Petroleum Extraction and Processing

Summary

Petroleum extraction and processing is the human exploitation of fossil fuels consisting of hydrocarbons in the form of crude oil and natural gas. The primary use of processed petroleum products is as powerful fuels, particularly for transportation in the form of gasoline, diesel fuel, jet fuel, and heating. The remainder of processed petroleum products are used in the petrochemical industry as fuel additives and to create applications such as plastics, specialty chemicals, solvents, fertilizers, pesticides, and pharmaceuticals. Worldwide, over 70 million barrels of crude oil are extracted each day.

Definition and Basic Principles

Petroleum extraction and processing encompass the activities through which crude oil and natural gas are taken from their natural reservoirs below the Earth's surface on land and sea and treated so they can be used as fuels and materials for the petrochemical industry. Reservoirs can be detected by applying the results of petroleum geology, the science describing under what circumstances oil and gas reservoirs were created during ancient times and how they can be found.

Once a likely reservoir is identified, exploratory drilling through the ground begins, either on land or at sea. When a well strikes a reservoir, the size of its area is estimated. Depending on whether crude oil or natural gas is dominant, the reservoir is called an oil or gas field. Many wells are drilled to extract oil and gas from fields that can be quite vast, extending for hundreds or thousands of square kilometers (or miles) under the surface. From the discovery of the first oil well in 1859, over 50,000 oil fields have been discovered worldwide.

Usually, natural pressure forces gas and oil to the surface. In mature wells, however, pressure must be added by technical means. After gas and oil are extracted, both are sent by pipelines for further processing.

Processing natural gas separates almost all other components from its key ingredient, methane. Processing crude oil occurs in a refinery. Because the different components of crude oil vaporize at different temperatures, they can be separated by distillation. To obtain the most desirable end products, the components are further treated through chemical processes called cracking and reforming.

Background and History

Modern petroleum use was based on the demand for kerosene for lighting. Polish pharmacist Ignacy Łukasiewicz discovered how to distill kerosene from petroleum in 1853. He dug the first modern oil well in 1846 and the world's first refinery in 1856.

Retired railway conductor Edwin Drake dug the first oil well in the United States at Titusville, Pennsylvania, on August 28, 1859. His drilling method, using a pipe to cover a drill suspended from a rig and leading the pipe into the Earth to prevent the borehole from collapsing, was widely copied as he did not patent it. It is still the basic drilling mechanism. Horizontal rather than vertical drilling, which allows easier access to the reservoir of an oil field, revolutionized crude oil extraction in the 1990s.

The appearance and spread of the internal combustion engine by the late nineteenth century led to crude oil being refined to produce gasoline. The quest to extract more gasoline led to the application of thermal cracking in 1913, and by 1975, many subsequent new cracking techniques had culminated in residual hydrocracking. Beginning in 1916, processes were invented to decrease the unwanted sulfur content of crude oil. Since 1939, visbreaking has been used to make smoother-flowing products, and isomerization and alkylation have increased gasoline yield and quality since 1940. Modern refineries try to make these processes as efficient and clean as possible.

How It Works

Exploration. Almost all exploration of new oil and gas fields is done by geophysical means such as seismic reflection or other seismic, gravity, or magnetic surveys. These surveys use the different densities of subterranean rock formations to identify source rock formations likely to hold hydrocarbons. Based on this information, three-dimensional computer models are generated and analyzed. Once petroleum engineers and geologists have decided on a promising prospect, exploratory drilling begins.

Extraction. Oil and gas deposits are accessed by drilling a well from a rig, either on land or in the sea. Rigs are adapted to their particular environment but share some common elements. Suspended from a metal tower called a derrick, the drilling bit hangs from its drilling string over the well bore, the borehole where the well is dug. As the drilling bit goes deeper, the borehole is fitted with a pipe to prevent collapse. The pipe is placed in a larger steel casing, leaving space between the pipe and the casing. Drilling mud descends through the pipe to cool the drilling bit as it bores into the rock and percolates back to the surface between the pipe and casing. On the sea, the rig is placed on an offshore oil platform. Modern drills can dig thousands of meters (or feet) deep.

Drilling is successful when the well strikes petroleum deposits below their seal rock. Natural pressure ejects gas and oil through the pipe. A wellhead is placed on the top of the well, and natural gas is separated from crude oil in a separator unit. Both products are collected and transported by intermediary pipelines connecting the many wells of a single field.

Primary recovery continues as long as natural pressure ejects petroleum. Once this pressure decreases, water or gas is pumped into the reservoir to create artificial pressure during secondary recovery. The well is considered exhausted when maintaining artificial pressure is no longer economical.

Processing. Natural gas has to be cleaned in gas processing plants typically built close to the point of extraction. It is separated from its water and natural gas condensate (also called natural gasoline), and the latter is sent to a refinery. Then, it is stripped of its acid gases (carbon dioxide, hydrogen sulfide, and other gases with sulfur content), which are desulfurized and often burned as tail gases. To gain as much pure methane, its main component, as possible, natural gas undergoes a further series of processes to remove contaminants (such as mercury) and nitrogen. Natural liquid gases (NLGs) are removed for use as feedstock in petrochemical plants. Then, consumer-grade natural gas is ready for sale.

Crude oil is processed at a refinery. Refineries need not be close to oil fields as crude oil can be transported by pipeline or ocean tanker. A refinery, which is a highly integrated chemical plant, seeks to create the most desirable products out of crude oil. These products are hydrocarbon chains with few rather than many carbon atoms (called light instead of heavy).

First, crude oil is desalted, then it is separated into its various components, called fractions, by atmospheric distillation. As crude oil is heated, its different fractions vaporize at different temperatures and are removed separately. All fractions are processed further. The lightest fraction, distilled gas, is subjected to sulfur extraction. The heaviest fraction, called atmospheric bottom, undergoes vacuum distillation. Most distilled fractions undergo hydrotreatment, which is an infusion of hydrogen to remove sulfur.

Its fluid catalytic cracker and hydrocracker are at the heart of a refinery. They break down heavy (long) hydrocarbon chains into lighter (shorter) ones. A catalytic reformer creates higher-octane reformate, a more valuable naphtha distillate. Isomerization and alkylation are chemical processes that boost the distillate's octane rating. Refineries send their products to end users or the petrochemical industry.

Applications and Products

Gasoline. The most common and valuable petroleum product is gasoline. Typically, around half of US crude oil is processed into gasoline of various qualities. As fuel for the internal combustion engine, gasoline is essential for any industrial society. It is used by most cars and many light trucks. Aviation gasoline fuels piston-engine airplanes.

Refineries seek to optimize their gasoline output and create blends that minimize damaging spontaneous combustion in engines called knocking. Lead was used until the 1970s, but because of its harmful effects, it has been prohibited in most industrialized nations. Instead, chemists have developed a variety of alternative additives.

Diesel and Fuel Oils. The second most important petroleum products, which account for about one-third of US crude oil, are diesel and other fuel oils. These fuel oils have longer hydrocarbon chains than gasoline and thus boil at higher temperatures. Diesel is fuel for trucks, buses, ships, locomotives, and automobiles. In Europe, diesel engines are very popular for automobiles as they are more fuel-efficient. Environmentalists have expressed concern about burning these fuels because the process creates the pollutant sulfur dioxide. The US Environmental Protection Agency (EPA) set standards for diesel's sulfur content, and cleaner-burning fuels that significantly reduce particulate emissions, like Ultra Low Sulfur Diesel (ULSD) fuel, were developed. Diesel consumption contributes significantly to transportation-related greenhouse gas (GHG) emissions. Every gallon (3.8 liters) of diesel fuel releases twenty-two pounds (ten kilograms) of carbon dioxide. Similarly, ethanol-free gasoline produces around twenty pounds (nine kilograms) of carbon dioxide.

Heavy fuel oils account for another 2.4 percent of petroleum products processed from crude oil. Among them, bunker oil is the heaviest. It is used to fuel large ship engines.

Natural Gas. Natural gas, which may be found alongside oil and accounts for less than 4 percent of US refinery yields, is used for generating electric power, domestic and industrial heating, and increasingly transportation by bus or automobile. Europe has a dense network of pipelines bringing natural gas, primarily from Russia, to industrial and domestic consumers.

Natural gas can be liquefied (as liquefied natural gas, LNG) for transport by gas tankers across oceans. This is the preferred method to bring natural gas from gas fields in the Middle East, North Africa, and the Caribbean to Europe and the United States. After reaching the destination, LNG is gasified and pumped into a pipeline at the port terminal. When natural gas is compressed below 1 percent of its volume, it forms compressed natural gas (CNG). CNG can be used in various applications, such as clean fuel in cars and buses.

Jet Fuel. Jet fuel powers gas-turbine engines of airplanes (jets). Its production amounts to about 9.5 percent of processed crude oil in the US. Commercial jet fuel is produced according to international standards. It is either Jet A or Jet A-1, with Jet A freezing at –40 degrees Celsius (–40 degrees Fahrenheit) and A-1 at –47 degrees Celsius (–52.6 degrees Fahrenheit). Jet B is a lighter, more flammable jet fuel for cold regions, such as northern Canada. Military jet fuel is produced according to individual national standards.

Liquefied Petroleum Gas. The result of distilling the remaining gas from crude oil at a refinery, liquefied petroleum gas (LPG), is composed of a mixture of propene, propane, butene, and butane. It is usually compressed in tanks and stored as a liquid. LPG is widely used for domestic heating, water heaters, and cooking in Asia, South America, and Eastern Europe and is a common outdoor cooking fuel for campers, off-grid homes, and gas cooktops in the United States. LPG is also a global fuel alternative for automobiles.

Petrochemicals. Petrochemicals such as naphthas are often byproducts of gasoline production. They are grouped as olefins or aromatics. The value of petrochemicals has been rising consistently as new chemical processes have found additional applications.

After they leave a refinery, most petrochemicals are used as feedstock for petrochemical plants. Among olefins, ethylene and propylene are building blocks for plastics and specialty chemicals. The olefin butadiene is processed to eventually form synthetic rubber. Among aromatics, benzene is used to produce synthetic dyes, detergents, and such innovative products as polycarbonates that form light, hard plastic shells in many electronic items such as mobile phones. Toluene and xylene are used as solvents or building blocks for other chemicals, creating, for example, polyester fibers.

Petrochemicals are also used to create adhesives, food ingredients, and pharmaceuticals. They have become a source of much innovative chemical research.

Lubricating Oils. Although their volume accounts for only 1 percent of petroleum products leaving a US refinery, lubricating oils and greases are important for the machines and engines of industrialized nations. Refineries create a great variety of lubricating oils composed of 80 to 90 percent pure petroleum hydrocarbon distillate with different additives. The most commonly used lubricating oils, motor and hydraulic oils, are often recycled, keeping them from polluting the soil and groundwater.

Asphalt. The heaviest product from crude oil, asphalt, makes up about 2 percent of US refinery products. Bitumen, a viscous liquid occurring naturally or produced from refined petroleum, is combined with a mixture of minerals called construction aggregate to create asphalt. Concrete asphalt for durable roads and runways is the most common North American asphalt use, followed by roof shingles. Asphalt can also be used as an emulsion, flux, and stabilization material (its mixture with petroleum solvent is called cutback asphalt).

Careers and Course Work

Students interested in the petroleum industry should take science and mathematics courses, particularly chemistry and physics, in high school. College students should seek a bachelor's of science. The choice of science to study depends on whether the student wishes to pursue a career in exploration and production or processing and petrochemicals.

For the former, the geosciences, particularly geology, geophysics, mining, hydrology, and hydrogeology, as well as chemistry, are helpful. Computer literacy and the ability to work with specific applications in geology, particularly three-dimensional sensing and modeling, is important. Oil companies will welcome successful graduates with a bachelor's of science in geology, hydrogeology and engineering, chemical engineering, geology and mining, or even physics. A master's or engineering degree in these fields will provide additional opportunities. For example, a master's of science in petroleum engineering or environmental engineering geology can lead to an advanced entrance position as a reservoir geologist. One of the most important criteria for top positions, however, is years of practical work experience. Because increasing responsibilities lead toward management, it would not be uncommon for a senior geologist to hold a master of business administration degree and a science degree.

A bachelor of science in chemistry or a related field is a good foundation for a petroleum processing career at a refinery or petrochemical plant. A master's or doctoral degree in chemistry or chemical engineering, as well as in mechanical, environmental, or control engineering, will serve for an advanced position.

The oil and gas industry also employs many laboratory scientists and technicians. Corporate research and development departments are typically headed by scientists with doctorates in chemistry and related sciences.

Because of the oil and gas industry's cyclical nature, there are periods in which skilled employees, such as drilling engineers, are in high demand. Still, these workers also experience layoffs during downturns. Work can be at remote locations, and global mobility is often expected.

Social Context and Future Prospects

The late-nineteenth-century discovery that crude oil and natural gas could be turned into powerful fuels for industrialized society meant that those nations where oil and gas were found possessed a precious natural resource. However, using and distributing wealth from petroleum was a huge social challenge.

The industrialized nations' dependence on petroleum products has significantly influenced global politics since the early twentieth century. Since the late 1980s, there has been increasing concern that the massive burning of hydrocarbon fuel causes global warming because of the accumulation of greenhouse gases in the atmosphere. Over the ensuing decades, various methods were employed worldwide to address the problem—from increasing the efficiency of hydrocarbon-reliant technologies, such as automobiles and power plants, to creating alternative devices and energy sources to creating emissions caps and carbon pricing schemes for polluters. However, petroleum-related carbon emissions continued to rise.

Oil spills from wells or when crude oil tankers run aground can be major environmental disasters. On April 20, 2010, an explosion destroyed the Deepwater Horizon oil drilling platform in the Gulf of Mexico. The resulting gas and crude oil spill was the largest disaster of its kind in US history and the second-largest in the world. From a well on the ocean floor, about 1,500 meters (about 5,000 feet) below the surface, between 35,000 to 60,000 barrels leaked into the ocean daily for more than 85 days. In 2016, a financial settlement of over $8 billion was reached, but restoration of the site continued into the third decade of the twenty-first century. After the incident, the US National Oceanic and Atmospheric Administration (NOAA) started the satellite-based Marine Pollution Surveillance Program to routinely monitor American coasts to provide early detection of spills and better understand the impact of such accidents.

There is ongoing scientific debate over when Earth's petroleum resources will be depleted. In 1956, American geoscientist Marion King Hubbert published his theory of peak oil, in which he tried to calculate when the volume of petroleum extracted would exceed the volume of remaining petroleum reserves. A concerted effort involving new exploration and extraction technologies seeks to discover even more remote reserves, particularly deep under the sea and in the Arctic, and to develop oil shale and oil sands more efficiently and economically. Another area of ongoing interest is recycling petroleum products, such as asphalt, lubricants, and petrochemicals. In the early 2020s, various research and governmental agencies agreed the world would exhaust its oil supply by 2050. Accelerated exploration of undiscovered oil reserves was needed to meet demands despite transitioning from fossil fuels.

Scientists have also predicted that future alternative fuels, including those derived from hydrogen or renewable resources, will take the role of petroleum in the coming years. Hydrogen fuel cells are gaining ground in various applications, including electricity generation and transportation. Around 250 megawatts (MW) of electricity was sourced through US hydrogen fuel cell plants in 2020. By the end of 2022, this increased to 350 MW. Many automobile makers began producing hydrogen-fueled vehicles in the US. The adoption of these vehicles has been slow due to the cost of fuel cells and the low number of hydrogen fueling stations. Over time, the technology has become increasingly accepted.

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