JP2013140134A - Device and method for attenuating acoustic signals - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide methods and devices for attenuating acoustic signals traveling within a body.SOLUTION: A device includes a body and at least one acoustic attenuator disposed along the body. The attenuator includes a cavity and granular particles disposed within the cavity. A liquid is also disposed within the cavity. A restrictor applies a stress to the granular particles within the cavity.

Description

  The present invention relates to acoustic signals, and more particularly to attenuating acoustic signals.

  In the oil and gas industry, it is usually possible to explore underground layers with logging tools to determine formation characteristics, which can be used to predict or evaluate the profitability and productivity of subsequent excavation or production operations. In many cases, an acoustic logging tool is used to measure the acoustic properties of the formation, and this tool can be used to obtain other properties of the formation.

US Pat. No. 5,852,587 US Pat. No. 6,643,221

Valenza et al., “Dynamic Effective Mass of Granular Media and the Attenuation of Structure-Born Sound”, Phys. Rev. E80 (2009) 053304 Valenza et al., “Effect of Granular Media on the Vibrational Response of a Resonant Structure”, J. et al. Acoustic. Soc. Am. 128,2768 (2010)

  Such acoustic logging tools can include an acoustic transmitter for transmitting acoustic signals into the formation and an acoustic receiver for receiving acoustic signals returning from the formation. A common problem faced by acoustic logging tools is that sometimes the components of the acoustic signal are transmitted directly from the transmitter to the receiver through the tool body. This component of the acoustic signal does not provide useful information about the formation, but rather generates signal noise that interferes with useful signals from the formation. Conventionally, there are solutions to this problem, but these solutions cannot sufficiently attenuate a wide range of acoustic frequencies.

  Exemplary embodiments relate to an apparatus for attenuating an acoustic signal. In one embodiment, such a device includes a body and a plurality of attenuators (eg, at least one attenuator) disposed along the body. The acoustic attenuator includes a cavity. A liquid and a granular medium (such as a plurality of granular particles) are disposed in the cavity. The attenuator also includes a restrictor for applying stress to the granular particles in the cavity.

  In some embodiments, multiple acoustic attenuators are placed along the body. Some of these attenuators apply stress to the granular particles and some others apply different values of stress. In this way, the acoustic attenuator attenuates different acoustic frequencies.

  Exemplary embodiments also relate to a logging tool for performing acoustic surveys of underground layers traversed by a borehole. The logging tool includes a tool body extending in the longitudinal direction. A plurality of acoustic transmitters are arranged at the vertical position of the main body, and a plurality of acoustic receivers are arranged at different vertical positions of the main body. The acoustic logging tool also includes a plurality of acoustic attenuators located between the acoustic transmitter and the acoustic receiver. The attenuator includes a cavity disposed within the tool body. A granular medium and a liquid are disposed in the cavity. The liquid is configured to cover the granular particles in the cavity. The attenuator also includes a restrictor for applying stress to the granular particles in the cavity.

  In some embodiments, multiple acoustic attenuators are placed along the tool body. Some of these attenuators apply stress to the granular particles and some others apply different values of stress. In this way, the acoustic attenuator attenuates different acoustic frequencies.

  Exemplary embodiments also relate to a method for attenuating an acoustic signal passing through a body. The method includes disposing a granular medium (such as a plurality of particles) in a cavity disposed along the body and applying stress to the granular particles in the cavity. In some embodiments, the stress applied to the granular particles is adjusted to attenuate certain frequencies of the acoustic signal.

  The exemplary embodiment also relates to a method for predicting the attenuation characteristics of a body including an attenuator with a granular medium. The method includes determining an effective mass of a granular medium to which stress is applied. This effective mass is used to determine the effective density of the body. This effective density is used to determine the body delay. This process can be repeated over a plurality of different applied stresses.

  Those skilled in the art will more fully appreciate the advantages of the various embodiments of the present disclosure from the following Detailed Description, described below with reference to the drawings summarized below.

1 is a schematic view of a drilling assembly according to one embodiment of the present disclosure. FIG. 1 is a schematic view of a tool body according to one embodiment of the present disclosure. FIG. 1 is a schematic diagram of an attenuator according to one embodiment of the present disclosure. FIG. FIG. 6 is a schematic diagram of an attenuator according to another embodiment of the present disclosure. FIG. 6 is a schematic diagram of an attenuator according to another embodiment of the present disclosure. FIG. 6 is an assembly diagram of the attenuator of FIG. 5. FIG. 6 is a schematic diagram of an attenuator according to yet another embodiment of the present disclosure. FIG. 8 is an assembly diagram of the attenuator of FIG. 7. FIG. 6 is a schematic diagram of an attenuator according to another particular embodiment of the present disclosure. FIG. 6 is a schematic diagram of an attenuator according to yet another embodiment of the present disclosure. FIG. 6 is a schematic diagram of an attenuator according to another exemplary embodiment of the present disclosure. 2 is a schematic view of an attenuator coupled to a tool body, according to one embodiment of the present disclosure. 2 is a plot of attenuation of a tool body versus frequency, according to one embodiment of the present disclosure. 6 is a plot of tool body attenuation versus frequency according to another embodiment of the present disclosure. FIG. 6 is a schematic view of a tool body according to another embodiment of the present disclosure. It is sectional drawing of the tool main body of FIG. FIG. 6 is a schematic view of a tool body according to another embodiment of the present disclosure. FIG. 6 is a schematic view of a tool body according to yet another embodiment of the present disclosure. It is sectional drawing of the tool main body of FIG. FIG. 4 illustrates an attenuator arrangement according to some embodiments of the present disclosure. FIG. 4 illustrates an attenuator arrangement according to some embodiments of the present disclosure. FIG. 4 illustrates an attenuator arrangement according to some embodiments of the present disclosure. FIG. 3 illustrates an acoustic tool according to one embodiment of the present disclosure. 2 is a plot of dissipation capacity versus frequency according to one embodiment of the present disclosure. 4 is a plot of attenuation versus frequency according to one embodiment of the present disclosure.

  Exemplary embodiments of the present invention relate to a method and apparatus for attenuating a wide range of acoustic signal frequencies propagating through a tool body. To this end, various embodiments of the present invention place liquid and granular media in cavities located along the tool body. Next, stress is applied to the granular medium. This applied stress can be adjusted so that the granular medium attenuates a particular frequency of the acoustic signal. In certain embodiments, multiple cavities are used to adjust individual cavities to attenuate different ranges of frequencies. In this way, some embodiments of the invention can be adjusted to attenuate a wide range of acoustic signal frequencies. Details of various embodiments are described below.

  FIG. 1 illustrates a drilling assembly 100 according to one embodiment of the present invention. The drilling assembly 100 includes a drilling rig 102 disposed on the borehole 104. The drilling rig 102 includes a drilling string 106 with a downhole acoustic logging tool 108. The downhole acoustic logging tool 108 is used to conduct an acoustic survey of the underground layer 110 that the borehole 104 traverses. In one embodiment, the acoustic logging tool 108 is part of the simultaneous excavation logging tool and is configured to investigate the underground layer while performing the excavation operation. However, in other embodiments, the acoustic logging tool 108 does not rely on excavation operations.

  FIG. 2 illustrates a tool body 200 according to one embodiment of the present invention. In the particular embodiment shown in FIG. 2, the tool body 200 is a body that is configured to be disposed within a borehole and that extends in the longitudinal direction of the cavity. Tool body 200 includes an outer surface 202 defined by an outer diameter and an inner surface 204 defined by an inner diameter. In one particular embodiment, the tool body 200 is the drill collar of the drilling tool. In such embodiments, drilling mud flows down into the borehole through the inner diameter of the tool body 200 and rises between the borehole formation and the outer surface 202 of the body. In addition, the description regarding the relative shape of the tool main body 200, a dimension, and a size is an illustration, and is not for limiting the scope of the present invention.

  Tool body 200 also includes an acoustic sensor (such as at least one acoustic transmitter 206 and at least one acoustic receiver 208) disposed on the tool body. In some embodiments, transmitter 206 and receiver 208 are vertically spaced from each other. Tool body 200 also includes an attenuation portion 210 defined by the volume of tool body 200 between transmitter 206 and receiver 208. The attenuation portion 210 includes at least one attenuator 212 disposed along the tool body 200 for attenuating acoustic signals propagating through the tool body. In the embodiment shown in FIG. 2, a plurality of attenuators 212 are arranged around the outer surface 202 of the tool body 200.

  The various embodiments of the present invention are not limited to the attenuator arrangement shown in FIG. For example, an attenuator can be placed adjacent to one or more acoustic sensors (on the backside, perimeter and bottom of the sensor, etc.). In other embodiments, the attenuator can be positioned along the tool body above or below the attenuation portion (such as below the transmitter and / or above the receiver). Such an embodiment can help reduce acoustic signals returning from the surrounding formations to the tool body.

  FIG. 3 is a cross-sectional view of an attenuator 300 according to one embodiment of the present invention. The attenuator includes a cavity 302 disposed in the tool body 304. The cavity 302 has a cylindrical shape and is disposed within the outer surface 305 of the tool body. In additional or alternative embodiments, the cavity 302 may be located on the inner surface of the tool body. In various other embodiments, the cavity 302 is located outside the tool body. Further, the cavity 302 can take a variety of other forms. For example, the cavity 302 can be rectangular or elliptical. Cavity 302 can also form a channel extending longitudinally or radially around the outer or inner surface of tool body 304.

  As shown in FIG. 3, a granular medium 306 (such as a plurality of granular particles) is disposed in the cavity 302. In various embodiments, the size of the granular particles 306 is significantly smaller than the wavelength to be attenuated in the tool body 304. In certain embodiments, the granular particles of granular media 306 are between 5 microns and 500 microns. However, these sizes are only examples. In another example, the granular media 306 includes particles up to 5000 microns in size. The size parameters of the granular particles can vary. The ranges and sizes disclosed herein are not intended to limit the scope of the invention.

  Also, in various embodiments of the present invention, the granular media 306 is selected such that the particles are stable at high borehole temperatures. For this purpose, granular particles can be formed from metallic materials such as aluminum or tungsten and / or various other materials such as silicon, cast iron or tungsten carbide. The particulate media 306 can also be selected such that there is a mixture of different sized particles and / or particulate materials in the cavity 302. The exemplary materials disclosed herein are not intended to limit the scope of the invention. The material composition of the granular particles may vary other than the examples shown in this specification.

  Another particle property that can be considered is particle shape. For example, in one particular embodiment, the particulate media 306 includes substantially symmetric (such as spherical) particles that are rounded and / or smooth on the surface. In other embodiments, the particles are asymmetric and have an uneven surface and / or jagged edges. As explained, the shape of the granular particles may vary. The exemplary shapes disclosed herein are not intended to limit the scope of the invention.

  In the particular example of FIG. 3, the cavity 302 also includes a liquid 308 such as water, oil, drilling fluid, fluorocarbon lubricant, polymer and / or gel. In one particular example, the liquid 308 is a silicone oil such as polydimethylsiloxane. In various exemplary embodiments, the liquid 308 is a viscous liquid that has a higher viscosity value than water (eg, 1 cSt). In another specific embodiment, the liquid 308 has a viscosity of 2-1,000,000 cSt at a specific application temperature. For example, for consumer goods applications, the liquid 308 can have a viscosity of 2-1,000,000 cSt at room temperature. For borehole applications, the liquid 308 can have a viscosity of 2 to 1,000,000 cSt at a borehole temperature (such as 100-175 ° C.). The compositions and ranges disclosed herein are not intended to limit the scope of the invention. The composition and viscosity parameters of the liquid 308 may vary beyond the examples shown herein. For example, in some embodiments, the liquid 308 can have a lower viscosity than water.

  In one exemplary embodiment, the volume of liquid 308 in cavity 302 is sufficient to cover at least a portion of particulate medium 306 with liquid. In such an embodiment, the volume of liquid 308 is selected so that liquid 308 does not penetrate particulate medium 306. For example, in one particular embodiment, 110 grams of tungsten powder is covered with 80 mg of 5000 cSt silicone oil. For this purpose, in various embodiments, the volume ratio of the liquid 308 in the cavity 302 relative to the granular medium 306 is 0.001% to 5%. In other embodiments of the present invention, the liquid 308 penetrates the particulate medium 306. The ratios and ranges disclosed herein are examples and are not intended to limit the scope of the invention. The liquid volume and particulate media volume parameters may vary beyond the ratios and ranges described herein.

  As shown in FIG. 3, the attenuator 300 also includes a restrictor 310 configured to apply stress to the granular media 306. The inventors have realized that by adjusting the stress applied to the granular medium 306, the attenuator 300 can be adjusted to attenuate a particular frequency of the acoustic signal.

  The stress applied to the granular medium 306 by the restrictor 310 is an effective stress. Effective stress is defined as the external stress applied by the restrictor minus the pore pressure (such as atmospheric pressure). The stress applied to the granular medium by the restrictor 310 is at least greater than 0 Pa. In the particular example shown in FIG. 3, the restrictor 310 includes a threaded male cap 312 configured to mate with a female thread in the opening 314 of the cavity 302. When the cap 312 is screwed into the opening 314 of the cavity, the cap contacts the granular medium 302 and applies stress to the granular medium. The stress applied to the granular media 302 can be adjusted by turning the cap 312 and moving the cap into and out of the cavity 302 (such as by adjusting the displacement of the cap). In various exemplary embodiments, the stress applied to the granular medium 302 is between 1 Pa and 5 MPa. The stress applied to the granular medium 302 may be varied outside this range. Such examples and ranges are not intended to limit the scope of the invention.

  FIG. 4 illustrates an attenuator 400 according to another embodiment of the present invention. The attenuator 400 is similar to the attenuator disclosed in FIG. 3 except that the restrictor 402 in FIG. 4 includes a corresponding medium 404 such as a plug. This corresponding medium 404 is placed between the threaded cap 406 and the granular medium 408. As the threaded cap 406 is turned into the cavity 410, the corresponding media 404 applies stress to the granular media 408. When the corresponding medium 404 comes to a predetermined position, a constant stress is applied to the granular medium 408. Corresponding media 404 can be made from a variety of different types of materials, such as rubber or silicon. By selecting from one or more corresponding media that apply different predetermined values of stress (such as by using materials having different moduli of elasticity), the stress applied to the granular media 408 can be adjusted. Corresponding media 404 can also have a variety of different geometries (such as thickness). In this way, the stress applied to the granular media 408 can be adjusted by selecting from one or more different media shapes (eg, using a thicker corresponding media 404). Stress also increases).

  5-6 illustrate an attenuator 500 according to another embodiment of the present invention. In FIG. 5 to FIG. 6, the corresponding medium 404 includes a piston 502 and a spring 504. A spring 504 is disposed between the threaded cap 506 and the piston 502. As the threaded cap 506 is turned into the cavity 508, the spring 504 compresses and applies stress to the piston 502, which further applies stress to the granular media 510. FIG. 6 shows an assembly view of the threaded cap 506, the spring 504, and the piston 502. When assembled, the spring 504 applies a constant stress to the granular medium 510 through the piston 502. In one particular embodiment, the spring 504 is a helical coil formed from a metallic material. The piston 502 can also be formed from a metallic material. By selecting from one or more springs that apply different predetermined values of stress (eg, using springs with different spring constants), the stress applied to the granular media 510 can be adjusted.

  Exemplary embodiments of restrictors that use compatible media (such as springs and rubber materials) have the advantage of applying a constant stress within the borehole environment. In many cases, the vibration of the tool in the borehole environment reduces the total volume of the granular media over time, resulting in a decrease in stress applied to the granular media. A corresponding medium, such as a spring, automatically adapts to take into account this reduction in volume and consequently continues to apply a constant stress to the granular medium.

  7-8 illustrate an attenuator 700 according to yet another embodiment of the present invention. 7-8, the restrictor structure 702 does not have male and female threads. Instead, this particular embodiment relies on a heat treatment such as a welding or brazing process to secure the cap 704 to the opening 706 of the cavity 708. FIG. 8 shows an assembly view of the cap 704, the spring 710, and the piston 712. The attenuator includes a joint 714 formed between the cap and cavity 708 by heat / pressure treatment.

  FIG. 9 illustrates an attenuator 900 according to another specific embodiment of the invention. The embodiment of FIG. 9 includes two variations of the embodiment shown in FIGS. For example, the cap 902 is fixed to the opening 904 of the cavity 906 using an interference fit instead of heat treatment. In other words, the diameter of the cap 902 is slightly larger than the diameter of the opening 904, and a force is applied to fix the cap in the opening. Also, in contrast to the flat cavity wall 716 as shown in FIGS. 7-8, in the embodiment of FIG. 9, the cavity wall 908 includes a flare 910. The flare 910 increases the surface area of the cavity 906 that contacts the granular media 912 and the liquid 914. Such a flare 910 can further facilitate attenuation of the acoustic signal. In various embodiments of the invention, the amplitude and / or frequency of the flare 910 is limited to less than the size of the granular particles. A cavity having such an “uneven” surface can potentially better couple acoustic signals to the granular media 912.

  FIG. 10 shows an attenuator 1000 according to yet another embodiment of the present invention. In the particular embodiment shown, the restrictor 1002 includes a cap 1004 with a protrusion 1006 having a particular thickness. A mechanical fastener 1012 such as a screw or rivet is used to secure the cap 1002 to the opening 1008 of the cavity 1010. The restrictor 1002 also includes a corresponding bag or container 1014 (made from rubber, silicone, or the like) that at least partially includes the particulate medium 1016. A corresponding bag 1010 is placed in the cavity 1010 and the cap 1004 is secured to the opening 1008 of the cavity 1010. In this way, the protrusion 1006 applies stress to the corresponding bag 1014, which further applies stress to the granular medium 1016. For example, the stress applied to the granular medium 1016 can be adjusted by adjusting the thickness of the protrusion 1006, adjusting the elastic coefficient of the protrusion 1006, and / or adjusting the elastic coefficient of the corresponding bag 1014.

  FIG. 11 illustrates an attenuator 1100 according to another exemplary embodiment of the present invention. In FIG. 11, the protrusion 1006 is replaced with a piston 1102 and a spring 1104. When assembled, the spring 1104 applies a force to the piston 1102, which further applies stress to the corresponding bag 1106 and the granular media 1108 in the bag. For example, the stress applied to the granular media 1108 can be adjusted by adjusting the spring constant and / or adjusting the elastic modulus of the corresponding bag.

  3 to 11, the attenuator is formed integrally with the tool body. In other words, a portion of the tool body is used to contain the granular media and liquid. However, in various other embodiments, the attenuator can be a different member coupled to the tool body (such as coupled to the outer or inner surface of the tool body).

  FIG. 12 illustrates an attenuator 1200 coupled to a tool body 1202 according to one embodiment of the present invention. The attenuator 1200 is disposed in the through hole 1204 of the tool body. Attenuator 1200 includes a restrictor 1206 that defines a cavity 1207. The cavity 1207 includes a liquid 1208 and a granular medium 1210. The restrictor 1206 is configured to apply stress to the granular media 1210. In one embodiment, the attenuator 1200 is coupled to the tool body 1202 after the granular media 1210 is filled into the restrictor 1206. For example, stress can be applied to the granular media 1210 by shrink fitting a restrictor 1206 around the liquid 1208 and the granular media 1210. In another example, at least one wall of the restrictor 1206 is intentionally deformed so that the deformation applies stress to the granular media 1210. In the particular embodiment of FIG. 12, the attenuator 1200 also includes a retaining ring 1212 and an O-ring seal 1214. Retaining ring 1212 secures the container in place within through-hole 1204 and O-ring seal 1214 prevents drilling fluid or other contaminants from flowing through through-hole 1204.

  As noted above, the inventors have realized that the attenuation characteristics of a particular attenuator are a function of the stress applied to the granular media within the attenuator. In an exemplary embodiment of the invention, the tool body includes a plurality of attenuators that are adjusted to different stress values so that at least some attenuate the different frequencies of the acoustic signal. In this way, various embodiments of the present invention can attenuate a wide range of acoustic frequencies that propagate through the tool body.

曲線１３０２で示すように、表１に従って調整した減衰器は、８〜１１ｋＨｚの周波数を効果的に４０ｄＢ／ｍも減衰させる。これに対し、曲線１３０４は、キャビティが空の（例えば、液体又は粒状媒体が含まれていない）ツール本体の減衰特性を示す。 FIG. 13 illustrates a tool body attenuation vs. frequency plot 1300 according to one embodiment of the present invention. In this particular example, the tool body includes a plurality of attenuators. These attenuators are adjusted to different applied stresses according to Table 1. The attenuator has a total volume (eg, the sum of the volumes of each cavity), and Table 1 shows the volume fraction of the total volume adjusted to the individual applied stress.
Table 1

As shown by the curve 1302, the attenuator adjusted according to Table 1 effectively attenuates the frequency of 8 to 11 kHz by 40 dB / m. In contrast, curve 1304 shows the damping characteristics of a tool body with an empty cavity (eg, no liquid or particulate media is included).

曲線１４０２で示すように、表２に従って調整した減衰器は、５〜１４ｋＨｚの周波数を効果的に減衰させる。また、この範囲では、減衰は３０ｄＢ／ｍほどである。曲線１４０４は、キャビティが空の（例えば、液体又は粒状媒体が含まれていない）ツール本体の減衰特性を示す。 FIG. 14 illustrates a tool body attenuation vs. frequency plot 1400 in accordance with another embodiment of the present invention. In this case, the tool body includes a plurality of attenuators adjusted to different applied stresses according to Table 2. Similar to Table 1, Table 2 also shows the volume fraction of the total volume adjusted to each applied stress.
Table 2

As shown by curve 1402, the attenuator tuned according to Table 2 effectively attenuates the frequency of 5-14 kHz. In this range, the attenuation is about 30 dB / m. Curve 1404 shows the damping characteristics of a tool body with an empty cavity (eg, no liquid or particulate media is contained).

  FIG. 2 shows an example of a tool body 200 that includes a plurality of attenuators 212, at least some of which are adjusted to different stress values to attenuate different frequencies of the acoustic signal. In FIG. 2, the attenuators 212 are arranged to form a plurality of circumferential rows separated by a selected longitudinal interval. In particular examples, one or more (such as five, ten, or fifteen) attenuations in which each row is azimuthally arranged at substantially equal intervals around the longitudinal axis of the tool body 200. A container 212 may be included. The plurality of attenuators 212 can be classified into a plurality of different sections based on the attenuation characteristics of the attenuators. For example, in the first compartment 214, the attenuator 212 is adjusted to attenuate a frequency of 2-4 kHz. The attenuator 212 in this first compartment 214 can be adjusted so as not to apply stress to the granular media. In the second compartment 216, a slight stress is applied to the granular media and thus the attenuator 212 is adjusted to attenuate frequencies between 4 kHz and 6 kHz. In the third compartment 218, greater stress is applied to the granular media, and the attenuator 212 is therefore adjusted to attenuate frequencies between 6 kHz and 8 kHz. Then, in the fourth compartment 220, even greater stress is used to adjust the attenuator 212 to attenuate frequencies above 8 kHz. In this way, the attenuation portion 210 of the tool body 200 is configured to attenuate a wide range of acoustic signal frequencies (such as 2-10 kHz).

  It should be noted that exemplary embodiments of the present invention are not limited to such a “partitioned” arrangement of attenuators. For example, in other embodiments, the tuned attenuator is not separated by various compartments based on the attenuation characteristics of the attenuator. In other embodiments, differently tuned attenuators are placed between each other. In yet another embodiment, differently tuned attenuators are randomly placed between each other.

  15 and 16 show a tool body 1500 according to another embodiment of the present invention. In this embodiment, the tool body 1500 includes seven attenuators 1502 located between the transmitter 1504 and the two receivers 1506. Each attenuator 1502 includes a cavity in the form of a channel 1508 that extends around the tool body 1500. In the particular example of FIGS. 15 and 16, four of the channels 1508 are disposed on the outer surface 1510 of the tool body 1500 and three channels are disposed on the inner surface 1512 of the tool body. However, in other embodiments, the channel 1508 can be disposed only on the inner surface 1512 or the outer surface 1510 of the tool body. In addition or alternatively, in other embodiments, the attenuator 1502 can include a separate member coupled to the tool body 1500, such as the embodiment of FIG.

  Each attenuator 1502 also includes a restrictor 1514 for applying stress to the particulate medium 1518 and liquid 1516 disposed within the channel 1508. In the particular example of FIGS. 15 and 16, the restrictor 1514 includes an inner sleeve 1520 and an outer sleeve 1522 for securing the liquid 1516 and granular media 1518 within the channel 1508. In the particular embodiment of FIG. 15, the ends of inner sleeve 1516 and outer sleeve 1518 include O-rings 1524 to prevent ingress of debris and liquid. The restrictor 1514 also includes a corresponding medium (such as a plug or spring / piston assembly) for applying adjustable stress to the granular medium 1516. According to certain embodiments of the invention, each attenuator 1502 is tuned to a different stress, thus attenuating different frequencies of the acoustic signal. In this way, the seven attenuators 1502 work together to attenuate a wide range of acoustic signals.

  The acoustic logging tool according to the embodiment of FIGS. 15 and 16 can advantageously provide the benefits of an additional damping mechanism. In some embodiments, the channels can form a series of periodically spaced grooves in the tool body that attenuate the acoustic signal. US Pat. No. 5,852,587 to Kostek et al. Discloses a method and apparatus for attenuating signals using a series of periodically spaced grooves in the tool body. This patent is incorporated herein by reference in its entirety.

  FIG. 17 illustrates a tool body 1700 according to another embodiment of the present invention. The tool body 1700 includes a plurality of attenuators 1702, 1703 located between the transmitter 1704 and the two receivers 1706. In the particular example of FIG. 17, a plurality of “cylindrical” attenuators 1702 as disclosed in FIG. 3 are disposed on the outer surface 1708 of the tool body 1700, such as disclosed in FIGS. A plurality of attenuators 1703 including channels extending around the body are disposed on the inner surface 1710 of the tool body. In other embodiments, both types of attenuators 1702, 1703 can be disposed on the outer surface 1708 and / or the inner surface 1710 of the tool body 1700.

  18 and 19 show a tool body 1800 according to yet another embodiment of the present invention. The tool body 1800 includes a plurality of attenuators 1802 positioned between a transmitter 1804 and two receivers 1806. In this embodiment, the attenuator 1802 includes a slot shaped cavity 1808 disposed along the outer surface 1810 of the tool body. The slot-shaped cavity 1808 has a certain width and length and is disposed around the tool body 1800. As shown in FIG. 19, each attenuator 1802 includes a restrictor 1810 that includes a particulate medium 1814 and a corresponding medium 1812 configured to apply stress to it. 18 shows the slot-shaped cavity 1808 oriented vertically (parallel to the axis of the tool body 1800), but in other embodiments, the slot-shaped cavity 1808 is axial, radial. , Tangential and / or diagonal.

  20, 21 and 22 illustrate an attenuator arrangement according to some embodiments of the present invention. The upper schematic view of each figure represents a perspective view of the tool body, and the lower schematic view represents a cross-sectional view of the tool body.

  In the example shown in FIG. 20, the tool body 2000 includes a plurality of cylindrical cavities 2002 disposed on the outer surface 2004 of the tool body. Cylindrical cavities 2002 are arranged in a plurality of azimuthally continuous rows. These rows are spaced at selected intervals along the central axis of the tool body 2000.

  In the example shown in FIG. 21, the tool body 2100 includes a plurality of slot-shaped cavities 2102 disposed on the outer surface 2104 of the tool body. The cavities 2102 are arranged in a plurality of azimuthally continuous rows spaced at selected intervals relative to the central axis of the tool body 2100.

  In the example shown in FIG. 22, the tool body 2200 includes a plurality of cylindrical cavities 2202 arranged in a plurality of azimuthally arranged rows. These rows are spaced at various intervals along the central axis of the tool body 2200. The cavities 2202 on each row have openings azimuthally arranged at even intervals. The cavity 2202 is formed to extend laterally within the tool body 2200 in a direction substantially tangent to the outer surface 2204 of the tool body.

  The present invention is not limited to the specific parameters described herein. Parameters such as the position, orientation and size of one or more cavities of the attenuator may vary. Another attenuator arrangement is disclosed in US Pat. No. 6,643,221 to Hsu et al., Which is hereby incorporated by reference in its entirety.

  FIG. 23 illustrates an acoustic tool 2300 according to one embodiment of the present invention. In one particular embodiment, this tool is used as a backing plate 2300 for a series of acoustic transducers 2302. The backing plate 2300 includes two halves configured to secure the acoustic transducer 2302 on the borehole tool and to insulate it from the acoustic signal propagating through the borehole tool.

  The backing plate 2300 includes a cylindrical tool body having an inner surface 2304 and an outer surface 2306. A series of acoustic sensors 2302 (such as a transmitter and / or receiver) are mounted on the outer surface 2306 of the backing plate 2300. The cylindrical tool body includes two half cylindrical metal frames 2308, 2310. Each half cylindrical member 2308, 2310 includes a plurality of attenuators 2312. The attenuator 2312 includes a cavity extending longitudinally from the top surface 2314 of the cylindrical tool body and between the inner surface 2304 and the outer surface 2306 of the tool body. These cavities are located circumferentially apart and can extend in various depths within the wall of the cylindrical member. A particulate medium and liquid are placed in each of these cavities to form an attenuator 2312. Next, using one of the restrictors described above, one or both ends of the cavity are sealed according to the depth of the hole. These restrictors hold the liquid and the granular medium in the cavity and apply stress to the granular medium. The cylindrical tool body 2300 can be attached to a borehole tool (not shown) after being molded into two halves.

  In an exemplary embodiment of the invention, the total volume of the attenuator within the tool body may vary. For example, in some specific embodiments, the total volume of the cavity is between 5% and 20% of the total volume of the tool body. In FIG. 2, the total volume of the tool body is defined as the volume between at least one acoustic transmitter 206 and at least one acoustic receiver 208 (such as the attenuation portion 210). Various other embodiments of the present invention are not limited to a range of 5% to 20%. In many cases, the total volume of the cavity can be increased to 50% or 60% of the total volume of the tool body. In general, the total volume of the cavity can be increased as long as the tool body maintains mechanical integrity.

式中、Ｍ_Cはカップの質量であり、Ｆ_C（ω）は、カップと加振機の間に結合された力計からの出力であり、ａ_C（ω）は、カップに結合された加速度計からの出力である。 Exemplary embodiments of the present invention also relate to methods and processes for modeling the attenuation characteristics of the attenuators and tool bodies described above. For this purpose, the effective mass M (ω) of a granular medium (such as a plurality of particles) to which stress is applied is determined. The effective mass can be measured using a shaker and a cup attached to the shaker. Fill the cup with granular media and apply a specific stress to the granular media in the cup. A shaker vibrates the cup and the granular medium at a series of frequencies. The measurement can be repeated over a plurality of different applied stresses. The effective mass of the granular medium at a specific stress can be determined according to the following equation:

Where M _C is the mass of the cup, F _C (ω) is the output from the dynamometer coupled between the cup and shaker, and a _C (ω) is coupled to the cup. Output from accelerometer.

  Further details on measuring the effective mass of granular media can be found in Valenza et al., “Dynamic Effective Mass of Granular Media and the Attenuation of Construction-Born,” . Rev. E80 (2009) 051304, and Valenza et al., “Effect of Granular Media on the Vibrational Response of a Resonant Structure”, J. Acoustic. Soc. Am. 128, 2768 (2010).

The effective mass of the granular medium includes a real part M ₁ and an imaginary part M ₂ . M ₂ is the dissipation capacity of the granular medium (M ₂ = Im [M (ω)] etc.). Dissipative capacity is a measure of the ability of a granular medium to dissipate acoustic signals. The inventors have realized that this dissipation capacity can be maximized through a specific acoustic frequency by adjusting the stress applied to the granular medium.

FIG. 24 shows a dissipation capacity vs. frequency plot 2400 according to one embodiment of the invention. The plot comprises five curves show each, the characteristics of dissipation capacity M ₂ attenuator adjusted to five different stress ranging 0.1MPa～2MPa. These five curves are designated as 2402, 2404, 2406, 2408 and 2410 in order of increasing applied stress. These five curves show that by adjusting the stress applied to the granular medium, the peak of the dissipative capacity M ₂ can be shifted over a wide frequency range (such as 5-12 kHz).

式中、ρ_sは本体の密度（鋼の密度など）であり、Ｖ_cは、本体内の１つのキャビティの体積であり、φは本体の空隙率である。 The effective mass of the granular media at a particular stress can be used to determine the damping characteristics of the granular media in the body (such as a drill collar). The following equation can be used to determine the effective density ρ _s of a body including an attenuator with a granular medium under stress.

Where ρ _s is the density of the body (such as the density of steel), V _c is the volume of one cavity in the body, and φ is the porosity of the body.

Standard acoustic borehole techniques can be used to determine the body delay value S (ω), where the density is given by Equation 2 and the body elastic constant can be measured independently. The delay value S (ω) of interest is a composite delay value. The composite delay value S (ω) includes a real part S ₁ (ω) and an imaginary part S ₂ (ω). Attenuation is related to the imaginary part of the delay and can be defined as the product of the frequency ω and the imaginary part of the delay S ₂ (ω) (eg, ω × S ₂ (ω)). This value can be converted to a decibel scale.

  FIG. 25 shows an attenuation vs. frequency plot 2500 according to one embodiment of the present invention. This plot shows the attenuation characteristics of the attenuator of FIG. In this example, the same five stresses (ranging from 0.1 MPa to 2 MPa) were applied to the granular medium in the attenuator. The five curves are designated as 2502, 2504, 2506, 2508, and 2510 in order of increasing applied stress. In contrast, curve 2512 shows the attenuation characteristics of an empty cavity (eg, free of liquid or particulate media). When the stress applied to the granular medium changes, the attenuation characteristics of the attenuator also change. For example, the least stressed granular medium 2502 attenuates about 10 decibels from a frequency of 6-7 kHz, whereas the most stressed granular medium 2510 is effective at least 100 decibels from a frequency of 12-14 kHz. Attenuate.

  The exemplary embodiments of the present invention are not limited to oil and gas applications. Various embodiments of the present invention can be used in a wide range of acoustic applications (such as telemetry, room acoustics, architectural acoustics, household appliances and audio equipment). Furthermore, while some of the embodiments disclosed above describe tools that use attenuators in conjunction with acoustic sensors, exemplary embodiments of the present invention relate to applications that do not use acoustic sensors. There are also things. For example, various embodiments of the present invention relate to damping and / or insulating materials that incorporate attenuators. In many cases, such damping materials and insulating materials do not use acoustic sensors.

  While the above description discloses various exemplary embodiments of the present invention, those of ordinary skill in the art will appreciate various implementations of some of the advantages of the present invention without departing from the true scope of the present invention. It will be clear that corrections can be made.

Claims (20)

The body,
At least one acoustic attenuator disposed along the body;
The attenuator comprises:
A cavity,
A plurality of granular particles disposed in the cavity;
A liquid disposed in the cavity;
A restrictor configured to apply stress to the granular particles in the cavity;
including,
A device characterized by that. And a plurality of acoustic attenuators, wherein at least one attenuator applies a first stress to the granular particles and at least one other attenuator applies a second stress to the granular particles. The first stress and the second stress have different values;
The apparatus according to claim 1. The restrictor is configured to apply a stress of 1 Pa to 5 MPa to the granular particles in the cavity;
The apparatus according to claim 1. The liquid has a viscosity of 2 to 1,000,000 cSt at room temperature;
The apparatus according to claim 1. The volume ratio of the liquid to the granular particles in the cavity is 0.001% to 5%.
The apparatus according to claim 1. The volume of liquid in the cavity is configured such that the liquid covers the granular particles;
The apparatus according to claim 5. The granular particles have a particle size of 1 to 500 microns,
The apparatus according to claim 1. At least one acoustic transmitter disposed on the body;
At least one acoustic receiver disposed on the body;
The at least one acoustic attenuator is disposed between the at least one acoustic receiver and the at least one acoustic transmitter.
The apparatus according to claim 1. A plurality of attenuators disposed between the at least one acoustic transmitter and the at least one acoustic receiver; and the plurality of attenuators between the at least one acoustic transmitter and the at least one acoustic receiver. The attenuator has a volume of 5% to 20% of the volume of the tool body;
The apparatus according to claim 8. The device is a drilling simultaneous logging tool and the body is a drill collar;
The apparatus according to claim 1. A logging tool to conduct acoustic surveys of the underground layer that the borehole crosses,
A tool body extending in the vertical direction;
At least one acoustic transmitter disposed at a first longitudinal position on the body;
At least one acoustic receiver disposed at a second longitudinal position on the body;
At least one acoustic attenuator disposed between the at least one acoustic transmitter and the at least one acoustic receiver;
The attenuator comprises:
A cavity in the tool body;
A plurality of granular particles disposed in the cavity;
A liquid disposed within the cavity and configured to cover the granular particles within the cavity;
A restrictor configured to apply stress to the granular particles in the cavity;
including,
Logging tool characterized by that. The restrictor includes a spring configured to apply stress to the granular particles in the cavity;
The logging tool according to claim 11. A plurality of attenuators disposed between the at least one acoustic transmitter and the at least one acoustic receiver, wherein the at least one attenuator applies a first stress to the granular particles; One other attenuator applies a second stress to the granular particles, the first stress and the second stress having different values;
The logging tool according to claim 11. The liquid has a viscosity of 2 to 1,000,000 cSt at the borehole temperature;
The logging tool according to claim 11. The restrictor is configured to apply a stress of 1 Pa to 5 MPa to the granular particles in the cavity;
The logging tool according to claim 11. The granular particles have a particle size of 1 to 500 microns,
The logging tool according to claim 11. And a plurality of attenuators disposed between the at least one acoustic transmitter and the at least one acoustic receiver, the plurality of attenuators between the at least one acoustic transmitter and the at least one acoustic receiver. The attenuator has a volume of 5% to 20% of the volume of the tool body;
The logging tool according to claim 11. The device is a drilling simultaneous logging tool and the body is a drill collar;
The logging tool according to claim 11. A method of attenuating an acoustic signal propagating through a main body,
Disposing a plurality of granular particles in a cavity disposed along the body;
Applying stress to the granular particles in the cavity;
A method comprising the steps of: The stress applied to the granular particles is adjusted to attenuate a specific frequency of the acoustic signal;
20. A method according to claim 19, wherein:

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