The cumulative production is the sum of all oil that has ever been produced until a specific date. Cumulative production can be given for a field, oil basin, country or the world.
The decline rate refers to production only. It is defined as the negative relative change of production over a time period. Often a period of a year is used. The decline rate can be expressed as a fraction or as percent.
Assume a production of 1 Gb in year 2000 and 0.95 Gb in year 2001. The decline rate for year 2001 would then be (1 – 0.95)/1 = 0.05 = 5%. If the production is rising, the decline rate becomes negative.
The amount of oil left is calculated by taking the URR minus last year’s cumulative production. The depletion rate depends on the estimated amount of oil left. As more oil is produced, less oil is left. At a constant production the depletion rate grows while the decline rate is zero. The depletion rate can never become negative.
A large geological area in which sedimentation is occurring or has occurred. Certain parts of the basin might therefore have the required geological conditions to trap oil. Consists of many oil fields.
In context of oil production, the definition from BP Statistical Review (B.4) is used: crude oil, shale oil, oil sands and NGLs (natural gas liquids – the liquid content of natural gas where this is recovered separately).
In context of oil consumption, the definition from World Energy Outlook (A.6) is used: crude oil, condensates, natural gas liquids, refinery feedstocks and additives, other hydrocarbons and petroleum products (refinery gas, ethane, LPG, aviation gasoline, motor gasoline, jet fuels, kerosene, gas/diesel oil, heavy fuel oil, naphtha, white spirit, lubricants, bitumen, paraffin waxes, petroleum coke and other petroleum products).
A subsurface porous and permeable rock body that contains oil, gas or both.
An area consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the same individual geological structural feature or stratigraphic condition.
The recoverable reserves are an estimate of how much recoverable oil is still left in the already found oil fields. It can only be an estimate since it’s impossible to know exactly how much oil is still in the ground.
Because of this uncertainty, reserves are calculated with a certain probability. A reserve estimate followed with, for instance, ‘P90’ means that there is a 90% chance that there is at least as much recoverable oil as the reserve estimate claims.
A wildcat is an exploration borehole drilled when searching for oil or gas.
Yet-to-find is an estimate of the amount of recoverable oil that exists in fields that have not yet been found.
Previous Story Previous post: What is Peak Oil?