System and Method for Energizing Bitumen in a Bitumen Reserve for Recovery of Same, Using Acoustic Standing Waves

Abstract

A method is provided that uses acoustic energy propagating within the formation to contribute to hydrocarbon mobilization and/or increasing the permeability of the formation for producing such hydrocarbons, in part due to some degree of heating as well as due to vibration of the surrounding environment. An acoustic standing wave process can be used as a primary recovery process, during start up, or subsequent to another hydrocarbon recovery process. By selectively operating acoustic resonators in areas or zones within a pay region until that area or zone is energized, production can progress in stages in an efficient manner to avoid operating the acoustic resonators longer than is necessary to sufficiently energize the targeted area. In this way, the amount of equipment required to mobilize and produce the hydrocarbon in the pay region can be reduced.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Canadian Patent Application No. 3,009,932 filed on Jun. 27, 2018, incorporated herein by reference.

TECHNICAL FIELD

The following relates to systems and methods for energizing bitumen in a bitumen reserve for recovery of same, using acoustic standing waves.

DESCRIPTION OF THE RELATED ART

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.

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. For some bitumen reserves, steam driven techniques can be considered less desirable or less economical.

Moreover, 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.

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.

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

In one aspect, there is provided a method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising: energizing an area comprising a portion of the formation using a first set of at least one acoustic resonator positioned in the formation that generates acoustic waves at a predetermined resonant frequency of a geological material in the portion, wherein the acoustic waves generate standing waves within the portion that increase permeability of, and/or energize hydrocarbons in, the portion; ceasing operation of the first set of the at least one acoustic resonator; and commencing energizing at least one additional portion of the formation by beginning to operate a second set of at least one acoustic resonator positioned in the at least one additional portion.

In another aspect, there is provided a system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising: a first set of at least one acoustic resonator positioned in an area comprising a portion of the formation, the first set of at least one acoustic resonator configured to energize the area by generating acoustic waves at a predetermined resonant frequency of a geological material in the portion, wherein the acoustic waves generate standing waves within the portion that increase permeability of, and/or energize hydrocarbons in, the portion; a second set of at least one acoustic resonator positioned in at least one additional portion of the formation, wherein the second set of at least one acoustic resonator is configured to commence energizing the at least one additional portion after ceasing operation of the first set of the at least one acoustic resonator; and at least one acoustic generator coupled to the first and second sets of acoustic resonators.

In yet another aspect, there is provided a method for enhanced hydrocarbon recovery from a hydrocarbon-bearing formation, the method comprising: energizing a first portion of the formation using an acoustic resonator positioned within the formation to generate acoustic waves at a predetermined resonant frequency of a geological material in the first portion of the formation, wherein the acoustic waves generate standing waves that increase permeability and/or energize hydrocarbons in the first portion of the formation; upon reaching a desired permeability and/or energization of the hydrocarbons, ceasing the energizing of the first portion of the formation and commencing a hydrocarbon production operation in the first portion; commencing energizing a second portion of the formation using an acoustic resonator and continuing such energizing until reaching a desired permeability and/or energization of hydrocarbons in the second portion, upon which energizing the second portion is ceased and a production operation is commenced; and repeating the energizing followed by production operation selectively at multiple portions of the formation.

In yet another aspect, there is provided a system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising a plurality of acoustic resonator positioned within the formation in a plurality of portions of the formation; and at least one acoustic generator coupled to the plurality of acoustic resonators; wherein the plurality of acoustic resonators are configured to perform the above method.

In an implementation, the methods and systems can include recovering a hydrocarbon containing fluid from the formation after energizing the area, which can be done after energizing the at least one additional portion. The hydrocarbon containing fluid can be recovered via gravity drainage.

In an implementation, the operation of the first set of at least one acoustic resonator positioned in the portion can be ceased after the area of the pay region is energized, the first set of at least one acoustic resonator can be removed from the formation, and the first set of at least one acoustic resonator can be used in one or more of the at least one additional portion. At least three portions of the pay region can be selectively energized over corresponding periods of time, and at least one portion can be selectively energized more than once.

In an implementation, at least one portion of the pay region can be energized such that both permeability of the formation is increased, and the hydrocarbon is mobilized for subsequent production. The formation can comprise any one or more of shale, sandstone, or carbonate rock, and increasing permeability in the pay region can include creating fractures and/or microfractures in the shale using the acoustic standing waves.

In an implementation, the hydrocarbon can be recovered from the pay region using at least one wellbore used to position the first and/or second set of at least one acoustic resonator. In another implementation, the first and/or second set of at least one acoustic resonator can be positioned in the pay region via a substantially vertically oriented wellbore, and the energizing can be 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.

In an implementation, the first and/or second set of at least one acoustic resonator can be positioned in the pay region via a substantially horizontally oriented wellbore, and the energizing can be 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.

In an implementation, the methods can include predetermining the resonant frequency of the geological material in the pay region, and can also include operating the first and/or second set of at least one acoustic resonator at an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

In an implementation, the first and/or second set of at least one acoustic resonator is powered by at least one acoustic generator from surface. In another implementation, a plurality of acoustic resonators are each powered by an acoustic generator from surface, and the first and/or second set of at least one acoustic generator can be coupled to a controller. The method can further include selecting the resonant frequency from a plurality of resonant frequencies of the geological material.

In an implementation, the method can further include testing at least one experimentally determined resonant frequency in situ prior to generating the standing waves, and a set of a plurality of resonant frequencies can be determined based on the in situ testing. At least one resonant frequency of the geological material can also be determined using a drill core extracted from the formation rock. The methods can also include determining if the resonant frequency has changed in the geological material subsequent to at least some production of a hydrocarbon in the pay region.

In an implementation, recovering the hydrocarbon from the pay region can include applying an oil recovery technique, the oil recovery technique can include generating standing waves within the pay region to mobilize a heavy oil in the pay region, and the heavy oil can be bitumen. The methods can also include producing a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the first and/or second set of at least one resonator, and a lower one of a pair of substantially horizontally oriented wellbores containing a plurality of acoustic resonators can be used to produce the bitumen containing fluid to surface.

In an implementation, the methods can include injecting solvent into the pay region, the solvent can be injected prior to operating the first and/or second set of at least one acoustic resonator to mobilize the heavy oil, the solvent can be injected subsequent to operating the at least one acoustic resonator to mobilize the heavy oil, and the solvent can be injected during operation of the first and/or second set of at least one acoustic resonator to mobile the heavy oil.

In an implementation, the oil recovery technique includes a SAGD technique.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of example only with reference to the appended drawings wherein:

FIG. 1A is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves;

FIG. 1B is a cross-sectional elevation view of a system for energizing bitumen from a bitumen reserve using acoustic standing waves, in which the hydrocarbon bearing formation is at least in part fractured using the acoustic standing waves;

FIG. 2 is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves, in which a first area is energized and a second area is being targeted by the acoustic standing waves;

FIG. 3 is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves, in which first and second areas are energized and a third area is being targeted by the acoustic standing waves;

FIG. 4A is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves, in an alternative configuration;

FIG. 4B is a cross-sectional elevation view of a system for energizing bitumen from a bitumen reserve using acoustic standing waves in the alternative configuration, in which the hydrocarbon bearing formation is at least in part fractured using the acoustic standing waves;

FIG. 5 is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves in the alternative configuration, in which a first area is energized and a second area is being targeted by the acoustic standing waves;

FIG. 6 is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves in the alternative configuration, in which first and second areas are energized and a third area is being targeted by the acoustic standing waves;

FIG. 7 is a cross-sectional elevation view of a system for energizing bitumen in a bitumen reserve using acoustic standing waves, in another alternative configuration;

FIG. 8 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/or formation fracturing;

FIG. 9 is a flow chart illustrating operations performed in selectively generating acoustic standing waves to target areas in a bitumen reserve; and

FIG. 10 is a flow chart illustrating operations performed in increasing permeability of formation rock in a bitumen reserve and producing bitumen from the reserve, using acoustic standing waves.

DETAILED DESCRIPTION

The use of acoustic energy in oil or other hydrocarbon 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.

Moreover, by determining such 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.

The acoustic standing wave process described herein can therefore also 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.

By selectively operating acoustic resonators in areas or zones within a pay region until that area or zone is energized, bitumen or other hydrocarbon production can progress in stages in an efficient manner to avoid operating the acoustic resonators longer than is necessary to sufficiently energize the targeted area. In this way, the amount of equipment required to mobilize and produce the hydrocarbon in the pay region can be reduced.

Turning now to the figures, FIG. 1A, illustrates a bitumen reserve such as that found in the Canadian oil sands, hereinafter referred to as the “pay 10”; which is accessed for in situ bitumen recovery. While the examples provided herein refer to bitumen recovery, the principles discussed herein apply to other hydrocarbon recovery processes and to increasing the permeability of other types of reserves. 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. 1A, the pay 10 itself underlies a layer of overburden 16 between the pay 10 and the surface 18. In the implementation shown in FIG. 1A, an upper horizontally oriented resonator well 20 is paired with a lower horizontally oriented resonator well 30 to induce vertical standing waves 26 within the pay 10 therebetween. The lower resonator well 30 can also be used as an injector well, e.g., for injecting steam or solvent into the pay 10. A producer well 32 is also shown in this example, which can be used to produce a bitumen-containing fluid to surface 18. It can be appreciated that the lower resonator well 30 can also be used as a producer well in other implementations, and thus can eliminate the need for a separate producer well 32. Acoustic generation, injection, and production equipment (collectively “surface equipment 34”) is located at surface 18 and is used to operate acoustic resonators in the wells 20, 30, and injection and production equipment in the wells 30, 32, where applicable.

In the implementation shown in FIG. 1A, the upper and lower resonator wells 20, 30 contain a series of resonator pairs 22, 24. For example, a first upper resonator 22a is spaced along the upper resonator well 20 to be in horizontal alignment with a first lower resonator 24a in the lower well 30, a second upper resonator 22b is spaced along the upper resonator well 20 to be in horizontal alignment with a second lower resonator 24b in the lower well 30, and so forth. Various acoustic devices can be used for the acoustic resonators 22, 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.

By using a horizontal configuration as shown in FIG. 1A, a smaller footprint at surface 18 can be achieved. Moreover, the horizontal configuration requires fewer wells to be drilled than compared to a vertical well implementation (described below), which is balanced against any additional losses resulting from the need to space the resonators 22, 24 a greater distance from the acoustic generator(s).

The upper and lower acoustic resonators 22, 24 operate to create standing acoustic waves 26 in the pay 10, i.e. an acoustic wave that remains in a substantially constant position. The standing wave 26 is generated through the superposition of a first wave 27 generated by the upper acoustic resonator 22 and a second wave 28 traveling in an opposite direction, which is generated by the lower acoustic resonator 24. The first and second waves 27, 28 are of substantially the same frequency in order to create the standing wave 26, 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 26 enable deeper penetration through the pay 10, in order to energize and mobilize the pay 10 to generate mobilized bitumen. 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 26 within the pay 10, as herein described, energy can be propagated farther with a greater impact on mobilization of the bitumen.

In the example shown in FIG. 1A, a first acoustic resonator pair 22a, 24a and a second acoustic resonator pair 22b, 24b are being operated in order to target a particular zone or area 36 within the pay 10. As discussed in greater detail below, once the area 36 is energized, operation of the acoustic resonators 22a/24a, 22b/24b can be stopped, and different acoustic resonators used to target a different area 36 in the pay 10. The resonator pairs 22a/24a, 22b/24b can be moved along the wells 20, 30 or additional resonator pairs 22/24 can be brought online to energize a next one or more targeted areas 36.

As illustrated in FIG. 1B, and discussed above, a similar system and implementation thereof can be used to increase the permeability in the formation using at least one acoustic resonator positioned in the pay 10 and used to generate standing waves within the pay region. The standing waves can therefore also be used to increase the permeability of the pay region, e.g., by creating fractures and/or microfractures in the formation, increasing permeability in the rock matrix.

The standing waves 26 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 can be recovered. For example, shale gas and/or shale oil can begin to flow into the resonator well 30 and/or the producer well 32, allowing for the shale gas and/or shale oil to be recovered using techniques known in the art. The standing waves 26 can be applied and power increased until hydrocarbons begin to flow into the wells 30, 32, 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.

In the example shown in FIG. 1B, the fractures and microfractures created in the pay 10 are 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 to flow towards the resonator well 30 or producer well 32, e.g., similar to existing shale fracturing techniques.

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, a configuration that is similar to what is shown in FIGS. 1A and 1B can be applied to pay 10 in which pores 40 within the rock (see inset view in FIG. 1B) to have microfractures 42 link pores together to increase permeability within the pay 10. The interconnected porosity created by the microfractures 42 are created due to the stresses applied by the standing waves 26.

After increasing the permeability as illustrated in FIG. 1B, the acoustic standing waves 26 can continue to be used to increase the flow of a hydrocarbon in the pay 10 (on its own or by applying another oil recovery technique).

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 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.

FIG. 2 illustrates a subsequent stage in operation of the system shown in FIGS. 1A and/or 1B. In this subsequent stage, the first area 36 being targeted is determined to be “energized”, and the resonator pairs 22a/24a, 22b/24b cease operating, with new resonator pairs 22c/24c, 22d/24d commencing operation. It can be appreciated that the new resonator pairs 22c/24c, 22d/24d can be separate equipment or the same equipment as that used in providing the first resonator pairs 22a/24b, 22b/24b. It can also be appreciated that while two resonator pairs 22, 24 are shown in each stage of operation, this is only for illustrative purposes. That is, one or more than two resonator pairs 22, 24 can be utilized in any one of the targeted areas 36. The area 36 is considered to be an energized area of the formation or “energized area 50”, in that the acoustic energy introduced into the formation provides measurable vibrations in the rock. As illustrated in FIG. 2, the energized area 50 can be subjected to a production phase. For example, the bitumen in the energized area 50 may be mobilized such that mobilized bitumen 52 can be collected by gravity drainage using the producer well 34 (and/or lower resonator well 32). Additionally, steam and/or solvent can be injected into the energized area 50 to further mobilize the bitumen 52 during the production phase.

Turning now to FIG. 3, it can be appreciated that after increasing the size of the energized area 50 using the second resonator pairs 22c/24c, 22d/24d, a third area can be targeted using new third resonator pairs 22e/24e, 22f/24f. It can be appreciated that this process of selectively targeting areas of the pay 10 and moving acoustic generation operations to different areas can continue throughout a site. It can also be appreciated that previously targeted areas 36 of the pay 10 can be targeted again, e.g., to re-energize that particular previously-targeted area. That is, while the example shown in FIGS. 1-3 includes progressively moving acoustic generation operations along the well pairs 20, 30, this pattern of progression is only illustrative.

FIG. 4A illustrates an implementation using a plurality of vertically oriented resonator wells 20 (a first resonator well 20a, a second resonator well 20b, a third resonator well 20c, and a fourth resonator well 20d, shown by way of example). The resonator wells 20 at least in part extend into the pay 10.

The plurality of resonator wells 20 facilitate the placement and positioning of pairs of acoustic resonators 22, 24 (a first acoustic resonator pair 22a, 24a shown by way of example) within the pay 10 to emit acoustic energy into the pay 10.

The pairs of acoustic resonators 22, 24 are powered by acoustic generators 60 (a first acoustic generator 60a, a second acoustic generator 60b, a third acoustic generator 60c, and a fourth acoustic generator 60d shown by way of example) via power and/or communication connections between the acoustic generators 60 and the acoustic resonators 22, 24. The acoustic generators 60 in this example are controlled by a common controller 62, although it can be appreciated that more than one controller can be used, e.g., dedicated controllers 62 for each acoustic generator 60.

The first pair of acoustic resonators 22a, 24a operates to create a standing acoustic wave 26 in the pay 10, i.e. an acoustic wave that remains in a substantially constant position. The standing wave 26 is generated through the superposition of a first wave 27 generated by one of the acoustic resonators 22a, and a second wave 28 traveling in an opposite direction, which is generated by the second of the acoustic resonators 24a in the first acoustic resonator pair 22a, 24a. The first and second waves 27, 28 are of substantially the same frequency in order to create the standing wave 26, 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 mobilized bitumen can be produced using a horizontally-oriented producer well 32 (shown optionally using dashed lines), which is operated using production equipment (not shown in FIG. 4A) to produce the bitumen to surface 18. The producer well 32 and production equipment can be similar in structure and function to producer wells used in other advanced oil recovery methods such as SAGD or CSS.

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.

The resonator pairs 22, 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 λ=v/f, where λ is the wavelength, f is the resonant frequency, and v is the speed of sound. By calculating λ, the distance between the resonator wells 20 can be determined, e.g. at a spacing of xλ, 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.

As illustrated in FIG. 4A, any number of resonator wells 20 required to span the region of pay 10 can be used, by configuring resonators 22, 24 within the resonator wells 20 to induce standing waves 26 in both directions, in unison with adjacent resonators 22, 24 in adjacent resonator wells 20. In the example shown in FIG. 4A, only a first standing wave 26 is shown to illustrate targeting acoustic energy within a particular area 36 of the pay 10, as discussed above. It can be appreciated that standing waves 26 can be generated between any one or more (including all) pairs of resonator wells 20. As discussed herein, this can be done selectively to energize certain areas 36.

Similar FIG. 2B, FIG. 4B illustrates that 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, a configuration that is similar to what is shown in FIGS. 4A and 4B can be applied to pay 10 in which pores 40 within the rock (see inset view in FIG. 4B) to have microfractures 42 link pores together to increase permeability within the pay 10. The interconnected porosity created by the microfractures 42 are created due to the stresses applied by the standing waves 26.

FIG. 5 illustrates a subsequent stage in operation of the system shown in FIGS. 4A and/or 4B. In this subsequent stage, the first area 36 being targeted is determined to be “energized”, and the first resonator pair 22a, 24a ceases operating, with a new resonator pair 22b, 24b commencing operation. It can be appreciated that the new resonator pair 22b, 24b can include separate equipment or the same equipment as that used in providing the first resonator pair 22a, 24b. It can also be appreciated that while a single resonator pair 22, 24 is shown in each stage of operation, this is only for illustrative purposes. That is, one or more than two resonator pairs 22, 24 can be utilized in any one of the targeted areas 36. Similar to that described above, the area 36 is considered to be an energized area of the formation or an “energized area 50”, in that the acoustic energy introduced into the formation provides measurable vibrations in the rock. As illustrated in FIG. 5, the energized area 50 can be subjected to a production phase. For example, the bitumen in the energized area 50 may be mobilized such that mobilized bitumen 52 can be collected by gravity drainage using the producer well 32. Additionally, steam and/or solvent can be injected into the energized area 50 to further mobilize the bitumen 52 during the production phase.

Turning now to FIG. 6, it can be appreciated that after increasing the size of the energized area 50 using the second resonator pair 22b, 24b, a third area 36 can be targeted using new third resonator pair 22c, 24c. It can be appreciated that this process of selectively targeting areas of the pay 10 and moving acoustic generation operations to different areas can continue throughout a site. It can also be appreciated that previously targeted areas 36 of the pay 10 can be targeted again, e.g., to re-energize that particular previously-targeted area. That is, while the example shown in FIGS. 4-6 includes progressively moving acoustic generation operations along a series of pairs of vertical wells 20, this pattern of progression is only illustrative.

As illustrated in FIG. 7, it can be appreciated that standing waves 26 can also be generated using a single resonator 22 when there is a surface against which the first acoustic wave 27 can reflect creating a second acoustic wave 28 that together create the standing wave 26. For example, in the implementation shown in FIG. 7, a single resonator well 32 is drilled along the bottom of the pay 10 and includes a series of lower resonators 22a, 22b, etc. These lower resonators 22 are operable to transmit a series of first waves 27 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 28 that superimpose on the first waves 27 to generate the standing waves 26. It can be appreciated that if the underlying formation 12 is suitable, the resonator well 32 can also be drilled along the top of the pay 10 to direct acoustic waves 27 downwardly. Furthermore, single resonator wells 32 can also be used in vertical configurations as shown in FIGS. 4-6 when an appropriate surface is present for reflecting the acoustic waves 30. As illustrated in FIG. 7, this alternative, single well configuration can also be adapted to selectively target areas 36 of the pay 10 to energize those regions in a particular sequence or order, as described above.

It can also be appreciated that a single resonator configuration can also be implemented which does not rely on reflection and superimposition of the waves 27, 28, but instead generates the standing wave 26 outwardly from a single source. When implementing such a single resonator configuration, since the superposition effect provided by pairs of resonators as described above is not experienced, the amount of energy required to energize the formation in a similar manner increases. As such, a consideration of capital costs associated with installing as second resonator can be made against the increased energy costs in running the single resonator to achieve the same effect, in order to determine whether to utilized a single or dual resonator implementation.

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. 8, 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.

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

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.

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

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 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. 8 can be conducted independently of the production phases in which the standing waves 26 are generated and mobilized bitumen 52 is produced as shown in FIGS. 1-7. Moreover, the process shown in FIG. 8 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. 8 may not be required in order to determine the standing waves 26 for production.

FIG. 9 illustrates a process that can be implemented in order to selectively target areas 36 of the pay 10 as herein exemplified. At step 90 the acoustic generators 60 can be operated to generate standing waves 26. The flow of bitumen containing fluid is monitored at step 92 to determine if the pay area 36 has been sufficiently energized. If not, step 90 can continue. If the area 36 is determined to have become an energized area 50, operation of the at least one acoustic resonator 22, or resonator pair 22, 24 is ceased at step 94. When a further area 36 is to commence being energized, step 96 can be optionally implemented in which one or more acoustic resonators 22 or resonator pairs 22, 24 begin operation in at least one other pay area 36. As illustrated in FIG. 9, the process shown in FIG. 9 can be executed from step 92, from point A as a subroutine in a production, start-up, or other hydrocarbon extraction process, as shown in FIG. 10. That is, it can be appreciated that the process for energizing the pay area 36 shown in FIG. 9 can be considered both a stand-alone process for energizing hydrocarbons such as bitumen, and a sub-routine of a larger production process.

FIG. 10 is a flow chart illustrating an example of a process that uses acoustic standing waves 26 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. 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. 8. The acoustic generators 60 are operated at the determined resonant frequency at 102 to induce standing waves 26 in the pay 10, which creates fractures and/or microfractures in the formation at 104, e.g., allowing hydrocarbons such as shale oil and/or shale gas to be produced.

The controller 62 determines at 106 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 102 with another selected frequency. If no further frequencies are to be used at that time, the controller 62 determines at 108 whether or not the fracturing phase is done and thus whether or not production is to begin. It can be observed that the process shown in FIG. 9 can be implemented at point A, as a sub-routine to selectively target areas 36 of the pay 10 in order to selectively fracture areas 36 of the formation, e.g., as shown in FIGS. 1B and 4B.

It may be noted that in step 102, the standing waves 26 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 108, the process proceeds to step 200.

As shown in FIG. 10, the acoustic standing wave process described herein can be used in conjunction with solvent injection and/or steam injection with various combinations of acoustic standing waves and/or solvent and/or steam according to the orientation and configuration of the equipment being used, which can vary based on the type of rock in the formation. Suitable solvents include, for example: alkanes, n (normal) and iso-alkanes, naphtha, toluene, xylene, benzene, diesel, natural gas, etc. Such solvent and/or steam 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.

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 100), e.g., according to previously obtained experimental data according to the process shown in FIG. 8. The acoustic generators 60 are operated at the determined resonant frequency at 204 to induce standing waves 26 in the pay 10, which enables heavy oil 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 62 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 62 determines at 212 whether or not the production phase is done, or otherwise requires the acoustic generators 60 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.

It can again be observed that the process shown in FIG. 9 can be implemented at point A during the mobilization phase of production, as a sub-routine to selectively target areas 36 of the pay 10 in order to selectively mobilize bitumen in areas 36 of the pay as shown in FIGS. 1A and 4A.

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 62, acoustic generators 60, acoustic resonators 22, 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.

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.

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.

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.

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.

Claims

1. A method for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the method comprising: energizing an area comprising a portion of the formation using a first set of at least one acoustic resonator positioned in the formation that generates acoustic waves at a predetermined resonant frequency of a geological material in the portion, wherein the acoustic waves generate standing waves within the portion that increase permeability of, and/or energize hydrocarbons in, the portion;ceasing operation of the first set of the at least one acoustic resonator; andcommencing energizing at least one additional portion of the formation by beginning to operate a second set of at least one acoustic resonator positioned in the at least one additional portion.

2. The method of claim 1, further comprising recovering a hydrocarbon containing fluid from the formation after energizing the area.

3. The method of claim 1, further comprising recovering a hydrocarbon containing fluid from the formation after energizing the at least one additional portion.

4. The method of claim 2, wherein the hydrocarbon containing fluid is recovered via gravity drainage.

5. The method of claim 1, wherein the operation of the first set of at least one acoustic resonator positioned in the portion is ceased after the area of the pay region is energized.

6. The method of claim 5, wherein the first set of at least one acoustic resonator is removed from the formation.

7. The method of claim 6, wherein the first set of at least one acoustic resonator is used in one or more of the at least one additional portion.

8. The method of claim 1, wherein at least three portions of the pay region are selectively energized over corresponding periods of time.

9. The method of claim 8, wherein at least one portion is selectively energized more than once.

10. The method of claim 1, wherein at least one portion of the pay region is energized such that both permeability of the formation is increased, and the hydrocarbon is mobilized for subsequent production.

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

12. The method of claim 11, wherein the formation comprises shale, and wherein increasing permeability in the pay region comprises creating fractures and/or microfractures in the shale using the acoustic standing waves.

13. The method of claim 1, wherein the hydrocarbon is recovered from the pay region using at least one wellbore used to position the first and/or second set of at least one acoustic resonator.

14. The method of claim 1, wherein the first and/or second set of at least one acoustic resonator is positioned in the pay region via a substantially vertically oriented wellbore.

15. The method of claim 14, wherein the energizing 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.

16. The method of claim 1, wherein the first and/or second set of at least one acoustic resonator is positioned in the pay region via a substantially horizontally oriented wellbore.

17. The method of claim 16, wherein energizing 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.

18. The method of claim 1, further comprising: predetermining the resonant frequency of the geological material in the pay region.

19. The method of claim 18, further comprising: operating the first and/or second set of at least one acoustic resonator at an additional resonant frequency of a geological material in the formation to achieve the additional resonant frequency.

20. The method of claim 1, wherein the first and/or second set of at least one acoustic resonator is powered by at least one acoustic generator from surface.

21. The method of claim 1, wherein a plurality of acoustic resonators are each powered by an acoustic generator from surface.

22. The method of claim 20, wherein the first and/or second set of at least one acoustic generator is coupled to a controller.

23. The method of claim 18, further comprising selecting the resonant frequency from a plurality of resonant frequencies of the geological material.

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

25. The method of claim 24, wherein a set of a plurality of resonant frequencies is determined based on the in situ testing.

26. The method of claim 23, wherein at least one resonant frequency of the geological material is determined using a drill core extracted from the formation rock.

27. The method of claim 1, 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.

28. The method of claim 2, wherein recovering the hydrocarbon from the pay region comprises applying an oil recovery technique.

29. The method of claim 28, wherein the oil recovery technique comprises generating standing waves within the pay region to mobilize a heavy oil in the pay region.

30. The method of claim 29, wherein the heavy oil is bitumen.

31. The method of claim 28, further comprising producing a bitumen containing fluid to surface using a substantially horizontally oriented production well positioned below the first and/or second set of at least one resonator.

32. The method of claim 31, 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.

33. The method of claim 28, further comprising injecting solvent into the pay region.

34. The method of claim 33, wherein the solvent is injected prior to operating the first and/or second set of at least one acoustic resonator to mobilize the heavy oil.

35. The method of claim 33, wherein the solvent is injected subsequent to operating the at least one acoustic resonator to mobilize the heavy oil.

36. The method of claim 33, wherein the solvent is injected during operation of the first and/or second set of at least one acoustic resonator to mobile the heavy oil.

37. The method of claim 28, wherein the oil recovery technique comprises a steam assisted gravity drainage (SAGD) technique.

38. A system for enabling hydrocarbons to be recovered from a hydrocarbon-bearing formation, the system comprising: a first set of at least one acoustic resonator positioned in an area comprising a portion of the formation, the first set of at least one acoustic resonator configured to energize the area by generating acoustic waves at a predetermined resonant frequency of a geological material in the portion, wherein the acoustic waves generate standing waves within the portion that increase permeability of, and/or energize hydrocarbons in, the portion;a second set of at least one acoustic resonator positioned in at least one additional portion of the formation, wherein the second set of at least one acoustic resonator is configured to commence energizing the at least one additional portion after ceasing operation of the first set of the at least one acoustic resonator; andat least one acoustic generator coupled to the first and second sets of acoustic resonators.

39. A method for enhanced hydrocarbon recovery from a hydrocarbon-bearing formation, the method comprising: energizing a first portion of the formation using an acoustic resonator positioned within the formation to generate acoustic waves at a predetermined resonant frequency of a geological material in the first portion of the formation, wherein the acoustic waves generate standing waves that increase permeability and/or energize hydrocarbons in the first portion of the formation;upon reaching a desired permeability and/or energization of the hydrocarbons, ceasing the energizing of the first portion of the formation and commencing a hydrocarbon production operation in the first portion;commencing energizing a second portion of the formation using an acoustic resonator and continuing such energizing until reaching a desired permeability and/or energization of hydrocarbons in the second portion, upon which energizing the second portion is ceased and a production operation is commenced; andrepeating the energizing followed by production operation selectively at multiple portions of the formation.