Survey of Energy Resources 2007
Natural Bitumen - Definitions
In this chapter the following definitions apply:
Discovered original oil in place: the volume of oil (natural bitumen/extra-heavy oil) in place reported for deposits or parts of deposits that have been measured by field observation. In the literature, estimates of the in-place volumes are often derived from the physical measures of the deposit; areal extent, rock grade, and formation thickness.
Prospective additional original oil in place: the oil in unmeasured parts of a deposit believed to be present as a result of inference from geological (and often geophysical) study.
Original oil in place: the amount of oil in a deposit before any exploitation has taken place. Where original oil in place is not reported, it is most often calculated from reported data on original reserves (cumulative production plus reserves). Although admittedly inexact, this is a reasonable way to describe the relative abundance of the natural bitumen or extra-heavy oil.
Original reserves: reserves plus cumulative production. This category includes oil that is frequently reported as estimated ultimate recovery, particularly in the case of new discoveries.
Cumulative production: total of production to latest date.
Reserves: those amounts of oil commonly reported as reserves or probable reserves, generally with no further distinction, are quantities that are anticipated to be technically (but not necessarily commercially) recoverable from known accumulations. Only in Canada are reserves reported separately as recoverable by primary or enhanced methods. Russian A, B, and C1 reserves are included here. The term reserve, as used here, has no economic connotation.
Coking: a thermal cracking process that converts the heavy fraction of residue or heavy oils to elemental carbon (coke) and to lighter fractions of the residue, including naphtha or heavy gas oils.
Conventional oil: oil with an API gravity of greater than 20° (density below 0.934 g/cm3). API gravity is the inverse of density and is computed as (141.5/sp g)-131.5 where sp g is the specific gravity of oil at 60 degrees Fahrenheit.
Cracking: a general term used for a process in which relatively heavy hydrocarbons are broken down into smaller, lower-boiling molecules.
Delayed coking: a coking process that recovers coke and produces heavy gas oils from the residuum following the initial distillation of the feedstock oil. The process uses at least two sets of large drums that are alternatively filled and emptied while the rest of the plant operates continuously. Drum temperatures are 415° to 450°C.
Extra-heavy oil: extra-heavy oil is commonly defined as oil having a gravity of less than 10° and a reservoir viscosity of no more than 10 000 centipoises. In this chapter, when reservoir viscosity measurements are not available, extra-heavy oil is considered to have a lower limit of 4° API.
Flexi-coking: an extension of fluid coking, which includes the gasification of the coke produced in the fluid coking operation and produces a coke gas (Speight, 1986). Flexi-coking is an ExxonMobil proprietary process.
Fluid Coking: a continuous coking process where residuum is sprayed onto a fluidised bed of hot coke particles. The residuum is cracked at high temperatures into lighter products and coke. Coke is a product and a heat carrier. The process occurs at much higher temperatures than delayed coking but leads to lower coke yields and greater higher liquid recovery. Temperatures in the coking vessels are from 480° to 565°C (Speight, 1986). Fluid coking is an ExxonMobil proprietary process.
Gas oil: hydrocarbon mixture of gas and oils that form as product of initial distillation of bitumen or heavy oil feedstock.
Heavy oil: Oil with API gravity from 10° to 20° inclusive (density above 1.000 g/cm3).
Hydrocracking: a catalytic cracking process that occurs in the presence of hydrogen where the extra hydrogen saturates or hydrogenates the cracked hydrocarbons.
Natural bitumen: natural bitumen is defined as oil having a viscosity greater than 10 000 centipoises under reservoir conditions and an API gravity of less than 10°API. In this chapter, when reservoir viscosity measurements are not available, natural bitumen is taken as having a gravity of less than 4°. (Natural bitumen is immobile in the reservoir. Because of lateral variations in chemistry as well as in depth, and therefore temperature, many reservoirs contain both extra-heavy oil, and occasionally heavy oil, in addition to natural bitumen).
Oil Field: a geographic area below which are one or more discrete reservoirs from which petroleum is produced. Each reservoir may be comprised of one or more zones, the production from which is commingled. The production from the reservoirs may be commingled, in which case production and related data cannot be distinguished.