Page 122 - Synthetic Fuels Handbook

108 CHAPTER FOUR

Miocene sheet sandstone. It overlies an eroded anticline of Upper Cretaceous age with
remnants of an early tertiary formation still preserved on the flanks.
The Trinidad bitumen is currently mined and sold as road asphalt. Estimates of the
amount available vary and a very approximate estimate indicates that at current production
rates (approximately 50,000 tons/year) there is believed to be sufficient to last 150 years.
There are no current plans to use the Trinidad bitumen as a source of synthetic fuels.
The Rumanian deposits are located at Derna deposits and occur (along with Tataros
and other deposits) in a triangular section east and northeast of Oradia between the Sebos
Koros and Berrettyo rivers. The tar sand occurs in the upper part of the Pliocene formation
and the asphalt is characterised by its penetrating odour. The reservoir rock is nonmarine,
representing freshwater deposition during a period of regression.
Tar sands occur at Cheildag, Kobystan and outcrop in the south flank of the Cheildag
anticline; there are approximately 24 million barrels of bitumen in place. Other deposits
in the former U.S.S.R. occur in the Olenek anticline (northeast of Siberia) and it has been
claimed that the extent of asphalt impregnation in the Permian sandstone is of the same
order of magnitude (in area and volume) as that of the Athabasca deposits. Tar sands have
also been reported from sands at Subovka and the Notanebi deposit (Miocene sandstone) is
reputed to contain 20 percent bitumen by weight. On the other hand, the Kazakhstan occur-
rence, near the Shubar-Kuduk oil field, is a bituminous lake with a bitumen content that has
been estimated to be of the order of 95 percent by weight of the deposit.
Tar sand occurrences also occur in the Southern Llanos of Colombia where drilling has
presented indications of deposits generally described as heavy crude oil, natural asphalt, and
bitumen. Most of these occurrences are recorded below 1500 ft (457 m). The tar sands at
Burgan in Kuwait and at the Inciarte and Bolivar coastal fields of the Maracaibo Basin are
of unknown dimensions. Those at Inciarte have been exploited and all are directly or closely
associated with large oil fields. The tar sands of the Bolivar coastal fields are above the oil
zones in Miocene beds and are in a lithologic environment similar to that of the Officina-
Tremblador tar belt. The small Miocene asphalt deposits in the Leyte Islands (Philippines) are
extreme samples of stratigraphic entrapment and resemble some of the Californian deposits.
Those of the Mefang Basin in Thailand are in Pliocene beds that overlie Triassic deposits and
their distribution is stratigraphically controlled. There is a small accumulation at Chumpi, near
Lima (Peru), which occurs in tuffaceous sands and it is believed to be derived from strongly
deformed Cretaceous limestone from which a petroleum-type was distilled as a result of
volcanic activity. Finally, tar sand deposits have also been recorded in Spain, Portugal, Cuba,
Argentina, Thailand, and Senegal but most are poorly defined and are considered to contain
(in-place) less than 1 million barrel of bitumen.

4.2 STRUCTURE AND PROPERTIES OF TAR SAND

Tar sand is a mixture of sand and other rock materials that is composed of approximately
80 to 85 percent sand, clay, and other mineral matter, 5 to 10 percent by weight of water,
and from 1 to 18 percent by weight of bitumen.
Bitumen is a thick, viscous carbonaceous material that, at room temperature, is in a near
solid state and which is immobile in the deposit.
Prior to processing, the bitumen is separated from the sand, other mineral materials, and
formation water before it is delivered to downstream upgraders or refineries. Shallow oil
sands deposits, less than about 250 ft (76 m) to the top of the tar sands zone, are exploited
using surface mining to recover ore-grade oil sands, which are then delivered to an extraction
plant for separation of bitumen from the sand, other minerals, and connate water. Deep oil
sands, greater than about 250 ft (76 m) to the top of the oil sands zone, are exploited using