CA2883643C - System and method for recovering bitumen from a bitumen reserve using acoustic standing waves - Google Patents

Abstract

A system and method are provided for recovering bitumen from a bitumen reserve. The system and method operate to recover 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 a plurality of acoustic resonators positioned in the pay region, each pair of the plurality of acoustic resonators generating synchronized acoustic waves at a resonant frequency of a geological material in the pay region. The acoustic waves combine to generate standing waves within the pay region.

Description

, , , 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 22687522.1 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.

22687522.1 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.

22687522.1 , ,

[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 22687522.1 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 22687522.1

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 22687522.1 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.

22687522.1 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 22687522.1 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 22687522.1 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.

22687522.1

Claims (35)

Claims:

1. A method for recovering bitumen from a bitumen reserve, the method comprising:
energizing a geological material and bitumen within 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 directed at each other at a resonant frequency of the geological material in the pay region to combine and generate standing waves within the pay region between respective pairs of resonators;
and recovering a bitumen containing fluid from the bitumen reserve via gravity drainage.

2. The method of claim 1, wherein the plurality of acoustic resonators are positioned in the pay region via vertically oriented wellbores.

3. The method of claim 2, further comprising producing the bitumen containing fluid to surface using a horizontally oriented production well positioned below the plurality of resonators.

4. The method of claim 1, wherein the plurality of acoustic resonators are positioned in horizontally oriented wellbores.

5. The method of claim 4, wherein a lower one of the horizontally oriented wellbores is used to produce the bitumen containing fluid to surface.

6. The method of any one of claims 1 to 5, further comprising:
determining at least one additional resonant frequency; and operating the plurality of acoustic resonators at the at least one additional resonant frequency.

7. The method of any one of claims 1 to 6, wherein the plurality of acoustic resonators are powered by at least one acoustic generator from surface.

8. The method of any one of claims 1 to 6, wherein the plurality of acoustic resonators are each powered by an acoustic generator from surface.

9. The method of claim 7 or claim 8, wherein the plurality'of acoustic generators are coupled to a controller.

10. The method of any one of claims 1 to 9, further comprising injecting solvent into the pay region.

11. The method of claim 10, wherein the solvent is injected prior to operating the plurality of acoustic resonators.

12. The method of claim 10 or claim 11, wherein the solvent is injected subsequent to operating the plurality of acoustic resonators.

13. The method of any one of claims 10 to 12, wherein the solvent is injected during operation of the plurality of acoustic resonators.

14. The method of any one of claims 1 to 13, wherein steam is injected into the pay region prior to operating the plurality of acoustic resonators.

15. The method of claim 14, wherein the steam is injected using a steam assisted gravity drainage (SAGD) technique.

16. The method of any one of claims 1 to 15, further comprising determining at least one resonant frequency of the formation rock.

17. The method of claim 16, further comprising testing at least one experimentally determined resonant frequency in situ prior to recovering the bitumen containing fluid.

18. The method of claim 16 or claim 17, wherein a set of a plurality of resonant frequencies is determined.

19. The method of any one of claims 16 to 18, wherein the at least one resonant frequency of the formation rock is determined using a drill core extracted from the formation rock.

20. The method of any one of claims 16 to 19, further comprising determining if the resonant frequency has changed in the formation rock subsequent to at least some production of the bitumen containing fluid.

21. 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 a geological material and the bitumen within the pay region by generating synchronized acoustic waves directed at each other, at a resonant frequency of the geological material in the pay region to combine and generate standing waves within the pay region between pairs of the plurality of acoustic resonators; and at least one acoustic generator coupled to the plurality of acoustic resonators.

22. The system of claim 21, further comprising vertically oriented wellbores in the pay region into which the plurality of acoustic wellbores resonators are positioned.

23. The system of claim 22, further comprising a horizontally oriented production well positioned below the plurality of resonators for producing the bitumen containing fluid to surface.

24. The system of claim 21, further comprising horizontally oriented wellbores in the pay region in which the plurality of acoustic resonators are positioned.

25. The system of claim 24, wherein a lower one of the horizontally oriented wellbores is used to produce the bitumen containing fluid to surface.

26. The system of any one of claims 21 to 25, further comprising a controller configured to:
determine at least one additional resonant frequency; and operate the plurality of acoustic resonators at the at least one additional resonant frequency using the at least one acoustic generator.

27. The system of any one of claims 21 to 26, wherein the at least one acoustic generator is controlled from surface.

28. The system of any one of claims 21 to 27, wherein the plurality of acoustic resonators are each powered by an acoustic generator from surface.

29. The system of claim 27 or claim 28, further comprising a controller coupled to the plurality of acoustic generators.

30. The system of any one of claims 21 to 29, further comprising at least one solvent injector for injecting solvent into the pay region.

31. The system of claim 30, wherein the solvent is injected prior to operating the plurality of acoustic resonators.

32. The system of claim 30 or claim 31, wherein the solvent is injected subsequent to operating the plurality of acoustic resonators.

33. The system of any one of claims 30 to 32, wherein the solvent is injected during operation of the plurality of acoustic resonators.

34. The system of any one of claims 21 to 33, wherein steam is injected into the pay region prior to operating the plurality of acoustic resonators.

35. The system of claim 34, wherein the steam is injected using a steam assisted gravity drainage (SAGD) technique.