A piezoelectric seismic geophone

Abstract

A piezoelectric geophone core and a piezoelectric geophone, comprising a cantilever beam base made of elastic material and a first-end piezoelectric sheet and a second-end voltage sheet respectively located at both ends of the cantilever beam base, one end of the cantilever beam base is used to rigidly connect to the inner wall of the shell of the piezoelectric geophone, the lower surface of the first-end piezoelectric sheet is fixed to one end of the cantilever beam base, the lower surface of the second-end piezoelectric sheet is fixed to the other end of the cantilever beam base, and the first-end piezoelectric sheet and the second-end piezoelectric sheet are electrically connected to an output wire to output the respectively sensed electrical signals in voltage series or current parallel connection. The geophone core structure provided by the present invention has the advantages of high sensitivity, strong anti-interference ability, wide dynamic range, lightness and durability, and is more reliable and widely used in the fields of onshore seismic exploration, downhole slot wave seismic exploration, etc.

Description

Technical Field

[0001] The present invention relates to the field of seismic exploration, and more particularly to a piezoelectric seismic geophone core and a piezoelectric seismic geophone. Background Art

[0002] A seismic detector is a special sensor used in geological exploration and engineering measurement that converts the direct wave of an artificially excited earthquake source or the reflected wave of each stratum into an electrical signal and then inputs it into a seismic instrument. According to the working principle, it can be divided into magnetoelectric, eddy current, and piezoelectric detectors. According to the application environment, it can be divided into land exploration seismic detectors, underwater seismic detectors used in rivers, lakes and seas, and well seismic detectors used in seismic logging. According to the energy conversion mechanism, it can be divided into velocity type geophones and acceleration type geophones. From the exploration method, it can be divided into longitudinal wave geophones, also known as vertical geophones, and transverse wave geophones, also known as horizontal geophones, and three-component geophones. In addition, seismic detectors can also be divided into active geophones and passive geophones. Traditional mechanical moving coil and eddy current geophones are both passive geophones, while piezoelectric geophones are active geophones.

[0003] At present, the most widely used in China is the traditional analog seismic detector. This seismic wave sensor outputs an analog signal. Conventional or super-speed detectors are mainly used on land. This type of detector is basically a magnetoelectric detector or an eddy current detector. Their internal structure is composed of permanent magnets and coils. They basically apply the principle of electromagnetic induction and achieve the purpose of seismic exploration through the interaction between coils and permanent magnets. These detectors have a highly elastic structure such as a coil inside. The components are prone to large relative motion and deformation, so the waveform is prone to deformation, which in turn causes signal distortion. In addition, since the performance of the permanent magnet will change and the magnetism will fade over time, its life is not long and it is easily affected by the environment. The stability is low, so it cannot meet the requirements of high-precision and high-resolution seismic exploration. As the first step of the seismic signal acquisition process, this detector device cannot obtain a good original seismic signal, which directly affects the quality of the collected seismic data, limits the ability to obtain complex geological structures using seismic exploration methods, and becomes one of the main bottlenecks restricting the development of petroleum geophysical exploration technology. With the improvement of high-precision oil and gas exploration technology and the increase in the complexity of oil and gas exploration, seismic detectors are developing in the direction of low distortion, high sensitivity, wide bandwidth, large dynamic range, wide frequency response, low equivalent input noise, small size, light weight and strong anti-electromagnetic interference ability, meeting the requirements of high-resolution acquisition, which is the current development trend of seismic detectors. Various new types of geophones using different new technologies and new materials have begun to appear.

[0004] Piezoelectric acceleration geophone is a new type of geophone that has appeared in recent years. It has a simple internal structure, no magnetic steel and coil, so it has high rigidity, small deformation, small waveform distortion, stable performance, high resolution, and is a high-sensitivity high-fidelity geophone. Yuan Baoding et al. developed an inertial piezoelectric land and water universal geophone in 1993 (Chinese patent 93232320.0); Duke et al. developed a land-based piezoelectric ceramic geophone (Chinese patent 00226749.7); Liu Zhaoqi developed a YD2000 land-based piezoelectric geophone (Chinese patent 200420042025.X), all of which use traditional lead zirconium and zirconium titanate [PbZrO3-PbTiO3] (PZT for short). The piezoelectric geophone has a high natural frequency and good high-frequency response, but due to the low piezoelectric constant and high impedance of its traditional piezoelectric elements, it has a small dynamic range, high impedance, and low low-frequency response. The study shows that the new relaxor ferroelectric crystal lead magnesium niobate-lead titanate [xPb(Mg 1 / 3 Nb 2 / 3 The main piezoelectric performance indicators of PMNT are much higher than those of the currently commonly used PZT piezoelectric ceramics. Relaxor ferroelectric single crystal materials have a high piezoelectric constant g 33 d 33 , electromechanical coupling coefficient k 33 , dielectric constant ε 33 T Its comprehensive performance is superior to that of PZT ceramics due to its high thermal conductivity and low electrical loss. Using relaxor ferroelectric single crystal materials as the sensing element of piezoelectric seismic geophones and designing a matching geophone core structure to give full play to the performance advantages of single crystal materials will hopefully greatly improve their sensitivity. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a piezoelectric seismic detector core and a piezoelectric seismic detector in order to overcome the shortcomings of the existing piezoelectric seismic detectors, such as insufficient sensitivity and poor low-frequency response. A cantilever beam structured detector core is used to increase the sensitivity of the detector in a limited space and improve its low-frequency response performance.

[0006] According to one aspect of the present invention, in order to solve its technical problem, the present invention provides a piezoelectric seismic detector core, including a cantilever beam base made of elastic material and a first-end piezoelectric plate and a second-end voltage plate respectively located at both ends of the cantilever beam base, one end of the cantilever beam base is used to rigidly connect to the inner wall of the outer shell of the piezoelectric seismic detector, the lower surface of the first-end piezoelectric plate is fixed to one end of the cantilever beam base, and the lower surface of the second-end piezoelectric plate is fixed to the other end of the cantilever beam base, the first-end piezoelectric plate and the second-end piezoelectric plate are electrically connected to the output wire to output the respectively sensed electrical signals in voltage series or current parallel.

[0007] In the piezoelectric geophone core of the present invention, the cantilever beam base is made of beryllium bronze or phosphor bronze.

[0008] In the piezoelectric seismic geophone core of the present invention, both the first-end piezoelectric sheet and the second-end piezoelectric sheet are single-layer structures and are made of piezoelectric single crystal PMN-PT; or,

[0009] The first-end piezoelectric sheet and / or the second-end piezoelectric sheet respectively have multiple piezoelectric single crystals. The piezoelectric single crystals contained in the first-end piezoelectric sheet and the second-end piezoelectric sheet are respectively arranged and connected according to the crystal polarization direction, and each piezoelectric single crystal is made of piezoelectric single crystal PMN-PT.

[0010] In the piezoelectric seismic geophone core of the present invention, the crystal orientation of the piezoelectric sheet at the first end is <110> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the piezoelectric piece at the first end is d 31 Transduction mode; the crystal orientation of the second end piezoelectric piece is <001> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the second end piezoelectric piece is d 33 Transducer mode.

[0011] In the piezoelectric seismic detector core of the present invention, the upper surface and lower surface of each piezoelectric plate in the first end piezoelectric plate and the second end piezoelectric plate are respectively provided with an upper surface electrode and a lower surface electrode, and output wires are respectively led out from each upper surface electrode and each lower surface electrode; the electrode material of the upper and lower surface electrodes of the first end piezoelectric plate and the second end piezoelectric plate is silver or gold; the output wires led out from the upper and lower surface electrodes of the first end piezoelectric plate and the second end piezoelectric plate are copper wires.

[0012] In the piezoelectric geophone core of the present invention, the lower surfaces of the first end piezoelectric sheet and the second end piezoelectric sheet are both fixed to the cantilever beam base by bonding.

[0013] In the core of the piezoelectric geophone of the present invention, a mass block is fixed to the region where one end of the cantilever beam base is located, and the other end is used for rigid connection with the inner wall of the shell of the piezoelectric geophone.

[0014] The mass block is located on the upper surface of the first end piezoelectric sheet or the second end piezoelectric sheet, the lower surface of the mass block is the same in shape and size as the upper surface of the first end piezoelectric sheet or the second end piezoelectric sheet connected thereto, and the two are connected to completely cover each other.

[0015] According to another aspect of the present invention, in order to solve its technical problem, the present invention also provides a piezoelectric seismic detector, including a piezoelectric seismic detector core as described in any of the above items, wherein one end of the cantilever beam base of the piezoelectric seismic detector core is rigidly connected to the inner wall of the outer shell of the piezoelectric seismic detector.

[0016] In the piezoelectric geophone of the present invention, one end of the cantilever beam base of the core of the piezoelectric geophone is rigidly connected to the inner wall of the outer shell of the piezoelectric geophone through a base, and one end of the cantilever beam base of the core of the piezoelectric geophone is rigidly connected to the base, and the base is rigidly connected to the inner wall of the outer shell of the piezoelectric geophone.

[0017] The piezoelectric seismic detector realized based on the piezoelectric seismic detector core of the present invention has the advantages of high sensitivity, strong anti-interference ability, wide dynamic range, lightness and durability, and is more reliably and widely used in the fields of onshore seismic exploration, downhole slot wave seismic exploration, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0019] Figure 1 A schematic structural diagram of a preferred embodiment of a piezoelectric seismic geophone core provided by the present invention;

[0020] Figure 2 for Figure 1 The sensitivity-frequency relationship curve of the new PMN-PT piezoelectric material compared with PZT material under the cantilever beam structure;

[0021] Figure 3 A schematic structural diagram of another embodiment of the piezoelectric seismic detector core provided by the present invention. DETAILED DESCRIPTION

[0022] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0023] like Figure 1As shown, it is a structural schematic diagram of a preferred embodiment of the piezoelectric geophone core of the present invention. The piezoelectric geophone core includes a cantilever beam substrate 2, a piezoelectric sheet 3 (first end voltage sheet), a piezoelectric sheet 7 (second end voltage sheet) and a mass block 4. These components form a dual piezoelectric sheet cantilever beam structure, so that the piezoelectric sheets 3 and 7 vibrate with the vibration of the external environment. The cantilever beam substrate 2 uses an elastic element, which is more sensitive to vibration and can increase the sensitivity of the piezoelectric geophone core. It can be preferably made of beryllium bronze or phosphor bronze. The lower surface of the piezoelectric sheet 7 is attached to the end of the cantilever beam substrate 2, the A end. The piezoelectric geophone has a base 1. The A end of the cantilever beam substrate 2 is rigidly connected to the base 1 and is arranged horizontally. The base 1 is rigidly connected to the shell of the geophone; the lower surface of the piezoelectric sheet 3 is attached to the other end of the cantilever beam substrate 2, the B end. The upper surface of the piezoelectric sheet 3 is fixed with a mass block 4 made of steel or tungsten alloy. The mass block 4 can cause the piezoelectric sheet 3 to produce a greater strain. For different piezoelectric seismic geophones, the sensitivity and resonant frequency of the geophone are designed by setting the mass block 4 to different masses; the bottom surface of the mass block 4 is the same size and shape as the upper surface of the piezoelectric sheet 3, and the two are connected without any stagger; the piezoelectric sheet 3 and the piezoelectric sheet 7 convert the force into an electrical signal, and the upper surface electrode 5 and the lower surface electrode 6 are respectively mounted on the upper surface and the lower surface of the piezoelectric sheet 3, and the upper surface electrode 8 and the lower surface electrode 9 are respectively mounted on the upper surface and the lower surface of the piezoelectric sheet 7, and output wires are respectively led out from each upper surface electrode and the lower surface electrode, wherein a group of outputs is formed on the piezoelectric sheet 3, and a group of outputs is formed on the piezoelectric sheet 7, and the two groups of outputs perform parallel output of current or series output of voltage to form a seismic electrical signal, and the two groups of signals are superimposed after the parallel output of current or the series output of voltage, and the signal is larger. In Figure 1, F(t) indicates that when the ground vibrates, the force on the a end of the geophone is transmitted to the b end, and the force on the b end is F B (t), where F B (t) = KF(t), where K is the transfer coefficient and is a constant.

[0024] The electrode materials of the upper surface electrodes 5 and 8, the lower surface electrodes 6 and 9 can be silver, copper or gold. The piezoelectric sheets 3 and 7 are square single-layer structures with a size of 10 mm*10 mm*1 mm, and are made of piezoelectric single crystal (PMN-PT); the crystal orientation of the piezoelectric sheet 7 is <110> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the piezoelectric piece a is d 31 Transducer mode; the crystal orientation of the piezoelectric piece 3 is <001> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the piezoelectric piece b is d 33 Transducer mode.

[0025] Figure 2The cantilever beam structure shows that, after calculation, the sensitivity of the model with PMN-PT as the piezoelectric material is higher than that of the model with PZT-5A as the piezoelectric material in the frequency range of 0-1000Hz. The sensitivity of the PMN-PT dual piezoelectric combined cantilever beam model in the frequency range of 0-1000Hz is 13.5-63.6mV / ms -2 , which is not only higher than the sensitivity of the PZT-5A dual piezoelectric combined cantilever beam model, but also higher than the central compression structure model with PMN-PT as the piezoelectric material and the single piezoelectric cantilever beam model. This is because the dual piezoelectric combined cantilever beam structure simultaneously utilizes the d 31 and d 33 Two transducer modes. This shows that using PMN-PT as the sensitive material of the seismic detector can greatly improve the sensitivity of the seismic detector.

[0026] refer to Figure 3 , which is a schematic diagram of the structure of another embodiment of the piezoelectric seismic geophone core of the present invention. Figure 1 The difference between the embodiments shown is that the first end piezoelectric sheet and the second end piezoelectric sheet both have two piezoelectric single crystals, and the piezoelectric single crystals of each are arranged in the same crystal polarization direction and bonded, and the current and voltage transmission between the two connected piezoelectric single crystals can be realized after bonding. In this embodiment, each piezoelectric single crystal is realized by piezoelectric sheets 3, 4, 6, and 7, and the crystal orientation of piezoelectric sheets 6 and 7 is <110> direction, the polarization electric field direction is parallel to the thickness direction, and the transduction mode of the piezoelectric sheet is the d31 transduction mode; the crystal orientation of the piezoelectric sheets 3 and 5 is <001> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the piezoelectric sheet is the d33 transduction mode. The upper and lower surfaces of the piezoelectric sheets 3, 4, 6, and 7 are plated with electrodes, and wires are led out from the upper surfaces of the piezoelectric sheets 4 and 6, and wires are led out from the lower surfaces of the piezoelectric sheets 3 and 7. Among them, the piezoelectric sheets 3 and 4 form a group of outputs, and the piezoelectric sheets 6 and 7 form a group of outputs, and the two groups of output currents are connected in parallel or voltages are output in series. In another embodiment of the present invention, the upper surface of the piezoelectric sheet 3 and the lower surface of the piezoelectric sheet 4, and the upper surface of the piezoelectric sheet 7 and the lower surface of the piezoelectric sheet 6 do not need to be connected to each other, but the output wires are led out separately and then processed, and the processing method also meets the output mode of voltage series output or current parallel output. The specific method belongs to the common knowledge in the field and will not be repeated here.

[0027] The working principle of the present invention is that when the core of the piezoelectric cantilever beam is subjected to the vibration of the earth, the piezoelectric cantilever beam will vibrate with the same frequency and amplitude as the vibration of the earth. Due to the action of the mass block, the piezoelectric material at the B end of the piezoelectric cantilever beam will be deformed by force. Due to the positive piezoelectric effect of the piezoelectric material, when the piezoelectric material is deformed, the mechanical energy will be converted into electrical energy. Then, the electrical signals on the two piezoelectric sheets are collected to obtain the seismic electrical signals. It should be understood that the above Figure 1 and Figure 3 In the embodiment shown, the above-mentioned mass block may be omitted, and the core can still work normally; the first-end voltage plate and the second-end voltage plate do not have to be arranged at the left and right end points of the end where the cantilever beam base is located. The distance between the first-end voltage plate and the second-end voltage plate and the end points of the end where the cantilever beam base is located shall not exceed one-third of the length of the cantilever beam base, which can better meet the design requirements of the detector.

[0028] The core structure of the present invention is simple, light, and small in size. It utilizes the structure of a single piezoelectric cantilever beam and is suitable for use in low-frequency vibration environments. It also has the characteristic of increasing sensitivity with frequency. Since seismic wave signals are lost during propagation, the higher the frequency of the seismic wave, the greater the amplitude attenuation during propagation. This can compensate, to a certain extent, for the attenuation of the seismic wave amplitude as the frequency increases.

[0029] The detector core structure provided by the present invention utilizes the vibration of the surrounding environment to drive the cantilever beam structure to vibrate, so as to cause the piezoelectric piece to bend and deform, thereby generating an effective potential between different electrodes of the piezoelectric piece, thereby enabling the piezoelectric to output energy more effectively.

[0030] The detector core structure provided by the present invention gives full play to the anisotropic performance of the piezoelectric single crystal (PMN-PT) and makes full use of the d 31 and d 33 Two transducer modes. The electrodes of the piezoelectric sheet are set as upper and lower surface electrodes, and the polarization direction is consistent with the extrusion direction (thickness direction). The Poisson effect of the piezoelectric sheet itself when it is bent is used to more effectively exert the performance of the piezoelectric sheet and improve the energy output efficiency of the piezoelectric sheet.

[0031] In general, the seismic detector with the core structure provided by the present invention has the advantages of high sensitivity, strong anti-interference ability, wide dynamic range, lightness and durability, and is more reliable and widely used in the fields of downhole slot wave seismic exploration and onshore seismic exploration.

[0032] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A piezoelectric seismic detector core, characterized in that: It comprises a cantilever beam base made of elastic material and a first-end piezoelectric sheet and a second-end piezoelectric sheet respectively located at two ends of the cantilever beam base, one end of the cantilever beam base is used to rigidly connect to the inner wall of the shell of the piezoelectric seismic detector, the lower surface of the first-end piezoelectric sheet is fixed to one end of the cantilever beam base, the lower surface of the second-end piezoelectric sheet is fixed to the other end of the cantilever beam base, and the first-end piezoelectric sheet and the second-end piezoelectric sheet are electrically connected to an output wire to output the respectively sensed electrical signals in voltage series or current parallel connection; The first-end piezoelectric sheet and the second-end piezoelectric sheet are both single-layer structures, and are made of piezoelectric single crystal PMN-PT; The crystal orientation of the piezoelectric film at the second end is <110> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the second end piezoelectric piece is d 31 Transducer mode; the crystal orientation of the first end piezoelectric piece is <001> direction, the polarization electric field direction is parallel to its thickness direction, and the transduction mode of the piezoelectric piece at the first end is d 33 Transducer mode; The upper surface and the lower surface of each piezoelectric sheet in the first end piezoelectric sheet and the second end piezoelectric sheet are respectively provided with an upper surface electrode and a lower surface electrode, and each upper surface electrode and each lower surface electrode respectively lead out an output wire; A mass block is fixed in the area where one end of the cantilever beam base is located, and the other end is used to be rigidly connected to the inner wall of the shell of the piezoelectric seismic detector; the mass block is located on the upper surface of the first end piezoelectric sheet, and the lower surface of the mass block is the same in shape and size as the upper surface of the first end piezoelectric sheet connected to it, and the two are connected to each other in a completely covering manner; Among them, the lower surface of the piezoelectric piece at the second end is pasted to the end of the cantilever beam base, namely the A end, the A end of the cantilever beam base is rigidly connected to the base, and the base is rigidly connected to the outer shell of the piezoelectric seismic detector; the lower surface of the piezoelectric piece at the first end is pasted to the other end of the cantilever beam base, namely the B end, and a mass block is fixed on the upper surface of the piezoelectric piece at the first end.

2. The piezoelectric geophone core according to claim 1, characterized in that: The cantilever beam base is made of beryllium bronze or phosphor bronze.

3. The piezoelectric geophone core according to claim 1, characterized in that: The electrode materials of the upper and lower surface electrodes of the first end piezoelectric sheet and the second end piezoelectric sheet are silver or gold; the output wires drawn from the upper and lower surface electrodes of the first end piezoelectric sheet and the second end piezoelectric sheet are copper wires.

4. The piezoelectric geophone core according to claim 1, characterized in that: The lower surfaces of the first end piezoelectric sheet and the second end piezoelectric sheet are both fixed to the cantilever beam base by bonding.

5. A piezoelectric seismic geophone, characterized in that: It comprises a piezoelectric geophone core as claimed in any one of claims 1 to 4, wherein one end of the cantilever beam base of the piezoelectric geophone core is rigidly connected to the inner wall of the shell of the piezoelectric geophone.

6. The piezoelectric geophone according to claim 5, characterized in that: One end of the cantilever beam base of the piezoelectric seismic detector core is rigidly connected to the inner wall of the shell of the piezoelectric seismic detector through a base, and one end of the cantilever beam base of the piezoelectric seismic detector core is rigidly connected to the base, and the base is rigidly connected to the inner wall of the shell of the piezoelectric seismic detector.

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