Carbon dioxide concentration detection device and storage monitoring system based on optical fiber sensing

Abstract

The present invention provides a carbon dioxide concentration detection device and storage monitoring system based on optical fiber sensing. A modular first optical fiber sensing unit is designed so that the contact portion between the sensitive coating and the optical fiber Bragg grating can be independently maintained and replaced, and can accurately detect the wavelength drift of the optical fiber reflection caused by changes in the CO2 concentration in the environment. At the same time, the present invention provides an optical fiber Bragg grating not covered with a CO2 sensitive coating as a reference to detect wavelength drift mainly caused by environmental interference factors. By calculating the wavelength drift of the two optical fiber Bragg gratings and combining the mathematical model of the wavelength drift and CO2 concentration, the influence of environmental interference factors on the wavelength drift of the CO2 optical fiber sensor can be eliminated, thereby obtaining an accurate CO2 concentration value. The present invention realizes efficient real-time monitoring of CO2 concentration in the process of CO2 geological storage, ensuring that the data is accurate and reliable. In addition, the modular design facilitates regular inspection and replacement of the sensor, prolongs its service life, reduces maintenance costs, and has high sensitivity, strong stability and good maintainability.

Description

Technical Field

[0001] The present invention relates to the field of geological storage technology, and in particular to a carbon dioxide concentration detection device based on optical fiber sensing and a storage monitoring system. Background Art

[0002] With the continuous development of CO2 geological storage technology, real-time monitoring of CO2 concentration has become increasingly important. Existing methods for CO2 concentration monitoring include chemical sensors, electrochemical sensors, infrared absorption, and fiber optic sensing.

[0003] Chemical and electrochemical sensors are widely used in CO2 monitoring. These sensors typically detect changes in CO2 concentration through electrochemical or chemical reactions. However, these sensors often suffer from slow response, poor selectivity, susceptibility to aging, and complex maintenance. The infrared absorption method estimates CO2 concentration by measuring the absorption intensity of CO2 gas at specific wavelengths of infrared light. While this method offers good sensitivity, it requires a specific light source and a high-precision optical detector, resulting in high system costs. Furthermore, the operating environment must be free of strong light interference and have relatively stable temperature and humidity, otherwise measurement accuracy will be affected.

[0004] Fiber optic sensing technology, especially sensing technology based on fiber Bragg gratings or long-period gratings, has been widely used in recent years. Fiber optic sensors have advantages such as good resistance to electromagnetic interference, strong environmental resistance, high sensitivity, and fast response speed, and therefore have great application potential in CO2 concentration monitoring. Although fiber optic sensing technology has certain advantages in CO2 monitoring, existing technologies still face problems such as aging and maintenance of sensitive coatings, lack of modular design, and insufficient temperature stability. Although fiber optic sensing technology has shown high potential in CO2 concentration detection, due to the imperfect combination of fiber Bragg gratings or fiber Bragg gratings with CO2 sensitive coatings, and the lack of modular structure in existing designs, it is difficult to meet the needs of long-term, stable, and efficient monitoring. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a carbon dioxide concentration detection device and storage monitoring system based on optical fiber sensing, which is used to solve the technical problems in the prior art in CO2 concentration monitoring, such as slow response speed, poor selectivity, easy aging, complex maintenance, high cost, poor environmental adaptability, lack of modular design and insufficient temperature stability.

[0006] To achieve the above-mentioned and other related objectives, the present invention provides a device for detecting carbon dioxide concentration based on optical fiber sensing, the device comprising: a first optical fiber sensing unit, a second optical fiber sensing unit, a light source unit, a data acquisition unit, and a data processing unit; wherein the first optical fiber sensing unit adopts a modular design and comprises: a fiber Bragg grating and a CO2-sensitive coating module; the CO2-sensitive coating module is mounted on the fiber Bragg grating so that the CO2-sensitive coating inside the module covers the fiber Bragg grating; the first optical fiber sensing unit is configured to generate a wavelength shift through the fiber Bragg grating covered with the CO2-sensitive coating and reflect a corresponding light signal; the second optical fiber sensing unit comprises: a fiber Bragg grating not covered with the CO2-sensitive coating, a fiber Bragg grating disposed on the first optical fiber sensing unit; the second optical fiber sensing unit is configured to generate a wavelength drift through a fiber Bragg grating (FBG) not covered with a CO2 sensitive coating therein, and reflect a corresponding optical signal; the light source unit is configured to provide a stable excitation optical signal to the first optical fiber sensing unit and the second optical fiber sensing unit; the data acquisition unit is configured to receive optical signals respectively reflected by the fiber Bragg gratings in the first optical fiber sensing unit and the second optical fiber sensing unit, and extract wavelength drift information corresponding to the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit; the data processing unit is configured to calculate the wavelength drift amount based on the extracted wavelength drift information of the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit, and obtain the corresponding CO2 concentration based on the constructed mathematical model of the wavelength drift amount and the CO2 concentration.

[0007] In one embodiment of the present invention, the CO2-sensitive coating module is provided with a CO2-sensitive coating, a substrate providing support for the CO2-sensitive coating, and a protective shell; wherein the surface of the substrate is coated with the CO2-sensitive coating and allows CO2 gas to penetrate into the CO2-sensitive coating; the protective shell is used to prevent the external environment from damaging the first optical fiber sensing unit; by mounting the CO2-sensitive coating module on the fiber Bragg grating of the first optical fiber sensing unit and bringing the surface of the substrate coated with the CO2-sensitive coating into close contact with the corresponding optical fiber surface, when CO2 gas penetrates into the CO2-sensitive coating, it reacts with the CO2-sensitive coating, causing the physical properties of the CO2-sensitive coating to change, thereby causing the reflection wavelength of the fiber Bragg grating to drift.

[0008] In one embodiment of the present invention, a fixing structure is provided on the protective shell for detachably mounting the CO2 sensitive coating module on the fiber Bragg grating; wherein the fixing structure includes: one or more structures of a mechanical interlocking structure, an elastic clamping mechanism, and a magnetic coupling structure.

[0009] In one embodiment of the present invention, the light source unit includes: a light source for providing a stable excitation light signal through a broadband spontaneous radiation light source or a supercontinuum light source; a temperature control system connected to the light source, for monitoring the temperature of the light source in real time, and automatically adjusting the temperature through a semiconductor refrigeration plate to provide a stable excitation light signal.

[0010] In one embodiment of the present invention, the data acquisition unit includes: a signal receiving module, configured to receive, through a spectrometer or an optical detector, optical signals respectively reflected by the fiber Bragg gratings in the first and second optical fiber sensing units, and convert them into electrical signals respectively; a signal processing module, connected to the signal receiving module, configured to amplify, through a low-noise amplifier, the electrical signals converted from the optical signals reflected by the fiber Bragg gratings in the first and second optical fiber sensing units, and perform filtering and demodulation on the amplified electrical signals to extract wavelength drift information corresponding to the optical signals reflected by the first and second optical fiber sensing units; a storage module, connected to the signal processing module, configured to store the wavelength drift information extracted by the signal processing module; and a position determination module, connected to the signal receiving module, configured to identify the position of the light source from which the received optical signal comes.

[0011] In one embodiment of the present invention, the data processing unit includes: a wavelength drift acquisition module, which is used to obtain the center wavelength of the corresponding reflection spectrum using a high-speed sampling and frequency analysis algorithm based on the wavelength drift information of the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit, and calculate the wavelength drift of the first optical fiber sensing unit and the second optical fiber sensing unit; a CO2 concentration calculation module, connected to the wavelength drift acquisition module, which is used to obtain the corresponding CO2 concentration based on the wavelength drift of the first optical fiber sensing unit and the second optical fiber sensing unit based on a constructed mathematical model of wavelength drift and CO2 concentration.

[0012] In one embodiment of the present invention, the method for constructing the mathematical model of the wavelength drift and CO2 concentration includes: receiving light signals reflected by the fiber Bragg gratings of the first fiber optic sensing unit and the second fiber optic sensing unit under a standard gas environment with different CO2 concentrations, and calculating the wavelength drifts corresponding to the first fiber optic sensing unit and the second fiber optic sensing unit under different CO2 concentrations; and training based on the wavelength drifts corresponding to the first fiber optic sensing unit and the second fiber optic sensing unit under each CO2 concentration to obtain the mathematical model of the wavelength drift and CO2 concentration.

[0013] In one embodiment of the present invention, the mathematical model of wavelength drift and CO2 concentration includes: a decoupling module for separating the effects of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first optical fiber sensing unit based on the input wavelength drift of the corresponding second optical fiber sensing unit, so as to extract the wavelength drift primarily related to the CO2 concentration from the wavelength drift of the corresponding first optical fiber sensing unit; and a CO2 concentration detection module, connected to the decoupling module, for calculating the corresponding CO2 concentration based on the wavelength drift primarily related to the CO2 concentration based on a constructed calibration curve between wavelength drift and CO2 concentration.

[0014] In one embodiment of the present invention, the data processing unit also includes: an automatic calibration module, which is used to regularly use data from standard gases with different CO2 concentrations to calibrate the mathematical model of the wavelength drift and CO2 concentration; a remote data transmission module, which is used to upload the obtained CO2 concentration to a remote monitoring platform; an anomaly detection module, which is used to perform an anomaly analysis on the wavelength drift data, automatically identify possible fault conditions, and trigger an alarm signal; and a visual display module, which is used to display the CO2 concentration change curve in real time through a graphical interface and provide historical data query and analysis functions.

[0015] To achieve the above-mentioned and other related purposes, the present invention provides a carbon dioxide geological storage monitoring system, which includes: the above-mentioned carbon dioxide concentration detection device based on optical fiber sensing.

[0016] As described above, the present invention is a carbon dioxide concentration detection device and storage monitoring system based on fiber optic sensing, which has the following beneficial effects: The present invention designs a modular first fiber optic sensing unit, allowing the contact portion between the sensitive coating and the fiber Bragg grating (FBG) to be independently maintained and replaced, enabling accurate detection of fiber reflection wavelength drift caused by changes in environmental CO2 concentration. Furthermore, the present invention incorporates a fiber Bragg grating (FBG) uncovered with the CO2-sensitive coating as a reference to detect wavelength drift primarily caused by environmental interference. By calculating the wavelength drift of the two FBGs and combining a mathematical model that correlates wavelength drift with CO2 concentration, the effects of environmental interference on the wavelength drift of the CO2 fiber sensor can be eliminated, thereby obtaining an accurate CO2 concentration value. This invention enables efficient, real-time monitoring of CO2 concentration during CO2 geological storage, ensuring accurate and reliable data. Furthermore, the modular design facilitates regular inspection and replacement of the sensor, extending its service life and reducing maintenance costs. The system exhibits high sensitivity, strong stability, and excellent maintainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a structural schematic diagram of a carbon dioxide concentration detection device based on optical fiber sensing in one embodiment of the present invention.

[0018] Figure 2 FIG. 1 is a schematic structural diagram of a first optical fiber sensing unit according to an embodiment of the present invention.

[0019] Figure 3 Shown is a structural schematic diagram of a carbon dioxide concentration detection device based on optical fiber sensing in one embodiment of the present invention.

[0020] Figure 4 Shown is a structural schematic diagram of a CO2 geological storage monitoring system in one embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0022] It should be noted that in the following description, reference is made to the accompanying drawings, which describe several embodiments of the present invention. It should be understood that other embodiments may also be used, and that mechanical, structural, electrical, and operational changes may be made without departing from the spirit and scope of the present invention. The following detailed description should not be considered restrictive, and the scope of the embodiments of the present invention is limited only by the claims of the published patents. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Spatially related terms, such as "upper", "lower", "left", "right", "below", "below", "lower", "above", "upper", etc., may be used in the text to facilitate the description of the relationship between one element or feature shown in the figure and another element or feature.

[0023] Throughout this specification, when a part is said to be "connected" to another part, this includes not only "direct connection" but also "indirect connection" with other elements interposed therebetween. Furthermore, when a part is said to "include" a certain component, unless otherwise stated, this does not exclude the inclusion of such other components but rather implies that the part may include such other components.

[0024] The terms "first," "second," and "third" are used to describe various parts, components, regions, layers, and / or segments, but are not intended to be limiting. These terms are used solely to distinguish one part, component, region, layer, or segment from another. Therefore, a reference to a first part, component, region, layer, or segment below may also refer to a second part, component, region, layer, or segment without departing from the scope of the present invention.

[0025] Furthermore, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms "comprise", "include" indicate the presence of the described features, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B, and C". Exceptions to this definition occur only when the combination of elements, functions, or operations is inherently mutually exclusive in some way.

[0026] The present invention provides a device for detecting carbon dioxide concentration based on optical fiber sensing. A first optical fiber sensing unit with a modular structure is designed so that the contact portion between the sensitive coating and the optical fiber Bragg grating can be independently maintained and replaced, and can accurately detect the wavelength drift of the optical fiber reflection caused by changes in the CO2 concentration in the environment. At the same time, the present invention provides an optical fiber Bragg grating not covered with a CO2 sensitive coating as a reference to detect wavelength drift mainly caused by environmental interference factors. By calculating the wavelength drift of the two optical fiber Bragg gratings and combining a mathematical model of the wavelength drift and CO2 concentration, the influence of environmental interference factors on the wavelength drift of the CO2 optical fiber sensor can be eliminated, thereby obtaining an accurate CO2 concentration value. The present invention realizes efficient real-time monitoring of CO2 concentration during the CO2 geological storage process, ensuring accurate and reliable data. In addition, the modular design facilitates regular inspection and replacement of the sensor, prolongs its service life, reduces maintenance costs, and has high sensitivity, strong stability, and good maintainability.

[0027] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0028] like Figure 1 A schematic structural diagram of a carbon dioxide concentration detection device based on optical fiber sensing in an embodiment of the present invention is shown.

[0029] The system comprises: a first optical fiber sensing unit 1, a second optical fiber sensing unit 2, a light source unit 3, a data acquisition unit 4 and a data processing unit 5;

[0030] The first fiber optic sensing unit 1 is specifically designed to detect changes in CO2 concentration in the environment. Its core component is a fiber Bragg grating (FBG) covered with a CO2-sensitive coating. This unit reflects changes in CO2 concentration through wavelength shifts generated by the FBG and reflects the corresponding optical signal for subsequent analysis. To improve the sensor's maintainability and extend its service life, the first fiber optic sensing unit 1 is designed with a modular structure. This design mainly includes two key components:

[0031] FBG is a technology that achieves sensing by introducing periodic refractive index changes in optical fibers. Its working principle is based on the reflection of light of specific wavelengths by the grating. When light passes through the FBG, only light of specific wavelengths is reflected back.

[0032] The CO2-sensitive coating module is a structure specifically designed to work with the FBG sensing area. It contains a CO2-sensitive coating. Once installed on the FBG, the coating covers the FBG surface. When the CO2 concentration in the environment changes, the sensitive coating responds to the CO2, causing a change in the coating's refractive index or volume.

[0033] When CO2 concentration changes, the refractive index or volume change of the sensitive coating directly affects the FBG's reflection characteristics. This change manifests as a shift in the FBG's reflection wavelength—the wavelength of the reflected light shifts with the CO2 concentration. By monitoring this shift in reflection wavelength, the CO2 concentration in the environment can be calculated.

[0034] Because optical fiber wavelength drift is easily affected by both temperature and pressure, it can severely impact the accuracy of CO2 concentration detection. To address this issue, a second optical fiber sensing unit 2 is provided. This second optical fiber sensing unit 2 comprises a fiber Bragg grating (FBG) without a CO2-sensitive coating. This FBG is positioned around the fiber Bragg grating of the first optical fiber sensing unit. The second optical fiber sensing unit 2 utilizes the FBG within it, which is not coated with a CO2-sensitive coating, to generate wavelength drift and reflect the corresponding optical signal. Because this grating is not coated with a CO2-sensitive coating, it is insensitive to changes in ambient CO2 concentration. However, it responds to changes in temperature and pressure, causing the reflected wavelength to drift. The second optical fiber sensing unit 2 serves as a reference sensing unit, unaffected by CO2 concentration but subject to the same temperature and pressure variations as the first optical fiber sensing unit 1. Thus, the wavelength drift of the FBG in the second optical fiber sensing unit 2 primarily reflects changes in temperature and pressure.

[0035] The light source unit 3 is used to provide a stable excitation light signal to the first optical fiber sensing unit 1 and the second optical fiber sensing unit 2 to ensure that the two optical fiber sensing units can accurately monitor wavelength drift.

[0036] The data acquisition unit 4 is configured to receive optical signals reflected by the fiber Bragg gratings in the first optical fiber sensing unit 1 and the second optical fiber sensing unit 2, respectively, and extract wavelength drift information corresponding to the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit;

[0037] The data processing unit 5 is used to calculate the wavelength drift amount based on the extracted wavelength drift information of the optical signals reflected by the first optical fiber sensing unit 1 and the second optical fiber sensing unit 2, and obtain the corresponding CO2 concentration based on the constructed mathematical model of wavelength drift amount and CO2 concentration.

[0038] This solution simultaneously collects wavelength drift data from both the first fiber optic sensing unit (1) (for detecting CO2 concentration) and the second fiber optic sensing unit (2) (for monitoring temperature and pressure), and performs in-depth analysis and processing on this data. This allows for precise isolation of the effects of temperature and pressure on the wavelength drift of the CO2 fiber optic sensor. This results in more accurate and reliable CO2 concentration results, effectively improving the CO2 concentration monitoring system's anti-interference capabilities and measurement accuracy.

[0039] In one embodiment, the CO2 sensitive coating module includes: a substrate, a CO2 sensitive coating, and a protective shell;

[0040] The substrate provides stable support for the CO2-sensitive coating while allowing CO2 gas to penetrate the coating. The substrate is made of flexible, gas-permeable polymers such as polydimethylsiloxane (PDMS) and polyimide, or microporous materials. These materials not only provide excellent support but also ensure rapid CO2 gas penetration into the sensitive coating, improving detection response speed.

[0041] The CO2-sensitive coating is evenly coated on the surface of the substrate. Coating methods can include spraying, spin coating, or dip coating to ensure uniform coating thickness. The CO2-sensitive coating uses highly selective CO2-responsive materials, such as metal-organic frameworks, functionalized polymers, or nanocomposites. These materials will undergo volume expansion or refractive index changes during CO2 adsorption or desorption, thereby affecting the spectral response of the fiber Bragg grating. The coating thickness is optimized to ensure a balance between sensitivity and response time. When CO2 gas penetrates the coating, it reacts with the coating, causing changes in the physical properties of the coating (such as volume and refractive index), which in turn causes the reflection wavelength of the fiber Bragg grating to drift.

[0042] The protective housing 103 prevents the external environment from damaging the first optical fiber sensing unit 1. The housing made of breathable material can protect the sensor unit while allowing CO2 gas to penetrate into the sensitive coating without affecting the normal operation of the sensor.

[0043] In a preferred embodiment, if Figure 2 A cylindrical accommodating space is formed in the middle of the CO2 sensitive coating module, and the accommodating space is used to place the optical fiber 100.

[0044] The substrate 101 is composed of two connected semi-annular structures, each with a roughly semicircular cross-section. When the two semi-annular structures are joined at both ends, they together form a hollow cylindrical space. This space is specifically designed to accommodate optical fibers, reflecting the precision and efficiency of the structural design. The inner diameter of the substrate is precisely designed based on the diameter of the optical fiber used, typically slightly larger by 0.1-0.3mm. This size design is intended to ensure that the optical fiber 100 can be easily placed therein while retaining a certain amount of room for movement to avoid weakening the close contact between the CO2-sensitive coating 102 and the optical fiber 100 due to an excessively large gap.

[0045] The protective shell 103 as a whole has a hollow cylindrical structure and is tightly connected to the substrate. The cylindrical inner surface formed by it matches the inner surface of the substrate 101. It is worth noting that the protective shell 103 is not formed in one piece, but consists of two structures. This split design has significant advantages, which greatly facilitates the installation and disassembly process of the sensor. One side of the protective shell 103 is connected by a specific connecting component, which can be a flexible plastic sheet, an elastic rubber strip or a hinge structure with a certain strength. The other side of the protective shell 103 is carefully designed with a fixing structure. Common fixing structures include snap buckles, magnetic devices, etc. This fixed structure design makes it possible to operate the protective shell 103 conveniently and quickly when installing and disassembling the sensor, thereby significantly improving work efficiency.

[0046] During the installation process, the optical fiber 100 is first placed in the accommodation space of the substrate 101. After the optical fiber 100 is in place, the two semi-annular substrates are merged and firmly fixed together using the fixing structure on the protective shell 103. At this time, the internal CO2 sensitive coating 102 will tightly wrap the surface of the optical fiber, thereby constructing a stable and reliable detection environment. During disassembly, it is only necessary to operate the fixing structure on the other side of the protective shell 103 to separate the two structures of the protective shell 103. As the two structures of the protective shell 103 separate, the substrate 101 originally wrapped by the shell is also exposed, and then the two semi-annular substrates can be separated to remove the optical fiber 100 from the accommodation space.

[0047] In one embodiment, the protective housing 103 is provided with a fixing structure for removably mounting the CO2-sensitive coating module on the fiber Bragg grating (FBG), facilitating maintenance and replacement. This fixing structure can be one or more of a mechanical interlocking structure, an elastic clamping mechanism, or a magnetic coupling structure. Mechanical interlocking structures include various types, such as snap-on and slot-type, cam-locking, wedge-block interlocking, and tongue-and-groove interlocking. Elastic clamping mechanisms include spring clips and rubber elastic clamping. Magnetic coupling structures include magnet-iron adsorption, magnetic ring coupling, magnetic snap-on, and magnetic slide rail types. For example, Figure 2 illustrates a snap-on structure. The snap 104 on one side of the protective housing securely secures the CO2-sensitive coating module to the fiber Bragg grating (FBG).

[0048] In one embodiment, each CO2 sensitive coating module corresponds to a type of CO2 sensitive coating. In practical applications, to meet the requirements of accurate measurement under different environmental conditions, CO2 sensitive coating modules with different types of CO2 sensitive coatings can be flexibly replaced in the first optical fiber sensing unit. Specifically, CO2 sensitive coatings are available in multiple types to adapt to diverse detection scenarios:

[0049] High-sensitivity coating: Used in trace detection scenarios of low-concentration CO2, it has extremely high sensitivity and can accurately capture changes in extremely low concentrations of CO2 in the environment. It provides reliable data support for application scenarios with extremely high requirements for CO2 concentration accuracy, such as laboratory precision research and environmental micro-pollution monitoring.

[0050] High-temperature-resistant coating: Considering the special requirements for CO2 concentration detection in high-temperature environments, a high-temperature-resistant coating is used in high-temperature environments. It can maintain stable chemical and physical properties under high-temperature conditions, ensuring accurate CO2 concentration measurement in high-temperature environments. It is suitable for gas monitoring in high-temperature environments such as industrial high-temperature furnaces and aerospace.

[0051] Fast Response Coating: When rapid monitoring of gas concentration changes is required, use a fast response coating. It reacts quickly and provides immediate feedback on CO2 concentration fluctuations.

[0052] In one embodiment, if Figure 3 , the light source unit 3 includes:

[0053] A light source is used to provide a stable excitation light signal through a broadband spontaneous emission (ASE) or supercontinuum (SCS) source. Specifically, ASE sources are based on stimulated and spontaneous emission processes in doped optical fibers (such as erbium-doped fibers). Using an ASE source provides a broadband, low-noise optical signal with high spectral flatness, ensuring that the fiber Bragg grating is uniformly excited across its operating range. For applications with higher sensitivity, an SCS light source can be used. An SCS light source typically injects high-power pulsed laser light into a nonlinear optical fiber, leveraging the fiber's nonlinear effects to broaden the input narrowband pulsed laser light into an ultra-broadband continuous spectrum. The spectrum of an SCS light source can cover multiple wavelengths, from the visible to the near-infrared and even the mid-infrared, far exceeding the spectral range of an ASE light source. SCS light sources have a high optical power density and can maintain high signal strength over long transmission distances, making them suitable for long-distance fiber-optic sensing systems.

[0054] Because the wavelength stability of the light source is significantly affected by temperature, to ensure the stability and consistency of the light source signal, the light source unit 3 is equipped with a high-precision temperature control system. This temperature control system, connected to the light source, uses a high-precision temperature sensor to monitor the light source's temperature in real time and automatically adjusts the temperature via a semiconductor cooler to provide a stable excitation light signal. This system prevents the impact of ambient temperature changes on the light source's output wavelength and power, thereby maintaining the stability of the light signal and ensuring signal reliability during long-term monitoring.

[0055] In one embodiment, if Figure 3 , the data acquisition unit 4 includes:

[0056] The signal receiving module is primarily responsible for receiving the optical signals reflected by the fiber Bragg gratings in the first and second fiber optic sensing units 1 and 2 through a spectrometer or optical detector and converting them into electrical signals. Specifically, since the optical signals are analog, they require the use of a spectrometer or optical detector to convert them into electrical signals (such as voltage or current).

[0057] The signal processing module is connected to the signal receiving module and is mainly responsible for processing the electrical signal. It first uses a low-noise amplifier to amplify the electrical signal converted from the optical signal reflected by the fiber Bragg grating in the first optical fiber sensing unit 1 and the second optical fiber sensing unit 2. This amplification process is crucial, especially when the signal strength is low, to ensure the accurate extraction of wavelength information. Subsequently, the module will filter and demodulate the amplified electrical signal. Specifically, digital filtering technology, such as Kalman filtering and adaptive noise suppression algorithm, is used to remove environmental noise, thereby improving signal quality and accurately extracting the wavelength drift information corresponding to the optical signal reflected by the first optical fiber sensing unit and the second optical fiber sensing unit.

[0058] The storage module is connected to the signal processing module and is mainly used to locally store the wavelength drift information extracted by the signal processing module. This stored information provides a basis for subsequent data analysis and monitoring.

[0059] The position determination module, connected to the signal receiving module, has the core function of determining the location of the light source corresponding to the received light signal. Specifically, it identifies the distance from which the light signal originates. This function accurately determines the source of the light signal, providing precise spatial positioning information for subsequent monitoring and analysis, helping to better understand the distribution of CO2 concentration changes at different locations.

[0060] In one embodiment, if Figure 3 , the data processing unit 5 includes:

[0061] The wavelength drift acquisition module is used to determine the center wavelength of the corresponding reflection spectrum based on the wavelength drift information of the optical signals reflected by the first and second optical fiber sensing units 1 and 2 using high-speed sampling and frequency analysis algorithms. This module then calculates the wavelength drift of the corresponding optical signals. Specifically, in an optical fiber sensing system, the optical signal reflected by the fiber optic bridge (FBG) is a continuously varying analog signal. High-speed sampling enables the acquisition of discrete temporal data points. The sampled digital signal is then subjected to Fourier transform or matched filtering to accurately determine the center wavelength of the reflection spectrum, thereby calculating the wavelength drift. For the Fourier transform method, Fourier transforming the sampled digital signal converts the signal from the time domain to the frequency domain, yielding the signal's spectral distribution. In the spectrum, the center wavelength of the FBG-reflected light corresponds to a specific frequency peak. By detecting the location of this peak, the center position of the reflected wavelength can be precisely determined. For the matched filtering method, the sampled digital signal is subjected to a matched filtering algorithm to locate the location with the highest degree of match with the reference signal, thereby determining the center position of the reflected wavelength. In a fiber optic sensing system, the theoretical waveform of the FBG reflected light can be known in advance and used as a reference signal. After obtaining the center position of the FBG reflected wavelength, it is compared with the initial center wavelength to calculate the corresponding wavelength drift.

[0062] The CO2 concentration calculation module is connected to the wavelength drift acquisition module and is used to obtain the corresponding CO2 concentration according to the wavelength drift of the first optical fiber sensing unit and the second optical fiber sensing unit based on a mathematical model of wavelength drift and CO2 concentration constructed by regression analysis or machine learning algorithm.

[0063] In one embodiment, the mathematical model of the wavelength shift and CO2 concentration is constructed by:

[0064] CO2 of varying concentrations is mixed with other gases (such as nitrogen or air) to prepare a series of standard gases with varying CO2 concentrations. This step is fundamental to ensuring the accuracy and reliability of experimental data, as the accuracy of the standard gas concentration directly affects the accuracy of the subsequent relationship between wavelength shift and CO2 concentration. Flow controllers precisely adjust the flow rates of various gases to achieve accurate control of CO2 concentration.

[0065] Light emitted by a light source is transmitted via optical fibers to the fiber Bragg gratings (FBGs) in the first and second fiber optic sensing units 1 and 2. FBGs reflect light of specific wavelengths. The reflected light signals from the FBGs are used to calculate the wavelength shifts of the first and second fiber optic sensing units 1 and 2 at different CO2 concentrations. The specific calculation method is similar to that described in the previous embodiment and is not detailed here.

[0066] The wavelength drift of the two units corresponding to different carbon dioxide concentrations is used as data samples, and the relationship between them is fitted through an algorithm, so that the model can accurately calculate the carbon dioxide concentration based on the drift.

[0067] Specifically, a relationship between temperature, pressure, and wavelength drift is established based on the wavelength drift of the first and second optical fiber sensing units 1 and 2 at different CO2 concentrations to construct a decoupling module. This decoupling module can extract the effective drift primarily related to CO2 concentration based on the input wavelength drift of the first and second optical fiber sensing units 1 and 2. The wavelength drift primarily related to CO2 concentration output by the decoupling module is paired with standard CO2 concentration data and used as a sample. Using regression analysis or a machine learning algorithm, the sample data is fitted to generate a calibration curve that accurately reflects the corresponding relationship between the two. This constructs a CO2 concentration detection module that can quickly calculate the corresponding CO2 concentration value based on the input wavelength drift primarily related to CO2 concentration.

[0068] After building a mathematical model, it needs to be validated and optimized. This can be done using an independent test dataset to calculate the model's prediction error and assess its accuracy and reliability. If the model's prediction error is large, adjustments and optimizations may be necessary, such as changing the mathematical model's form or increasing its complexity, until the model's prediction error meets the required level.

[0069] In one embodiment, the mathematical model of the wavelength shift and CO2 concentration includes:

[0070] a decoupling module for separating the effects of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first optical fiber sensing unit based on the input wavelength drift of the second optical fiber sensing unit, so as to extract the wavelength drift mainly related to the CO2 concentration from the wavelength drift of the first optical fiber sensing unit;

[0071] The CO2 concentration detection module is connected to the decoupling module and is used to calculate the corresponding CO2 concentration based on the wavelength drift amount mainly related to the CO2 concentration based on the calibration curve between the wavelength drift and the CO2 concentration.

[0072] In one embodiment, if Figure 3 , the data processing unit further includes:

[0073] The automatic calibration module features automatic periodic calibration. It uses standard gas data with varying CO2 concentrations to calibrate the mathematical model linking wavelength drift and CO2 concentration at preset intervals or under specific trigger conditions. In practical applications, detection devices can age over time. Furthermore, changes in environmental conditions (such as fluctuations in temperature, humidity, and pressure) can also affect their performance, leading to measurement errors. By incorporating standard gas data and dynamically adjusting the mathematical model, the automatic calibration module effectively eliminates errors introduced by these factors, ensuring the accuracy and stability of the model.

[0074] The remote data transmission module is responsible for uploading CO2 concentration data obtained by the data processing unit to the remote monitoring platform. It supports multiple communication protocols and network connection methods, such as Ethernet, Wi-Fi, and 4G / 5G, ensuring stable and reliable data transmission to the remote end. Through remote data transmission, users can obtain real-time CO2 concentration data from anywhere with an internet connection, enabling remote management of the detection system. The remote monitoring platform not only provides real-time data reception but also offers powerful data storage and management capabilities. The platform categorizes and stores uploaded CO2 concentration data and establishes a corresponding database. Users can query, compile, and analyze historical data as needed, providing data support for decision-making in areas such as environmental monitoring and industrial production. The platform also features data backup and recovery capabilities to ensure data security and integrity.

[0075] The anomaly detection module monitors and analyzes wavelength drift data in real time. It employs a variety of anomaly detection algorithms, such as statistically based threshold judgment and machine learning-based pattern recognition, to conduct in-depth research on the distribution patterns and trends of wavelength drift data. When wavelength drift data is detected to be outside the normal range or exhibiting abnormal fluctuations, the module automatically identifies a possible fault condition. Once a fault condition is identified, the anomaly detection module immediately triggers an alarm signal. This alarm signal can be sent to relevant personnel via various means, such as text messages, emails, and audible and visual alarms, ensuring that users are promptly informed of system anomalies. The module also records information such as the time, location, and type of anomaly, providing a basis for troubleshooting and repair.

[0076] The visualization module displays a real-time CO2 concentration curve through a graphical interface. Users can intuitively see how CO2 concentration changes over time and understand the dynamics of CO2 concentration in the environment. The interface is simple and easy to use, and users can adjust the displayed time range and data accuracy as needed. In addition to real-time display, the module also provides historical data query and analysis capabilities. Users can query historical CO2 concentration data by entering specific time ranges, locations, and other conditions. The module also supports statistical analysis of historical data, such as calculating averages, maximums, and minimums, and generates corresponding reports and charts, providing users with more in-depth data analysis results.

[0077] like Figure 4 A structural schematic diagram of a carbon dioxide geological storage monitoring system according to an embodiment of the present invention is shown.

[0078] The carbon dioxide geological storage monitoring system includes: the carbon dioxide concentration detection device based on optical fiber sensing described in the above embodiment, so it will not be described in detail here. The carbon dioxide concentration detection device based on optical fiber sensing is suitable for monitoring CO2 geological storage sites, and can operate stably in extreme environments such as high pressure, high humidity and corrosiveness. By relying on multi-point distributed sensing technology, it can achieve real-time and all-round monitoring of the CO2 concentration in the storage area. The system can also be set up in combination with other environmental monitoring equipment, such as temperature, pressure, and earthquake monitoring equipment, and use the collection of multiple detection data for comprehensive analysis. This not only effectively improves the reliability and accuracy of the data, but also can accurately assess the safety of the storage environment.

[0079] Compared with the prior art, the present invention has the following advantages:

[0080] 1. High sensitivity and accuracy

[0081] This invention combines a fiber Bragg grating (FBG) with a CO2-sensitive coating to accurately monitor wavelength drift caused by changes in CO2 concentration in the environment. The sensitive coating produces significant changes in refractive index or volume when CO2 concentration changes. Combined with the high sensitivity of the fiber Bragg grating (FBG), this method can generate stable and accurate monitoring signals even with minimal concentration changes, significantly improving detection accuracy and reliability.

[0082] 2. Modular design, easy to maintain

[0083] The first optical fiber sensing unit of the present invention adopts a modular structural design, so that the contact part between the sensitive coating and the optical fiber can be independently maintained and replaced, which facilitates regular inspection and replacement of the sensor, extends the service life of the sensor, and reduces maintenance costs.

[0084] 3. Temperature control system ensures light source stability

[0085] The light source unit of the present invention adopts a high-precision temperature control system to monitor and adjust the temperature of the light source in real time, avoiding the influence of ambient temperature changes on the output wavelength and power of the light source, ensuring the stability and consistency of the light source, and thus ensuring the reliability of the signal of the system during long-term monitoring.

[0086] 4. Real-time data collection and analysis

[0087] The data acquisition unit of the present invention can capture changes in the reflected spectrum of the optical fiber sensing unit in real time and accurately obtain wavelength drift information through high-speed sampling and sophisticated frequency analysis algorithms. The data acquisition unit also has noise filtering and calibration functions to ensure data stability and accuracy during long-term operation.

[0088] 5. Efficient data processing and accurate calculation

[0089] The data processing unit utilizes advanced signal processing techniques, such as high-pass and low-pass filtering, and Kalman filtering, to remove noise and ensure input signal quality. Quantitative analysis using linear or nonlinear regression models, combined with calibration data, ultimately calculates accurate CO2 concentrations. Regular system calibration ensures continued high accuracy, preventing errors caused by environmental changes or sensor aging.

[0090] In summary, the fiber-optic sensing-based carbon dioxide concentration detection device and storage monitoring system of the present invention features a modular first fiber-optic sensing unit, allowing the contact area between the sensitive coating and the fiber Bragg grating (FBG) to be independently maintained and replaced. This allows for accurate detection of wavelength drift in the optical fiber reflection caused by changes in CO2 concentration in the environment. Furthermore, the present invention incorporates a fiber Bragg grating (FBG) uncovered with the CO2-sensitive coating as a reference to detect wavelength drift primarily caused by environmental interference. By calculating the wavelength drift of the two FBGs and combining this with a mathematical model that correlates wavelength drift with CO2 concentration, the effects of environmental interference on the wavelength drift of the CO2 fiber sensor can be eliminated, thereby obtaining an accurate CO2 concentration value. This invention enables efficient, real-time monitoring of CO2 concentration during CO2 geological storage, ensuring accurate and reliable data. Furthermore, the modular design facilitates regular inspection and replacement of the sensor, extending its service life and reducing maintenance costs. The system exhibits high sensitivity, strong stability, and excellent maintainability. Therefore, the present invention effectively overcomes the shortcomings of the prior art and possesses high industrial value.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, any equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A carbon dioxide concentration detection device based on optical fiber sensing, characterized in that: The device comprises: a first optical fiber sensing unit, a second optical fiber sensing unit, a light source unit, a data acquisition unit and a data processing unit; wherein, The first optical fiber sensing unit adopts a modular design and includes: a fiber Bragg grating and a CO2-sensitive coating module; the CO2-sensitive coating module is mounted on the fiber Bragg grating so that the CO2-sensitive coating inside the module covers the fiber Bragg grating; the first optical fiber sensing unit is configured to generate a wavelength shift through the fiber Bragg grating covered with the CO2-sensitive coating and reflect a corresponding optical signal; The second optical fiber sensing unit comprises: a fiber Bragg grating not covered with a CO2 sensitive coating, arranged around the fiber Bragg grating of the first optical fiber sensing unit; the second optical fiber sensing unit is configured to generate a wavelength shift through the fiber Bragg grating not covered with a CO2 sensitive coating therein and reflect a corresponding optical signal; The light source unit is configured to provide a stable excitation light signal to the first optical fiber sensing unit and the second optical fiber sensing unit; The data acquisition unit is configured to receive optical signals reflected by the fiber Bragg gratings in the first optical fiber sensing unit and the second optical fiber sensing unit, respectively, and extract wavelength drift information corresponding to the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit; The data processing unit is configured to calculate the wavelength drift amount based on the extracted wavelength drift information of the optical signals reflected by the first optical fiber sensing unit and the second optical fiber sensing unit, and obtain the corresponding CO2 concentration based on the constructed mathematical model of the wavelength drift amount and CO2 concentration; The CO2 sensitive coating module is provided with a CO2 sensitive coating, a substrate providing support for the CO2 sensitive coating, and a protective shell; The surface of the substrate is coated with a CO2 sensitive coating, and CO2 gas is allowed to penetrate into the CO2 sensitive coating; the protective housing is used to prevent the external environment from damaging the first optical fiber sensing unit; The CO2 sensitive coating module is mounted on the fiber Bragg grating of the first optical fiber sensing unit and the surface of the substrate coated with the CO2 sensitive coating is in close contact with the surface of the corresponding optical fiber, so that when CO2 gas penetrates into the CO2 sensitive coating, it reacts with the CO2 sensitive coating, causing the physical properties of the CO2 sensitive coating to change, thereby causing the reflection wavelength of the fiber Bragg grating to drift; The substrate is composed of two connected semi-annular structures, each of which has a cross-section approximately semicircular. When the two semi-annular structures are combined at both ends, they together form a hollow cylindrical space, which accommodates the optical fiber. The protective shell has a hollow cylindrical structure as a whole and is closely connected to the substrate; a fixing structure is provided on the protective shell for detachably mounting the CO2 sensitive coating module on the fiber Bragg grating; After the optical fiber is placed in place, the two semi-annular substrates are merged and firmly fixed together using the fixing structure on the protective shell. At this time, the internal CO2 sensitive coating will tightly wrap the surface of the optical fiber.

2. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that: The fixing structure includes: one or more structures of a mechanical interlocking structure, an elastic clamping mechanism, and a magnetic coupling structure.

3. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that: The light source unit includes: A light source, used for providing a stable excitation light signal through a broadband spontaneous emission light source or a supercontinuum light source; The temperature control system is connected to the light source and is used to monitor the temperature of the light source in real time and automatically adjust the temperature through semiconductor cooling chips so that the light source provides a stable excitation light signal.

4. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that: The data acquisition unit includes: a signal receiving module, configured to receive, through a spectrometer or an optical detector, optical signals respectively reflected by the fiber Bragg gratings in the first optical fiber sensing unit and the second optical fiber sensing unit, and convert them into electrical signals respectively; a signal processing module, connected to the signal receiving module, configured to amplify, through a low-noise amplifier, electrical signals converted from optical signals reflected by the fiber Bragg gratings in the first and second optical fiber sensing units, and perform filtering and demodulation on the amplified electrical signals to extract wavelength drift information corresponding to the optical signals reflected by the first and second optical fiber sensing units; a storage module, connected to the signal processing module, and configured to store the wavelength drift information extracted by the signal processing module; The position determination module is connected to the signal receiving module and is used to identify the position of the light source from which the received light signal comes.

5. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that: The data processing unit includes: a wavelength drift acquisition module, configured to obtain the center wavelength of the corresponding reflection spectrum based on the wavelength drift information of the optical signals reflected by the first and second optical fiber sensing units using a high-speed sampling and frequency analysis algorithm, and calculate the wavelength drift amounts of the first and second optical fiber sensing units; The CO2 concentration calculation module is connected to the wavelength drift acquisition module and is used to obtain the corresponding CO2 concentration according to the wavelength drift of the first optical fiber sensing unit and the second optical fiber sensing unit based on the constructed mathematical model of wavelength drift and CO2 concentration.

6. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 5, characterized in that: The mathematical model of the wavelength drift and CO2 concentration is constructed in the following manner: receiving optical signals reflected by the fiber Bragg gratings of the first optical fiber sensing unit and the second optical fiber sensing unit under standard gas environments with different CO2 concentrations, and calculating the wavelength drifts corresponding to the first optical fiber sensing unit and the second optical fiber sensing unit under different CO2 concentrations; The mathematical model of the wavelength drift and CO2 concentration is obtained based on the wavelength drift corresponding to the first optical fiber sensing unit and the second optical fiber sensing unit at each CO2 concentration.

7. The device for detecting carbon dioxide concentration based on optical fiber sensing according to claim 6, characterized in that: The mathematical model of the wavelength drift and CO2 concentration includes: a decoupling module for separating the effects of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first optical fiber sensing unit based on the input wavelength drift of the second optical fiber sensing unit, so as to extract the wavelength drift mainly related to the CO2 concentration from the wavelength drift of the first optical fiber sensing unit; The CO2 concentration detection module is connected to the decoupling module and is used to calculate the corresponding CO2 concentration based on the wavelength drift amount mainly related to the CO2 concentration based on the calibration curve between the wavelength drift and the CO2 concentration.

8. The device for detecting carbon dioxide concentration based on optical fiber sensing according to claim 5, characterized in that: The data processing unit further includes: An automatic calibration module, configured to periodically calibrate the mathematical model of the wavelength drift and CO2 concentration using data of standard gases with different CO2 concentrations; Remote data transmission module, used to upload the obtained CO2 concentration to the remote monitoring platform; Anomaly detection module, used to perform anomaly analysis on wavelength drift data, automatically identify possible fault conditions, and trigger an alarm signal; The visualization display module is used to display the CO2 concentration change curve in real time through a graphical interface and provide historical data query and analysis functions.

9. A carbon dioxide geological storage monitoring system, characterized in that: The system includes: a carbon dioxide concentration detection device based on optical fiber sensing according to any one of claims 1 to 8.

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