A coal fire crack identification and plugging method and system by injection and exploration separation

Abstract

The application discloses a coal fire crack identification and plugging method and a plugging system, relates to the fields of coalfield drilling and coalfield fire area treatment, and forms a drilling network for the coal fire area construction, carries out joint electric-magnetic scanning on the selected observation hole, obtains data vectors before and after the injection of the tracer medium, reconstructs the three-dimensional conductivity and magnetic permeability distribution of the underground cracks, obtains the three-dimensional spatial distribution of the cracks, and determines the grouting amount of the tracer plugging material; the system integrates the heat dissipation drilling, crack identification, plugging and control depth, and completes the whole process of high-temperature pore forming-tracer injection-electromagnetic scanning-inversion imaging-targeted grouting-effect verification. The application realizes the joint inversion of the conductivity and magnetic permeability double parameters, solves the problems that the single electric method / magnetic method detection cannot distinguish the natural geological anomaly from the crack channel and the inversion result has many false anomalies, realizes the true three-dimensional and high-resolution stereoscopic imaging of the spatial distribution and connectivity of the cracks, and provides the high-precision target point for the targeted grouting.

Description

Technical Field

[0001] This invention relates to coalfield drilling technology, belonging to the field of coalfield fire zone management, and specifically to a method and system for identifying and sealing coal fire cracks through injection-exploration separation. Background Technology

[0002] Coalfield fires are highly destructive geological hazards, characterized by their wide burning range, long duration, and difficulty in control. Currently, the main control technology approach combines stripping, water injection, drilling, grouting, and covering. However, the following problems exist in practical applications:

[0003] 1. Drilling is a crucial step before underground grouting. Due to the high temperature inherent in coalfield fires, such as surface temperatures in shallow fire zones often exceeding 200°C, the local hotspots generated by the high-speed friction between the drill bit and the high-temperature rock layer during drilling can exceed 500°C. This high-temperature drilling environment directly leads to: 1) Rapid deterioration of the drill bit cutting teeth material, decreased hardness, and increased wear, requiring frequent replacements, resulting in low operational efficiency and high costs; 2) The high-temperature drill bit becomes an ignition source, easily igniting the coal body around the borehole, causing secondary disasters and making the remediation work counterproductive; Traditional high-pressure water injection cooling methods, although able to temporarily lower the temperature, cause a large amount of cold water to invade the high-temperature rock layer, drastically altering its physical and mechanical properties, which can easily induce major safety accidents such as landslides.

[0004] 2. There is a serious lack of precision in the underground grouting and sealing process. Existing treatment techniques have gradually evolved into shallow oxygen control and asphyxiation to extinguish deep fire sources. For example, Chinese invention patent CN110454211A discloses a method for treating shallow oxygen control and asphyxiation in coalfield fire areas where mine fires and surface fires coexist. The method involves injecting filling material into shallow treatment boreholes to fill cavities, pre-cooling the high-temperature shallow areas of the fire zone, and then performing layered sealing in the shallow areas, while simultaneously monitoring the fire zone. However, this method relies on judging the sealing range from the shallow macroscopic temperature field and does not specifically image the fracture network. It cannot identify the spatial distribution and seepage paths of hidden fractures, resulting in grouting that remains largely unpredictable and makes it difficult to accurately seal critical oxygen supply channels.

[0005] Currently, fracture detection mainly employs geophysical techniques, including electrical resistivity, magnetic methods, and acoustic methods. Fracture detection is primarily applied in groundwater extraction, reservoir oil and gas extraction, geological exploration, hydrogeological and environmental monitoring research, but these are all passive detection methods, lacking a specific approach for detecting fractures in coal fires. Chinese invention patent CN121409762A, entitled "An Active Enhanced Detection Test System and Method for Fractures in Coal Fire Zones," discloses that by constructing four modules—fracture evolution, detection, intervention, and intelligent feedback—it achieves simultaneous multi-physics field monitoring and four-dimensional visualization of the fracture evolution process in coal fire zones, providing a scientific basis for precise fracture delineation and targeted sealing. However, this scheme is used for laboratory mechanism research and method verification. It lacks a nonlinear characteristic fracture inversion method for tracer strong contrast anomaly. At the same time, its application scenario is limited to small-scale coal and rock specimens and does not involve engineering drilling operations in real field high-temperature fire zone environments. Furthermore, it lacks a multi-coupling design of "on-site drilling - detection inversion - quantitative sealing - effect verification", which makes it difficult to support the engineering logic of "exploration before injection and sealing as needed" on-site. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for identifying and sealing coal fire cracks by separating injection and exploration. This sealing method significantly improves the accuracy and reliability of hidden crack identification, realizes the joint inversion of electrical conductivity and magnetic permeability, and can solve the problems of single electrical / magnetic detection being unable to distinguish between natural geological anomalies and crack channels, having many false anomalies in the inversion results, and having poor positioning accuracy. It achieves true three-dimensional, high-resolution stereo imaging of crack spatial distribution and connectivity, providing high-precision target points for targeted grouting.

[0007] To achieve the above objectives, a method for identifying and sealing coal fire cracks using injection-probe separation specifically includes the following steps:

[0008] S1 forms a borehole network including injection holes and observation holes for construction in coal fire areas;

[0009] Select the borehole located in the center of the expected crack development area as the injection hole, and at least two adjacent boreholes around it as observation holes;

[0010] S2, Select at least one observation well and perform a combined electromagnetic scanning (EMS) scan. This combined EMS scan is a well-to-surface combined EMS scan and / or a cross-well combined EMS scan to acquire a background field multi-physical quantity data vector including potential and magnetic field data prior to injection. ;

[0011] A tracer medium with significant differences in electrical conductivity and magnetic permeability is then continuously injected into the injection well. Under pressure, the tracer medium moves along the crack network. During or after injection, a combined electromagnetic scan is performed again to acquire the multi-physics data vector of the excitation field. ;

[0012] S3-1, Defining a Two-Parameter Model for Subsurface Media Construct an inversion objective function that includes a data fitting term and a model regularization term. :

[0013] S3-2, the Gauss-Newton iterative method is used to solve the nonlinear inversion problem of step S3-1, and the three-dimensional conductivity and magnetic permeability distribution of the underground fractures are reconstructed to calculate the final model parameter variation distribution. ; The final output model, This is the initial background model; The non-zero region in space directly characterizes the three-dimensional spatial distribution of cracks filled with tracer medium;

[0014] S4. Based on the three-dimensional spatial distribution of the crack, the amount of tracer sealing material to be injected is determined, and tracer sealing material with pre-placed conductive and magnetic components is injected into the sealing target point to verify the grouting sealing effect.

[0015] In some examples of the present invention, in step S3-1, an inversion objective function comprising a data fitting term and a model regularization term is constructed. :

[0016]

[0017] in, The parameter variation distribution of each grid cell in the final underground three-dimensional space is represented by non-zero regions, which indicate cracks filled by the tracer medium.

[0018] A data weighting matrix is ​​used to standardize the signal-to-noise ratio differences among different observation data;

[0019] The joint sensitivity Jacobian matrix is ​​formed by combining the potential partial derivative matrix of the high-density electrical resistivity method and the magnetic field partial derivative matrix of the well magnetic measurement.

[0020] This is a regularization factor used to adjust the weight balance between the degree of data fit and the smoothness of the model;

[0021] This is the roughness matrix of the model;

[0022] The square of the Euclidean norm of a vector is used to quantify the magnitude of the residual.

[0023] The time-shifted differential observation data vector is calculated using the following formula: ;

[0024] Step S3-2 specifically includes the following iterative steps:

[0025] S3-2-1, Iteration Initialization: Set the iteration count... ; Initial background model As the initial model for inversion, the residual convergence threshold and the maximum number of iterations are set;

[0026] S3-2-2, Dynamic Update of Forward Response and Joint Sensitivity Jacobian Matrix: Based on the current... The model of the next iteration Numerical simulations were performed using multiphysics forward modeling operators to calculate the theoretical response of the current model. At the same time, the current joint sensitivity Jacobian matrix is ​​recalculated. ;

[0027] S3-2-3, Construct a modified regularized normal equation system;

[0028] Introducing model correction amount To construct a system of normal equations containing double difference residuals:

[0029]

[0030] in, For the first Model correction amount in each iteration;

[0031] For the first The current joint sensitivity Jacobian matrix of the next iteration The transpose of the matrix, Weighted matrix of data The transpose of the matrix;

[0032] The theoretical response of the initial background model;

[0033] S3-2-4, Solve for the model correction:

[0034] By iteratively solving the normal equations in step S3-2-3 using the conjugate gradient least squares method, the model correction for the current iteration step can be obtained. ;

[0035] S3-2-5, Model parameter update:

[0036] The obtained model correction amount Overlay onto the current model to update the subsurface medium parameters:

[0037]

[0038] in, For the next underground medium parameters, These are the current underground medium parameters; The iterative search step size is dynamically determined using a line search algorithm to ensure the inversion of the objective function. It shows a monotonically decreasing trend;

[0039] S3-2-6, Convergence Condition Determination and Result Output:

[0040] Calculate the root mean square error of the data residuals in the current iteration and the norm of the model correction. If it is less than the set convergence threshold, or the number of iterations... Once the maximum number of iterations is reached, the stopping condition is triggered, the iteration loop ends, and the final two-parameter model of the underground medium is output. If the stopping condition is not met, then let Return to step S3-2-2 and enter the next loop;

[0041] S3-2-7, Extracting abnormal crack distribution:

[0042] Based on the final output model Calculate the final distribution of model parameter changes. .

[0043] In some examples of the present invention, in S3-2-1, the initial background model The construction process is as follows: The background field multi-physical quantity data vector... As input, combining prior information from the geological borehole columnar section and electrical / magnetic logging curves of the area, a three-dimensional initial physical property distribution grid of the subsurface space is established using a conventional smoothing inversion algorithm. Each grid is assigned initial electrical conductivity and magnetic permeability values, thus forming the initial background model. ;

[0044] In step S3-2-2, the theoretical response of the current model Current joint sensitivity Jacobian matrix The construction process is as follows: establish the governing equations of the DC steady electric field and the static magnetic field in the three-dimensional medium respectively, and use them as physical forward modeling operators;

[0045] For high-density electrical resistivity tomography (EDT), the Poisson equation describing the steady-state electric field distribution is established:

[0046]

[0047] in, For divergence operators, For gradient operators, For electrical conductivity, Potential, conductivity With potential All change with the three-dimensional spatial coordinates; The current density supplied to the point power source. For current intensity, For the Dirac function, The position vector of the point power source; Let be the position vector of any point in three-dimensional space;

[0048] For in-well magnetic measurements, an integral equation for the static magnetic field describing the magnetization anomaly field is established:

[0049]

[0050] in, This is the spatial magnetic anomaly vector. Permeability of free space; The magnetization intensity;

[0051] The position vector of the observation point With the underground field source point location vector The difference is such that its modulus length is ; Unit vector, ; The integral volume of the three-dimensional space containing the underground anomaly;

[0052] The Poisson equation and the static magnetic field integral equation for a stable electric field distribution are discretized and solved using the finite element method or finite volume method to obtain the theoretical response of the current model. The partial derivative matrix is ​​extracted to update the current joint sensitivity Jacobian matrix. The partial derivative matrix is ​​formed by splicing the potential partial derivative submatrix of the current high-density electrical resistivity tomography and the magnetic field partial derivative submatrix of the current well magnetic survey.

[0053] In some examples of the present invention, in step S4, the amount of grout injected with the tracer sealing material... The calculation formula is:

[0054]

[0055]

[0056]

[0057] in, The slurry diffusion loss coefficient; Inverted volume of the crack space for effective filling of the tracer medium;

[0058] The total number of 3D meshes for imaging. For the index number of the grid cell, ;

[0059] For the first The geometric volume of a single element in a grid;

[0060] For the first The equivalent crack porosity of each grid is calculated based on the Archie formula;

[0061] For the first The change in inverted conductivity of each grid;

[0062] The conductivity of the tracer medium; This represents the cementation index.

[0063] In some examples of the present invention, step S4 specifically includes the following steps:

[0064] S4-1, Grouting and Sealing: Based on the three-dimensional spatial distribution of cracks obtained in step S3, key crack channels are identified as grouting and sealing target points, and tracer sealing materials with pre-placed conductive and magnetic components are injected into the sealing target points.

[0065] S4-2, Re-scanning and Inversion: After the tracer sealing material has solidified, repeat step S2 to obtain multi-physical quantity data vectors including potential data and magnetic field data after sealing, and perform inversion imaging;

[0066] S4-3, Verification of Blocking Effectiveness:

[0067] The latest inversion imaging results are compared with the actual grouting project parameters for judgment:

[0068] Validity is determined as follows: If a dual-physics anomaly matching the electromagnetic response characteristics of the tracer sealing material is detected in the three-dimensional region of the original crack target, and the inversion volume is obtained through the voxel integral formula, then the inversion is valid. Compared with the actual recorded grouting volume If the error between the two is within the set allowable threshold range, the grouting and sealing are deemed effective.

[0069] Invalidity and Anomaly Handling: If any of the following situations occur: A. No obvious electromagnetic anomaly is detected in the target's three-dimensional region; B. The electromagnetic anomaly region deviates significantly from the set blocking target point; C. The inverted volume... If the ratio of the actual grouting volume to the total grouting volume is less than 0.7, the grouting and sealing are deemed ineffective.

[0070] A coal fire crack identification and sealing system based on injection and detection separation, the system being used to implement the aforementioned coal fire crack identification and sealing method based on injection and detection separation, comprising:

[0071] A drilling unit with heat-dissipating drill rods is used for drilling a borehole network including injection holes and observation holes in coal fire areas.

[0072] The crack identification unit includes an injection component for injecting a tracer medium into the injection hole, an electromagnetic detection component for performing a combined electromagnetic scan into the observation hole to obtain potential and magnetic field data, and an analysis component for building a model to obtain the three-dimensional spatial distribution of the crack and verifying the effectiveness of the sealing.

[0073] The plugging unit has plugging components for injecting tracer plugging material into the borehole;

[0074] The control unit, connected to the drilling unit, fracture identification unit, and sealing unit, controls the actions of each unit: first, it controls the drilling unit to drill in the coal fire area to form a borehole network; after the borehole network is completed, the control unit controls the electromagnetic detection component to obtain the background electromagnetic response data vector before injection; then, it controls the injection component to continuously inject the tracer medium into one or more injection holes; during or after injection, the control unit controls the electromagnetic detection component to obtain the excitation field electromagnetic response data vector; after the analysis component constructs a model to obtain the three-dimensional spatial distribution of the fracture, the control unit controls the sealing unit to inject tracer sealing material into the borehole.

[0075] In some examples of the present invention, a shallow treatment unit is also included, configured as an ecological substrate for surface construction to isolate oxygen after deep fire extinguishing in coalfield fire zones;

[0076] The ecological matrix is ​​mixed in parts by weight, including: 15-25 parts of straw-based hydrogel microspheres, 30-40 parts of red mud-biochar composite particles, 20-30 parts of decomposed coal gangue powder, and 2-5 parts of arbuscular mycorrhizal fungi encapsulation slow-release agent.

[0077] After mixing the ecological substrate with water, spread it on the surface of the fire area with a thickness of ≥20cm.

[0078] In some examples of the present invention, the drilling unit has a heat-dissipating drill rod; the heat-dissipating drill rod includes:

[0079] The drill rod and drill bit are connected to each other. The drill bit has a closed heat dissipation cavity filled with phase change material.

[0080] The cooling component has an energy storage box located inside the drill pipe and at least one condenser located inside the energy storage box;

[0081] The energy storage tank is fixedly arranged and stores liquid cryogenic working fluid inside. The condenser is connected to the drive component and is driven to move radially. Under the action of the drive component, when the temperature inside the drill pipe exceeds a first temperature threshold, the condenser moves radially to a position in contact with the energy storage tank. When the temperature inside the drill pipe drops below a second temperature threshold, the condenser moves radially to a position detached from the energy storage tank. Alternatively, when the drill pipe rotation speed exceeds a first rotation speed threshold, the condenser moves radially to a position in contact with the energy storage tank. When the drill pipe rotation speed drops below a second rotation speed threshold, the condenser moves radially to a position detached from the energy storage tank. Wherein, the first temperature threshold is greater than the second temperature threshold, and the first rotation speed threshold is greater than the second rotation speed threshold.

[0082] The condenser and the heat dissipation chamber are connected by an evaporation pipe and a return pipe to form a closed loop, which allows the phase change material to evaporate from the heat dissipation chamber into the condenser and then flow back into the heat dissipation chamber.

[0083] In some examples of the present invention, the drive component has a support cylinder, a support rod, and a shape memory alloy component;

[0084] One end of the support rod moves inside the support cylinder and contacts the elastic element, while the other end is fixedly connected to the condenser box.

[0085] The support cylinder is equipped with an elastic element, which contacts the inner wall of the support cylinder and the support rod. Under the action of the elastic element, the support rod bears the elastic force toward the drill rod axis. Under the action of centrifugal force, the support rod moves to compress the elastic element.

[0086] The shape memory alloy component is located near the drill rod axis. One end of the shape memory alloy component is fixed and the other end is fixedly connected to the support cylinder. The drill bit is equipped with a heat-conducting plate. One end of the heat-conducting plate extends and connects to the shape memory alloy component. When the temperature reaches the first temperature threshold, the shape memory alloy component is heated and elongates.

[0087] or:

[0088] The drill bit is equipped with a temperature sensor, and the drill rod end is equipped with an angular velocity sensor for sensing the drill rod rotation speed. The driving component is a driving rod, which is fixed inside the drill rod.

[0089] The wires of the temperature sensor, angular velocity sensor, and drive rod are first led out through an electric slip ring and then connected to the controller, which controls the movement of the drive rod.

[0090] In some examples of the present invention, the central tube is a hollow structure and is coaxially located inside the drill pipe and drill bit;

[0091] The drill rod includes an inner drill rod and an outer drill rod, with an annular cavity formed between the inner drill rod and the outer drill rod;

[0092] The inner drill rod is provided with a secondary vent hole that communicates with the annular cavity. The lower end of the annular cavity is provided with a main vent hole that communicates with the outside, and the upper end is connected to the first high-pressure air source through a first rotary joint. The main vent hole is inclined and its lower end faces the drill bit.

[0093] The energy storage box is located inside the inner drill pipe, and a pressure relief valve connected to the auxiliary vent is installed at the upper end;

[0094] The cryogenic working fluid is liquid nitrogen;

[0095] The central tube is equipped with a cap at one end of the drill bit and can be switched to the slag discharge box and the second high-pressure gas source at the other end of the drill rod via a second rotary joint.

[0096] The end cap is configured to open the central tube port when subjected to pressure from below and close the central tube port when subjected to pressure from above.

[0097] The controller controls the inlet pressure of the first high-pressure gas source and the second high-pressure gas source.

[0098] Compared with existing technologies, this method for identifying and sealing coal fire cracks through injection and detection separation has the following advantages:

[0099] 1. Adopting an injection-probe separation active tracer detection mode improves the accuracy of hidden crack detection;

[0100] The present invention employs a hole-tracing-detection mode, which actively injects a dual-property tracer medium with both high conductivity and high magnetic permeability into the fracture. This artificially amplifies the difference in physical properties between the fracture and the surrounding rock by more than an order of magnitude, suppressing the background interference of natural strata from the physical source. This significantly improves the accuracy and reliability of hidden fracture identification and avoids the influence of background interference such as pyromorphic rocks and aquifers on passive detection.

[0101] 2. Joint inversion of electromagnetic dual physics fields eliminates the non-uniqueness of single physics field inversion;

[0102] This invention combines the DC electric field Poisson equation and the static magnetic field integral equation using a dual-property tracer medium to construct a joint sensitivity Jacobian matrix composed of potential partial derivative submatrices and magnetic field partial derivative submatrices. This enables joint inversion of both electrical conductivity and magnetic permeability, solving the problems of single electrical / magnetic methods failing to distinguish between natural geological anomalies and fracture channels, resulting in numerous false anomalies and poor positioning accuracy. Furthermore, by employing well-to-surface / cross-hole joint dual-field collaborative detection and introducing a dual-difference Gauss-Newton iterative normal equation system, this invention accurately solves the nonlinear inversion problem of tracing strong-contrast anomalies, achieving true three-dimensional, high-resolution stereo imaging of fracture spatial distribution and connectivity, and providing high-precision target points for targeted grouting.

[0103] 3. Establish a quantitative calculation system for crack volume to achieve precise targeted grouting;

[0104] This invention is based on the three-dimensional spatial distribution of cracks. The change in crack conductivity obtained by inversion is converted into the equivalent crack porosity of a single grid using the Archie formula. Then, the equivalent connected total volume of the crack is accurately calculated by three-dimensional voxel integration. Combined with the diffusion loss coefficient, the design grouting volume is automatically output, realizing exploration before grouting and sealing as needed. This greatly improves the sealing density and avoids the waste of materials caused by relying on manual experience to estimate the grouting volume in traditional coal-fired grouting.

[0105] 4. Forming a fully intelligent closed loop of "detection-injection-testing-adjustment" to reduce the risk of fire reignition in the fire zone;

[0106] The tracer sealing material after solidification is scanned again. By comparing the inverted volume with the actual grouting volume in a quantitative and intelligent manner, the material can be directly and visually verified to ensure that it accurately fills the target crack. In the event of extreme conditions such as grout leakage, the material can automatically track the leakage path and generate a correction and re-grouting scheme to adjust the mix ratio and supplement the borehole, thus achieving closed-loop treatment throughout the entire process.

[0107] A coal fire crack identification and sealing system with injection and detection separation has the following advantages:

[0108] 1. Deeply integrate the four major units of heat dissipation drilling, crack identification, sealing and control, with data interconnection and coordinated actions, to automatically complete the entire process of "high temperature hole formation - tracer injection - electromagnetic scanning - inversion imaging - targeted grouting - effect verification", and realize intelligent closed-loop management and control of coal fire treatment;

[0109] 2. Set up shallow treatment units. After the deep fire is extinguished, use solid waste-based pre-mineralized ecological matrix prepared by straw-based hydrogel microspheres and red mud-biochar composite particles to spread on the ground. This not only builds a dense oxygen barrier to prevent reignition, but also quickly improves the soil microenvironment in the fire area that is high-temperature acidified and barren and degraded, and actively promotes the establishment of vegetation roots, so as to realize the integrated implementation of coalfield disaster management and ecosystem restoration.

[0110] 3. Drilling units have the following advantages:

[0111] 3-1, to achieve safe drilling in high-temperature fire zones without water cooling, reducing the risk of secondary disasters;

[0112] By using a closed-loop phase change circulation system consisting of a built-in phase change heat dissipation chamber in the drill bit and a deep cryogenic energy storage condensation box in the drill pipe, continuous and efficient cooling of the drill bit is achieved, avoiding geological disasters such as sudden cooling and heating of rock mass and landslides caused by the intrusion of high-temperature rock layers by traditional high-pressure water injection.

[0113] 3-2, Temperature-speed dual-parameter coordinated cooling achieves a balance between on-demand cooling and efficient response;

[0114] The condenser and energy storage tank are switched on and off as needed by the drive components, which can simultaneously respond to two parameters: drill bit temperature and drill rod speed. Compared with single temperature control or single speed control, this avoids the ineffective waste of cold source caused by continuous cooling and solves the problems of lag and poor cooling effect of single parameter control. It realizes the coordinated action of rapid heat transfer, on-demand switching, and deep cryogenic energy storage, and the cooling control logic is more in line with the actual working conditions of high-temperature drilling. In addition, the dual scheme of pure mechanical and electric control improves the adaptability to different fire zone working conditions and the flexibility of field application.

[0115] 3-3, integrated cooling, slag removal, and drag reduction to improve overall drilling efficiency;

[0116] Using liquid nitrogen cryogenic working fluid in the energy storage tank as a cold source, the high-pressure nitrogen gas after heat absorption and vaporization can work in conjunction with a high-pressure gas source to simultaneously achieve drilling slag removal and borehole wall gas film drag reduction. On the one hand, the drilling slag is quickly discharged through high-pressure airflow to avoid drill jamming accidents; on the other hand, a protective gas film is formed between the drill rod and the borehole wall to reduce the heat generated by the rotational friction of the drill rod, further enhancing the cooling effect and forming a positive synergistic cycle of "active cooling - efficient slag removal - friction drag reduction", which significantly improves the drilling efficiency in high-temperature fire zones. Attached Figure Description

[0117] Figure 1 This is a flowchart of the blocking method in this invention;

[0118] Figure 2 This is a front view of the drill rod and drill bit assembly of the drilling unit in the plugging system of the present invention;

[0119] Figure 3 This is an exploded view of the assembly between the central tube, condenser box, and energy storage box in the drilling unit of this invention;

[0120] Figure 4 This is a first-view exploded view of the assembly of the condenser box and the central tube in the drilling unit of this invention;

[0121] Figure 5 This is a second-view exploded view of the assembly of the condenser box and the central tube in the drilling unit of this invention;

[0122] Figure 6 This is a schematic diagram of a cross-section of the condenser box in the drilling unit of this invention;

[0123] Figure 7 This is a front view of the drive component in the drilling unit of the present invention;

[0124] Figure 8 This is a front view of the drilling unit of the present invention when the end cap opens the central tube to remove slag;

[0125] Figure 9 This is a front view of the drilling unit of the present invention when the end cap closes the central tube to form a gas film;

[0126] In the diagram: 10. Drill rod; 11. Secondary vent; 12. Main vent; 13. Annular cavity.

[0127] 20. Drill bit; 21. End cap; 22. Heat-conducting plate;

[0128] 31. Heat dissipation chamber; 32. Condensation chamber; 321. First baffle; 322. Second baffle; 33. Evaporation tube; 34. Return pipe;

[0129] 40. Energy storage tank; 41. Pressure relief valve;

[0130] 50. Center tube; 51. Slide rail;

[0131] 60. Drive component; 61. Shape memory alloy component; 62. Support cylinder; 63. Elastic component; 64. Support rod. Detailed Implementation

[0132] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0133] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its 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; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0134] like Figure 1 As shown, a method for identifying and sealing coal fire cracks using injection and detection separation specifically includes the following steps:

[0135] S1, a drilling network including injection holes and observation holes is formed in the coal fire area through the heat dissipation drill rod with the above-mentioned cooling components;

[0136] Among them, the borehole located in the center of the expected crack development area is selected as the injection hole, and at least two adjacent boreholes around it are selected as observation holes;

[0137] S2, Before injecting the tracer medium, select at least one observation well and use well-to-surface combined electromagnetic scanning and / or cross-well combined electromagnetic scanning to acquire background field multi-physical quantity data vectors, including potential and magnetic field data, before injection. ;

[0138] Subsequently, tracer media with significant differences in electrical conductivity and magnetic permeability are continuously injected into one or more injection wells. The tracer media moves along the crack network under pressure. During or after the tracer media injection, a combined electromagnetic scan is performed again to acquire the multiphysics data vector of the excitation field. ;

[0139] The tracer medium, acting as a tracer, is a sensitive fluid that undergoes delayed or non-permanent curing. This fluid consists of 70%-90%wt of a base carrier fluid, 5%-30%wt of a composite tracer functional component, and 0.1%-5%wt of a rheology modifier. The composite tracer functional component is a mixture of conductive and magnetic components. The conductive component can be one or more of hydroxylated reduced graphene oxide, multi-walled carbon nanotubes, carboxylated short-diameter multi-walled carbon nanotubes, and nano-silver powder. The magnetic component can be one or more of nano-ferric oxide powder, carbonyl iron powder, ultrafine magnetite powder, and ferrite micropowder. The fluid's electrical conductivity differs from the background value of the surrounding rock in the target area by at least one order of magnitude, and its magnetic permeability differs from the background value of the surrounding rock in the target area by at least five times. Furthermore, it exhibits low viscosity characteristics with shear thinning during the initial injection phase, facilitating long-distance seepage and filling within the fracture network.

[0140] The excitation field multiphysics data vector Multi-physical quantity data vectors of background field Perform the difference operation to obtain the time-shifted differential observation data vector. ,Right now ;

[0141] S3-1 is the macroscopic field signal that can be measured on the surface / in the well. Convert to a realistic three-dimensional distribution of coal and rock fractures, and define a two-parameter model of the underground medium. The model To characterize the electrical conductivity within each grid cell in the underground three-dimensional space With permeability Combined column vectors; construct an inversion objective function containing data fitting terms and model regularization terms. :

[0142]

[0143] in, For the parameters of each grid cell in the final underground three-dimensional space (including) and The distribution of tracer changes, with non-zero regions representing cracks filled with tracer;

[0144] The data weighting matrix is ​​typically a diagonal matrix formed by the reciprocal of the standard deviation of the data noise, used to standardize the signal-to-noise ratio differences between different observation data. Specifically, in step S2, each measuring point undergoes N repeated observations (e.g., N=64), recording the original potential response sequence or magnetic field strength response sequence. The standard deviation of the aforementioned continuous observation data sequence for that measuring point is then calculated. ,make The diagonal elements This can automatically reduce the interference of high-noise data on the inversion results and enhance noise resistance;

[0145] The joint sensitivity Jacobian matrix is ​​formed by combining the potential partial derivative submatrix of the high-density electrical method (corresponding to the change in conductivity) and the magnetic field partial derivative submatrix of the well magnetic measurement (corresponding to the change in magnetic permeability). Its essence is the Fréchet derivative obtained by the forward modeling physical equations for the two-parameter model of the subsurface medium.

[0146] is the regularization factor, a scalar constant used to adjust the weight balance between the degree of data fit and the smoothness of the model; The selection of the curve employs an L-curve adaptive search algorithm; during the inversion iteration process, different curves are dynamically calculated. The data fit difference corresponding to the value With model roughness ,draw Curve. Select the point of maximum curvature (inflection point) of the curve. The value is used as the optimal regularization parameter to achieve the best balance between resolution and stability;

[0147] The model roughness matrix (or model weighting matrix) is constructed using a three-dimensional second-order finite difference operator (Laplacian operator), that is, for any element in the three-dimensional mesh... The operator calculates the parameter differences between itself and its six adjacent units (front, back, left, right, top, and bottom). This is achieved by minimizing... This forces the inversion results to maintain spatial continuity, which is consistent with the geological characteristics of continuous extension of the fractures;

[0148] The L2 norm of a vector is the square of its Euclidean norm, which is the sum of the squares of the elements of the vector. It is used to quantify the magnitude of the residual.

[0149] S3-2, obtaining countless [items] in step S3-1 To find the optimal solution that uniquely matches the geological characteristics of the coal fire fractures at the site, it is necessary to make... Minimum, i.e., taking the unknown quantity The derivative (gradient) equals the zero vector, yielding the fundamental normal equations:

[0150]

[0151] in, They are respectively , The transpose of the matrix;

[0152] Joint sensitivity Jacobian matrix Applicable to changes in physical properties caused by tracer media When the error of linear approximation is very small and negligible, it can be solved using the fundamental system of equations. However, in this example, a tracer medium with significant differences in electrical conductivity and magnetic permeability was injected. The electrical conductivity / magnetic permeability at the crack location jumped by a factor of 10-100. For extremely large changes, the fundamental equations are used directly for solving. The error was amplified, and the obtained This would result in complete distortion and would fail to obtain the true three-dimensional spatial distribution of the cracks. Therefore, the Gauss-Newton iterative method is used to solve the nonlinear inversion problem in step S3-1 (solving... The process involves reconstructing the three-dimensional electrical and magnetic conductivity distributions of underground fissures, specifically including the following iterative steps:

[0153] S3-2-1, Iteration Initialization: Set the iteration count... ; Initial background model As the initial model for the inversion, let = And set the residual convergence threshold and the maximum number of iterations;

[0154] S3-2-2, Dynamic Update of Forward Response and Joint Sensitivity Jacobian Matrix: Based on the current... The model of the next iteration Numerical simulations were performed using multiphysics forward modeling operators to calculate the theoretical response of the current model. At the same time, the current joint sensitivity Jacobian matrix is ​​recalculated. ;

[0155] S3-2-3, Construct a modified regularized normal equation system;

[0156] To achieve high-precision crack characterization and quantitative parameter inversion under high-contrast conditions after the tracer medium is injected, a model correction factor is introduced. To construct a system of normal equations containing double difference residuals:

[0157]

[0158] in, For the first Model corrections in the next iteration (including conductivity corrections) With permeability correction );

[0159] For the first The current joint sensitivity Jacobian matrix of the next iteration The transpose of the matrix, Weighted matrix of data The transpose of the matrix;

[0160] In the right side of the equation The residual vector of pure difference data represents the fitting error between the actual observed electromagnetic field increment and the electromagnetic field increment predicted by the theoretical model.

[0161] S3-2-4, Solve for the model correction:

[0162] Since the Jacobian matrix of the 3D inversion is extremely large, the above equation is solved iteratively using the conjugate gradient least squares (CGLS) method to obtain the model correction for the current iteration step. ;

[0163] S3-2-5, Model parameter update:

[0164] The obtained model corrections are then added to the current model to update the subsurface medium parameters:

[0165]

[0166] in, For the next underground medium parameters, These are the current underground medium parameters; The iterative search step size is dynamically determined using a line search algorithm to ensure the objective function... It shows a monotonically decreasing trend;

[0167] S3-2-6, Convergence Condition Determination and Result Output:

[0168] Calculate the root mean square error of the data residuals in the current iteration and the norm of the model correction. If it is less than the set convergence threshold, or the number of iterations... Once the maximum number of iterations is reached, the stopping condition is triggered, the iteration loop ends, and the final two-parameter model of the underground medium is output. If the stopping condition is not met, then let Return to step S3-2-2 and enter the next loop;

[0169] S3-2-7, Extracting abnormal crack distribution:

[0170] Based on the final output model Calculate the final distribution of model parameter changes. The The non-zero region in space directly characterizes the three-dimensional spatial distribution morphology of the crack filled with the tracer medium;

[0171] S4, based on the three-dimensional spatial distribution of cracks, quantitative sealing and effect closed-loop verification are performed, including the following steps:

[0172] S4-1, Grouting and Sealing: Based on the three-dimensional spatial distribution of the cracks obtained in step S3, key crack channels are identified as grouting and sealing targets; existing injection holes, observation holes, or new boreholes can be used, and pre-filled tracer sealing materials with conductive and magnetic components are injected into the sealing targets; by planning the grouting sequence for multiple boreholes, an effective three-dimensional sealing curtain is formed; after the tracer sealing material is cured, it can maintain electromagnetic properties that are significantly different from the surrounding rock.

[0173] S4-2, Re-scanning and Inversion: After the tracer sealing material has solidified, repeat step S2 to obtain multi-physical quantity data vectors including potential data and magnetic field data after sealing, and perform inversion imaging;

[0174] S4-3, Verification of Blocking Effectiveness:

[0175] The latest inversion imaging results are intelligently compared and judged with the actual grouting project parameters:

[0176] Validity is determined as follows: If a dual-physics anomaly matching the electromagnetic response characteristics of the tracer sealing material is detected in the three-dimensional region of the original crack target, and the inversion volume is obtained through the voxel integral formula, then the inversion is valid. Its numerical value represents the effective volume of material filling the crack and the actual grouting volume recorded by the grouting pump. If the error between them is within the set allowable threshold range, then the sealing is verified to be effective, forming a reliable fire-barrier and oxygen-barrier curtain;

[0177] Invalidity and Anomaly Handling: If any of the following situations occur: A. No obvious electromagnetic anomaly is detected in the target area; B. The electromagnetic anomaly area deviates significantly from the set blocking target point; C. The inversion volume... If the ratio of the actual grouting volume to the total grouting volume is less than 0.7, it is determined that there has been serious grout leakage or loss, and the sealing is ineffective.

[0178] Subsequent closed-loop measures: When the sealing is determined to be ineffective, the control unit immediately outputs a leakage alarm and automatically issues a grouting pause command to avoid material waste; at the same time, based on the latest acquired abnormal grout distribution data, the grout loss path is tracked and a correction plan is automatically generated, namely: adjusting the quick-setting ratio of the next batch of tracer sealing material to seal the large leakage channel, or replanning the supplementary grouting holes for interception and re-grouting, until the effectiveness is verified by scanning again, realizing intelligent closed-loop control of the entire process from "detection-grouting-verification-correction";

[0179] Furthermore, in step S2, a combined well-to-surface electromagnetic scanning and / or a cross-hole combined electromagnetic scanning are employed. The well-to-surface combined electromagnetic scanning component is adapted for three-dimensional detection of shallow, large-scale fracture development areas in coal-fired zones, primarily using a combined well-to-surface high-density electrical resistivity tomography (EDT) and secondarily using a combined well-to-surface magnetic tomography, achieving coordinated data acquisition across two physical fields. Meanwhile, the cross-hole combined electromagnetic scanning component is adapted for high-precision tomographic imaging detection of deep, fracture-concentrated areas in coal-fired zones, primarily using a cross-hole high-density EDT and secondarily using cross-hole magnetic tomography, achieving fine characterization of inter-hole fractures. When well-to-surface combined electromagnetic scanning and cross-hole combined electromagnetic scanning are used in combination, multi-mode combined detection of well-to-surface and cross-hole methods can be achieved, further improving the coverage and accuracy of three-dimensional imaging of coal-fired fractures.

[0180] In step S3-2-1, The construction process is as follows: The background field multi-physical quantity data vector... As input, combining prior information such as existing geological borehole columnar sections and electrical / magnetic logging curves in the area, a three-dimensional initial physical property distribution grid of the subsurface space is established using a conventional smoothing inversion algorithm. Each grid is assigned initial electrical conductivity and magnetic permeability values, thus forming the initial background model. ;

[0181] In step S3-2-2, the theoretical response of the current model Current joint sensitivity Jacobian matrix The construction process is as follows: establish the governing equations of the DC steady electric field and the static magnetic field in the three-dimensional medium respectively, and use them as physical forward modeling operators;

[0182] For high-density electrical resistivity tomography (EDT), the Poisson equation describing the steady-state electric field distribution is established:

[0183]

[0184] in, For divergence operators, For gradient operators, For electrical conductivity, Potential, conductivity With potential All change with the three-dimensional spatial coordinates; The current density supplied to the point power source. For current intensity, For the Dirac function, The position vector of the point power source (power supply electrode); Let be the position vector of any point in three-dimensional space;

[0185] For in-well magnetic measurements, an integral equation for the static magnetic field describing the magnetization anomaly field is established:

[0186]

[0187] in, This is the spatial magnetic anomaly vector. Permeability of free space; The magnetization intensity;

[0188] The position vector of the observation point (magnetometer probe). With the underground field source point location vector The difference, that is Its module length is ; Unit vector, ; The integral volume of the three-dimensional space containing the underground anomaly;

[0189] The two sets of physical equations above clearly define the conductivity induced by the tracer medium. With permeability Anomalies are changes in the potential of underground spaces. With magnetic field The independent physical dominant factors of distribution;

[0190] Define the multiphysics forward modeling operator The numerical mapping process for solving the above physical governing equations involves incorporating conductivity. With permeability model Substituting the Poisson equation and the static magnetic field integral equation for the stable electric field distribution described above, the theoretical potential at the observation point can be calculated. With magnetic field The response sequence vector; define the joint sensitivity Jacobian matrix. This is the matrix of partial derivatives of the forward response with respect to the model parameters, which is derived from the potential partial derivative submatrix of the current high-density electrical resistivity method. The partial derivative submatrix of the magnetic field with respect to the current well magnetic measurement The model is constructed by splicing together components; the theoretical response of the current model can be obtained by discretizing and solving the two sets of governing equations using the finite element method or finite volume method. The partial derivative matrix is ​​extracted to update the current joint sensitivity Jacobian matrix. ;

[0191] This example employs a collaborative detection method that primarily uses high-density electrical resistivity tomography (EDT) combined with in-well magnetic surveying. By combining the Poisson equation for current diffusion with the static magnetic field equation using a tracer medium with both electrical and magnetic properties, a joint sensitivity Jacobian matrix is ​​constructed, consisting of a potential partial derivative matrix and a magnetic field partial derivative matrix from in-well magnetic surveying. This overcomes the limitations of single-hole magnetic surveying. The EDT array (providing a wide-area three-dimensional framework constraint) and magnetic surveying (providing high-precision details around the borehole) mutually verify each other, eliminating the non-uniqueness problem of single-physics field inversion. This enables true three-dimensional, high-resolution stereo imaging of hidden fracture networks in extremely complex deep formations.

[0192] Furthermore, in step S4, the injection volume of the tracer sealing material... The calculation formula is:

[0193]

[0194]

[0195]

[0196] in, The spatial inversion volume of the fracture for effective filling of the tracer medium can be obtained by the three-dimensional spatial distribution of the fracture to obtain the spatial inversion volume of the fracture for the flow of grout.

[0197] The total number of 3D meshes for imaging. Index number of the grid cell ( =1, 2, ..., N);

[0198] For the first The geometric volume of a single element in a grid;

[0199] For the first The equivalent crack porosity of each grid is calculated based on the Archie formula, i.e., the porosity corresponding to each grid, which can be obtained after the inversion in step S3.

[0200] For the first The change in inverted conductivity of each grid cell , The final model for step S3-2-7 above The Middle The conductivity value of each grid. The initial background model for step S3-2-1 above The Middle The conductivity value of each grid;

[0201] This is the slurry diffusion loss coefficient, which is generally taken as 1.1-1.3. It is used to compensate for the volume loss caused by slurry filtration into micropores and solidification shrinkage. The conductivity of the tracer medium; The cementation index, typically ranging from 1.3 to 2.0, characterizes the effect of the tortuosity of the pore channels on electrical conductivity.

[0202] Based on the calculated grouting volume It automatically generates the cut-off pressure threshold and maximum injection volume command for the grouting pump.

[0203] A coal fire crack identification and sealing system based on injection and detection separation, applicable to the aforementioned sealing method, comprising:

[0204] A drilling unit is a network of boreholes, including injection holes and observation holes, used for drilling operations in coal-fired areas.

[0205] The crack identification unit includes an injection component for injecting a tracer medium into the injection hole, an electromagnetic detection component for performing electromagnetic scanning into the observation hole to obtain potential and magnetic field data, and an analysis component for building a model to obtain the three-dimensional spatial distribution of the crack and verifying the effectiveness of the sealing.

[0206] The plugging unit has plugging components for injecting tracer plugging material into the borehole;

[0207] The control unit, connected to the drilling unit, fracture identification unit, and sealing unit, is used to control the actions of each unit. Specifically, it first controls the drilling unit to drill in the coal fire area to form a borehole network, and then controls the electromagnetic detection component to acquire the background electromagnetic response data vector before injection. Then, the injection unit is controlled to continuously inject the tracer medium into one or more injection holes. During or after injection, the electromagnetic detection unit is controlled to acquire the electromagnetic response data vector of the excitation field. After the analysis component constructs a model to obtain the three-dimensional spatial distribution of the crack, the control unit then controls the sealing unit to inject tracer sealing material into the borehole.

[0208] Specifically, the injection component in the crack identification unit has a grouting pipe. One end of the grouting pipe extends into the injection hole, and the other end is connected to the tracer medium source through a pressure pump. The hole is sealed at the opening of the injection hole, for example, by using a sealing airbag fitted on the grouting pipe. This is existing technology and will not be elaborated further.

[0209] The electromagnetic detection component is the core data acquisition module of the fracture identification unit. It is used to perform the full-process electromagnetic scanning of the background field and excitation field in step S2, and the post-plugging effect verification scan in step S4, to obtain the raw potential and magnetic field data required for inversion imaging. The electromagnetic detection component includes a well-to-surface combined electromagnetic scanning component and / or a cross-hole combined electromagnetic scanning component, as well as a synchronous acquisition control unit and a data preprocessing and transmission unit.

[0210] The operating mode can be flexibly switched according to the depth of crack development in the coal fire area and the required detection range:

[0211] A. A combined well-to-surface electro-magnetic scanning component, adapted for three-dimensional detection of shallow and large-scale fractured areas in coal-fired zones. It primarily utilizes a combined well-to-surface high-density electrical resistivity tomography (EDS) method, supplemented by a combined well-to-surface magnetic survey, to achieve collaborative data acquisition across two physical fields. The combined well-to-surface EDS component includes:

[0212] The well-surface combined high-density electrical resistivity subsystem (main detection module) features: a high-density non-polarized surface electrode array, a multi-channel high-temperature resistant downhole electrode string, a high-power programmable electrical resistivity transmitter, and a multi-channel synchronous electrical resistivity receiver.

[0213] The well-ground combined downhole magnetic measurement subsystem (auxiliary detection module) includes: a high-temperature resistant triaxial downhole magnetometer probe, a surface magnetic measurement recording unit, and a surface reference magnetometer;

[0214] Among them, the high-density non-polarized electrode array on the surface can have surface power supply electrodes and surface measurement electrodes; the high-power programmable electrical method transmitter is connected to the power supply terminals of the surface power supply electrodes and the multi-channel high-temperature resistant downhole electrode string respectively, and is used to provide excitation power for the establishment of a stable underground electric field; the multi-channel synchronous electrical method receiver is connected to the measurement terminals of the surface measurement electrodes and the multi-channel high-temperature resistant downhole electrode string respectively, and is used to synchronously acquire the potential difference signals of each measuring point;

[0215] The high-temperature resistant triaxial downhole magnetometer probe is electrically connected to the input end of the surface magnetic measurement and recording unit for real-time transmission of the three-component magnetic field data collected downhole; the signal output end of the surface reference magnetometer is electrically connected to the calibration input end of the surface magnetic measurement and recording unit for providing a diurnal variation correction reference for the magnetic measurement data.

[0216] At this time, the power supply terminal of the synchronous acquisition control unit is electrically connected to the field regulated power supply, and its output terminal is electrically connected to the control terminal of the high-power programmable electrical method transmitter, the multi-channel synchronous electrical method receiver, and the ground magnetic measurement recording unit, respectively, to provide synchronous triggering and parameter control signals for each device.

[0217] The multi-channel high-temperature resistant downhole electrode string and the high-temperature resistant triaxial downhole magnetometer probe are lowered and raised into the observation hole through the winding component. The winding component can communicate with the synchronous acquisition and control unit to record the lowering depth of the downhole equipment in real time, so as to achieve accurate matching between the acquired data and the spatial coordinates. In addition, a centering device can be set at the opening of the observation hole to ensure centering and avoid measurement errors caused by adhering to the wall.

[0218] The well-to-surface combined electromagnetic scanning component can realize two well-to-surface joint observation modes: surface power supply-well reception and well power supply-surface reception. Through the cooperation of the surface high-density non-polarized electrode array and the downhole equipment, it can achieve full coverage detection of the fracture area in a 360° range around the observation hole and a depth of 0-800m. The same set of equipment and the same set of locked observation parameters are used before and after injection to ensure the purity of time-shift differential data and provide core input data for dual-parameter joint inversion.

[0219] B. Cross-hole combined electro-magnetic scanning component, adapted for high-precision tomographic imaging detection in deep coal fire zones and areas with concentrated fracture development. It primarily uses cross-hole high-density electrical resistivity tomography (EDT) supplemented by cross-hole magnetic tomography (MTT) to achieve fine characterization of inter-hole fractures. The cross-hole combined EDT component includes:

[0220] The cross-hole high-density electrical resistivity subsystem (main detection module) has at least two sets of multi-channel high-temperature downhole transmitter-receiver electrode strings, a high-power multi-channel programmable electrical resistivity transmitter, a multi-channel synchronous electrical resistivity receiver, and a cross-hole observation programmable module;

[0221] The cross-hole magnetic tomography subsystem (auxiliary detection module) has at least two sets of high-temperature resistant triaxial downhole magnetometer probes, a dual-well synchronous surface magnetic measurement and recording unit, and a surface reference magnetometer.

[0222] Among them, the high-power multi-channel programmable electrical resistivity transmitter is connected to the power supply terminal of the multi-channel high-temperature resistant downhole electrode string to provide excitation power for the establishment of a stable underground electric field; the multi-channel synchronous electrical resistivity receiver is connected to the transmitting-receiving electrode string in all receiving holes to synchronously acquire the potential difference signal between the transmitting-receiving electrode pairs across holes.

[0223] The high-temperature resistant triaxial downhole magnetometer probe is electrically connected to the multi-channel input terminal of the dual-well synchronous surface magnetic measurement and recording unit to realize the synchronous acquisition of magnetic measurement data from two or more wells; the surface reference magnetometer is electrically connected to the calibration input terminal of the dual-well synchronous surface magnetic measurement and recording unit to provide a unified daily variation correction benchmark.

[0224] At this time, the synchronous acquisition control unit is connected to the high-power multi-channel programmable electrical resistivity transmitter, the multi-channel synchronous electrical resistivity receiver, and the dual-well synchronous ground magnetic measurement recording unit to realize synchronous control of acquisition triggering and lifting, and ensure that the depth synchronization error of the dual-well probe is ≤5cm.

[0225] Multi-channel high-temperature resistant downhole transmitting-receiving electrode strings, downhole magnetometer probes, and dual-well synchronous surface magnetic measurement and recording units can be lowered and raised into the observation hole via a winding component. The winding component can communicate with the synchronous acquisition and control unit to record the lowering depth of the downhole equipment in real time, achieving precise matching between the acquired data and spatial coordinates. In addition, a centering device can be installed at the opening of the observation hole to ensure centering and avoid measurement errors caused by adhering to the wall.

[0226] The well-to-surface combined electromagnetic scanning component can realize cross-hole tomographic imaging detection between injection wells and surrounding observation wells. For deep fractures where the resolution of the far-well area is insufficient in the well-to-surface combined mode, it can achieve high-precision and detailed characterization of the inter-well area. It can be used in conjunction with the well-to-surface combined electromagnetic scanning component to realize multi-mode joint detection of well-to-surface / cross-hole, further improving the coverage and accuracy of three-dimensional imaging of coal and fire fractures.

[0227] The sealing unit has a grouting pipe and sealing components. One end of the grouting pipe extends into the borehole formed at the grouting sealing location, and the other end is connected to the tracer sealing material source via a pressure pump. The sealing is performed at the borehole by the sealing components. This is existing technology and will not be further elaborated. The tracer sealing material includes one or more of the following: geopolymer sealing material, solid waste-doped expanded graphite sealing material, or organic curing foam material. The tracer sealing material contains a certain proportion of conductive or magnetic tracer components to maintain electromagnetic properties that are significantly different from those of the surrounding rock after the material has cured, so as to facilitate the verification of the sealing effect in step S4 above.

[0228] The control unit is the assembly of the overall control system, which includes the controller matched to each unit. The overall control system issues control commands to the controllers of the corresponding units to complete the sequential actions of this blocking system.

[0229] This coal fire crack identification and sealing system, which separates injection and exploration, drills into the coalfield fire area using a heat dissipation drill rod in the drilling unit, forming a borehole network that includes injection holes and observation holes. The borehole grid can be set from 10m×10m to 20m×20m. The borehole located in the center of the expected crack development area is selected as the injection hole, and at least two adjacent boreholes around it are selected as observation holes.

[0230] The electromagnetic detection component is lowered into at least two observation holes to perform an initial electromagnetic scan, acquiring the background electromagnetic response data vector before injection. ;

[0231] The tracer medium is then continuously injected into one or more injection holes via the injection component. The electrical conductivity of the tracer medium fluid differs from the background value of the surrounding rock in the target area by at least one order of magnitude. The injection holes are sealed to prevent tracer medium overflow. Under pressure, the tracer medium moves along the fracture network. During or after the injection of the tracer medium, the electromagnetic detection component performs another electromagnetic scan to acquire the electromagnetic response data vector of the excitation field. ;

[0232] The electromagnetic detection component transmits the acquired data to the analysis component via a wireless communication module. The analysis component is a computer with modeling, calculation and analysis functions to complete the construction of the model and equation system in step S3. Based on the data acquired by the electromagnetic detection component and other basic data, the three-dimensional spatial distribution of the crack can be analyzed and obtained. The grouting volume can be further calculated, and the multi-physical quantity data vector obtained after the second scan and inversion can be inverted and imaged to finally verify the sealing effectiveness.

[0233] Based on the three-dimensional spatial distribution of the crack, the operator determines the grouting location and volume. The tracer sealing material is injected into the borehole through the sealing unit, and the borehole opening is sealed to prevent the tracer medium from overflowing. After the sealing has cured, the electromagnetic detection component performs another electromagnetic scan. If an electromagnetic anomaly with the same physical properties as the sealing material is detected in the original crack area, and the inverted volume matches the grouting volume well, the sealing is verified to be effective.

[0234] After verifying the effectiveness of the sealing, an ecological substrate was laid on the surface of the coalfield after the fire was extinguished deep within the fire zone to help with vegetation restoration.

[0235] In some examples of the present invention, the coal fire crack identification and sealing system with injection and exploration separation also includes a shallow treatment unit;

[0236] This unit is used for the construction of oxygen-barrier solid waste-based pre-mineralized composite materials for surface construction after deep fire extinguishing in coalfield fire areas, in order to help vegetation restoration;

[0237] Once the sealing is verified to be effective, an ecological substrate for efficient vegetation restoration is laid on the surface of the coalfield after deep fire extinguishing. The ecological substrate is a pre-mineralized composite material based on solid waste, mixed in the following mass proportions: 15-25 parts of straw-based hydrogel microspheres, obtained by cross-linking after carboxymethylation modification of crop straw; 30-40 parts of red mud-biochar composite particles, obtained by mixing red mud and rice husk biochar at a mass ratio of 1:1 and sintering at 800℃ for 2 hours to form porous particles; 20-30 parts of decomposed coal gangue powder, obtained by grinding coal gangue after 6 months of aerobic composting; and 2-5 parts of arbuscular mycorrhizal fungi encapsulation slow-release agent, prepared by emulsification-cross-linking method using AMF spores, sodium alginate, and humic acid. The ecological substrate is mixed with water and spread on the surface of the fire area with a thickness of ≥20cm.

[0238] In this example, solid waste-based premineralized composite materials are used to cover coalfield fire areas as an independent construction step. This not only effectively isolates oxygen and prevents reignition, but its specific pH value and components (such as straw-based hydrogels and arbuscular mycorrhizal fungi) can also rapidly improve the soil environment, creating favorable conditions for vegetation establishment and community restoration. This extends the endpoint of disaster management to the active restoration of the ecosystem, achieving a balance between engineering and environmental benefits, and avoiding the neglect of ecological restoration after coalfield fire suppression.

[0239] like Figures 2 to 5 As shown, the drilling unit has a heat-dissipating drill rod; the heat-dissipating drill rod includes:

[0240] The drill rod 10 and the drill bit 20 are provided. The drill bit 20 is provided with a closed heat dissipation cavity 31 and the heat dissipation cavity 31 is filled with phase change material.

[0241] The cooling component has an energy storage box 40 located inside the drill pipe 10 and at least one condenser box 32 located inside the energy storage box 40.

[0242] The energy storage tank 40 is fixedly arranged and stores liquid cryogenic working fluid inside. The condenser 32 is connected to the drive component 60 and is driven to move radially. Under the action of the drive component 60, when the temperature inside the drill rod 10 exceeds the first temperature threshold, the condenser 32 moves radially to a position in contact with the energy storage tank 40. When the temperature inside the drill rod 10 drops below the second temperature threshold, the condenser 32 moves radially to a position where it is detached from the energy storage tank 40. Alternatively, when the rotational speed of the drill rod 10 exceeds the first rotational speed threshold, the condenser 32 moves radially to a position in contact with the energy storage tank 40. When the rotational speed of the drill rod 10 drops below the second rotational speed threshold, the condenser 32 moves radially to a position where it is detached from the energy storage tank 40. Wherein, the first temperature threshold is greater than the second temperature threshold, and the first rotational speed threshold is greater than the second rotational speed threshold.

[0243] The condenser 32 and the heat dissipation chamber 31 are connected by the evaporation pipe 33 and the return pipe 34 respectively, so that the phase change material can evaporate from the heat dissipation chamber 31 into the condenser 32 and then flow back from the condenser 32 into the heat dissipation chamber 31 to form a closed loop.

[0244] Specifically, the drill rod 10 and the drill bit 20 are detachably connected, for example, by using a toothed or pin-type connection. The contents of the energy storage box 40 and the heat dissipation cavity 31 need to be determined before installation and use.

[0245] The phase change material inside the drill bit 20 is one or a combination of sodium-potassium alloy, water, or naphthalene, and its filling amount is calculated to ensure that the phase change material can be evaporated, condensed, and refluxed under the centrifugal force of the rotating drill bit 20.

[0246] The cooling component's energy storage tank 40 pre-stores liquid cryogenic working fluid to provide an independent cold source for drilling. Preferably, the cryogenic working fluid is liquid nitrogen. The energy storage tank 40 has a circular sealed structure and is fixed inside the drill pipe 10. The condenser 32 can be four arc-shaped structures, evenly arranged circumferentially on the inner side of the energy storage tank 40, and can initially be assembled into a ring. The condenser 32 can be installed radially via a slide rail 51. The condenser 32 and the heat dissipation cavity 31 are connected by an evaporation pipe 33 and a return pipe 34. The heat dissipation cavity 31 can be machined with micro-channels and grooves on the inner side of the heated surface to improve heat exchange. The evaporator tube 33 has multiple microchannels inside, and the capillary force generated during evaporation can provide the power for the circulation of the evaporating working fluid, provide the liquid evaporation interface, and realize liquid supply. The return pipe 34 is connected to the bottom of the heat dissipation cavity 31 and the condenser 32 to ensure liquid flow and avoid blockage by steam. A telescopic flexible connection is made at a certain point between the evaporator tube 33 and the return pipe 34. This flexible connection is used to compensate for the radial movement of the condenser 32. The drive component 60 is used to automatically connect or disconnect the connection between the condenser 32 and the energy storage box 40 according to changes in temperature and speed.

[0247] When constructing in high-temperature fire zones, the entire drill rod is axially perpendicular or at a certain angle to reduce the impact on the evaporation, rise, condensation, and reflux of the phase change material in the cooling components.

[0248] During drilling operations, the drilling network mainly includes injection holes and observation holes. The drill bit 20 generates frictional heat. When the temperature or rotation speed reaches a certain level, the drive component 60 drives the condenser box 32 to move radially and approach the energy storage box 40. The phase change material filled in the heat dissipation cavity 31 of the drill bit 20 evaporates and enters the condenser box 32 above from the evaporation pipe 33. The phase change material in the condenser box 32 absorbs heat through the wall of the energy storage box 40, cools down and condenses, and then flows back to the heat dissipation cavity 31 from the return pipe 34. This achieves heat dissipation and cooling of the drill bit 20, avoiding excessive temperature that could cause rapid deterioration of the drill bit cutting tooth material, affecting drilling or igniting the coal around the borehole and causing secondary disasters.

[0249] As an example of the drive component 60, the drill bit 20 is provided with a heat source capture module, which can be a temperature sensor for sensing temperature. The drill rod 10 end side can be provided with an angular velocity sensor for sensing the rotation speed of the drill rod 10. The drive component 60 can be a drive rod and fixed inside the drill rod 10.

[0250] The power and signal transmission of the temperature sensor, angular velocity sensor, and drive rod can be continuously led out through an electric slip ring and then connected to the controller. The controller controls the movement of the drive rod. Specifically, when the temperature sensor detects that the temperature inside the drill rod 10 exceeds the first temperature threshold, the controller controls the output end of the drive rod to extend, causing the condenser 32 to move radially and contact the energy storage tank 40. When the temperature inside the drill rod 10 drops to the second temperature threshold, the controller controls the output end of the drive rod to shorten, causing the condenser 32 to move radially and disengage from the energy storage tank 40. When the angular velocity sensor detects that the rotational speed of the drill rod 10 exceeds the first rotational speed... When the speed reaches the threshold, the controller controls the output end of the drive rod to extend, causing the condenser 32 to move radially and contact the energy storage box 40. When the speed of the drill rod 10 drops to the second speed threshold, the controller controls the output end of the drive rod to shorten, causing the condenser 32 to move radially and disengage from the energy storage box 40. It can be noted that the first speed threshold and the second speed threshold can be located in the range of 120-300 r / min, and the first temperature threshold and the second temperature threshold can be located in the range of 120℃-230℃. The corresponding speed threshold and temperature threshold are determined according to the actual construction environment, the characteristics of the elastic element 63 and the shape memory alloy element 61.

[0251] In this example, temperature and rotation speed parameters are obtained through the controller, and then the drive rod is controlled to extend and retract. The operation is convenient and can achieve precise control, which is suitable for the needs of fine drilling. In addition, a monitoring module can be set up to detect the liquid level of the cryogenic working fluid in the energy storage tank 40 or the temperature of key nodes of the drill bit 20.

[0252] As another example of the drive component 60, such as Figure 7 As shown, the drive component 60 has a support cylinder 62, a support rod 64, and a shape memory alloy part 61;

[0253] One end of the support rod 64 moves to be located inside the support cylinder 62 and contacts the elastic element 63, while the other end is fixedly connected to the condenser box 32.

[0254] The support cylinder 62 is provided with an elastic element 63 that contacts the inner wall of the support cylinder 62 and the support rod 64. Under the action of the elastic element 63, the support rod 64 bears the elastic force toward the axis of the drill pipe 10. Under the action of centrifugal force, the support rod 64 moves to compress the elastic element 63.

[0255] The shape memory alloy part 61 is close to the axis of the drill rod 10, one end is fixed and the other end is fixedly connected to the support cylinder 62. The drill bit 20 is provided with a heat-conducting plate 22. One end of the heat-conducting plate 22 extends and is connected to the shape memory alloy part 61. When the temperature reaches the threshold, the shape memory alloy part 61 elongates.

[0256] Specifically, the heat source capture module is a heat-conducting plate 22 installed on the cutting teeth or crown of the drill bit 20. One end of the heat-conducting plate 22 extends and connects to the shape memory alloy part 61, causing the shape memory alloy part 61 to deform when heated; the elastic part 63 is a high-temperature resistant spring.

[0257] The shape memory alloy component 61 is a rod-shaped component formed by twisting and winding shape memory alloy material. At a low initial temperature, the shape memory alloy component 61 is in a shortened state, and under the action of the elastic component 63, the support rod 64 and the condensation box 32 move away from the energy storage box 40. During drilling, when the rotational speed exceeds the first rotational speed threshold, under the action of centrifugal force, the support rod 64 and the condensation box 32 can approach and contact the energy storage box 40. When the rotational speed decreases to below the second rotational speed threshold, under the action of the elastic component 63, the support rod 64 and the condensation box 32 move away from the energy storage box 40. The first and second rotational speed thresholds can be within the range of 120-300 r / min, and the first... The rotational speed threshold is greater than the second rotational speed threshold. When the temperature reaches the first temperature threshold, the shape memory alloy part 61 deforms due to heat, causing the support cylinder 62, support rod 64, and condensation box 32 to gradually approach the energy storage box 40. When the temperature drops to the second temperature threshold, the shape memory alloy part 61 returns to its original state, and the support rod 64 and condensation box 32 move away from the energy storage box 40. The first and second temperature thresholds can be within the range of 120℃-230℃, and the first temperature threshold is greater than the second temperature threshold. It should be noted that the corresponding rotational speed threshold and temperature threshold can be determined according to the actual construction environment based on the characteristics of the elastic part 63 and the shape memory alloy part 61.

[0258] In this example, the elastic element 63 acts on the support rod 64, and the shape memory alloy element 61 is connected to the support cylinder 62, so that the condenser box 32 can automatically move closer to or away from the energy storage box 40 under the condition of temperature or speed. This avoids the complexity of the structure caused by adding wires and other electrical control, and is more stable and reliable. The mechanical drive scheme of the shape memory alloy element 61 does not require the laying of downhole power supply and signal lines. It has a simple structure, strong anti-interference ability, and is suitable for the harsh drilling environment of high temperature and high dust in coal fire areas.

[0259] Furthermore, such as Figure 6 As shown, the condenser box 32 is provided with a first baffle 321 and a second baffle 322 arranged at an incline, with the first baffle 321 located above the second baffle 322;

[0260] The side of the first baffle 321 closest to the evaporator tube 33 is higher than the side furthest from the evaporator tube 33, and the side of the second baffle 322 closest to the return tube 34 is lower than the side furthest from the return tube 34.

[0261] Specifically, the first baffle 321 is used to concentrate the vaporized phase change material along its lower wall, and the second baffle 322 is used to concentrate the liquefied phase change material along its upper wall, thereby improving the efficiency of evaporation and condensation of the phase change material.

[0262] In some examples of the present invention, such as Figures 2 to 5 As shown, the cryogenic working fluid is liquid nitrogen;

[0263] The heat dissipation drill rod also includes:

[0264] The central tube 50 is hollow and coaxially located inside the drill pipe 10 and the drill bit 20.

[0265] The drill rod 10 includes an inner drill rod and an outer drill rod, and an annular cavity 13 is formed between the inner drill rod and the outer drill rod;

[0266] The inner drill rod is provided with a secondary vent 11 that communicates with the annular cavity 13. The lower end of the annular cavity 13 is provided with a main vent 12 that communicates with the outside, and the upper end is connected to the first high-pressure air source through a first rotary joint. The main vent 12 is inclined toward the drill bit 20.

[0267] The energy storage box 40 is located inside the inner drill rod, and a pressure relief valve 41 is provided at the upper end and connected to the auxiliary vent 11.

[0268] Furthermore, the central tube 50 is equipped with a cap 21 at one end of the drill bit 20, and at one end of the drill rod 10, it can be switched to the slag discharge box and the second high-pressure gas source via a second rotary joint;

[0269] The end cap 21 is configured to open the port of the central tube 50 when subjected to pressure from below and close the port of the central tube 50 when subjected to pressure from above.

[0270] The controller controls the inlet pressure of the first high-pressure gas source and the second high-pressure gas source;

[0271] Specifically, the central tube 50 can be used for slag discharge and fixed support; a fixing ring is fixed on the central tube 50, and the upper end of the condenser box 32 can be radially moved and installed on the fixing ring via the slide rail 51;

[0272] When the central tube 50 is used for slag discharge, the upper part of the energy storage box 40 is equipped with a self-resetting pressure relief valve 41. When the pressure of liquid nitrogen after absorbing heat and vaporizing exceeds the set value, the pressure relief valve 41 opens, and the released high-pressure nitrogen gas is discharged from the auxiliary vent 11 and the main vent 12. The first high-pressure gas source simultaneously introduces high-pressure gas into the annular cavity 13. Both the high-pressure gas and the high-pressure nitrogen gas are discharged from the main vent 12, and the drilling slag is discharged from the central tube 50 to the outside.

[0273] The end cap 21 opens unidirectionally upwards and can close to the central tube 50. For example, the lower end of the central tube 50 is provided with a limiting block for the outward rotation of the end cap 21. The end cap 21 is rotatably mounted on the lower end of the central tube 50 via a rotating shaft. A torsion spring is sleeved on the rotating shaft to close the end cap 21 to the central tube 50. Initially, the end cap 21 is closed and limited by the limiting block. The upper end of the central tube 50 can be switched between the slag discharge box and the second high-pressure gas source. Figure 8 As shown, when the central pipe 50 is connected to the slag discharge box, the controller controls the first high-pressure gas source to open, and the high-pressure gas can discharge the slag from the central pipe 50 into the slag discharge box; as Figure 9 As shown, when the central tube 50 is connected to the second high-pressure gas source, the controller controls the second high-pressure gas source to open, and the end cap 21 closes the central tube 50 downward under the action of high-pressure gas. The first high-pressure gas source can be opened or closed. Gas at a certain pressure and high-pressure nitrogen are discharged from the main vent 12 and form a protective gas film between the drill rod 10 and the inner wall of the borehole. This gas film can reduce the direct contact between the drill rod 10 and the inner wall during drilling and avoid the generation of frictional heat.

[0274] In this example, the high-pressure nitrogen gas produced by heating and vaporizing liquid nitrogen in the energy storage tank 40 is combined with the introduced high-pressure gas to quickly remove slag from the central tube 50 during the drilling process. When the central tube 50 is closed, the high-pressure nitrogen gas can form a gas film between the drill rod 10 and the borehole, reducing the direct contact between the drill rod 10 and the inner wall.

[0275] The foregoing description, with reference to preferred embodiments, details an exemplary implementation of the coal fire crack identification and sealing method and sealing system proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A method for identifying and sealing coal fire cracks using injection and detection separation, characterized in that, Specifically, the following steps are included: S1 forms a borehole network including injection holes and observation holes for construction in coal fire areas; Select the borehole located in the center of the expected crack development area as the injection hole, and at least two adjacent boreholes around it as observation holes; S2, Select at least one observation well and perform a combined electromagnetic scanning (EMS) scan. This combined EMS scan is a well-to-surface combined EMS scan and / or a cross-well combined EMS scan to acquire a background field multi-physical quantity data vector including potential and magnetic field data prior to injection. ; A tracer medium with significant differences in electrical conductivity and magnetic permeability is then continuously injected into the injection well. Under pressure, the tracer medium moves along the crack network. During or after injection, a combined electromagnetic scan is performed again to acquire the multi-physics data vector of the excitation field. ; S3-1, Defining a Two-Parameter Model for Subsurface Media Construct an inversion objective function that includes a data fitting term and a model regularization term. ; S3-2, the Gauss-Newton iterative method is used to solve the nonlinear inversion problem of step S3-1, and the three-dimensional conductivity and magnetic permeability distribution of the underground fractures are reconstructed to calculate the final model parameter variation distribution. ; The final output model, This is the initial background model; The non-zero region in space directly characterizes the three-dimensional spatial distribution of cracks filled with tracer medium; S4. Based on the three-dimensional spatial distribution of the crack, the amount of tracer sealing material to be injected is determined, and tracer sealing material with pre-placed conductive and magnetic components is injected into the sealing target point to verify the grouting sealing effect.

2. The method for identifying and sealing coal fire cracks using injection and detection separation according to claim 1, characterized in that, In step S3-1, an inversion objective function is constructed that includes a data fitting term and a model regularization term. : in, The parameter variation distribution of each grid cell in the final underground three-dimensional space is represented by non-zero regions, which indicate cracks filled by the tracer medium. A data weighting matrix is ​​used to standardize the signal-to-noise ratio differences among different observation data; The joint sensitivity Jacobian matrix is ​​formed by combining the potential partial derivative matrix of the high-density electrical resistivity method and the magnetic field partial derivative matrix of the well magnetic measurement. This is a regularization factor used to adjust the weight balance between the degree of data fit and the smoothness of the model; This is the roughness matrix of the model; The square of the Euclidean norm of a vector is used to quantify the magnitude of the residual. The time-shifted differential observation data vector is calculated using the following formula: ; Step S3-2 specifically includes the following iterative steps: S3-2-1, Iteration Initialization: Set the iteration count... ; Initial background model As the initial model for inversion, the residual convergence threshold and the maximum number of iterations are set; S3-2-2, Dynamic Update of Forward Response and Joint Sensitivity Jacobian Matrix: Based on the current... The model of the next iteration Numerical simulations were performed using multiphysics forward modeling operators to calculate the theoretical response of the current model. At the same time, the current joint sensitivity Jacobian matrix is ​​recalculated. ; S3-2-3, Construct a modified regularized normal equation system; Introducing model correction amount To construct a system of normal equations containing double difference residuals: in, For the first Model correction amount in each iteration; For the first The current joint sensitivity Jacobian matrix of the next iteration The transpose of the matrix, Weighted matrix of data The transpose of the matrix; The theoretical response of the initial background model; S3-2-4, Solve for the model correction: By iteratively solving the normal equations in step S3-2-3 using the conjugate gradient least squares method, the model correction for the current iteration step can be obtained. ; S3-2-5, Model parameter update: The obtained model correction amount Overlay onto the current model to update the subsurface medium parameters: in, For the next underground medium parameters, These are the current underground medium parameters; The iterative search step size is dynamically determined using a line search algorithm to ensure the inversion of the objective function. It shows a monotonically decreasing trend; S3-2-6, Convergence Condition Determination and Result Output: Calculate the root mean square error of the data residuals in the current iteration and the norm of the model correction. If it is less than the set convergence threshold, or the number of iterations... Once the maximum number of iterations is reached, the stopping condition is triggered, the iteration loop ends, and the final two-parameter model of the underground medium is output. If the stopping condition is not met, then let Return to step S3-2-2 and enter the next loop; S3-2-7, Extracting abnormal crack distribution: Based on the final output model Calculate the final distribution of model parameter changes. .

3. The method for identifying and sealing coal fire cracks using injection and detection separation according to claim 2, characterized in that, In step S3-2-1, the initial background model The construction process is as follows: The background field multi-physical quantity data vector... As input, combining prior information from the geological borehole columnar section and electrical / magnetic logging curves of the area, a three-dimensional initial physical property distribution grid of the subsurface space is established using a conventional smoothing inversion algorithm. Each grid is assigned initial electrical conductivity and magnetic permeability values, thus forming the initial background model. ; In step S3-2-2, the theoretical response of the current model Current joint sensitivity Jacobian matrix The construction process is as follows: establish the governing equations of the DC steady electric field and the static magnetic field in the three-dimensional medium respectively, and use them as physical forward modeling operators; For high-density electrical resistivity tomography (EDT), the Poisson equation describing the steady-state electric field distribution is established: in, For divergence operators, For gradient operators, For electrical conductivity, Potential, conductivity With potential All change with the three-dimensional spatial coordinates; The current density supplied to the point power source. For current intensity, For the Dirac function, The position vector of the point power source; Let be the position vector of any point in three-dimensional space; For in-well magnetic measurements, an integral equation for the static magnetic field describing the magnetization anomaly field is established: in, This is the spatial magnetic anomaly vector. The vacuum permeability; The magnetization intensity; The position vector of the observation point With the underground field source point location vector The difference is such that its modulus length is ; Unit vector ; The integral volume of the three-dimensional space containing the underground anomaly; The Poisson equation and the static magnetic field integral equation for a stable electric field distribution are discretized and solved using the finite element method or finite volume method to obtain the theoretical response of the current model. The partial derivative matrix is ​​extracted to update the current joint sensitivity Jacobian matrix. The partial derivative matrix is ​​formed by splicing the potential partial derivative submatrix of the current high-density electrical resistivity tomography and the magnetic field partial derivative submatrix of the current well magnetic survey.

4. The method for identifying and sealing coal fire cracks using injection and detection separation according to claim 1, characterized in that, In step S4, the amount of grout injected with the tracer sealing material The calculation formula is: in, The slurry diffusion loss coefficient; Inverted volume of the crack space for effective filling of the tracer medium; The total number of 3D meshes for imaging. For the index number of the grid cell, ; For the first The geometric volume of a single element in a grid; For the first The equivalent crack porosity of each grid is calculated based on the Archie formula; For the first The change in inverted conductivity of each grid; The conductivity of the tracer medium; This represents the cementation index.

5. The method for identifying and sealing coal fire cracks using injection and detection separation according to claim 1, characterized in that, Step S4 specifically includes the following steps: S4-1, Grouting and Sealing: Based on the three-dimensional spatial distribution of cracks obtained in step S3, key crack channels are identified as grouting and sealing target points, and tracer sealing materials with pre-placed conductive and magnetic components are injected into the sealing target points. S4-2, Re-scanning and Inversion: After the tracer sealing material has solidified, repeat step S2 to obtain multi-physical quantity data vectors including potential data and magnetic field data after sealing, and perform inversion imaging; S4-3, Verification of Blocking Effectiveness: The latest inversion imaging results are compared with the actual grouting project parameters for judgment: Validity is determined as follows: If a dual-physics anomaly matching the electromagnetic response characteristics of the tracer sealing material is detected in the three-dimensional region of the original crack target, and the inversion volume is obtained through the voxel integral formula, then the inversion is valid. Compared with the actual recorded grouting volume If the error between the two is within the set allowable threshold range, the grouting and sealing are deemed effective. Invalidity and Anomaly Handling: If any of the following situations occur: A. No obvious electromagnetic anomaly is detected in the target's three-dimensional region; B. The electromagnetic anomaly region deviates significantly from the set blocking target point; C. The inverted volume... If the ratio of the actual grouting volume to the total grouting volume is less than 0.7, the grouting and sealing are deemed ineffective.

6. A coal fire crack identification and sealing system based on injection and detection separation, the sealing system being used to implement the coal fire crack identification and sealing method based on injection and detection separation as described in claim 1, characterized in that, include: A drilling unit is a network of boreholes, including injection holes and observation holes, used for drilling operations in coal-fired areas. The crack identification unit includes an injection component for injecting a tracer medium into the injection hole, an electromagnetic detection component for performing a combined electromagnetic scan into the observation hole to obtain potential and magnetic field data, and an analysis component for building a model to obtain the three-dimensional spatial distribution of the crack and verifying the effectiveness of the sealing. The plugging unit has plugging components for injecting tracer plugging material into the borehole; The control unit, connected to the drilling unit, fracture identification unit, and sealing unit, controls the actions of each unit: first, it controls the drilling unit to drill in the coal fire area to form a borehole network; after the borehole network is completed, the control unit controls the electromagnetic detection component to obtain the background electromagnetic response data vector before injection; then, it controls the injection component to continuously inject the tracer medium into one or more injection holes; during or after injection, the control unit controls the electromagnetic detection component to obtain the excitation field electromagnetic response data vector; after the analysis component constructs a model to obtain the three-dimensional spatial distribution of the fracture, the control unit controls the sealing unit to inject tracer sealing material into the borehole.

7. A coal fire crack identification and sealing system based on injection and detection separation according to claim 6, characterized in that, It also includes shallow treatment units, configured as an ecological substrate for oxygen-barrier construction on the surface after deep fire extinguishing in coalfield fire zones; The ecological matrix is ​​mixed in parts by weight, including: 15-25 parts of straw-based hydrogel microspheres, 30-40 parts of red mud-biochar composite particles, 20-30 parts of decomposed coal gangue powder, and 2-5 parts of arbuscular mycorrhizal fungi encapsulation slow-release agent. After mixing the ecological substrate with water, spread it on the surface of the fire area with a thickness of ≥20cm.

8. A coal fire crack identification and sealing system based on injection and detection separation according to claim 6, characterized in that, The drilling unit has a heat-dissipating drill rod; the heat-dissipating drill rod includes: The drill rod (10) and drill bit (20) are connected to each other. The drill bit (20) is provided with a closed heat dissipation cavity (31) and the heat dissipation cavity (31) is filled with phase change material. The cooling component has an energy storage box (40) located inside the drill pipe (10) and at least one condenser box (32) located inside the energy storage box (40). The energy storage tank (40) is fixedly arranged and stores liquid cryogenic working fluid inside. The condenser (32) is connected to the drive component (60) and is driven to move radially. Under the action of the drive component (60), when the temperature inside the drill rod (10) exceeds the first temperature threshold, the condenser (32) moves radially to the position of contact with the energy storage tank (40). When the temperature inside the drill rod (10) drops below the second temperature threshold, the condenser (32) moves radially to the position of separation from the energy storage tank (40). Alternatively, when the rotation speed of the drill rod (10) exceeds the first rotation speed threshold, the condenser (32) moves radially to the position of contact with the energy storage tank (40). When the rotation speed of the drill rod (10) drops below the second rotation speed threshold, the condenser (32) moves radially to the position of separation from the energy storage tank (40). Wherein, the first temperature threshold is greater than the second temperature threshold, and the first rotation speed threshold is greater than the second rotation speed threshold. The condenser (32) and the heat dissipation chamber (31) are connected by an evaporation pipe (33) and a return pipe (34) to form a closed loop, so that the phase change material can evaporate from the heat dissipation chamber (31) into the condenser (32) and then flow back into the heat dissipation chamber (31).

9. A coal fire crack identification and sealing system based on injection and detection separation according to claim 8, characterized in that, The drive component (60) has a support cylinder (62), a support rod (64), and a shape memory alloy component (61). One end of the support rod (64) moves to be located inside the support cylinder (62) and contacts the elastic element (63), while the other end is fixedly connected to the condenser box (32); The support cylinder (62) is provided with an elastic element (63). The elastic element (63) contacts the inner wall of the support cylinder (62) and the support rod (64) respectively. Under the action of the elastic element (63), the support rod (64) bears the elastic force towards the axis of the drill rod (10). Under the action of centrifugal force, the support rod (64) moves to compress the elastic element (63). The shape memory alloy part (61) is close to the axis of the drill rod (10). One end of the shape memory alloy part (61) is fixed and the other end is fixedly connected to the support cylinder (62). The drill bit (20) is provided with a heat-conducting plate (22). One end of the heat-conducting plate (22) extends and connects to the shape memory alloy part (61). When the temperature reaches the first temperature threshold, the shape memory alloy part (61) is heated and elongated. or: The drill bit (20) is equipped with a temperature sensor, and the drill rod (10) end is equipped with an angular velocity sensor for sensing the rotation speed of the drill rod (10). The drive component (60) is a drive rod and is fixed inside the drill rod (10). The wires of the temperature sensor, angular velocity sensor, and drive rod are first led out through an electric slip ring and then connected to the controller, which controls the movement of the drive rod.

10. A coal fire crack identification and sealing system based on injection and detection separation according to claim 8, characterized in that, Also includes: The central tube (50) has a hollow structure and is coaxially located inside the drill rod (10) and the drill bit (20); The drill rod (10) includes an inner drill rod and an outer drill rod, and an annular cavity (13) is formed between the inner drill rod and the outer drill rod. The inner drill rod is provided with a secondary vent (11) that communicates with the annular cavity (13). The lower end of the annular cavity (13) is provided with a main vent (12) that communicates with the outside, and the upper end is connected to the first high-pressure air source through the first rotary joint. The main vent (12) is inclined and the lower end faces the drill bit (20). The energy storage box (40) is located inside the inner drill rod and has a pressure relief valve (41) connected to the auxiliary vent (11) at the upper end. The cryogenic working fluid is liquid nitrogen; The central tube (50) is equipped with a cap (21) at one end of the drill bit (20) and can be switched to the slag discharge box and the second high-pressure gas source at the other end of the drill rod (10) through the second rotary joint. The end cap (21) is configured to open the central tube (50) port when subjected to pressure from below and close the central tube (50) port when subjected to pressure from above. The controller controls the inlet pressure of the first high-pressure gas source and the second high-pressure gas source.

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