CA2917238C - System and method for recovering hydrocarbons from a hydrocarbon bearing formation using acoustic standing waves - Google Patents

Abstract

A system and method are provided for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation. The system and method operate to increase the permeability of the formation to enable such recovery. The permeability of the pay region is increased (e.g., by creating fractures and/or microfractures in the formation) using at least one acoustic resonator positioned in the pay region, each acoustic resonator 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 to increase the permeability.

Description

SYSTEM AND METHOD FOR RECOVERING HYDROCARBONS FROM A HYDROCARBON
BEARING FORMATION USING ACOUSTIC STANDING WAVES
TECHNICAL FIELD
[0001] The following relates to systems and methods for recovering hydrocarbons from a hydrocarbon bearing formation using acoustic standing waves.
DESCRIPTION OF THE RELATED ART

[0002] Many hydrocarbon bearing formations have low permeability, e.g., reservoirs with poorly connected inter-granular pores or vugs and/or low vulgar porosity. The low permeability can be found in tight oil and gas reservoirs (e.g., siltstones, shale, etc.
that trap a mobile oil), as well as carbonates, and heterolithic portions of clastic reservoirs that include muds saturated with water such as oil sands containing bitumen.

[0003] Because of the low permeability of shale, shale hydrocarbon reservoirs typically need to be fractured to allow the oil and gas to flow into a well drilled into the shale formation.
To fracture shale, a number of wells are drilled into the shale deposit, and several hydraulic fracturing treatments may be applied over time. Hydraulic fracturing involves pumping fracturing fluid into a well bore at a rate sufficient to increase pressure at the target depth to exceed that of the fracture gradient of the rock. The fracturing fluid causes the rock to crack, and the fluid permeates the rock to extend the crack further. Fractures created by hydraulic fracturing typically extend outwardly from the wellbore. The fractures enable the shale gas and shale oil to flow more freely within the shale, thus facilitating production. When the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants hold the fractures open.

[0004] Concerns have been raised with respect to the environmental impacts of hydraulic fracturing, which include risks to ground and surface water contamination from the fracturing fluid, and seismic activity following the application of hydraulic fracturing.
SUMMARY

[0005] In one aspect, there is provided a method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising: increasing permeability in a pay region in the formation using at least one acoustic resonator positioned in the pay region that generates acoustic waves at a predetermined resonant frequency of a geological material in the pay region, wherein acoustic waves combine to generate standing waves within the pay region that increase the permeability of the pay region.
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[0006] In another aspect, there is provided a system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising: at least one acoustic resonator positioned in a pay region in the formation that generates acoustic waves at a predetermined resonant frequency of a geological material in the pay region, wherein acoustic waves combine to generate standing waves within the pay region that increase the permeability of the pay region; and at least one acoustic generator coupled to the at least one acoustic resonator.

[0007] In yet another aspect, there is provided a method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising:
operating at least two acoustic resonators to achieve a predetermined resonant frequency of a geological material in the formation, wherein adjacent ones of the at least two acoustic resonators are positioned in corresponding wellbores in the formation to generate opposing acoustic waves at the resonant frequency, the opposing acoustic waves combining to generate standing waves within the formation which increase the permeability of the formation.

[0008] In an implementation of the methods and/or system, the formation can comprise any one or more of shale, sandstone, or carbonate rock. In a formation comprising shale, increasing permeability in the pay region comprises creating fractures and/or microfractures in the shale using the acoustic standing waves.

[0009] In an implementation, the methods can further comprise recovering a hydrocarbon from the pay region.

[0010] In an implementation of the system and/or methods, the acoustic resonators can be positioned in the pay region via substantially vertically oriented wells.

[0011] In other implementations of the system and/or methods, the acoustic resonators can be positioned in one or more substantially horizontally oriented wells.
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 fracturing a hydrocarbon bearing formation using acoustic standing waves;

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[0014] FIG. 2 is a cross-sectional elevation view of a system for fracturing a hydrocarbon bearing formation 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 fracturing a hydrocarbon bearing formation using acoustic standing waves;

[0016] FIG. 4 is a cross-sectional elevation view of yet another alternative implementation of a system for fracturing a hydrocarbon bearing formation using acoustic standing waves;

[0017] FIG. 5 is a flow chart illustrating operations performed in determining resonant frequencies in formation rock for a hydrocarbon reserve;

[0018] FIG. 6 is a flow chart illustrating operations performed in fracturing a hydrocarbon bearing formation using acoustic standing waves;

[0019] FIG. 7A is a cross-sectional elevation view of a system for increasing permeability in a formation using acoustic standing waves;

[0020] FIG. 7B is a cross-sectional elevation view of a system for producing heavy oil using acoustic standing waves subsequent to the stage illustrated in FIG. 7A;

[0021] FIG. 8A is a cross-sectional elevation view of a system for fracturing a hydrocarbon bearing formation using acoustic standing waves for facilitating heavy oil production;

[0022] FIG. 8B is a cross-sectional elevation view of a system for producing heavy oil using acoustic standing waves subsequent to the stage illustrated in FIG. 8A;

[0023] FIG. 9A is a cross-sectional elevation view of an alternative implementation of a system for fracturing a hydrocarbon bearing formation using acoustic standing waves;

[0024] FIG. 9B is a cross-sectional elevation view of an alternative implementation of a system for producing heavy oil using acoustic standing waves subsequent to the stage illustrated in FIG. 9A;

[0025] FIG. 9C is a cross-sectional elevation view of a system for producing heavy oil using steam assisted gravity drainage (SAGD) subsequent to the stage illustrated in FIG. 7A or FIG.9A; and

[0026] FIG. 10 is a flow chart illustrating operations performed in producing bitumen using acoustic standing waves.

22852956.1 DETAILED DESCRIPTION

[0027] By determining resonant frequencies of the surrounding formation rock, and inducing acoustic standing waves within the formation, the permeability of the formation can be increased, e.g., by fracturing a rock matrix, or linking pores in the rock matrix. For example, in shale formations, fractures and/or microfractures created by acoustic standing waves can facilitate production of shale oil and/or shale gas in the shale formation by enabling the shale oil and/or shale gas to flow into one or more wells drilled into the formation. In general, by increasing the permeability within a rock formation, standing wave fracturing can be used to increase pore connectivity in the formation to enhance the recovery of hydrocarbons using subsequent oil recovery techniques.

[0028] The acoustic standing wave process described herein can be used as a primary hydrocarbon production process, e.g., as a shale-fracturing hydrocarbon recovery process; or as a preliminary process to increase permeability for subsequent production in any formation, using another hydrocarbon recovery process.

[0029] In the following, there is provided a system and method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation. The method includes increasing the permeability in a pay region in the formation using at least one acoustic resonator positioned in the pay region. Each acoustic resonator generates acoustic waves at a resonant frequency of a geological material in the pay region, and the acoustic waves combine to generate standing waves within the pay region. The standing waves increase the permeability of the pay region, e.g., by creating fractures and/or microfractures in the formation, increasing permeability in the rock matrix.

[0030] In an implementation of the system and method, the acoustic resonators can be positioned in the pay region via substantially vertically oriented wells.

[0031] In other implementations of the system and method, the acoustic resonators can be positioned in one or more substantially horizontally oriented wells.

[0032] In other implementations, at least one additional resonant frequency can be determined and the acoustic resonators operated at the at least one additional resonant frequency.

[0033] In other implementations, the method and system are used in combination with an oil recovery technique. For example, the acoustic generators can be used to increase permeability 22852956.1 in the pay region, and then are subsequently operated to mobilize heavy oil such as bitumen, that is contained in the same pay region.

[0034] Turning now to the figures, FIG. 1 illustrates a hydrocarbon-bearing formation reserve, hereinafter referred to as the "pay 10"; which is accessed for hydrocarbon recovery. In this example, the pay 10 includes shale gas and/or shale oil (hereinafter "shale hydrocarbons 22") recovered using a plurality of resonator wells 20 (a first resonator well 20a, and a second resonator well 20b shown by way of example). The pay 10 can include any combination of shale, sandstone, or carbonate rock, etc., and the techniques described herein can be applied to any formation to improve the permeability. The resonator wells 20 at least in part extend into the pay 10. A formation at least partially underlies the pay 10, and is hereinafter referred to as the "underlying formation 12". In the example shown in FIG. 1, the pay 10 underlies a layer of overburden 16 between the pay 10 and the surface 18.

[0035] 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.

[0036] 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.

[0037] 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, 22852956.1 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.

[0038] The standing waves 32 penetrate through the pay 10, and the vibrations are sufficient to cause fractures and/or microfractures in the rock formation throughout an area of the pay 10. The fractures and microfractures are created when the acoustic energy within the standing waves cause the rock formation to deform and yield. By creating fractures and/or microfractures within the pay 10, hydrocarbons 22 can be recovered as illustrated in FIG. 1. For example, shale gas and/or shale oil can begin to flow into the resonator wells 20 allowing for the shale gas and/or shale oil to be recovered using techniques known in the art.
The standing waves 32 can be applied and power increased until hydrocarbons 22 begin to flow into the wells 20, at which time the fracturing process can be stopped or the power reduced to control fracture propagation. That is, the fracturing process can be controlled to achieve enough fracturing to produce hydrocarbons without creating undesirably large fractures.

[0039] 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 throughout the pay 10 to create fractures and/or microfractures throughout the rock formation, e.g., in a shale formation as illustrated in this example.

[0040] 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.

[0041] The resonators 24 are also spaced at multiples of wavelengths apart.
For example, the speed of sound in a particular formation is about 3000 m/s (versus about 343 m/s in air).
The wavelength is defined as A = 11 , 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 22852956.1 frequencies are attenuated faster, which lends to designing an acoustic system by selecting the lowest functional frequency, thus reducing the resonator well frequency.

[0042] 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 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.

[0043] 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. While the implementation shown in FIG. 3 shows vertically-spaced horizontally oriented wells 20, it can be appreciated that side-by-side horizontally oriented wells 20 can also be used, i.e., wells 20 which are horizontally oriented and horizontally spaced from each other. Combinations of vertically and horizontally spaced wells 20 can also be used to create arrays of resonator wells 20 throughout the pay 10.

[0044] 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.

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[0045] 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. After creating fractures and/or microfractures in the pay 10, the horizontal resonator wells 20a, 20b can be used to recover the hydrocarbons 22 that are now able to more easily flow within the pay 10.

[0046] As illustrated in FIG. 4, it can be appreciated that standing waves 30 can also be generated using a single resonator 50 or 52 when there is a surface against which the first acoustic wave 30 can reflect creating a second acoustic wave 31 that together create the standing wave 32. For example, in the implementation shown in FIG. 4, a single resonator well 22 is drilled along the bottom of the pay 10 and includes a series of lower resonators 52a, 52b, 52c, 52d. These lower resonators 52a-52d are operable to transmit a series of first waves 30a-30d that reflect off the bottom of a solid surface such as an impermeable layer 14 in the overburden 16, to generate a series of second waves 31a-31d that superimpose on the first waves 30a-30d to generate the standing waves 30a-30d. The shale hydrocarbons 22 can be recovered through the horizontally oriented resonator well 20. It can be appreciated that if the underlying formation 12 is suitable, the resonator well 20 can also be drilled along the top of the pay 10 to direct acoustic waves 30a-30d downwardly. Furthermore, single resonator wells 20 can also be used in vertical configurations as shown in FIGS. 1 and 2 when an appropriate surface is present for reflecting the acoustic waves 30.

[0047] In order to induce the standing waves 32 within the pay 32, the resonant frequencies of the particular formation are determined. For example, as shown in FIG. 5, 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., a rock matrix, formation sand, fluid, etc.

[0048] 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.
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 22852956.1 being output, or by impact, etc. Vibrations of the sample are monitored using transducers and analyzed to determine the resonant frequencies.

[0049] 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.

[0050] Yet another technique that could be used to conduct resonance measurements includes extracting a core measuring frequencies within the core, above ground.

[0051] 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 creating fractures and/or microfractures in the pay 10, allowing the fracturing phase to cycle through more than one frequency over time to maximize permeability and/or to target different materials within the bitumen-containing formation. The process shown in FIG. 5 can be conducted independently of the production phase in which the standing waves 32 are generated and hydrocarbons 22 are recovered as shown in FIGS. 1-4. Moreover, the process shown in FIG. 5 can be conducted periodically before and/or 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 (i.e. if any shale hydrocarbons 22 extracted from the shale formation cause the properties of the rock in the pay 10 to change). 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. 5 may not be required in order to determine the standing waves 32 for fracturing and production of shale hydrocarbons 22.

[0052] FIG. 6 illustrates an example of a process for using acoustic standing waves for creating fractures and/or microfractures in a formation to recover hydrocarbons therefrom. A
resonant frequency for the rock-matrix, sand, fluid, etc. in the pay 10 is determined at 100, e.g., according to previously obtained experimental data accordingly to the process shown in FIG. 5.
The acoustic generators 28 are operated at the determined resonant frequency at 102 to induce standing waves 32 in the pay 10, which creates fractures and/or microfractures in the formation at 104, allowing hydrocarbons such as shale oil and/or shale gas to be produced at 106.

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[0053] The controller 36 determines at 108 if another frequency is to be used (e.g., if more than one resonant frequency is applicable and the fracturing phase cycles through these frequencies). If so, the process can repeat at 100 with another selected frequency. If no further frequencies are to be used at that time, the controller 36 determines at 110 whether or not the fracturing 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 102. Otherwise, the fracturing process and any production performed during operation of the standing waves in the formation ends at 112.

[0054] In the examples shown in FIGS. 1-6, the fractures and microfractures created in the pay 10 were illustrated as providing an alternative to existing techniques for producing hydrocarbons in tight formations, such as those containing shale or other formations having low permeability, e.g., as an alternative to hydraulic fracturing which causes relatively larger fractures that extend outwardly from the wells. The fractures and/or microfractures created using the standing wave technique described herein, increase the permeability of the rock (e.g.
shale) in the pay 10 and thus enable hydrocarbons 22 to flow towards the resonator wells 20, e.g., similar to existing shale fracturing techniques.

[0055] The acoustic standing wave principles discussed herein can be applied to any hydrocarbon-bearing formation to increase the permeability of that formation and enhance the flow of hydrocarbons therewithin. For example, as shown in FIG. 7A, a configuration that is similar to what is shown in FIG. 3 can be applied to pay 10 in which pores 70 within the rock (see inset view) to have microfractures 72 link pores together to increase permeability within the pay 10. The interconnected porosity created by the microfractures 72 are created due to the stresses applied by the standing waves 30.

[0056] After increasing the permeability as illustrated in FIG. 7A, the acoustic standing waves 30 can continue to be used as shown in FIG. 7B to, for example, increase the flow of a hydrocarbon in the pay 10 (on its own or by applying another oil recovery technique).

[0057] It has also been recognized that at least some tight oil and gas formations and/or other formations having relatively low permeability can also include at least some heavy oil or otherwise viscous hydrocarbons such as bitumen. The acoustic energy that propagates within the formation by way of the standing wave technique described herein, can also be used to contribute to mobilization of bitumen or other types of heavy or viscous oil.
Mobilization of the bitumen is caused by reducing the viscosity of the bitumen using the acoustic energy in the 22852956.1 standing waves, based on two effects. First, the standing waves contribute to lowering the viscosity because the acoustic energy itself has been found to lower the viscosity of the bitumen. For example, it has been found experimentally that in the presence of shear or other energy sources, such as acoustic energy, the rheology of the non-Newtonian bitumen changes as a characteristic of the bitumen itself. Second, at least some of the acoustic energy propagating through the formation would be converted to heat, which further lowers the viscosity =
of the bitumen. That is, exposure to the acoustic energy can cause an increase in temperature that also decreases viscosity. As such, the standing wave acoustic technique can be used to increase the permeability in the formation, and to facilitate a subsequent application of SAGD or cyclic steam stimulation (CSS) or to mobilize and produce the bitumen or heavy oil itself.

[0058] The use of acoustic energy 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 heavy oil such as bitumen within the formation.
That is, in addition to fracturing rock formation in the pay 10, any heavy oil such as bitumen can be mobilized using a similar standing wave configuration. 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.

[0059] In the following, there is provided a method for recovering heavy oil such as bitumen from the pay 10, which can be done following the fracturing process described above, but can also be done independently. The method includes recovering a heavy oil or 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.

[0060] FIGS. 8A and 8B illustrate an implementation in which the acoustic standing wave configuration described above is used for both creating fractures and/or microfractures in the pay 10 and mobilizing heavy oil in the pay 10. In FIG. 8A, the same configuration is shown as that in FIG. 1, with the addition of a producer well 60 that is drilled along the bottom of the pay and production equipment 38 installed at surface 18. By having the producer well 60 in the 22852956.1 pay 10, the resonators 24a and 24b can be used to mobilize heavy oil 34 in the pay as illustrated in FIG. 8B. It can be appreciated that the producer well 60 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. A single producer well 60 can be used to produce mobilized bitumen 34 for a number of acoustic well-pairs (e.g., adapted for the arrangement shown in FIG.
2). However, it can be appreciated that multiple producer wells 60 can also be used.

[0061] FIGS. 9A and 9B illustrate another implementation using horizontally oriented resonator wells 20a, 20b; wherein the same configuration as shown in FIG. 3 is used, and the lower resonator well 20b is used as the production well 60. While the lower resonator well 20b is used as a producer well 60 in this example, it can be appreciated that separate lower resonator and producer wells 20b, 60 can also be used.

[0062] In yet another implementation shown in FIG. 90, after increasing permeability as illustrated in FIG. 7A or FIG. 9A, the acoustic equipment can be removed and another oil recovery technique employed as shown in FIG. 90, in which a SAGD well-pair 60, 62 is introduced. In this way, an advanced oil recovery technique is used to mobilize bitumen 34 in the pay 10 after having applied the standing wave acoustic technique described herein to create a higher permeability. As such, it can be appreciated that the acoustic standing wave system shown herein can be applied in various configurations, including as a stand-alone configuration, as well as in combination with other oil recovery techniques to recover hydrocarbons from the pay 10.

[0063] FIG. 10 is a flow chart illustrating an example of a process that uses acoustic standing waves 30 to both increase permeability in the pay 10 (e.g., by fracturing shale, increasing pores in the rock matrix, etc.), and energize and mobilize heavy oil in the pay 10 thereafter - bitumen in this example. Steps 100 through 110 are similar to those shown in FIG.
and thus need not be reiterated here. However, it may be noted that in step 104, the standing waves 30 have the effect of generally increasing the permeability of the pay 10, which can include fracturing shale in shale formations, or increasing the interconnected porosity of the rock matrix as discussed above. After determining that production is to begin at step 100, the process proceeds to step 200.

[0064] As shown in FIG. 10, the acoustic standing wave process described herein can be used in conjunction with solvent injection. Suitable solvents include, for example: alkanes, n (normal) and iso-alkanes, naphtha, toluene, xylene, benzene, diesel, natural gas, etc. Such 22852956.1 solvent injection can be optionally performed at any one or more of the following times: before the process at 200, during the process at 208, or after the process at 214, as will be described in greater detail below.

[0065] A resonant frequency for the rock-matrix, sand, fluid, etc. in the pay 10 is determined at 202 (if different from that used to increase permeability at 104), e.g., according to previously obtained experimental data according to the process shown in FIG.
5. The acoustic generators 28 are operated at the determined resonant frequency at 204 to induce standing waves 32 in the pay 10, which enables bitumen production at 206. Optionally, solvent can also be injected into the pay 10, e.g., using solvent injectors installed in the resonator wells 20 at 208. The controller 36 determines at 210 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 202 with another selected frequency. If no further frequencies are to be used at that time, the controller 36 determines at 212 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 204. When production is done at 212, solvent can be optionally injected at 214.

[0066] 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 module herein described can be implemented using computer readable/executable instructions that can be stored or otherwise held by such computer readable media.

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[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

22852956.1

Claims (88)

Claims:

1. A method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising:
increasing permeability in a pay region in the formation using at least one acoustic resonator positioned in the pay region by generating acoustic waves at a predetermined resonant frequency of a geological material in the pay region, wherein the acoustic waves combine to generate standing waves within the pay region that increase the permeability of the pay region.

2. The method of claim 1, wherein the formation comprises any one or more of shale, sandstone, or carbonate rock.

3. The method of claim 2, wherein the formation comprises shale, and wherein increasing permeability in the pay region comprises creating fractures, microfractures, or fractures and microfractures in the shale, using the acoustic standing waves.

4. The method of any one of claims 1 to 3, further comprising:
predetermining the resonant frequency of the geological material in the pay region.

5. The method of any one of claims 1 to 4, further comprising:
recovering a hydrocarbon from the pay region.

6. The method of claim 5, wherein the hydrocarbon is recovered from the pay region using at least one wellbore used to position the at least one acoustic resonator.

7. The method of any one of claims 1 to 6, wherein the at least one acoustic resonator is positioned in the pay region via a substantially vertically oriented wellbore.

8. The method of claim 7, wherein increasing permeability is performed by using a plurality of acoustic resonators, adjacently positioned ones of the plurality of acoustic resonators being positioned in a corresponding substantially vertically oriented wellbore.

9. The method of any one of claims 1 to 6, wherein the at least one acoustic resonator is positioned in the pay region via a substantially horizontally oriented wellbore.

10. The method of claim 9, wherein increasing permeability is performed by using a plurality of acoustic resonators, oppositely positioned ones of the plurality of acoustic resonators being positioned in a corresponding substantially horizontally oriented wellbore.

11. The method of any one of claims 4 to 10, further comprising:
operating the at least one acoustic resonator at an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

12. The method of any one of claims 1 to 11, wherein the at least one acoustic resonator is powered by at least one acoustic generator from surface.

13. The method of any one of claims 1 to 12, wherein a plurality of acoustic resonators are each powered by an acoustic generator from surface.

14. The method of claim 12 or claim 13, wherein the at least one acoustic generator is coupled to a controller.

15. The method of any one of claims 4 to 14, further comprising selecting the resonant frequency from a plurality of resonant frequencies of the geological material.

16. The method of any one of claims 1 to 14, further comprising testing at least one experimentally determined resonant frequency in situ prior to generating the standing waves.

17. The method of claim 16, wherein a set of a plurality of resonant frequencies is determined based on the in situ testing.

18. The method of any one of claims 15 to 17, wherein at least one resonant frequency of the geological material is determined using a drill core extracted from the formation rock.

19. The method of any one of claims 1 to 18, further comprising determining if the resonant frequency has changed in the geological material subsequent to at least some production of a hydrocarbon in the pay region.

20. The method of any one of claims 5 to 19, wherein recovering the hydrocarbon from the pay region comprises applying an oil recovery technique.

21. The method of claim 20, wherein the oil recovery technique comprises generating standing waves within the pay region to mobilize a heavy oil in the pay region.

22. The method of claim 21, wherein the heavy oil is bitumen.

23. The method of claim 20, further comprising producing a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the at least one resonator.

24. The method of claim 23, wherein a lower one of a pair of substantially horizontally oriented wellbores containing a plurality of acoustic resonators is used to produce the bitumen containing fluid to surface.

25. The method of any one of claims 20 to 24, further comprising injecting solvent into the pay region.

26. The method of claim 25, wherein the solvent is injected prior to operating the at least one acoustic resonator to mobilize the heavy oil.

27. The method of claim 25 or claim 26, wherein the solvent is injected subsequent to operating the at least one acoustic resonator to mobilize the heavy oil.

28. The method of any one of claims 25 to 27, wherein the solvent is injected during operation of the at least one acoustic resonator to mobile the heavy oil.

29. The method of claim 20, wherein the oil recovery technique comprises a steam assisted gravity drainage (SAGD) technique.

30. A system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising:
at least one acoustic resonator positioned in a pay region in the formation that generates acoustic waves at a predetermined resonant frequency of a geological material in the pay region, wherein the acoustic waves combine to generate standing waves within the pay region that increase the permeability of the pay region; and at least one acoustic generator coupled to the at least one acoustic resonator.

31. The system of claim 30, wherein the formation comprises any one or more of shale, sandstone, or carbonate rock.

32. The system of claim 31, wherein the formation comprises shale, and wherein increasing permeability in the pay region comprises creating fractures, microfractures, or fractures and microfractures in the shale, using the acoustic standing waves.

33. The system of claim 30, wherein a hydrocarbon is recovered from the pay region using at least one wellbore used to position the at least one acoustic resonator.

34. The system of any one of claims 30 to 33, wherein the at least one acoustic resonator is positioned in the pay region via a substantially vertically oriented wellbore.

35. The system of claim 34, wherein a plurality of acoustic resonators are positioned in the pay region, adjacently positioned ones of the plurality of acoustic resonators being positioned in a corresponding substantially vertically oriented wellbore.

36. The system of any one of claims 30 to 35, wherein the at least one acoustic resonator is positioned in the pay region via a substantially horizontally oriented wellbore.

37. The system of claim 36, wherein a plurality of acoustic resonators are positioned in the pay region, oppositely positioned ones of the plurality of acoustic resonators being positioned in a corresponding substantially horizontally oriented wellbore.

38. The system of any one of claims 30 to 37, wherein the system is configured to operate the at least one acoustic resonator using an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

39. The system of any one of claims 30 to 38, wherein the at least one acoustic resonator is powered by at least one acoustic generator from surface.

40. The system of any one of claims 30 to 39, wherein a plurality of acoustic resonators are each powered by an acoustic generator from surface.

41. The system of claim 39 or claim 40, wherein the at least one acoustic generator is coupled to a controller.

42. The system of any one of claims 30 to 41, further comprising an apparatus for determining at least one resonant frequency of the geological material.

43. The system of claim 42, further comprising apparatus for testing at least one experimentally determined resonant frequency in situ prior to generating the standing waves.

44. The system of claim 42 or claim 43, wherein the apparatus is configured to determine a set of a plurality of resonant frequencies based on the in situ testing.

45. The system of any one of claims 42 to 44, wherein the at least one resonant frequency of the geological material is determined using a drill core extracted from the formation rock.

46. The system of any one of claims 42 to 45, wherein the system is configured to determine if the resonant frequency has changed in the geological material subsequent to at least some production of a hydrocarbon in the pay region.

47. The system of any one of claims 33 to 46, wherein the system is configured for recovering the hydrocarbon from the pay region by applying an oil recovery technique.

48. The system of claim 47, wherein the oil recovery technique comprises generating standing waves within the pay region to mobilize a heavy oil in the pay region.

49. The system of claim 48, wherein the heavy oil is bitumen.

50. The system of claim 47, wherein the system is configured to produce a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the at least one resonator.

51. The system of claim 50, wherein a lower one of a pair of substantially horizontally oriented wellbores containing a plurality of acoustic resonators is used to produce the bitumen containing fluid to surface.

52. The system of any one of claims 47 to 51, further comprising apparatus for injecting solvent into the pay region.

53. The system of claim 52, wherein the system is configured for injecting the solvent prior to operating the at least one acoustic resonator to mobilize the heavy oil.

54. The system of claim 52 or claim 53, wherein the system is configured for injecting the solvent subsequent to operating the at least one acoustic resonator to mobilize the heavy oil.

55. The system of any one of claims 52 to 54, wherein the system is configured to inject solvent during operation of the at least one acoustic resonator to mobilize the heavy oil.

56. The system of claim 47, wherein the oil recovery technique comprises a steam assisted gravity drainage (SAGD) technique.

57. A method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising:
operating at least two acoustic resonators to achieve a predetermined resonant frequency of a geological material in the formation, wherein adjacent ones of the at least two acoustic resonators are positioned in corresponding wellbores in the formation to generate opposing acoustic waves at the resonant frequency, the opposing acoustic waves combining to generate standing waves within the formation which increase the permeability of the formation.

58. The method of claim 57, wherein the corresponding wellbores in the formation are substantially vertically oriented.

59. The method of claim 57, wherein the corresponding wellbores in the formation are substantially horizontally oriented.

60. The method of any one of claims 57 to 59, further comprising:
operating the at least two acoustic resonators at an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

61. The method of any one of claims 57 to 60, wherein the at least two acoustic resonators are powered by at least one acoustic generator from surface.

62. The method of claim 61, wherein the at least two acoustic resonators are coupled to a controller to coordinate operation of the at least two acoustic resonators in generating the opposing acoustic waves.

63. The method of any one of claims 57 to 62, further comprising selecting the resonant frequency from a plurality of resonant frequencies of the geological material.

64. The method of any one of claims 57 to 63, wherein the formation comprises any one or more of shale, sandstone, or carbonate rock.

65. The method of claim 64, wherein the formation comprises shale, and wherein increasing permeability in the pay region comprises creating fractures, microfractures, or fractures and microfractures in the shale, using the acoustic standing waves.

66. The method of any one of claims 57 to 65, further comprising:
recovering a hydrocarbon from the hydrocarbon-bearing formation.

67. The method of claim 66, wherein the hydrocarbon is recovered from the hydrocarbon-bearing formation using at least one wellbore used to position the at least two acoustic resonators.

68. The method of any one of claims 66 to 67, wherein recovering the hydrocarbon from the hydrocarbon-bearing formation comprises applying an oil recovery technique.

69. The method of claim 68, wherein the oil recovery technique comprises generating standing waves within the hydrocarbon-bearing formation to mobilize a heavy oil in the hydrocarbon-bearing formation.

70. The method of claim 69, wherein the heavy oil is bitumen.

71. The method of claim 70, further comprising producing a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the at least two resonators.

72. The method of claim 71, wherein a lower one of a pair of substantially horizontally oriented wellbores containing at least two acoustic resonators is used to produce the bitumen containing fluid to surface.

73. A system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising at least two acoustic resonators positioned in a pay region in the formation, and at least one acoustic generator coupled to the at least two acoustic resonators, the system being configured to:
operate the at least two acoustic resonators to achieve a predetermined resonant frequency of a geological material in the formation, wherein adjacent ones of the at least two acoustic resonators are positioned in corresponding wellbores in the formation to generate opposing acoustic waves at the resonant frequency, the opposing acoustic waves combining to generate standing waves within the formation which increase the permeability of the formation.

74. The system of claim 73, wherein the corresponding wellbores in the formation are substantially vertically oriented.

75. The system of claim 73, wherein the corresponding wellbores in the formation are substantially horizontally oriented.

76. The system of any one of claims 73 to 75, further configured to:

operate the at least two acoustic resonators at an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

77. The system of any one of claims 73 to 76, wherein the at least two acoustic resonators are powered by at least one acoustic generator from surface.

78. The system of claim 77, wherein the at least two acoustic resonators are coupled to a controller to coordinate operation of the at least two acoustic resonators in generating the opposing acoustic waves.

79. The system of any one of claims 73 to 78, further configured to select the resonant frequency from a plurality of resonant frequencies of the geological material.

80. The system of any one of claims 73 to 79, wherein the formation comprises any one or more of shale, sandstone, or carbonate rock.

81. The system of claim 80, wherein the formation comprises shale, and wherein increasing permeability in the pay region comprises creating fractures, microfractures, or fractures and microfractures in the shale, using the acoustic standing waves.

82. The system of any one of claims 73 to 81, further configured to:
recover a hydrocarbon from the hydrocarbon-bearing formation.

83. The system of claim 82, wherein the hydrocarbon is recovered from the hydrocarbon-bearing formation using at least one wellbore used to position the at least two acoustic resonators.

84. The system of any one of claims 82 to 83, wherein recovering the hydrocarbon from the hydrocarbon-bearing formation comprises applying an oil recovery technique.

85. The system of claim 84, wherein the oil recovery technique comprises generating standing waves within the hydrocarbon-bearing formation to mobilize a heavy oil in the hydrocarbon-bearing formation.

86. The system of claim 85, wherein the heavy oil is bitumen.

87. The system of claim 86, further configured to produce a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the at least two resonators.

88. The system of claim 87, wherein a lower one of a pair of substantially horizontally oriented wellbores containing at least two acoustic resonators is used to produce the bitumen containing fluid to surface.