CRUDE OIL CLASSIFICATION AND BENCHMARKS
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Furthermore, petroleum varies in composition from one oil field
to another, from one well to another in the same field, and even from
one level to another in the same well. This variation can be in both
molecular weight and the types of molecules present in petroleum.
4.1.3 Density and API Gravity
The use of density values has been advocated for quantitative application using a scheme based on the American Petroleum Institute
(API) gravity, which offers a wider scale of values by which crude
oil can be classified and priced. As indicated above, the density of
crude oil varies slightly from conventional crude to heavy crude.
Light crude oil is usually oil having API gravity above 30 or
35°API. Medium crude oil falls into the API gravity range is below
these numbers. Heavy oil is considered to be those petroleum-type
materials that had gravity somewhat less than 20°API, with the
heavy oils falling into the API gravity range 10 to 15° (e.g., Cold
Lake crude oil = 12°API) and bitumen falling into the 5 to 10°API
range (e.g., Athabasca bitumen = 8°API).
However, the assignment of specific numbers to the classification of petroleum is fraught with difficulty. Using such points of
demarcation does not circumvent the question that must arise
when one considers a material having API gravity equal to 9.9 and
one material having API gravity equal to 10.1; nor does the point of
demarcation make allowance for the limitations of the accuracy of
the analytical method. The use of one physical parameter, be it API
gravity or any other physical property for that matter, is inadequate
to the task of classifying conventional petroleum, heavy oil, and tar
sand bitumen.
4.1.4 Viscosity
At the same time, in concert with the use of API gravity, the line of
demarcation between petroleum and heavy oil vis-à-vis tar sand
bitumen has been drawn at 10,000 centipoises. Briefly, materials
having a viscosity of less than 10,000 centipoises are conventional
petroleum and heavy oil, while tar sand bitumen has a viscosity
greater than 10,000 centipoises. The use of such a scale requires a
fine line of demarcation between the various crude oils, heavy oils,
and bitumen to the point where it would be confusing to have to
differentiate between a material having a viscosity of 9950 cp and
109
Furthermore, petroleum varies in composition from one oil field
to another, from one well to another in the same field, and even from
one level to another in the same well. This variation can be in both
molecular weight and the types of molecules present in petroleum.
4.1.3 Density and API Gravity
The use of density values has been advocated for quantitative application using a scheme based on the American Petroleum Institute
(API) gravity, which offers a wider scale of values by which crude
oil can be classified and priced. As indicated above, the density of
crude oil varies slightly from conventional crude to heavy crude.
Light crude oil is usually oil having API gravity above 30 or
35°API. Medium crude oil falls into the API gravity range is below
these numbers. Heavy oil is considered to be those petroleum-type
materials that had gravity somewhat less than 20°API, with the
heavy oils falling into the API gravity range 10 to 15° (e.g., Cold
Lake crude oil = 12°API) and bitumen falling into the 5 to 10°API
range (e.g., Athabasca bitumen = 8°API).
However, the assignment of specific numbers to the classification of petroleum is fraught with difficulty. Using such points of
demarcation does not circumvent the question that must arise
when one considers a material having API gravity equal to 9.9 and
one material having API gravity equal to 10.1; nor does the point of
demarcation make allowance for the limitations of the accuracy of
the analytical method. The use of one physical parameter, be it API
gravity or any other physical property for that matter, is inadequate
to the task of classifying conventional petroleum, heavy oil, and tar
sand bitumen.
4.1.4 Viscosity
At the same time, in concert with the use of API gravity, the line of
demarcation between petroleum and heavy oil vis-à-vis tar sand
bitumen has been drawn at 10,000 centipoises. Briefly, materials
having a viscosity of less than 10,000 centipoises are conventional
petroleum and heavy oil, while tar sand bitumen has a viscosity
greater than 10,000 centipoises. The use of such a scale requires a
fine line of demarcation between the various crude oils, heavy oils,
and bitumen to the point where it would be confusing to have to
differentiate between a material having a viscosity of 9950 cp and