System and method for monitoring combustible gas in tube well

Abstract

The invention discloses a system and a method for monitoring combustible gas in a tube well, and belongs to the technical field of tube well combustible gas leakage monitoring. The system comprises a battery, an optical system, a diffuse reflection sheet, a data processing module, a temperature sensor, a humidity sensor, a pressure sensor, a 4G antenna and a GPS antenna. The method comprises the following steps: emitting a laser signal into a tube well; receiving a reflected light signal which is absorbed by the combustible gas and is enhanced by a diffuse reflection sheet, and converting the reflected light signal into a reference and measurement light path signal; calculating absorbance based on the signal ratio to reduce noise; carrying out concentration inversion calculation; and comprehensively correcting environmental influence factors in combination with temperature, humidity and pressure data to obtain accurate concentration. Through the synergistic effect of light path enhancement, noise suppression and environmental compensation, the problems of weak signals and large environmental interference in the tube well are effectively solved, and the monitoring accuracy, stability and reliability are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of well combustible gas leakage monitoring technology, and in particular to a well combustible gas monitoring system and method. Background Technology

[0002] Combustible gas leakage is one of the major safety risks faced by urban underground pipe networks (such as gas pipelines and municipal manholes). Timely and accurate monitoring of combustible gas concentrations within manholes is crucial for preventing major safety accidents such as explosions and fires. Currently, technologies applied to gas monitoring mainly include semiconductor sensing, catalytic combustion, and optical absorption spectroscopy. Among these, tunable diode laser absorption spectroscopy (TDLAS) is considered a promising gas detection solution due to its high selectivity, non-contact measurement, and rapid response. However, when TDLAS technology is applied to the unique and harsh environment of manholes, existing technologies reveal numerous insurmountable shortcomings, severely limiting their monitoring performance and reliability.

[0003] First, the confined space and complex structure of the well, along with numerous obstacles, severely restrict the laser transmission path. Traditional direct-transmission TDLAS systems require precise alignment, making installation and stable operation difficult within wells. While open-path technology using natural diffuse reflection reduces alignment requirements, the signal attenuates significantly after multiple diffuse reflections within the well, resulting in extremely weak light intensity reaching the detector. This leads to a low signal-to-noise ratio, and the detection limit and accuracy fail to meet the stringent requirements of safety monitoring. Second, the well environment differs drastically from laboratory conditions. Internal temperature and pressure can fluctuate dramatically with seasons, weather, and underground activity, while humidity remains consistently high. The absorption coefficient of gases is strongly dependent on temperature and pressure, and water vapor exhibits a wide absorption spectrum in the near-infrared band, causing severe cross-interference with the characteristic absorption spectra of target gases (such as methane). Most existing TDLAS monitoring devices either do not consider environmental compensation or only perform simple temperature or pressure compensation, making it impossible to achieve accurate concentration inversion in wells where temperature, pressure, and humidity change dynamically at the same time. The measured values ​​often deviate from the true concentration, which can easily lead to false alarms or missed alarms.

[0004] Secondly, existing monitoring systems often focus on the performance of the sensing units themselves, lacking systematic strategies for handling complex noise. Laser-driven noise, optical interference fringes, and environmental electromagnetic interference introduce various types of noise, which are difficult to effectively suppress using only hardware filtering or simple software algorithms, affecting the stability of long-term monitoring. Finally, from a system application perspective, traditional monitoring points typically require wiring, power supply, and communication, resulting in high construction difficulty and cost, and hindering large-scale deployment and centralized management. Data upload delays prevent true real-time early warning and precise location, leading to inefficient emergency response after potential hazards are detected.

[0005] Therefore, there is an urgent need in this field for a combustible gas monitoring system and method that can adapt to the special environment of wells, overcome signal attenuation and complex interference, achieve high-precision and high-reliability monitoring, and have intelligent remote management capabilities, so as to fill the current technological gap and effectively ensure the operational safety of urban underground pipelines. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a pipeline leakage monitoring and early warning system and method. This invention employs a diffuse reflector sheet on the back of the manhole cover to actively enhance the secondary reflected light signal; calculates absorbance using the ratio of the reference optical path signal to the measurement optical path signal to suppress common-mode noise; integrates temperature, humidity, and pressure sensors and constructs a comprehensive compensation algorithm that fuses real-time water vapor subtraction and temperature and pressure coefficient correction; and combines moving average filtering with an IoT edge computing architecture. This solves the problems faced by existing technologies in manhole applications, such as severe signal attenuation, complex environmental interference, significant measurement noise, and difficulties in system deployment and management. It achieves a 30%-50% improvement in the monitoring signal-to-noise ratio, reduces concentration measurement error from over 15% in traditional methods to less than 5%, and simultaneously realizes intelligent remote real-time early warning and precise positioning.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for monitoring combustible gas in a well, comprising the following steps: S1: emitting a laser signal into the well, so that the laser signal passes through the combustible gas in the well; S2: Receive the reflected light signal after being absorbed by the combustible gas, wherein the reflected light signal includes a secondary diffuse reflection signal enhanced by the diffuse reflection sheet on the back of the manhole cover; S3: Convert the reflected light signal into a reference optical path signal and a measurement optical path signal; S4: Calculate the total absorbance based on the ratio of the reference optical path signal to the measurement optical path signal. A total : A total =- ln ( V sig / V ref ) in, V sig To measure the optical path signal, V ref For reference optical path signal; S5: Apply a moving average filter to the calculated total absorbance to obtain the filtered absorbance. A filtered ( t ): in, N To adjust the sliding window size; t The current moment; A total ( t - i )for t - i Total absorbance at any given time; S6: Based on the filtered absorbance A filtered ( t Concentration inversion calculation is performed using the following formula: in, c For gas concentration, e The molar absorptivity is 1. L It is the optical path length; S7: Acquire temperature, humidity, and pressure data inside the well collected by temperature, humidity, and pressure sensors; and adjust the absorbance using temperature and pressure correction algorithms, water vapor subtraction algorithms, and molar absorptivity correction algorithms. A filtered ( t A combined correction is performed to obtain the corrected flammable gas concentration.

[0008] Preferably, the temperature and pressure correction algorithm calculates the corrected absorbance using the temperature and pressure data measured by the temperature sensor and pressure sensor. A corrected : in, A target The absorbance of the target gas, methane; P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These are the measured pressure and measured temperature inside the well, respectively. m It is a constant.

[0009] Preferably, the formula for the water vapor subtraction algorithm is: A target = A total - e 水汽 × c 水汽 × L in, Atarget The absorbance of the target gas, methane; A total The total absorbance is... e 水汽 The absorption coefficient of water vapor is denoted as . c 水汽 Water vapor concentration; L This is the optical path length.

[0010] Preferably, the water vapor concentration c 水汽 The formula is: in, e s This is the saturated water vapor pressure; RH The measured humidity inside the well; P This represents the measured pressure inside the well.

[0011] Preferably, the formula for the molar absorptivity correction algorithm is: in, e The molar absorption coefficient, e 0 represents the molar absorption coefficient under standard conditions. P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These are the measured pressure and measured temperature inside the well, respectively.

[0012] Preferably, the sliding window size N The value range is 4-16.

[0013] Preferably, the method further includes comparing the corrected combustible gas concentration with a preset threshold. If the corrected combustible gas concentration exceeds the threshold, an alarm signal is generated and sent to the cloud server via a wireless communication module. At the same time, the well's geographical location information obtained through a GPS antenna is uploaded. The alarm signal is sent to the user via SMS or a pop-up window on the platform interface.

[0014] A combustible gas monitoring system for wells, used to perform the above-mentioned combustible gas monitoring method for wells, includes: an optical system for emitting laser signals into the well and receiving reflected light signals after being absorbed by combustible gas in the well; A diffuse reflector sheet is fixedly installed on the back of the manhole cover to enhance the reflected light signal; A data processing module, connected to the optical system, is used to process the reflected light signal; Temperature, humidity and pressure sensors are connected to the data processing module to collect temperature, humidity and pressure data inside the well. The optical system, diffuse reflector, and data processing module work together to improve monitoring accuracy by enhancing the optical signal and reducing noise.

[0015] Preferably, the optical system includes a laser, a beam splitter, a filter, a photodetector, and a receiving mirror; The beam splitter divides the laser signal into a reference optical path and a measurement optical path. The reference optical path directly enters the photodetector, while the measurement optical path is absorbed by the combustible gas and then received by the receiving mirror, and the reflected signal is enhanced by the diffuse reflector.

[0016] Preferably, the combustible gas monitoring system further includes a 4G antenna for uploading and receiving data commands and a GPS antenna for calibrating the geographical location of the well.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects.

[0018] (1) This invention targets the well structure and fixes the diffuse reflector as an active reflector on the back of the well cover. By coordinating the diffuse reflector on the back of the well cover with the optical receiving mirror, the intensity of the effective backlight signal is directly enhanced, providing a basis for solving the signal bottleneck in subsequent processing. The measured signal-to-noise ratio is improved by about 30%-50%.

[0019] (2) The present invention is based on the real-time signal ratio of dual optical paths A total =- ln ( V sig / V ref Absorbance calculation and moving average filtering A filtered ( t The collaborative noise reduction mechanism deeply integrates the optical differential measurement principle of the hardware with digital signal processing technology, forming a two-level collaborative noise reduction mechanism of "ratio method to suppress common mode noise" and "moving average to smooth random fluctuations". This significantly improves the quality and stability of the original data, controls the error of the basic absorbance calculation to below 5%, and provides reliable input for high-precision inversion.

[0020] (3) This invention establishes a real-time, interconnected compensation model that simultaneously includes temperature and pressure correction algorithms, water vapor subtraction algorithms, and molar absorptivity correction algorithms, rather than isolated or partial parameter corrections, and integrates the temperature inside the well measured by the sensor. T ,pressure P ,humidity RHThe comprehensive environmental compensation algorithm systematically offsets the main environmental interferences in the well, enabling TDLAS technology to move from stable laboratory environments to complex field conditions, reducing the overall concentration measurement error to within 5%.

[0021] (4) The present invention integrates a built-in battery, edge computing, and 4G / GPS module into an IoT monitoring terminal architecture, which integrates high-precision optical sensing, real-time on-site algorithm processing, and wireless remote control functions to form an "end-cloud" collaborative solution suitable for distributed well monitoring. It realizes low-power, wireless, and intelligent deployment of monitoring points, and builds a real-time online, automatic alarm, and location-traceable security monitoring network, solving the problems of engineering applications.

[0022] (5) This invention enhances the secondary reflected light signal by coordinating the diffuse reflector and the receiving mirror of the optical system, thereby improving the signal-to-noise ratio; the data processing module uses the ratio method to calculate the absorbance, effectively canceling common-mode noise, and combines the environmental data obtained in real time by temperature, humidity and pressure sensors for comprehensive correction. Through the deep integration of the optical differential measurement principle of the hardware and digital signal processing technology, high-precision concentration inversion is achieved, which solves the technical problems of weak signal and large environmental interference in the monitoring of combustible gas in the well, and significantly improves the accuracy, stability and reliability of monitoring. Attached Figure Description

[0023] The following provides a detailed discussion of the manufacture and application of preferred embodiments of the present invention. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in various specific environments. The specific embodiments discussed are merely illustrative of specific ways of manufacturing and using the present invention and do not limit the scope of the invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0024] Figure 1 This is a schematic diagram of the system of the present invention.

[0025] Figure 2 This is a schematic diagram of the optical system of the present invention.

[0026] Among them, 1-battery; 2-4G antenna; 3-data processing module; 4-temperature sensor; 5-humidity sensor; 6-pressure sensor; 7-optical system; 8-GPS antenna; 9-diffuse reflector; 10-manhole cover; 11-laser; 12-photodetector one; 13-filter one; 14-beam splitter; 15-receiving mirror; 16-filter two; 17-photodetector two. Detailed Implementation

[0027] The following provides a detailed discussion of the manufacture and application of preferred embodiments of the present invention. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in various specific environments. The specific embodiments discussed are merely illustrative of specific ways of manufacturing and using the invention and do not limit the scope of the invention.

[0028] This invention addresses the technical problems of severe signal attenuation, complex environmental interference, and difficult system deployment when using TDLAS for combustible gas monitoring in wells in existing technologies. It provides a complete implementation of a combustible gas monitoring system and method for wells. The system hardware composition of this embodiment is as follows: Figure 1 As shown, the system mainly includes a battery 1, a data processing module 3, an optical system 7, a diffuse reflector 9 fixedly mounted on the back of the manhole cover 10, a temperature sensor 4, a humidity sensor 5, and a pressure sensor 6 for collecting environmental data, and a 4G antenna 2 and a GPS antenna 8 for communication and positioning. The battery 1 powers the entire system; the temperature sensor 4, humidity sensor 5, pressure sensor 6, optical system 7, 4G antenna 2, and GPS antenna 8 are all electrically connected to the data processing module 3.

[0029] The specific monitoring method of this embodiment is implemented according to the following steps. First, step S1 is performed: a laser signal of a specific wavelength is emitted into the well by the optical system 7, and the laser signal passes through the combustible gas inside the well. The specific structure of the optical system 7 is as follows: Figure 2 As shown, the light emitted by its laser 11 is split into two paths by the beam splitter 14: one path serves as a reference optical path, which passes through the filter lens 13 and is then received by the photodetector 12, where it is converted into a reference optical path signal. V ref The other path serves as the measurement optical path, directed towards the interior of the well. Then, step S2 is executed: the reflected light signal after absorption by the combustible gas is received. This reflected light signal includes not only the signal captured by the receiving mirror 15 after primary diffuse reflection from the inner wall of the well, but more importantly, the secondary diffuse reflection signal enhanced by the diffuse reflector 9 on the back of the well cover 10, thus significantly increasing the received light intensity. The enhanced measurement optical path is collected by the receiving mirror 15, passes through the second filter mirror 16, and is received and converted into a measurement optical path signal by the second photodetector 17. V sig .

[0030] Next, steps S3 to S5 are performed for signal processing and noise reduction. Data processing module 3 processes the electrical signal corresponding to the received reflected light signal, i.e., based on the reference optical path signal. V ref and measurement optical path signal V sig According to the formula: A total =-ln ( V sig / V ref Calculate the total absorbance. A total To further suppress random noise, a moving average filter is applied to the calculated total absorbance to obtain the filtered absorbance. A filtered ( t In this embodiment, the sliding window size N is 8, determined by the formula: in, N To adjust the sliding window size; t The current moment; A total ( t - i )for t - i Total absorbance at time; of which i From 0 to N -1 is achieved, effectively smoothing out data fluctuations.

[0031] Then, perform step S6: According to the Beer-Lambert law, use the filtered absorbance... A filtered ( t A preliminary concentration inversion calculation is performed, using the following formula: in, c For gas concentration, e The molar absorptivity is 1. L This refers to the optical path length. To obtain accurate concentration, step S7 is executed: comprehensive correction for environmental influencing factors is performed. Data processing module 3 simultaneously acquires the real-time well temperature data collected by temperature sensor 4, humidity sensor 5, and pressure sensor 6. T ,humidity RH and pressure P The correction process first uses a moisture subtraction algorithm, employing the formula: in, e s This is the saturated water vapor pressure; RH The measured humidity inside the well; P The water vapor concentration is calculated based on the measured pressure inside the well, and then according to the formula: A target = A total - e 水汽 × c水汽 × L in, A target The absorbance of the target gas, methane; A total The total absorbance is... e 水汽 The absorption coefficient of water vapor is denoted as . c 水汽 Water vapor concentration; L This represents the optical path length. The absorbance of the target gas, methane, is obtained by subtracting the absorption contribution of water vapor from the total absorbance. A target .

[0032] Subsequently, a temperature and pressure correction algorithm is applied, according to the formula: in, A target The absorbance of the target gas, methane; P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These are the measured pressure and measured temperature inside the well, respectively. m It is a constant.

[0033] Absorbance is corrected for temperature and pressure normalization. Simultaneously, the molar absorptivity correction algorithm is based on the formula: in, e The molar absorption coefficient, e 0 represents the molar absorption coefficient under standard conditions. P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These represent the measured pressure and temperature within the wellbore, respectively. The molar absorption coefficient under standard conditions was determined using real-time temperature and pressure data. e 0 is corrected, and the corrected version is... e Substitute these values ​​into the final concentration calculation formula. Through the above combined corrections, we finally obtain an accurate combustible gas concentration value that is unaffected by environmental fluctuations: .

[0034] This embodiment effectively solves the core challenges in well monitoring through the aforementioned hardware collaboration and algorithmic process. Testing shows that the application of the diffuse reflector 9 improves the system's signal-to-noise ratio by approximately 40%. The two-stage noise reduction using the ratio method and moving average filtering reduces the fluctuation error in the basic absorbance calculation by over 60%. Furthermore, the comprehensive environmental compensation algorithm stabilizes the concentration measurement error, which exceeds 15% under varying temperature, pressure, and high humidity conditions, within 5%. In addition, the system is powered by a built-in battery 1 and achieves wireless remote data transmission and precise geolocation of the well via a 4G antenna 2 and a GPS antenna 8. When the final concentration value calculated by the data processing module 3 exceeds a preset safety threshold, the system immediately sends an alarm signal and GPS location information to the cloud server via the 4G antenna 2, thereby achieving real-time, accurate leak warning and intelligent operation and maintenance management. This fully demonstrates the significant advantages of this invention in improving monitoring accuracy, stability, and engineering practicality.

[0035] The following is in conjunction with the appendix Figure 1-2 To elaborate further.

[0036] This invention relates to a combustible gas monitoring system and method for wells. Figure 1 As shown, the system includes a battery 1, a data processing module 3, an optical system 7, a diffuse reflector 9 fixedly mounted on the back of the manhole cover 10, a temperature sensor 4, a humidity sensor 5, a pressure sensor 6, a 4G antenna 2, and a GPS antenna 8. The battery 1 powers all components; the temperature sensor 4, humidity sensor 5, pressure sensor 6, optical system 7, 4G antenna 2, and GPS antenna 8 are all electrically connected to the data processing module 3. The specific structure of the optical system 7 is as follows... Figure 2 As shown, it includes a laser 11, a beam splitter 14, a first filter 13, a second filter 16, a first photodetector 12, a second photodetector 17, and a receiving mirror 15. The light emitted by the laser 11 is split into two beams by the beam splitter 14: a reference beam and a measurement beam.

[0037] In this embodiment, the monitoring method primarily begins by emitting a laser signal into the wellbore through the optical system 7. After the beam of light in the measurement optical path passes through the combustible gas inside the wellbore, part of it undergoes natural diffuse reflection from the inner wall of the well, while the other part is enhanced by the diffuse reflector 9 on the back of the well cover 10 before being captured by the receiving mirror 15. This design allows the diffuse reflector 9 to act as an active signal enhancement unit, working in conjunction with the receiving mirror 15 to directly enhance the effective backlighting based on the structural characteristics of the wellbore. Experiments show that compared to the traditional scheme that relies solely on natural diffuse reflection, introducing the diffuse reflector 9 can improve the signal-to-noise ratio of the received signal by approximately 40%, providing a crucial hardware foundation for overcoming the bottleneck of subsequent high-precision signal processing.

[0038] The measurement optical path signal collected by receiver 15 is converted into a measurement optical path signal by photodetector 17 after passing through filter 16. V sig Simultaneously, the beam from the reference optical path is directly received by the photodetector 12 via filter 13 and converted into a reference optical path signal. V ref Data processing module 3 then processes these two signals, first according to the formula... A total =- ln ( V sig / V ref Calculate the total absorbance. A total This ratio calculation method suppresses common-mode noise such as laser fluctuations from a hardware perspective. Secondly, to further smooth out random fluctuations such as environmental electromagnetic interference, [further details are needed]. A total Perform a moving average filter to obtain the filtered absorbance. A filtered ( t ): in, N To adjust the sliding window size; t The current moment; A total ( t - i )for t - i The total absorbance at any given time; where the sliding window size N is set to 8 in this embodiment. The hardware ratio method and the software moving average filtering constitute a two-stage collaborative noise reduction mechanism. The former suppresses common-mode noise, while the latter smooths random noise; the two are sequentially coupled. Test results show that this collaborative noise reduction mechanism can reduce the short-term fluctuation error of the original absorbance data by more than 60%, providing stable and clean data input for subsequent concentration inversion, an effect that cannot be achieved by a single noise reduction method.

[0039] Obtain the filtered absorbance A filtered ( t After that, a preliminary concentration inversion is performed according to the Beer-Lambert law, and the formula is as follows: in, c For gas concentration, e The molar absorptivity is 1. L This refers to the optical path length. To achieve accurate measurement, corrections must be made for environmental influences. At this point, the temperature sensor 4, humidity sensor 5, and pressure sensor 6 collect real-time data on the temperature inside the well.T ,humidity RH and pressure P The data is sent to data processing module 3.

[0040] The correction process first executes a water vapor subtraction algorithm to deduct the contribution of water vapor absorption: the formula for the water vapor subtraction algorithm is as follows: A target = A total - e 水汽 × c 水汽 × L in, A target The absorbance of the target gas, methane; A total The total absorbance is... e 水汽 The absorption coefficient of water vapor is denoted as . c 水汽 Water vapor concentration; L This refers to the optical path length. The water vapor concentration... c 水汽 The formula is: in, e s This is the saturated water vapor pressure; RH The measured humidity inside the well; P This represents the measured pressure inside the well.

[0041] Then apply the temperature and pressure correction algorithm, according to the formula: in, A target The absorbance of the target gas, methane; P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These are the measured pressure and measured temperature inside the well, respectively. m The absorbance is normalized by using a constant.

[0042] Meanwhile, according to the molar absorptivity correction algorithm, the formula is: in, e The molar absorption coefficient, e 0 represents the molar absorption coefficient under standard conditions. P 0 and T 0 represents standard pressure and standard temperature, respectively.P and T These represent the measured pressure and temperature inside the well, respectively. The molar absorption coefficient is used to... e Real-time corrections are performed to ultimately obtain the precise concentration of the target gas, methane. c 甲烷 The final calculation formula is: .

[0043] The described water vapor subtraction algorithm and temperature / pressure correction algorithm constitute a linked environmental compensation model with multi-sensor data as real-time input. This model systematically offsets the complex effects of coupled changes in temperature, pressure, and humidity on absorption line intensity and spectral interference. In comparative tests simulating well conditions during the spring-summer transition (temperature variation 15-35℃, humidity 60%-95%), the concentration error reached 18% without using this integrated compensation model, while the error was stably controlled within 5% after applying the linked compensation model of this invention, verifying the significant accuracy improvement brought about by its synergistic characteristics.

[0044] Finally, data processing module 3 will obtain the final precise concentration. c 甲烷 The concentration is compared with a preset safety threshold. When the concentration exceeds the limit, an alarm signal is immediately sent to the cloud server via 4G antenna 2, and the precise geographical location information obtained by GPS antenna 8 is uploaded simultaneously. The entire system is powered by battery 1 and integrates optical sensing, real-time processing, and wireless communication, forming an independent IoT terminal with edge computing capabilities. The technical solution of this invention adopts an integrated "sensing-computing-communication" approach, enabling the high-precision monitoring scheme based on the aforementioned optical enhancement, collaborative noise reduction, and comprehensive compensation to be deployed on a large scale without wiring. In actual deployment tests, after 30 days of continuous monitoring, the concentration reading fluctuation range of this invention's system is much smaller than that of traditional wired sensor networks, demonstrating the high reliability and long-term stability brought about by deep collaboration between hardware and algorithms.

[0045] Although the specification has provided a detailed description, it should be understood that various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention as defined by the appended claims. Furthermore, the specific embodiments described are not intended to limit the scope of the invention, and those skilled in the art will readily understand based on this invention that existing or future-developed processes, machines, manufactures, compositions of matter, means, methods, or steps can perform substantially the same functions or achieve substantially the same results as the embodiments of the invention. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods, or steps within their scope.

Claims

1. A method for monitoring combustible gases in a well, characterized in that, Includes the following steps: S1: Emit a laser signal into the well, so that the laser signal passes through the combustible gas inside the well; S2: Receive the reflected light signal after being absorbed by the combustible gas, wherein the reflected light signal includes a secondary diffuse reflection signal enhanced by the diffuse reflection sheet on the back of the manhole cover; S3: Convert the reflected light signal into a reference optical path signal and a measurement optical path signal; S4: Calculate the total absorbance based on the ratio of the reference optical path signal to the measurement optical path signal. A total : A total =- ln ( V sig / V ref ) in, V sig To measure the optical path signal, V ref For reference optical path signal; S5: Apply a moving average filter to the calculated total absorbance to obtain the filtered absorbance. A filtered ( t ): in, N To adjust the sliding window size; t The current moment; A total ( t - i )for t - i Total absorbance at any given time; S6: Based on the filtered absorbance A filtered ( t Concentration inversion calculation is performed using the following formula: in, c For gas concentration, ε The molar absorptivity is 1. L It is the optical path length; S7: Acquire temperature, humidity, and pressure data inside the well collected by temperature, humidity, and pressure sensors; and adjust the absorbance using temperature and pressure correction algorithms, water vapor subtraction algorithms, and molar absorptivity correction algorithms. A filtered ( t The combined corrections are performed to obtain the corrected flammable gas concentration.

2. The method for monitoring combustible gases in a well as described in claim 1, characterized in that, The temperature and pressure correction algorithm calculates the corrected absorbance using the temperature and pressure data measured by the temperature and pressure sensors. A corrected : in, A target The absorbance of the target gas, methane; P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These are the measured pressure and measured temperature inside the well, respectively. m It is a constant.

3. The method for monitoring combustible gases in a well as described in claim 1, characterized in that, The formula for the water vapor subtraction algorithm is: A target = A total － ε 水汽 × c 水汽 × L in, A target The absorbance of the target gas, methane; A total The total absorbance is... ε 水汽 The absorption coefficient of water vapor is denoted as . c 水汽 Water vapor concentration; L This is the optical path length.

4. The method for monitoring combustible gases in a well as described in claim 3, characterized in that, The water vapor concentration c 水汽 The formula is: in, e s This is the saturated water vapor pressure; RH The measured humidity inside the well; P This represents the measured pressure inside the well.

5. The method for monitoring combustible gases in a well as described in claim 1, characterized in that, The formula for the molar absorptivity correction algorithm is as follows: in, ε The molar absorption coefficient, ε 0 represents the molar absorption coefficient under standard conditions. P 0 and T 0 represents standard pressure and standard temperature, respectively. P and T These represent the measured pressure and temperature inside the well, respectively.

6. The method for monitoring combustible gases in a well as described in claim 1, characterized in that, The size of the sliding window N The value range is 4-16.

7. The method for monitoring combustible gases in a well as described in claim 1, characterized in that, The method further includes comparing the corrected combustible gas concentration with a preset threshold. If the corrected combustible gas concentration exceeds the threshold, an alarm signal is generated and sent to the cloud server via a wireless communication module. At the same time, the well's geographical location information obtained through a GPS antenna is uploaded. The alarm signal is sent to the user via SMS or a pop-up window on the platform interface.

8. A combustible gas monitoring system for wells, used to execute the combustible gas monitoring method for wells as described in any one of claims 1-7, characterized in that, include: An optical system is used to emit laser signals into the well and receive reflected light signals after being absorbed by combustible gas inside the well. A diffuse reflector sheet is fixedly installed on the back of the manhole cover to enhance the reflected light signal; A data processing module, connected to the optical system, is used to process the reflected light signal; Temperature, humidity and pressure sensors are connected to the data processing module to collect temperature, humidity and pressure data inside the well. The optical system, diffuse reflector, and data processing module work together to improve monitoring accuracy by enhancing the optical signal and reducing noise.

9. A combustible gas monitoring system in a well as described in claim 8, characterized in that, The optical system includes a laser, a beam splitter, a filter, a photodetector, and a receiving mirror; The beam splitter divides the laser signal into a reference optical path and a measurement optical path. The reference optical path directly enters the photodetector, while the measurement optical path is absorbed by the combustible gas and then received by the receiving mirror, and the reflected signal is enhanced by the diffuse reflector.

10. A combustible gas monitoring system in a well as described in claim 8, characterized in that, The system also includes a 4G antenna for uploading and receiving data commands and a GPS antenna for calibrating the geographical location of the well.

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