Seismic gas coupling monitoring well suitable for carbon dioxide geological storage in mining space

Abstract

This invention belongs to the field of monitoring wells, specifically a seismic-gas coupled monitoring well applicable to the geological sequestration of carbon dioxide in mining spaces. It includes a well drilled from the surface to the goaf. During drilling, monitoring systems are installed at the goaf, fracture zone, aquifer, and upper loose layer. Each monitoring system includes a protective tubing system and monitoring components such as sensors arranged within it. A connecting tubing system is also provided to connect the protective tubing system. The inner tubing of all tubing systems forms a sealed pipeline cavity, within which a transmission pipeline is installed and led to the surface. This invention, through a vertical architecture design of one well and four layers, establishes a full-path monitoring barrier from the goaf, fracture zone, overlying aquifer, loose layer to the surface. The segmented isolation design of the monitoring system not only accurately locates the specific layer where CO2 leaks but also effectively distinguishes between leakage and interference, facilitating accurate evaluation of CO2 geological sequestration leakage.

Description

Technical Field

[0001] This invention belongs to the field of monitoring wells, specifically a seismic-gas coupled monitoring well applicable to geological carbon dioxide sequestration in mining spaces. Background Technology

[0002] After coal mining, from bottom to top, caving zones (goaf), fracture zones, and flexural subsidence zones form. The caving zones contain numerous void spaces, and the fracture zones also contain some void spaces. These void spaces can be used for CO2 geological sequestration. The flexural subsidence zone, due to its maintenance of strata integrity, often serves as a caprock. The movement of the overlying strata continues long after coal mining, taking decades to reach relative stability. In the caving zones, the large void spaces between rock fragments are easily compressed under the pressure of the overlying strata. In the fracture zones, rock blocks are prone to new fracturing, rotation, and other activation movements under the pressure of the overlying strata. Due to insufficient strata stability, utilizing the mining-affected spaces for CO2 geological sequestration is prone to vertical leakage. Therefore, monitoring CO2 leakage in coal mining-affected spaces is essential.

[0003] The existing methods for monitoring leaks in CO2 geological storage have the following shortcomings: (1) The monitoring dimensions are single, resulting in a serious "data silo" phenomenon: Existing monitoring methods often focus on monitoring single physical or chemical indicators. For example, chemical sensors can only capture changes in CO2 concentration that have leaked to a specific location, which is a "lagging monitoring"; while conventional microseismic monitoring can capture rock fractures, it cannot distinguish whether the fractures are filled with water, air or CO2. Due to the lack of multi-parameter coupling correlation, fluctuations in a single indicator often lead to false alarms of CO2 leaks. (2) The lack of hierarchical and targeted design makes it difficult to achieve "layered interception" monitoring: CO2 migration in the mining space has a clear tendency to spread vertically upwards. Existing single-point monitoring or full-well-section line-of-sight monitoring cannot accurately locate the specific retention layer and migration front of CO2 on the vertical profile, making it difficult to issue early warnings in the early stages of leakage. (3) The lack of monitoring of CO2 leak precursor information leads to insufficient preparation for CO2 leak handling. In addition, the existing monitoring methods have a large workload for monitoring and data processing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a seismic-gas coupling monitoring well suitable for carbon dioxide geological sealing in mining spaces. This includes drilling from the surface to the goaf, with monitoring systems installed in the goaf, fracture zone, aquifer, and loose strata above the aquifer during drilling. The goaf monitoring system includes a goaf protection tubing system, comprising a cylindrical tube at least closed at the top, with connecting holes on the sidewalls. A partition divides the tube into upper and lower chambers. The top wall of the upper chamber houses a first CO2 integrated monitoring sensor and a gas concentration sensor. The lower chamber contains a water level sensor, a first water quality monitoring sensor, and a drainage system. The system includes a pump and an active wave excitation device; a first water quality monitoring sensor capable of acquiring at least the pH value of the water accumulated in the goaf; a fracture zone monitoring system comprising a fracture zone protection tubular system, which includes a circular first inner tubular column and a flexible breathable skin, wherein the top and bottom of the first inner tubular column and the flexible breathable skin are connected by a first connecting ring to form an air chamber, and the air inlet channel of the air chamber is the flexible breathable skin; a second CO2 integrated monitoring sensor is installed in the air chamber; a telescopic device is installed on the outer wall of the first inner tubular column, which is radially arranged, with the bottom end of the cylinder fixed to the outer wall of the first inner tubular column, and a first micro-vibration detector is installed at the top of the telescopic end.

[0005] Preferably, the aquifer monitoring system includes an aquifer protection pipe column system, which includes a coaxially arranged circular inner pipe column and a porous outer pipe wall. The top and bottom of the inner pipe column and the porous outer pipe wall are connected by a second connecting ring to form a chamber. The water inlet channel of the chamber is the porous outer pipe wall. A CO2 concentration sensor, a second water quality monitoring sensor, a pH-sensitive microcapsule, a microcapsule tracer sensor, and a sampling pump are installed in the chamber.

[0006] Preferably, the loose layer monitoring system includes a loose layer protection pipe column system, which includes a third inner pipe column and a first outer pipe wall arranged coaxially, with the top and bottom of the third inner pipe column and the first outer pipe wall connected by a third connecting ring; a sensor slot is provided on the outside of the first outer pipe wall, and a third CO2 integrated monitoring sensor is provided in the sensor slot.

[0007] Preferably, the monitoring well consists of, from bottom to top, a sealed goaf protection tubing system, a fracture zone protection tubing system, a lower connecting tubing system, an aquifer protection tubing system, an upper connecting tubing system, and a loose layer protection tubing system. The connecting tubing system includes a coaxially arranged circular inner tubing and a second outer tubing wall, with the top and bottom of the inner and outer tubing walls connected by a fourth connecting ring. A wellhead device is installed at the top of the monitoring well. A second microseismic detector is also installed on the surface corresponding to the goaf.

[0008] Preferably, the inner tubing of the fracture zone protection tubing system, the lower connecting tubing system, the aquifer protection tubing system, the upper connecting tubing system, and the loose layer protection tubing system forms a sealed pipeline cavity. A transmission pipeline is installed in the pipeline cavity. One end of the cable in the transmission pipeline extends to the ground surface and the other end is connected to the sensors, active wave excitation device, telescopic device, and first microseismic detector in the monitoring well. The other end of the pipe in the transmission pipeline extends to the ground surface and is connected to the water pump in the monitoring well.

[0009] Preferably, the first, second, and third CO2 integrated monitoring sensors all include a CO2 concentration sensor, a humidity sensor, and a pressure sensor; the telescopic device is equipped with a radial support force acquisition device; the second water quality monitoring sensor can at least acquire the pH value of the aquifer water; the pH-sensitive microcapsule acts as a chemical threshold switch, releasing a specific tracer when a set CO2 concentration is dissolved in the aquifer water, and the microcapsule tracer sensor is used to capture the specific tracer; the CO2 concentration sensor is used to acquire the CO2 gas concentration in the aquifer water; and the sampling pump is capable of sampling the aquifer water.

[0010] This invention also provides a monitoring well construction and monitoring method for constructing the aforementioned seismic-gas coupled monitoring well suitable for carbon dioxide geological sealing in mining spaces, comprising the following steps: S1: First drilling, penetrating the loose layer and its internal aquifer, with the casing running synchronously with the drill bit during drilling; Second drilling, drilling to the bottom plate of the goaf; S2: In the second drilling, sequentially lowering the goaf monitoring system, fracture zone monitoring system, and lower connecting tubing system from bottom to top, and connecting the transmission pipeline; S3: In the first drilling, sequentially lowering the aquifer monitoring system, upper connecting tubing system, and loose layer monitoring system from bottom to top, and connecting the transmission pipeline; Installing a wellhead device, and setting a second microseismic detector on the surface corresponding to the goaf; S4: After CO2 geological sealing in the goaf, operating the monitoring well to monitor CO2 leakage; S5: CO2 leakage early warning processing.

[0011] Preferably, in step S4, the monitoring mode is set to passive sentinel monitoring mode under normal circumstances: each sensor samples at low frequency, and the first and second microseismic detectors are always on. The microseismic detectors passively receive the microseismic signals generated by the activation movement of the rock strata. When the microseismic signal indicates that the rock strata have activated, each sensor starts high-frequency sampling. The active precursor detection mode is activated once at fixed intervals: the active wave excitation device located at the bottom of the goaf is activated, so that it periodically impacts the floor of the goaf to generate stable elastic wave signals. The first and second microseismic detectors receive the direct waves and transmitted waves generated by the active wave excitation device. Using wave velocity tomography technology, the fracture zone and the dynamic development of fractures in the strata of the goaf are inverted and generated. When the activation movement of the rock strata is detected, each sensor starts high-frequency sampling.

[0012] Preferably, in step S5, the amount of CO2 contained in the goaf water is calculated based on the area of ​​the goaf, the height of the goaf water obtained from the water level sensor, and the CO2 concentration dissolved in the goaf water obtained from the first water quality monitoring sensor, and the impact of the goaf water on the CO2 concentration is analyzed; the gas concentration in the goaf obtained from the gas concentration sensor is analyzed to determine the impact of the gas concentration on the CO2 concentration; considering the influence of goaf water and gas, the first CO2 comprehensive monitoring sensor is used to determine whether there are abnormal changes in the goaf CO2 concentration and whether there is a CO2 leak; when there is a lot of goaf water, the goaf water is drained to the ground by a drainage pump, and the amount of CO2 carried by the drained goaf water is analyzed to further analyze its impact on the CO2 concentration; the goaf water is kept below the height of the partition; based on the second CO2 comprehensive monitoring sensor... The system employs a multi-sensor approach: a sensor detects abnormal changes in CO2 concentration within the fracture zone to determine if a CO2 leak is occurring; a telescopic device is controlled to maintain adequate radial support; a second water quality monitoring sensor acquires the CO2 concentration dissolved in the aquifer water and detects any abnormal changes to determine if a CO2 leak is occurring; a microcapsule tracer sensor captures specific tracers to further determine if a CO2 leak is occurring, providing comprehensive verification; furthermore, if the CO2 concentration sensor detects the presence of CO2 gas in the aquifer, indicating a CO2 leak, a sampling pump is used to sample the aquifer water, and precise laboratory testing is conducted to further determine if a CO2 leak is occurring; a third comprehensive CO2 monitoring sensor detects abnormal changes in CO2 concentration to determine if a CO2 leak is occurring, referencing CO2 concentration benchmarks under different seasons and day / night conditions.

[0013] The invention points and beneficial technical effects of the present invention are as follows: (1) It achieves full-space coverage capability of vertical layering and targeted interception: Through the vertical architecture design of one well and four layers, a full-path monitoring barrier is established from the goaf, fracture zone to the overlying aquifer, loose layer to the surface; the segmented isolation design of the monitoring system can not only accurately locate the specific layer where CO2 leaks, but also effectively distinguish between leakage and interference, which is conducive to accurately evaluating the leakage situation of CO2 geological sequestration.

[0014] (2) The coupling and correlation of multiple parameters significantly reduces the false alarm rate of safety warnings: It breaks through the limitations of single indicator monitoring and forms a multi-dimensional cross-confirmation system of "rock mechanics (micro-seismic / wave velocity) - fluid mechanics (gas pressure / concentration) - geochemistry (tracer)". Through the spatiotemporal correlation analysis of multi-dimensional monitoring data, false anomalies caused by environmental interference (loose layer environment, gas influence in goaf) are reduced.

[0015] (3) It has high adaptability and coupling: In view of the characteristics of continuous movement of rock strata in fracture zone and uneven distribution of fractures, the proposed "radial hydraulic adaptive skeleton" not only solves the problem of equipment support in deformed wellbore, but also cleverly realizes the forced rigid coupling between microseismic detector and rock wall, which greatly improves the signal-to-noise ratio and acquisition quality of microseismic wave signal.

[0016] (4) Capture precursor information of CO2 leakage based on microseismic monitoring data to make full preparations for handling CO2 leakage. Further set up passive sentinel monitoring mode and active precursor detection mode, conduct low-frequency monitoring for the stage with low probability of CO2 leakage, and conduct high-frequency monitoring for the stage with high probability of CO2 leakage, reduce the monitoring workload and data processing workload, and achieve accurate monitoring. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the vibration-gas coupling monitoring well of the present invention.

[0018] Figure 2 This is a schematic diagram of the vertical cross-section of the monitoring system for goaf areas in wells using the vibration-gas coupling monitoring method of the present invention.

[0019] Figure 3 This is a schematic diagram of the vertical cross-section of the well fracture zone monitoring system of the present invention, which is a gas-vibration coupling monitoring system.

[0020] Figure 4 This is a schematic diagram of the horizontal profile of the well fracture zone monitoring system of the present invention, which uses gas-vibration coupling.

[0021] Figure 5 This is a schematic diagram of the vertical cross-section of the aquifer monitoring system in the well using the vibration-gas coupling monitoring method of the present invention.

[0022] Figure 6This is a schematic diagram of the vertical cross-section of the seismic-gas coupling monitoring system for monitoring loose layers in wells according to the present invention.

[0023] Figure 7 This is a schematic diagram of the horizontal profile of the seismic-gas coupling monitoring system for monitoring loose layers in wells according to the present invention.

[0024] In the diagram: 1-Goaf monitoring system; 11-Goaf protection tubular system; 12-Connecting hole; 13-Baffle; 14-First CO2 integrated monitoring sensor; 15-Gas concentration sensor; 16-Water level sensor; 17-First water quality monitoring sensor; 18-Drainage pump; 19-Active wave excitation device; 2-Fractured zone monitoring system; 21-First inner tubular column; 22-Flexible breathable skin; 23-First connecting ring; 24-Second CO2 integrated monitoring sensor; 25-Extension device; 26-First micro-vibration detector; 3 - Aquifer monitoring system; 31-Second inner tubing string; 32-Porous outer tubing wall; 33-Second connecting ring; 34-CO2 concentration sensor; 35-Second water quality monitoring sensor; 36-pH-sensitive microcapsule; 37-Microcapsule tracer sensor; 38-Sampling pump; 4-Loose layer monitoring system; 41-Third inner tubing string; 42-First outer tubing wall; 43-Third connecting ring; 44-Third CO2 integrated monitoring sensor; 5-Second microseismic detector; 6-Connecting tubing string system; 7-Transmission pipeline; 8-Wellhead device. Detailed Implementation

[0025] The specific embodiments of the present invention will now be described in conjunction with the accompanying drawings.

[0026] Example 1

[0027] like Figures 1-7 As shown, this invention proposes a seismic-gas coupled monitoring well suitable for carbon dioxide geological sealing in mining spaces, comprising drilling from the surface to the goaf. During drilling, a goaf monitoring system 1 is installed at the goaf stratum, a fracture zone monitoring system 2 is installed at the fracture zone stratum, an aquifer monitoring system 3 is installed at the aquifer stratum, and a loose layer monitoring system 4 is installed at the loose layer stratum above the aquifer. In this application, the aquifer refers to an aquifer within the loose layer, and the goaf refers to the collapse zone.

[0028] like Figures 1-2As shown, the goaf monitoring system 1 includes a goaf protection pipe column system 11. The goaf protection pipe column system 11 includes a cylindrical pipe that is at least closed at the top. Several sets of connecting holes 12 are arranged on the side wall of the cylindrical pipe from bottom to top, with each set of connecting holes 12 evenly distributed around the circumference of the cylindrical pipe. A partition 13 is provided in the middle of the cylindrical pipe, dividing it into upper and lower chambers. The top wall of the upper chamber is equipped with a first CO2 integrated monitoring sensor 14 and a gas concentration sensor 15. The first CO2 integrated monitoring sensor 14 includes at least a CO2 concentration sensor. Preferably, it also includes a humidity sensor and a pressure sensor, so that the ambient temperature and humidity can be combined to determine whether there are abnormal changes in CO2 concentration, and the judgment of whether CO2 is leaking is more accurate. The lower cavity is equipped with a water level sensor 16, a first water quality monitoring sensor 17, a drainage pump 18 and an active wave excitation device 19. The water level sensor 16 is preferably a pressure-type liquid level sensor to obtain the water level in the goaf. The first water quality monitoring sensor 17 can at least obtain the pH value of the water in the goaf, so as to determine the CO2 concentration dissolved in the water in the goaf based on the pH value. The fissure water in the surrounding rock strata will flow into the goaf. The amount of CO2 dissolved in the water in the goaf can be calculated based on the area of ​​the goaf, the water level in the goaf and the CO2 concentration in the water in the goaf, so as to facilitate the analysis of the impact of the water in the goaf on the CO2 concentration. The goaf contains residual coal, and the residual coal and some broken gangue contain gas and continuously precipitate. The gas concentration sensor 15 is used to obtain the gas concentration in the goaf, so as to facilitate the analysis of the impact of the gas concentration on the CO2 concentration. When there is a lot of water accumulation in the goaf, the water is pumped to the ground by the drainage pump 18, and the amount of CO2 carried by the discharged water is analyzed to analyze its impact on the CO2 concentration; the water accumulation in the goaf is kept below the height of the partition 13.

[0029] like Figure 1 , Figures 3-4As shown, the fracture zone monitoring system 2 includes a fracture zone protection tubing system. The fracture zone protection tubing system includes a coaxially arranged circular tubular first inner tubing 21 and a flexible breathable skin 22. The top and bottom of the first inner tubing 21 and the flexible breathable skin 22 are connected by a first connecting ring 23, thus forming an air chamber. The air inlet channel of the air chamber is the flexible breathable skin 22. A second CO2 integrated monitoring sensor 24 is installed in the air chamber. The second CO2 integrated monitoring sensor 24 includes at least a CO2 concentration sensor, and preferably also includes a humidity sensor and a pressure sensor, thereby comprehensively considering ambient temperature and humidity to determine whether there are abnormal changes in CO2 concentration, making the determination of CO2 leakage more accurate. Inside the air chamber, in the first inner tubing... Several sets of telescopic devices 25 are arranged from top to bottom on the outer wall of the first inner tubing 21. Each set of telescopic devices 25 is evenly distributed around the circumference of the first inner tubing 21. The telescopic devices 25 are arranged radially, with the bottom end of the cylinder fixed to the outer wall of the first inner tubing 21. A first micro-vibration detector 26 is arranged at the top of the telescopic end. The first micro-vibration detector 26 and the flexible breathable skin 22 are pressed against the surrounding fracture zone drilling rock wall by radial thrust, thereby acquiring the micro-vibration signal generated by the activation movement such as fracture and rotation of the fracture zone rock strata. A radial support force acquisition device is arranged on the telescopic device 25 to control the telescopic device 25 to maintain a reasonable radial support force (neither too large nor too small) after the fracture zone rock strata generate activation movements such as fracture and rotation, so that the first micro-vibration detector 26 is stably pressed against the surrounding fracture zone drilling rock wall.

[0030] like Figure 1 , Figure 5 As shown, the aquifer monitoring system 3 includes an aquifer protection pipe column system. The aquifer protection pipe column system includes a coaxially arranged circular inner pipe column 31 and a porous outer pipe wall 32. The top and bottom of the second inner pipe column 31 and the porous outer pipe wall 32 are connected by a second connecting ring 33, thus forming a chamber. The water inlet channel of the chamber is the porous outer pipe wall 32. A CO2 concentration sensor 34, a second water quality monitoring sensor 35, a pH-sensitive microcapsule 36, a microcapsule tracer sensor 37, and a sampling pump 38 are installed in the chamber. The second water quality monitoring... Sensor 35 can at least obtain the pH value of the aquifer water, thereby determining the concentration of CO2 dissolved in the aquifer water based on the pH value; pH-sensitive microcapsules 36 act as chemical threshold switches, releasing specific tracers when a set CO2 concentration is dissolved in the aquifer water (when the acidity reaches a certain threshold), and microcapsule tracer sensor 37 is used to capture the specific tracers; the CO2 concentration sensor 34 is used to obtain the CO2 gas concentration in the aquifer water, indicating that CO2 has been saturated and dissolved in the aquifer water and CO2 gas has been incorporated into the aquifer water; the sampling pump 38 can sample the aquifer water and perform accurate detection in the laboratory.

[0031] like Figure 1 , Figures 6-7 As shown, the loose layer monitoring system 4 includes a loose layer protection pipe column system. This system comprises a coaxially arranged circular inner pipe column 41 and a first outer pipe wall 42. The top and bottom of the inner pipe column 41 and the outer pipe wall 42 are connected by a third connecting ring 43. Several sets of sensor slots are arranged from top to bottom on the outer side of the outer pipe wall 42, with each set evenly distributed circumferentially around the wall. A third CO2 integrated monitoring sensor 44 is installed in each slot. The third CO2 integrated monitoring sensor 44 includes at least a CO2 concentration sensor, and preferably also includes a humidity sensor and a pressure sensor. This allows for a comprehensive assessment of ambient temperature and humidity to determine if there are any abnormal changes in CO2 concentration, leading to more accurate detection of CO2 leaks. Since the loose layer itself contains a small amount of CO2 gas, which is affected by seasonal and diurnal variations, CO2 concentration benchmarks should be established for different seasons and diurnal conditions to reduce false anomalies caused by environmental interference in the loose layer.

[0032] Connecting tubing systems 6 are respectively installed between the fracture zone protection tubing system and the aquifer protection tubing system, and between the aquifer protection tubing system and the loose layer protection tubing system. Each connecting tubing system 6 includes a coaxially arranged circular inner tubing and a second outer tubing wall. The top and bottom of the inner and outer tubing are connected by a fourth connecting ring. The goaf protection tubing system 11 covers the entire goaf in height, the fracture zone protection tubing system covers the entire fracture zone in height, and the aquifer protection tubing system covers the entire aquifer in height. Preferably, the upper part of the aquifer protection tubing system is higher than the top surface of the aquifer, and the lower part is lower than the bottom surface of the aquifer. The monitoring well, from bottom to top, consists of a sealed connection between the goaf protection tubing system 11 and the fracture zone protection tubing system. The monitoring well comprises a lower connecting tubing system 6, an aquifer protection tubing system, an upper connecting tubing system 6, and a loose layer protection tubing system. The upper part of the loose layer protection tubing system reaches the ground surface. A wellhead device 8 is installed at the top of the monitoring well. The inner tubing of the fracture zone protection tubing system, the lower connecting tubing system 6, the aquifer protection tubing system, the upper connecting tubing system 6, and the loose layer protection tubing system forms a sealed pipeline cavity. A transmission pipeline 7 is installed in the pipeline cavity. One end of the cable in the transmission pipeline 7 extends to the ground surface and the other end connects to the sensors, active wave excitation device 19, telescopic device 25, and first microseismic detector 26 in the monitoring well. The other end of the pipe in the transmission pipeline 7 extends to the ground surface and connects to the water pump in the monitoring well. Several second microseismic detectors 5 are also installed on the ground surface corresponding to the goaf. In this embodiment, the well diameters of the monitoring wells corresponding to the goaf protection tubing system 11, the fracture zone protection tubing system, and the lower connecting tubing system 6 are the same and relatively small, while the well diameters of the monitoring wells corresponding to the aquifer protection tubing system, the upper connecting tubing system 6, and the loose layer protection tubing system are the same and relatively large.

[0033] Example 2

[0034] This invention also provides a method for constructing and monitoring a monitoring well, used in the construction of the seismic-gas coupled monitoring well suitable for geological carbon dioxide sequestration in mining spaces, as described in Example 1. Figures 1-7 As shown, the specific steps include the following.

[0035] S1: Use a large-size drill bit with casing assembly for the first drilling operation, penetrating the loose layer and its internal aquifer, drilling to 2-3 meters into the intact rock strata; during the drilling process, the casing is lowered synchronously with the drill bit to physically seal the easily collapsible loose layer and the easily leaking aquifer; replace with a smaller drill bit and drilling assembly, and lower it coaxially from inside the casing in the first drilling operation to start the second drilling operation, drilling to the bottom of the goaf.

[0036] S2: In the second section, from bottom to top, the goaf monitoring system 1, the fracture zone monitoring system 2, and the lower connecting pipe column system 6 are sequentially lowered, and the goaf protection pipe column system 11, the fracture zone protection pipe column system, and the lower connecting pipe column system 6 are sealed together, thereby forming a sealed pipeline cavity in the inner pipe column; the cables in the transmission pipeline 7 are connected to the sensors, active wave excitation device 19, telescopic device 25, and first micro-vibration detector 26 in the monitoring well, and the pipeline in the transmission pipeline 7 is connected to the drainage pump 18.

[0037] S3: In the first well, the aquifer monitoring system 3, the upper connecting tubing system 6, and the loose layer monitoring system 4 are sequentially lowered from bottom to top, and the lower connecting tubing system 6, the aquifer protection tubing system, the upper connecting tubing system 6, and the loose layer protection tubing system are sealed together to form a sealed pipeline cavity in the inner tubing; the cables in the transmission pipeline 7 are connected to the remaining sensors in the monitoring well, and the pipelines in the transmission pipeline 7 are connected to the sampling pump 38; the wellhead device 8 is installed, and the transmission pipeline 7 is led out from the wellhead device 8, and several second microseismic detectors 5 are set on the surface corresponding to the goaf.

[0038] S4: After CO2 geological sealing in the goaf, the monitoring well is used to monitor CO2 leakage. Under normal circumstances, the monitoring mode is set to passive sentinel monitoring mode: each sensor samples at low frequency, the first microseismic detector 26 and the second microseismic detector 5 are in the all-time open state, and the microseismic detectors passively receive the microseismic signals generated by the active motion of rock strata such as fracturing and rotation, and determine the magnitude, location and moment tensor. When the microseismic signal indicates that the rock strata have generated active motion such as fracturing and rotation, each sensor starts high-frequency sampling. The active precursor detection mode is activated at fixed intervals: the active wave excitation device 19 located at the bottom of the goaf is activated to periodically impact the goaf floor, generating a stable elastic wave signal. The first microseismic detector 26 and the second microseismic detector 5 receive the direct wave and transmitted wave generated by the active wave excitation device 19. Using wave velocity tomography technology, the dynamics of fracture development in the strata, especially in the fracture zone and the goaf strata, are inverted. When active movements such as rock strata fracture and rotation are detected, each sensor starts high-frequency sampling.

[0039] S5: CO2 Leakage Early Warning and Handling: Calculate the amount of CO2 contained in the goaf water based on the area of ​​the goaf, the height of the goaf water obtained by the water level sensor 16, and the CO2 concentration dissolved in the goaf water obtained by the first water quality monitoring sensor 17, and analyze the impact of the goaf water on the CO2 concentration; analyze the impact of the gas concentration on the CO2 concentration based on the gas concentration sensor 15; considering the influence of goaf water and gas, determine whether there are abnormal changes in the goaf CO2 concentration based on the first CO2 comprehensive monitoring sensor 14, and determine whether there is a CO2 leak; when there is a large amount of goaf water, drain the goaf water to the ground using the drainage pump 18, and analyze the amount of CO2 carried by the drained goaf water, and further analyze its impact on the CO2 concentration; keep the goaf water level below the height of the partition 13.

[0040] The second CO2 integrated monitoring sensor 24 determines whether there are abnormal changes in CO2 concentration in the fracture zone and whether there is a CO2 leak. By controlling the telescopic device 25 to always maintain a reasonable radial support force (neither too large nor too small), the first microseismic detector 26 is stably abutted against the surrounding fracture zone drilling rock wall, ensuring the stable operation of the fracture zone monitoring system 2.

[0041] The second water quality monitoring sensor 35 acquires the CO2 concentration dissolved in the aquifer water and determines whether there are any abnormal changes, thus determining whether there is a CO2 leak. The microcapsule tracer sensor 37 captures specific tracers to further determine whether there is a CO2 leak, and a comprehensive verification is performed. In addition, if the CO2 concentration sensor 34 detects the presence of CO2 gas in the aquifer, indicating a CO2 leak, the aquifer water is sampled by the sampling pump 38 and accurately tested in the laboratory to further determine whether there is a CO2 leak.

[0042] The third CO2 integrated monitoring sensor 44 is used to determine whether there are abnormal changes in CO2 concentration and to determine whether there is a CO2 leak. The determination is based on the CO2 concentration benchmark under different seasons and day and night conditions. Based on the goaf, fracture zone, aquifer, and loose layer, the location of CO2 leakage can be accurately determined, so as to take more accurate leak repair measures.

[0043] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A seismic gas coupling monitoring well suitable for carbon dioxide geological storage in a mining space, characterized in that, This includes drilling from the surface to the goaf; during drilling, monitoring systems are installed in the goaf, fracture zone, aquifer, and loose strata above the aquifer; the goaf monitoring system includes a goaf protection pipe column system; the goaf protection pipe column system includes a cylindrical pipe that is at least closed at the top, with connecting holes on the sidewalls of the cylindrical pipe, and a partition in the middle dividing it into upper and lower chambers. The top wall of the upper chamber is equipped with a first CO2 integrated monitoring sensor and a gas concentration sensor, and the lower chamber is equipped with a water level sensor, a first water quality monitoring sensor, a drainage pump, and... The active wave excitation device and the first water quality monitoring sensor are capable of acquiring at least the pH value of the water accumulated in the goaf. The fracture zone monitoring system includes a fracture zone protection tubing system. The fracture zone protection tubing system includes a cylindrical first inner tubing and a flexible, breathable skin. The top and bottom of the first inner tubing and the flexible, breathable skin are connected by a first connecting ring, thus forming an air chamber. The air inlet channel of the air chamber is the flexible, breathable skin. A second CO2 integrated monitoring sensor is installed in the air chamber. A telescopic device is installed on the outer wall of the first inner tubing. The cylinder is arranged radially, with its bottom end fixed to the outer wall of the first inner tube column, and a first micro-vibration detector installed at the top of the telescopic end; a radial support force acquisition device is installed on the telescopic device; the aquifer monitoring system includes an aquifer protection tube column system, which includes a coaxially arranged circular tubular second inner tube column and a porous outer tube wall. The top and bottom of the second inner tube column and the porous outer tube wall are connected by a second connecting ring, thus forming a chamber. The water inlet channel of the chamber is the porous outer tube wall; a device is installed in the chamber. The system includes a CO2 concentration sensor, a second water quality monitoring sensor, pH-sensitive microcapsules, a microcapsule tracer sensor, and a sampling pump; the loose layer monitoring system includes a loose layer protection pipe column system, which consists of a coaxially arranged circular inner pipe column and a first outer pipe wall, with the top and bottom of the inner pipe column and the first outer pipe wall connected by a third connecting ring; a sensor slot is provided on the outside of the first outer pipe wall, and a third CO2 integrated monitoring sensor is installed in the sensor slot; a second microseismic detector is also installed on the surface corresponding to the goaf.

2. The seismo-atmospheric coupling monitoring well of claim 1, wherein, The monitoring well consists of, from bottom to top, a sealed goaf protection tubing system, a fracture zone protection tubing system, a lower connecting tubing system, an aquifer protection tubing system, an upper connecting tubing system, and a loose layer protection tubing system. The connecting tubing system includes a coaxially arranged circular inner tubing and a second outer tubing wall. The top and bottom of the inner tubing and the outer tubing wall are connected by a fourth connecting ring. A wellhead device is installed at the top of the monitoring well.

3. The gas-vibration coupling monitoring well according to claim 2, characterized in that, The inner tubing of the fracture zone protection tubing system, the lower connecting tubing system, the aquifer protection tubing system, the upper connecting tubing system, and the loose layer protection tubing system forms a sealed pipeline cavity. A transmission pipeline is installed in the pipeline cavity. One end of the cable in the transmission pipeline extends to the ground surface and the other end connects to the sensors, active wave excitation device, telescopic device, and first microseismic detector in the monitoring well. The other end of the pipeline in the transmission pipeline extends to the ground surface and connects to the water pump in the monitoring well.

4. The seismic-gas coupling monitoring well according to claim 3, characterized in that, The first, second, and third CO2 integrated monitoring sensors all include a CO2 concentration sensor, a humidity sensor, and a pressure sensor.

5. The seismic-gas coupling monitoring well according to claim 4, characterized in that, The second water quality monitoring sensor can at least obtain the pH value of the aquifer water; the pH-sensitive microcapsule acts as a chemical threshold switch, releasing a specific tracer when a set CO2 concentration is dissolved in the aquifer water, and the microcapsule tracer sensor is used to capture the specific tracer; the CO2 concentration sensor is used to obtain the CO2 gas concentration in the aquifer water; and the sampling pump can sample the aquifer water.

6. A method for constructing and monitoring a monitoring well, used for constructing the seismic-gas coupling monitoring well as described in claim 5, suitable for geological carbon dioxide sequestration in mining spaces, characterized in that, Includes the following steps: S1: First drilling, penetrating the loose layer and its internal water-bearing layer. During the drilling process, the casing is lowered synchronously with the drill bit; Second drilling, drilling to the bottom of the goaf. S2: In the second section, from bottom to top, the goaf monitoring system, the fracture zone monitoring system, and the lower connecting pipe column system are successively installed and connected to the transmission pipeline; S3: In the first well, from bottom to top, the aquifer monitoring system, the upper connecting tubing system, and the loose layer monitoring system are sequentially installed and connected to the transmission pipeline; the wellhead device is installed, and a second microseismic detector is set on the surface corresponding to the goaf. S4: After CO2 geological sealing is carried out in the goaf area, the monitoring well is operated to monitor CO2 leakage; S5: CO2 leak early warning and handling.

7. The monitoring well construction and monitoring method according to claim 6, characterized in that, In step S4, under normal circumstances, the monitoring mode is set to passive sentinel monitoring mode: each sensor samples at low frequency, the first microseismic detector and the second microseismic detector are always on, and the microseismic detector passively receives the microseismic signals generated by the activation movement of the rock layer. When the microseismic signal indicates that the rock layer has generated activation movement, each sensor starts high-frequency sampling. Active precursor detection mode is activated at fixed intervals: the active wave excitation device located at the bottom of the goaf is activated to periodically impact the goaf floor, generating stable elastic wave signals. The first and second microseismic detectors receive the direct and transmitted waves generated by the active wave excitation device. Using wave velocity tomography, the dynamics of fracture development in the fracture zone and the strata of the goaf are inverted and generated. When the activation movement of the rock strata is detected, each sensor starts high-frequency sampling.

8. The monitoring well construction and monitoring method according to claim 7, characterized in that, In step S5, the amount of CO2 contained in the goaf water is calculated based on the area of ​​the goaf, the height of the goaf water obtained from the water level sensor, and the CO2 concentration dissolved in the goaf water obtained from the first water quality monitoring sensor. The impact of the goaf water on the CO2 concentration is analyzed. The impact of the gas concentration on the CO2 concentration is analyzed based on the gas concentration obtained from the gas concentration sensor. Considering the effects of goaf water and gas, the CO2 concentration in the goaf is assessed for abnormal changes based on the first CO2 comprehensive monitoring sensor to determine if there is a CO2 leak. When there is a large amount of goaf water, it is drained to the ground using a drainage pump, and the amount of CO2 carried by the drained water is analyzed to further analyze its impact on the CO2 concentration. The height of the goaf water is kept below the height of the partition. The second CO2 comprehensive monitoring sensor... The system uses a device to determine if there are abnormal changes in CO2 concentration in the fracture zone, thus assessing whether there is a CO2 leak. It controls the telescopic device to maintain a reasonable radial support force. A second water quality monitoring sensor acquires the CO2 concentration dissolved in the aquifer water and determines if there are any abnormal changes, again assessing whether there is a CO2 leak. A microcapsule tracer sensor captures specific tracers to further determine if there is a CO2 leak, providing comprehensive verification. Furthermore, if the CO2 concentration sensor detects the presence of CO2 gas in the aquifer, indicating a CO2 leak, a sampling pump is used to sample the aquifer water, and precise testing is conducted in the laboratory to further determine if there is a CO2 leak. A third comprehensive CO2 monitoring sensor determines if there are any abnormal changes in CO2 concentration, assessing whether there is a CO2 leak, referencing CO2 concentration benchmarks under different seasons and day / night conditions.

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