H2S gas detection device and method based on non-contact cantilever beam enhanced photoacoustic spectrometry

Abstract

The invention discloses a non-contact cantilever beam enhanced photoacoustic spectrometry H2S gas detection device and method. The device comprises H2S gas detection devices arranged in a construction drilling well and an oil and gas production well; the H2S gas detection device adopts an optical fiber F-P interferometer structure and comprises an optical fiber F-P microphone and a non-resonance photoacoustic cell; each H2S gas detection device is connected with a modulation-demodulation instrument through a multi-path optical switch; and the connection modulation-demodulation instrument is connected with the computer system. By means of the H2S gas detection device based on the photoacoustic spectrum, multi-well long-distance non-contact safe real-time monitoring of H2S gas leakage possibly occurring at a well mouth of an oil and gas resource exploration well or an oil and gas production well can be achieved; the H2S gas detection device based on the photoacoustic spectrum is installed and arranged at all well mouths in a monitoring area; and long-term and real-time H2S gas concentration measurement and safety monitoring are carried out on underground H2S gas leakage risks possibly occurring in drilling or oil and gas resource production of all wellheads.

Description

Technical Field

[0001] The invention belongs to the technical field of geophysical exploration and ground and well monitoring, and in particular relates to a H2S gas detection device and method using a non-contact cantilever beam enhanced photoacoustic spectroscopy. Background Art

[0002] As early as 1880, scientists discovered the effect and reported it, but due to theoretical and technical limitations, the application of the effect did not develop for more than half a century. It was not until the advent of lasers that the application developed rapidly. As an important branch of spectroscopy, spectroscopy technology is different from traditional spectroscopy in that it does not detect the light signal after the interaction between light and tissue, thus overcoming many difficulties in traditional spectroscopy in sample analysis.

[0003] In traditional spectroscopy, light scattering and reflection are the biggest interferences, because the amount of light energy absorbed by the sample is determined by measuring the intensity of the transmitted light and subtracting the difference between the intensity of the transmitted light and the intensity of the incident light. The interaction between light and tissue is inevitably accompanied by certain reflections, scattering and other light losses, which will lead to a decrease in the intensity of the incident light. In addition, traditional spectroscopy detects the transmitted light signal after the interaction between light and tissue, so the sample must have a certain degree of light transmittance. In contrast, photoacoustic spectroscopy detects the mechanical waves generated by the absorption of light energy by the tissue, and the strength of this mechanical wave directly reflects the amount of light energy absorbed by the material. This avoids signal interference caused by reflection and scattering of light in the sample; at the same time, the irradiation power of the incident light can be appropriately increased for weakly absorbing samples to improve the signal-to-noise ratio. Therefore, it is widely used in various sample detections, such as transparent or opaque solids, liquids, gases, powders, colloids, crystals or amorphous materials, etc., which essentially solves the problem of traditional spectroscopy in detecting weakly absorbing, strongly scattering, opaque and other samples.

[0004] It describes the interaction between light and matter, that is, when a beam of modulated or pulsed laser is irradiated onto a tissue sample, the absorber in the tissue body undergoes local thermal expansion after absorbing light energy, thereby generating mechanical waves and forming outward mechanical waves. This mechanical wave is easily received by the detector placed around the tissue body. In the process of continuous change of the incident laser wavelength, the strength of the signal received by the detector will also change accordingly with the absorption spectrum of the absorber, thereby obtaining the corresponding signal spectrum. It not only depends on the photon characteristics, but also reflects the thermal properties (thermal conductivity, thermal diffusivity, specific heat, etc.) and spectral properties of the measured material. Therefore, the thermal and spectral properties of the material can be determined by detecting the ability of light conversion.

[0005] When a substance absorbs light and is excited, it can return to its initial state through radiative transition or non-radiative transition. The former process produces fluorescence or phosphorescence, while the latter process produces heat. Because the intensity of the absorbed light changes periodically, the pressure fluctuation in the container is also periodic. When the sample is a gas or liquid, it is itself a pressure medium. The electrical signal obtained by synchronously amplifying the mechanical wave sensed by the element is an optical signal. If the signal is recorded as a function of the frequency of the incident light, a spectrum can be obtained.

[0006] Spectroscopy is a new technology for studying the absorption spectrum of substances and has become an important branch of molecular spectroscopy. As a powerful analytical tool in the field of modern biomedicine, spectroscopy overcomes the influence of tissue scattering characteristics on measurement results and provides a highly sensitive, non-destructive and effective detection method for the study of biological tissue samples without pretreatment.

[0007] The principle of photoacoustic spectroscopy is to irradiate a sample sealed in a photoacoustic cell with a beam of monochromatic light with modulated intensity. The sample absorbs light energy and de-excites by releasing heat energy. The released heat energy causes the sample and the surrounding medium to be heated periodically according to the modulation frequency of the light, thereby causing the medium to produce periodic pressure fluctuations. This pressure fluctuation can be detected by a sensitive microphone or piezoelectric ceramic microphone, and a photoacoustic signal can be obtained by amplification. This is the photoacoustic effect. If the wavelength of the incident monochromatic light is variable, the photoacoustic signal spectrum that varies with the wavelength can be measured. This is the photoacoustic spectrum. If the incident light is a focused thin beam of light and moves in the xy axis scanning mode of the sample, the photoacoustic signal that changes with the position of the sample can be recorded. This is the photoacoustic imaging technology.

[0008] Photoacoustic spectroscopy is a spectrocalorimetric technique that directly measures the heat energy generated by a substance due to absorption of light energy. Gas molecules absorb light of a specific wavelength in the photoacoustic cell and are excited to a high energy state, and then convert the absorbed light energy into heat energy in the form of a non-radiative transition and return to the ground state. Since the excitation light is modulated periodically, the gas temperature in the closed absorption gas cell also changes periodically, which manifests itself as a change in pressure on a macro scale, that is, the generation of sound waves. The content of the absorbing gas can be inferred by detecting the amplitude of the sound wave. The resonant photoacoustic system modulates the light source at a certain intrinsic frequency of the sound wave propagating in the photoacoustic cell. The sound wave forms a standing wave in the photoacoustic cell, thereby achieving resonant amplification and improving the sensitivity of photoacoustic detection. The coupling effect of the cell wall absorption on the resonance mode is very small, which is conducive to reducing the noise caused by the cell wall absorption.

[0009] Trace gas detection technology has important application value in the fields of atmospheric environment monitoring, medical clinical diagnosis, coal mine safety monitoring, online monitoring of power facilities, etc. Among the many gas detection technologies, laser photoacoustic spectroscopy has the advantages of high sensitivity and low cross-interference, and therefore has received widespread attention.

[0010] Since the detection sensitivity of photoacoustic spectroscopy is proportional to the sensitivity and signal-to-noise ratio of the acoustic sensor, a variety of high-performance optical acoustic sensors such as optical cantilever acoustic sensors and fiber optic sensors have gradually replaced traditional electret microphones. In 2004, Kauppinen et al. designed a silicon microcantilever optical microphone based on Michelson interferometer and proposed a cantilever enhanced photoacoustic spectroscopy (CEPAS) detection scheme. Compared with diaphragm microphones, optical cantilever microphones have the advantages of good low-frequency response, high sensitivity and large dynamic response range. However, the traditional optical cantilever microphone adopts the Michelson interferometer structure, which has the disadvantages of large size, complex system and inconvenient matching with the photoacoustic cell. The fiber Fabry-Perot (FP) microphone can effectively solve the above-mentioned shortcomings. The sensor uses the fiber end face and the diaphragm to form an FP interferometer. When the sound wave acts on the diaphragm, it vibrates, causing the change of the optical path difference of the interferometer. Its advantage is that the acoustic impedance of the diaphragm is low, so higher sensitivity can be obtained. In addition, the microphone probe based on the FP interferometer structure is small in size and suitable for matching with the photoacoustic cell, which can effectively improve the overall detection performance of the photoacoustic spectroscopy detection system. Summary of the invention

[0011] In order to achieve long-distance, non-contact, safe and real-time monitoring of possible H2S gas leakage at the wellheads of oil and gas exploration drilling or oil and gas production wells, H2S gas detection devices based on photoacoustic spectroscopy are installed at all wellheads in the monitoring area to conduct long-term real-time H2S gas concentration measurement and safety monitoring of the H2S gas leakage risks that may occur at all wellheads during drilling or oil and gas resource production.

[0012] In order to solve the above technical problems, the present invention adopts the following solutions:

[0013] A non-contact cantilever beam enhanced photoacoustic spectroscopy H2S gas detection device includes an H2S gas detection device arranged in a construction drilling well and an oil and gas production well; the H2S gas detection device adopts an optical fiber FP interferometer structure, including an optical fiber FP microphone and a non-resonant photoacoustic cell; each H2S gas detection device is connected to a modulation and demodulation instrument through a multi-way optical switch; the modulation and demodulation instrument is connected to a computer system; the modulation and demodulation instrument and the computer system are kept at a distance from the construction drilling well or the oil and gas production well.

[0014] The optical fiber FP microphone comprises a stainless steel housing, a ceramic pin is arranged inside the stainless steel housing, and the ceramic pin is connected to the optical fiber outside the front end of the stainless steel housing; a stainless steel cantilever beam diaphragm is arranged at the rear end of the stainless steel housing;

[0015] The non-resonant photoacoustic cell has air holes at both ends, and the detected H2S gas enters and exits the inner cavity of the non-resonant photoacoustic cell through the air holes;

[0016] A polyethylene film having corrosion resistance and air tightness is provided on one side of the non-resonant photoacoustic cell, and a stainless steel cantilever beam diaphragm of the optical fiber FP microphone is provided on the outside of the polyethylene film;

[0017] The detected H2S gas enters the non-resonant photoacoustic cell through the pores. The laser and H2S gas interact to generate photoacoustic signals, which pass through the polyethylene film to cause forced vibration of the stainless steel cantilever beam diaphragm. The weak photoacoustic signal generated by the vibration of the stainless steel cantilever beam diaphragm is measured by the optical fiber FP microphone. The polyethylene film cannot allow gas to pass through, but can allow sound to pass through. The polyethylene film is in contact with the H2S gas, while the stainless steel cantilever beam diaphragm is not in contact with the H2S gas.

[0018] The inner wall of the non-resonant photoacoustic cell is polished and gold-plated to reduce the interference of cell wall absorption, an optical window with a transmittance greater than 90% is used to seal the incident port, and a gold-plated reflector is installed at the other end of the non-resonant photoacoustic cell to increase the effective power of the photoacoustic excitation light.

[0019] Preferably, the optical fiber FP microphone is installed in the middle of the side of the non-resonant photoacoustic cell to obtain the maximum signal amplitude.

[0020] The modulation and demodulation instrument is a high-performance modulation and demodulation instrument that uses time division multiplexing and frequency division multiplexing to achieve multi-point quasi-distributed measurement; the modulation and demodulation instrument can also be combined with multiple lasers to achieve quasi-distributed-contactless fiber-optic photoacoustic multi-gas sensing; the modulation and demodulation instrument can also be combined with an optical frequency comb to achieve quasi-distributed-contactless fiber-optic photoacoustic multi-gas sensing with a single light source;

[0021] The laser light sources of non-resonant photoacoustic cells include: Ar ion laser, He-Ne laser, CO2 laser, semiconductor laser and tunable special dye laser or quantum multi-level laser, and have the characteristics of good monochromaticity, high pulse peak power and wide spectral range;

[0022] The detection method of the H2S gas detection device using non-contact cantilever beam enhanced photoacoustic spectroscopy comprises the following steps:

[0023] (1) Deploy a modem instrument and a computer system connected to the H2S gas detection device at the middle position of the construction drilling well or oil and gas production well group where non-contact real-time monitoring of H2S gas is required;

[0024] (2) Install an H2S gas detection device near the wellhead of each construction drilling well or oil and gas production well that requires non-contact real-time monitoring of H2S gas;

[0025] (3) Connect each H2S gas detection device to the input end of the multi-way optical switch through an optical fiber, and then connect the output end of the multi-way optical switch to the modulation and demodulation instrument;

[0026] (4) Start the modem instrument and computer system to perform self-test and calibration on all H2S gas detection devices installed at the monitoring wellhead to ensure that the entire system can work normally;

[0027] (5) Start the modulation and demodulation instrument to inject the laser that excites the H2S gas into the non-resonant photoacoustic cell through the transmission optical fiber and the collimator. For the first-order longitudinal resonant photoacoustic cell, the nodes of the sound wave are at both ends of the resonance tube, and the inlet and outlet of the non-resonant photoacoustic cell are set at both ends of the buffer tank, which does not affect the pressure distribution in the cell and can also avoid the noise generated by the gas flow;

[0028] (6) The weak acoustic wave signal generated by the H2S gas absorbing the laser is received by the fiber FP microphone and converted into a voltage signal by the acoustic wave intensity demodulation system. After the weak photoacoustic signal is processed by the FPGA-based phase-locked amplifier, the intensity value of the photoacoustic signal is monitored using the second harmonic detection technology, and the weak acoustic wave signal monitored and measured in real time by the fiber FP microphone is transmitted to the computer system for real-time processing and mapping;

[0029] (7) When the non-resonant photoacoustic cell of the H2S gas detection device installed at a wellhead contacts the H2S gas leaking from the well to the ground, the H2S gas in the non-resonant photoacoustic cell absorbs the laser and generates a weak acoustic wave signal. At this time, the weak acoustic wave signal received by the optical fiber FP microphone is immediately transmitted to the technical computing system for real-time processing and analysis.

[0030] (8) Displaying the H2S gas concentration values ​​monitored and measured in real time by the H2S gas detection devices at all monitoring wellheads on a three-dimensional topographic map of the monitoring area, interpolating the values ​​using a three-dimensional numerical interpolation method, and correcting the regional wind direction and wind speed of the interpolated data using the regional wind direction and wind speed at the same time, and finally forming a three-dimensional spatial distribution map of the H2S gas in the monitoring area above the ground and a real-time three-dimensional spatial distribution change trend map over time; the three-dimensional numerical interpolation method includes but is not limited to nearest neighbor interpolation, linear interpolation, polynomial interpolation, Kriging interpolation, spline interpolation, radial basis function interpolation and other methods;

[0031] (9) When the H2S gas concentration monitored or measured by the H2S gas detection device at a wellhead or several wellheads in the monitoring area exceeds the pre-set safety threshold, the computer system will immediately activate the alarm device installed at the wellhead to warn the operators at the well site to immediately close the blowout prevention device or pipeline valve at the relevant wellhead and quickly evacuate the relevant well site;

[0032] (10) The computer system simultaneously sends an alarm message to the professional H2S gas leak handling department and activates the major H2S gas leak safety warning mechanism. The professional H2S gas leak handling operation team immediately rushes to the H2S gas leak well site to professionally handle the H2S gas leak incident to prevent major casualties.

[0033] The beneficial effects of the present invention are as follows: The purpose of the present invention is to provide a non-contact cantilever beam enhanced photoacoustic spectroscopy H2S gas detection system and monitoring method to solve the safety risk problem of underground H2S gas leaking to the ground through boreholes or pipes in oil and gas resource exploration wells and production wells. The present invention can realize multi-well long-distance non-contact safe real-time monitoring of H2S gas leakage that may occur at the wellheads of oil and gas resource exploration drilling or oil and gas production wells. By installing H2S gas detection devices at all wellheads in the monitoring area, long-term real-time H2S gas concentration measurement and safety monitoring of underground H2S gas leakage risks that may occur at all wellheads during drilling or oil and gas resource production can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the layout of the H2S gas detection device of the non-contact cantilever beam enhanced photoacoustic spectroscopy of the present invention.

[0035] Figure 2 It is a schematic diagram of the structure of the optical fiber FP microphone of the present invention.

[0036] Figure 3 It is a structural schematic diagram of the H2S gas detection device of the present invention.

[0037] Reference numerals:

[0038] 1- construction drilling, 2- oil and gas production well, 3- H2S gas detection device, 31- optical fiber, 32- ceramic pin, 33- stainless steel shell, 34- stainless steel cantilever beam diaphragm, 35- polyethylene film, 36- optical fiber FP microphone, 37- non-resonant photoacoustic cell, 38- inlet and outlet holes, 4- modulation and demodulation instrument, 5- multi-way optical switch, 6- computer system. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0040] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inside", "outside", "front", "back", "top", "bottom" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0041] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed", "opened", "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] like Figure 1 As shown in the schematic diagram of the layout of the long-distance non-contact H2S gas concentration monitoring and measurement system, the H2S gas detection device of the non-contact cantilever beam enhanced photoacoustic spectroscopy includes a construction well 1, an oil and gas production well 2, an H2S gas detection device 3, a modem instrument 4 connected to the H2S gas detection device 3, a multi-way optical switch 5, and a computer system 6 connected to the modem instrument 4. The modem instrument 4 and the computer system 6 of the H2S gas detection device 3 are set up on an open space at a certain distance from the construction well 1 or the oil and gas production well 2;

[0043] The H2S gas detection device 3 adopts a fiber FP interferometer structure, including a fiber FP microphone 36 and a non-resonant photoacoustic cell 37; Figure 2 3 is a schematic diagram of the structure of the fiber optic FP microphone 36. The fiber optic FP microphone 36 is composed of an optical fiber 31, a ceramic pin 32, a stainless steel housing 33 and a stainless steel cantilever beam diaphragm 34. The stainless steel housing 33 is provided with a ceramic pin 32, the ceramic pin 32 is connected to the optical fiber 31, and the stainless steel housing 33 is provided with a stainless steel cantilever beam diaphragm 34 at the tail end.

[0044] A corrosion-resistant and airtight polyethylene film 35 is placed at the end of the stainless steel cantilever beam diaphragm 34. Gases will not pass through the polyethylene film 35, but sound can pass through the polyethylene film 35, causing the stainless steel cantilever beam diaphragm 34 to vibrate; the weak photoacoustic signal generated by the vibration of the stainless steel cantilever beam diaphragm 34 is measured by the optical fiber FP microphone 36.

[0045] like Figure 3 As shown, the polyethylene film 35 is connected to the non-resonant photoacoustic cell 37. There are air holes 38 at both ends of the non-resonant photoacoustic cell 37. The detected H2S gas enters the non-resonant photoacoustic cell 37 through the air holes 38. The laser and the H2S gas interact to generate a photoacoustic signal. The photoacoustic signal passes through the polyethylene film 35 to cause the forced vibration of the stainless steel cantilever beam diaphragm 34. The polyethylene film 35 is in contact with the H2S gas, and the stainless steel cantilever beam diaphragm 34 is not in contact with the H2S gas.

[0046] The inner wall of the non-resonant photoacoustic cell 37 is polished and gold-plated to reduce the interference of the cell wall absorption, an optical window with a transmittance greater than 90% is used to seal the incident port, and a gold-plated reflector is installed at the other end of the non-resonant photoacoustic cell 37 to increase the effective power of the photoacoustic excitation light;

[0047] The fiber FP microphone 36 is installed in the middle of the non-resonant photoacoustic cell 37 to obtain the maximum signal amplitude;

[0048] The modem instrument 4 is a high-performance modem instrument that uses time division multiplexing and frequency division multiplexing to achieve multi-point quasi-distributed measurement;

[0049] The modem instrument 4 can also be combined with multiple lasers to achieve quasi-distributed-contactless fiber optic photoacoustic multi-gas sensing;

[0050] The modulation and demodulation instrument 4 can also be combined with an optical frequency comb to achieve quasi-distributed-contactless fiber optic photoacoustic multi-gas sensing with a single light source;

[0051] The laser light source of the non-resonant photoacoustic cell 37 includes: Ar ion laser, He-Ne laser, CO2 laser, semiconductor laser and tunable special dye laser or quantum multi-level laser, and has the characteristics of good monochromaticity, high pulse peak power and wide spectral range;

[0052] The detection method of the H2S gas detection device of the non-contact cantilever beam enhanced photoacoustic spectroscopy comprises the following steps:

[0053] (a) A modem instrument 4 and a computer system 6 connected to an H2S gas detection device 3 are arranged at the middle position of a construction well 1 or an oil and gas production well group 2 where non-contact real-time monitoring of H2S gas is required;

[0054] (b) Install an H2S gas detection device 3 near the wellhead of each construction well 1 or oil and gas production well 2 where non-contact real-time monitoring of H2S gas is required;

[0055] (c) connecting each H2S gas detection device 3 to the input end of the multi-way optical switch 5 through an optical fiber, and then connecting the output end of the multi-way optical switch 5 to the modulation and demodulation instrument 4;

[0056] (d) Start the modem instrument 4 and the computer system 6 to perform self-test and calibration on all H2S gas detection devices 3 deployed at the monitoring wellheads to ensure that the whole system can work normally;

[0057] (e) Start the modem 4 to inject the laser that excites the H2S gas into the non-resonant photoacoustic cell 37 through the transmission optical fiber and the collimator. For the first-order longitudinal resonant photoacoustic cell, the nodes of the sound wave are at both ends of the resonance tube, and the gas inlet and outlet of the photoacoustic cell are set at both ends of the buffer cell, which does not affect the pressure distribution in the cell and can also avoid the noise generated by the gas flow;

[0058] (f) The weak acoustic wave signal generated by the H2S gas absorbing the laser is received by the optical fiber FP microphone 36 and converted into a voltage signal by the acoustic wave intensity demodulation system. After the weak photoacoustic signal is processed by the FPGA-based phase-locked amplifier, the intensity value of the photoacoustic signal is monitored using the second harmonic detection technology, and the weak acoustic wave signal monitored and measured in real time by the optical fiber FP microphone 36 is transmitted to the computer system 6 for real-time processing and mapping;

[0059] (g) When the non-resonant photoacoustic cell 37 of the H2S gas detection device 3 arranged at a wellhead contacts the H2S gas leaked from the well to the ground, the H2S gas in the non-resonant photoacoustic cell 37 absorbs the laser and generates a weak acoustic wave signal. At this time, the weak acoustic wave signal received by the optical fiber FP microphone 36 is immediately transmitted to the technical computing system 6 for real-time processing and analysis;

[0060] (h) Displaying the H2S gas concentration values ​​monitored and measured in real time by the H2S gas detection devices 3 at all monitoring wellheads on a three-dimensional topographic map of the monitoring area, interpolating the values ​​using a three-dimensional numerical interpolation method, and correcting the regional wind direction and wind speed of the interpolated data using the regional wind direction and wind speed at the same time, and finally forming a three-dimensional spatial distribution map of the H2S gas in the monitoring area above the ground and a real-time three-dimensional spatial distribution change trend map over time; the three-dimensional numerical interpolation method includes but is not limited to nearest neighbor interpolation, linear interpolation, polynomial interpolation, Kriging interpolation, spline interpolation, radial basis function interpolation and the like;

[0061] (i) When the H2S gas concentration monitored or measured by the H2S gas detection device 3 at a wellhead or several wellheads in the monitoring area exceeds the preset safety threshold, the computer system will immediately activate the alarm device installed at the wellhead to warn the operators at the well site to immediately close the blowout prevention device or pipeline valve at the relevant wellhead and quickly evacuate the relevant well site;

[0062] (j) Computer system 6 simultaneously sends an alarm message to the professional H2S gas leakage handling department and activates a major H2S gas leakage safety warning mechanism. The professional H2S gas leakage handling operation team immediately rushes to the H2S gas leakage well site to professionally handle the H2S gas leakage incident to prevent major casualties.

[0063] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. According to the technical essence of the present invention, within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A non-contact cantilever beam enhanced photoacoustic spectroscopy H2S gas detection device, characterized in that: The invention comprises an H2S gas detection device (3) arranged beside the wellhead of a construction well (1) and an oil and gas production well (2); the H2S gas detection device (3) adopts an optical fiber FP interferometer structure, comprising an optical fiber FP microphone (36) and a non-resonant photoacoustic cell (37); each H2S gas detection device (3) is connected to a modulation and demodulation instrument (4) via an optical cable and a multi-channel optical switch (5); the modulation and demodulation instrument (4) is connected to a computer system (6); the modulation and demodulation instrument (4) and the computer system (6) are kept at a distance from the construction well (1) or the oil and gas production well (2).

2. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1 is characterized in that: The optical fiber FP microphone (36) comprises a stainless steel housing (33), a ceramic pin (32) is arranged inside the stainless steel housing (33), and the ceramic pin (32) is connected to an optical fiber (31) outside the front end of the stainless steel housing (33); a stainless steel cantilever beam diaphragm (34) is arranged at the rear end of the stainless steel housing (33); The non-resonant photoacoustic cell (37) has air holes (38) at both ends, and the detected H2S gas enters and exits the inner cavity of the non-resonant photoacoustic cell (37) through the air holes (38); A polyethylene film (35) having corrosion resistance and airtightness is provided on one side of the non-resonance photoacoustic cell (37), and a stainless steel cantilever beam diaphragm (34) of the optical fiber FP microphone (36) is provided on the outside of the polyethylene film (35); The detected H2S gas enters the non-resonant photoacoustic cell (37) through the air hole (38), and the laser and the H2S gas interact to generate a photoacoustic signal, which passes through the polyethylene film (35) to cause the forced vibration of the stainless steel cantilever beam diaphragm (34); the weak photoacoustic signal generated by the vibration of the stainless steel cantilever beam diaphragm (34) is measured by the optical fiber FP microphone (36); the polyethylene film (35) cannot allow gas to pass through, but can allow sound to pass through; the polyethylene film (35) is in contact with the H2S gas, and the stainless steel cantilever beam diaphragm (34) is not in contact with the H2S gas.

3. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The inner wall of the non-resonant photoacoustic cell (37) is polished and gold-plated to reduce interference caused by absorption of the cell wall, an optical window with a transmittance greater than 90% is used to seal the incident port, and a gold-plated reflector is installed at the other end of the non-resonant photoacoustic cell (37) to increase the effective power of the photoacoustic excitation light.

4. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The optical fiber FP microphone (36) is installed in the middle of the side of the non-resonant photoacoustic cell (37) to obtain the maximum signal amplitude.

5. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The modulation and demodulation instrument (4) is a high-performance modulation and demodulation instrument which adopts time division multiplexing and frequency division multiplexing to realize multi-point quasi-distributed measurement.

6. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The modulation and demodulation instrument (4) is combined with multiple lasers to form a quasi-distributed non-contact optical fiber photoacoustic multi-gas sensor.

7. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The modulation and demodulation instrument (4) is combined with an optical frequency comb to form a quasi-distributed non-contact optical fiber photoacoustic multi-gas sensor with a single light source.

8. The H2S gas detection device of non-contact cantilever beam enhanced photoacoustic spectroscopy according to claim 1, characterized in that: The laser light source acting in the non-resonance photoacoustic cell (37) includes: Ar ion laser, He-Ne laser, CO2 laser, semiconductor laser and adjustable special dye laser or quantum multi-level laser.

9. A method for detecting H2S gas by non-contact cantilever beam enhanced photoacoustic spectroscopy, characterized in that: The H2S gas detection device using the non-contact cantilever beam enhanced photoacoustic spectroscopy according to any one of claims 1 to 8, wherein the method comprises the following steps: (a) deploying a modem instrument (4) and a computer system (6) connected to an H2S gas detection device (3) at the middle position of a construction well (1) or a group of oil and gas production wells (2) where non-contact real-time monitoring of H2S gas is required; (b) installing an H2S gas detection device (3) next to the wellhead of each construction well (1) or oil and gas production well (2) where non-contact real-time monitoring of H2S gas is required; (c) connecting each H2S gas detection device (3) to the input end of the multi-way optical switch (5) via an optical cable, and then connecting the output end of the multi-way optical switch (5) to the input end of the modulation and demodulation instrument (4); (d) starting the modem instrument (4) and the computer system (6) to perform self-test and calibration on all H2S gas detection devices (3) arranged at the monitoring wellheads to ensure that the entire system can work normally; (e) starting the modulation and demodulation instrument (4) to guide the laser that excites the H2S gas into the non-resonant photoacoustic cell (37) via the transmission optical fiber and the collimator; for the first-order longitudinal resonant photoacoustic cell, the nodes of the sound wave are at both ends of the resonant tube; (f) The weak acoustic wave signal generated by the H2S gas absorbing the laser is received by the optical fiber FP microphone (36) and converted into a voltage signal by the acoustic wave intensity demodulation system; after the weak photoacoustic signal is processed by the FPGA-based phase-locked amplifier, the intensity value of the photoacoustic signal is monitored using the second harmonic detection technology, and the weak acoustic wave signal monitored and measured in real time by the optical fiber FP microphone (36) is transmitted to the computer system (6) for real-time processing and mapping; (g) When the non-resonant photoacoustic cell (37) of the H2S gas detection device (3) arranged next to a wellhead contacts the H2S gas leaking from the well to the ground, the H2S gas in the non-resonant photoacoustic cell (37) absorbs the laser and generates a weak sound wave signal. At this time, the weak sound wave signal received by the optical fiber FP microphone (36) is immediately transmitted to the technical computing system (6) for real-time processing and analysis; (h) displaying the H2S gas concentration values ​​monitored and measured in real time by the H2S gas detection devices (3) at all monitoring wellheads on a three-dimensional topographic map of the monitoring area, performing interpolation processing using a three-dimensional numerical interpolation method, and correcting the regional wind direction and wind speed of the interpolated data using the regional wind direction and wind speed at the same time, and finally forming a real-time three-dimensional spatial distribution map of the H2S gas above the ground in the monitoring area and a real-time three-dimensional spatial distribution change trend map over time; (i) When the H2S gas concentration monitored or measured by the H2S gas detection device (3) at a wellhead or several wellheads in the monitoring area exceeds a preset safety threshold, the computer system will immediately activate the alarm device installed at the wellhead to warn the operators at the well site to immediately close the blowout prevention device or pipeline valve at the relevant wellhead and quickly evacuate the relevant well site; (j) Computer system (6) simultaneously sends an alarm message to the professional H2S gas leakage handling department and activates a major H2S gas leakage safety warning mechanism. The professional H2S gas leakage handling operation team immediately rushes to the H2S gas leakage well site to professionally handle the H2S gas leakage incident.

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