Petroleum (
Latin Petroleum derived from
Greek πέτρα (Latin
petra) - rock + έλαιον (Latin
oleum) - oil) or
crude oil is a naturally occurring liquid found in formations in the
Earth consisting of a complex mixture of
hydrocarbons (mostly
alkanes) of various lengths. The approximate length range is C
5H
12 to C
18H
38. Any shorter hydrocarbons are considered
natural gas or
natural gas liquids, while long-chain hydrocarbons are more viscous, and the longest chains are
paraffin wax. In its naturally occurring form, it may contain other nonmetallic elements such as
sulfur,
oxygen, and
nitrogen. It is usually black or dark brown (although it may be yellowish or even greenish) but varies greatly in appearance, depending on its composition. Crude oil may also be found in semi-solid form mixed with sand, as in the
Athabasca oil sands in
Canada, where it may be referred to as crude
bitumen.
Petroleum is used mostly, by volume, for producing
fuel oil and
gasoline (
petrol), both important "
primary energy" sources.
84% by volume of the hydrocarbons present in petroleum is converted into energy-rich fuels (petroleum-based fuels), including gasoline, diesel, jet, heating, and other fuel oils, and
liquefied petroleum gas.
Due to its high
energy density, easy
transportability and
relative abundance, it has become the world's most important source of energy since the mid-1950s. Petroleum is also the raw material for many
chemical products, including
pharmaceuticals,
solvents,
fertilizers,
pesticides, and
plastics; the 16% not used for energy production is converted into these other materials.
Petroleum is found in
porous rock formations in the upper
strata of some areas of the
Earth's
crust. There is also petroleum in
oil sands (tar sands). Known
reserves of petroleum are typically estimated at around 1.2 trillion barrels without oil sands
, or 3.74 trillion barrels with oil sands
. However, oil production from oil sands is currently severely limited. Consumption is currently around 84 million barrels per day, or 3.6 trillion liters per year. Because of
reservoir engineering difficulties, recoverable oil reserves are significantly less than total oil-in-place. At current consumption levels, and assuming that oil will be consumed only from reservoirs, known reserves would be gone around 2039, potentially leading to a global
energy crisis. However, this ignores any new discoveries, rapidly increasing consumption in China & India, using oil sands, using synthetic petroleum, and other factors which may extend or reduce this estimate.
Formation
Chemistry
The chemical structure of petroleum is composed of
hydrocarbon chains of different lengths. These different hydrocarbon chemicals are separated by
distillation at an oil refinery to produce gasoline, jet fuel, kerosene, and other hydrocarbons. The general formula for these
alkanes is
CnH2n+2. For example
2,2,4-trimethylpentane (isooctane), widely used in
gasoline, has a chemical formula of C
8H
18 and it reacts with oxygen
exothermically:
»
Formation of petroleum occurs in a variety of mostly
endothermic reactions in high temperature and/or pressure. For example, a
kerogen may break down into
hydrocarbons of different lengths.
Biogenic theory
Most
geologists view crude oil and
natural gas as the product of
compression and heating of ancient
organic materials over
geological time. Oil is formed from the preserved remains of
prehistoric zooplankton and
algae which have been settled to the sea (or lake) bottom in large quantities under
anoxic conditions.
Terrestrial plants, on the other hand, tend to form
coal. Over
geological time this
organic matter, mixed with
mud, is buried under heavy layers of sediment. The resulting high levels of
heat and
pressure cause the organic matter to chemically change during
diagenesis, first into a waxy material known as
kerogen which is found in various
oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as
catagenesis.
Geologists often refer to an "oil window" which is the temperature range that oil forms in—below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to
natural gas through the process of
thermal cracking. Though this happens at different depths in different locations around the world, a 'typical' depth for the oil window might be 4–6 km. Note that even if oil is formed at extreme depths, it may be trapped at much shallower depths, even if it isn't formed there (the Athabasca Oil Sands is one example).
Because most hydrocarbons are
lighter than rock or water, these often migrate upward through adjacent rock layers until they they either reach the surface or become trapped beneath impermeable rocks, within porous rocks called
reservoirs. However, the process isn't straightforward since it's influenced by underground water flows, and oil may migrate hundreds of kilometres horizontally or even short distances downward before becoming trapped in a reservoir. Concentration of hydrocarbons in a trap forms an
oil field, from which the liquid can be extracted by
drilling and
pumping.
Three conditions must be present for oil reservoirs to form: first, a source rock rich in organic material buried deep enough for subterranean heat to cook it into oil; second, a
porous and
permeable reservoir rock for it to accumulate in; and last a cap rock (seal) or other mechanism that prevents it from escaping to the surface. Within these reservoirs fluids will typically organize themselves like a three-layer cake with with a layer of water below the oil layer and a layer of gas above it, although the different layers vary in size between reservoirs.
The vast majority of oil that has been produced by the earth has long ago escaped to the surface and been
biodegraded by oil-eating bacteria. Oil companies are looking for the small fraction that has been trapped by this rare combination of circumstances. Oil sands are reservoirs of partially biodegraded oil still in the process of escaping, but contain so much migrating oil that, although most of it has escaped, vast amounts are still present - more than can be found in conventional oil reservoirs. On the other hand, oil shales are source rocks that have never been buried deep enough to convert their trapped kerogen into oil.
The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where kerogen is broken down to oil and natural gas by a set of parallel reactions, and oil eventually breaks down to natural gas by another set of reactions. The first set was originally patented in 1694 under British Crown Patent No. 330 covering,
"a way to extract and make great quantityes of pitch, tarr, and oyle out of a sort of stone."
The latter set is regularly used in
petrochemical plants and
oil refineries.
Abiogenic theory
The idea of
abiogenic petroleum origin was championed in the
Western world by astronomer
Thomas Gold based on thoughts from
Russia, mainly on studies of
Nikolai Kudryavtsev. The idea proposes that hydrocarbons of purely geological origin exist in the
planet. Hydrocarbons are less dense than aqueous pore fluids, and are proposed to migrate upward through deep fracture networks.
Thermophilic, rock-dwelling
microbial life-forms are proposed to be in part responsible for the
biomarkers found in petroleum.
This theory is a minority opinion, especially amongst Western geologists; no Western oil companies are currently known to explore for oil based on this theory, although Russia is known to have applied this theory with some success.
Classification
The
oil industry classifies "crude" by the location of its origin (for example, "West Texas Intermediate, WTI" or "Brent") and often by its
relative weight or
viscosity ("
light", "intermediate" or "
heavy"); refiners may also refer to it as "
sweet," which means it contains relatively little
sulfur, or as "
sour," which means it contains substantial amounts of
sulfur and requires more refining in order to meet current product specifications. Each crude oil has unique molecular characteristics which are understood by the use of
crude oil assay analysis in petroleum laboratories.
Barrels from an area in which the crude oil's molecular characteristics have been determined and the oil has been classified are used as pricing
references throughout the world. These references are known as Crude oil benchmarks:
Means of production
Extraction
The most common method of obtaining petroleum is extracting it from
oil wells found in
oil fields. With improved technologies and higher demand for hydrocarbons various methods are applied in petroleum exploration and development to optimize the recovery of oil and gas. Primary recovery methods are used to extract oil that's brought to the surface by underground pressure, and can generally recover about 20% of the oil present. The natural pressure can come from several different sources; where it's provided by an underlying water layer it's called a
water drive reservoir and where it's from the gas cap above it's called
gas drive. After the reservoir pressure has depleted to the point that the oil is no longer brought to the surface, secondary recovery methods draw another 5 to 10% of the oil in the well to the surface. In a water drive oil field, water can be injected into the water layer below the oil, and in a gas drive field it can be injected into the gas cap above to repressurize the reservoir. Finally, when secondary oil recovery methods are no longer viable, tertiary recovery methods reduce the
viscosity of the oil in order to bring more to the surface. These generally involve the injection of heat and/or solvents.
Alternative methods
During the last
oil price peak, other alternatives to producing oil gained importance. The best known such methods involve extracting oil from sources such as oil shale or tar sands. These resources are known to exist in large quantities; however, extracting the oil at low cost without negatively impacting the environment remains a challenge.
It is also possible to transform
natural gas or
coal into oil (or, more precisely, the various hydrocarbons found in oil). The best-known such method is the
Fischer-Tropsch process. It was a concept pioneered in
Nazi Germany when
imports of petroleum were restricted due to war and
Germany found a method to extract oil from coal. It was known as
Ersatz ("substitute" in
German), and accounted for nearly half the total oil used in
WWII by Germany. However, the process was used only as a last resort as naturally occurring oil was much cheaper. As crude oil prices increase, the cost of coal to oil conversion becomes comparatively cheaper. The method involves converting high ash coal into
synthetic oil in a multi-stage process. Ideally, a
ton of coal produces nearly 200
liters (1.25 bbl, 52 US gallons) of crude, with
by-products ranging from tar to
rare chemicals.
Currently, two companies have commercialised their Fischer-Tropsch technology. Shell in
Bintulu,
Malaysia, uses
natural gas as a
feedstock, and produces primarily low-
sulfur diesel fuels.
Sasol
in
South Africa uses coal as a feedstock, and produces a variety of synthetic petroleum products.
The process is today used in
South Africa to produce most of the country's
diesel fuel from coal by the company
Sasol. The process was used in South Africa to meet its energy needs during its isolation under
Apartheid. This process has received renewed attention in the quest to produce low
sulfur diesel fuel in order to minimize
the environmental impact from the use of diesel
engines.
An alternative method of converting coal into petroleum is the
Karrick process, which was pioneered in the 1930s in the
United States. It uses high temperatures in the absence of ambient air, to
distill the short-chain hydrocarbons of petroleum out of coal.
More recently explored is
thermal depolymerization (TDP), a process for the reduction of complex
organic materials into light
crude oil. Using pressure and heat, long chain
polymers of
hydrogen,
oxygen, and
carbon decompose into short-chain petroleum
hydrocarbons. This mimics the natural
geological processes thought to be involved in the production of
fossil fuels. In theory, TDP can convert any organic waste into petroleum.
History
Petroleum, in some form or other, isn't a substance new in the world's history. More than four thousand years ago, according to
Herodotus and confirmed by
Diodorus Siculus,
asphalt was employed in the construction of the walls and towers of
Babylon; there were oil pits near Ardericca (near Babylon), and a pitch spring on
Zacynthus. Great quantities of it were found on the banks of the river
Issus, one of the tributaries of the
Euphrates. Ancient
Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society.
The earliest known
oil wells were drilled in
China in
347 CE or earlier. They had depths of up to about and were drilled using
bits attached to
bamboo poles. The oil was burned to evaporate
brine and produce
salt. By the 10th century, extensive
bamboo pipelines connected oil wells with salt springs. The ancient records of China and Japan are said to contain many allusions to the use of natural gas for lighting and heating. Petroleum was known as
burning water in Japan in the 7th century.
(See also: Alchemy (Islam), Islamic science, and Timeline of science and technology in the Islamic world.)
The earliest mention of American petroleum occurs in
Sir Walter Raleigh's account of the
Trinidad Pitch Lake in 1595; whilst thirty-seven years later, the account of a visit of a Franciscan, Joseph de la Roche d'Allion, to the oil springs of New York was published in Sagard's
Histoire du Canada. A Russian traveller, Peter Kalm, in his work on America published in 1748 showed on a map the oil springs of Pennsylvania.
The Pechelbronn oil field was active until 1970, and was the birth place of companies like
Antar and
Schlumberger. The first modern refinery was built there in 1857.
But at the same time,
offshore oil platforms also form micro-habitats for marine creatures. Extraction may involve
dredging, which the
seabed,
killing the sea plants that marine creatures need to survive.
Oil spills
Crude oil and refined fuel
spills from
tanker ship accidents have damaged natural
ecosystems in
Alaska, the
Galapagos Islands,
France and many
other places and times in
Spain (for example
Ibiza).
The quantity of oil spilled during accidents has ranged from a few hundred tons to several hundred thousand tons (
Atlantic Empress,
Amoco Cadiz...). Smaller spills have already proven to have a great impact on ecosystems, such as the
Exxon Valdez oil spill
Global warming
Burning oil releases carbon dioxide into the atmosphere, which contributes to
global warming. Per energy unit, oil produces less
CO2 than coal, but more than natural gas. However, oil's unique role as a
transportation fuel makes reducing its CO
2 emissions a particularly thorny problem; amelioration strategies such as
carbon sequestering are generally geared for large
power plants, not individual vehicles.
Whales
It has been argued that the advent of kerosene was one development, which saved the great cetaceans from extinction.
Alternatives to petroleum
Alternatives to petroleum-based vehicle fuels
The term alternative propulsion or "alternative methods of propulsion" includes both:
alternative fuels used in standard or modified internal combustion engines (for example combustion hydrogen or biofuels).
propulsion systems not based on internal combustion, such as those based on electricity (for example, all-electric or hybrid vehicles), compressed air, or fuel cells (for example hydrogen fuel cells).
Nowadays, cars can be classified between the next main groups:
Petro-cars, this is, only use petroleum and biofuels (biodiesel and biobutanol).
Hybrid vehicle and plug-in hybrids, that use petroleum and other source, generally, electricity.
Petrofree car, that can not use petroleum, like electric cars, hydrogen vehicles...
The future of petroleum production
Hubbert peak theory
The Hubbert peak theory (also known as peak oil) is a proposition which predicts that future world petroleum production must inevitably reach a peak and then decline at a similar rate to the rate of increase before the peak as these reserves are exhausted. It also suggests a method to calculate mathematically the timing of this peak, based on past production rates, past discovery rates, and proven oil reserves.
Controversy surrounds the theory for numerous reasons. Past predictions regarding the timing of the global peak have failed, causing a number of observers to disregard the theory. Further, predictions regarding the timing of the peak are highly dependent on the past production and discovery data used in the calculation.
Proponents of peak oil theory also refer as an example of their theory, that when any given oil well produces oil in similar volumes to the amount of water used to obtain the oil, it tends to produce less oil afterwards, leading to the relatively quick exhaustion and/or commercial inviability of the well in question.
The issue can be considered from the point of view of individual regions or of the world as a whole. Hubbert's prediction for when US oil production would peak turned out to be correct, and after this occurred in 1971 - causing the US to lose its excess production capacity - OPEC was finally able to manipulate oil prices, which led to the 1973 oil crisis. Since then, most other countries have also peaked: the United Kingdom's North Sea, for example in the late 1990s. China has confirmed that two of its largest producing regions are in decline, and Mexico's national oil company, Pemex, has announced that Cantarell Field, one of the world's largest offshore fields, was expected to peak in 2006, and then decline 14% per annum.
It is difficult to predict the oil peak in any given region (due to the lack of transparency in accounting of global oil reserves
)
. Based on available production data, proponents have previously (and incorrectly) predicted the peak for the world to be in years 1989, 1995, or 1995-2000. Some of these predictions date from before the recession of the early 1980s, and the consequent reduction in global consumption, the effect of which was to delay the date of any peak by several years. A new prediction by Goldman Sachs picks 2007 for oil and some time later for natural gas. Just as the 1971 U.S. peak in oil production was only clearly recognized after the fact, a peak in world production will be difficult to discern until production clearly drops off.
Many proponents of the Hubbert peak theory expound the belief that the production peak is imminent, for various reasons. The year 2005 saw a dramatic fall in announced new oil projects coming to production from 2008 onwards - in order to avoid the peak, these new projects would have to not only make up for the depletion of current fields, but increase total production annually to meet increasing demand.
The year 2005 also saw substantial increases in oil prices due to a number of circumstances, including war and political instability. Oil prices rose to new highs. Analysts such as Kenneth Deffeyes
argue that these price increases indicate a general lack of spare capacity, and the price fluctuations can be interpreted as a sign that peak oil is imminent.
Pricing
International market
Petroleum efficiency among countries
There are two main ways to measure the petroleum efficiency of countries: by population or by GDP (gross domestic product). This metric is important in the global debate over oil consumption/energy consumption/climate change because it takes social and economic considerations into account when scoring countries on their oil consumption/energy consumption/climate change goals. Nations such as China and India with large populations tend to promote the use of population based metrics, while nations with large economies such as the United States would tend to promote the GDP based metric.
| Selected Nations |
Oil Efficiency (US dollar/barrel/day) |
|
3.75 |
|
3.34 |
|
3.31 |
|
2.96 |
|
2.65 |
|
2.89 |
|
2.71 |
|
2.57 |
|
2.52 |
|
2.4 |
|
2.34 |
|
2.21 |
|
1.96 |
|
1.93 |
|
1.87 |
|
1.65 |
|
1.59 |
|
1.47 |
|
1.39 |
|
1.35 |
|
1.07 |
|
1.04 |
|
1.00 |
|
1.00 |
|
0.99 |
|
0.98 |
|
0.94 |
|
0.94 |
|
0.93 |
|
0.89 |
|
0.86 |
|
0.84 |
|
0.71 |
|
0.61 |
|
0.53 |
|
0.46 |
|
0.41 |
|
0.40 |
|
0.35 |
| Selected Nations |
Oil Efficiency (barrel/person/year) |
|
0.13 |
|
0.37 |
|
0.57 |
|
0.73 |
|
1.95 |
|
2.17 |
|
2.18 |
|
2.70 |
|
3.77 |
|
4.63 |
|
4.96 |
|
7.48 |
|
9.85 |
|
11.67 |
|
11.67 |
|
12.55 |
|
13.86 |
|
17.66 |
|
18.07 |
|
21.56 |
|
29.70 |
|
30.18 |
|
32.31 |
|
32.43 |
|
32.43 |
|
34.01 |
|
35.18 |
|
34.64 |
|
34.68 |
|
41.68 |
|
42.01 |
|
42.22 |
|
43.84 |
|
52.06 |
|
61.52 |
|
68.81 |
|
69.85 |
|
75.08 |
|
178.45 |
(Note: The figure for Singapore is skewed because of its small
population compared with its large oil refining capacity.
Most of this oil is sent to other countries.)
Top petroleum-producing countries
Source: Energy Statistics from the U.S. Government
.
For oil reserves by country, see Oil reserves by country.
In order of amount produced in 2004 in MMbbl/d & ML/d:
| # |
Producing Nation for 2004 |
(×106bbl/d) |
(×10³m³/d) |
| 1 |
|
10.37 |
1,649 |
| 2 |
|
9.27 |
1,474 |
| 3 |
|
8.69 |
1,382 |
| 4 |
|
4.09 |
650 |
| 5 |
|
3.83 |
609 |
| 6 |
|
3.62 |
576 |
| 7 |
|
3.18 |
506 |
| 8 |
|
3.14 |
499 |
| 9 |
|
2.86 |
455 |
| 10 |
|
2.76 |
439 |
| 11 |
|
2.51 |
399 |
| 12 |
|
2.51 |
399 |
| 13 |
|
2.08 |
331 |
| 14 |
|
2.03 |
323 |
1 peak production of conventional oil already passed in this state
² Though still a member, Iraq hasn't been included in production figures since 1998
³ Canada has the world's second largest oil reserves when tar sands are included, and is the leading source of U.S. imports, averaging 1.7 MMbbl/d in April 2006 (External Link).
Top petroleum-exporting countries
In order of amount exported in 2003:
Saudi Arabia (OPEC)
Russia
Norway 1
Iran (OPEC)
United Arab Emirates (OPEC)
Venezuela (OPEC) 1
Kuwait (OPEC)
Nigeria (OPEC)
Mexico 1
Algeria (OPEC)
Libya (OPEC) 1
1 peak production already passed in this state
Note that the USA consumes almost all of its own production, while the UK has recently become a net-importer rather than net-exporter.
Total world production/consumption (as of 2005) is approximately 84 million barrels per day.
See also: Organization of Petroleum Exporting Countries.
Top petroleum-consuming countries
| # |
Consuming Nation |
(bbl/day) |
(m³/day) |
| 1 |
|
20,030,000 |
3,184,516 |
| 2 |
|
6,391,000 |
1,016,088 |
| 3 |
|
5,578,000 |
886,831 |
| 4 |
|
2,800,000 |
445,164 |
| 5 |
|
2,677,000 |
425,609 |
| 6 |
|
2,320,000 |
368,851 |
| 7 |
|
2,300,000 |
365,671 |
| 8 |
|
2,061,000 |
327,673 |
| 9 |
|
2,060,000 |
327,514 |
| 10 |
|
1,874,000 |
297,942 |
| 11 |
|
1,775,000 |
282,202 |
| 12 |
|
1,752,000 |
278,546 |
| 13 |
|
1,722,000 |
273,776 |
| 14 |
|
1,610,000 |
255,970 |
Source: CIA World Factbook
Top petroleum-importing countries
| # |
Importing Nation |
(bbl/day) |
(m³/day) |
| 1 |
|
13,150,000 |
2,790,683 |
| 2 |
|
5,449,000 |
866,322 |
| 3 |
|
3,226,000 |
512,893 |
| 4 |
|
2,284,000 |
363,127 |
| 5 |
|
2,281,000 |
362,650 |
| 6 |
|
2,263,000 |
359,788 |
| 7 |
|
2,158,000 |
343,095 |
| 8 |
|
2,135,000 |
339,438 |
| 9 |
|
2,090,000 |
332,283 |
| 10 |
|
1,582,000 |
251,518 |
| 11 |
|
1,084,000 |
172,342 |
| 12 |
|
1,042,000 |
165,665 |
| 13 |
|
963,000 |
153,105 |
| 14 |
|
616,500 |
98,016 |
Source: CIA World Factbook
Top petroleum non-producing and consuming countries
| # |
Consuming Nation |
(bbl/day) |
(m³/day) |
| 1 |
|
5,578,000 |
886,831 |
| 2 |
|
2,677,000 |
425,609 |
| 3 |
|
2,320,000 |
368,851 |
| 4 |
|
2,061,000 |
327,673 |
| 5 |
|
2,060,000 |
327,514 |
| 6 |
|
1,874,000 |
297,942 |
| 7 |
|
1,537,000 |
244,363 |
| 8 |
|
946,700 |
150,513 |
Source : CIA World Factbook
Writers covering the petroleum industry
Brian Black
Colin J. Campbell
Kenneth S. Deffeyes
Thomas Gold
David Goodstein
Jay Hanson
Daniel Yergin
Derrick Jensen
External results
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