搜尋結果
The formation of oil takes a significant amount of time with oil beginning to form millions of years ago. 70% of oil deposits existing today were formed in the Mesozoic age (252 to 66 million years ago), 20% were formed in the Cenozoic age (65 million years ago), and only 10% were formed in the Paleozoic age (541 to 252 million years ago).
- Graphite
Graphite is a mineral composed of stacked sheets of ...
- Carbon Capture and Storage
Former oil and gas fields can be used as places to ...
- Graphite
Crude oil may also be found in a semi-solid form mixed with sand and water, as in the Athabasca oil sands in Canada, where it is usually referred to as crude bitumen. In Canada, bitumen is considered a sticky, black, tar-like form of crude oil which is so thick [66
- 83 to 85%
- 0.1 to 2%
- 10 to 14%
- 0.05 to 1.5%
- Overview
- Chemical and physical properties
- Extraction and processing
crude oil, liquid petroleum that is found accumulated in various porous rock formations in Earth’s crust and is extracted for burning as fuel or for processing into chemical products.
A summary treatment of crude oil follows. For full treatment, see petroleum, petroleum production, and petroleum refining.
Britannica Quiz
13 True-or-False Questions from Britannica’s Easiest Science Quizzes
Crude oil is a mixture of comparatively volatile liquid hydrocarbons (compounds composed mainly of hydrogen and carbon), though it also contains some nitrogen, sulfur, and oxygen. Those elements form a large variety of complex molecular structures, some of which cannot be readily identified. Regardless of variations, however, almost all crude oil ranges from 82 to 87 percent carbon by weight and 12 to 15 percent hydrogen by weight.
Crude oils are customarily characterized by the type of hydrocarbon compound that is most prevalent in them: paraffins, naphthenes, and aromatics. Paraffins are the most common hydrocarbons in crude oil; certain liquid paraffins are the major constituents of gasoline (petrol) and are therefore highly valued. Naphthenes are an important part of all liquid refinery products, but they also form some of the heavy asphaltlike residues of refinery processes. Aromatics generally constitute only a small percentage of most crudes. The most common aromatic in crude oil is benzene, a popular building block in the petrochemical industry.
Because crude oil is a mixture of such widely varying constituents and proportions, its physical properties also vary widely. In appearance, for instance, it ranges from colourless to black. Possibly the most important physical property is specific gravity (i.e., the ratio of the weight of equal volumes of a crude oil and pure water at standard conditions). In laboratory measurement of specific gravity, it is customary to assign pure water a measurement of 1; substances lighter than water, such as crude oil, would receive measurements less than 1. The petroleum industry, however, uses the American Petroleum Institute (API) gravity scale, in which pure water has been arbitrarily assigned an API gravity of 10°. Liquids lighter than water, such as oil, have API gravities numerically greater than 10. On the basis of their API gravity, crude oils can be classified as heavy, medium, and light as follows:
•Heavy: 10–20° API gravity
•Medium: 20–25° API gravity
•Light: above 25° API gravity
Crude oil occurs underground, at various pressures depending on depth. It can contain considerable natural gas, kept in solution by the pressure. In addition, water often flows into an oil well along with liquid crude and gas. All these fluids are collected by surface equipment for separation. Clean crude oil is sent to storage at near atmospheric pressure, usually aboveground in cylindrical steel tanks that may be as large as 30 metres (100 feet) in diameter and 10 metres (33 feet) tall. Often crude oil must be transported from widely distributed production sites to treatment plants and refineries. Overland movement is largely through pipelines. Crude from more isolated wells is collected in tank trucks and taken to pipeline terminals; there is also some transport in specially constructed railroad cars. Overseas transport is conducted in specially designed tanker ships. Tanker capacities vary from less than 100,000 barrels to more than 3,000,000 barrels.
The primary destination of crude oil is a refinery. There any combination of three basic functions is carried out: (1) separating the many types of hydrocarbon present in crude oils into fractions of more closely related properties, (2) chemically converting the separated hydrocarbons into more desirable reaction products, and (3) purifying the products of unwanted elements and compounds. The main process for separating the hydrocarbon components of crude oil is fractional distillation. Crude oil fractions separated by distillation are passed on for subsequent processing into numerous products, ranging from gasoline and diesel fuel to heating oil to asphalt. The proportions of products that may be obtained by distillation of five typical crude oils, ranging from heavy Venezuelan Boscan to the light Bass Strait oil produced in Australia, are shown in the figure. Given the pattern of modern demand (which tends to be highest for transportation fuels such as gasoline), the market value of a crude oil generally rises with increasing yields of light products.
- The Editors of Encyclopaedia Britannica
Crude oil, or petroleum, is formed through a natural processes called diagenesis and catagenesis that take millions of years. As ancient plants, bacteria, algae, and other small animals and organisms (or diatoms) that lived in the oceans millions and millions of years ago died, they settled down on the ocean floor.
How is crude oil found and produced? The search for crude oil begins with geologists who study the structure and history of rock layers below the earth's surface to locate areas that may contain deposits of oil and natural gas.
2023年10月19日 · Today, petroleum is found in vast underground reservoirs where ancient seas were located. Petroleum reservoirs can be found beneath land or the ocean floor. Their crude oil is extracted with giant drilling machines. Crude oil is usually black or dark brown, but can also be yellowish, reddish, tan, or even greenish.
5 天前 · Petroleum, complex mixture of hydrocarbons that occur in Earth in liquid, gaseous, or solid form. The term is often restricted to the liquid form, commonly called crude oil, but, as a technical term, ‘petroleum’ also refers to natural gas and the viscous or solid form known as bitumen, which is found in tar sands.
