The oil industry is littered with jargon which is possibly why it is so difficult for the ordinary man and woman to understand it. Since the oil companies seem to want to keep quiet about peak oil (assumedly so as not to effect their share prices), they probably are happy to use such terms. On this page are some definitions which you will need.
You would think that a simple term like oil would be straightforward enough. Unfortunately not.
Crude oil (or petroleum) is one form of a substance known as hydrocarbons that form part of what we call ‘fossil fuels’. The other hydrocarbon is natural gas. Coal is not usually considered a hydrocarbon. Oil itself comes in different forms with consistencies from liquid to nearly solid.
Regular or Conventional Oil
Conventional oil is generally defined as oil which is produced by primary or secondary recovery methods. These methods are from its own pressure, physical lift, water flooding, and pressure from water or natural gas. Generally refers to free flowing oil so excludes tar sands, heavy oil, deepwater, polar and NGL. This accounts for about 95% of all oil production.
Bitumen: generally means hydrocarbons in a solid or semi-solid state. Principally the tar sands of Canada, defined by viscosity, from which synthetic oil is made.
Coal and Gas Conversion: oil produced from the conversion of coal or gas to oil.
Deepwater Oil: oil below 500m in depth of water. Defined differently from regular oil because of its significantly different geology, operating conditions and the state of knowledge regarding it.
Extra Heavy Oil: oil less than 10ºAPI. Production is controlled by its extraction rate rather than the resource base. Mainly in Venezuela and Canada.
Gas Condensates: hydrocarbon liquid dissolved in saturated natural gas that comes out of solution when the pressure drops below the dew point.
Heavy Oil: oil less than 17.5ºAPI but greater than 10º API (“Extra Heavy Oil”). Production is controlled by its extraction rate rather than the resource base.
NGL (Natural Gas Liquid): hydrocarbons that exist in fields as constituents of natural gas but which are recovered separately as liquids. Natural gas liquids include propane, butane, pentane, hexane and heptane, but not methane and ethane, since these hydrocarbons need refrigeration to be liquefied.
Oil Shale: a petroleum source rock that has never been converted to oil. It can be converted to liquid oil by mining, crushing and heating.
Polar Oil: defined differently from regular oil because of its significantly different geology, operating conditions and the state of knowledge regarding it.
Tar Sands (Oil Sands): an oil field which has been exposed at the surface so that only a nearly solid tar is left. It can be converted to liquid oil by mining, heating and separation.
- API (Gravity): a measure of oil density. By definition, the API Gravity of fresh water is 10. Higher API Gravities correspond to lower-density (ie.'lighter') liquids.
This is the first stage of oil or gas production when the natural pressure of gas or water inside the reservoir forces the hydrocarbons to the surface naturally. As the pressure drops, it is necessary to bring in pumps such as the 'nodding donkeys' to assist but this is still classed as primary production. Only about 10-20% of the source is produced in this stage and it ends when the production rates are too low to be economical or the amount of gas or water in the output is too high.
Here an external fluid such as water or gas is injected into the reservoir to create an artificial pressure, enough to drive the hydrocarbons to the surface. 15-40% of the source can be produced by secondary recovery and it ends when too much of the injected fluid is being returned at the well head.
In the last stage, sophisticated techniques are used to increase pressure and improve fluid flow. These involve altering the original properties of the gas or oil. The three main methods are chemical flooding, CO2/hydrocarbon injection, and thermal recovery (steam-flooding or combustion). 5-15% may be recovered using tertiary production. Tertiary recovery is also known as "Enhanced Oil Recovery" (EOR).
The chart above shows the amount of oil each form of recovery is likely to extract from a reservoir. It shows that, even at the very (unlikely) best, 20% of the oil will remain in the ground. Usually you could not expect to get more than about 60% from a field.