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Patent 2869600 Summary

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(12) Patent: (11) CA 2869600
(54) English Title: THERMALLY ASSISTED GRAVITY DRAINAGE (TAGD)
(54) French Title: DRAINAGE PAR GRAVITE ACTIVE THERMIQUEMENT
Status: Granted
Bibliographic Data
(51) International Patent Classification (IPC):
  • E21B 43/24 (2006.01)
(72) Inventors :
  • ROBERTS, BRUCE (Canada)
  • BEATTIE, DOUG (Canada)
  • HAMIDA, TAREK (Canada)
(73) Owners :
  • ATHABASCA OIL CORPORATION (Canada)
(71) Applicants :
  • ATHABASCA OIL CORPORATION (Canada)
(74) Agent: FIELD LLP
(74) Associate agent:
(45) Issued: 2018-05-29
(22) Filed Date: 2014-10-31
(41) Open to Public Inspection: 2016-04-30
Examination requested: 2017-10-02
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract

A method for producing bitumen or heavy oil from a reservoir, the method comprising: defining at least one lateral section of the reservoir for placement of patterns of heater wells above a producer well; placing the producer well at a substantially centered location at or adjacent to the bottom of the reservoir within each of the lateral sections; placing a triangular pattern of heater wells above the producer well; placing a regular or non-regular pentagonal pattern of heater wells, or a portion thereof, at or above the triangular pattern of heater wells; heating the reservoir with the triangular and pentagonal patterns of heater wells to conductively heat the reservoir and reduce the viscosity of the bitumen or heavy oil; and producing bitumen or heavy oil with the producer well.


French Abstract

Un procédé pour produire du bitume ou du pétrole lourd à partir dun réservoir. Le procédé consiste à définir au moins une section latérale du réservoir pour la mise en place densembles de puits chauffants au-dessus dun puits de production, et à placer ce dernier à un emplacement essentiellement centré au fond du réservoir, ou adjacent à celui-ci, dans chacune des sections latérales. Le procédé consiste également à placer un ensemble triangulaire de puits chauffants au-dessus du puits de production, à placer un ensemble pentagonal régulier ou irrégulier de puits chauffants, ou une partie de celui-ci, au niveau ou au-dessus de lensemble triangulaire de puits chauffants, à chauffer le réservoir avec les ensembles triangulaire et pentagonal de puits chauffants pour chauffer par conduction le réservoir et réduire la viscosité du bitume ou du pétrole lourd, et à produire du bitume ou du pétrole lourd avec le puits de production.

Claims

Note: Claims are shown in the official language in which they were submitted.


CLAIMS
1. A method for producing bitumen or heavy oil from a reservoir, the method
comprising:
a) defining at least one lateral section of the reservoir for placement of
patterns of
heater wells above a producer well;
b) placing the producer well at a substantially centered location at or
adjacent to the
bottom of the reservoir within each of the lateral sections;
c) placing a triangular pattern of heater wells above the producer well, the
triangular
pattern arranged with a lowermost vertex located above and substantially
aligned with
the producer well;
d) placing a regular or non-regular pentagonal pattern of heater wells above
the
triangular pattern of heater wells, the pentagonal pattern including as its
lowest side, the
heater wells of the two higher vertices of the triangular pattern;
e) heating the reservoir with the triangular and pentagonal patterns of heater
wells to
conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil; and
f) producing bitumen or heavy oil with the producer well.
2. The method of claim 1 wherein the remaining two higher vertices of the
triangular
pattern are contained within the boundaries of the lateral section at
substantially the
same level above the lowermost vertex of the triangular pattern.
3. The method of claim 1 or 2 wherein an additional heater well is placed
substantially centrally within the pentagonal pattern.
4. The method of any one of claims 1 to 3 wherein the width of the lateral
section is
between about 35 m to about 65 m.
5. The method of any one of claims 1 to 4 wherein the bitumen or heavy oil
drains
by gravity from an upper portion of the lateral section into the producer well
in a
generally triangular profile.
- 33 -

6. The method of any one of claims 1 to 5 wherein the distance between the
top of
the triangular pattern and the lowermost vertex of the pentagonal pattern is
between
about 2 m to about 20 m.
7. A method for producing bitumen or heavy oil from a reservoir, the method
comprising:
a) defining at least one lateral section of the reservoir for placement of
patterns of
heater wells above a producer well;
b) placing the producer well at a substantially centered location at or
adjacent to
the bottom of the reservoir within each of the lateral sections;
c) placing a triangular pattern of heater wells above the producer well, the
triangular pattern arranged with a lowermost vertex located above and
substantially
aligned with the producer well;
d) placing a plurality of successively elevated regular or non-regular
pentagonal
patterns of heater wells above the triangular pattern of heater wells, wherein
at least one
upper pentagonal pattern is spaced apart from an adjacent lower pentagonal
pattern and
at least one upper pentagonal pattern is arranged to share two vertices with
upper
vertices of a lower pentagonal pattern;
e) heating the reservoir with the triangular and pentagonal patterns of heater

wells to conductively heat the reservoir and reduce the viscosity of the
bitumen or heavy
oil; and
f) producing bitumen or heavy oil with the producer well.
8. The method of claim 7, wherein the two higher vertices of the triangular
pattern
are contained within the boundaries of the lateral section at substantially
the same level
above the lowermost vertex of the triangular pattern.
9. The method of claim 7 or 8, wherein an additional heater well is placed
substantially centrally within one or more of the pentagonal patterns.
10. The method of any one of claims 7 to 9, wherein the width of the
lateral section is
between about 35 m to about 65 m.
- 34 -

11. The method of any one pf claims 7 to 10, wherein the distance between
the top
of the triangular pattern and the lowermost vertex of the pentagonal pattern
is between
about 2 m to about 20 m.
12. A method for modeling the construction of an assembly of heater wells
for
thermally assisted gravity drainage of bitumen or heavy oil from a reservoir,
the method
comprising:
a) defining at least one lateral section of the reservoir for placement of
patterns of
heater wells above a producer well;
b) placing the producer well at a substantially centered location at or
adjacent to
the bottom of the reservoir within each of the lateral sections;
c) placing a triangular pattern of heater wells above the producer well, the
triangular pattern arranged with a lowermost vertex located above and
substantially
aligned with the producer well; and
d) placing successively elevated regular or non-regular pentagonal patterns of

heater wells above the triangular pattern with each pentagonal pattern
oriented with a
lower vertex substantially aligned with the producer well until an uppermost
pentagonal
pattern is placed near the upper boundary of the reservoir, wherein, if the
upper vertices
of the uppermost pentagonal pattern are found to extend above the upper
boundary, one
or more of the pentagonal patterns are rearranged to share their lower
vertices with the
upper vertices of a lower adjacent pentagonal pattern, thereby placing an
uppermost
vertex of the uppermost pentagonal pattern below the upper boundary.
13. The method of claim 12, wherein the two higher vertices of the
triangular pattern
are contained within the boundaries of the lateral section at substantially
the same level
above the lowermost vertex of the triangular pattern.
14. The method of claim 12 or 13, wherein an additional heater well is
placed
substantially centrally within one or more of the pentagonal patterns.
- 35 -

15. The method of any one of claims 12 to 13, wherein the width of the
lateral section
is between about 35 m to about 65 m.
16. The method of any one pf claims 12 to 15, wherein the distance between
the top
of the triangular pattern and the lowermost vertex of the pentagonal pattern
is between
about 2 m to about 20 m.
- 36 -

Description

Note: Descriptions are shown in the official language in which they were submitted.


CA 02869600 2014-10-31
THERMALLY ASSISTED GRAVITY DRAINAGE (TAGD)
FIELD OF THE INVENTION
[0001] The present disclosure relates generally to recovery of hydrocarbons.
More
particularly, the present disclosure relates to thermal recovery of bitumen or
heavy oil.
BACKGROUND OF THE INVENTION
[0002] As existing reserves of conventional light liquid hydrocarbons such as
light crude
oil are depleted and prices for hydrocarbon products continue to rise, new
sources of
hydrocarbons are desirable. Viscous hydrocarbons such as heavy oil and bitumen
offer
an alternative source of hydrocarbons with extensive deposits throughout the
world. In
general, hydrocarbons having an API gravity less than 22 are referred to as
"heavy oil"
and hydrocarbons having an API gravity less than 100 are referred to as
"bitumen."
Although recovery of heavy oil and bitumen present challenges due to their
relatively
high viscosities, there are a variety of processes that can be employed to
recover such
viscous hydrocarbons from underground deposits.
[0003] Many techniques for recovering heavy oil and bitumen use thermal energy
to
heat the hydrocarbons, thereby decreasing their viscosity and increasing their
mobility
within the formation. This enables the extraction and recovery of the
hydrocarbons.
Accordingly, such production and recovery processes may generally be described
as
"thermal" techniques. A steam-assisted gravity drainage (SAGD) operation is
one
thermal technique for recovering viscous hydrocarbons such as bitumen and
heavy oil.
SAGD operations typically employ two vertically spaced horizontal wells
drilled into the
reservoir. Steam is injected into the formation via the upper well, also
referred to as the
"injection well," to form a steam chamber that extends radially outward and
upward from
the injection well. Thermal energy from the steam reduces the viscosity of the
viscous
hydrocarbons, thereby enabling them to flow downward through the formation
under the
force of gravity. The mobilized hydrocarbons drain into the lower well, also
referred to as
the "production well." The hydrocarbons collected in the production well are
produced to
the surface with artificial lift techniques.
- 1 -

CA 02869600 2014-10-31
[0004] Other processes use conductor-in-conduit heat sources to mobilize the
heavy oil
and bitumen, such as the processes described in U.S. patent 7,004,247 to Cole
et al.
[0005] Other examples of hydrocarbon recovery processes are described in U.S.
Pat.
No. 7,673,681 issued on Mar. 9, 2010 to Vinegar et al., U.S. Publication No.
2011/0048717 published on Mar. 3, 2011 to Diehl et at., PCT Publication No. WO

2010/107726 published on Sep. 23, 2010 to Al-Buraik, and Canadian Patent No.
2,120,851 issued on Aug. 22, 1995 to Yu et al.
SUMMARY OF THE INVENTION
[0006] In a first aspect, the present disclosure provides a method of
producing bitumen
or heavy oil from a reservoir including: providing a heater well in a first
portion of the
reservoir; providing a producer well in a second portion of the reservoir, the
second
portion being at a greater depth than the first portion; providing a reservoir
heater in the
heater well; operating the reservoir heater to conductively heat the reservoir
and reduce
the viscosity of the bitumen or heavy oil; and producing bitumen or heavy oil
through the
producer well.
[0007] In another embodiment, the method further includes providing a
reservoir
producer heater in the producer well and operating the reservoir producer
heater to
conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil.
[0008] In another embodiment, the method further includes providing a flow
assurance
heater in the producer well and operating the flow assurance heater to
facilitate flow of
bitumen or heavy oil in the producer well.
[0009] In some embodiments, the reservoir is heated to an average temperature
of less
than 300 C.
[0010] In some embodiments, the reservoir is heated to an average temperature
of less
than 250 C.
[0011] In some embodiments, the reservoir is heated to an average temperature
of less
than 200 C.
- 2 -

CA 02869600 2014-10-31
[0012] In some embodiments, the reservoir is heated to an average temperature
of less
than the thermal cracking temperature of the bitumen or heavy oil in the
reservoir at
reservoir conditions.
[0013] In some embodiments, the reservoir is heated to a temperature less than
the
saturated steam temperature at reservoir conditions.
[0014] In some embodiments, the reservoir is heated to an average temperature
of
between about 120 C and about 160 C.
[0015] In some embodiments, the reservoir is heated to an average temperature
of
between about 135 C and about 145 C.
[0016] In some embodiments, the reservoir is a clastic reservoir.
[0017] In some embodiments, the reservoir is a carbonate reservoir.
[0018] In some embodiments, the reservoir is a dolomite carbonate reservoir.
[0019] In some embodiments, the reservoir is a limestone carbonate reservoir.
[0020] In some embodiments, the reservoir is a karsted carbonate reservoir.
[0021] In some embodiments, the reservoir is a vuggy carbonate reservoir.
[0022] In some embodiments, the reservoir is a moldic carbonate reservoir.
[0023] In some embodiments, the reservoir is a fractured carbonate reservoir.
[0024] In a further aspect, the present disclosure provides a method of
producing
bitumen or heavy oil from a reservoir including: providing a heater well in a
first portion of
the reservoir; providing a producer well in a second portion of the reservoir,
the second
portion being at a greater depth than the first portion; heating the heater
well to
conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil; and
producing bitumen or heavy oil through the producer well.
- 3 -

CA 02869600 2014-10-31
[0025] In certain embodiments, the method further includes heating the
producer well to
conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil.
[0026] In certain embodiments, the method further includes heating the
producer well to
facilitate flow of bitumen or heavy oil in the producer well.
[0027] In certain embodiments, the method further includes selecting a target
average
temperature and reducing heating of the heater well once the average
temperature of
the reservoir is substantially equal to the target average temperature to
maintain the
average temperature of the reservoir at the target average temperature without

increasing the average temperature of the reservoir.
[0028] In certain embodiments, the method further includes selecting a target
average
temperature and reducing heating of the heater well once the average
temperature of
the reservoir is substantially equal to the target average temperature to
maintain the
average temperature of the reservoir at the target average temperature without

increasing the average temperature of the reservoir, and the target average
temperature
is between about 120 C and about 160 C.
[0029] In certain embodiments, the method further includes selecting a target
average
temperature and reducing heating of the heater well once the average
temperature of
the reservoir is substantially equal to the target average temperature to
maintain the
average temperature of the reservoir at the target average temperature without

increasing the average temperature of the reservoir, and the target average
temperature
is between about 135 C and about 145 C.
[0030] In certain embodiments, the method further includes controlling
pressure during
production to prevent an increase in pressure.
[0031] In certain embodiments, the method further includes controlling
pressure during
production to prevent an increase in pressure by drawing down pressure from
the
reservoir.
[0032] In certain embodiments, the method further includes controlling
pressure during
heating to prevent an increase in pressure.
- 4 -

CA 02869600 2014-10-31
[0033] In certain embodiments, the method further includes controlling
pressure during
heating to prevent an increase in pressure by producing fluids from the
reservoir.
[0034] In a further aspect, the present disclosure provides a system for
producing
bitumen or heavy oil from a reservoir comprising: a heater well in a first
portion of the
reservoir; a producer well in a second portion of the reservoir, the second
portion being
at a depth greater than the first portion; and a heater in the heater wellbore
for heating
the reservoir.
[0035] In some embodiments, the system further includes a second heater in the

producer wellbore for heating the reservoir.
[0036] In some embodiments, the system further includes a second heater in the

producer wellbore for heating bitumen or heavy oil produced from the reservoir
to
maintain a selected viscosity of the bitumen or heavy oil in the producer
well.
[0037] In some embodiments, the heater is an electric resistance heater.
[0038] In some embodiments, the heater is an electric resistance heater cable
heater.
[0039] In some embodiments, the heater is a fluid exchange heater.
[0040] In a further aspect, the present disclosure provides a method of
producing
bitumen or heavy oil from a reservoir including conductively electrically
heating the
reservoir to lower the viscosity of bitumen or heavy oil in the reservoir,
forming a
mobilized column of bitumen or heavy oil; and producing the bitumen or heavy
oil below
the mobilized column of bitumen or heavy oil.
[0041] In some embodiments, the method further includes heating an upper
portion of
the reservoir, the upper portion of the reservoir laterally offset from the
mobilized
column.
[0042] In a further aspect, the present disclosure provides a method of
producing
bitumen or heavy oil from a reservoir comprising: a) providing a horizontal
producer well
adjacent to a lower boundary of a cross-sectional area of the reservoir and
substantially
centered between two vertical no-flow pattern boundaries within a cross-
sectional area
- 5 -

CA 02869600 2014-10-31
of the reservoir; b) providing a plurality of vertically distributed rows of
horizontal heater
wells in the reservoir above the producer well, the plurality of rows
including a first row
with a single aligned heater well substantially vertically aligned and
parallel with the
producer well and a second row above the first row including at least two
offset heater
wells laterally offset and substantially equidistant from the producer well;
c) activating the
heater wells to conductively heat the reservoir and reduce the viscosity of
the bitumen or
heavy oil; d) allowing the bitumen or heavy oil to drain by gravity into the
producer well;
and e) producing the bitumen or heavy oil with the producer well.
[0043] In some embodiments, the method further comprises providing a reservoir

producer heater in the producer well and operating the reservoir producer
heater to
conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil.
[0044] In some embodiments, the method further comprises providing a reservoir

producer heater in a vertical section of the producer well and operating the
reservoir
producer heater to facilitate flow of the bitumen or heavy oil in the producer
well
upstream to the well head.
[0045] In some embodiments, the reservoir is heated to an average temperature
of less
than the thermal cracking temperature of the bitumen or heavy oil in the
reservoir at
reservoir conditions.
[0046] In some embodiments, the reservoir is heated to a temperature less than
the
saturated steam temperature at reservoir conditions.
[0047] In some embodiments, the reservoir is heated to an average temperature
of
between about 120 C and about 160 C.
[0048] In some embodiments, the reservoir is heated to an average temperature
of
between about 135 C and about 145 C.
[0049] In some embodiments, the reservoir is a clastic reservoir.
[0050] In some embodiments, the reservoir is a carbonate reservoir.
[0051] In some embodiments, the reservoir is a dolomite reservoir.
- 6 -

CA 02869600 2014-10-31
[0052] In some embodiments, the reservoir is a limestone reservoir.
[0053] In some embodiments, the reservoir is a karsted reservoir.
[0054] In some embodiments, the reservoir is a vuggy reservoir.
[0055] In some embodiments, the reservoir is a moldic reservoir.
[0056] In some embodiments, the reservoir is a fractured reservoir.
[0057] In some embodiments, the method further comprises selecting a target
average
temperature; and reducing heating of the heater wells once the average
temperature of
the reservoir is substantially equal to the target average temperature to
maintain the
average temperature of the reservoir at the target average temperature without

increasing the average temperature of the reservoir.
[0058] In some embodiments, the target average temperature is between about
120 C
and about 160 C.
[0059] In some embodiments, the target average temperature is between about
135 C
and about 145 C.
[0060] In some embodiments, the method further comprises controlling pressure
during
production to prevent an increase in pressure due to thermal expansion of in
situ fluids.
[0061] In some embodiments, the pressure is controlled by drawing down
pressure from
the reservoir.
[0062] In some embodiments, the plurality of vertically distributed rows of
horizontal
heater wells further includes at least one additional row with a single
aligned heater well
substantially aligned with and parallel to the producer well, to keep the area
near the
producer sufficiently warm to allow drainage of the bitumen or heavy oil into
the producer
well and at least one additional row including at least two offset heater
wells laterally
offset and substantially equidistant from the producer well.
[0063] In some embodiments, the rows with a single aligned heater well
alternate with
the rows of offset heater wells.
- 7 -

CA 02869600 2014-10-31
[0064] In some embodiments, the plurality of vertically distributed rows of
horizontal
heater wells includes at least two rows with a single aligned heater well and
at least two
rows with offset heater wells.
[0065] In some embodiments, the rows with an aligned heater well alternate
with the
rows of offset heater wells.
[0066] In some embodiments, the distance between the two offset heater wells
of the
same row varies among different rows of offset heater wells.
[0067] In some embodiments, at least one row of offset heater wells includes
one offset
heater well located substantially at or adjacent to each no-flow vertical
boundary of the
cross-sectional area of the reservoir.
[0068] In some embodiments, at least one row of offset heater wells further
includes a
heater well substantially laterally aligned with the producer well, to provide
sufficient
heating to promote drainage of the bitumen or heavy oil above the producer
well.
[0069] In some embodiments, there is a repeating pattern of offset and aligned
heater
wells.
[0070] In some embodiments, the plurality of rows of heater wells includes
three rows of
heater wells with one aligned heater well row and two offset heater well rows.
[0071] In some embodiments, the three rows of heater wells follows a pattern
wherein:
the first row above the producer well includes a single aligned heater well,
the second
row above the producer well includes two offset heater wells, and the third
row above
the producer well includes two offset heater wells and a single aligned heater
well.
[0072] In some embodiments, the vertical distance between adjacent rows is
between
about 8 m to about 15 m.
[0073] In some embodiments, the distance between offset heater wells in the
same row
is between about 12 m to about 40 m.
[0074] In some embodiments, the reservoir has a thickness of about 40 m.
- 8 -

CA 02869600 2014-10-31
[0075] In some embodiments, the plurality of rows of heater wells includes
five rows of
heater wells with three aligned heater well rows and two offset heater well
rows.
[0076] In some embodiments, the five rows of heater wells follows a pattern
wherein:
the first row above the producer well includes a single aligned heater well,
the second
row above the producer well includes two offset heater wells, the third row
above the
producer well includes a single aligned heater well, the fourth row above the
producer
well includes two offset heater wells, and the fifth row above the producer
well includes a
single aligned heater well.
[0077] In some embodiments, the vertical distance between adjacent rows is
between
about 2 m to about 15 m.
[0078] In some embodiments, the distance between offset heater wells in the
same row
is between about 12 m to about 50 m.
[0079] In some embodiments, the reservoir has a thickness of about 60 m.
[0080] In some embodiments, the plurality of rows of heater wells includes six
rows of
heater wells with three aligned heater well rows and three offset heater well
rows.
[0081] In some embodiments, the six rows of heater wells follows a pattern
wherein: the
first row above the producer well includes a single aligned heater well, the
second row
above the producer well includes two offset heater wells, the third row above
the
producer well includes a single aligned heater well, the fourth row above the
producer
well includes two offset heater wells, the fifth row above the producer well
includes a
single aligned heater well, and the sixth row above the producer well includes
two offset
heater wells.
[0082] In some embodiments, the vertical distance between adjacent rows is
between
about 4 m to about 14 m.
[0083] In some embodiments, the distance between offset heater wells in the
same row
is between about 12 m to about 50 m.
[0084] In some embodiments, the reservoir has a thickness of about 80 m.
- 9 -

CA 02869600 2014-10-31
=
[0085] In some embodiments the reservoir has a thickness ranging between about
40 m
to about 80 m.
[0086] In some embodiments, the heater wells are heated by an electric
resistance
cable heater, a fluid exchange heater, hot water, steam, oil, molten salts, or
molten
metals.
[0087] In some embodiments, step c) generates gas through solution gas
evolution and
connate water vaporization to replace voidage created by step e).
[0088] In some embodiments, step d) further comprises injecting gas into a
zone
overlying the reservoir.
[0089] In a further aspect, the present disclosure provides a method for
producing
bitumen or heavy oil from a reservoir, the method comprising: a) defining at
least one
lateral section of the reservoir for placement of patterns of heater wells
above a producer
well; b) placing the producer well at a substantially centered location at or
adjacent to the
bottom of the reservoir within each of the lateral sections; c) placing a
triangular pattern
of heater wells above the producer well; d) placing a regular or non-regular
pentagonal
pattern of heater wells, or a portion thereof, at or above the triangular
pattern of heater
wells; e) heating the reservoir with the triangular and pentagonal patterns of
heater wells
to conductively heat the reservoir and reduce the viscosity of the bitumen or
heavy oil;
and f) producing bitumen or heavy oil with the producer well.
[0090] In some embodiments, the triangular pattern is arranged with a
lowermost vertex
located above and substantially aligned with the producer well and the heater
wells of
the remaining two higher vertices of the triangular pattern are contained
within the
boundaries of the lateral section at substantially the same level above the
lowermost
vertex of the triangular pattern.
[0091] In some embodiments, an additional heater well is placed substantially
centrally
within the pentagonal pattern.
[0092] In some embodiments, the width of the lateral section is between about
35 m to
about 65 m.
-10-

CA 02869600 2014-10-31
[0093] In some embodiments, the reservoir thickness is less than about 50 m
and the
pentagonal pattern includes, as its lowest side, the heater wells of the two
higher
vertices of the triangular pattern and wherein the adjacent vertices of the
pentagonal
pattern extending laterally from the lowest side are located at or adjacent to
the
boundaries of the lateral section.
[0094] In some embodiments, the pentagonal pattern is a complete regular or
non-
regular pentagonal pattern and the apex of the pentagonal pattern is
substantially
aligned with the producer well.
[0095] In some embodiments, the bitumen or heavy oil drains by gravity from an
upper
portion of the lateral section into the producer well in a generally
triangular profile.
[0096] In some embodiments, the reservoir thickness is greater than about 50 m
and the
pentagonal pattern is elevated above the triangular pattern and oriented with
its
lowermost vertex substantially aligned with the heater well.
[0097] In some embodiments, an additional heater well is placed substantially
centrally
within the pentagonal pattern.
[0098] In some embodiments, the distance between the top of the triangular
pattern and
the lowermost vertex of the pentagonal pattern is between about 2 m to about
20 m.
[0099] In some embodiments, the adjacent vertices of the pentagonal pattern
extending
laterally from the lowermost vertex are located at or adjacent to the
boundaries of the
lateral section.
[0100] In some embodiments, the pentagonal pattern is a complete pentagonal
pattern
with uppermost vertices contained within the boundaries of the lateral
section.
[0101] In some embodiments, the bitumen or heavy oil drains vertically by
gravity from
an upper portion of the lateral section into the producer well in the
pentagonal pattern
which narrows into radial inflow in the triangular pattern.
-11-

CA 02869600 2014-10-31
[0102] In some embodiments, reservoir thickness exceeds 100 m and additional
successively elevated regular or non-regular pentagonal patterns of heater
wells are
placed above the pentagonal pattern located above the triangular pattern.
[0103] In some embodiments, an additional heater well is placed substantially
centrally
within each of the pentagonal patterns.
[0104] In some embodiments, the bitumen or heavy oil drains vertically by
gravity from
an upper portion of the lateral section into the producer well which narrows
into radial
inflow in the pentagonal pattern located above the triangular pattern.
[0105] In some embodiments, at least one higher pentagonal pattern is arranged
such
that it shares two vertices with the preceding lower pentagonal pattern.
[0106] In a further aspect, the present disclosure provides a method for
producing
bitumen or heavy oil from a reservoir, the method comprising: a) dividing at
least a
portion of the reservoir into a plurality of lateral sections; b) placing a
producer well at a
substantially centered location at or adjacent to the bottom of the reservoir
within each of
the lateral sections; c) placing a triangular pattern of heater wells above
each producer
well; d) placing a regular or non-regular pentagonal pattern of heater wells,
or a portion
thereof, at or above each triangular pattern of heater wells; e) heating the
reservoir with
the triangular and pentagonal patterns of heater wells to conductively heat
the reservoir
and reduce the viscosity of the bitumen or heavy oil; and f) producing bitumen
or heavy
oil with the producer well of each lateral section.
[0107] In some embodiments, the method further comprises the step of: g)
placing a
second pentagonal pattern of heater wells, or a portion thereof, at or above
the
pentagonal pattern of heater wells placed in step d).
[0108] In some embodiments, at least one heater well of the pentagonal pattern
of
heater wells of one lateral section is shared by an adjacent pentagonal
pattern of heater
wells in an adjacent lateral section.
- 12-

[0108a] In a further aspect, the present disclosure provides a method for
producing
bitumen or heavy oil from a reservoir, the method comprising: a) defining at
least one
lateral section of the reservoir for placement of patterns of heater wells
above a producer
well; b) placing the producer well at a substantially centered location at or
adjacent to the
bottom of the reservoir within each of the lateral sections; c) placing a
triangular pattern
of heater wells above the producer well, the triangular pattern arranged with
a lowermost
vertex located above and substantially aligned with the producer well; d)
placing a
regular or non-regular pentagonal pattern of heater wells above the triangular
pattern of
heater wells, the pentagonal pattern including as its lowest side, the heater
wells of the
two higher vertices of the triangular pattern; e) heating the reservoir with
the triangular
and pentagonal patterns of heater wells to conductively heat the reservoir and
reduce
the viscosity of the bitumen or heavy oil; and f) producing bitumen or heavy
oil with the
producer well.
[0108b] In a further aspect, the present disclosure provides a method for
producing
bitumen or heavy oil from a reservoir, the method comprising: a) defining at
least one
lateral section of the reservoir for placement of patterns of heater wells
above a producer
well; b) placing the producer well at a substantially centered location at or
adjacent to the
bottom of the reservoir within each of the lateral sections; c) placing a
triangular pattern
of heater wells above the producer well, the triangular pattern arranged with
a lowermost
vertex located above and substantially aligned with the producer well; d)
placing a
plurality of successively elevated regular or non-regular pentagonal patterns
of heater
wells above the triangular pattern of heater wells, wherein at least one upper
pentagonal
pattern is spaced apart from an adjacent lower pentagonal pattern and at least
one
upper pentagonal pattern is arranged to share two vertices with upper vertices
of a lower
pentagonal pattern; e) heating the reservoir with the triangular and
pentagonal patterns
of heater wells to conductively heat the reservoir and reduce the viscosity of
the bitumen
or heavy oil; and f) producing bitumen or heavy oil with the producer well.
[0108c] In a further aspect, the present disclosure provides a method for
modeling the
construction of an assembly of heater wells for thermally assisted gravity
drainage of
bitumen or heavy oil from a reservoir, the method comprising: a) defining at
least one
- 12A -
CA 2869600 2018-01-10

lateral section of the reservoir for placement of patterns of heater wells
above a producer well;
b) placing the producer well at a substantially centered location at or
adjacent to the bottom of
the reservoir within each of the lateral sections; c) placing a triangular
pattern of heater wells
above the producer well, the triangular pattern arranged with a lowermost
vertex located above
and substantially aligned with the producer well; and d) placing successively
elevated regular or
non-regular pentagonal patterns of heater wells above the triangular pattern
with each
pentagonal pattern oriented with a lower vertex substantially aligned with the
producer well until
an uppermost pentagonal pattern is placed near the upper boundary of the
reservoir, wherein, if
the upper vertices of the uppermost pentagonal pattern are found to extend
above the upper
boundary, one or more of the pentagonal patterns are rearranged to share their
lower vertices
with the upper vertices of a lower adjacent pentagonal pattern, thereby
placing an uppermost
vertex of the uppermost pentagonal pattern below the upper boundary.
- 12B -
CA 2869600 2018-01-10

CA 02869600 2014-10-31
[0109] Other aspects and features of the present disclosure will become
apparent to
those ordinarily skilled in the art upon review of the following description
of specific
embodiments in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] Various aspects of the invention will now be described with reference
to the
figures. For the purposes of illustration, components depicted in the figures
are not
necessarily drawn to scale. Instead, emphasis is placed on highlighting the
various
contributions of the components to the functionality of various aspects of the
invention.
[0111]
Figure 1 is a schematic of a heater well and a producer well arranged in a
TAGD
pattern;
Figure 2 is a plot of viscosity as a function of temperature for Leduc
bitumen;
Figure 3 is a cross section of three adjacent identical heater well patterns
showing one arrangement of a pattern with a triangular building block and a
partial pentagonal building block with one side shared between the two
building
blocks.
Figure 4 is a cross section of three adjacent identical heater well patterns
showing a second arrangement of a pattern with a triangular building block and
a
partial pentagonal building block with separation between the two building
blocks.
Figure 5 is a cross section of three adjacent identical heater well patterns
showing a third arrangement of a pattern with a triangular building block and
a
complete pentagonal building block with separation between the building
blocks.
Figure 6 is a cross-section of a first pattern with a 60 m thick pay zone;
Figure 7 is a cross-section of a second pattern with a 40 m thick pay zone;
Figure 8 is a cross-section of a third pattern with an 80 m thick pay zone;
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CA 02869600 2014-10-31
Figure 9 is a cross-section of a reservoir divided into four lateral sections
(Sections A to D) with a pattern of heater wells located in each section in an

arrangement selected to optimize heating of available volume of each section.
Figure 10 is a plot of the bitumen production rate from a simulation of the
pattern
of Figure 6 versus time with a portion of a ramp-up stage indicated at about 3

years;
Figure 11 is a plot of temperature in the pattern of Figure 6 at 3 years;
Figure 12 is a plot of viscosity in the pattern of Figure 6 at 3 years;
Figure 13 is a plot of gas saturation in the pattern of Figure 6 at 3 years;
Figure 14 is a plot of the bitumen production rate versus time with a portion
of a
peak production stage indicated at about 7 years;
Figure 15 is a plot of temperature in the pattern of Figure 6 at 7 years;
Figure 16 is a plot of viscosity in the pattern of Figure 6 at 7 years;
Figure 17 is a plot of gas saturation in the pattern of Figure 6 at 7 years;
Figure 18 is a plot of the bitumen production rate versus time with a portion
of a
production decline stage indicated at about 10 years;
Figure 19 is a plot of temperature in the pattern of Figure 6 at 10 years;
Figure 20 is a plot of viscosity in the pattern of Figure 6 at 10 years;
Figure 21 is a plot of gas saturation in the pattern of Figure 6 of at 10
years;
Figure 22 is a plot of bitumen production rate and cumulative bitumen
production
versus time for the pattern of Figure 6;
Figure 23 is a plot of net pattern power and cumulative energy requirements
versus time for the pattern of Figure 6; and
- 14-

CA 02869600 2014-10-31
,
Figure 24 is a plot of the bitumen recovery factor and cumulative energy ratio

versus time for the pattern of Figure 6.
DETAILED DESCRIPTION OF THE INVENTION
[0112] Generally, the present disclosure provides a process, method, and
system for
recovering hydrocarbons from a reservoir. A number of possible alternative
features are
introduced during the course of this description. It is to be understood that,
according to
the knowledge and judgment of persons skilled in the art, such alternative
features may
be substituted in various combinations to arrive at different embodiments of
the present
invention.
Thermally-Assisted Gravity Drainage (TAGD)
[0113] Thermal Assisted Gravity Drainage (TAGD) is an in situ recovery process
for
production of viscous hydrocarbons such as bitumen or heavy oil. Less viscous
hydrocarbons may be produced with the bitumen or heavy oil. TAGD is applicable
to
production of bitumen or heavy oil from either clastic or carbonate
reservoirs. Carbonate
reservoirs include limestone or dolomite, and may be any combination of vuggy,
moldic,
karsted, or fractured. More generally, TAGD is applicable to any formation
wherein it is
advantageous to transfer thermal energy to the formation.
[0114] Figure 1 is a schematic of a heater well 10 and a producer well 20
(collectively
"wells") arranged in a TAGD pattern in a bitumen or heavy oil reservoir 30. As
used
herein, the reservoir 30 refers to that portion of a bitumen or heavy oil
reservoir within a
pattern as defined below (for example, any of the patterns illustrated in
Figures 3-9).
[0115] In the particular embodiment shown in Figure 1, the producer well 20 is
located
below the heater well 10 and may be located near the base of the reservoir 30.
The
heater well 10 may be between about 5 m and about 15 m above the producer well
20.
An instrument string 40 may be present within each of the wells. The
instrument string
40 may include a pressure sensor, a temperature sensor, both, or other
instruments.
[0116] The heater well 10 includes a substantially horizontal heater well
section 50 and
a substantially vertical heater well section 60 joined by a heater well heel
65. The
substantially vertical heater well section 60 joins the substantially
horizontal heater well
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CA 02869600 2014-10-31
section 50 with a wellhead (not shown). The substantially horizontal heater
well section
50 includes a heating zone 70. The heating zone 70 may have a length
substantially
equal to the length of the substantially horizontal heater well section 50. In
one
illustrative example, the heating zone 70 is about 1600 m in length. The
heater well 10 is
cased and hydraulically isolated from the reservoir 30.
[0117] A reservoir heater 80 is located in the heater well 10. The reservoir
heater 80
includes a heating section 90 for transferring thermal energy to the reservoir
30. The
heating section 90 defines the heating zone 70. In one illustrative example,
the heating
section 90 is about 1600 m in length.
[0118] The producer well 20 includes a substantially horizontal producer well
section
110 and a vertical producer well section 120 joined by a producer well heel
125. The
vertical producer well section 120 joins the substantially horizontal producer
well section
110 with a wellhead (not shown). The substantially horizontal producer well
section 110
includes a production zone 130. The producer well 20 is cased and
hydraulically isolated
from the reservoir 30 except at the production zone 130. The producer well 20
is
completed in the production zone 130 with, for example, perforations, screens,
a slotted
liner 140 or other fluid inlet in the production zone 130. An artificial lift
system, for
example a pump 150, such as a rod pump, progressing cavity pump, or electric
submersible pump, is provided in the producer well 20 to carry bitumen or
heavy oil to
the surface.
[0119] A reservoir producer heater 160 may be present in the producer well 20.
A
producer well 20 including a reservoir producer heater 160 functions as both a
producer
well 20 and a heater well 10, and is referred to below as a heater producer
well 170. The
reservoir producer heater 160 performs the same functions as the reservoir
heater 80,
providing thermal energy to the reservoir 30 along a producer heater heating
section 95.
The producer heater heating section 95 defines a producer heating zone 100.
The
producer heating zone 100 and the production zone 130 may be co-extensive. The

producer heating zone 100 may have a length substantially equal to the length
of the
substantially horizontal producer well section 110. In one illustrative
example, the
producer heating zone 100 is about 1600 m in length.
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CA 02869600 2014-10-31
[0120] A flow assurance heater 190 may be present in the vertical producer
well section
120. The flow assurance heater 190 facilitates flow of bitumen or heavy oil
within the
producer well 20 by maintaining the temperature (and thus limiting the
viscosity) of the
bitumen or heavy oil. Thermal energy output of the flow assurance heater 190
may be
uniform per unit length from the producer well heel 125 to the wellhead. The
heater
producer well 170 may include both the reservoir producer heater 160 and the
flow
assurance heater 190. A producer well 20 including the flow assurance heater
190, but
lacking the reservoir producer heater 160, is not a heater producer well 170.
[0121] Each of the reservoir heaters 80, the reservoir producer heater 160,
and the flow
assurance heater 190 (collectively "heaters") may be of any type adapted for
use in a
well. Any of the heaters may be elongate to facilitate placement in the wells.
Any of the
heaters may be an electric resistance heater, for example a mineral insulated
three-
phase heater, for example a rod heater or cable heater. The electric
resistance heater
may be capable of accommodating medium voltage levels, for example from 600 V
to
4160 V phase to phase.
[0122] Any of the heaters may be a heat exchanger that transfers thermal
energy to the
reservoir 30 by circulation of heat transfer fluid such as hot water, steam,
oil (including
synthetic oil), molten salts, or molten metals.
Heating
[0123] Thermal energy is transferred from the reservoir heater 80 or reservoir
producer
heater 160 to the reservoir 30 by conductive heating. The reservoir 30 is
heated to an
average temperature at which the viscosity of heavy oil or bitumen is low
enough for the
heavy oil or bitumen to flow by gravity to the producer well 20 or heater
producer well
170. The viscosity of bitumen or heavy oil may be lowered, for example, to
between
about 50 cP and about 200 cP.
[0124] Figure 2 is a plot of the viscosity of Leduc bitumen versus
temperature. The data
in Figure 2 was applied to a simulation prepared with a commercially-available
reservoir
simulator (Computer Modeling Group (CMG)--STARS). A significant decrease in
viscosity of Leduc bitumen occurs when the temperature of the bitumen is
increased
from 11 C to between about 120 C and about 160 C. Dead oil viscosity is
reduced from
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CA 02869600 2014-10-31
about 14 million cP at an initial reservoir temperature of 11 C to about 80 cP
at 140 C.
At 140 C, the bitumen or heavy oil is sufficiently mobile to drain downward to
the
producer well 20 or heater producer well 170 by gravity.
[0125] The reservoir heater 80 and the reservoir producer heater 160 are
operated to
transfer sufficient thermal energy to the reservoir 30 to increase the average

temperature of the reservoir 30 to a target average temperature of between
about 120 C
and about 160 C. This is done to maximize the energy efficiency of the
process, and
utilize the least amount of energy to recover the hydrocarbon effectively.
While the
reservoir 30 as a whole may average between about 120 C and about 160 C, there
may
be near heater zones 180 (See for example Figure 11) of the heater wells 10
and heater
producer wells 170 with an average temperature of up to about 250 C. The near
heater
zones 180 are modeled as one meter blocks extending along the length of the
heating
zone 70, and for a heater producer well 170, at least a portion of the
production zone
130.
[0126] TAGD may be applied to raise the average temperature of the reservoir
30 to
between about 120 C and about 160 C. An average temperature of about 140 C
provided favorable economics. At significantly lower average temperatures, for
example
about 100 C, production rates are too low to be economical. At significantly
higher
average temperatures, for example about 180 C, the resulting increase in the
production
rate does not justify the required increase in energy input required to raise
the reservoir
30 to the higher average temperature. In addition, heating the reservoir 30 to
between
about 120 C and about 160 C avoids other potentially undesirable effects
associated
with higher average temperatures, such as increased H2S or CO2 production, and
in
some cases, thermal cracking of bitumen or heavy oil.
[0127] During heating, the reservoir pressure may be monitored and controlled.

Pressure may be controlled to remain below a selected value by reducing
transfer of
thermal energy to the reservoir 30 or by producing bitumen, heavy oil, water,
vapours, or
other fluids from the reservoir 30.
-18-

CA 02869600 2014-10-31
Well Spacing
[0128] The spacing of the heater wells 10 and producer wells 20 is set to
realize the
economical production of hydrocarbons. Substantially horizontal heater well
sections 50
may be spaced as close as between about 5 m and about 40 m apart from each
other
and from substantially horizontal producer well section 110. The following
performance
metrics are relevant to optimization of the spacing of the heater wells 10 and
producer
wells 20: oil production profile (oil production rate versus time), overall
recovery factor
(fraction of original oil in place (00IP) produced), energy ratio (ratio of
energy supplied
to the reservoir 30 to the heating value of the produced bitumen or heavy
oil), and capital
cost.
[0129] The process of constructing certain embodiments of TAGD well patterns
in a
hydrocarbon-containing formation may make use of combinations of building
block
geometries, or portions thereof, some of which may be arranged in different
orientations.
In such embodiments, one building block is a triangular pattern of heater
wells which is
placed immediately above the producer well (depicted with a small triangle
symbol)
which is substantially centrally located within a repeating pattern at the
base of the
reservoir. The triangular pattern is illustrated with short-dashed lines
between the circles
representing cross sections of heater wells in each of Figures 3-5 and Figure
9. This
triangular pattern is also seen in immediately above the producer well 170 in
each of
Figures 6-8. The primary function of the triangular pattern is to ensure
proper inflow of
heated hydrocarbons into the producer well.
[0130] Also shown with short-dashed lines between the circles representing
cross
sections of heater wells in each of Figures 3-5 and Figure 9 is a pentagonal
pattern. The
pentagonal pattern is employed to minimize the number of heater wells in a two-

dimensional space and to take advantage of thermal superpositioning to achieve
a
uniform lateral temperature distribution. This second pentagonal building
block may be
provided in repeating units, and/or portion(s) thereof, in similar or
different orientations,
as described hereinbelow, for the purpose of heating the majority of a defined

longitudinal section of a reservoir. The pentagon may be laterally distorted
(i.e. non-
regular) from the equilateral (regular) pentagon geometry shown in Figures 3-5
and
Figure 9 in order to optimize drainage volume. An example of such a non-
regular
- 19 -

CA 02869600 2014-10-31
pentagon is seen, for example, in Figure 8 with two wells 10 spaced apart from
each
other by 50 m.
[0131] A series of adjacent identical cross sectional well patterns is shown
in Figure 3.
To preserve clarity, the heater wells 10 are labelled only in the left-most
pattern. Each
pattern has a producer well 170, a triangular pattern 325 of heater wells 10
located
immediately above the producer well 170 and a pentagonal pattern 330 of heater
wells
which shares its lower side with the upper side of the triangular pattern 325.
In this
particular pattern, the apex of the pentagonal pattern is a vacant space 335
where a
heater well would be located if drainage volume was desired at that location
(therefore
the pentagonal pattern is a "partial" pentagonal pattern. The triangular
pattern includes a
single aligned heater well 10, 240 (vertically aligned with the producer well
170) and two
offset heater wells, 10, 245. The pentagonal pattern includes four offset
heater wells 10,
245 and a single centrally-located aligned heater well 10, 240. The drainage
volume
provided by this overall pattern is a triangle indicated by the shaded area
340. It is also
seen that the right-most offset heater well 10, 245 of the pentagonal pattern
330 also
acts as the left-most offset heater well 10, 245 of the pentagonal pattern to
the right of
the left-most pentagonal pattern. This is an example of sharing of heater
wells between
adjacent reservoir sections. In most cases, the bottom most heater well 10,
240 would
be placed 5-8 m above the producer well, with variations depending upon the
thermal
conductivity, power output and desired pre-heating time. The triangular
building block
325 ensures that the region near the producer well remains hot, thereby
preventing a
reduction in the mobility of the bitumen as it drains into the producer well.
[0132] As the thickness of the reservoir increases, it is advantageous to add
more
heater wells 10 using the pentagonal building block 330. Generally if the
reservoir
thickness is less than 50 m, the arrangement shown in Figure 3 is employed,
wherein
the lower side of the upper pentagon pattern 330 is oriented to share a side
with the
upper side of the triangular pattern 325.
[0133] Shown in Figure 4 is another pattern which is used when the thickness
of the
reservoir exceeds 50 m. In this case, the pentagonal pattern 330 is elevated
and rotated
by 36 with respect to the orientation of the pentagonal pattern 330 of Figure
3 such that
the lowermost heater well 10 of this pattern is now an aligned heater well
240. The
- 20 -

CA 02869600 2014-10-31
,
pentagonal pattern is a partial pentagon with two upper vacancies 335. The
drainage
volume shown by the shaded area 340 has changed in shape and increased in
volume
relative to that of Figure 3.
[0134] Shown in Figure 5 is a pattern combination similar to that of Figure 4,
with the
exception that offset heater wells 10, 245 occupy the upper corners of the
pentagonal
pattern 330 at positions which are vacant in Figure 4. This has the effect of
increasing
the heat provided at upper levels of the pattern. As noted above, the initial
drainage
occurs primarily along a central column directly above the producer well 170.
With time,
the laterally positioned heater wells 10, 245, widen the thermal column (in
each of
Figures 3-5, the drainage volume is the shaded area 340.
[0135] Figures 6 to 8 are cross-sections of patterns with width and depth
dimensions
indicated. The pattern of Figure 6 is similar to the pattern of Figure 4. The
pattern of
Figure 7 is similar to the pattern of Figure 3. The pattern of Figure 8 is
similar to the
pattern of Figure 5. In each of Figures 6-8 the reservoir has a pay thickness
230 and a
pattern width 220, and is defined by a no-flow boundary 210 at each end of the
pattern
width 220. The number of heater wells 10 and their respective locations
relative to each
other and to the heater producer well 170 may be varied to account for
features of the
reservoir 30 including pay thickness 230, vertical and horizontal
permeabilities, well
length, heater power output and temperature, and cost of wells and surface
facilities.
[0136] Figure 6 is a cross section of a first pattern 200. The pattern width
220 is 50 m
and the pay zone 230 is 60 m thick. Six heater wells 10 and one heater
producer well
170 are arranged in five rows in the first pattern 200. The heater wells 10
include aligned
heater wells 240 above and substantially laterally aligned with the heater
producer well
170. The heater wells 10 also include first offset heater wells 245 above and
laterally
offset from the heater producer well 170. The heater wells 10 also include
second offset
heater wells 250 above and laterally offset from the heater producer well 170
(with one
half of a second offset heater well 250 at each no-flow boundary 210). The
second offset
heater wells 250 are laterally offset from the heater producer well 170 to a
greater extent
than the first offset heater wells 245.
- 21 -

CA 02869600 2014-10-31
[0137] The number of wells, the locations of the wells in the first pattern
200, and the
heating output of the heaters were adjusted to obtain a high net present
value. The
simulation was based on the reservoir 30 and well properties indicated in
Table 1.
TABLE 1
Property Quantity Unit
Vertical Permeability 2200 mDarcy
Horizontal Permeability 1100 m Darcy
Porosity 15 A
Pay Thickness 60 m
Pressure at the Top of Reservoir (absolute) 473 kPa
Initial Reservoir Temperature 11 C
Bitumen Saturation 88 A
Water Saturation 12 %
Irreducible Water Saturation 10 %
Dead Oil Viscosity at 11 C 14 x 106 cP
Viscosity at 140 C 80 cP
Reservoir Heater Power Output 650 W/m
Reservoir Producer Heater Power Output 150 W/m
Rock Heat Capacity at 11 C 2.41 x 106 J/m3.
C
Rock Heat Capacity at 140 C 2.88 x 106 J/m3.
C
- 22 -

CA 02869600 2014-10-31
Rock Thermal Conductivity at 11 C 4.6 W/(m=K)
Rock Thermal Conductivity at 140 C 3.7 W/(m=K)
Bottomhole Pressure (absolute) 500 kPa
[0138] For a reservoir 30 with the pay zone 230 being thinner or thicker than
the 60 m of
Figure 6, rows of wells may be respectively added or removed. Similarly, the
lateral
offset of first offset heater wells 245 or second offset heater wells 250 (or
third offset
heater wells 255 as seen in Figure 8, or any offset heater wells generally)
may be
adjusted to account for a reservoir 30 with the thickness 220 being greater or
less than
the 50 m of Figure 6.
[0139] Figure 7 is a cross section of a second pattern 260. The pattern width
220 is 40
m and the pay zone 230 is 40 m thick. Five heater wells 10 and one heater
producer well
170 are arranged in four rows. The heater wells 10 include aligned heater
wells 240, first
offset heater wells 245 and second offset heater wells 250 (with one half of a
second
offset heater well 250 at each no-flow boundary 210).
[0140] Figure 8 is a cross section of a third pattern 270. The pattern width
220 is 50 m
and the pay zone 230 is 80 m thick. Eight heater wells 10 and one heater
producer well
170 are arranged in six rows. The heater wells 10 include aligned heater wells
240, first
offset heater wells 245 and second offset heater wells 250. The heater wells
further
include third offset heater wells 255 (with one half of a third offset heater
well 255 at
each no-flow boundary 210). The third offset heater wells 255 are laterally
offset from
the heater producer well 170 to a greater extent than the second offset heater
wells 250.
[0141] Figure 9 is a schematic cross-sectional view of a reservoir of
irregular shape
divided into four sections (A-D). This view shows how different heater well
patterns may
be assembled to provide optimal drainage volumes across a reservoir. The
optimization
provides maximal drainage of the bitumen or heavy oil from the reservoir with
the
minimal number of heater wells, thereby optimizing recovery efforts in terms
of energy
and cost.
- 23 -

CA 02869600 2014-10-31
[0142] In Figure 9, a defined reservoir 400 with a boundary 410 is divided
into four
sections (Sections A-D) ranging in width between about 40 to about 60 m and a
heater
pattern is selected for each of the four sections with section boundaries 420.
In this
particular example, the first two leftmost sections (Sections A and B) have
close to the
same depth while the third Section (Section C) has less thickness and the
fourth section
(Section D) is considerably less thick. It is seen that Sections A and B have
the same
building block pattern and that the patterns of Section C and Section D are
distinct from
each other and from the patterns of Section A and B.
[0143] In placement of heater wells above the producer well, a triangular
pattern of
heater wells 325 is first placed above the producer well as indicated in
Figure 9 in an
orientation with the lower vertex oriented above the producer well and the two
higher
vertices located at the same level above the lower vertex. Then, one or more
pentagonal patterns of heater wells 330 is/are placed above the triangular
pattern,
depending upon the depth of the remaining portion of the lateral section. In
some cases
the orientation of the pentagonal pattern(s) 330 is/are altered. While not
shown in Figure
9, it is understood from Figures 3, 4, 6 and 7 that uppermost heater wells of
a
pentagonal pattern 330 may be omitted if they would extend above the desired
drainage
volume.
[0144] For the purposes of this illustration, the heater wells and producer
wells are
identified according to the section in which they are located (the heater
wells of section
A are heater wells A-1 to A-15; the heater wells of section B are heater wells
B-1 to B-
13; the heater wells of section C are heater wells C-1 to C-13; and the heater
wells of
section D are heater wells D-1 to D-6). The same convention holds for the
producer
wells which are designated A-P, B-P, C-P and D-P.
[0145] Sections A and B - In Sections A and B (Figure 9), the arrangement of
triangular 325 and pentagonal 330 patterns above their respective producer
wells A-P
and B-P is identical because the depths of reservoir Sections A and B are
similar.
However, it is seen that two of the heater wells of the pentagonal pattern of
section A
(heater wells A-6 and A-12) are shared with the adjacent pentagonal pattern of
heater
wells of section B. This sharing of heater wells provides the advantage of
requiring fewer
heater wells in section B (15 heater wells in section A vs. 13 heater wells in
section B).
- 24 -

CA 02869600 2014-10-31
,
This is advantageous because heaters are costly to produce and operate and
because it
minimizes the number of heater wells to be drilled.
[0146] Section C - Section C has a different pattern than the pattern of
Sections A and
B. This pattern is also different from other patterns described hereinabove.
Notably, the
uppermost pentagonal pattern is oriented such that its lowermost edge is
shared with the
uppermost edge of the lowermost pentagonal pattern with the two heater wells
of the
shared edge (C-8 and C-9) shared between the two pentagons. Section C
therefore
requires 13 heater wells (C-1 to C-13).
[0147] Section D - If the depth of the remaining portion of the lateral
section of the
reservoir is less than 50 m, a pentagonal pattern is arranged as shown for
Section D
with offset lower vertices of the pentagon superimposed on the upper offset
vertices of
the triangular pattern. This is similar to the pattern illustrated in Figures
3 and 6, with the
exception that the vacancy 335 shown in Figure 3 is occupied by heater well D-
6 in the
pattern of Section D. Heater wells are not required at the two lower vertices
of the
pentagon for the pattern of Section D because the pentagon shares the edge
with the
edge formed by the heater wells originating from the triangular pattern D-2
and 0-3. The
pattern of Section D also dispenses with an additional heater well at the left
boundary of
the lateral section because heater well C-12 has already been placed at that
location for
pattern C. As a result, the pattern of Section D requires only 6 heater wells.
[0148] If a given lateral section has reduced thickness relative to a
neighboring section,
the pentagonal pattern may be modified by removing some of the upper heaters.
Conductive Heating
[0149] Conductive heating provides for more uniform temperature distribution
in the
reservoir 30 relative to convective heating processes such as those dependent
on steam
injection. The greater uniformity provides greater predictability of the
temperature
distribution. As a result, a TAGD pattern may be more easily optimized for a
particular
set of reservoir conditions than a pattern for a recovery process based on
convective
heating, for example steam assisted gravity drainage (SAGD) or cyclic steam
stimulation
(CSS). The number of wells and spacing between wells may be adjusted to
account for
differences between individual reservoirs with respect to the thicknesses,
permeabilities,
- 25 -

CA 02869600 2014-10-31
pressures, temperatures, and other properties of the reservoirs, but the
presence of
obstacles does not introduce as much uncertainty as in processes based on
convective
heating.
[0150] In reservoirs having impermeable or semi-impermeable barriers, such as
shale
extending across portions of the reservoir, the vertical growth of a SAGD or
CSS steam
chamber may be impeded by the barriers. However, thermal energy transfer by
conductive heating as in the present disclosure may pass through or around the
barriers,
mitigating the impact of the barriers on production, recovery, or both.
Production
[0151] Production may be described as occurring in three general stages: a
ramp-up
stage, a peak production stage, and a production decline stage. Figures 10 to
21 are
plots of simulation data for the first pattern 200 of Figure 3 at each of the
stages wherein
the heating zones 70 and the producer heating zones 100 each extend along a
substantially horizontal well length of 1600 m. In an embodiment, the bitumen
or heavy
oil produced from the reservoir 30 is produced substantially as a liquid via
the pump 150.
In an embodiment, there is no appreciable vaporization of bitumen or heavy oil
in the
reservoir 30 or the near heater zone 180, or both.
Ramp-Up Stage
[0152] Figure 10 is a plot of the bitumen production rate versus time for the
simulation
with a portion of the ramp-up stage indicated at about 3 years. Figures 11 to
13 are
respectively plots of temperature, viscosity, and gas saturation distributions
in the
reservoir 30 with the first pattern 200 at 3 years into the simulation.
[0153] The temperature distribution ranges from about 12 C in the majority of
the
reservoir 30 to about 250 C at the near heater zones 180. During the ramp-up
stage
(from start-up to about two years of heating), significant increases in
temperature that
result in a portion of the reservoir 30 reaching the target average
temperature of
between about 120 C and about 160 C primarily occur in the vicinity of the
near heater
zones 180. The viscosity in the reservoir 30 ranges from 1000 cP or greater in
the
majority of the reservoir 30 to about 10 cP in the near heater zones 180.
Initial bitumen
production is from a relatively small volume of heated bitumen in the vicinity
of the
- 26 -

CA 02869600 2014-10-31
heater producer well 170. The gas saturation ranges from 0 in the majority of
the
reservoir 30 to about 0.4 at the lowermost aligned heater well 240 and in a
gassy-
bitumen zone 290. A mobilized column 280 of connected mobile bitumen that
connects
the aligned heater wells 240, the first offset heater wells 245, and the
producer well 20
has yet to form (Figure 16).
[0154] As time passes and the reservoir 30 is heated further, the average
temperature
of the reservoir 30 increases, the viscosity of bitumen in the reservoir 30
decreases, and
a gas chamber 300 (Figure 17) forms and expands generally upwards.
Peak Production Stage
[0155] Figure 14 is a plot of the bitumen production rate for the first
pattern 200 with a
portion of the peak production stage indicated at about 7 years. Figures 15 to
17 are
plots of temperature, viscosity, and gas saturation distributions in the
reservoir 30 at a
point 7 years into the simulation.
[0156] The average temperature in the reservoir 30 has increased relative to
the ramp-
up stage. A significant volume of bitumen is at the target average temperature
of
between about 120 C and about 160 C. As a result, a mobilized column 280 of
bitumen
has formed in the reservoir 30 above the heater producer well 170 wherein the
viscosity
of the bitumen is below 1000 cP and is about 100 cP in much of the mobilized
column
280. The aligned heater wells 240, the first offset heater wells 245, and the
heater
producer well 170 are within the mobilized column 280. A gas chamber 300
comprising
evolved solution gas and water vapor has also formed and moves upward as
bitumen
drains down to the heater producer well 170. The gas chamber 300 provides
internal
drive and voidage replacement (see below).
[0157] Continued heating increases the height and width of the mobilized
column 280
with a concurrent increase in bitumen production rate. Peak production occurs
due to a
favorable combination of pressures and viscosity when the mobilized column 280
has
reached a maximum height. The gas chamber 300 has reached a significant size
and
the aligned heater wells 240 and the first offset heater wells 245 are within
the gas
chamber 300. During the peak production stage, thermal energy output from the
heater
wells 10 or the heater producer well 170, or both, may be reduced to maintain
the target
- 27 -

CA 02869600 2014-10-31
average temperature of between about 120 C and about 160 C in the reservoir 30

without additional increase in temperature to maximize efficiency of energy
use.
Production Decline Stage
[0158] Figure 18 is a plot of the bitumen production rate for the first
pattern 200 with a
portion of the production decline stage indicated at about 10 years. Figures
19 to 21 are
plots of temperature, viscosity, and gas saturation distributions at 10 years
into the
simulation.
[0159] During the production decline stage, the majority of the reservoir 30
is at the
target average temperature of between about 120 C and about 160 C and the
majority
of the bitumen has a sufficiently low viscosity to be substantially mobile.
The gas
chamber 300 has merged with the gassy-bitumen zone 290 to form a secondary gas
cap
310. The secondary gas cap 310 includes evolved solution gas and water vapor.
An
angle 320 at which mobilized bitumen drains to the heater producer well 170
becomes
increasingly acute to the horizontal. During the production decline stage, the
reservoir
heaters 80 may be turned down to deliver less thermal energy than during
previous
stages (Figure 23), and may even be turned off (not shown). As a result, while
the near
heater zones 180 remain, the difference in temperature between the near heater
zones
180 and the majority of the reservoir 30 is less pronounced. At abandonment,
the
remaining oil-in-place is contained at near residual saturations within the
gas chamber
300, and near the base of the reservoir 30 at an angle 320 that is
unfavourably acute to
the horizontal with respect to the heater producer well 170.
Summary of Value Indicators Over Time
[0160] Figure 22 is a plot of the bitumen production rate and the cumulative
recovered
bitumen of the simulation versus time. The peak production rate of 145 m3/day
and
overall recovery after 20 years is about 69% of 00IP. The peak production rate
and
overall recovery are comparable to that observed for an average SAGD well
pair.
[0161] Figure 23 is a plot of the net pattern power and the cumulative energy
of the
simulation versus time with 650 W/m of power output to the six heater wells 10
and 150
W/m of power output to the heater producer well 170. Each of the heater wells
10 has a
1600 m long heating zone 70 and the heater producer well 170 has a 1600 m long
- 28 -

CA 02869600 2014-10-31
producer heating zone 100. The net pattern power drops and levels off when
thermal
energy output from the heater wells 10 and the heater producer well 170 is
reduced from
the above levels. Reduction in thermal energy output allows the target average

temperature of between about 120 C and about 160 C to be maintained (but not
further
increased) while using less power.
[0162] Figure 24 is a plot of the bitumen recovery factor and the cumulative
energy ratio
of the simulation versus time.
Voidage Replacement
[0163] To effectively drain hot mobilized bitumen or heavy oil, produced
volumes must
be replaced to prevent establishment of low reservoir pressures. Low reservoir

pressures may prevent economical production. Without wishing to be bound by
any
theory, the simulation indicates that voidage replacement may occur by one or
more of
at least three mechanisms.
[0164] First, evolution of solution gas from the bitumen or heavy oil.
Solubility of gas in
bitumen or heavy oil decreases significantly with increasing temperature. As
the bitumen
or heavy oil is heated, solution gas evolves from the bitumen or heavy oil.
The specific
volume of the dissolved gas component is significantly greater in the gas
phase than in
the solution phase, thus replacing some of the voidage created by production.
For
example, at 140 C and 500 kPa (absolute), the specific volume of the solution
gas
component is about 200 times greater in the gas phase than as a dissolved
component
in the liquid bitumen or heavy oil phase.
[0165] Second, vaporization of connate water in low-pressure reservoirs (for
example
shallow reservoirs). The specific volume of steam is significantly greater
than that of
liquid water. At 140 C, the specific volume of saturated steam is about 500
times greater
than that of saturated liquid water. A portion of the reservoir 30 will exceed
the saturation
temperature thus leading to the vaporization of some of the connate water
initially in
place and thus contributing to voidage replacement. The target average
temperature of
the reservoir 30 is between about 120 C and about 160 C so water may boil
where the
average temperature of the reservoir 30 is on the upper end of this range and
water will
boil in the near heater zones 180.
- 29 -

CA 02869600 2014-10-31
[0166] Third, expansion of in-place volumes. Although less significant that
the solution
gas evolution and vaporization of connate water processes noted above, some
voidage
replacement will be realized by thermal expansion of in-place hydrocarbons,
connate
water and free gas. For example, an expansion of about 10% is estimated at 140
C and
500 kPa (absolute).
Gas Injection
[0167] Gas injection into a gassy-bitumen zone 290, a gas cap (not shown), or
a gas-
bitumen transition zone (not shown) overlying the reservoir 30 at or near the
beginning
of the ramp-up stage may allow the ramp-up stage to be completed in a shorter
time
frame. In the simulation, the peak production stage began about two years
sooner with
gas injection (i.e. at about 5 years instead of about 7 years). Gas injection
provides
further drive to the gravity drainage process. Gas injection may be stopped
once the
injected gas begins to break-through to the producer well 20. A variety of non-

condensable gases may be used, including natural gas, nitrogen, carbon
dioxide, or flue
gas.
Advantages of TAGD
[0168] The TAGD recovery process has several important advantages over other
thermal processes used to recover bitumen or heavy oil (e.g. SAGD, CSS, and
hybrid
steam injection with solvent).
[0169] TAGD allows more uniform and predictable heating of a reservoir
relative to
steam injection processes. In steam injection processes, transfer of thermal
energy is
accomplished through convection in which thermal energy is carried throughout
the
reservoir by fluid flow. Transfer of thermal energy by convection is governed
by pressure
differential and the effective permeability of the reservoir. The effective
permeability may
vary by orders of magnitude within a carbonate reservoir. Low permeability
layers may
block or retard the flow of steam. Steam may also flow preferentially in
natural fractures
thus bypassing the majority of the reservoir and resulting in poor steam
conformance.
Poor steam conformance results in poor recovery and high steam-oil ratios, and

therefore in unfavourable economics.
- 30 -

CA 02869600 2014-10-31
[0170] Heat conduction is governed largely by a temperature difference and the

effective thermal conductivity of a reservoir. The effective thermal
conductivity of the
reservoir is a function of rock mineralogy, reservoir porosity, and the
saturations and
thermal conductivities of the fluids in the reservoir, including bitumen or
heavy oil, water
and gas. In general, unlike reservoir permeability, the variation of thermal
conductivity
throughout the reservoir is relatively minor and is expected to be less than
about plus or
minus 25%. The result will be a much more uniform temperature distribution
within the
reservoir.
[0171] TAGD allows more efficient use of input energy. In the SAGD recovery
process,
the temperature of a reservoir contacted by steam is determined by the
reservoir
pressure and is generally in excess of 200 C, such as about 260 C. Even higher

temperatures are reached during the higher pressure CSS processes, such as
about
330 C. By contrast, the target average temperature in TAGD is about 120 C to
about
160 C, thus requiring significantly less input energy, for comparable oil
recovery (e.g.
production rate or recovery factor, or both), than the processes based on
steam
injection.
[0172] TAGD does not require steam injection and therefore does not require
water for
steam generation. This may be an important advantage in field locations where
a source
of available water is absent or is costly to develop. The simulation indicates
that
produced water-oil ratios may be less than 0.5 m3/m3 after year 3 of
production. In
contrast, steam-based processes produce at water-oil ratios on the order of
3.0 m3/m3
(or 3:1). The initial water-oil ratio in TAGD is a function of the mobility of
water present in
the reservoir prior to heating, and may vary from reservoir to reservoir. In
addition to
lowered water use, this advantage also provides the benefit of allowing
processing
facilities for produced bitumen to be smaller, simpler in design, and less
expensive to
build.
[0173] At the target average reservoir temperature of between about 120 C and
about
160 C, little or no generation of H2S or CO2 is expected. Thus, less H2S and
less CO2 is
produced per unit of produced bitumen or heavy oil than for a typical SAGD
project.
- 31 -

CA 02869600 2014-10-31
[0174] TAGD may be used to supplement existing SAGD operations or may be used
as
a retrofit existing SAGD well bores.
[0175] In the preceding description, for purposes of explanation, numerous
details are
set forth in order to provide a thorough understanding of the embodiments.
However, it
will be apparent to one skilled in the art that these specific details are not
required. The
above-described embodiments are intended to be examples only. Alterations,
modifications and variations can be effected to the particular embodiments by
those of
skill in the art without departing from the scope, which is defined solely by
the claims
appended hereto.
[0176] Although the present invention has been described and illustrated with
respect to
preferred embodiments and preferred uses thereof, it is not to be so limited
since
modifications and changes can be made therein which are within the full,
intended scope
of the invention as understood by those skilled in the art.
- 32 -

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 2018-05-29
(22) Filed 2014-10-31
(41) Open to Public Inspection 2016-04-30
Examination Requested 2017-10-02
(45) Issued 2018-05-29

Abandonment History

There is no abandonment history.

Maintenance Fee

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Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $400.00 2014-10-31
Maintenance Fee - Application - New Act 2 2016-10-31 $100.00 2016-10-07
Maintenance Fee - Application - New Act 3 2017-10-31 $100.00 2017-09-22
Request for Examination $800.00 2017-10-02
Final Fee $300.00 2018-04-10
Maintenance Fee - Patent - New Act 4 2018-10-31 $100.00 2018-10-16
Maintenance Fee - Patent - New Act 5 2019-10-31 $200.00 2019-10-23
Maintenance Fee - Patent - New Act 6 2020-11-02 $200.00 2020-10-02
Maintenance Fee - Patent - New Act 7 2021-11-01 $204.00 2021-09-28
Maintenance Fee - Patent - New Act 8 2022-10-31 $203.59 2022-10-05
Maintenance Fee - Patent - New Act 9 2023-10-31 $210.51 2023-09-26
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
ATHABASCA OIL CORPORATION
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Abstract 2014-10-31 1 18
Description 2014-10-31 32 1,417
Claims 2014-10-31 4 115
Drawings 2014-10-31 21 1,032
Representative Drawing 2016-04-04 1 21
Cover Page 2016-05-02 2 57
Special Order / Request for Examination 2017-10-02 3 95
Special Order - Green Granted 2017-10-12 1 52
Examiner Requisition 2017-11-24 3 239
Amendment 2018-01-10 16 580
Claims 2018-01-10 4 115
Description 2018-01-10 34 1,402
Final Fee 2018-04-10 1 32
Representative Drawing 2018-05-02 1 18
Cover Page 2018-05-02 1 48
Assignment 2014-10-31 3 81
Maintenance Fee Payment 2023-09-26 1 33