JP6411131B2 - Vibration sensor and vibration sensing system - Google Patents

Description

  The present invention relates to a vibration sensor and a vibration sensing system, for example, a vibration sensor and a vibration sensing system using a superconducting quantum interferometer (SQUID) used for a seismometer and a vibration sensor for elastic wave inspection.

  Seismometers and vibration sensors for elastic wave inspection are used in exploration using artificial earthquakes to obtain underground information such as resource exploration. Conventionally, geophones (for example, see Patent Document 1) and MEMS vibration sensors (for example, see Patent Document 2) are used as vibration sensors for elastic wave diagnosis, and useful underground information can be acquired by elastic wave diagnosis. It is like that.

  In recent years, underground information collection by elastic wave diagnosis has become increasingly important in the development of shale gas and new resources such as increased oil production (EOR), and in particular, low frequency elastic wave diagnosis has become important. Yes.

JP 05-248175 A JP 2011-209200 A

  However, the geophone has a problem that it is not good at low-frequency detection because the coil is fixed by a spring and an induced electromotive force is generated by a mutual movement with a permanent magnet that moves together with the casing, thereby capturing vibration. The same applies to MEMS sensors. Furthermore, the development of underground exploration technology using artificially generated magnetic signals is progressing, and a fusion of various sensing technologies is required.

  Accordingly, it is an object of the present invention to detect low frequency vibration with high accuracy in a vibration sensor and a vibration sensing system.

From one aspect to be disclosed, a fixed member and a superconducting quantum interferometer mechanically fixed to the fixed member are included, and vibration from a vibration source is linked to the superconducting quantum interferometer generated by the vibration. A vibration sensor is provided that is secondarily detected as a change in an external magnetic field.

  From another viewpoint to be disclosed, the above-described vibration sensor, a magnetometer installed remotely from the vibration sensor with respect to the vibration source to detect a change in geomagnetism not caused by the vibration, and the vibration sensor There is provided a vibration sensing system comprising extraction means for subtracting the output of the magnetometer from the output and extracting only a change in geomagnetism due to vibration as a difference.

  From another viewpoint to be disclosed, the apparatus includes the above-described vibration sensor, a magnetometer that is installed in the vicinity of the vibration sensor to detect magnetism other than geomagnetism, and a vibration isolation mechanism that suppresses vibration of the magnetometer. A vibration sensing system characterized by the above is provided.

From another viewpoint the disclosed installation and fixing member, the fixing member mechanically fixed superconducting quantum interferometer and the magnetized steel pipes a housing containing the vibration sensor is embedded in the ground with And the vibration sensing system characterized by using the magnetic field which the said steel pipe emits as a magnetic field generation source is provided.

According to another aspect of the disclosure, a shield having a vibration signal having a fixed member and a superconducting quantum interferometer mechanically fixed to the fixed member and having a magnetic signal cutoff frequency of 1 kHz or more is provided on the exterior. There is provided a vibration sensing system characterized in that the provided casing is installed in a steel pipe buried in the ground.

  According to the disclosed vibration sensor and sensing system, it is possible to detect with high accuracy against low-frequency vibration.

It is explanatory drawing of the vibration sensor of embodiment of this invention. It is explanatory drawing of the detection principle of the vibration sensor of embodiment of this invention. It is explanatory drawing of the vibration sensor of Example 1 of this invention. It is explanatory drawing of the main-body part of the vibration sensor of Example 1 of this invention. It is explanatory drawing of the installation state of the vibration sensor of Example 1 of this invention. It is explanatory drawing of the main-body part of the vibration sensor of Example 2 of this invention. It is a notional block diagram of the vibration sensing system of Example 3 of this invention. It is a notional block diagram of the vibration sensing system of Example 4 of this invention. It is a notional block diagram of the vibration sensing system of Example 5 of this invention. It is a notional block diagram of the vibration sensing system of Example 6 of this invention.

Here, with reference to FIG.1 and FIG.2, the vibration sensor and vibration sensing system of embodiment of this invention are demonstrated. FIG. 1 is an explanatory view of a vibration sensor according to an embodiment of the present invention. A container 2 containing a superconducting quantum interferometer 1 is mechanically fixed to a fixing member 3 to form a main body of the vibration sensor. As the superconducting quantum interferometer 1, any superconducting quantum interferometer may be used as long as it is composed of a high-temperature superconductor mainly made of a rare earth material such as Y, Ba, or Cu and operates at a liquid nitrogen temperature of 77K. Further, as the SQUID element structure used in the superconducting quantum interferometer 1, various high-temperature superconducting junctions such as a ramp edge type Josephson element, a step edge type Josephson element, and a bicrystal type can be used.

Further, the superconducting quantum interferometer 1, x direction xyz orthogonal coordinate system with respect to the fixed member 3, it is desirable to mechanically fixed in three directions of the y and z directions. Thus, the direction of the vibration source can be specified by each superconducting quantum interferometer 1 mechanically fixed in the three directions of the x direction, the y direction, and the z direction. Further, by combining the outputs of the respective superconducting quantum interferometers 1 and analyzing the vibration, it is possible to detect the vibration with high accuracy regardless of the position of the vibration source.

In this case, the fixed shaft diameter and length of the fixing member 3, may be the possible pendulum motion size relative to the fixed shaft fixed point 4, whereby the change of the magnetic field interlinking increases, solid The sensitivity to the frequency around the individual vibration of the member 3 can be further increased. For example, the diameter of the fixed shaft is 25 mm or less and the length is 100 mm or more.

FIG. 2 is an explanatory diagram of the detection principle of the vibration sensor according to the embodiment of the present invention. 2 (a) is a diagram showing the initial state, the superconducting quantum interferometer 1 are interlinked with the magnetic field 5 at a predetermined angle. As shown in FIG. 2B, when the superconducting quantum interferometer 1 vibrates due to vibration from the vibration source, the relative positions of the superconducting quantum interferometer 1 and the magnetic field 5 change, and accordingly, the superconducting quantum interferometer 1 is chained to the superconducting quantum interferometer 1. magnetic field 5 to exchange changes.

  As shown in FIG. 2C, vibration can be detected secondarily by measuring the change in the magnetic field with the superconducting quantum interferometer 1. In this case, since the superconducting quantum interferometer 1 has a highly sensitive performance from DC to 100 kHz, it can detect low-frequency vibrations with high sensitivity.

The magnetic field 5 to be measured may be geomagnetism or an artificial magnetic field.

  In order to sense vibration using such a vibration sensor, it is desirable to install a magnetometer remote from the vibration sensor with respect to the vibration source in order to measure a change in geomagnetism not caused by vibration. In this way, by providing a separate magnetometer and subtracting the output of the magnetometer from the output of the vibration sensor and extracting only the change in geomagnetism due to vibration as a difference, highly accurate detection that is not affected by natural fluctuations in geomagnetism is possible. It becomes possible.

  In order to eliminate the influence of artificial magnetism, a reference magnetometer may be installed in the vicinity of the vibration sensor. In this case, a vibration isolation mechanism that can remove the vibration of the frequency that the magnetometer wants to detect. It is desirable to install it via Note that it is desirable to use a magnetometer having a sensitivity of 1 nT or more, such as a fluxgate magnetometer, an optical pumping magnetometer, or a superconducting quantum interference device, as a magnetometer, in order to maintain measurement accuracy even in a remote arrangement.

Or installed on the fixed member 3 to mechanically fixed superconducting quantum interferometer 1 magnetized in steel pipes the housing containing the vibration sensor is embedded in the ground with, utilizes a magnetic field generated by the steel pipe as a magnetic source You may do it.

Alternatively, in a steel pipe in which a casing having a shield with a magnetic signal cutoff frequency of 1 kHz or more that contains a vibration sensor having a superconducting quantum interferometer 1 mechanically fixed to a fixing member 3 is embedded in the ground. May be installed. In this case, since the magnetic signal transmitted artificially from the transmitting coil can be received, it can be used as a sensor for both electromagnetic exploration and seismic exploration.

  In the embodiment of the present invention, since the vibration is detected as a change in the magnetic field using the superconducting quantum interferometer 1, low-frequency elastic wave exploration from DC to 100 kHz necessary for underground resource exploration becomes possible. . In addition, the electromagnetic exploration method can improve the efficiency and accuracy of exploration by utilizing the same sensor system, and can greatly advance the technology of resource exploration and underground monitoring.

Next, a vibration sensor and a vibration sensing system according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 3 is an explanatory diagram of the vibration sensor according to the first embodiment of the present invention, and is shown here as a partially cutaway perspective view. As the vibration sensor main body, a container 12 in which the SQUID is accommodated in the fixed column 13 is mechanically fixed in the xyz 3-axis direction.

  The housing for storing the vibration sensor main body includes an envelope made of an aluminum frame 21 and a glass dewar 23 accommodated in the envelope via a vibration-proof foam gel 22. The glass dewar 23 is sealed and fixed by a shield spring spiral 25 through an aluminum-coated melamine foam 24. The fixed column 13 is attached to a lid member integrated with the shield spring spiral 25 and immersed in liquid nitrogen 26 injected into the glass dewar 23.

  FIG. 4 is an explanatory diagram of the vibration sensor main body according to the first embodiment of the present invention. The container 12 containing the SQUID 11 is fixed to the fixed column 13 in the xyz 3-axis direction to form the vibration sensor main body. Here, the SQUID 11 is a SQUID using a lamp edge type Josephson element using yttrium and lanthanoid high temperature superconductivity.

  FIG. 5 is an explanatory diagram of an installation state of the vibration sensor according to the first embodiment of the present invention. Here, the geomagnetism 40 is used as a magnetic field, and the vibration sensor 10 is controlled by the control circuit 30 to detect vibration. The vibration sensor 10 is fixed to the vibration surface. The vibration surface is, for example, the ground when detecting the vibration of the ground. By using the geomagnetism 40 which is not mechanically connected, it is possible to reduce mechanical natural vibration to the limit.

  In this example, when the SQUID 11 is fixed, the SQUID 11 is firmly fixed so that the fixed axis of the SQUID 11 does not resonate around the fixed point 14 in the frequency band of vibration to be measured. For example, as shown in FIG. 4, a cylindrical fixed column 13 of 30 mmφ or more is used for the fixed shaft of the SQUID 11. Here, the diameter d is 30 mmφ, and the length h is 80 mm.

  Thus, in Example 1 of this invention, since the container 12 which accommodated SQUID11 is being fixed to the xyz3 axial direction, a vibration direction can be specified. The vibration intensity is obtained by combining the outputs of three SQUIDs 11 fixed in the xyz 3-axis direction.

Next, the vibration sensor according to the second embodiment of the present invention will be described with reference to FIG. 6. Since the overall structure is the same as that of the first embodiment shown in FIG. 3, only the vibration sensor main body will be described. To do. FIG. 6 is an explanatory diagram of the vibration sensor main body according to the second embodiment of the present invention. Here, the container 12 containing the SQUID 11 is mechanically fixed to the fixed column 15 in the xyz 3-axis direction, and the main body of the vibration sensor is mounted. Form.

In the second embodiment, the SQUID 11 is fixed with the flexibility to cause the shaft swing. By providing flexibility in this manner, the pendulum motion is performed around the fixed point 16 of the shaft while being restricted by the natural vibration. Therefore vibration sensor will be inclined larger relative geomagnetism, since the change of the magnetic field interlinking increases, can be detected with high sensitivity to frequencies around the natural frequency.

  In order to detect a change in a low-frequency magnetic field with high sensitivity, a cylindrical fixed column 15 having a length of 25 mmφ or less and a length of 100 mm or more is used as a fixed shaft. Here, the diameter d is 20 mmφ and the length h is 120 mm.

Next, with reference to FIG. 7 , the vibration sensing system of Example 3 of this invention is demonstrated. FIG. 7 is a conceptual configuration diagram of the vibration sensing system according to the third embodiment of the present invention. Here, an example of elastic wave diagnosis for artificially generating vibration will be described. First, the vibration sensors 51 to 53 are inserted into the boring casing 54 serving as the inner wall of the well, and the vibration sensors 51 to 53 are controlled by the control circuit 55. Here, a reference flux gate 56 serving as a reference is separately provided in order to distinguish a change in the geomagnetism itself that fluctuates daily from a relative change in the geomagnetism due to vibration.

  In this case, as the vibration sensors 51 to 53, the vibration sensor of the first embodiment may be used, or a vibration sensor in which only one SQUID is housed in a housing may be used. In this case, for example, the SQUID may be fixed in the x direction in the vibration sensor 51, the SQUID may be fixed in the y direction in the vibration sensor 52, and the SQUID may be fixed in the z direction in the vibration sensor 53.

  As described above, the change in geomagnetism changes on a daily basis by about 100 nT, and there is almost no difference in the magnitude of the geomagnetism within a range of about 100 km. Therefore, in the case of elastic wave diagnosis for artificially generating vibration, a reference flux gate 56 having a sensitivity of 1 nT or more is installed at a position several kilometers away from the vibration sensors 51 to 53 for vibration detection, for example, 3 km. To do. A magnetometer such as an optical pumping magnetometer or a superconducting quantum interference device may be used instead of the flux gate.

When the seismic wave 58 is generated by the artificial seismic source 57, the vibration sensors 51 to 53 housed in the boring casing 54 and fixed by the centizer vibrate together with the crust, so that the relative position of each SQUID and the geomagnetism 59 changes. Accordingly, the magnetic field linked to the SQUID changes, so that vibration can be detected by detecting the change in the magnetic field.

  At this time, the vibration can be accurately detected by subtracting the daily change of the geomagnetism 59 detected by the reference flux gate 56 from the detection output.

Next, with reference to FIG. 8 , the vibration sensing system of Example 4 of this invention is demonstrated. FIG. 8 is a conceptual configuration diagram of the vibration sensing system according to the fourth embodiment of the present invention. The basic configuration is the same as that of the third embodiment, but here, a reference SQUID is provided in the vicinity of the vibration sensor. Yes.

  Here, it will be described as an example of elastic wave diagnosis that artificially generates vibration. First, the vibration sensors 51 to 53 are inserted into the boring casing 54 serving as the inner wall of the well, and the vibration sensors 51 to 53 are controlled by the control circuit 55. Here, in order to remove an artificial magnetic change such as a commercial power source, a reference SQUID 60 serving as a reference is installed in the vicinity of the installation positions of the vibration sensors 51 to 53. In this case, it is desirable to install the reference SQUID 60 using a vibration isolation mechanism 61 that can remove the vibration in the frequency region that the reference SQUID 60 wants to detect, and to remove magnetic field changes other than vibration. Also in this case, a reference flux gate 56 serving as a reference may be provided in order to distinguish a change in the geomagnetism itself that fluctuates daily from a relative change in the geomagnetism due to vibration.

Next, with reference to FIG. 9 , the vibration sensing system of Example 5 of this invention is demonstrated. FIG. 9 is a conceptual configuration diagram of the vibration sensing system according to the fifth embodiment of the present invention. The basic configuration is the same as that of the third embodiment described above, but here, a magnetic field generated from a magnetized steel pipe instead of geomagnetism. Is used. In order to magnetize the steel pipe 62, it may be artificially magnetized or natural magnetization by geomagnetism may be used.

  Here, it will be described as an example of elastic wave diagnosis that artificially generates vibration. First, a magnetized steel pipe 62 is used as a boring casing serving as the inner wall of the well. The vibration sensors 51 to 53 are inserted into the steel pipe 62, and the vibration sensors 51 to 53 are controlled by the control circuit 55. At this time, while the vibration sensors 51 to 53 are held in the center of the steel pipe 62 by a centralizer, play is provided in the steel pipe 62 and the vibration sensors 51 to 53 so that vibration of the minute steel pipe 62 can be detected.

The artificial source 57 and to generate a seismic wave 58, a vibration by the steel pipe 62 is vibrated, for detecting a magnetic signal generated from the vibration sensor 51 to 53 and linkage to the steel pipe 62 with the vibration of the steel pipe 62 in SQUID Can be detected. In addition, since the steel pipe 62 serves as a magnetic shield, the influence of geomagnetism on the vibration sensors 51 to 53 can be shielded.

Next, with reference to FIG. 10 , the vibration sensing system of Example 6 of this invention is demonstrated. FIG. 10 is a conceptual configuration diagram of the vibration sensing system according to the sixth embodiment of the present invention. The basic configuration is the same as that of the third embodiment, but here, a magnetic signal is artificially generated. .

  Here, it will be described as an example of elastic wave diagnosis that artificially generates vibration. First, the vibration sensors 51 to 53 are inserted into the boring casing 54 serving as the inner wall of the well, and the vibration sensors 51 to 53 are controlled by the control circuit 55. Here again, a reference flux gate 56 serving as a reference is separately provided in order to distinguish a change in the geomagnetism itself that fluctuates daily from a relative change in the geomagnetism due to vibration. In addition, as a housing | casing of the vibration sensors 51-53, it shields using RF shielding material whose cutoff frequency is 1 kHz or more. In addition, an oscillation coil 64 is inserted into a boring casing 63 serving as an inner wall of another well, and the oscillation coil 64 is controlled by an oscillation circuit 65 to generate a magnetic signal 66.

The vibration detection in the sixth embodiment is exactly the same as in the third embodiment. When the seismic wave 58 is generated by the artificial seismic source 57, the vibration sensors 51 to 53 vibrate together with the crust, so that the relative position of each SQUID and the geomagnetism 59 is Change. Accordingly, the magnetic field interlinking with the SQUID changes, so that vibration can be detected by detecting a change in a low frequency magnetic field excluding a high frequency component of 1 kHz or more.

In addition to vibration detection, a magnetic signal 66 is generated by the oscillation coil 64 inserted into the boring casing 63, and the magnetic signal 66 is detected by the vibration sensors 51 to 53.
A sensor function as an electromagnetic logging for analyzing the resistivity structure can be provided.

In the vibration sensing system of Example 6 of the present invention, it is possible to perform elastic wave logging and electromagnetic logging using the same sensor. As a result, it is possible to improve the utilization efficiency and work efficiency of the facility, and to perform a more detailed analysis of the underground structure by performing a plurality of logs simultaneously.

Here, the following supplementary notes are attached to the embodiments of the present invention including Examples 1 to 6.
(Supplementary Note 1) A fixed member and a superconducting quantum interferometer that is mechanically fixed to the fixed member. The vibration from the vibration source is an external magnetic field that links the superconducting quantum interferometer generated by the vibration. A vibration sensor characterized by secondary detection as a change.
(Supplementary note 2) The vibration sensor according to supplementary note 1, wherein the superconducting quantum interferometer is mechanically fixed to a fixed member in three directions of x, y, and z directions of an xyz orthogonal coordinate system. .
(Supplementary note 3) The vibration sensor according to supplementary note 2, wherein the vibration analysis is performed by combining the outputs of the respective superconducting quantum interferometers mechanically fixed in the three directions of the x direction, the y direction, and the z direction.
(Additional remark 4) The vibration sensor of Additional remark 2 or Additional remark 3 characterized by making the fixed shaft diameter and length of the said fixing member into the size in which the said fixed shaft can carry out a pendulum movement with respect to a fixed point.
(Supplementary note 5) The vibration sensor according to any one of supplementary notes 1 to 4, wherein the change in the magnetic field is a change in geomagnetism caused by the superconducting quantum interferometer vibrating in the geomagnetism.
(Appendix 6) The vibration sensor according to any one of appendices 1 to 5, and a magnetometer that is installed remotely from the vibration sensor with respect to the vibration source and detects a change in geomagnetism not caused by the vibration. And an extraction means for subtracting the output of the magnetometer from the output of the vibration sensor and extracting only the change in geomagnetism due to vibration as a difference.
(Supplementary note 7) The vibration sensor according to any one of supplementary notes 1 to 5, a magnetometer that is installed in the vicinity of the vibration sensor and detects magnetism other than geomagnetism, and vibration isolation that suppresses vibration of the magnetometer A vibration sensing system characterized by having a mechanism.
(Supplementary note 8) A magnetic field generated by a steel pipe installed in a magnetized steel pipe embedded in the ground with a container containing a vibration sensor having a fixing member and a superconducting quantum interferometer mechanically fixed to the fixing member. Is a vibration sensing system characterized in that it is used as a magnetic field source.
(Additional remark 9) The housing | casing which equip | installed the exterior with the shield which the cutoff frequency of the magnetic signal which accommodated the vibration sensor which has a fixed member and the superconducting quantum interferometer mechanically fixed to the said fixed member becomes 1 kHz or more A vibration sensing system that is installed in a steel pipe buried in

DESCRIPTION OF SYMBOLS 1 Superconducting quantum interferometer 2 Container 3 Fixed member 4 Fixed point 5 Magnetic field 10 Vibration sensor 11 SQUID
12 Containers 13 and 15 Fixed struts 14 and 16 Fixed point 21 Aluminum frame 22 Antivibration foam gel 23 Glass dewar 24 Aluminum coated melamine foam 25 Shield spring spiral 26 Liquid nitrogen 30 Controller 40 Geomagnetism
51 to 53 Vibration sensors 54 and 63 Boring casing 55 Control circuit 56 Reference flux gate 57 Artificial source 58 Seismic wave 59 Geomagnetism 60 Reference SQUID
61 Vibration isolation mechanism 62 Steel pipe 64 Oscillation coil 65 Oscillation circuit 66 Magnetic signal

Claims (6)

A fixing member;
A superconducting quantum interferometer mechanically fixed to the fixing member;
A vibration sensor, wherein vibration from a vibration source is secondarily detected as a change in an external magnetic field interlinked with the superconducting quantum interferometer generated by the vibration. 2. The vibration sensor according to claim 1, wherein the superconducting quantum interferometer is mechanically fixed in three directions of an xyz orthogonal coordinate system in an x direction, a y direction, and a z direction with respect to a fixed member. The vibration sensor according to claim 1 or 2,
A magnetometer installed remotely from the vibration sensor with respect to the vibration source and detecting a change in geomagnetism not caused by the vibration;
A vibration sensing system comprising: extraction means for subtracting the output of the magnetometer from the output of the vibration sensor and extracting only a change in geomagnetism due to vibration as a difference. The vibration sensor according to claim 1 or 2,
A magnetometer installed near the vibration sensor to detect magnetism other than geomagnetism;
A vibration sensing system comprising a vibration isolation mechanism that suppresses vibration of the magnetometer. A fixing member, installed on the fixed member to mechanically fixed superconducting quantum interferometer and magnetized in steel containers housing the vibration sensor is embedded in the ground with,
A vibration sensing system using a magnetic field generated by the steel pipe as a magnetic field generation source. A steel pipe in which a casing having a shield with a magnetic signal cut-off frequency of 1 kHz or more is embedded in the ground, housing a vibration sensor having a fixed member and a superconducting quantum interferometer mechanically fixed to the fixed member Vibration sensing system characterized by being installed inside.

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