and experiences high pressure and temperature below the Earth's surface.

Oil is extracted from reservoirs underground, known as oil wells, by drilling the Earth's crust after conducting a geological survey to test the permeability and porosity of the geological reservoir.

Oil is a crucial primary source of energy, earning it the nickname "black gold" due to its high economic significance. Light fractions are primarily used in automotive and aviation fuel blends, while heavy fractions are utilized in electricity generation, industrial processes, and operating heavy machinery.

Moreover, oil serves as the raw material for many chemical industries, producing various products such as fertilizers, insecticides, plastics, fabrics, and pharmaceuticals.

The Arab region, especially the Arabian Gulf, is among the world's richest in oil reserves and is a leading producer and exporter of oil, typically transported through pipelines or tankers. The rate of oil consumption increases with human progress and dependence on this resource as a primary energy source, with oil prices playing a crucial role in global economic performance. However, oil reserves are vulnerable to depletion and non-renewability, especially with the ongoing approach of what is known as peak oil, the maximum rate of global oil production. This has prompted the search for and development of new energy alternatives, such as renewable energy sources.

The excessive use of oil and other fossil fuels has negatively impacted the biosphere and the Earth's environmental system. Oil spills, in particular, often cause environmental disasters, and the combustion of fossil fuels is a major contributor to global warming.

The Chemical and Physical Properties of Oil

Oil Exploration

The exploration for oil typically begins with a preliminary geological survey of remote areas, often aided by the terrain's characteristics to identify potentially oil-rich regions. The identification process is generally easier on land than at sea. Surveying can involve studying data collected from aerial imaging. However, geological surveys conducted by geologists in potential areas provide more meaningful data about oil reserves, especially when studying the types of rocks present. The directed search mission for underground resources is referred to as oil exploration, and it commonly employs technological methods based on natural physical laws that provide indications of the presence of oil or gas. These measurements include gravity and magnetic measurements, as well as seismic surveys of the studied areas.

In the initial stages of exploration, a geological study is conducted to understand the nature of the rocks. The nature of the sedimentary basin is then examined using gravity and magnetic measurements of the reservoir. Subsequently, a seismic survey is conducted by sending sound waves into the Earth's crust and studying the variations in reflectivity using land-based and underwater speakers in the seas. The data obtained from the speakers, including time duration and distinctive properties of reflected signals, are essential inputs for forming a preliminary image of geological layers beneath the Earth's crust. Seismic surveys in the early stages are two-dimensional, and if significant results are obtained, a three-dimensional survey is conducted. Since offshore oil exploration is more challenging and comes with the risks of failure, additional methods such as electromagnetic measurements are often employed.

Oil Extraction

Wells are drilled to extract oil from reservoirs beneath the Earth's surface. The pressure of the reservoir beneath the Earth's surface plays a crucial role in the ascent of hydrocarbon fluids to the surface. Initially, primary methods are employed, distinguishing between two approaches. The first is the "natural lift" method, relying on the natural reservoir pressure that forces the oil to the surface in the early stages of well life. As time progresses, natural pressure decreases, leading to the adoption of the "artificial lift" method. This method ensures sufficient pressure for oil extraction, either through specialized pumps or by injecting oil or gas.

Afterward, secondary extraction methods are utilized, such as water injection to increase pressure and compel the oil to reach the extraction pipes. Once primary and secondary methods are exhausted, tertiary methods, known as enhanced oil recovery, come into play. These methods may involve using carbon dioxide gas to maintain pressure in the reservoir.

Drilling at sea is more challenging than on land, requiring the installation of offshore platforms to provide a stable platform for extraction operations. Additional drilling techniques, such as directional drilling, are commonly applied on offshore platforms. Several studies are conducted to develop oil extraction methods from the sea, including the idea of using robots operating on the seafloor. Unconventional oil extraction involves surface mining methods, as seen in the extraction of oil sands.

Russia and Saudi Arabia have been leading global oil producers since the beginning of the 21st century, followed by the United States, Iraq, Iran, and China. (For more details, refer to the list of countries by oil production.) OPEC member countries contribute to approximately 40% of global production (2014 statistics).

Consumption

Oil consumption is closely linked to the global economic situation, with a strong correlation between oil consumption and various industrial sectors. For example, the automotive industry has continuously thrived since the late 20th century and the early 21st century, primarily due to the growth of the automotive sector. The abundance of oil in the 1980s supported the sales of fuel-consuming vehicles in countries of the Organization for Economic Cooperation and Development, while the 2008 economic crisis impacted the sales of such vehicles. Generally, the relationship between global oil production, price, and investments is related to supply and demand factors, according to data from the International Energy Agency.

The United States is the largest oil-importing country globally, followed by the European Union as a whole. Considering individual countries, China, Japan, and India follow the United States in terms of consumption. (For more details, refer to the list of countries by oil consumption.) Some major countries import additional quantities beyond their consumption to secure their strategic oil reserves, especially during times of crises.

Chemistry of Oil

Oil is a mixture of a large number of different hydrocarbons, with the most common being linear alkanes (paraffins), cyclic alkanes (naphthenes), and aromatic hydrocarbons (arenes). Additionally, there is a presence of complex asphaltene compounds. Each oil mixture has its unique composition of constituent molecules, ultimately determining its general physical properties such as color and viscosity.

There are several types of hydrocarbons based on the degree of saturation. Alkanes (or paraffins) are saturated hydrocarbons, meaning they only contain single bonds in their structure. Their general formula is CnH2n+2, and the carbon structure can be either linear or branched, with a carbon atom count reaching up to 40 atoms per molecule. Alkanes with carbon atoms ranging from 1 to 4 are gaseous components in natural gas associated with oil, which can be either flared in oil refineries or processed. Typically, alkanes from pentane (C5H12) to octane (C8H18) are components of gasoline, while higher alkanes from nonane (C9H20) to hexadecane (cetane C16H34) are components of diesel, kerosene, aviation fuel, and jet fuel.

Higher alkanes with a carbon atom count exceeding 26 are usually repeated into fuel oil for large engines and lubricating oils for machinery. As the carbon atom count increases, the physical state of hydrocarbons changes from liquid to solid. Alkanes with more than 25 carbon atoms exist as paraffin wax, while asphaltenes contain alkanes with more than 35 carbon atoms, which can be catalytically cracked into smaller hydrocarbons of greater significance or mixed with other components to manufacture asphalt used in road paving.

Cycloalkanes (or naphthenes) are also saturated hydrocarbons, but their carbon structure forms a closed ring with a general formula of CnH2n. They share relatively similar properties with linear alkanes. Aromatic hydrocarbons are cyclic compounds as well but are unsaturated, with a benzene ring (C6H6) as their basic unit. The degree of unsaturation changes as the structure becomes more complex, especially with the fusion of multiple rings, as seen in compounds like coronene.

Previously, sulfur content in heavy oil types would burn through oxidation reactions into sulfur dioxide and further into sulfur trioxide, eventually leading to sulfuric acid through subsequent chemical processes. However, the release of acidic gases into the atmosphere resulted in the phenomenon of acid rain, which had catastrophic effects on the environment. Therefore, methods like hydrodesulfurization or flue gas desulfurization have been employed to reduce sulfur content in various petroleum derivatives.

Different particles present in an oil sample can be identified through laboratory analysis. Fractionation is conducted to simplify the structure by dividing it into various components based on chemical and physical properties. One such method is the SARA fractionation technique, which categorizes oil into four groups: Saturates (S), Aromatics (A), Resins (R), and Asphaltenes (A). Each group can be further analyzed using various analytical methods, such as gas or liquid chromatography, with suitable detectors like flame ionization or mass spectrometry.

Environmental Impact: The exposure of ecosystems to oil and its derivatives leads to pollution, especially since hydrocarbons are not miscible with water. Most negative effects caused by oil derivatives on the environment are of human origin. However, there are rare cases where oil reaches environmental media through natural means, such as seepage to the Earth's surface or the formation of natural tar pits. These cases have similar negative effects on the environment as human activities but on a narrower scale.

The negative effects of oil and its derivatives on the environment include ocean acidification, global warming, and oil spills. The extraction of oil is accompanied by the use of specific chemicals that may be contaminated, especially in offshore platforms.

Oil Spill

When an oil spill occurs on land, the environmental impact is severe, but it is relatively easier to contain compared to spills that happen in aquatic environments. Oil spills from oil tankers, on the other hand, have catastrophic effects on marine ecosystems. Marine oil spills lead to the destruction of marine life in the affected area, affecting all marine organisms, including birds, fish, mammals, crustaceans, algae, and others. This has been evident in several regions worldwide, such as the 2010 Gulf of Mexico oil spill. The quantity of leaked oil varies according to the disaster's scale, ranging from hundreds of tons to several hundred thousand tons, as seen in incidents like the sinking of the Amoco Cadiz in the Atlantic Ocean in 1978 or the sinking of the Atlantic Empress near the Caribbean in 1979.

Containing an oil spill is a challenging task that requires substantial material and technological resources. The techniques used for containment are continuously evolving. In the past, there have been unsuccessful attempts at containment, such as when the Torrey Canyon tanker was bombed off the British coast in 1967. Sometimes, efforts to mitigate the impact of an oil spill involve trying to extract oil from the sunken tanker using pumps, as was done in the Prestige and Erika tanker incidents. Some scientific studies have shown the ability of certain bacteria, such as microorganisms and fungi, to analyze specific chemical compounds present in oil, especially nitrogen-containing compounds like pyridine, picoline, and quinoline. The concentration of tarballs is measured to assess the extent of oil spill dispersion.

Radioactive Waste

During oil drilling, rocks may contain quantities of radioactive elements, often belonging to a specific decay series of a radioactive element such as uranium, thorium, radium, or others. These materials are collectively known as Naturally Occurring Radioactive Materials (NORM). The risk of these radioactive materials leaking into groundwater becomes evident during drilling operations. Groundwater extracted with oil is commonly referred to as "produced water," and it contains various salts like barium, calcium, and strontium. As this water ascends to the surface due to reduced pressure and temperature, salts precipitate in the form of scales containing traces of radioactive elements like radium.

Typically, the residues from deposits and rocks are left as radioactive waste. The level of radiation in these residues varies depending on the drilling location. For example, the radioactivity in scales containing radium is around 15,000 becquerels per gram. In Germany, documented radioactive residues have an average radiation activity of 40 becquerels per gram, without suitable coding for proper storage or transportation. This environmental issue accompanies oil extraction operations worldwide, necessitating the establishment of regulations and controls, whether at the local or international level.

API Gravity Scale

The API gravity is a measure of specific gravity, indicating the ratio of the weight of a specific volume of a substance to the weight of an equivalent volume of water. Due to the variation in the volume of liquids with changes in temperature and pressure, the weight of a specific volume of oil is measured for its specific gravity under standard conditions, typically at 60 degrees Fahrenheit (16 °C) and atmospheric pressure. The American Petroleum Institute (API) has established a scale specifically for expressing the specific gravity, and this API gravity scale has become widely used globally for its ease of use. The API scale corresponds to water with a specific gravity of one, resulting in a scale value of 10 (the lower the specific gravity, the higher the API value).

Oil prices are determined based on the specific gravity, with light oils having higher prices compared to heavy oils due to their higher content of petroleum products demanded in the markets. On the other hand, oils with light or colorless appearances exhibit higher API values. For instance, medium oils tend to have a greenish color, while heavy oils are characterized by darker colors like black.

Importance of API Gravity:

Firstly:  Oil Classification

• According to this scale, oil is classified into different grades based on its specific gravity in relation to water, ranging from heavy to medium to light.
• The higher the API gravity, the lighter the oil, and vice versa.
• Density is measured using the API gravity scale by the American Petroleum Institute (API), and oil is categorized as follows:

A. Light if its API value is greater than 31.10

B. Medium for values between 22.30 and 31.10

C. Heavy if the API value is less than 22.30.

Secondly:  Calculating the Number of Barrels of Crude Oil per Metric Ton

This is determined by the following relationship:

The Mathematical Formula for API Gravity Law

The mathematical formula for calculating specific gravity (SG) according to the API is as follows:

Therefore, for heavy crude oil, its specific gravity (SG) is calculated using the API scale as follows:

Abstract

Despite the continuous increase in consumption, advancements in oil extraction methods (such as enhanced oil extraction technologies) and the ongoing evolution of unconventional oil extraction techniques have led to a state of static equilibrium. The gap between consumption and production remained relatively constant until the late second decade of the 21st century. The estimated calculation of the peak oil has varied with the development of unconventional oil extraction methods like directional drilling and hydraulic fracturing, which resulted in an increase in oil production and contributed to the decline in oil prices in late 2014.

Since the late 20th century, there has been a focus on finding alternative energy sources, leading to the development of renewable energy technologies with environmentally friendly features, such as solar energy, wind energy, hydroelectric power, and others, for electricity generation. Additionally, various new types of alternative fuels for vehicles have been developed, such as flexible-fuel vehicles using blends of fossil fuels with other fuels like biodiesel or methanol. There are also vehicles utilizing different types of fuels such as natural gas, hydrogen, or fuel cells. Hybrid vehicles, such as plug-in hybrid electric vehicles, have also been developed with either internal batteries or external charging sources.

Hydrocarbons extracted from oil serve as primary materials in the chemical industries to produce essential products in daily life. Alkenes can be used to produce plastics, while higher alkanes are used in the preparation of lubricating oils and are involved in the composition of wax. Aromatic compounds are utilized in various chemical industries, including pharmaceuticals, pesticides, fertilizers, and more.

Oil is the primary resource and mainstay of the economy in several countries, referred to as an "oil economy."

There are two main methods for global oil transportation for export and import: through oil tankers by sea or through oil pipelines by land. Examples of well-known pipelines include Nord Stream for gas transportation and Druzhba for oil transportation.

In the 1950s, the cost of transporting oil from the Arabian Gulf to the United States was about 33% of the oil price. However, due to the development of the oil tanker industry, the cost decreased to between 3-5% in the early 21st century.

Crude oil is generally classified in several ways: by geographical production location, by specific gravity according to the American Petroleum Institute (API), or by sulfur content.

Crude oil is considered light if its density is low and heavy if its density is high. The density is measured according to the API gravity scale, and crude oil is classified as light if its value is greater than 31.10, medium at values between 22.30 and 31.10, and heavy when its API gravity is less than 22.30.

On the other hand, crude oil can be described as sweet if it has a low sulfur content and sour if it has a high sulfur content. The closer the specifications of crude oil are to being light and sweet, the more desirable it is, and its value increases. Processing heavy or sour crude oil presents additional technical and environmental challenges.

Approximately 84% of the hydrocarbons in oil are used in the production of various high-energy-content fuels, including liquefied petroleum gas, motor gasoline (petrol), aviation fuel, kerosene, fuel oil (diesel), and diesel.

Different petroleum derivatives emit carbon dioxide (CO2) when burned, and its concentration in the atmosphere has increased significantly in recent decades. As CO2 is a greenhouse gas, the increase in its concentration in the atmosphere leads to global warming, with most emissions originating from the burning of fossil fuels in various human activities. Additionally, the phenomenon of ocean acidification occurs due to the absorption of CO2 from the atmosphere by the oceans.

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