Note: Descriptions are shown in the official language in which they were submitted.
CA 02883643 2015-02-27
,
,
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SYSTEM AND METHOD FOR RECOVERING BITUMEN FROM A BITUMEN RESERVE
USING ACOUSTIC STANDING WAVES
TECHNICAL FIELD
[0001] The following relates to systems and methods for recovering
bitumen from a bitumen
reserve using acoustic standing waves.
DESCRIPTION OF THE RELATED ART
[0002] Bitumen is known to be considerably viscous and does not flow
like conventional
crude oil, and can be present in an oil sand reservoir. As such, bitumen is
recovered using what
are considered non-conventional methods. For example, bitumen reserves are
typically
extracted from a geographical area using either surface mining techniques,
wherein overburden
is removed to access the underlying pay (e.g., oil sand ore-containing
bitumen) and transported
to an extraction facility; or using in situ techniques, wherein subsurface
formations (containing
the pay), e.g., oil sands, are heated such that the bitumen is caused to flow
into one or more
wells drilled into the pay while leaving formation rock in the reservoir in
place. Both surface
mining and in situ processes produce a bitumen product that is subsequently
sent to an
upgrading and refining facility, to be refined into one or more petroleum
products, such as
gasoline and jet fuel.
[0003] Bitumen reserves that are too deep to feasibly permit bitumen
recovery by mining
techniques are typically accessed by drilling wellbores into the hydrocarbon
bearing formation
(i.e. the pay) and implementing an in situ technology. There are various in
situ technologies
available, such as steam driven based techniques, e.g., Steam Assisted Gravity
Drainage
(SAGD), Cyclic Steam Stimulation (CSS), etc. SAGD and CSS typically require
horizontally
oriented wells that are drilled directionally from surface and production
equipment located at a
surface site.
[0004] For some bitumen reserves, steam driven techniques can be
considered less
desirable or less economical.
SUMMARY
[0005] In one aspect, there is provided a method for recovering
bitumen from a bitumen
reserve, the method comprising: energizing bitumen from a pay region in the
bitumen reserve
using a plurality of acoustic resonators positioned in the pay region, wherein
pairs of the plurality
of acoustic resonators generate synchronized acoustic waves at a resonant
frequency of a
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geological material in the pay region, the acoustic waves combining to
generate standing waves
within the pay region; and recovering a bitumen containing fluid from the
bitumen reserve via
gravity drainage.
[0006] In an implementation, the acoustic resonators are positioned in the
pay region via
vertically oriented wells. The plurality of acoustic resonators can also be
positioned in a pair of
horizontally oriented wells. A lower one of the pair of horizontally oriented
wells can be used to
produce the bitumen containing fluid to surface.
[0007] In another implementation, at least one additional resonant
frequency can be
determined and the plurality of acoustic resonators operated at the at least
one additional
resonant frequency.
[0008] In other implementations, solvent can be injected before, during, or
after operating
the acoustic resonators. In another implementation, steam can be injected into
the pay region
prior to operating the plurality of acoustic resonators. The steam that is
injected can be injected
using a SAGD technique.
[0009] In another aspect, there is provided a method of determining
production parameters
for a standing wave acoustic system for bitumen recovery, the method
comprising: obtaining a
sample of formation rock extracted from the bitumen reserve; and using an
experimental
technique to determine at least one resonant frequency of the formation rock
to enable standing
waves to be induced in a pay region comprising the formation rock and bitumen.
[0010] In yet another aspect, there is provided a method of determining a
resonant
frequency of formation rock in a bitumen reserve, the method comprising
performing in situ
testing of acoustic propagation in the formation rock, subsurface.
[0011] In yet another aspect, there is provided a system for recovering
bitumen from a
bitumen reserve, the system comprising: a plurality of acoustic resonators
positioned in a pay
region in the bitumen reserve, the plurality of acoustic resonators configured
to energize the
bitumen in the pay region by generating synchronized acoustic waves at a
resonant frequency
of a geological material in the pay region, the acoustic waves combining to
generate standing
waves within the pay region; and at least one acoustic generator coupled to
the plurality of
acoustic resonators.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Embodiments will now be described by way of example only with
reference to the
appended drawings wherein:
[0013] FIG. 1 is a cross-sectional elevation view of a system for
recovering bitumen from a
bitumen reserve using acoustic standing waves;
[0014] FIG. 2 is a cross-sectional elevation view of a system for
recovering bitumen from a
bitumen reserve using acoustic standing waves, in which multiple zones are
targeted;
[0015] FIG. 3 is a cross-sectional elevation view of an alternative
implementation of a
system for recovering bitumen from a bitumen reserve using acoustic standing
waves;
[0016] FIG. 4 is a flow chart illustrating operations performed in
determining resonant
frequencies in formation rock for a bitumen reserve to be used in bitumen
production; and
[0017] FIG. 5 is a flow chart illustrating operations performed in
producing bitumen using
acoustic standing waves.
DETAILED DESCRIPTION
[0018] The use of acoustic energy in oil recovery, particularly in
mobilizing bitumen, has
historically been limited by attenuation within the oil-bearing formation,
thus limiting the
penetration of energy. By determining resonant frequencies of the surrounding
formation rock,
and inducing acoustic standing waves within the formation, energy can be
propagated farther,
increasing the effectiveness at mobilizing bitumen within the formation. The
acoustic energy
that propagates within the formation can contribute to bitumen mobilization in
part due to some
degree of heating as well as due to vibration of the surrounding environment.
The acoustic
standing wave process described herein can be used as a primary bitumen
recovery process,
during start up, or subsequent to another oil recovery process such as SAGD or
CSS.
[0019] In the following, there is provided a method for recovering bitumen
from a bitumen
reserve. The method includes recovering a bitumen containing fluid from a pay
region in the
bitumen reserve via gravity drainage. The bitumen containing fluid is
recovered by energizing
the bitumen in the pay region using acoustic resonators positioned in the pay
region. Each pair
of the acoustic resonators generates synchronized acoustic waves that are
generated at a
resonant frequency of a geological material in the pay region. The acoustic
waves combine to
generate standing waves within the pay region.
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,
,
[0020] In an implementation of the system and method, the acoustic
resonators are
positioned in the pay region via vertically oriented wells.
[0021] In other implementations of the system and method, the plurality of
acoustic
resonators can be positioned in a pair of horizontally oriented wells. A lower
one of the pair of
horizontally oriented wells can be used to produce the bitumen containing
fluid to surface.
[0022] In other implementations, at least one additional resonant frequency
can be
determined and the plurality of acoustic resonators operated at the at least
one additional
resonant frequency.
[0023] In at least some implementations solvent can be injected before,
during, or after
operating the acoustic resonators.
[0024] In other implementations, steam can be injected into the pay region
prior to operating
the plurality of acoustic resonators. The steam that is injected can be
injected using a SAGD
technique.
[0025] There is also provided a method of determining production parameters
for a standing
wave acoustic system for bitumen recovery. The method includes obtaining a
sample of
formation rock extracted from the bitumen reserve. The sample of formation
rock is used to
determine at least one resonant frequency of the formation rock, using an
experimental
technique. Determining the resonant frequencies enables standing waves to be
induced in a
pay region that includes the formation rock and bitumen.
[0026] In some implementations, the at least one resonant frequency can be
tested in situ to
select at least one resonant frequency for production.
[0027] In some implementations, multiple resonant frequencies are
determined.
[0028] There is also provided a method of determining a resonant frequency
of formation
rock in a bitumen reserve. The method includes performing in situ testing of
acoustic
propagation in the formation rock, subsurface.
[0029] There is also provided a system for recovering bitumen from a
bitumen reserve. The
system includes a plurality of acoustic resonators positioned in a pay region
in the bitumen
reserve. The plurality of acoustic resonators are configured to energize the
bitumen in the pay
region by generating synchronized acoustic waves at a resonant frequency of a
geological
material in the pay region, and the acoustic waves combine to generate
standing waves within
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the pay region. The system also include at least one acoustic generator
coupled to the plurality
of acoustic resonators.
[0030] Turning now to the figures, FIG. 1 illustrates a bitumen reserve,
hereinafter referred
to as the "pay 10"; which is accessed for in situ bitumen recovery using a
plurality of resonator
wells 20 (a first resonator well 20a, and a second resonator well 20b shown by
way of example).
The resonator wells 20 at least in part extend into the pay 10. The pay 10
typically includes a
number of geological materials such as a rock matrix, sand, and fluid such as
the bitumen that
is being targeted. A formation at least partially underlies the pay 10, and is
hereinafter referred
to as the "underlying formation 14". In the example shown in FIG. 1, the pay
10 itself underlies
a layer of overburden 16 between the pay 10 and the surface 18.
[0031] The plurality of resonator wells 20 facilitate the placement and
positioning of acoustic
resonators 24 (a first acoustic resonator 24a, and a second acoustic resonator
24b shown by
way of example) within the pay 10 to emit acoustic energy into the pay 10.
Various acoustic
devices can be used for the acoustic resonators 24, for example, oscillators,
air guns, explosive
guns, mechanical vibrators, sonic or ultrasonic sirens or whistles, or other
sound- and vibration-
producing mechanical or electrical devices.
[0032] The plurality of acoustic resonators 24 are powered by acoustic
generators 28 (a first
acoustic generator 28a and a second acoustic generator 28b shown by way of
example) via
power and/or communication connections 26 (a first connection 26a and a second
connection
26b shown by way of example) between the acoustic generators 28 and the
acoustic resonators
24. The acoustic generators 28 in this example are controlled by a common
controller 36,
although it can be appreciated that more than one controller can be used,
e.g., dedicated
controllers 36 for each acoustic generator 28.
[0033] The first and second acoustic resonators 24a, 24b operate to create
a standing
acoustic wave 32 in the pay 10, i.e. an acoustic wave that remains in a
substantially constant
position. The standing wave 32 is generated through the superposition of a
first wave 30
generated by the first acoustic resonator 24a and a second wave 31 traveling
in an opposite
direction, which is generated by the second acoustic resonator 24b. The first
and second
waves 30, 31 are of substantially the same frequency in order to create the
standing wave 32,
and are chosen to be at or around a resonant frequency for the rock in the pay
10, i.e. to
achieve resonance within the pay 10. The standing waves 32 enable deeper
penetration
through the pay 10, in order to energize and mobilize the pay 10 to generate
mobilized bitumen
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34. Historically, the use of acoustic energy within oil bearing zones has been
found to be
ineffective, at least in part due to attenuation within the oil bearing zone,
thus limiting the
penetration of the acoustic energy. As such acoustic energy has often been
limited to
applications such as well clean outs, which only require minimal acoustic
penetration. By
determining resonant frequencies and inducing standing waves 32 within the pay
10, as herein
described, energy can be propagated farther with a greater impact on
mobilization of the
bitumen 34.
[0034] The mobilized bitumen 34 is produced using a horizontally oriented
producer well 22,
which is operated using production equipment 38 to produce the bitumen 34 to
surface 18. The
producer well 22 and production equipment 38 can be similar in structure and
function to
producer wells used in other advanced oil recovery methods such as SAGD or
CSS.
[0035] The number of, and spacing between, the resonator wells 20, can be
determined
according to the resonant frequency of the formation rock in the particular
pay 10 being
targeted. This is because different frequencies will have different factors of
penetration and
attenuation, thus dictating how far apart successive pairs of resonator wells
20 should be
placed.
[0036] The resonators 24 are also spaced at multiples of wavelengths apart.
For example,
the speed of sound in the particular formation is about 3000 m/s (versus about
343 m/s in air).
The wavelength is defined as A = fE, where A is the wavelength, f is the
resonant frequency, and
v is the speed of sound. By calculating A, the distance between the resonator
wells 20 can be
determined, e.g. at a spacing of xA, where x is a whole number greater than
zero. Higher
frequencies are attenuated faster, which lends to designing an acoustic system
by selecting the
lowest functional frequency, thus reducing the resonator well frequency.
[0037] As illustrated in FIG. 2, any number of resonator wells 20 required
to span the region
of pay 10 can be used, by configuring resonators 24 within the resonator wells
20 to induce
standing waves 32 in both directions, in unison with adjacent resonators 24 in
adjacent
resonator wells 20. In the example shown in FIG. 2, a first standing wave 32a
is generated
through the superposition of a first pair of first and second acoustic waves
30a, 31a; a second
standing wave 32b is generated through the superposition of a second pair of
first and second
acoustic waves 30b, 31b; a third standing wave 32c is generated through the
superposition of a
third pair of first and second acoustic waves 30c, 31c; a fourth standing wave
32d is generated
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through the superposition of a fourth pair of first and second acoustic waves
30d, 31d; and so
forth. Each resonator well 20a, 20b, 20c, and 20d is operated using a
dedicated acoustic
generator 28a, 28b, 28c, and 28d respectively, although fewer acoustic
generators 28 can be
used in order to power multiple acoustic resonators 24. As also shown in FIG.
2, a single
producer well 22 can be used to produce mobilized bitumen 34 for a number of
acoustic well-
pairs. However, it can be appreciated that multiple producer wells 22 can also
be used.
[0038] Turning now to FIG. 3, an alternative implementation is shown in
which an upper
horizontally oriented resonator well 20a is paired with a lower horizontally
oriented resonator
well 20b to induce vertical standing waves 32 within the pay 10. The lower
resonator well 20b
can also be used as a producer well 22 as illustrated in FIG. 3, although it
can be appreciated
that separate lower resonator and producer wells 20b, 22 can also be used.
[0039] In the implementation shown in FIG. 3, the upper and lower resonator
wells 20a,
20b contain a series of resonator pairs 50, 52. For example, a first upper
resonator 50a is
spaced along the upper resonator well 20a to be in horizontal alignment with a
first lower
resonator 52a in the lower well 20b, a second upper resonator 50b is spaced
along the upper
resonator well 20a to be in horizontal alignment with a second lower resonator
52b in the lower
well 20b, a third upper resonator 50c is spaced along the upper resonator well
20a to be in
horizontal alignment with a third lower resonator 52c in the lower well 20b, a
fourth upper
resonator 50d is spaced along the upper resonator well 20a to be in horizontal
alignment with a
fourth lower resonator 52d in the lower well 20b, and so forth.
[0040] By using a horizontal configuration as shown in FIG. 3, a smaller
footprint at surface
18 can be achieved. Moreover, the horizontal configuration requires fewer
wells to be drilled,
which is balanced against any additional losses resulting from the need to
space the resonators
50, 52 a great distance from the acoustic generator 28.
[0041] In order to induce the standing waves 32 within the pay 32, the
resonant
frequencies of the particular bitumen-containing formation are determined. For
example, as
shown in FIG. 4, a core can be drilled in the formation at 80 and one or more
experimental
techniques applied to the core at 82, to determine one or more resonant
frequencies of
geological components of the formation, e.g., the rock matrix, formation sand,
fluid, etc.
[0042] Various techniques are known in the art, which can be used at 82 to
conduct
resonance measurements of a geological material such as the formation
containing the pay 10.
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For example, it is known to measure the resonant frequency of a geological
material using a bar
resonance technique. In the bar resonance technique, the drill core can be set
into mechanical
(e.g., sonic and/or ultrasonic) vibration in one or more vibrational modes at
one or more
frequencies at which the vibrational displacements are at a maximum (i.e. at
resonance). The
drill core sample can be excited to vibration using drivers with continuously
variable frequencies
being output, or by impact, etc. Vibrations of the sample are monitored using
transducers and
analyzed to determine the resonant frequencies.
[0043] Another technique that could be used to conduct resonance
measurements
includes modifying acoustic generators to identify wavelengths which are least
attenuated. This
can be done in situ, i.e. subsurface prior to a production phase. That is, the
resonant frequency
of the formation can be determined by performing in situ testing of acoustic
propagation in the
formation rock, subsurface.
[0044] Yet another technique that could be used to conduct resonance
measurements
includes extracting a core measuring frequencies within the core, above
ground.
[0045] The aforementioned resonance measurements can be used to determine a
set of
one or more resonant frequencies, e.g., a set of harmonics, that are tested in
situ at 84 to
determine one or more suitable frequencies for production at 86. For example,
the testing
conducted at 84 could determine that more than one resonant frequency can be
effective at
mobilizing bitumen 23 in the pay 10, allowing the production phase to cycle
through more than
one frequency over time to maximize mobilization and/or to target different
materials within the
bitumen-containing formation. The process shown in FIG. 4 can be conducted
independently of
the production phase in which the standing waves 32 are generated and bitumen
34 is
produced as shown in FIGS. 1-3. Moreover, the process shown in FIG. 4 can be
conducted
periodically during production (e.g., on a yearly basis) in order to determine
if the resonant
frequency of the pay 10 has changed as a result of the changes caused by the
production itself.
It can also be appreciated that if the resonant frequency or frequencies of a
particular rock
matrix are already known, the process shown in FIG. 4 may not be required in
order to
determine the standing waves 32 for production.
[0046] FIG. 5 illustrates an example of a process for using acoustic
standing waves for
bitumen production. As shown in FIG. 5, the acoustic standing wave process
described herein
can be used in conjunction with solvent injection. Such solvent injection can
be optionally
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performed at any one or more of the following times: before the process at
100, during the
process at 108, or after the process at 114, as will be described in greater
detail below.
[0047] A resonant frequency for the rock-matrix, sand, fluid, etc. in the
pay 10 is
determined at 102, e.g., according to previously obtained experimental data
accordingly to the
process shown in FIG. 4. The acoustic generators 28 are operated at the
determined resonant
frequency at 104 to induce standing waves 32 in the pay 10, which enables
bitumen production
at 106. Optionally, solvent can also be injected into the pay 10, e.g., using
solvent injectors
installed in the resonator wells 20 at 108. The controller 36 determines at
110 if another
frequency is to be used (e.g., if more than one resonant frequency is
applicable and the
production phase cycles through these frequencies). If so, the process can
repeat at 102 with
another selected frequency. If no further frequencies are to be used at that
time, the controller
36 determines at 112 whether or not the production phase is done, or otherwise
requires the
acoustic generators 28 to cease operation. If production at that frequency is
to continue, the
process continues to repeat at 104. When production is done at 112, solvent
can be optionally
injected at 114.
[0048] As shown in FIG. 5, step 100, steam can also be injected prior to
the acoustic
standing wave process. For example, in one implementation, the acoustic
standing wave
process can be implemented subsequent to a SAGD process to enhance production
of a SAGD
site.
[0049] It will be appreciated that any module or component exemplified
herein that
executes instructions can include or otherwise have access to computer
readable media such
as storage media, computer storage media, or data storage devices (removable
and/or non-
removable) such as, for example, magnetic disks, optical disks, or tape.
Computer storage
media can include volatile and non-volatile, removable and non-removable media
implemented
in any method or technology for storage of information, such as computer
readable instructions,
data structures, program modules, or other data. Examples of computer storage
media include
RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital
versatile
disks (DVD) or other optical storage, magnetic cassettes, magnetic tape,
magnetic disk storage
or other magnetic storage devices, or any other medium which can be used to
store the desired
information and which can be accessed by an application, module, or both. Any
such computer
storage media can be part of the controller 36, acoustic generators 28,
acoustic resonators 24,
or any component of or related thereto, or accessible or connectable thereto.
Any application or
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module herein described can be implemented using computer readable/executable
instructions
that can be stored or otherwise held by such computer readable media.
[0050] For simplicity and clarity of illustration, where considered
appropriate, reference
numerals may be repeated among the figures to indicate corresponding or
analogous elements.
In addition, numerous specific details are set forth in order to provide a
thorough understanding
of the examples described herein. However, it will be understood by those of
ordinary skill in the
art that the examples described herein may be practiced without these specific
details. In other
instances, well-known methods, procedures and components have not been
described in detail
so as not to obscure the examples described herein. Also, the description is
not to be
considered as limiting the scope of the examples described herein.
[0051] The examples and corresponding diagrams used herein are for
illustrative purposes
only. Different configurations and terminology can be used without departing
from the principles
expressed herein. For instance, components and modules can be added, deleted,
modified, or
arranged with differing connections without departing from these principles.
[0052] The steps or operations in the flow charts and diagrams described
herein are just for
example. There may be many variations to these steps or operations without
departing from the
principles discussed above. For instance, the steps may be performed in a
differing order, or
steps may be added, deleted, or modified.
[0053] Although the above principles have been described with reference to
certain specific
examples, various modifications thereof will be apparent to those skilled in
the art as outlined in
the appended claims.
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