Patent Publication Number: US-2023160302-A1

Title: Short And Wideband Isolator For Acoustic Tools

Description:
BACKGROUND 
     For oil and gas exploration and production, a network of wells, installations and other conduits may be established by connecting sections of metal pipe together. For example, a well installation may be completed, in part, by lowering multiple sections of metal pipe (i.e., a casing string) into a wellbore, and cementing the casing string in place. In some well installations, multiple casing strings are employed (e.g., a concentric multi-string arrangement) to allow for different operations related to well completion, production, or enhanced oil recovery (EOR) options. From time to time, well installations and the subterranean formation in which the well installations are installed may be analyzed through measurement operations for any number of downhole operations. In some measurement operations, acoustic logging tools may be utilized. 
     Acoustic togging tools may be used to measure acoustic properties of a subterranean formations from which images, mechanical properties or other characteristics of the formations may be derived. Acoustic energy is generated by the acoustic logging tool and acoustic waves comprising periodic vibrational disturbances resulting from the acoustic energy propagating through the formation or the acoustic togging system are received by a receiver in the acoustic logging tool. Acoustic waves may be characterized in terms of their frequency, amplitude and speed of propagation. Acoustic properties of interest for formations may comprise compressional wave speed, shear wave speed, surface waves speed (e.g., Stoneley waves) and other properties. Acoustic images may be used to depict borehole wall conditions and other geological features away from the borehole. The acoustic measurements have applications in seismic correlation, petrophysics, rock mechanics and other areas. Acoustic measurements and thus acoustic images may be susceptible to direct coupling between the transmitter and receiver on the acoustic logging tool, which may degrade the acoustic image. 
     As the transmitter and receivers are physically connected by the tool body, direct coupling is acoustic waves propagating between the transmitter and receivers, at the speed of sound in the body of the acoustic logging tool. This speed of sound is much faster in solids, such as the body of the acoustic logging tool, other than that of the borehole fluids. Hence the acoustic waves traveling through the body will be received by the receivers earlier than the desired signals from the casing or borehole and overlay onto the latter. This phenomenon, direct coupling, is the common challenge to acoustic tools. An effective operation of the acoustic logging tools may be hindered by undesirable noise signals encountered downhole by the logging tools. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These drawings illustrate certain aspects of some examples of the present disclosure and should not be used to limit or define the disclosure. 
         FIG.  1    illustrates a system including an acoustic logging tool; 
         FIG.  2    illustrates a cross sectional view of an acoustic isolator; 
         FIG.  3    illustrates a cross sectional view of another acoustic isolator; 
         FIGS.  4 A- 5 D  are graphs illustrating acoustic energy attenuation for low frequencies with and without an acoustic isolator; and 
         FIGS.  5 A- 5 D  are graphs illustrating acoustic energy attenuation for high frequencies with and without an acoustic isolator. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure may generally relate to system and methods for an acoustic isolator disposed on a conveyance. The acoustic isolator may reduce the acoustic energy transferred through the body of the acoustic logging tool. This may reduce and/or prevent direct coupling between acoustic transmitters and acoustic receivers on the acoustic logging tool. 
       FIG.  1    illustrates an operating environment for an acoustic logging tool  100  as disclosed herein. Acoustic logging tool  100  may comprise a transmitter  102  and/or a receiver  104  that may be separated by an acoustic isolator  126 . In examples, there may be any number of transmitters  102 , any number of receivers  104 , and/or any number of acoustic isolators  126 , which may be disponed on acoustic logging tool  100 . Acoustic logging tool  100  may be operatively coupled to a conveyance  106  (e.g., wireline, slickline, coiled tubing, pipe, downhole tractor, and/or the like) which may provide mechanical suspension, as well as electrical connectivity, for acoustic logging tool  100 . Conveyance  106  and acoustic logging tool  100  may extend within casing string  108  to a desired depth within the wellbore  110 . Conveyance  106 , which may comprise one or more electrical conductors, may exit wellhead  112 , may pass around pulley  114 , may engage odometer  116 , and may be reeled onto winch  118 , which may be employed to raise and lower the tool assembly in the wellbore  110 . Signals recorded by acoustic logging tool  100  may be stored on memory and then processed by display and storage unit  120  after recovery of acoustic logging tool  100  from wellbore  110 . Alternatively, signals recorded by acoustic logging tool  100  may be conducted to display and storage unit  120  by way of conveyance  106 . Display and storage unit  120  may process the signals, and the information contained therein may be displayed for an operator to observe and stored for future processing and reference. Alternatively, signals may be processed downhole prior to receipt by display and storage unit  120  or both downhole and at surface  122 , for example, by display and storage unit  120 . Display and storage unit  120  may also contain an apparatus for supplying control signals and power to acoustic logging tool  100 . Typical casing string  108  may extend from wellhead  112  at or above ground level to a selected depth within a wellbore  110 . Casing string  108  may comprise a plurality of joints  130  or segments of casing string  108 , each joint  130  being connected to the adjacent segments by a collar  132 . 
       FIG.  1    also illustrates a typical pipe string  138 , which may be positioned inside of casing string  108  extending part of the distance down wellbore  110 . Pipe string  138  may be production tubing, tubing string, casing string, or other pipe disposed within casing string  108 . Pipe string  138  may comprise concentric pipes. It should be noted that concentric pipes may be connected by collars  132 . Acoustic logging tool  100  may be dimensioned so that it may be lowered into the wellbore  110  through pipe string  138 , thus avoiding the difficulty and expense associated with pulling pipe string  138  out of wellbore  110 . 
     In logging systems, such as, for example, logging systems utilizing the acoustic logging tool  100 , a digital telemetry system may be employed, wherein an electrical circuit may be used to both supply power to acoustic logging tool  100  and to transfer data between display and storage unit  120  and acoustic logging tool  100 . A DC voltage may be provided to acoustic logging tool  100  by a power supply located above ground level, and data may be coupled to the DC power conductor by a baseband current pulse system. Alternatively, acoustic logging tool  100  may be powered by batteries located within the downhole tool assembly, and/or the data provided by acoustic logging tool  100  may be stored within the downhole tool assembly, rather than transmitted to the surface during logging (corrosion detection). 
     Acoustic logging tool  100  may be used for excitation of transmitter  102 . As illustrated, one or more receiver  104  may be positioned on the acoustic logging tool  100  at selected distances (e.g., axial spacing) away from transmitter  102 . The axial spacing of receiver  104  from transmitter  102  may vary, for example, from about 0 inches (0 cm) to about 40 inches (101.6 cm) or more. In some embodiments, at least one receiver  104  may be placed near the transmitter  102  (e.g., within at least 1 inch (2.5 cm) while one or more additional receivers may be spaced from 1 foot (30.5 cm) to about 5 feet (152 cm) or more from the transmitter  102 . It should be understood that the configuration of acoustic logging tool  100  shown on  FIG.  1    is merely illustrative and other configurations of acoustic logging tool  100  may be used with the present techniques. In addition, acoustic logging tool  100  may comprise more than one transmitter  102  and more than one receiver  104 . For example, an array of receivers  104  may be used. Transmitters  102  may comprise any suitable acoustic source for transmitting (i.e., generating) acoustic waves downhole, including, but not limited to, monopole and multipole sources (e.g., dipole, cross-dipole, quadrupole, hexapole, or higher order multi-pole transmitters). Additionally, one or more transmitters  102  (which may comprise segmented transmitters) may be combined to excite a mode corresponding to an irregular/arbitrary mode shape. Specific examples of suitable transmitters  102  may comprise, but are not limited to, piezoelectric elements, bender bars, or other transducers suitable for generating acoustic waves downhole. Receiver  104  may comprise any suitable acoustic receiver suitable for use downhole, including piezoelectric elements that may convert acoustic waves into an electric signal. 
     Transmission of acoustic waves by the transmitter  102  and the recordation of signals by receivers  104  may be controlled by display and storage unit  120 , which may comprise an information handling system  144 . As illustrated, the information handling system  144  may be a component of the display and storage unit  120 . Alternatively, the information handling system  144  may be a component of acoustic logging tool  100 . An information handling system  144  may comprise any instrumentality or aggregate of instrumentalities operable to compute, estimate, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system  144  may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. Information handling system  144  may comprise a processing unit  146  (e.g., microprocessor, central processing unit, etc.) that may process EM log data by executing software or instructions obtained from a local non-transitory computer readable media  148  (e.g., optical disks, magnetic disks). The non-transitory computer readable media  148  may store software or instructions of the methods described herein. Non-transitory computer readable media  148  may comprise any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Non-transitory computer readable media  148  may comprise, for example, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk drive), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), and/or flash memory; as well as communications media such wires, optical fibers, microwaves, radio waves, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing. Information handling system  144  may also comprise input device(s)  150  (e.g., keyboard, mouse, touchpad, etc.) and output device(s)  152  (e.g., monitor, printer, etc.). The input device(s)  150  and output device(s)  152  provide a user interface that enables an operator to interact with acoustic logging tool  100  and/or software executed by processing unit  146 . For example, information handling system  144  may enable an operator to select analysis options, view collected log data, view analysis results, and/or perform other tasks 
     As noted above and illustrated in  FIG.  1   , transmitters  102  and receivers  104  are physically connected by the tool body of acoustic logging tool  100 . During measurement operations, transmitter  102  may transmit one or more acoustic waves, as discussed above. At least a part of these acoustic waves may propagate between transmitter  102  and receivers  104  through the tool body of acoustic logging tool  100 , this is defined as direct coupling. The acoustic waves may propagate at the speed of sound through the tool material, which may be, for example, steel. The speed of sound through a solid material, such as steel, is much faster than that of the speed of sound through liquids, such as borehole fluids. Thus, acoustic waves may be received by receivers  104  earlier than the desired acoustic signals that may have propagated though casing string  108 , wellbore  110 , and/or pipe string  138 . Acoustic isolator  126  may operate and function to prevent direct coupling between transmitter  102  and receiver  104  through a variety of mechanisms. 
       FIG.  2    illustrates a cut away view of acoustic isolator  126 . Acoustic isolator  126  may decrease (e.g., minimize or eliminate) undesirable acoustic signals propagated through acoustic logging tool  100 , e.g., the tool mode. Additionally, acoustic isolator  126  may be implemented in any application in which acoustic waves transmitted between a transmitter  102  and receiver  104  (e.g., referring to  FIG.  1   ) fixed longitudinally apart on the same tool body, are to be isolated. Implementing the techniques described here may increase an efficiency of acoustic isolator  126  and reduce a length of the tool resulting in increase in production speed, decrease in production cost, decrease in manufacturing issues and increase in log data quality. The reduced tool mode may also increase the range of formation slowness that acoustic isolator  126  may measure (e.g., formation with faster compressional and shear wave speed). As illustrated, acoustic isolator  126  comprises annular chambers  202  formed in acoustic isolator body  200  of acoustic isolator  126 . Annular chambers  202  may be positioned along longitudinal axis  204  of acoustic isolator  126 . The size, position, and number of annular chambers  202  in acoustic isolator  126  may be selected to attenuate acoustic energy across a selected frequency range. The creation of the inner and outer grooves for the isolator may be done by conventional machining. It also can be done via  3 D print technology, in which the isolator, sometimes including the transmitter and receiver sections, can be directly printed out. 
       FIG.  2    further illustrates acoustic isolator  126  that has cut acoustic isolator body  200  from both inside and outside, to create both annular chambers  202  and annular grooves  210 . In examples, acoustic isolator  126  may range in length from about 2″ to about one foot (about 5 cm to about 31 cm). As noted above, annular chambers  202  are cut inside of acoustic isolator body  200  and annular grooves  210  are cut on outer surface  206  of acoustic isolator body  200 . The creation of annular chambers  202  inside of acoustic isolator body  200  and annular grooves  210  outside of acoustic isolator body  200  may be performed by conventional machining. In other examples, annular chambers  202  and annular grooves  210  may be formed via  3 D print technology, in which acoustic isolator  126 , sometimes including the transmitter and receiver sections, may be directly printed out. In examples, acoustic isolator body  200  comprises at least one pair of annular chamber  202  and annular groove  210 . This may create a passage  208  in acoustic isolator body  200 . Passage  208  may form a zigzag path in which acoustic waves may travel. Passage  208  may attenuate acoustic energy and thus may prevent acoustic waves from traversing through the entire length of acoustic isolator  126 . 
     Annular groove  210  may be formed to take many different shapes and/or sizes. For example, annular groove  210  may be formed perpendicular and/or parallel to outer surface  206 , as illustrated in  FIG.  2   , or may be formed at an angle to outer surface  206 . Additionally, as illustrated in  FIG.  3   , annular groove  210  may comprise horizontal annular grooves  300 , which may range from about 0″ to about 5″ (about 0 cm to about 13 cm) and may extend the length of passage  208  and may further help in attenuating acoustic energy from acoustic waves. Referring back to  FIG.  2   , annular groove  210  may have a depth d that may range from about 0.1″ to about 3″ (about 0.25 cm to about 8 cm) and may allow for acoustic isolator  126  to maintain mechanical strength. Width of annular groove  210 , ot, may be about 0.1″ and range from about 0.01″ to about 3″ (about 0.25 cm to about 8 cm), to minimize the strength reduction on acoustic isolator  126  and reduce the overall length of acoustic isolator  126 . The width of annular chambers  202 , it, may be larger than, ot, but may be about 0.3″ and range from about 0.1″ to about 2″ to keep acoustic isolator  126  short. Additionally, spacing, a, between annular chamber  202  and annular groove  210  may be about 0.3″ and range from about 0.1″ to about 2″ (about 0.25 cm to about 5 cm), which may narrow passage  208  and further help attenuate acoustic waves that may travers through passage  208 . In examples, depth of annular groove  210 , d, may be equal or larger than surface depth, e, of outer surface  206 . This may also narrow passage  208  and further help attenuate acoustic waves that may travers through passage  208 . As noted above, there may be a plurality of annular grooves  210  disposed across the length of acoustic isolator  126 . In examples, annular grooves  210  may be disposed between each annular chamber  202 . However, there may be multiple annular grooves  210  disposed between each annular chamber  202 . Additionally, zero, one, or a plurality of annular grooves  210  may be disposed between an annular chamber  202  and either a first end  212  or second end  214  of acoustic isolator  126 . Distance, s, between each annular groove  210  may be equal between each annular groove  210  and/or may vary between each annular groove  210 . In examples, distance, s, may be about 1″ (about 2.5 cm) and may range from about 0.3″ to about 2″ (about 0.75 cm to about 5 cm), which may allow for acoustic isolator  126  to remain shorter in overall length, l. Although not illustrates, acoustic isolator  126  may be housed in a sleeve to prevent borehole fluid from entering any of annular grooves  210 . However, in examples, annular grooves  210  may fill with downhole fluid, tool oil, formation fluid, and/or the like, which may assist in attenuation of acoustic energy. 
       FIGS.  4 A- 5 D  are graphs of simulated data to show acoustic energy reduction utilizing the design of acoustic isolator  126  show in  FIGS.  2  and  3   .  FIGS.  4 A- 4 D  illustrate acoustic energy, first wavelet  400  of an acoustic waves illustrates the acoustic energy without acoustic isolator  126 . Utilizing acoustic isolator  126  of about 6″ in length, acoustic energy may be reduced significantly, or more than 30 dB in this case.  FIGS.  4 A- 4 D  illustrate comparisons of first wavelet  400  and second wavelet  402 . Second wavelet  402  illustrates acoustic energy using acoustic isolator  126 . Each graph in  FIGS.  4 A- 4 D  may comprise an input signal is at 10 to 30 kHz, where the horizontal axis is sampling points in time domain, and the vertical axis is amplitude of the received signals. As noted above, acoustic isolator  126  may comprise passage  208  (e.g., referring to  FIG.  2   ) that may form a zigzag path. This type of path may allow be effective for higher frequency. 
       FIGS.  5 A- 5 D , illustrate acoustic energy, first wavelet  500  of an acoustic waves illustrates the acoustic energy without acoustic isolator  126 . Utilizing acoustic isolator  126  of about 6″ in length, acoustic energy may be reduced significantly, or more than 30 dB in this case.  FIGS.  5 A- 5 D  illustrate comparisons of first wavelet  500  and second wavelet  502 . Second wavelet  502  illustrates acoustic energy using acoustic isolator  126 . Each graph in  FIGS.  4 A- 4 D  may comprise an input signal is at 30 to 50 kHz, where the horizontal axis is sampling points in time domain, and the vertical axis is amplitude of the received signals. As noted above, acoustic isolator  126  may comprise passage  208  (e.g., referring to  FIG.  2   ) that may form a zigzag path. This type of path may allow be effective for attenuation of higher frequency. 
     Although acoustic energy attenuation may be achieved via a short acoustic isolator  126 , for example, from about 2″ to about one foot (about 5 cm to about 31 cm), a longer acoustic isolator  126  may be used by using the disclosed design, with both annular chambers  202  and annular grooves  210  to create zigzag passage  208  for acoustic energy to traverse. Additionally, annular grooves  210  may be filled with other material, for example, plastics, rubber, tungsten rubber composite. 
     Improvements over current technology comprise methods and systems that may incorporate annular chambers and annular grooves as described above. Utilizing annular chambers and annular grooves may form zigzag passage for acoustic energy to traverse. The methods and system above may attenuate acoustic energy over short sections of an acoustic isolator. In examples, acoustic isolator may range in length from about 2″ to about one foot (about 5 cm to about 31 cm), while current technology requires acoustic isolators may are over a foot in length (31 cm). In addition, this methods and systems may operate to attenuate acoustic energy in a wideband frequency. The systems and methods disclosed herein may comprise any of the various features of the systems and methods disclosed herein, including one or more of the following statements. 
     Statement 1: An acoustic isolator may comprise a body, one or more annular chambers formed inside the body of the acoustic isolator and positioned along a longitudinal axis of the acoustic isolator, an annular groove formed on an outer surface of the body of the acoustic isolator, and a passage disposed between the one or more annular chambers and the annular groove. 
     Statement 2. The acoustic isolator of statement 1, wherein the passage is a zigzag passage between the one or more annular chambers and the annular groove. 
     Statement 3. The acoustic isolator of any preceding statements 1 or 2, wherein the annular groove is disposed between a first annular chamber and a second annular chamber. 
     Statement 4. The acoustic isolator of any preceding statements 1-3, wherein the annular groove is disposed between a first end of the acoustic isolator and the one or more annular chambers. 
     Statement 5. The acoustic isolator of statement 4, wherein the annular groove is disposed between a second end of the acoustic isolator and the one or more annular chambers. 
     Statement 6. The acoustic isolator of any preceding statements 1-4, wherein the annular groove is perpendicular to the outer surface of the body of the acoustic isolator. 
     Statement 7. The acoustic isolator of statement 6, wherein the annular groove comprises one or more horizontal annular grooves. 
     Statement 8. The acoustic isolator of any preceding statements 1-4 or 6, wherein the annular groove is angled to the outer surface of the of the body of the acoustic isolator. 
     Statement 9. The acoustic isolator of statement 8, wherein the annular groove comprises one or more horizontal annular grooves. 
     Statement 10. The acoustic isolator of any preceding statements 1-4, 6, or 8, further comprising a plurality of annular grooves. 
     Statement 11. The acoustic isolator of statement 10, wherein at least one of the plurality of annular grooves are disposed between each of the one or more annular chambers. 
     Statement 12. The acoustic isolator of statement 10, wherein a distance between each of the plurality of annular grooves is from about 0.3″ to about 2″. 
     Statement 13. The acoustic isolator of statement 10, wherein a distance between each of the plurality of annular grooves varies between each of the plurality of annular grooves. 
     Statement 14. The acoustic isolator of any preceding statements 1-4, 6, 8, or 10, wherein the annular groove is filled with a material. 
     Statement 15. The acoustic isolator of statement 14, the material is a plastic, a rubber, tungsten, or a rubber composite. 
     Statement 16. A method may comprise transmitting an acoustic wave from a transmitter disposed on an acoustic logging tool into a subterranean formation, receiving an acoustic signal from the subterranean formation with a receiver disposed on the acoustic logging tool, and attenuating a second acoustic wave that moves between the transmitter and the receiver and through an acoustic isolator. The acoustic isolator may comprise a body, one or more annular chambers formed inside the body of the acoustic isolator and positioned along a longitudinal axis of the acoustic isolator, an annular groove formed on an outer surface of the body of the acoustic isolator, and a passage disposed between the one or more annular chambers and the annular groove. 
     Statement 17. The method of statement 16, wherein the passage is a zigzag passage between the one or more annular chambers and the annular groove. 
     Statement 18. The method of any preceding statements 16 or 17, wherein the annular groove is disposed between a first annular chamber and a second annular chamber. 
     Statement 19. The method of any preceding statements 17 or 18, wherein the annular groove is disposed between a first end of the acoustic isolator and the one or more annular chambers. 
     Statement 20. The method of statement 19, wherein the annular groove is disposed between a second end of the acoustic isolator and the one or more annular chambers. 
     The preceding description provides various examples of the systems and methods of use disclosed herein which may contain different method steps and alternative combinations of components. It should be understood that, although individual examples may be discussed herein, the present disclosure covers all combinations of the disclosed examples, including, without limitation, the different component combinations, method step combinations, and properties of the system. It should be understood that the compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. 
     For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited. 
     Therefore, the present examples are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular examples disclosed above are illustrative only, and may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual examples are discussed, the disclosure covers all combinations of all of the examples. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. It is therefore evident that the particular illustrative examples disclosed above may be altered or modified and all such variations are considered within the scope and spirit of those examples. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.