Non-contact detector and method for gas-liquid interface in salt caverns based on laser ranging

Abstract

This application discloses a non-contact detector and method for the gas-liquid interface in salt caverns based on laser ranging. It is used to perform real-time measurement of the gas-liquid interface while the wellhead remains sealed and closed. The method includes: an in-wellbore probe assembly, installed inside the wellbore and directly facing the gas-liquid interface inside the reservoir, emitting a laser beam and receiving the reflected echo. The in-wellbore probe assembly includes a laser emitting module, a laser receiving module, a high-pressure resistant sealed housing, and a light-transmitting window; and an external wellbore control assembly, located outside the wellbore, electrically and signal-connected to the in-wellbore probe assembly, used for power supply, signal acquisition, data processing, and communication. This application allows for real-time measurement of the gas-liquid interface while the wellhead remains sealed and closed, avoiding the gas leakage risks, operational safety hazards, and production stoppage losses associated with traditional well-opening measurement methods. Furthermore, the non-contact measurement overcomes the problems of scaling and failure of contact level gauges in the high salt spray and highly corrosive environment of salt caverns.

Description

Technical Field

[0001] This application relates to the field of underground salt cavern storage monitoring and wellbore online detection technology, and in particular to a non-contact detector and method for the gas-liquid interface of salt cavern storage based on laser ranging. Background Technology

[0002] Salt caverns, as important underground energy storage methods such as compressed air storage, natural gas storage, and hydrogen storage, often exhibit a dynamic gas-liquid interface during injection and production operations, where gas and liquid phases coexist within the cavity. The location of this gas-liquid interface directly affects the effective volume of the storage facility, injection and production safety, pressure fluctuations, and cavity stability; therefore, real-time, accurate, and continuous monitoring of this interface is of great significance.

[0003] Existing gas-liquid interface detection technologies mainly include contact level gauges, pressure inversion methods, acoustic ranging methods, and manual periodic measurements. Contact level gauges require direct contact with the medium, which can easily lead to scaling, corrosion, failure, and maintenance difficulties in the high-salt-spray, high-humidity, highly corrosive, and high-pressure environments of salt caverns. Pressure inversion methods indirectly estimate the level based on parameters such as temperature, pressure, and gas composition, but are greatly affected by model errors and parameter fluctuations, making accuracy difficult to control. Although acoustic ranging methods can achieve non-contact measurement, they are easily affected by complex reflections, attenuation, gas density changes, foam, and droplet scattering in salt caverns, resulting in difficulties in echo identification, insufficient resolution, and poor stability. Manual measurements have problems such as high safety risks, poor real-time performance, and unsuitability for continuous monitoring.

[0004] Furthermore, the wellbore and cavity environment of salt cavern reservoirs typically features long distances, weak lighting, strong salt mist, large temperature and humidity fluctuations, wellbore deviation, and localized multiple reflections, placing higher demands on the sealing, protection, signal recognition, and algorithm compensation of measuring equipment. Currently, there is a lack of a gas-liquid interface detection technology suitable for the complex operating conditions of salt cavern reservoirs, possessing non-contact, real-time, continuous, high-precision, anti-interference capabilities, and easy online deployment. Therefore, there is an urgent need to develop a non-contact, high-precision detection device and method capable of real-time measurement while maintaining a sealed wellhead. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a non-contact detector and method for the gas-liquid interface in salt cavern storage based on laser ranging. This aims to resolve existing technical problems in salt cavern gas-liquid interface detection, such as the susceptibility to corrosion of contact equipment, large indirect calculation errors, poor real-time performance, insufficient adaptability to complex downhole environments, the need for equipment to be deployed inside or open the well, large space requirements, the need to open the wellhead for measurement, high operational safety risks, long downtime, and high maintenance costs. The technical solution is as follows: The first aspect of this application provides a non-contact detector for the gas-liquid interface of a salt cavern reservoir based on laser ranging, used to complete real-time measurement of the gas-liquid interface while the wellhead remains sealed and closed. The detector includes: an in-well probe assembly installed inside the wellbore and directly facing the gas-liquid interface inside the reservoir to emit a laser beam and receive reflected echoes; the in-well probe assembly includes a laser emitting module, a laser receiving module, a high-pressure resistant sealed housing, and a light-transmitting window; and an external wellbore control assembly located outside the wellbore, electrically and signal-connected to the in-well probe assembly, used for power supply, signal acquisition, data processing, and communication. According to the above embodiments, by integrating the laser emitting module and the laser receiving module into the probe assembly inside the wellbore and directly facing the gas-liquid interface, while setting the power supply, control, and processing units outside the wellbore, a split, wellbore-integrated non-contact measurement structure is formed. The effect is that real-time measurement of the gas-liquid interface can be completed while the wellhead is kept sealed and closed, without opening the wellhead or entering the well for operation. This avoids the risks of gas leakage, operational safety hazards, and production stoppage losses caused by traditional well-opening measurement methods. At the same time, non-contact measurement overcomes the problems of easy scaling and failure of contact level gauges in high salt spray and highly corrosive environments in salt caverns.

[0006] For example, in one embodiment of the non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging, the probe assembly inside the wellbore further includes an optical collimation and focusing module for shaping the laser beam to reduce the divergence angle. According to the above embodiment, by setting the optical collimation and focusing module to shape the laser beam to reduce the divergence angle, the effect is to: increase the directional energy and propagation distance of the laser beam, maintain a smaller spot divergence in the long-distance gas phase space of the wellbore, enhance the light intensity reaching the gas-liquid interface, thereby obtaining a stronger reflected echo signal and improving the signal-to-noise ratio and stability of long-distance measurements.

[0007] For example, in one embodiment of the non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging, the probe assembly inside the wellbore further includes an anti-salt mist and anti-scaling module to reduce the adhesion of salt mist, water vapor, and crystalline salt particles to the surface of the light-transmitting window. According to the above embodiment, by setting the anti-salt mist and anti-scaling module to act on the light-transmitting window, the effect is to reduce the adhesion of salt mist, water vapor, and crystalline salt particles to the window surface, maintain a long-term stable light transmittance of the optical window, avoid laser emission energy attenuation or echo signal loss due to window contamination, and ensure the continuous and reliable operation of the detector in the harsh environment of high humidity and high salt mist in the salt cavern storage facility.

[0008] For example, in one embodiment of the non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging, the anti-salt spray and anti-scaling module includes at least one of an annular air curtain purging unit, a window heating unit, and a surface hydrophobic and salt-repellent coating. According to the above embodiment, by employing an annular air curtain purging to form a clean gas protective layer, window heating to prevent condensation, and a surface hydrophobic and salt-repellent coating to improve anti-pollution capability, the effect is: to construct a multi-layered active and passive protection synergistic mechanism; air curtain purging to remove attached salt spray particles in real time; heating unit to eliminate condensate interference; and coating to reduce the adhesion strength of pollutants. The combination of these three elements can significantly extend the window cleaning cycle, reduce the frequency of manual maintenance, and ensure the feasibility of long-term continuous monitoring.

[0009] For example, in one embodiment of the non-contact detector for the gas-liquid interface of a salt cavern reservoir based on laser ranging, the external control component includes: a power supply module for power supply; a signal acquisition module for receiving and converting echo signals; a data processing module for calculating the gas-liquid interface distance and elevation; an environmental parameter acquisition module for real-time acquisition of temperature, pressure, humidity, and gas composition; an attitude detection module for obtaining the detector's installation tilt angle; and a communication module for uploading measurement results. According to the above embodiment, by integrating the power supply, signal acquisition, data processing, environmental parameter acquisition, attitude detection, and communication modules, the effect is to achieve comprehensive control and compensation of the measurement process without opening the well. The environmental parameter acquisition module acquires temperature, pressure, humidity, and gas composition in real time to correct the laser propagation speed and refractive index; the attitude detection module provides the installation tilt angle for vertical distance correction of deviated wells or skewed installations, thereby eliminating the influence of environmental changes and installation errors on the ranging accuracy and improving the accuracy of the measurement results.

[0010] For example, in one embodiment of the laser ranging-based non-contact detector for the gas-liquid interface of a salt cavern reservoir, the high-pressure resistant sealing shell is made of corrosion-resistant metal material, capable of withstanding the high pressure, high humidity, and high salt spray environment inside the salt cavern reservoir. According to the above embodiment, by using a high-pressure resistant sealing shell made of corrosion-resistant metal material, the effect is that the probe assembly inside the wellbore can withstand the high pressure (tens of megapascals), high humidity, and high salt spray environment inside the salt cavern reservoir, protecting the internal optical and electronic components from pressure damage and chemical corrosion, and ensuring the long-term physical integrity and functional stability of the detector under extreme conditions in deep formations.

[0011] The second aspect of this application provides a non-contact detection method for the gas-liquid interface in a salt cavern reservoir based on laser ranging, comprising the following steps: installing a probe assembly inside the wellbore, completing the sealing connection and optical path calibration; emitting a laser beam into the reservoir through a laser emitting module while the wellhead remains closed; acquiring reflected echoes from the gas-liquid interface through a laser receiving module; filtering, denoising, and extracting multiple features from the echo signals to identify the true interface echo; calculating the gas-liquid interface distance and absolute elevation based on laser flight time, environmental parameter compensation, and attitude correction; and outputting a real-time interface change curve. According to the above embodiment, by sequentially executing the steps of probe installation, laser emission under wellhead sealing, echo acquisition, multi-feature identification, environmental compensation and attitude correction, and outputting the interface curve, the effect is that a complete "emission-reception-identification-compensation-output" closed-loop measurement process is formed. This method organically combines hardware structure with signal processing algorithms, achieving automated calculation from the original echo to a high-precision interface elevation without opening the wellhead, solving the problems of large errors, poor real-time performance, and inability to continuously monitor traditional indirect calculation methods.

[0012] For example, in one embodiment of the non-contact detection method for gas-liquid interfaces in salt cavern storage based on laser ranging, the identification of real interface echoes includes: extracting the amplitude, peak width, signal-to-noise ratio, waveform symmetry, multi-frame continuity, and time stability features of candidate echoes, constructing a confidence evaluation function, and determining that an echo is a real gas-liquid interface echo when the confidence level is higher than a threshold. According to the above embodiment, by extracting multi-dimensional features such as amplitude, peak width, signal-to-noise ratio, waveform symmetry, multi-frame continuity, and time stability of candidate echoes, and constructing a confidence evaluation function, an echo is determined to be a real gas-liquid interface echo only when the confidence level is higher than a threshold. The effect is that it effectively distinguishes gas-liquid interface echoes from multi-path interference signals such as wellbore reflection, foam layers, and droplet scattering, avoiding misjudgments or measurement jumps caused by clutter in complex downhole environments, and significantly improving the reliability of interface identification and the robustness of measurement results.

[0013] For example, in one embodiment of the non-contact detection method for the gas-liquid interface of a salt cavern storage facility based on laser ranging, the environmental parameter compensation includes: correcting the laser propagation speed and refractive index in the gaseous medium based on real-time collected temperature, pressure, humidity, and gas composition information; the attitude correction includes: vertically correcting the measurement distance based on the installation tilt angle of the detector. According to the above embodiment, by correcting the laser propagation speed and refractive index through real-time collection of temperature, pressure, humidity, and gas composition, and combining this with vertical correction of the ranging value based on the installation tilt angle, the effect is to eliminate ranging errors caused by changes in environmental parameters (such as temperature fluctuations leading to changes in gas density) and wellbore tilt. Compared to direct ranging methods that do not consider changes in refractive index and geometric tilt angles, the compensation and correction mechanism of this application can control the absolute error of long-distance measurements (hundreds of meters) to the centimeter or even millimeter level, meeting the engineering requirements for precise positioning of the gas-liquid interface in salt cavern storage facilities.

[0014] For example, in one embodiment of the non-contact detection method for the gas-liquid interface of a salt cavern storage system based on laser ranging, a continuous monitoring and linkage control step is also included: dynamically filtering the continuous measurement results to generate an interface change curve; when the interface height exceeds a preset safety threshold, an alarm signal is automatically issued or the injection and production control system is linked for adjustment. According to the above embodiment, by dynamically filtering the continuous measurement results to generate a smooth interface change curve, and automatically issuing an alarm signal or linking the injection and production control system for adjustment when the interface height exceeds a preset safety threshold, the effect is to achieve a complete closed loop from "data acquisition" to "intelligent early warning and automatic control". The real-time interface change curve can be used to analyze the dynamics of the storage system's injection and production and to determine changes in the effective volume of the cavity; the over-limit linkage function can prevent gas from carrying liquid phase into the production pipeline due to an excessively high interface, or to prevent insufficient effective volume of the cavity and abnormal pressure due to an excessively low interface, thereby improving the safety and automation level of the salt cavern storage system.

[0015] This application provides a non-contact detector and method for the gas-liquid interface of a salt cavern storage facility based on laser ranging. Through techniques such as wellbore embedding, split-type arrangement, non-contact laser ranging, multi-feature echo recognition, environmental parameter compensation, and attitude correction, it achieves the following significant advantages: (1) Continuous real-time monitoring without well opening is achieved: The laser emission and reception module is set inside the wellbore, while the control and processing unit is placed outside the well. The wellhead is kept sealed and closed throughout the measurement process. This design fundamentally avoids the risks of gas leakage, operational safety risks, and production stoppage losses caused by the traditional method of opening the wellhead for measurement. It significantly improves the safety and convenience of on-site detection and achieves true online continuous monitoring.

[0016] (2) Solved the long-term reliability problem in salt cavern corrosion environment: The probe assembly inside the wellbore adopts a high-pressure resistant sealed shell and a salt spray and scale prevention module (air curtain purging, heating demisting, hydrophobic and salt-repellent coating), which can effectively resist the pollution and erosion of the optical window by high salt spray, high humidity, strong corrosion and high pressure harsh environment. Even in long-term operation, the light-transmitting window can still maintain a high light transmittance, avoiding the defects of contact sensors that are prone to scale failure, and greatly reducing the maintenance frequency and operation and maintenance costs.

[0017] (3) Significantly improved measurement accuracy in complex downhole environments: By using a multi-feature fusion confidence evaluation function, the true gas-liquid interface echo is identified from multiple dimensions such as echo amplitude, peak width, signal-to-noise ratio, waveform symmetry, multi-frame continuity, and time stability, effectively eliminating clutter interference such as well wall reflection, foam layer, and droplet scattering. At the same time, the laser propagation speed and refractive index are compensated by real-time acquisition of temperature, pressure, humidity, and gas composition, and the installation tilt angle is vertically corrected by the attitude detection module, so that the absolute error of long-distance (hundreds of meters) measurement can be controlled at the centimeter or even millimeter level, which is better than traditional indirect calculation or acoustic ranging methods.

[0018] (4) It has intelligent early warning and linkage control capabilities: The system can continuously output a smooth interface change curve and automatically issue an alarm signal or link the injection and production control system for adjustment when the interface height exceeds the preset safety threshold. This closed-loop function can prevent gas from carrying liquid phase into the production pipeline due to excessively high interface height, or prevent insufficient effective volume of the cavity and abnormal pressure due to excessively low interface height, thereby improving the safety and automation level of the salt cavern storage operation.

[0019] (5) Compact structure and strong adaptability: The probe assembly inside the wellbore is small in size, suitable for the retrofitting and standardized deployment of existing wellbore systems, and does not occupy the space around the wellhead. Since non-contact laser ranging is used, there is no need to lay complex cables or liquid level sensing chains inside the wellbore, making installation and maintenance convenient. At the same time, this technical solution is applicable to various salt cavern storage scenarios such as compressed air energy storage, natural gas storage, and hydrogen storage, and has broad engineering promotion value.

[0020] In summary, this application systematically solves the pain points of existing gas-liquid interface detection technologies in complex working conditions of salt cavern storage, such as easy corrosion, low accuracy, poor real-time performance, high safety risks, and insufficient adaptability, through a series of innovative designs including wellbore-integrated laser ranging, split structure, multi-feature echo recognition, environmental compensation, and attitude correction. It provides a reliable technical means for intelligent monitoring of underground energy storage. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Fig. 1 This is a schematic diagram of the overall structure of the non-contact detector for the gas-liquid interface of a salt cavern storage based on laser ranging, as described in this application. Fig. 2 This is a cross-sectional view of the wellbore installation of the non-contact detector for the gas-liquid interface in a salt cavern storage system based on laser ranging, as described in this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0025] I. Overall Structure of the Detector like Figs. 1-2 As shown, this application provides a non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging. It adopts a split structure and includes an in-well probe assembly and an external control assembly 7.

[0026] The probe assembly inside the wellbore 22 is mainly composed of: a laser emitting module 1, a laser receiving module 2, an optical collimation and focusing module 3, a high-pressure resistant sealed housing 4, a light-transmitting window 5, and an anti-salt spray and anti-scaling module 6.

[0027] The external control component 7 is located outside the wellbore 22 and mainly includes: a power module 8, a signal acquisition module 9, a data processing module 10, an environmental parameter acquisition module 11, an attitude detection module 12, a communication module 13, and a human-machine interaction module 14.

[0028] The measuring components inside the well and the control components outside the well are electrically connected and transmit signals through the ground pipeline 25, forming a split-type, well-built detection system.

[0029] II. Functions and Connections of Components in the Wellbore Probe Assembly The laser emitting module 1 preferably uses a pulsed laser to emit a pulsed laser beam into the salt cavern storage. The optical collimation and focusing module 3 is located on the output path of the laser emitting module 1 to shape the laser beam into an incident laser beam 15 with good directionality and a small divergence angle.

[0030] The light-transmitting window 5 is mounted on the high-pressure resistant sealed housing 4, serving as the optical channel for the laser beam to enter and exit the wellbore. The laser receiving module 2 is positioned on the echo path of the light-transmitting window 5, and preferably includes a high-sensitivity photodetector for receiving the reflected echo 16 from the gas-liquid interface and converting it into an electrical signal.

[0031] The high-pressure resistant sealed housing 4 is made of corrosion-resistant metal material, which can withstand the high pressure, high humidity and high salt spray environment inside the salt cavern storage, and protect the internal optical and electronic components.

[0032] The anti-salt spray and anti-scaling module 6 is disposed around the light-transmitting window 5 and includes at least one of the following: an annular air curtain purging unit, a window heating unit, and a surface hydrophobic and alkali-repellent coating. The air curtain purging unit forms a clean gas protective layer on the outside of the light-transmitting window 5 to reduce direct adhesion of salt spray; the heating unit keeps the window surface temperature above the dew point temperature to prevent water vapor condensation; and the hydrophobic and alkali-repellent coating further improves the anti-fouling ability.

[0033] III. Functions of Each Component in the External Control Assembly for Wellbore Power module 8 supplies power to the various functional units outside the wellbore and the measurement components inside the wellbore. Signal acquisition module 9 samples, amplifies, and transmits the electrical signal output by laser receiving module 2. Data processing module 10 performs filtering, noise reduction, threshold determination, peak extraction, waveform feature analysis, distance calculation, and attitude correction on the echo signal.

[0034] The environmental parameter acquisition module 11 is used to collect real-time information on temperature, pressure, humidity, and gas composition within the wellbore 22. The attitude detection module 12 is used to obtain the installation tilt angle θ of the detector relative to the wellbore axis. The communication module 13 is used to upload the processed measurement results to an external monitoring system or host computer platform in real time. The human-machine interaction module 14 is used to display the current interface position, historical change curves, alarm status, and equipment operating status.

[0035] IV. Distance Measurement Principles and Environmental Compensation Methods The detector employs the laser time-of-flight ranging principle. After the laser emitting module 1 emits a pulsed laser, the incident laser beam 15 enters the wellbore through the light-transmitting window 5, and upon reaching the gas-liquid interface 18, generates a reflected echo 16. This echo is received by the laser receiving module 2 and converted into an electrical signal. Let the time difference between laser emission and echo reception be t, and the laser propagation speed in the current gaseous medium be v, then the interface distance L is: Considering the refractive index n of the gas, we have v = n·c (where c is the speed of light in vacuum), therefore: The environmental parameter acquisition module 11 acquires real-time temperature, pressure, humidity, and gas composition data to calculate the current value of the refractive index n and compensate for the laser propagation speed. The attitude detection module 12 outputs the installation tilt angle θ to perform vertical correction on the measurement results. If the wellhead reference elevation is Z0, then the absolute elevation of the gas-liquid interface is: H V. Echo Signal Identification and Anti-interference Mechanism The data processing module 10 performs filtering, noise reduction, time gating, and multi-feature extraction on the acquired echo signals. To effectively distinguish between real gas-liquid interface echoes and wellbore reflections, foam layers, water mist particles, and other interference signals, the system employs a multi-feature fusion recognition method.

[0036] The following features are extracted from candidate echoes: echo amplitude A; peak width (waveform width); signal-to-noise ratio S; waveform symmetry; multi-frame continuity R; and time stability.

[0037] Construct the confidence evaluation function C: Where Q is the waveform quality factor, and α, β, γ, and δ are weighting coefficients. When C is higher than a preset threshold, the echo is determined to be a true gas-liquid interface echo; when it is lower than the threshold, it is discarded as an interference signal.

[0038] The system can also be set with a time-gated window to only collect data within the expected echo arrival time range, in order to further reduce wellbore reflections and clutter.

[0039] VI. Specific Operating Procedures In one specific embodiment, the detection process is as follows: Installation and initialization: Securely install the probe assembly inside the measuring section of the wellbore 22, and complete the sealing connection, optical path calibration, and zero-point calibration. Keep the wellhead and its sealing structure 23 closed.

[0040] Power-on and parameter acquisition: The external control component 7 is powered on, initialized, performs self-test, loads parameters, and establishes a communication link. The environmental parameter acquisition module 11 acquires the temperature, pressure, humidity, and gas composition inside the wellbore; the attitude detection module 12 monitors the installation tilt angle.

[0041] Laser emission and echo reception: The data processing module 10 controls the laser emission module 1 to emit laser light according to the set operating frequency and pulse parameters. The incident laser beam 15 is shaped by the optical collimation and focusing module 3, enters the wellbore 22 through the light transmission window 5, propagates in the gas phase space 20, reaches the gas-liquid interface 18, and is reflected to form a reflected echo 16. The reflected echo 16 returns through the light transmission window 5, is captured by the laser receiving module 2, and is converted into an electrical signal.

[0042] Signal processing and interface recognition: The signal acquisition module 9 samples and amplifies the electrical signal and sends it to the data processing module 10. The data processing module 10 filters, denoises, determines thresholds, extracts peak values, and analyzes waveform features of the echo signal, extracts multiple features, calculates the confidence level C, and identifies the real gas-liquid interface echo.

[0043] Distance calculation and compensation: The data processing module 10 compensates for the laser propagation speed and refractive index based on the laser flight time and the temperature, pressure, humidity and gas composition provided by the environmental parameter acquisition module 11. It also uses the tilt angle θ output by the attitude detection module 12 for vertical correction and calculates the actual distance, height and absolute elevation of the gas-liquid interface 18 relative to the wellbore reference position.

[0044] Continuous monitoring and data output: The system continuously acquires gas-liquid interface echo signals without well opening and outputs interface height information in real time. Data processing module 10 performs moving average, median filtering, or Kalman filtering on the continuous results to obtain a stable interface change curve. Communication module 13 uploads the results to a ground monitoring platform, SCADA system, or storage tank operation control system. Human-machine interface module 14 displays the current interface position, change curve, and equipment status.

[0045] Alarm and linkage: When the interface height exceeds the preset safety threshold, the data processing module 10 automatically issues an alarm message and links the injection and extraction control system through the communication module 13 to make adjustments or execute prompts and protection actions.

[0046] VII. Long-term operation and maintenance During long-term operation, the anti-salt spray and anti-scaling module 6 works continuously: the air curtain purging unit periodically or continuously blows clean gas onto the surface of the light-transmitting window 5; the heating unit keeps the window surface temperature above the dew point temperature to prevent condensation; and the hydrophobic and salphobic coating reduces contaminant adhesion. When the echo signal is detected to be affected by contamination, the interface recognition algorithm in the data processing module 10 automatically removes outliers through multi-feature discrimination to maintain measurement continuity.

[0047] If maintenance is required, the probe assembly inside the wellbore only needs to be removed as a whole for cleaning or replacement, without having to open the wellhead for complex operations.

[0048] VIII. Alternative Solutions and Expansions The laser emission module 1 can also employ a continuous wave laser ranging scheme, obtaining distance information through the phase method. The environmental parameter acquisition module 11 can also integrate a humidity sensor and a gas composition analysis sensor (such as CO2 and CH4 sensors) to further improve the refractive index compensation accuracy. The attitude detection module 12 can employ a triaxial accelerometer or tilt sensor. The communication module 13 supports RS485, Ethernet, 4G / 5G, or fiber optic communication.

[0049] This application is also applicable to other underground storage facilities that require long-distance, non-contact, real-time liquid level or interface detection, such as underground water-sealed caverns and abandoned mine energy storage.

[0050] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging, characterized in that, Used for real-time measurement of the gas-liquid interface while the wellhead remains sealed and closed, including: The wellbore probe assembly is installed inside the wellbore and directly faces the gas-liquid interface inside the reservoir to emit a laser beam and receive reflected echoes. The wellbore probe assembly includes a laser emitting module, a laser receiving module, a high-pressure resistant sealed housing, and a light-transmitting window. The external control component is located outside the wellbore and is electrically and signal connected to the probe component inside the wellbore. It is used for power supply, signal acquisition, data processing, and communication.

2. The non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging according to claim 1, characterized in that, The probe assembly inside the wellbore also includes an optical collimation and focusing module for shaping the laser beam to reduce the divergence angle.

3. The non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging according to claim 1, characterized in that, The probe assembly inside the wellbore also includes an anti-salt spray and anti-scaling module, which is used to reduce the adhesion of salt spray, water vapor and crystalline salt particles to the surface of the light-transmitting window.

4. The non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging according to claim 3, characterized in that, The anti-salt spray and anti-scaling module includes at least one of an annular air curtain blowing unit, a window heating unit, and a surface hydrophobic and salt-repellent coating.

5. The non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging according to claim 1, characterized in that, The external control assembly for the wellbore includes: The power module is used for power supply; The signal acquisition module is used to receive and convert echo signals; The data processing module is used to calculate the gas-liquid interface distance and elevation. The environmental parameter acquisition module is used to collect temperature, pressure, humidity, and gas composition in real time. The attitude detection module is used to obtain the installation tilt angle of the detector; The communication module is used to upload measurement results.

6. The non-contact detector for the gas-liquid interface of a salt cavern storage facility based on laser ranging according to claim 1, characterized in that, The high-pressure resistant sealing shell is made of corrosion-resistant metal material and can withstand the high pressure, high humidity and high salt spray environment inside the salt cavern storage.

7. A non-contact detection method for the gas-liquid interface in salt cavern storage based on laser ranging, characterized in that, The detector according to any one of claims 1 to 6 comprises the following steps: Install the probe assembly inside the wellbore, complete the sealing connection and optical path calibration; With the wellhead closed, a laser beam is emitted into the reservoir via a laser emission module; The reflected echo from the gas-liquid interface is collected by a laser receiving module; The echo signal is filtered, denoised, and multi-feature extracted to identify the real interface echo; Based on laser flight time, environmental parameter compensation, and attitude correction, the gas-liquid interface distance and absolute elevation are calculated. Output the real-time interface change curve.

8. The non-contact detection method for the gas-liquid interface of salt cavern storage based on laser ranging according to claim 7, characterized in that, The identification of real interface echoes includes: extracting the amplitude, peak width, signal-to-noise ratio, waveform symmetry, multi-frame continuity and time stability features of candidate echoes, constructing a confidence evaluation function, and determining that when the confidence is higher than the threshold, it is a real gas-liquid interface echo.

9. The non-contact detection method for the gas-liquid interface of a salt cavern storage tank based on laser ranging according to claim 7, characterized in that, The environmental parameter compensation includes: correcting the propagation speed and refractive index of the laser in the gaseous medium based on real-time collected temperature, pressure, humidity and gas composition information; the attitude correction includes: vertically correcting the measurement distance based on the installation tilt angle of the detector.

10. The non-contact detection method for the gas-liquid interface of a salt cavern storage tank based on laser ranging according to claim 7, characterized in that, It also includes continuous monitoring and linkage control steps: dynamically filtering the continuous measurement results to generate interface change curves; when the interface height exceeds the preset safety threshold, an alarm signal is automatically issued or the injection and extraction control system is linked to make adjustments.

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