Petroleum
Petroleum is a fossil fuel formed over billions of years from the anaerobic decay of organic materials. Vast amounts of zooplankton and algae settled to sea or lake bottoms where they were covered in stagnant water. Water oxygen concentration dropped below 0.1 mg/L approximately one meter below this sediment layer. Anaerobic bacteria reduced sulfates and nitrates among the matter to hydrogen sulfide and nitrogen gas respectively. These bacteria used the organic matter as a source for other reactants. Polysaccharides and proteins hydrolyzed into simple sugars and amino acids. Monosaccharides ultimately decayed into carbon dioxide and methane. Fats and waxes did not extensively hydrolyze under these mild conditions. As further layers settled, intense heat and pressure built up in lower regions. This process caused the organic matter to change first into a waxy material known as kerogen. Temperatures reached around 50 degrees Celsius at a depth of about one kilometer from the Earth's surface. Kerogen formation represents a halfway point between organic matter and fossil fuels. The latter happened through catagenesis in which reactions were mostly radical rearrangements of kerogen. These reactions took thousands to millions of years with no external reactants involved. Heat for catagenesis came from the decomposition of radioactive materials of the crust including potassium-40 and uranium isotopes. Geologists often refer to the temperature range in which oil forms as an oil window. Below the minimum temperature oil remains trapped in the form of kerogen. Above the maximum temperature the oil is converted to natural gas through thermal cracking.
More than 4300 years ago bitumen was mentioned when Sumerians used it to make boats. A tablet of the legend of the birth of Sargon of Akkad mentions a basket closed by straw and bitumen. More than 4000 years ago asphalt was used in the construction of walls and towers of Babylon according to Herodotus and Diodorus Siculus. Great quantities of it were found on the banks of the river Issus one of the tributaries of the Euphrates. Ancient Persian tablets indicate medicinal and lighting uses of petroleum amongst the upper class. The use of petroleum in ancient China dates back more than 2000 years. The I Ching cites that oil in its raw state was first discovered extracted and used in China in the 1st century BCE. By 347 CE oil was produced from bamboo-drilled wells in China. In the 7th century petroleum was among essential ingredients for Greek fire an incendiary projectile weapon used by Byzantine Greeks against Arab ships attacking Constantinople. Crude oil was distilled by Persian chemists with clear descriptions given in Arabic handbooks such as those of Abu Bakr al-Razi. Streets of Baghdad were paved with tar derived from petroleum accessible from natural fields in the region. In the 9th century oil fields were exploited in the area around modern Baku Azerbaijan. These fields were described by Marco Polo in the 13th century who describes output of those wells as hundreds of shiploads. Sophisticated oil pits deep were dug by Seneca people and other Iroquois in Western Pennsylvania as early as 1415 to 1450. French General Louis-Joseph de Montcalm encountered Seneca using petroleum for ceremonial fires during a visit to Fort Duquesne in 1750.
Petroleum consists of a variety of liquid gaseous and solid components. Lighter hydrocarbons are gases methane ethane propane and butane. The bulk of liquid and solids are largely heavier organic compounds often hydrocarbons containing carbon and hydrogen only. Nitrogen oxygen and sulfur appear in other organic compounds along with traces of metals like iron nickel copper and vanadium. Four different types of hydrocarbon appear in crude oil including alkanes cycloalkanes aromatic hydrocarbons and asphaltics. Alkanes from pentane C5H12 to octane C8H18 refine into gasoline. Those from nonane C9H20 to hexadecane C16H34 become diesel fuel kerosene and jet fuel. Alkanes with more than 16 carbon atoms can be refined into fuel oil and lubricating oil. Paraffin wax is an alkane with approximately 25 carbon atoms while asphalt has 35 and up. Components separate by fractional distillation at an oil refinery to produce gasoline jet fuel kerosene and other fractions. During winter butane C4H10 blends into gasoline pool at high rates because its high vapor pressure assists cold starts. Aromatic hydrocarbons are unsaturated hydrocarbons that have one or more benzene rings. They tend to burn with a sooty flame and many have sweet aroma. Some are carcinogenic. Crude oil varies greatly in appearance depending on composition. It is usually black or dark brown although it may be yellowish reddish or even greenish. In the reservoir it is found in association with natural gas which forms a gas cap over petroleum and saline water which sinks beneath it.
According to US Energy Information Administration estimate for 2021 world consumes 97.26 million barrels of oil each day. About 80 percent of world's readily accessible reserves located in Middle East with 62.5 percent coming from Arab five: Saudi Arabia United Arab Emirates Iraq Qatar and Kuwait. Top three oil-producing countries as of 2018 are United States Russia and Saudi Arabia. In 2018 due to developments in hydraulic fracturing and horizontal drilling United States became world largest producer. Petroleum makes up 40 percent total energy consumption in United States but responsible for only one percent electricity generation. About 90 percent vehicular fuel needs met by oil. In 1950s shipping costs made up 33% price of oil transported from Persian Gulf to United States. With development of supertankers in 1970s cost of shipping dropped to 5% price of Persian oil in US. Share of shipping cost on final cost delivered commodity less than 3% in 2010. During 1973 oil crisis Saudi Arabia and other Arab nations imposed oil embargo against United States United Kingdom Japan and other Western nations which supported Israel in Yom Kippur War. This followed by 1979 oil crisis caused by drop in oil production wake of Iranian Revolution causing oil prices more than double. Two oil price shocks had many short and long-term effects on global politics and economy. They led to sustained reductions in demand as result substitution to other fuels especially coal and nuclear. High oil prices induced investment in oil production by non-OPEC countries including Prudhoe Bay Alaska North Sea offshore fields United Kingdom and Norway Cantarell offshore field Mexico and oil sands Canada.
About quarter annual global greenhouse gas emissions carbon dioxide from burning petroleum plus methane leaks industry. Along with burning coal petroleum combustion largest contributor increase atmospheric CO2. Atmospheric CO2 risen over last 150 years current levels over 415 ppmv from 180-300 ppmv prior 800 thousand years. Rise Arctic temperature reduced minimum Arctic ice pack loss almost half since satellite measurements started 1979. Ocean acidification increase acidity Earth's oceans caused uptake carbon dioxide atmosphere. Saturation state calcium carbonate decreases with uptake carbon dioxide ocean. Increase acidity inhibits all marine life having greater effect smaller organisms shelled organisms such as Pectinoidea. Crude oil refined fuel spills tanker ship accidents damaged natural ecosystems human livelihoods Alaska Gulf of Mexico Galapagos Islands France many other places. Quantity oil spilled during accidents ranged few hundred tons several hundred thousand tons Deepwater Horizon oil spill SS Atlantic Empress Amoco Cadiz. Smaller spills proven great impact ecosystems Exxon Valdez oil spill. Oil spills sea generally much more damaging land since spread hundreds square miles thin oil slick cover beaches thin coating oil. This kill sea birds mammals shellfish other organisms coat. Control oil spills difficult requiring ad hoc methods often large amount manpower. Dropping bombs incendiary devices aircraft wreck produced poor results modern techniques include pumping oil wreck like Prestige oil spill Erika oil spill.
Control petroleum production significant driver international relations during much 20th and 21st centuries. Organizations OPEC played outsized role international politics. Some historians commentators called this Age of Oil. With rise renewable energy addressing climate change some commentators expect realignment international power away petrostates. Oil rents described connected corruption political literature. A 2011 study suggests increases oil rents increased corruption countries heavy government involvement production oil. Study found increases oil rents significantly deteriorates political rights. Investigators say oil exploitation gave politicians incentive extend civil liberties reduce political rights presence oil windfalls evade redistribution conflict. Petroleum production linked conflict many years leading thousands deaths. Petroleum deposits very few countries around world. Conflicts start when countries refuse cut oil production which other countries respond actions increasing production causing trade war experienced 2020 Russia-Saudi Arabia oil price war. Other conflicts start countries wanting petroleum resources other reasons oil resource territory experienced Iran-Iraq War. German invasion Soviet Union included goal capture Baku oilfields provide much-needed oil supplies German military suffering blockades. Access oil major factor several military conflicts 20th century including World War II during oil facilities major strategic asset extensively bombed. In 1985-2003 oil glut even fueled sales low fuel economy vehicles OECD countries. 2008 economic crisis seemed had some impact sales such vehicles still 2008 oil consumption showed small increase.
Common questions
How was petroleum formed over billions of years?
Petroleum is a fossil fuel formed over billions of years from the anaerobic decay of organic materials. Vast amounts of zooplankton and algae settled to sea or lake bottoms where they were covered in stagnant water with oxygen concentration below 0.1 mg/L. Anaerobic bacteria reduced sulfates and nitrates while heat and pressure converted the matter into kerogen and eventually oil through catagenesis.
When did ancient civilizations first use petroleum for boats and construction?
More than 4300 years ago bitumen was mentioned when Sumerians used it to make boats. More than 4000 years ago asphalt was used in the construction of walls and towers of Babylon according to Herodotus and Diodorus Siculus. The I Ching cites that oil in its raw state was first discovered extracted and used in China in the 1st century BCE.
What chemical components are found inside crude oil?
Petroleum consists of a variety of liquid gaseous and solid components including lighter hydrocarbons like methane ethane propane and butane. The bulk of liquid and solids are largely heavier organic compounds often hydrocarbons containing carbon and hydrogen only. Nitrogen oxygen and sulfur appear in other organic compounds along with traces of metals like iron nickel copper and vanadium.
Which countries hold the majority of world's readily accessible oil reserves as of 2018?
About 80 percent of world's readily accessible reserves located in Middle East with 62.5 percent coming from Arab five: Saudi Arabia United Arab Emirates Iraq Qatar and Kuwait. Top three oil-producing countries as of 2018 are United States Russia and Saudi Arabia. In 2018 due to developments in hydraulic fracturing and horizontal drilling United States became world largest producer.
How does burning petroleum contribute to global greenhouse gas emissions?
About quarter annual global greenhouse gas emissions carbon dioxide from burning petroleum plus methane leaks industry. Along with burning coal petroleum combustion largest contributor increase atmospheric CO2. Atmospheric CO2 risen over last 150 years current levels over 415 ppmv from 180-300 ppmv prior 800 thousand years.