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Recovery of Heavy Oil and Tar Sand Bitumen
Another aboveground method of separating bitumen from mined tar sand involves direct heating of the tar sand without previous separation of the bitumen. Thus, the bitumen is not recovered
as such but is an upgraded overhead product. In the process, the sand is crushed and introduced
into a vessel, where it is contacted with either hot (spent) sand or with hot product gases that furnish part of the heat required for cracking and volatilization. The volatile products are passed out
of the vessel and are separated into gases and (condensed) liquids. The coke that is formed as a
result of the thermal decomposition of the bitumen remains on the sand, which is then transferred
to a vessel for coke removal by burning in air. The hot flue gases can be used either to heat incoming tar sand or as refinery fuel. As expected, processes of this type yield an upgraded product
but require various arrangements of pneumatic and mechanical equipment for solids movement
around the refinery.
One approach toward recovering a significant portion of heavy oil from a reservoir is to use a
combination of petroleum recovery and mining technologies. Through the use of mining technology, access is developed below the petroleum reservoir within or beneath a permeability barrier.
Underground development consists of providing room for subsurface drilling and petroleum production operations as well as a life-supporting atmosphere and safe working conditions. Wells are
drilled at inclinations from the horizontal to the vertical upward into the reservoir. Wells produce as
a result of a combination of pressure depletion and gravity drainage.
In improved mining, directional (horizontal or slant) wells are drilled into the reservoir from a
mine in an underlying formation to drain oil by pressured depletion and gravity drainage. In the
process of gravity drainage extraction of liquid crude oil, the wells are completed so that only
the forces acting within the reservoir are used. The forces acting on the reservoir are left intact,
perhaps maintained or increased. A large number of closely spaced wells can be drilled into a
reservoir from an underlying tunnel more economically than the same number of wells from the
surface. In addition, only one pumping system is required in underground drainage, whereas at
the surface each well must have a pumping system. The objective of using a large number of wells
is to produce each well slowly so that the gas/oil and water/oil interfaces move toward each other
efficiently. By maintaining the reservoir pressures because of forces acting on the reservoir, it is
then assured that the oil production is provided by the internal forces due to gravity (the buoyancy
effect) and capillary effects.
The recovery efficiency is improved by applying an EOR method. The production drain holes
should be surveyed while drilling, and the drilling should be accomplished using mud-operated
drills with a bent sub for control of direction. The drain holes must be controlled so that a network
of uniformly spaced holes conforming to the data output from the computer modeling can be drilled
in the production zone. The drill string should be equipped with check valves to minimize the backflow of mud during the installation of additional drill pipe. The return mud line should be equipped
with a blow line to safely vent to the surface any formation gas encountered. All drilling should be
accomplished working through a blowout preventer or diverter. Drill cuttings should be contained
in a closed system and not allowed to encumber the mine atmosphere.
Large vertical shafts sunk from the surface are generally the means through which underground
openings can be excavated. These shafts are one means of access to offer an outlet for removal
of excavated rock, provide sufficient opening for equipment, provide ventilation, and allow the
removal of oil and gas products during later production. These requirements plus geological conditions and oil reservoir dimensions determine the shaft size. It is expected that an access shaft will
range from 8 to 20 ft in diameter.
Completing wells from a level of drifts beneath the reservoir is the most economical application
of gravity drainage. In this case, only one pumping system is required rather installing a pump in
each well as is necessary in wells drilled from the surface. When wells are drilled from beneath the
producing formation in an oil–water system, the developer has two options for completion. The casing may be set totally through the formation and the region opposite the oil saturation perforated to
permit production. If desired, the easing may pass only through the water-saturated zone and then
Recovery of Heavy Oil and Tar Sand Bitumen
Another aboveground method of separating bitumen from mined tar sand involves direct heating of the tar sand without previous separation of the bitumen. Thus, the bitumen is not recovered
as such but is an upgraded overhead product. In the process, the sand is crushed and introduced
into a vessel, where it is contacted with either hot (spent) sand or with hot product gases that furnish part of the heat required for cracking and volatilization. The volatile products are passed out
of the vessel and are separated into gases and (condensed) liquids. The coke that is formed as a
result of the thermal decomposition of the bitumen remains on the sand, which is then transferred
to a vessel for coke removal by burning in air. The hot flue gases can be used either to heat incoming tar sand or as refinery fuel. As expected, processes of this type yield an upgraded product
but require various arrangements of pneumatic and mechanical equipment for solids movement
around the refinery.
One approach toward recovering a significant portion of heavy oil from a reservoir is to use a
combination of petroleum recovery and mining technologies. Through the use of mining technology, access is developed below the petroleum reservoir within or beneath a permeability barrier.
Underground development consists of providing room for subsurface drilling and petroleum production operations as well as a life-supporting atmosphere and safe working conditions. Wells are
drilled at inclinations from the horizontal to the vertical upward into the reservoir. Wells produce as
a result of a combination of pressure depletion and gravity drainage.
In improved mining, directional (horizontal or slant) wells are drilled into the reservoir from a
mine in an underlying formation to drain oil by pressured depletion and gravity drainage. In the
process of gravity drainage extraction of liquid crude oil, the wells are completed so that only
the forces acting within the reservoir are used. The forces acting on the reservoir are left intact,
perhaps maintained or increased. A large number of closely spaced wells can be drilled into a
reservoir from an underlying tunnel more economically than the same number of wells from the
surface. In addition, only one pumping system is required in underground drainage, whereas at
the surface each well must have a pumping system. The objective of using a large number of wells
is to produce each well slowly so that the gas/oil and water/oil interfaces move toward each other
efficiently. By maintaining the reservoir pressures because of forces acting on the reservoir, it is
then assured that the oil production is provided by the internal forces due to gravity (the buoyancy
effect) and capillary effects.
The recovery efficiency is improved by applying an EOR method. The production drain holes
should be surveyed while drilling, and the drilling should be accomplished using mud-operated
drills with a bent sub for control of direction. The drain holes must be controlled so that a network
of uniformly spaced holes conforming to the data output from the computer modeling can be drilled
in the production zone. The drill string should be equipped with check valves to minimize the backflow of mud during the installation of additional drill pipe. The return mud line should be equipped
with a blow line to safely vent to the surface any formation gas encountered. All drilling should be
accomplished working through a blowout preventer or diverter. Drill cuttings should be contained
in a closed system and not allowed to encumber the mine atmosphere.
Large vertical shafts sunk from the surface are generally the means through which underground
openings can be excavated. These shafts are one means of access to offer an outlet for removal
of excavated rock, provide sufficient opening for equipment, provide ventilation, and allow the
removal of oil and gas products during later production. These requirements plus geological conditions and oil reservoir dimensions determine the shaft size. It is expected that an access shaft will
range from 8 to 20 ft in diameter.
Completing wells from a level of drifts beneath the reservoir is the most economical application
of gravity drainage. In this case, only one pumping system is required rather installing a pump in
each well as is necessary in wells drilled from the surface. When wells are drilled from beneath the
producing formation in an oil–water system, the developer has two options for completion. The casing may be set totally through the formation and the region opposite the oil saturation perforated to
permit production. If desired, the easing may pass only through the water-saturated zone and then