Note: Descriptions are shown in the official language in which they were submitted.
1
PROCESS FOR RECOVERING HYDROCARBONS INCLUDING AN IN SITU
COMBUSTION PHASE
FIELD OF THE TECHNOLOGY
[01] The present technology relates to a process for recovering bitumen/oil
from an
underground reservoir and more precisely to an in situ combustion recovery
process for
mature hydrocarbon recovery operations, such as in situ thermal operations.
BACKGROUND
[02] In situ steam based thermal extraction is one of the most extensively
used
techniques for recovering heavy hydrocarbons, such as heavy oils and bitumen,
from
underground reservoirs. For example, this technique has been successful in
extracting
bitumen from the Northern Alberta oil sands. Cyclic Steam Simulation (CSS) and
Steam
Assisted Gravity Drainage (SAGD) are two major processes that have been used
for in
situ thermal extraction. However, each of these processes has an economic
limit and
when this limit is reached; steam injection is terminated or scaled back. The
economic limit
.. of a SAGD operation depends of course on several factors. One indicator
that a SAGD
process is approaching its economic limit is often when the steam chambers
which have
developed in the reservoir have stopped increasing in volume. In the latter
stage of a
SADG operation as it approaches or reaches its economic limit, the SAGD
operation is
generally referred to as being "mature". In the case of multiple SAGD well
pairs adjacent to
one another, which is often the case in the field, individual steam chambers
developed
above and around each well pair begin to coalesce with one another until one
common
steam chamber is formed. Eventually an equilibrium is reached at which point
the steam
chamber generally stops growing, assuming a constant steam injection rate is
maintained.
The maturity of a SAGD operation can also be indicated for example in terms of
the
steam-oil ratio (SOR). When the SOR is too high, the process becomes
uneconomic.
However, when a SAGD operation has reached maturity, significant oil/bitumen
still
remains in the reservoir and the SAGD chambers and it would be desirable to
recover as
much as possible of the remaining hydrocarbons.
[03] In situ combustion is another technique which can be used to extract
oil/bitumen
from underground reservoirs. In general, in situ combustion involves the
injection of an
Date Recue/Date Received 2022-07-19
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oxidizing gas such as air into the reservoir to enable combustion of some of
the reservoir
hydrocarbons underground as fuel, thus heating and forcing the mobilized
hydrocarbons to
facilitate production. There are several known methods of in situ combustion
using various
injection and production wells patterns and orientations, oxidizing gas
injection strategies
and well constructions and designs. However, in various reservoir geologies
and
scenarios, in situ combustion has not been a proven method for bitumen
recovery. Indeed,
several in situ combustion field projects have been prematurely terminated,
due to low fluid
mobility in the reservoir and oxygen or combustion front rapid breakthrough
from the
producers among other challenges. Oxygen breakthrough has several challenges
including hazards such as light hydrocarbon vapor/gas explosions at producers
resulting in
tubular damage, flue gas breakthrough at producers causing wellbore gas-liquid
interference during production, and acid gas resulting in corrosion both in
downhole
equipment and surface facilities.
[04] Canadian patent No. 2,594,414 discloses a technology for recovering
oil/bitumen
using an air injection method into wells previously employed for a SAGD
operation.
Continuous air injection is conducted through an injection well while
producers are
maintained open in production mode throughout the process. This purportedly
allows
keeping the SAGD zones at constant pressure. The speed of combustion front in
the
formation is purportedly designed by the rate of air to be injected. However,
continuous air
injection is a technique which is difficult to apply to bitumen recovery, for
instance because
of the problem of air or oxygen early breakthrough observed in in situ
combustion field
applications. One reason for difficulties is due to significant heterogeneity
in the reservoir,
especially after SAGD operation, where hot spots and cold spots are observed.
Hot spots
show a high mobility of gas/air due to lower oil/bitumen saturation and lower
oil/bitumen
viscosity, compared to cold spots. Fluid saturation and temperature
distributions can vary
from place to place at the mature stage of a SAGD operation, which creates
heterogeneity
to fluid mobility. Therefore, air or oxygen tend to flow through the area that
is of the lowest
flowing resistance, Le. the highest directional permeability streaks or most
depleted
portions within the SAGD chamber. Another reason for difficulties is that
within mature
steam chamber, the air injector(s) will connect to producer(s) through some
high
permeability streaks that are of the lowest flow resistance to air or flue gas
and become
Date Recue/Date Received 2022-07-19
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early oxygen/combustion breakthrough paths, if measures related to restriction
of
production are not taken.
[05] There is thus a need for a technology that overcomes at least some of the
drawbacks of what is known in the field, such as the above-mentioned drawback
that can
result from premature oxygen/combustion breakthrough and/or low mobility of
fluids, that
increases the recovery of hydrocarbons from an underground reservoir at a
mature stage
of a SAGD operation and/or that enables hydrocarbon recovery while reducing or
maintaining a low steam-oil ratio.
SUMMARY
.. [06] The present technology responds to the above need by providing an in
situ
combustion recovery process for mature hydrocarbon recovery operations, such
as in situ
thermal operations.
[07] In a first aspect, there is provided a process for in situ
combustion in a mature
hydrocarbon recovery operation in an underground reservoir, the mature
hydrocarbon
recovery operation including well pairs and an interwell communication zone
between the
well pairs, the process including injecting an oxidizing gas through at least
one well to
initiate combustion and promote mobilization of residual heavy hydrocarbons in
the
reservoir, wherein the oxidizing gas is injected at an injection flux of about
0.3 to about 1.2
m3(ST)/m2.hour.
[08] In another aspect, there is provided a process for in situ combustion
in a mature
Steam-Assisted Gravity Drainage (SAGD) operation in an underground reservoir,
the
mature SAGD operation including well pairs and an interwell communication zone
between
the well pairs, the process including injecting an oxidizing gas through at
least one well to
initiate combustion and promote mobilization of residual heavy hydrocarbons in
the
reservoir, wherein the oxidizing gas is injected at an injection flux of about
0.3 to about 1.2
m3(ST)/m2.hour.
[09] In one implementation, the interwell communication zone has a bitumen
saturation
of from about 0.20 to about 0.05.
[010] In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
Date Recue/Date Received 2022-07-19
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[011] In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[012] In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[013] In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[014] In one implementation, the oxidizing gas is oxygen, air, enriched air, a
mixture
steam/air or a mixture thereof.
[015] In one implementation, the oxidizing gas further includes additional
components
.. including methane or fuel gas or a combination thereof.
[016] In one implementation, the oxidizing gas further includes CO2, recovered
flue gases
from a previous combustion sequence, and/or N2.
[017] In one implementation, the oxidizing gas further includes water.
[018] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
[019] In one implementation, the oxidizing gas is air.
[020] In one implementation, each well pair includes a fluid injection well
and a
production well, the oxidizing gas being injected through the fluid injection
well of one of
the well pairs.
[021] In one implementation, the process includes operating the production
well of the
well pair including the injection well where the oxidizing gas is injected in
shut-in or choked
mode as long as the oxidizing gas is injected.
[022] In one implementation, the production well is operated in shut-in mode
as long as
the oxidizing gas is injected.
[023] In one implementation, the oxidizing gas is injected through a well
which is on one
end of the interwell communication zone.
[024] In one implementation, the oxidizing gas injection is injected through
the injection
well of an outside one of the well pairs.
[025] In another aspect, there is provided a process for in situ combustion in
a mature
Steam-Assisted Gravity Drainage (SAGD) operation in an underground reservoir,
the mature
Date Recue/Date Received 2022-07-19
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SAGD operation comprising well pairs and an interwell communication zone
between the
well pairs, each well pair comprising a fluid injection well having a
horizontal portion and a
production well having a horizontal portion positioned below and aligned with
the horizontal
portion of the injection well, the process comprising injecting an oxidizing
gas through at
least one fluid injection well of one of the well pairs to initiate combustion
and promote
mobilization of residual heavy hydrocarbons in the reservoir, wherein the
interwell
communication zone has a bitumen saturation of from about 0.20 to about 0.05,
and wherein
the production well of the well pair comprising the injection well where the
oxidizing gas is
injected is operated in shut-in or choked mode while the oxidizing gas is
injected.
[026] In a further aspect, there is provided a process for in situ combustion
in a mature
hydrocarbon recovery operation in an underground reservoir, the mature
hydrocarbon
recovery operation comprising well pairs and an interwell communication zone
between the
well pairs, each well pair comprising a fluid injection well having a
horizontal portion and a
production well having a horizontal portion positioned below and aligned with
the horizontal
portion of the injection well, the process comprising injecting an oxidizing
gas through at
least one fluid injection well of one of the well pairs to initiate combustion
and promote
mobilization of residual heavy hydrocarbons in the reservoir, wherein the
interwell
communication zone has a bitumen saturation of from about 0.20 to about 0.05,
and wherein
the production well of the well pair comprising the injection well where the
oxidizing gas is
injected is operated in shut-in or choked mode while the oxidizing gas is
injected.
[027] In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
[028] In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[029] In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[030] In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[031] In one implementation, the oxidizing gas is oxygen, air, enriched air, a
mixture
steam/air or a mixture thereof.
Date Recue/Date Received 2022-07-19
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[032] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[033] In one implementation, the oxidizing gas further includes CO2, recovered
flue gases
from a previous combustion sequence, and/or N2.
[034] In one implementation, the oxidizing gas further includes water.
[035] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
[036] In one implementation, the oxidizing gas is air.
[037] In one implementation, the production well is operated in shut-in mode
as long as
the oxidizing gas is injected.
[038] In one implementation, the oxidizing gas is injected through a well
which is on one
end of the interwell communication zone.
[039] In one implementation, the oxidizing gas injection is injected through
the injection
well of an outside one of the well pairs.
[040] In another aspect, there is provided an in situ process for recovering
heavy
hydrocarbons from an underground reservoir, including:
a) providing an array of well pairs for gravity controlled recovery of heavy
hydrocarbons, each well pair including a fluid injection well having a
horizontal
portion and a production well having a horizontal portion positioned below and
aligned with the horizontal portion of the injection well;
b) operating the array of adjacent well pairs to produce hydrocarbons from the
production wells and forming mobilized chambers within the reservoir
extending from corresponding well pairs;
c) establishing fluid communication between the mobilized chambers of adjacent
ones of the well pairs to create an interwell mobilized zone;
d) operating at least one well as an oxidizing gas injection well;
e) injecting oxidizing gas through the oxidizing gas injection well into a
corresponding one of the mobilized chambers to form a combustion region at
least partially sustained by residual hydrocarbons in the reservoir, the
combustion region having a combustion front;
Date Recue/Date Received 2022-07-19
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f) promoting displacement of the combustion front through the interwell
communication zone to sweep the array of well pairs;
g) regulating the array of well pairs to pressurize the interwell
communication
zone;
h) terminating oxidizing gas injection;
i) regulating the array of well pairs to effectuate blowdown and produce a
blowdown portion of the heavy hydrocarbons therefrom;
j) terminating blowdown; and
k) repeating the sequence of steps d) to j).
[041] In one implementation, step d) includes converting a fluid injection
well into the
oxidizing gas injection well.
[042] In one implementation, the process includes operating the production
well of the
well pair including the oxidizing gas injection well in shut-in or choked mode
while injecting
the oxidizing gas through the oxidizing gas injection well.
[043] In one implementation, the production well of the well pair including
the oxidizing
gas injection well is operated in shut-in mode as long as the oxidizing gas is
injected
through the oxidizing gas injection well.
[044] In one implementation, step f) includes:
operating the well pairs downstream of the combustion front in production mode
while the combustion front advances there-toward; and
restricting each of the well pairs once the combustion front respectively
reaches
each of the well pairs.
[045] In one implementation, both the injection well and the production well
of each well
pair are operated in production mode while the combustion front advances there-
toward.
[046] In one implementation, both the injection well and the production well
of each well
pair are operated in shut-in or choked mode once the combustion front
respectively
reaches each of the well pairs.
Date Recue/Date Received 2022-07-19
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[047] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of heat there-through.
[048] In one implementation, the restricting of each of the well pairs is
performed upon
breakthrough of combustion gas there-through.
[049] In one implementation, step g) includes operating the well pairs in shut-
in or choke
mode to achieve pressurization of the interwell communication zone.
[050] In one implementation, step i) includes operating at least one of the
wells of the
array of well pairs in production mode.
[051] In one implementation, step i) includes operating the production wells
in production
mode.
[052] In one implementation, step i) includes operating the fluid injection
well and the
production well of each of the well pairs of the array in production mode.
[053] In one implementation, the interwell communication zone extends along
substantially the entire length of the horizontal portions of each of the well
pairs.
[054] In one implementation, the underground reservoir is further provided
with at least
one infill well positioned in between two adjacent well pairs.
[055] In one implementation, step c) includes establishing fluid communication
between
the mobilized chambers and the at least one infill well thereby fluidly
connecting the infill
well with the interwell communication zone.
[056] In one implementation, step d) includes converting the infill well into
the oxidizing
gas injection well.
[057] In one implementation, step f) includes:
operating the at least one infill well downstream of the combustion front in
production mode while the combustion front advances there-toward; and
restricting each of the at least one infill well once the combustion front
respectively
reaches each of the at least one infill well.
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[058] In one implementation, each of the at least one infill well is operated
in shut-in or
choked mode once the combustion front respectively reaches each of the at
least one infill
well.
[059] In one implementation, step g) includes operating each of the at least
one infill well
in shut-in or choke mode to help achieve pressurization of the interwell
communication
zone.
[060] In one implementation, step i) includes operating each of the at least
one infill well
in production mode.
[061] In one implementation, step k) includes selecting the same well as the
oxidizing
gas injection well for each sequence.
[062] In one implementation, step k) includes selecting a different well as
the oxidizing
gas injection well for a subsequent sequence.
[063] In one implementation, a single well is used as the oxidizing gas
injection well.
[064] In one implementation, the oxidizing gas injection well is on one end of
the interwell
communication zone.
[065] In one implementation, the oxidizing gas injection well is the injection
well of an
outside one of the well pairs.
[066] In one implementation, the combustion front displaces from one end of
the interwell
communication zone over the array of well pairs to the opposed end of the
interwell
communication zone.
[067] In one implementation, the combustion front displaces across the array
of well pairs
in a direction perpendicular with respect to the well pairs.
[068] In another aspect, there is provided a cyclic in situ combustion process
for a
mature steam assisted gravity drainage (SAGD) operation in an underground
reservoir,
the mature SAGD operation including an array of well pairs generally parallel
to each other
and an interwell communication zone between the well pairs, each well pair
including a
fluid injection well having a horizontal portion and a production well having
a horizontal
portion positioned below and aligned with the horizontal portion of the
injection well, the
cyclic in situ combustion process including:
Date Recue/Date Received 2022-07-19
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(i) operating at least one well as an oxidizing gas injection well;
(ii) injecting oxidizing gas through the oxidizing gas injection well into a
corresponding one of the mobilized chambers to form a combustion region
at least partially sustained by residual hydrocarbons in the reservoir, the
combustion region having a combustion front;
(iii) promoting displacement of the combustion front through the interwell
communication zone to sweep the array of well pairs;
(iv) pressurizing the interwell communication zone;
(v) terminating oxidizing gas injection;
(vi) producing a blowdown portion of the heavy hydrocarbons therefrom;
(vii) terminating blowdown; and
(viii) repeating the sequence of steps (i) to (vii).
[071] In one implementation, step (i) includes converting a fluid injection
well of one of
the well pairs into the oxidizing gas injection well.
[072] In one implementation, the process includes operating the production
well of the
well pair including the oxidizing gas injection well in shut-in or choked mode
while injecting
the oxidizing gas through the oxidizing gas injection well.
[073] In one implementation, the production well of the well pair including
the oxidizing
gas injection well is operated in shut-in mode as long as the oxidizing gas is
injected
through the oxidizing gas injection well.
[074] In one implementation, step (iii) includes:
operating the well pairs downstream of the combustion front in production mode
while the combustion front advances there-toward; and
restricting each of the well pairs once the combustion front respectively
reaches
each of the well pairs.
[075] In one implementation, both the injection well and the production well
of each well
pair are operated in production mode while the combustion front advances there-
toward.
Date Recue/Date Received 2022-07-19
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[076] In one implementation, both the injection well and the production well
of each well
pair are operated in shut-in or choked mode once the combustion front
respectively
reaches each of the well pairs.
[077] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of heat there-through.
[078] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of combustion gas there-through.
[079] In one implementation, step (iv) includes operating the well pairs in
shut-in or choke
mode to achieve pressurization of the interwell communication zone.
[080] In one implementation, step (vi) includes operating at least one of the
wells of the
array of well pairs in production mode.
[081] In one implementation, step (vi) includes operating the production wells
in
production mode.
[082] In one implementation, step (vi) includes operating the fluid injection
well and the
production well of each of the well pairs of the array in production mode.
[083] In one implementation, the interwell communication zone extends along
substantially the entire length of the horizontal portions of each of the well
pairs.
[084] In one implementation, the process includes providing at least one
infill well
positioned in between two adjacent well pairs.
[085] In one implementation, the process includes establishing fluid
communication
between the mobilized chambers and the at least one infill well thereby
fluidly connecting
the infill well with the interwell communication zone.
[086] In one implementation, the process includes converting the infill well
into the
oxidizing gas injection well.
[087] In one implementation, step (iii) includes:
operating the at least one infill well downstream of the combustion front in
production mode while the combustion front advances there-toward; and
Date Recue/Date Received 2022-07-19
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restricting each of the at least one infill well once the combustion front
respectively
reaches each of the at least one infill well.
[088] In one implementation, each of the at least one infill well is operated
in shut-in or
choked mode once the combustion front respectively reaches each of the at
least one infill
well.
[089] In one implementation, step (iv) includes operating each of the at least
one infill
well in shut-in or choke mode to help achieve pressurization of the interwell
communication zone.
[090] In one implementation, step (vi) includes operating each of the at least
one infill
well in production mode.
[091] In one implementation, step (viii) includes selecting the same well as
the oxidizing
gas injection well for each sequence.
[092] In one implementation, step (viii) includes selecting a different well
as the oxidizing
gas injection well for a subsequent sequence.
[093] In one implementation, a single well is used as the oxidizing gas
injection well.
[094] In one implementation, the oxidizing gas injection well is on one end of
the interwell
communication zone.
[095] In one implementation, the oxidizing gas injection well is the injection
well of an
outside one of the well pairs.
[096] In one implementation, the combustion front displaces from one end of
the interwell
communication zone over the array of well pairs to the opposed end of the
interwell
communication zone.
[097] In one implementation, the combustion front displaces across the array
of well pairs
in a direction perpendicular with respect to the well pairs.
[098] In one implementation, step (vi) is performed so as to establish fluid
communication
between the interwell communication zone and the at least one infill well.
[099] In a further aspect, there is provided an in situ process for recovering
heavy
hydrocarbons from a reservoir, an array of well pairs being located in the
reservoir,
Date Recue/Date Received 2022-07-19
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wherein mobilized chambers in fluid communication with each other extend
upward from
respective well pairs and form an interwell communication zone, the process
including:
injecting oxidizing gas through at least one well into a corresponding one of
the
mobilized chambers to form a combustion region at least partially sustained by
residual hydrocarbons in the reservoir, the combustion region having a
combustion front, wherein the combustion front is swept across the array of
well
pairs;
terminating oxidizing gas injection;
producing the heavy hydrocarbons from at least one of the wells of the array;
and
restarting the process at the oxidizing gas injection step.
[0100] In another aspect, there is provided an in situ process for recovering
heavy
hydrocarbons from a reservoir, an array of well pairs being located in the
reservoir,
wherein mobilized chambers in fluid communication with each other extend
upward from
respective well pairs and form an interwell communication zone, the process
including:
injecting oxidizing gas through at least one well into a corresponding one of
the
mobilized chambers to form a combustion region at least partially sustained by
residual hydrocarbons in the reservoir, the combustion region having a
combustion front, wherein the combustion front is swept across the array of
well pairs;
serially restricting each of the well pairs once the combustion front
respectively
reaches each of the well pairs;
producing the heavy hydrocarbons from at least one of the wells of the array.
[0101] In one implementation, each well pair includes a fluid injection well
having a
horizontal portion and a production well having a horizontal portion
positioned below and
aligned with the horizontal portion of the injection well and wherein the
oxidizing gas is
injected in the fluid injection well of one of the well pairs.
[0102] In one implementation, the process includes operating the production
well of the
well pair including the oxidizing gas injection well in shut-in or choked mode
while injecting
the oxidizing gas through the oxidizing gas injection well.
Date Recue/Date Received 2022-07-19
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[0103] In one implementation, the production well of the well pair including
the oxidizing
gas injection well is operated in shut-in mode as long as the oxidizing gas is
injected
through the oxidizing gas injection well.
[0104] In one implementation, the combustion front is swept across the array
of well pairs
by operating the well pairs downstream of the combustion front in production
mode while
the combustion front advances there-toward and each of the well pairs is
restricted once
the combustion front respectively reaches each of the well pairs.
[0105] In one implementation, both the injection well and the production well
of each well
pair are operated in production mode while the combustion front advances there-
toward.
.. [0106] In one implementation, both the injection well and the production
well of each well
pair are operated in shut-in or choked mode once the combustion front
respectively
reaches each of the well pairs.
[0107] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of heat there-through.
[0108] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of combustion gas there-through.
[0109] In one implementation, the process includes pressurizing the interwell
communication zone through injecting the oxidizing gas and operating the well
pairs in
shut-in or choke mode.
[0110] In one implementation, the production of the heavy hydrocarbons
includes
operating the production wells in production mode.
[0111] In one implementation, the production of the heavy hydrocarbons
includes
operating the fluid injection well and the production well of each of the well
pairs of the
array in production mode.
[0112] In one implementation, the interwell communication zone extends along
substantially the entire length of the horizontal portions of each of the well
pairs.
[0113] In one implementation, the process includes providing at least one
infill well
positioned in between two adjacent well pairs.
Date Recue/Date Received 2022-07-19
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[0114] In one implementation, the process includes establishing fluid
communication
between the mobilized chambers and the at least one infill well thereby
fluidly connecting
the infill well with the interwell communication zone.
[0115] In one implementation, the process includes converting the infill well
into the well
where the oxidizing gas is injected.
[0116] In one implementation, the combustion front is swept across the array
of well pairs by
operating the at least one infill well downstream of the combustion front in
production mode
while the combustion front advances there-toward and restricting each of the
at least one
infill well once the combustion front respectively reaches each of the at
least one infill well.
[0117] In one implementation, each of the at least one infill well is operated
in shut-in or
choked mode once the combustion front respectively reaches each of the at
least one infill
well.
[0118] In one implementation, each of the at least one infill well is operated
in shut-in or
choke mode to help achieve pressurization of the interwell communication zone.
[0119] In one implementation, the production of the heavy hydrocarbons
includes
operating each of the at least one infill well in production mode.
[0120] In one implementation, a single well is used as the well where the
oxidizing gas is
injected.
[0121] In one implementation, the well where the oxidizing gas is injected is
on one end of
the interwell communication zone.
[0122] In one implementation, the well where the oxidizing gas is injected is
an injection
well of an outside one of the well pairs.
[0123] In one implementation, the combustion front displaces from one end of
the interwell
communication zone over the array of well pairs to the opposed end of the
interwell
communication zone.
[0124] In one implementation, the combustion front displaces across the array
of well pairs
in a direction perpendicular with respect to the well pairs.
Date Recue/Date Received 2022-07-19
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[0125] In one implementation, the production of the heavy hydrocarbons is
performed so
as to establish fluid communication between the interwell communication zone
and the at
least one infill well.
[0126] In one implementation, the interwell communication zone has a bitumen
saturation
of from about 0.20 to less than about 0.05.
[0127] In one implementation, the oxidizing gas injection well injects air at
an injection flux
of about 0.3 to about 1.2 m3(ST)/m2.hour.
[0128] In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
[0129] In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[0130] In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[0131] In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[0132] In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
[0133] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof. In another optional
aspect, the
oxidizing gas further includes CO2, recovered flue gases from a previous
combustion
sequence, and/or N2.
[0134] In one implementation, the oxidizing gas further includes water.
[0135] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
[0136] In one implementation, the oxidizing gas is air.
.. [0137] In another aspect, there is provided a process for in situ
combustion in a mature
Steam-Assisted Gravity Drainage (SAGD) operation in an underground reservoir,
the
mature SAGD operation including well pairs, at least one infill well
positioned in between
two adjacent well pairs and an interwell communication zone between the well
pairs and
the at least one infill well, wherein the process includes:
Date Recue/Date Received 2022-07-19
17
injecting an oxidizing gas through the at least one infill well to initiate
combustion and
promote mobilization of residual heavy hydrocarbons in the reservoir; and
producing the heavy hydrocarbons from at least one of the wells.
[0138] In one implementation, a combustion region having a combustion front
forms upon
injecting the oxidizing gas through the at least one infill well, the
combustion region being
at least partially sustained by the residual hydrocarbons in the reservoir.
[0139] In one implementation, the mobilization of residual heavy hydrocarbons
in the
reservoir is achieved by displacement of the combustion front from the at
least one infill
well in direction of the adjacent well pairs and then through the interwell
communication
zone, followed by pressurization of the interwell communication zone.
[0140] In one implementation, the well pairs downstream of the combustion
front are
operated in production mode while the combustion front advances there-toward,
and each
of the well pairs is restricted once the combustion front respectively reaches
each of the
well pairs.
[0141] In one implementation, each well pair includes a fluid injection well
and a
production well, and both the injection well and the production well of each
well pair are
operated in production mode while the combustion front advances there-toward.
In another
optional aspect, both the injection well and the production well of each well
pair are
operated in shut-in or choked mode once the combustion front respectively
reaches each
of the well pairs.
[0142] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of heat there-through.
[0143] In one implementation, the restricting of each of the well pairs is
performed upon
breakthrough of combustion gas there-through.
[0144] In one implementation, pressurization is achieved by operating the well
pairs in
shut-in or choke mode.
[0145] In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
Date Recue/Date Received 2022-07-19
18
[0146] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[0147] In one implementation, the oxidizing gas further includes CO2,
recovered flue gases
from a previous combustion sequence, and/or N2.
[0148] In one implementation, the oxidizing gas further includes water.
[0149] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
[0150] In one implementation, the oxidizing gas is air.
[0151] In a further aspect, there is provided a process for in situ combustion
in a SAGD
operation in an underground reservoir, the SAGD operation including well pairs
and
mobilized chambers within the reservoir extending from corresponding well
pairs, wherein
after establishing fluid communication between the mobilized chambers to
create an
interwell communication zone, the process includes repeatedly executing the
following
sequence of steps:
initiating combustion by injecting an oxidizing gas through at least one well
of the
well pairs so as to promote mobilization of residual heavy hydrocarbons in the
reservoir;
ceasing gas injection through the at least one well; and
producing the heavy hydrocarbons from at least one of the wells.
[0152] In one implementation, each well pair includes a fluid injection well
and a
production well, and the fluid injection well of one of the well pair is used
to inject the
oxidizing gas.
[0153] In one implementation, a combustion region having a combustion front
forms upon
injecting the oxidizing gas, the combustion region being at least partially
sustained by the
residual hydrocarbons in the reservoir.
[0154] In one implementation, the mobilization of residual heavy hydrocarbons
in the
reservoir is achieved by displacement of the combustion front from the well
where the
oxidizing gas is injected through the interwell communication zone, followed
by
pressurization of the interwell communication zone.
Date Recue/Date Received 2022-07-19
19
[0155] In one implementation, the production well of the well pair including
the oxidizing
gas injection well is operated in shut-in or choked mode while injecting the
oxidizing gas
through the oxidizing gas injection well.
[0156] In one implementation, the production well of the well pair including
the oxidizing
gas injection well is operated in shut-in mode as long as the oxidizing gas is
injected
through the oxidizing gas injection well.
[0157] In one implementation, the well pairs downstream of the combustion
front are
operated in production mode while the combustion front advances there-toward,
and each
of the well pairs is restricted once the combustion front respectively reaches
each of the
well pairs.
[0158] In one implementation, both the injection well and the production well
of each well
pair are operated in production mode while the combustion front advances there-
toward.
[0159] In one implementation, both the injection well and the production well
of each well
pair are operated in shut-in or choked mode once the combustion front
respectively
reaches each of the well pairs.
[0160] In one implementation, the restricting of each of the well pairs is
preformed upon
breakthrough of heat there-through.
[0161] In one implementation, the restricting of each of the well pairs is
performed upon
breakthrough of combustion gas there-through.
.. [0162] In one implementation, pressurization is achieved by operating the
well pairs in
shut-in or choke mode.
[0163] In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
[0164] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[0165] In one implementation, the oxidizing gas further includes CO2,
recovered flue gases
from a previous combustion sequence, and/or N2.
[0166] In one implementation, the oxidizing gas further includes water.
[0167] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
Date Recue/Date Received 2022-07-19
20
[0168] In one implementation, the oxidizing gas is air.
[0169] In a further aspect, there is provided a process for in situ combustion
in a SAGD
operation in an underground reservoir, the SAGD operation including well pairs
and
mobilized chambers within the reservoir extending from corresponding well
pairs, wherein
after establishing fluid communication between the mobilized chambers to
create an
interwell communication zone, the process includes:
initiating combustion by injecting an oxidizing gas through at least one well
of the
well pairs so as to promote mobilization of residual heavy hydrocarbons in the
reservoir;
ceasing gas injection through the at least one well; and
producing the heavy hydrocarbons from the at least one well.
[0169a] In a further aspect, there is provided a process for recovering
bitumen from an
underground reservoir provided with well pairs wherein each well pair includes
an injection
well above a production well, the process including:
a start-up phase including introducing a solvent via the injection well of at
least
one well pair to establish communication between the injection well and the
production
well of the at least one well pair;
a production phase including injecting a solvent to recover heavy hydrocarbons
from the reservoir and form an interwell communication zone between the well
pairs; and
an in situ combustion phase including injecting an oxygen containing gas into
the
injection well or the production well of at least one well pair to initiate
combustion and
promote mobilization of residual heavy hydrocarbons in the reservoir, and
recovering
mobilized residual hydrocarbons from the reservoir.
[0169b] In one implementation, the production phase is operated until the
interwell
communication zone reaches maturity.
[0169c] In one implementation, the process further includes supplying an
external heat
source to the oxygen containing gas to promote combustion.
[0169d] In one implementation, the external heat source includes a heater in
the well
through which the oxygen containing gas is injected.
Date Recue/Date Received 2022-07-19
21
[0169e] In one implementation, the heater includes a wall heater disposed in
the well.
[0169f] In one implementation, in the start-up phase, the solvent is injected
via the injection
well.
[0169g] In one implementation, in the start-up phase, the solvent is
circulated via the
.. injection well.
[0169h] In one implementation, in the in situ combustion phase, the oxygen
containing gas
is injected via the injection well.
[0169i] In one implementation, the production phase includes injecting a
mixture of steam
and solvent into the reservoir to mobilize bitumen.
[0169j] In one implementation, the interwell communication zone has a bitumen
saturation
of from about 0.20 to about 0.05.
[0169k] In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
[01691] In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[0169m] In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[0169n] In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[01690] In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
[0169p] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[0169q] In one implementation, the oxidizing gas further includes CO2,
recovered flue
gases from a previous combustion sequence, and/or N2.
Date Recue/Date Received 2022-07-19
22
[0169r] In one implementation, the oxidizing gas further includes water.
[0169s] In one implementation, the oxidizing gas is oxygen or air or a
combination thereof.
[0169t] In one implementation, the oxidizing gas is air.
[0169u] In one implementation, the oxygen containing gas is injected via the
injection well
and the process includes operating the production well of the well pair
including the
injection well where the oxidizing gas is injected in shut-in or choked mode
as long as the
oxidizing gas is injected.
[0169v] In one implementation, the production well is operated in shut-in mode
as long as
the oxidizing gas is injected.
[0169w] In one implementation, both the injection well and the production well
have a
horizontal portion, the horizontal portion of the production well being
positioned below and
aligned with the horizontal portion of the injection well, allowing for
gravity drainage
recovery of the heavy hydrocarbons.
[0169x] In one implementation, the oxidizing gas is injected through a well
which is on one
end of the interwell communication zone.
[0169y] In one implementation, the initiation of combustion is followed by the
formation of a
combustion front which displaces from one end of the interwell communication
zone over
the array of well pairs to the opposed end of the interwell communication
zone.
[0169z] In one implementation, the combustion front displaces across the array
of well
pairs in a direction perpendicular with respect to the well pairs.
[0169a'] In a further aspect, there is provided a process for recovering
bitumen from an
underground reservoir provided with well pairs, each pair including an
injection well and a
production well, the process including:
a production phase including injecting a solvent to recover bitumen from the
reservoir and forming an interwell communication zone between the well pairs;
and
an in situ combustion phase including injecting an oxygen containing gas into
the
injection well of at least one well pair to initiate combustion in the
interwell communication
Date Recue/Date Received 2022-07-19
23
zone and promote mobilization of residual heavy hydrocarbons in the reservoir,
wherein
the injection well is provided with a heater to promote combustion.
[0169b1 In one implementation, the heater includes a wall heater disposed in
the injection
well.
[0169c1 In one implementation, the production phase includes injecting a
mixture of steam
and solvent into the reservoir to mobilize bitumen.
[0169d1 In one implementation, the interwell communication zone has a bitumen
saturation of from about 0.20 to about 0.05.
[0169e1 In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
[0169f1 In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[0169g1 In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[0169h1 In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[0169i1 In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
[0169j1 In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[0169k1 In one implementation, the oxidizing gas further includes CO2,
recovered flue
gases from a previous combustion sequence, and/or N2.
[016911 In one implementation, the oxidizing gas further includes water.
[0169m1 In one implementation, the oxidizing gas is oxygen or air or a
combination
thereof.
Date Recue/Date Received 2022-07-19
24
[0169n1 In one implementation, the oxidizing gas is air.
[016901 In one implementation, the process includes operating the production
well of the
well pair including the injection well where the oxidizing gas is injected in
shut-in or choked
mode as long as the oxidizing gas is injected.
[0169p1 In one implementation, the production well is operated in shut-in mode
as long as
the oxidizing gas is injected.
[0169q1 In one implementation, both the injection well and the production well
have a
horizontal portion, the horizontal portion of the production well being
positioned below and
aligned with the horizontal portion of the injection well, allowing for
gravity drainage
.. recovery of the heavy hydrocarbons.
[0169r1 In one implementation, the oxidizing gas is injected through a well
which is on one
end of the interwell communication zone.
[0169s1 In one implementation, the initiation of combustion is followed by the
formation of
a combustion front which displaces from one end of the interwell communication
zone over
the array of well pairs to the opposed end of the interwell communication
zone.
[0169t1 In one implementation, the combustion front displaces across the array
of well
pairs in a direction perpendicular with respect to the well pairs.
[0169u1 In a further aspect, there is provided a process for in situ
combustion in a mature
hydrocarbon recovery operation in an underground reservoir, the mature
hydrocarbon
.. recovery operation including an array of well pairs where each well pair
includes an
injection well above a production well, and an interwell communication zone
between the
well pairs, the process including:
injecting an oxidizing gas into the injection well of at least one well pair
to initiate
combustion and promote mobilization of residual heavy hydrocarbons in the
reservoir; and
producing the residual heavy hydrocarbons either through both the injection
well
and the production well of an adjacent well pair of the well pair including
the injection well
where the oxidizing gas is injected, or through one of the injection well or
the production
well of the adjacent well pair while the other well of the adjacent well pair
is shut in.
Date Recue/Date Received 2022-07-19
25
[0169v1 In one implementation, the residual heavy hydrocarbons are produced
through
both the injection well and the production well of the adjacent well pair.
[0169w1 In one implementation, the injection well is provided with a heater to
promote
combustion.
[0169x1 In one implementation, the heater includes a wall heater disposed in
the injection
well.
[0169y1 In one implementation, the interwell communication zone has a bitumen
saturation
[0169z1 In one implementation, the interwell communication zone has a porosity
between
about 0.30 to 0.35.
[0169a1 In one implementation, the interwell communication zone has a
temperature of at
least about 150 C upon initial injection of the oxidizing gas.
[0169b"] In one implementation, the interwell communication zone has a
temperature of at
least about 175 C upon initial injection of the oxidizing gas.
[0169c1 In one implementation, the interwell communication zone has a
temperature of at
least about 200 C upon initial injection of the oxidizing gas.
[0169d1 In one implementation, the oxidizing gas is oxygen, air, enriched air,
a mixture
steam/air or a mixture thereof.
[0169e] In one implementation, the oxidizing gas further includes additional
components
including methane or fuel gas or a combination thereof.
[01691] In one implementation, the oxidizing gas further includes CO2,
recovered flue
gases from a previous combustion sequence, and/or N2.
[0169g1 In one implementation, the oxidizing gas further includes water.
[0169h1 In one implementation, the oxidizing gas is oxygen or air or a
combination
thereof.
Date Recue/Date Received 2022-07-19
26
[0169i"] In one implementation, the oxidizing gas is air.
[0169j"] In one implementation, the process includes operating the production
well of the
well pair including the injection well where the oxidizing gas is injected in
shut-in or choked
mode as long as the oxidizing gas is injected.
[0169k"] In one implementation, the production well is operated in shut-in
mode as long as
the oxidizing gas is injected.
[0169I"] In one implementation, both the injection well and the production
well have a
horizontal portion, the horizontal portion of the production well being
positioned below and
aligned with the horizontal portion of the injection well, allowing for
gravity drainage
recovery of the heavy hydrocarbons.
[0169m"] In one implementation, the oxidizing gas is injected through a well
which is on
one end of the interwell communication zone.
[0169n"] In one implementation, the initiation of combustion is followed by
the formation of
a combustion front which displaces from one end of the interwell communication
zone over
the array of well pairs to the opposed end of the interwell communication
zone.
[016901 In one implementation, the combustion front displaces across the array
of well
pairs in a direction perpendicular with respect to the well pairs.
[0170] It should also be understood that many of the above implementations can
be used
in combination with one another.
BRIEF DESCRIPTION OF THE DRAWINGS
[0171] Figs la to lc are transverse front view schematics representing the
formation
stages of an interwell communication zone between mobilized chambers of
adjacent
SAGD well pairs within an underground reservoir according to steps a) to c) of
one
implementation of the process.
[0172] Figs 2a to 2d are transverse front view schematics representing the in
situ
combustion sweep, pressure-up and blowdown phases in the interwell
communication
zone according to steps d) to h) of one implementation of the process.
Date Recue/Date Received 2022-07-19
27
[0173] Fig 3a to 3d are transverse front view schematics representing the in
situ
combustion sweep, pressure-up and blowdown phases in the interwell
communication
zone according to steps d) to h) of another implementation of the process.
[0174] Figs 4a, 4b and 4c are transverse front view schematics representing
example
configurations of arrays of four well pairs that can be used according to
another
implementation of the process.
[0175] Figs 5a to 5d are transverse front view schematics representing the in
situ
combustion sweep, pressure-up and blowdown phases in the interwell
communication
zone of the coalesced steam chambers of SAGD well pairs and an infill well
provided in
between the SAGD well pairs in an underground reservoir according to steps d)
to h) of
another implementation of the process.
[0176] Figs 6a to 6d are transverse front view schematics representing the in
situ
combustion sweep, pressure-up and blowdown phases in the interwell
communication
zone of the coalesced steam chambers of SAGD well pairs and an infill well in
an
underground reservoir according to steps d) to h) of another implementation of
the
process.
[0177] Figs 7a to 7d are transverse front view schematics representing the
formation
stages of an interwell communication zone between mobilized chambers of an
array of
SAGD well pairs and the addition of a plurality of infill wells and their
fluid communication
with the interwell communication zone in an underground reservoir according to
another
implementation of the process.
[0178] Figs 8a to 8d are top view schematics representing the formation stages
of an
interwell communication zone between mobilized chambers of an array of SAGD
well pairs
and an in situ combustion sweep within the interwell communication zone in an
underground reservoir according to one implementation of the process.
[0179] Fig 9 is a schematic section view of a laboratory experimental
combustion tube
showing the locations of core centerline, wall thermocouples and wall heaters.
[0180] Fig 10 is a simplified schematic of an experimental combustion tube set-
up.
[0181] Fig 11 represents the core temperature profiles observed in the
combustion tube of
Fig 9 during the laboratory experimental combustion.
Date Recue/Date Received 2022-07-19
28
[0182] While the process will be described in conjunction with examples of
implementations, one will understand that these examples are not intended to
limit the
scope of the technology to these implementations.
DETAILED DESCRIPTION
[0183] The present technology provides an in situ process for recovering heavy
hydrocarbons from an underground reservoir. By heavy hydrocarbons, it is meant
heavy
crude oils or bitumen, Le. petroleum or petroleum-like liquids or semisolids
occurring
naturally in porous and fractured media. Bitumen deposits are also called tar
sand, oil
sand, oil-impregnated rock, bituminous sand and the like. In the following
detailed
description, the terms heavy hydrocarbons, oil/bitumen and bitumen will be
used
interchangeably. In some implementations, the in situ combustion process is
performed in
a bitumen containing reservoir.
[0184] In the first step, the process provides an array of well pairs for
gravity controlled
recovery of heavy hydrocarbons. Each well pair includes a fluid injection well
having a
horizontal portion and a production well having a horizontal portion
positioned below and
aligned with the horizontal portion of the injection well. It should be
understood that the
horizontal portions of the injection and production wells can have varying
inclinations along
their trajectory depending on the reservoir characteristics and the in situ
process used to
recover the hydrocarbons from the reservoir. In one implementation, the well
pairs have a
configuration for performing a SAGD operation. It should also be noted that
the well pairs
can be configured and operated to perform a number of other in situ recovery
processes
during their lifetime whereby other mobilizing fluids are injected into the
reservoir such as
hot water, solvents, steam and mixtures thereof.
[0185] At least two well pairs are used in the process. However, for the
purpose of
illustrating the process, reference will be made to three well pairs as shown
in Figs 1 to 3,
four well pairs as shown in Fig 4, two well pairs and an infill well as shown
in Figs 5 and 6,
and 5 well pairs as shown in Figs 7 and 8.
[0186] Referring to Fig la, there is shown an underground reservoir 10
provided with three
well pairs 12. Each well pair 12 includes a fluid injection well 20, 22, 24
having a horizontal
portion and a production well 30, 32, 34 having a horizontal portion
positioned below and
aligned with the horizontal portion of the injection well. The horizontal
portions of the
Date Recue/Date Received 2022-07-19
29
injection and production wells are connected to vertical portions (not
illustrated) which
extend to the surface where they are used to inject fluids underground or
recover the
produced fluids for further processing.
[0187] In the second and third steps of the process, as illustrated in Fig lb
as well as in
Figs 7a and 8a, the array of adjacent well pairs 12 is operated to inject
steam or another
mobilizing fluid via the injection wells 20, 22, 24 and to produce
hydrocarbons from the
production wells 30, 32, 34, thereby forming mobilized chambers 14 within the
reservoir
extending from each well pair 12. Fluid communication is then established
between the
mobilized chambers 14 of adjacent well pairs 12 to create an interwell
communication
zone 16 which is shown in Fig lc and also in Figs 2a to 2d, 3a to 3c, 5a to
5d, 6a to 6c, 7b
to 7d and 8b to 8d. In one implementation, the start-up phase includes
injection or
circulation of hot water, steam or solvent into the injection well such that
fluid
communication is established in between the injection well and production
well. The
processing is then ramped up as steam is injected into the bitumen baring
formation
through the fluid injection well 20, 22, 24 and production fluid including
heated mobilized
bitumen and condensate is recovered from the lower parallel-running horizontal
production
well 30, 32, 34 respectively. What has been called a mobilized steam chamber
14 is
developed, upward and outward from each well pair. As steam flows toward the
perimeter
of the chamber 14, it encounters the lower temperature of the formation and
condenses,
.. causing heating and mobilization of the heavy hydrocarbons which drain
downwardly with
the condensate toward the production well. In this way heat is transferred to
the bitumen,
causing the bitumen to warm up to the point of mobilization or flow ability,
preferably under
gravity control. Eventually, both the bitumen and steam condensate are
recovered from
the formation through the production well 30, 32, 34 located below the steam
injection well
20, 22, 24. As the heated and mobilized bitumen drains down, fresh bitumen
becomes
exposed at an extraction interface that is subsequently heated by the ongoing
steam
contact and its condensation. The continuous drainage of bitumen from the
formation
results in the steam filled bitumen depleted extraction chamber growing toward
the top of
the formation and then spreading sideways over time. This chamber is called a
SAGD
.. steam chamber, a gravity drainage chamber or a mobilized chamber. In time,
continuously
injecting steam into the chambers leads to expanding the mobilized chambers to
the point
of establishing fluid communication between the mobilized chambers of adjacent
well pairs
Date Recue/Date Received 2022-07-19
30
and creates an interwell communication zone 16. In other words, the chambers
14
coalesce to form a larger chamber where the well pairs 12 are in fluid
communication with
each other. Referring to Fig 7b, the interwell communication zone 16
preferably includes
the individual mobilized chambers 14 of the entire array of SAGD well pairs
12. In typical
SAGD operation, the interwell communication zone can usually have a porosity
of between
about 0.30 to about 0.35. More regarding the interwell communication zone 16
will be
described herein-below in reference to Figs 8a-8d. When SAGD operation reaches
the
economic limit, usually when bitumen recovery factor is at least 50% of the
original
bitumen in place or SAGD recoverable reserve, steam injection is terminated.
One can
then say that the SAGD operation is mature. The temperature in the mature SAGD
chambers is generally around about 190 C to about 257 C, which is based on
the SAGD
operating pressure from 1300kPa to 4500kPa. However, a temperature of at least
above
150 C, and even more preferably above 200 C, is favourable for the next
steps of the
process including initiating in situ combustion in the mature SAGD chamber.
Furthermore,
residual hydrocarbons are still present in and around the mobilized chambers
after SAGD
operation, which will also favour combustion. In another optional aspect, the
bitumen
residual saturation in a mature SAGD chamber can be about 0.20 to less than
about 0.05.
[0188] Referring to Figs 2a to 2d, there is shown the following steps of the
process and
more particularly those steps which allow recovering further oil/bitumen from
the
underground reservoir 10. As more particularly shown in Fig 2a, an oxidizing
gas, e.g.
oxygen or air, preferably air for availability and economic reasons is
injected through a
well, preferably through one of the fluid injecting wells 20 into the mature
interwell chamber
16. Even though air is preferably injected in the process, it is also possible
to inject other
gases such as methane (e.g. pipelined methane), fuel gas (e.g. fuel gas from
steam
boiler), pure oxygen or enriched air (e.g. an oxygen concentration above 21%)
as oxidizing
gas and it is also possible to inject or co-inject additional gases at various
steps of the
process such as CO2 or N2, recovered flue gases from a previous combustion
cycle, and
the like. A mixture of water and air could also be used. Injection of a
mixture steam/air is
also possible. In this latter case, the mole ratio of air to steam in this
mixture is preferably
.. more than 2%.
[0189] In another optional aspect, the air injection rate is based on the
value of air
required and of the minimum air flux to sustain in situ combustion. The
minimum air flux is
Date Recue/Date Received 2022-07-19
31
dependent upon the formation thickness, well length and well spacing. The
injection rate is
also dependent on the operating pressure and reservoir pressure. For example,
for a
typical SAGD well configuration and Athabasca bitumen formation, this rate can
be
estimated to be around 10,000 m3(ST)/day/well to 100,000 m3(ST)/day/well. In
one
implementation, the oxidizing gas injection flux can be about 3 to about 1.2
m3(ST)/m2.hour.
[0190] While in some implementations, one of the existing wells can be
converted into the
oxidizing gas injection well, it is also possible to provide an additional
well, which can be
vertical or horizontal, as the oxygen injection well. Due to the high
temperature in the
chamber and the presence of residual hydrocarbons, ignition occurs
spontaneously and a
combustion region forms around injecting well 20. It is worth noting that even
though
ignition is generally spontaneous, it would also be possible to initiate
combustion through
introduction of a source of ignition at the injection well. It is also
possible to promote initial
combustion by injecting a high oxygen content gas and then gradually scaling
back oxygen
content to the composition of air. At this step of initiating combustion, the
producer well 30
below the converted oxidizing gas injection well 20 is shut in while all the
other wells
(injectors and producers) 22, 32, 24 and 34 are preferably left open in
production mode.
The combustion region is then allowed to propagate through the interwell
communication
zone 16 encouraged in the direction of adjacent well pairs of the array as a
result of
pressure differential between the air injector 20 and the open wells 22, 32,
24 and 34.
Injection of oxidizing gas is continued and when the first breakthrough of
heat, combustion
flue gases occurs at wells 22 and 32, or in response to another detected
process
parameter, these wells are restricted by choking or shutting in. For example,
referring to
Fig 2b, the well 22 is shut in upon arrival of the combustion front, while the
downstream
wells 24 and 34 are kept open to continue encouraging the combustion front to
progress
further along the interwell chamber 16. The timed restriction of the wells
causes the
advancing combustion front from prematurely breaking through and enables a
continued
advancement of the combustion across more of the interwell chamber. The
combustion
front is redirected toward the remaining open wells 24 and 34. In this way,
the well pairs
are operated such that each subsequent downstream well is choked or shut in
upon arrival
of the combustion front thus promoting the advancement of the combustion
across and
throughout the interwell region. Once the oxygen/combustion front is close to
the last well
Date Recue/Date Received 2022-07-19
32
pair, wells 24 and 34 in Fig 2c for example, the restriction procedure is
applied to these
wells. Fig 2c shows all wells being shut in except for the air injection well.
Continuing air
injection causes the reservoir pressure to rise till a desired pressure value.
Then, air
injection is terminated and that well can also be shut in. The pressure-up
shut-in time can
be provided to allow prolonged heating of the interwell chamber. Even though
Figs 2a to
2d only shows three well pairs, it should be understood that more well pairs
could be
present in the array and in the mature interwell chamber. The pressure-up
phase could
also be implemented sequentially until all the further wells are restricted.
[0191] In one implementation, the pressure-up phase is reached by restricting
production by
either choking or shutting in wells 22, 32, 24 and 34, after oxygen or
combustion front has
arrived to these producer wells, while air is being injected. This results in
pressure rising
both in the mature SAGD chamber and its surrounding reservoir, especially in
the upswept
area. Thus, combustion front is forced to penetrate from the mature SAGD
chamber into the
adjacent portion of the reservoir which is upswept by steam and colder and
which has a
higher remaining oil/bitumen saturation. Therefore, more oxygen is consumed
rather than
flow breakthrough through the mature chamber that connected air injector 20
and wells 22,
32, 24 and 34. Thereby, more oil/bitumen is heated and eventually mobilized.
[0192] It is also worth mentioning that high energy can be released from the
combustion or
oxidation, and local combustion zone temperature can reach 300 C or more.
Flue gases
(mainly containing nitrogen and carbon dioxide) are generated as a result of
these high
temperature oxidation or combustion reactions, which displace and mobilize
residual
oil/bitumen to form oil/bitumen banks between the well pairs. Also, flue gas
occupies the void
volume which is left by the steam condensate, so as to allow gravity drainage
to
continuously take place within the mature chamber, and incremental oil/bitumen
is
recovered.
[0193] Once the desired value of chamber pressure is reached, e.g. at a
pressure below
4500 kPa, oxidizing gas or air injection is terminated. The next step of the
process
includes a blowdown/production phase. Fig 2d illustrates this phase of the
process. In one
implementation, the air injector 20 is shut in and eventually converted into a
producer.
Wells 30, 22, 32, 24, and 34 are also converted into producers in this period.
It should be
noted that depending on the reservoir conditions and oil/bitumen content as
well as the
Date Recue/Date Received 2022-07-19
33
economics of production, it can be preferred to open only the original
production wells 30,
32 and 34 at the blowdown/production stage. In some implementations, the
producers can
be opened with little or no restriction, and the heated and mobilized
oil/bitumen flows in the
channels and is collected by the producers. The blowdown/production phase is
continued
until the oil/bitumen production rate falls off to a given limit, for example
above 500 kPa
bottom hole pressure of the production wells 30, 32 and 34. At the end of the
blowdown/production phase, the oil/bitumen remaining in the mature chamber
preferably
ensures that ignition and combustion is obtained during the next oxidizing gas
injection or
pressure-up cycle.
[0194] Fig 2d shows that well 20, that is used as an oxidizing gas injection
well during the
injection cycle, can also be converted into a producer to collect flue gas and
bitumen when
blowdown/production phase is taken place. However, this well could also be
simply shut in
during blowdown/production phase and be re-used for injecting oxidizing gas or
air in the
next pressure-up phase.
[0195] In some implementations, the oxidizing injection pressure-up and
blowdown/
production sequence is repeated cyclically, for instance until the oil/bitumen
production
rate falls off to a given economic limit or until the residual bitumen in the
reservoir is
insufficient to support the initiation or adequate sweep of combustion.
[0196] In another optional aspect, the flue gases and liquids (oil/bitumen)
are produced
through the producers at the end of a cycle.
[0197] Figs 2a to 2d illustrate one possible implementation of the process
wherein a
configuration of three well pairs is used, in which steam injector 20, that is
the injector of
the well pair of one far end of the array, is converted into oxidizing gas
injector during the
pressure-up phase. In this implementation, the in situ combustion sweep is
able to
advance across the entire distance of the interwell chamber, heating and
mobilizing
residual bitumen in a continuous sweep. However, many other configurations and
operational variations could be used to implement the process. Some other
possible
configurations will be discussed hereinafter. However, the process is not
limited to these
specific examples.
[0198] In Figs 3a to 3d, for example, the steam injector of a well pair, in
between two other
well pairs, is converted into the oxidizing gas injector. Thus, air is
injected through well 22
Date Recue/Date Received 2022-07-19
34
and combustion is initiated in the vicinity of this well (Fig 3a). Well 32
below well 22 is shut
in and the combustion region is then allowed to propagate through the
interwell
communication zone 16 in the direction of adjacent well pairs as a result of
pressure
differential between the air injector 22 and the open wells 20, 30, 24 and 34.
Thus, the
combustion region moves in two opposite directions. Injection of oxidizing gas
is continued
and when the first breakthrough of heat/combustion occurs at wells 20 and 24,
and 30 and
34, these wells are restricted by choking or shutting in (see Fig 3b). Air
injection is
continued and the reservoir's pressure is allowed to rise until the desired
pressure value
(Fig 3c). Then, air injection is terminated. The pressure-up phase is then
followed by the
blowdown phase wherein all wells 20, 22, 24, 30, 32, 34, or selected wells
amongst those,
can be opened and bitumen produced (see Fig 3d). The pressure-up/blowdown
sequence
is then repeated to recover further bitumen.
[0199] Figs 4a and 4b show two other possible configurations of the well pairs
used to
implement the process according to another implementation. In this case, four
well pairs
are represented.
[0200] In Fig 4a, the injector of the first well pair from the array is used
as the air injector and
all the other wells are used as producers. Combustion is initiated in the
vicinity of the injector
while the producer just below is shut in. All the other wells are opened and
the combustion
front is allowed to propagate in the direction of the second well pair. When
the first
breakthrough of heat, combustion and/or gas occurs at the second well pair,
its wells are
restricted. Oxidizing gas or air injection is continued and the reservoir's
pressure is allowed
to rise. The combustion front is redirected toward the remaining opened wells
of the third
and fourth well pairs. Once the combustion front is close to the third well
pair, the restriction
procedure is re-applied to its wells. Continuing oxidizing gas or air
injection will allow the
combustion front to finally propagate toward the fourth well pair wherein the
wells are still
opened. Once the combustion front reaches the fourth well pair, its wells are
shut in, air
injection is continued and the reservoir's pressure is allowed to rise till
the desired pressure
value. Oxidizing gas or air injection is then terminated and the blowdown
phase is
implemented wherein all wells, or selected wells, are opened and bitumen is
produced there-
from. The pressure-up/blowdown sequence is then repeated to recover further
bitumen.
[0201] Fig 4b represents the case when air is injected through two different
wells. For
example, two steam injectors of SAGD well pairs can be converted to air
injectors in some
Date Recue/Date Received 2022-07-19
35
implementations of the process. In this example, air is injected in the steam
injector of the
first well pair of the array and in the steam injector of the third well pair.
The remaining
wells are used as producers. In this configuration, combustion is initiated
both in the
vicinity of the first and third injectors while the producer below in their
respective pair is
shut in. The first combustion front moves from the first well pair in the
direction of the
second well pair where the wells are opened. The second combustion front moves
from
the third well pair in two directions, toward the second well pair and also
toward the fourth
well pair, the wells of both these pair wells being also opened. Before the
combustion
fronts reach the second and fourth well pairs, the producers at these pairs
are shut in. Air
injection is continued to pressure-up the chamber. Then, the blowdown phase is
implemented by opening the wells and the oil/bitumen is produced.
[0202] It should also be noted that the process can be implemented by
injecting oxidizing
gas such as air through two injectors of adjacent well pairs (see Fig 4c). In
this case,
oxidizing gas such as air is injected in the steam injector of the second and
third well pair
of the array. The composition of the oxidizing gas injected through the two
wells can be the
same or different and can contain one or more of the above mentioned gases.
The
remaining wells are used as producers. In this configuration, combustion is
initiated both in
the vicinity of the second and third injectors while the producer below in
their respective
pair is shut in. A first combustion front moves from the second well pair in
the direction of
the first well pair of the array where the wells are opened. A second
combustion front
moves from the third well pair in the direction of the fourth well pair of the
array where the
wells are also opened. Before the combustion fronts reach the first and fourth
well pairs,
the producers at these pairs are shut in. Air injection is continued to
pressure-up the
chamber. Then, the blowdown phase is implemented by opening the wells and the
oil/bitumen is produced.
[0203] In another implementation, referring to Figs 5a to 5d, 6a to 6d and 7a
to 7d, one or
more infill wells can each be provided in between adjacent well pairs and can
be involved in
the in situ combustion process. Infill wells can be used to help recover
stranded bitumen
between SAGD well pairs. The infill wells can be provided by drilling a simple
horizontal well
between two existing well pairs in the bypassed zone of stranded or bypassed
bitumen.
Remaining mobilized bitumen is collected through this infill well. The process
can also be
Date Recue/Date Received 2022-07-19
36
implemented in an underground reservoir further including one or more infill
wells. One or
more of the infill wells can then be used as a producer or it could be used as
an air injector.
[0204] In Figs 5a to 5d, there is shown a two well pair configuration wherein
an infill well
40 is present in between the two pairs. The infill well 40 is used as a
producer, but it
should be understood that it can also be initially used as an injection of
steam, hot water
and/or solvent to help mobilized the surrounding bitumen. In one aspect,
combustion is
initiated at well 20, while well 30 below is shut in. In one implementation,
infill well 40 and
wells 22 and 32 can be opened at this stage (Fig 5a). The combustion front
then
propagates through the interwell chamber in the direction of infill well 40
Injection of air is
continued and before combustion front reaches the infill well 40, the latter
is restricted by
choking or shutting in (see Fig 5b). The restriction of the infill well 40
causes the
combustion front to be redirected toward the remaining opened wells 22 and 32.
Once the
combustion front is close to wells 22 and 32, the restriction procedure is re-
applied to
these wells. Continuing air injection causes the reservoir pressure to rise to
a given
pressure value (see Fig 5c). Then, air injection is terminated. The blowdown
phase is then
implemented by opening all of the wells or selected wells (see Fig 5d).
[0205] Figs 6a to 6d show another alternative wherein an infill well 40 is
used as the air
injector. In this case, the combustion region formed in the vicinity of the
infill well 40 is
allowed to move in the direction of both adjacent well pairs wherein wells 20,
30, 22, 32
are opened (see Figs 6a-6b). Injection of air is continued and before
combustion front
reaches wells 20, 30, 22, 32, these are restricted by choking or shutting in.
Oxidizing gas
or air injection is continued and the reservoir's pressure is allowed to rise
(see Fig 6c).
Then, air injection is terminated. Then follows the blowdown phase wherein all
wells or
selected wells, are opened and bitumen is collected (Fig 6d).
[0206] Referring now to Figs 7c and 7d, the SAGD array of well pairs can be
provided with
at least one infill well in between each adjacent well pair. In one
implementation, there is
one infill well in between each adjacent well pair, but there can be multiple
infill wells in
one or more cases, depending on the size of the bypassed region, the distance
in between
adjacent well pairs as well as reservoir characteristics. In one aspect,
conducting in situ
combustion heats one or more bypassed regions in which the infill wells have
not yet
established fluid communication with the coalesced mobilized chamber, e.g.,
infill wells 40'
in Fig 7d.
Date Recue/Date Received 2022-07-19
37
[0207] Referring to Figs 8a to 8d, the development of the mobilized chambers
14 and the
interwell communication zone 16 can occur in a variety of ways and the process
can be
implemented in accordance with mobilized chamber development. For instance, in
one
aspect, the in situ combustion process can be implemented once the interwell
chamber 16
covers the majority or entirety of the area above the array of well pairs.
This
implementation enables the combustion front to advance so as to remain
generally parallel
with the well pairs in a direction that is generally perpendicular with
respect to the well
pairs, as shown in Fig 8d. This promotes consistency and predictability in
operation of the
in situ combustion process. In another optional aspect, the combustion can be
conducted
while the interwell chamber has not yet completely covered the area above and
between
all well pairs, e.g. as shown in Fig 8b. In this case, the SAGD reservoir
still includes some
immobile bitumen regions 42 which are mainly located in between adjacent well
pairs. As
can be seen referring to Figs 8b and 8c, larger immobile bitumen regions 42a
can
eventually in time reduce to a smaller immobile bitumen region 42h and
eventually this
small region can be heated up resulting in sufficiently reducing the viscosity
of bitumen
and make the bitumen mobilized. In an optional aspect, the in situ combustion
can be
conducted while there are still various immobile bitumen regions 42 above and
between
the well pairs and the combustion sweeps help to heat, mobilize and reduce the
size of
these less mobile bitumen regions 42, compared to the SAGD chamber. In such
cases,
the combustion front follows a more tortuous path, which can have certain
upsides.
[0208] As described above, the process includes cyclically conducting the in
situ
combustion sweep and blowdown recovery. In one aspect, each cycle uses the
same well
as the oxygen injection well and the combustion displacement pattern is
generally similar
with each cycle. This can present various advantages, for example reducing
well
conversion requirements and having consistent combustion patterns and
development
over multiple cycles. Alternatively, different cycles can use different wells
as the oxygen
injection well. In one such scenario, a well at one end of the array is used
as the oxygen
injection well for one cycle and a well at the opposite end of the array is
used as the
oxygen injection well for a subsequent cycle. The oxidizing gas or air
injection can be
.. alternated back and forth between two wells at either end of the array. The
cycles can also
use a central well as the oxygen injection well followed by outside end well
in subsequent
cycles. Such back-and-forth or alternating oxygen injection techniques can
present
Date Recue/Date Received 2022-07-19
38
advantages by promoting different combustion sweep patterns and directions to
enhance
bitumen mobilization, improve thorough bitumen recovery from more areas of the
interwell
chamber and investigate the combustion efficiency and productivity according
to different
combustion flows.
[0209] The above description and drawings are intended to help the
understanding of
some implementations of the process. It will be apparent to one skilled in the
art that
various modifications can be made to the process.
EXAMPLES
[0210] Combustion tests were performed on a bitumen core matrix to assess the
suitability
for air injection based on enhanced oil recovery process at low bitumen
saturations in
conditions that would be encountered in a steamed region after a SAGD
operation is
mature. The core materials were taken from the native reservoir of Suncor's
Firebag
SAGD operation site, about 270 m to 310 m underground.
[0211] The Firebag reservoir bitumen-native core was packed in a combustion
tube as
illustrated in Fig 9. The core has been established residual oil saturation
around only 8.0 %
to mimic the case of residual bitumen within a SAGD chamber after SAGD
operation.
[0212] This experiment was designed to investigate the feasibility of the
process, by
showing that, using air injection, combustion can be ignited automatically,
combustion front
can be sustained, and bitumen can be recovered from a mature SAGD chamber.
[0213] The overall burning characteristics using dry air injection of the
native core-
bitumen-brine premix at reservoir pressure of 1500 kPag and reservoir
temperature of
190 C were assessed. The air and fuel requirements and other gas phase
parameters
were measured. Produced gas compositions and produced oil and water properties
were
measured to provide benchmarks for monitoring the process and field
operations.
[0214] On completion of the packing operation, the tube was sealed, insulated
and
inserted into the pressure jacket. Fig. 10 shows a simplified schematic of the
combustion
tube set-up. Table 1 gives the average properties of the composite core prior
to the test
and the fluid saturations at the start of air injection.
Date Recue/Date Received 2022-07-19
39
[0215] Table 1: Properties of initial core pack and at ignition
Permeability (darcies) Not Measured
Calculated Porosity (%) 38.9
Mass of Liquids Present (grams) Prior to Start After Inert Gas Flood
of Inert Gas (Start of Air Injection)
Flood
Oil in Core 437.3 437.3
Water in Core 3868.2 1896.8
Oil in Lines 0.0 0.0
Water in Lines 456.0 50.0
Oil in Total System 437.3 437.3
Water in Total System 4324.2 1946.8
Core Saturations (Volume %)
Oil 8.0 8.0*
Brine 68.9 33.8*
Gas 23.1 58.2*
* Core Saturations at the start of air injection are based on densities at 25
C and atmospheric pressure. They
should fairly accurately represent the core saturations at the actual
conditions of 190 C and 1500 kPag (218
psig). The gas saturation is by difference.
[0216] The experimental results indicate that the bitumen-native core can be
ignited
automatically at an initial temperature of 200 C, which is after steam
injection. The
combustion front advanced smoothly through the core. The temperature profiles
are
shown in Figure 11. The temperature response following the start of air
injection indicated
a good ignition, and shortly after the ignition, the wall heaters were set to
adiabatic control
with a temperature lag behind the centerline temperature. The combustion front
progressed stably through the core pack.
[0217] The following is a summary of the conditions and results of the
experiments:
Operating conditions:
- Core Porosity: 38.9 percent (calculated)
- Core Permeability: Not measured
- Pressure: 1500kPag (218 psig)
- Pre-heat Temperature: 190 C
Date Regue/Date Received 2022-07-19
40
- Feed Gas: Normal air (21.14 mole percent oxygen, balance nitrogen)
- Initial Injection Air Flux: 30.0 m3(ST)/m2h
- Oil Saturation: 8.0 percent
- The rest of fluid saturations are balanced with water and steam vapour.
Combustion parameters for the overall test:
- A maximum recorded peak temperature of 640 C
- An overall fuel requirement of 17.3 kg/m3
- An overall apparent atomic hydrogen to carbon ratio of 1.14.
[0218] The combustion process, occurring in this post-SAGD case, that followed
the core
ignition consumed 49.1% of the initial bitumen in place to mobilise 13.9% of
the initial oil
and effectively displaced almost all of the initial water. Residual bitumen
remained in the
unburned section of the core.
[0219] Table 2 shows the stabilized product gas compositions of the test
results. The
results show that combustion stabilization occurs following air injection into
a mature
SAGD chamber.
[0220] Table 2: Stable Product Gas Composition
Component Mole % (2.45-7.15 hours)*
CO2 14.09
CO 4.61
02 0.13
N2 80.50
CH4 0.15
C2H4 0.03
C2H6 0.05
C3H6 0.07
C3H8 0.05
C4+ 0.13
H25 0.15
H2 0.04
*Stabilized time by the front is 0.65-8.92 hours
Date Regue/Date Received 2022-07-19
