165
Recovery of Heavy Oil and Tar Sand Bitumen
principles are also operative for reductions in the nitrogen, sulfur, and oxygen contents. This latter
occurrence also improves catalyst life and activity as well as reduces the metals content. In short,
in situ recovery processes (although less efficient in terms of bitumen recovery relative to mining
operations) may have the added benefit of leaving some of the more obnoxious constituents (from
the processing objective) in the ground.
7.3.3 otHer ProCesses
Many innovative concepts in heavy oil production have been developed and the major new technologies that have positively affected the heavy oil industry in the last 10 years are
1. Horizontal well technology for shallow applications (1000 m), often combined with gravity
drainage approaches
2. Cold production using long horizontal wells that are often combined with multilaterals
with aggregate lengths exceeding several kilometers
3. Gravity-driven production, particularly steam-assisted gravity drainage (SAGD), vaporassisted petroleum extraction (VAPEX), and inert gas injection (IGI), all using horizontal
wells to establish stable, gravity-assisted oil recovery
4. Cold heavy oil production with sand (CHOPS), where sand production is encouraged and
managed as a means of enhancing well productivity
5. Pressure pulse flow technology, both as a reservoir-wide method and as a work-over method
The oil industry pioneered drilling shallow (500–3500 ft deep) horizontal wells a cost-per-meter
values that are now only 1.2–1.3 times those of vertical wells. These wells, in the shallowest cases
(150–1500 ft deep), are often drilled using masts inclined to reduce curvature build rates required
to turn the corner from vertical to horizontal. In reduced footprint developments, where there are
a number of producing wells and injecting wells on the same pad (savings in roads, services, etc.),
many horizontal wells (2–6) may be drilled from a small area, no larger than a hectare.
Coiled tubing drilling and work-over have been introduced and perfected in the last decade,
further reducing costs of horizontal well drilling. Good seismic control and cuttings analysis allows
precise steering in thin zones (20′) to place the well in the optimum position in the reservoir. In
the production phase, the long drainage length of a single well, as much as 1200 m in many cases,
allows much more effective production, also giving higher production percentages of original oil in
place (OOIP) when used in gravity drainage technologies.
Long horizontal wells with several multilateral branches have been used widely in the development of heavy oils of Venezuela, where production rates as high as 2,000–2,500 bbl/day in some
wells have been achieved through the use of aggregate horizontal lengths as large as 10,000 m in
oil of 1,200–5,000 cP viscosity. Unfortunately, this technology can only achieve 8%–15% recovery,
and only from the best high permeability zones. Thus, for the more efficient development of these
resources, other technologies will necessarily be implemented in the future.
Horizontal wells using cold primary production in heavy oils have been widely used in Canada
since the late 1980s, but the successes (usually well published) have been substantially offset by the
failures (rarely published). Furthermore, low recovery factors (seldom close to 10%), early water
breakthrough (usually impossible to plug when it happens), short well life (30%–40% decline per
year) and other factors such as expensive work-over if sand plugging takes place have combined to
make this a technology that has little attraction in Canada.
IGI is a technology for conventional oils in reservoirs where good vertical permeability exists,
or where it can be created through propped hydraulic fracturing. It is generally viewed as a topdown process with nitrogen or methane injection through vertical wells at the top of the reservoirs,
creating a gas–oil interface that is slowly displaced toward long horizontal production wells. As
with all gravity drainage processes, it is essential to balance the injection and production volumes
Recovery of Heavy Oil and Tar Sand Bitumen
principles are also operative for reductions in the nitrogen, sulfur, and oxygen contents. This latter
occurrence also improves catalyst life and activity as well as reduces the metals content. In short,
in situ recovery processes (although less efficient in terms of bitumen recovery relative to mining
operations) may have the added benefit of leaving some of the more obnoxious constituents (from
the processing objective) in the ground.
7.3.3 otHer ProCesses
Many innovative concepts in heavy oil production have been developed and the major new technologies that have positively affected the heavy oil industry in the last 10 years are
1. Horizontal well technology for shallow applications (1000 m), often combined with gravity
drainage approaches
2. Cold production using long horizontal wells that are often combined with multilaterals
with aggregate lengths exceeding several kilometers
3. Gravity-driven production, particularly steam-assisted gravity drainage (SAGD), vaporassisted petroleum extraction (VAPEX), and inert gas injection (IGI), all using horizontal
wells to establish stable, gravity-assisted oil recovery
4. Cold heavy oil production with sand (CHOPS), where sand production is encouraged and
managed as a means of enhancing well productivity
5. Pressure pulse flow technology, both as a reservoir-wide method and as a work-over method
The oil industry pioneered drilling shallow (500–3500 ft deep) horizontal wells a cost-per-meter
values that are now only 1.2–1.3 times those of vertical wells. These wells, in the shallowest cases
(150–1500 ft deep), are often drilled using masts inclined to reduce curvature build rates required
to turn the corner from vertical to horizontal. In reduced footprint developments, where there are
a number of producing wells and injecting wells on the same pad (savings in roads, services, etc.),
many horizontal wells (2–6) may be drilled from a small area, no larger than a hectare.
Coiled tubing drilling and work-over have been introduced and perfected in the last decade,
further reducing costs of horizontal well drilling. Good seismic control and cuttings analysis allows
precise steering in thin zones (20′) to place the well in the optimum position in the reservoir. In
the production phase, the long drainage length of a single well, as much as 1200 m in many cases,
allows much more effective production, also giving higher production percentages of original oil in
place (OOIP) when used in gravity drainage technologies.
Long horizontal wells with several multilateral branches have been used widely in the development of heavy oils of Venezuela, where production rates as high as 2,000–2,500 bbl/day in some
wells have been achieved through the use of aggregate horizontal lengths as large as 10,000 m in
oil of 1,200–5,000 cP viscosity. Unfortunately, this technology can only achieve 8%–15% recovery,
and only from the best high permeability zones. Thus, for the more efficient development of these
resources, other technologies will necessarily be implemented in the future.
Horizontal wells using cold primary production in heavy oils have been widely used in Canada
since the late 1980s, but the successes (usually well published) have been substantially offset by the
failures (rarely published). Furthermore, low recovery factors (seldom close to 10%), early water
breakthrough (usually impossible to plug when it happens), short well life (30%–40% decline per
year) and other factors such as expensive work-over if sand plugging takes place have combined to
make this a technology that has little attraction in Canada.
IGI is a technology for conventional oils in reservoirs where good vertical permeability exists,
or where it can be created through propped hydraulic fracturing. It is generally viewed as a topdown process with nitrogen or methane injection through vertical wells at the top of the reservoirs,
creating a gas–oil interface that is slowly displaced toward long horizontal production wells. As
with all gravity drainage processes, it is essential to balance the injection and production volumes