Publications

Survey of Energy Resources 2007

Definitions

Crude oil is a naturally occurring mixture consisting predominantly of hydrocarbons that exists in liquid phase in natural underground reservoirs and is recoverable as liquids at typical atmospheric conditions of pressure and temperature. Crude oil has a viscosity no greater than 10 000 mPa.s (centipoises) at original reservoir conditions; oils of greater viscosity are included in Chapter 4 - Natural Bitumen and Extra-Heavy Oil.

Natural gas liquids (NGLs) are hydrocarbons that exist in the reservoir as constituents of natural gas but which are recovered as liquids in separators, field facilities or gas-processing plants. Natural gas liquids include (but are not limited to) ethane, propane, butanes, pentanes, natural gasoline and condensate; they may include small quantities of non-hydrocarbons.

If reserves/resources/production/consumption of NGLs exist but cannot be separately quantified, they are included (as far as possible) under crude oil.

In the tables the following definitions apply to both crude oil and natural gas liquids:
Proved amount in place is the resource remaining in known natural reservoirs that has been carefully measured and assessed as exploitable under present and expected local economic conditions with existing available technology.
Proved recoverable reserves are the quantity within the proved amount in place that can be recovered in the future under present and expected local economic conditions with existing available technology.

Estimated additional amount in place is the resource additional to the proved amount in place that is of foreseeable economic interest. Speculative amounts are not included.

Estimated additional reserves recoverable is the quantity within the estimated additional amount in place that geological and engineering information indicates with reasonable certainty might be recovered in the future.

R/P (reserves/production) ratio is calculated by dividing the volume of proved recoverable reserves at the end of 2005 by volumetric production in that year. The resulting figure is the time in years that the proved recoverable reserves would last if production were to continue at the 2005 level.

NOTE:
The quantifications of reserves and resources presented in the tables that follow incorporate, as far as possible, data reported by WEC Member Committees. Such data will reflect the respective Member Committees' interpretation of the above Definitions in the context of the reserves/resources information available to them, and the degree to which particular countries' terminology and statistical conventions are compatible with the WEC specifications.