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The world’s 932 giant oil and gas fields are considered those with 500 million barrels of ultimately recoverable oil or gas equivalent. Geoscientists believe these giants account for 40 percent of the world’s petroleum reserves. They are clustered in 27 regions of the world, with the largest clusters in the Persian Gulf and Western Siberian Basin. The past three decades reflect declines in discoveries of giant fields. The present decade (2000-2010), however, reflects an upturn in discoveries and appears on track to be the third best for discovery of giant oil and gas fields in the 150 year history of modern oil and gas exploration.

According to analysis led by Paul Mann of the University of Texas’ Jackson School of Geosciences, almost all of the 932 giant oil and gas fields cluster within 27 regions, or about 30 percent of Earth’s land surface. Since 2003, Mann and colleagues M.K. Horn and Ian Cross have tracked the giants on a map that highlights the tectonic and sedimentary basin maps of the 27 key regions. The map is in the public domain and available as a high-resolution pdf on the Web site of the Jackson School of Geosciences. Read more »

Petroleum is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds.

Composition

The proportion of hydrocarbons in the mixture is highly variable and ranges from as much as 97% by weight in the lighter oils to as little as 50% in the heavier oils and bitumens.

The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium. The exact molecular composition varies widely from formation to formation but the proportion of chemical elements vary over fairly narrow limits as follows: Read more »

An oil is a substance that is in a viscous liquid state (“oily”) at ambient temperatures or slightly warmer, and is both hydrophobic, (immiscible with water) and lipophilic (miscible with other oils, literally). This general definition includes compound classes with otherwise unrelated chemical structures, properties, and uses, including vegetable oils, petrochemical oils, and volatile essential oils. Oil is a nonpolar substance.

Etymology

Oil is a colloquial term used to refer to certain diverse and unrelated compounds sharing the same physical properties (such as viscosity and a hydrophobic nature), while ignoring related compounds. The compounds found in cooking oil are chemically very similar, almost identical, to those found in butter and very different from those found in diesel fuel, but while diesel is an oil, butter is not. Indeed diesel is once again very similar to natural gas, but gas is certainly not oil. This disparity stems partly from the fact that oils must be liquid at room temperature, and thus only certain liquid chemicals in many unrelated families are recognised, collectively, as ‘oil’. Scientists, instead of using the term ‘oil’, adopt the terms lipids and other terms to denote them instead. Read more »