74
The Chemistry and Technology of Petroleum
leading to a proposal for a commercial venture. Shell Canada, Ltd. tested in sift recovery of bitumen;
a group headed by Cities Service Athabasca, Ltd. operated a pilot plant at Mildred Lake based on a
hot-water extraction process; and Great Canadian Oil Sands, Ltd. operated a pilot plant at the present commercial plant site near Mildred Lake. In addition, Mobil Oil Company has conducted tests
on in sift recovery, and Petrofina established a pilot facility across the Athabasca River from the site
of the Great Canadian Oil Sands (GCOS, now Suncor) plant. The operations of the latter two pilot
plants remain proprietary.
Although the origin of petroleum has been discussed elsewhere, it is appropriate to deal here
with the origin of bitumen. The mechanisms of bitumen formation differ somewhat from those of
petroleum formation.
There are two schools of thought regarding the origin of the bitumen. One is that the bitumen
was formed locally and has neither migrated a great distance, nor been subjected to large overburden pressures. Since under these conditions the bitumen cannot have been subjected to thermal
degradation, it is geologically young and therefore dense and viscous. The opposing theory assumes
a remote origin for the bitumen, both geographically and in geological time. The bitumen precursor is assumed to have migrated into the sand deposit, which may originally have been filled with
water. After the bitumen precursor migrated, the overburden pressures were relieved, and the light
portions of the crude evaporated, leaving behind a dense viscous residue. A more recent theory also
assumes a remote origin for the bitumen but postulates that bacteria carried into the reservoirs in
oxygenated, meteoric waters destroyed the light hydrocarbons.
The remote-origin theory would explain the water layer surrounding sand grains in the Athabasca
deposit. However, because the metals and porphyrin contents of bitumen are similar to those of
some conventional Alberta crude oils of Lower Cretaceous age and because Athabasca bitumen has
a relatively low coking temperature, the bitumen may be of Lower Cretaceous age. This is the age
of the McMurray formation, which is geologically young. This evidence supports the theory that
the bitumen was formed in situ and is a precursor, rather than a residue of some other material or oil
precursor. The issue remains unresolved.
On an international note, the bitumen in tar sand deposits represents a potentially large supply
of energy. However, many of the reserves are available only with some difficulty and that optional
refinery scenarios will be necessary for conversion of these materials to liquid products because of the
substantial differences in character between conventional petroleum and tar sand bitumen (Table 3.3).
Because of the diversity of available information and the continuing attempts to delineate the
various world tar sand deposits, it is virtually impossible to present accurate numbers that reflect
the extent of the reserves in terms of the barrel unit. Indeed, investigations into the extent of many
of the world’s deposits are continuing at such a rate that the numbers vary from one year to the next.
Accordingly, the data quoted here must be recognized as approximate with the potential of being
quite different at the time of publication.
Throughout this text, frequent reference is made to tar sand bitumen, but because commercial
operations have been in place for over 30 years it is not surprising that more is known about the
Alberta (Canada) tar sand reserves than any other reserves in the world. Therefore, when discussion
is made of tar sand deposits, reference is made to the relevant deposit, but when the information is
not available, the Alberta material is used for the purposes of the discussion.
Tar sand deposits are widely distributed throughout the world (Phizackerley and Scott, 1967;
Demaison, 1977; Meyer and Dietzman, 1981; Speight, 1990, 1997). The various deposits have been
described as belonging to two types:
1. Materials found in stratigraphic traps
2. Deposits located in structural traps
There are, inevitably, gradations, and combinations of these two types of deposits and a broad pattern of deposit entrapment are believed to exist. In general terms, the entrapment characteristics for
The Chemistry and Technology of Petroleum
leading to a proposal for a commercial venture. Shell Canada, Ltd. tested in sift recovery of bitumen;
a group headed by Cities Service Athabasca, Ltd. operated a pilot plant at Mildred Lake based on a
hot-water extraction process; and Great Canadian Oil Sands, Ltd. operated a pilot plant at the present commercial plant site near Mildred Lake. In addition, Mobil Oil Company has conducted tests
on in sift recovery, and Petrofina established a pilot facility across the Athabasca River from the site
of the Great Canadian Oil Sands (GCOS, now Suncor) plant. The operations of the latter two pilot
plants remain proprietary.
Although the origin of petroleum has been discussed elsewhere, it is appropriate to deal here
with the origin of bitumen. The mechanisms of bitumen formation differ somewhat from those of
petroleum formation.
There are two schools of thought regarding the origin of the bitumen. One is that the bitumen
was formed locally and has neither migrated a great distance, nor been subjected to large overburden pressures. Since under these conditions the bitumen cannot have been subjected to thermal
degradation, it is geologically young and therefore dense and viscous. The opposing theory assumes
a remote origin for the bitumen, both geographically and in geological time. The bitumen precursor is assumed to have migrated into the sand deposit, which may originally have been filled with
water. After the bitumen precursor migrated, the overburden pressures were relieved, and the light
portions of the crude evaporated, leaving behind a dense viscous residue. A more recent theory also
assumes a remote origin for the bitumen but postulates that bacteria carried into the reservoirs in
oxygenated, meteoric waters destroyed the light hydrocarbons.
The remote-origin theory would explain the water layer surrounding sand grains in the Athabasca
deposit. However, because the metals and porphyrin contents of bitumen are similar to those of
some conventional Alberta crude oils of Lower Cretaceous age and because Athabasca bitumen has
a relatively low coking temperature, the bitumen may be of Lower Cretaceous age. This is the age
of the McMurray formation, which is geologically young. This evidence supports the theory that
the bitumen was formed in situ and is a precursor, rather than a residue of some other material or oil
precursor. The issue remains unresolved.
On an international note, the bitumen in tar sand deposits represents a potentially large supply
of energy. However, many of the reserves are available only with some difficulty and that optional
refinery scenarios will be necessary for conversion of these materials to liquid products because of the
substantial differences in character between conventional petroleum and tar sand bitumen (Table 3.3).
Because of the diversity of available information and the continuing attempts to delineate the
various world tar sand deposits, it is virtually impossible to present accurate numbers that reflect
the extent of the reserves in terms of the barrel unit. Indeed, investigations into the extent of many
of the world’s deposits are continuing at such a rate that the numbers vary from one year to the next.
Accordingly, the data quoted here must be recognized as approximate with the potential of being
quite different at the time of publication.
Throughout this text, frequent reference is made to tar sand bitumen, but because commercial
operations have been in place for over 30 years it is not surprising that more is known about the
Alberta (Canada) tar sand reserves than any other reserves in the world. Therefore, when discussion
is made of tar sand deposits, reference is made to the relevant deposit, but when the information is
not available, the Alberta material is used for the purposes of the discussion.
Tar sand deposits are widely distributed throughout the world (Phizackerley and Scott, 1967;
Demaison, 1977; Meyer and Dietzman, 1981; Speight, 1990, 1997). The various deposits have been
described as belonging to two types:
1. Materials found in stratigraphic traps
2. Deposits located in structural traps
There are, inevitably, gradations, and combinations of these two types of deposits and a broad pattern of deposit entrapment are believed to exist. In general terms, the entrapment characteristics for