17
History and Terminology
1.4.5 extrA HeAvy oIl
Briefly, extra heavy oil is a material that occurs in the solid or near-solid state and generally has
mobility under reservoir conditions.
The term extra heavy oil is a recently evolved term (related to viscosity) of little scientific meaning. While this type of oil may resemble tar sand bitumen and does not flow easily, extra heavy oil is
generally recognized as having mobility in the reservoir compared to tar sand bitumen, that is typically incapable of mobility (free flow) under reservoir conditions. For example, the tar sand bitumen
located in Alberta, Canada, is not mobile in the deposit and requires extreme methods of recovery
to recover the bitumen. On the other hand, much of the extra heavy oil located in the Orinoco belt of
Venezuela requires recovery methods that are less extreme because of the mobility of the material
in the reservoir (Schenk et al., 2009).
Whether the mobility of extra heavy oil is due to a high reservoir temperature (that is higher
than the pour point of the extra heavy oil) or due to other factors is variable and subject to localized
conditions in the reservoir.
1.4.6 BItumen
The term bitumen (also, on occasion, referred to as native asphalt, and extra heavy oil) includes a
wide variety of reddish brown to black materials of semisolid, viscous to brittle character that can
exist in nature with no mineral impurity or with mineral matter contents that exceed 50% by weight.
Bitumen is frequently found filling pores and crevices of sandstone, limestone, or argillaceous sediments, in which case the organic and associated mineral matrix is known as rock asphalt (Abraham,
1945; Hoiberg, 1964).
Bitumen is a naturally occurring material that is found in deposits where the permeability is low
and passage of fluids through the deposit can only be achieved by prior application of fracturing
techniques. Tar sand bitumen is a high-boiling material with little, if any, material boiling below
350°C (660°F) and the boiling range approximates the boiling range of an atmospheric residuum.
Tar sands have been defined in the United States (FE-76-4) as
…the several rock types that contain an extremely viscous hydrocarbon which is not recoverable in its
natural state by conventional oil well production methods including currently used enhanced recovery
techniques. The hydrocarbon-bearing rocks are variously known as bitumen-rocks oil, impregnated
rocks, oil sands, and rock asphalt.
The recovery of the bitumen depends to a large degree on the composition and construction of
the sands. Generally, the bitumen found in tar sand deposits is an extremely viscous material that is
immobile under reservoir conditions and cannot be recovered through a well by the application of
secondary or enhanced recovery techniques.
The expression tar sand is commonly used in the petroleum industry to describe sandstone reservoirs that are impregnated with a heavy, viscous black crude oil that cannot be retrieved through
a well by conventional production techniques (FE-76-4, above). However, the term tar sand is actually a misnomer; more correctly, the name tar is usually applied to the heavy product remaining
after the destructive distillation of coal or other organic matter (Speight, 1994).
The bitumen in tar sand formations requires a high degree of thermal stimulation for recovery to
the extent that some thermal decomposition may have to be induced. Current recovery operations
of bitumen in tar sand formations involve use of a mining technique and nonmining techniques are
continually being developed (Chapter 7) (Speight, 2009).
It is incorrect to refer to native bituminous materials as tar or pitch. Although the word tar is
descriptive of the black, heavy bituminous material, it is best to avoid its use with respect to natural materials and to restrict the meaning to the volatile or near-volatile products produced in the
History and Terminology
1.4.5 extrA HeAvy oIl
Briefly, extra heavy oil is a material that occurs in the solid or near-solid state and generally has
mobility under reservoir conditions.
The term extra heavy oil is a recently evolved term (related to viscosity) of little scientific meaning. While this type of oil may resemble tar sand bitumen and does not flow easily, extra heavy oil is
generally recognized as having mobility in the reservoir compared to tar sand bitumen, that is typically incapable of mobility (free flow) under reservoir conditions. For example, the tar sand bitumen
located in Alberta, Canada, is not mobile in the deposit and requires extreme methods of recovery
to recover the bitumen. On the other hand, much of the extra heavy oil located in the Orinoco belt of
Venezuela requires recovery methods that are less extreme because of the mobility of the material
in the reservoir (Schenk et al., 2009).
Whether the mobility of extra heavy oil is due to a high reservoir temperature (that is higher
than the pour point of the extra heavy oil) or due to other factors is variable and subject to localized
conditions in the reservoir.
1.4.6 BItumen
The term bitumen (also, on occasion, referred to as native asphalt, and extra heavy oil) includes a
wide variety of reddish brown to black materials of semisolid, viscous to brittle character that can
exist in nature with no mineral impurity or with mineral matter contents that exceed 50% by weight.
Bitumen is frequently found filling pores and crevices of sandstone, limestone, or argillaceous sediments, in which case the organic and associated mineral matrix is known as rock asphalt (Abraham,
1945; Hoiberg, 1964).
Bitumen is a naturally occurring material that is found in deposits where the permeability is low
and passage of fluids through the deposit can only be achieved by prior application of fracturing
techniques. Tar sand bitumen is a high-boiling material with little, if any, material boiling below
350°C (660°F) and the boiling range approximates the boiling range of an atmospheric residuum.
Tar sands have been defined in the United States (FE-76-4) as
…the several rock types that contain an extremely viscous hydrocarbon which is not recoverable in its
natural state by conventional oil well production methods including currently used enhanced recovery
techniques. The hydrocarbon-bearing rocks are variously known as bitumen-rocks oil, impregnated
rocks, oil sands, and rock asphalt.
The recovery of the bitumen depends to a large degree on the composition and construction of
the sands. Generally, the bitumen found in tar sand deposits is an extremely viscous material that is
immobile under reservoir conditions and cannot be recovered through a well by the application of
secondary or enhanced recovery techniques.
The expression tar sand is commonly used in the petroleum industry to describe sandstone reservoirs that are impregnated with a heavy, viscous black crude oil that cannot be retrieved through
a well by conventional production techniques (FE-76-4, above). However, the term tar sand is actually a misnomer; more correctly, the name tar is usually applied to the heavy product remaining
after the destructive distillation of coal or other organic matter (Speight, 1994).
The bitumen in tar sand formations requires a high degree of thermal stimulation for recovery to
the extent that some thermal decomposition may have to be induced. Current recovery operations
of bitumen in tar sand formations involve use of a mining technique and nonmining techniques are
continually being developed (Chapter 7) (Speight, 2009).
It is incorrect to refer to native bituminous materials as tar or pitch. Although the word tar is
descriptive of the black, heavy bituminous material, it is best to avoid its use with respect to natural materials and to restrict the meaning to the volatile or near-volatile products produced in the