Over the years a variety of terms have been used to describe the hydrocarbon resource which is the subject of this paper. To reduce potential misunderstandings, the double noun "bitumen sands" will be used in this paper to describe the combined hydrocarbon and clastic sediment host rocks which are the potential source of synthetic crude oil and other by-products (sulphur, heavy minerals) of interest. Hence, the term bitumen applies to the in-place resource and raw, extracted hydrocarbon, whereas, synthetic crude oil applies to the upgraded material of which bitumen is the main input component.
At the Energy Resources Conservation Board (ERCS), crude bitumen is defined as:
A naturally occurring viscous mixture, mainly of hydrocarbons heavier than pentane, that may contain sulphur compounds, and that in its naturally occurring viscous state is not recoverable at a commercial rate through a well;
Typically it contains 4. 5 mass per cent sulphur, has a density range of 980 to 1030 kg/m3 depending on region of occurrence, and may contain small amounts of dissolved methane and traces of hydrogen sulphide.
As a hydrocarbon material, bitumen is also notable for a deficiency of hydrogen in relation to carbon, it being more or less mid-way between that of a mediumcrude oil (13 mass per cent hydrogen) and a sub bituminous coal (6 mass per cent hydrogen). Hence, upgrading technologies contemplate either hydrocracking (hydrogen addition) or coking (carbon reduction) as a means of converting the bitumen to asynthetic crude oil similar in properties to natural light/medium crudes.
Though bitumen is believed to be closely related, in the sense of geological origin, to the widespread Cretaceous heavy oils (960 to 910 kg/m3) of the Western Canada sedimentary basin (3), a most distinguishing characteristic is that of viscosity (Figure 1). The bitumen occurrences of Alberta exhibit extremely high viscosity to the point of pseudoplasticity with natural viscosities in the range l05 to 10 6 mPa.S (105 to 106 centipoises). (By comparison the heavy oils usually exhibit viscosities in the range 102 to 103 mPa.s (102 to 103 centipoises) at reservoir conditions.)
A wealth of technical information concerning the natural bitumen resources in Alberta has been developed, led in 1882 by the work of Dr. Robert Bell of the Geological and Natural History Survey of Canada and other of his colleagues, and particularly during this century by experts at the Alberta Research Council anda variety of industrial experts. This library of information thoroughly portrays the extent and characteristics of the bitumen accumulations ofnorthern Alberta (1, 2, 3, 4, 5, 6). The discourse which follows, therefore, is intended to provide onlyan overview and update of the extent of the occurrences. The technology for recovery (extraction) ofthe raw bitumen has undergone significant developments in the past two decades. However, very significant hurdles remain to be cleared, and these will be briefly discussed.