A multi-working mode coordinated mining well pattern and a mining method thereof

Abstract

The application discloses a multi-working mode coordinated exploitation well pattern and an exploitation method thereof, and belongs to the technical field of coal bed gas exploitation. The exploitation well pattern comprises a first horizontal well and a second horizontal well, the first horizontal well and the second horizontal well form a communication channel in a target coal bed, and the communication channel is used for selectively accelerating extraction of coal bed gas or serving as a reaction channel for underground coal gasification; and the exploitation well pattern further comprises a multifunctional well, which is communicated with the communication channel. The application constructs a multi-working mode coordinated exploitation well pattern of "double horizontal wells + multifunctional well", realizes the collection of monitoring production parameters, gas production and extraction, injection of carbon dioxide reaction slurry and solidifying fluid in the multifunctional well, realizes the cooperation of CO2 filling, reinforcement, sealing and storage, and solves the problems of lack of special carbon storage channels and difficulty in multi-technology cooperation in the prior art.

Description

Technical Field

[0001] This application belongs to the field of coalbed methane extraction technology, and specifically relates to a multi-mode collaborative extraction well network and its extraction method. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) is considered by mainstream assessment reports as an important supplementary tool for achieving deep emission reduction and negative emissions. Its basic idea is to capture CO2 from emission sources or the air, and after compression / transport, it is disposed of in two ways: utilization (U) and storage (S). Utilization includes: enhanced oil and gas recovery, mineral carbonization / concrete CO2 curing (converting CO2 into carbonate cement), chemicals / synthetic fuels (such as urea, methanol, and synthetic hydrocarbons), and bio-utilization; storage includes: deep saline aquifers, depleted oil and gas reservoirs, unminable coal seams, mineralization of reactive rock masses such as basalt, and backfilling of mine goaf areas. Meanwhile, coal mine goaf areas, as byproducts of coal mining, generally have structural defects such as roof delamination, mining-induced fractures, and residual voids, which can easily lead to a series of risks such as surface subsidence, stress redistribution, ventilation disturbances, and spontaneous combustion of residual coal, threatening the ecological security of the mining area and the surrounding production and living order. Therefore, CO2 sequestration and the reuse of resources from abandoned mines have become important directions for industry development. While current technologies have formed their own systems in areas such as goaf remediation, engineering applications of CO2 in coal mines / coal seams, resource recovery from abandoned mines, and shaft cementing, there are still many gaps in the synergistic integration of multiple technologies. The specific background and current status of technological development are as follows:

[0003] I. The basis and limitations of traditional technologies for treating goaf areas

[0004] To address the structural risks in goaf areas, traditional remediation techniques focus on grouting and filling. The core objective is to increase the overall modulus of the rock mass by filling voids, forming a load-bearing arch structure to suppress surface subsidence. Mainstream techniques can be categorized into three types: First, delamination grouting technology, which involves drilling holes in the overburden delamination zone and injecting a highly fluid grout such as a cement-fly ash-water glass system to achieve delamination closure and "secondary bonding"; second, segmented / deep-hole grouting and strip grouting filling technology, which targets large-scale, irregular goaf areas by using segmented pressure control, strip-based hole layout, and repeated grouting processes to ensure the grout diffusion radius and filling uniformity; and third, a supporting material system, using ordinary Portland cement or composite cement as the matrix, compounded with fly ash, slag, bentonite, and quick-setting / early-strength agents to balance the pumpability, initial setting time, and early strength requirements of the grout material.

[0005] Although traditional grouting filling technology has achieved remarkable results in mechanical reinforcement and settlement reduction, the core of the technology design focuses on the optimization of mechanical properties, without considering the impact of long-term CO2 contact and erosion on the durability of the filling body. Furthermore, it lacks a systematic design that incorporates permanent CO2 carbon sequestration into the governance system, making it difficult to meet the needs of coordinated development of "governance-carbon sequestration".

[0006] II. Progress in the Engineering Application of CO2 in the Coal Mining Sector

[0007] The application of CO2 in coal mines and coal seam engineering has formed several technical directions, providing a technical foundation for goaf management and carbon sequestration synergy: First, CO2 injection into goaf fire suppression technology utilizes the inerting and oxygen-reducing properties of CO2 to construct an inerting zone within the goaf, reducing the risk of spontaneous combustion and reignition of residual coal. Some studies and applications have found that a small amount of CO2 can be trapped simultaneously, but a synergistic design with grouting and filling and material mineralization has not yet been formed. Second, CO2 displacement of methane in unminable coal seams (ECBM) technology relies on the preferential adsorption characteristics of CO2 on coal. By injecting CO2 to replace CH4 in the coal seam, CO2 sequestration is achieved while improving coalbed methane recovery. Its effectiveness is affected by factors such as coal rank, temperature and pressure conditions, and fracture-matrix coupling characteristics. Third, underground coal gasification (UCG) well network technology uses injection wells and production wells (mainly directional / horizontal wells) to connect coal seams to achieve in-situ gasification. Currently, multi-well collaboration and reserved monitoring / injection channels are becoming development trends.

[0008] III. Current Status of Reuse Technology for Abandoned Mines (Ground-Out Areas)

[0009] Reusing abandoned mines (goafs) is an important pathway to achieving resource recycling and ecological restoration, with methane extraction and utilization from abandoned mines (AMM) being one of the core directions. AMM refers to methane trapped in unmined coal seams, mining-disturbed zones, and goaf voids after mine closure, representing a significant gas source during the "closure and abandonment" phase of a coal mine's life cycle. Currently, typical AMM extraction pathways include cross-border extraction from adjacent abandoned mines by operating mines, direct extraction from goafs via surface drilling, and underground sealed walls / buried pipe extraction. Extraction capacity is primarily constrained by factors such as sealing quality, negative pressure (5–40 kPa), mine water inflow, and channel resistance. Reuse scenarios have expanded to power generation, heating, and chemical industries. Furthermore, residual coal can be reused through UCG / in-situ pyrolysis, providing possibilities for coordinated development with goaf remediation and CO2 storage.

[0010] IV. Challenges and Countermeasures of Wellbore Cementing Technology in CO2 Environment

[0011] In oil and gas, geothermal and CO2 injection-storage well projects, the CO2 environment (especially supercritical CO2 coexisting with water) is prone to carbonization and decalcification of cement stone, resulting in weakened cement stone strength. It is also easy to form microchannels at the casing-formation interface, which greatly reduces the long-term sealing performance of the wellbore. This problem is also prominent in the coordinated engineering of goaf remediation and CO2 storage.

[0012] To address these challenges, the industry has developed three main countermeasures: First, developing CO2-resistant cement formulations by incorporating components such as aluminate cement (CAC), fly ash, silica fume, and nano-SiO2 to regulate the cement stone phase composition and densify the structure, thereby reducing Ca(OH)2 content and enhancing carbonation resistance; second, employing foamed cementing or hollow microsphere density reduction technologies to match formation mechanical properties and improve the casing-formation interface bonding; and third, optimizing interface engineering by improving displacement procedures to enhance interfacial shear strength and resistance to microchannel formation. However, existing technologies primarily focus on solving single-wellbore sealing problems and have not achieved integrated collaborative design with "waste resource reuse—goaf backfilling—mineralization preservation—wellbore cementing," making it difficult to adapt to the complex collaborative governance needs of goaf areas.

[0013] V. Overview and Core Limitations of Existing Related Technical Solutions

[0014] Based on technological advancements in areas such as goaf remediation, CO2 engineering applications in coal mines / coal seams, resource recycling, and shaft cementing, the current mainstream related technologies and their core limitations can be summarized as follows:

[0015] 1. Grouting and filling technologies in goaf areas (strip grouting and filling, overburden separation grouting for settlement reduction and supporting grouting systems): The core objective is to achieve settlement reduction or engineering grout delivery control through mechanical filling. The key technical points focus on hole layout design, grout formula matching and construction parameter control. However, CO2 mineralization reaction, permanent storage and metering are generally not included in the design system, and they are isolated from wellbore cementing technology, making it difficult to form a synergistic effect of "treatment-carbon fixation-sealing".

[0016] 2. CO2 injection application technologies (goaf suppression, ECBM): The former relies on inerting characteristics to achieve safety control. Although it can trap a small amount of CO2, it is not linked with grouting and filling and material mineralization, and cannot form a long-term structural seal. The latter focuses on improving coalbed methane recovery and CO2 storage, with a core focus on the characteristics of the coal seam itself. It lacks sufficient coordination design for goaf structural backfilling and wellbore cementing, as well as the metering coverage of storage within the same well network.

[0017] 3. Mine resource development technologies (UCG / CSG multi-well configuration): The mainstream solution adopts a dual-well mode of "injection well + production well", which focuses on controlling the in-situ gasification front or gas extraction efficiency. It does not set up a dedicated well as a CCUS channel, nor does it achieve integrated support for reaction grouting backfill, CO2-resistant cementing and metering monitoring through functional segmentation.

[0018] 4. CO2-resistant well cementing technology: Although the durability of a single well in a CO2 environment has been improved through formula optimization and construction improvements, it is not designed in conjunction with goaf backfilling and CO2 sealing metering within the same well network system, and cannot meet the full-process requirements of goaf treatment and CO2 sealing collaborative engineering.

[0019] In summary, existing technologies have laid a certain foundation in areas such as goaf remediation, CO2 engineering applications, waste resource recycling, and wellbore cementing. However, an integrated technical system covering "risk management, resource recovery, CO2 storage, and long-term sealing" has not yet been formed. Problems such as the lack of dedicated well network configuration, insufficient multi-technology collaboration, and lack of storage metering have become the core technical bottlenecks restricting the green and collaborative governance of coal mine goaf and the implementation of "dual carbon" goals. Summary of the Invention

[0020] To address the aforementioned issues, this application provides a multi-mode collaborative well network and its extraction method. The aim is to establish a multi-mode collaborative well network with a core architecture of "dual horizontal wells + multi-functional wells" to achieve an integrated engineering path of "waste resource reuse—goaf remediation—long-term wellbore sealing—CO2 storage." By integrating monitoring of production parameters, gas extraction, injection of carbon dioxide reaction slurry, and cementing fluid, the network achieves a synergistic effect of filling, reinforcement, sealing, and storage in the physical engineering process. Through multi-functional wells, an auditable record of CO2 destination is created to support the achievement of the "utilization + storage" objectives and operational decisions.

[0021] The first objective of this application is to provide a multi-mode collaborative mining well network, including a first horizontal well and a second horizontal well, wherein the first horizontal well and the second horizontal well form a connecting channel in the target coal seam, and the connecting channel is used to selectively accelerate the extraction of coalbed methane or as a reaction channel for underground coal gasification.

[0022] It also includes a multi-functional well, which is in fluid communication with the connecting channel.

[0023] In a specific embodiment of this application, the multi-functional well is divided into multiple segments along the well depth direction, including a first segment, a second segment, and a third segment, with packers provided between each pair of the first segment, the second segment, and the third segment;

[0024] Along the well depth direction, the second segment and the third segment are arranged in sequence, and the interface between the second segment and the third segment is not lower than the interface between the target coal seam and the overburden layer covering the target coal seam;

[0025] Several sensors are installed on the cylinder wall of the first section;

[0026] The third section of the well shaft is provided with several construction holes on its wall and valves are also provided on the third section of the well shaft.

[0027] The wellhead of the multi-functional well is equipped with a reversing valve assembly and an interface flange.

[0028] In a specific embodiment of this application, the multi-functional well is further provided with a fourth section. The third section and the fourth section are arranged in sequence along the well depth direction. A packer is provided between the third section and the fourth section. The wellbore located in the fourth section is connected to a pumping screen pipe. An ignition element is installed at the bottom of the fourth section.

[0029] In a specific embodiment of this application, the multi-working-mode collaborative well network further includes a surface supply unit, a pumping unit, a data unit, an ignition unit, and a monitoring unit.

[0030] The surface supply unit is used to connect to the injection port of the multi-functional well;

[0031] The pumping unit is used to connect to the pumping port of the multi-functional well;

[0032] The ignition unit is used to connect with the ignition element in the multi-functional well;

[0033] The monitoring unit is used to connect to the sensors in the multifunctional well;

[0034] The data unit is used to store monitoring data on pressure, temperature, fluid properties, and recovery / return volume in the multi-functional well.

[0035] The second objective of this application is to provide a multi-mode collaborative mining method, which employs a multi-mode collaborative mining well network, including working mode B, working mode C and working mode D.

[0036] The working mode B is the extraction mode, which includes: gas extraction or well testing in the target coal seam (400) through a multi-functional well (200);

[0037] The working mode C is the injection mode, which includes: injecting cementing fluid into the second section (220) of the multi-functional well (200) or injecting carbon dioxide reaction slurry into the target coal seam (400) through the multi-functional well (200);

[0038] The working mode D is the production parameter monitoring mode, which includes: measuring and monitoring pressure, temperature, fluid properties and recovery / return volume.

[0039] In a specific embodiment of this application, the working mode B is applicable to the following scenarios:

[0040] Scenario 1: The gas pressure of the target coal seam is greater than or equal to the preset value;

[0041] Scenario 2: When the gas concentration of the target coal seam reaches the utilization standard;

[0042] Scenario 3: Accelerating gas source recovery through coordinated "dual horizontal wells".

[0043] In a specific embodiment of this application, the system switches to operating mode C when one of the following conditions is met:

[0044] Scenario 4: When the extraction of the target gas source ends;

[0045] Scenario 5: When the volume of the goaf in the target coal seam reaches the design value for filling;

[0046] Scenario 6: When performing CO2 engineering trapping.

[0047] In a specific embodiment of this application, the working mode D is adapted to the following scenarios:

[0048] Scenario 10: During the entire project lifecycle;

[0049] Scenario 11: Long-term stability assessment and inventory audit phase after operation is stopped.

[0050] In a specific embodiment of this application, the multi-working-mode collaborative mining method further includes working mode A;

[0051] The operating mode A is the ignition and combustion control mode, including:

[0052] Ignition is achieved through the ignition element in the fourth section of the multi-functional well;

[0053] During the gasification process, combustion / extinguishing control is achieved by injecting a gaseous medium into the fourth section of the multi-functional well.

[0054] During ignition or combustion / extinguishing control, pressure and temperature changes are monitored by multi-functional in-well sensors.

[0055] In a specific embodiment of this application, the working mode A is adapted to the following scenarios:

[0056] Scenario 7: Obtaining energy through underground coal gasification;

[0057] Scene 8: Underground gasification is in the initial ignition stage;

[0058] Scenario 9: When the combustion surface shape needs to be adjusted during underground coal gasification.

[0059] Compared with the prior art, this application has the following advantages:

[0060] This application provides a multi-mode collaborative mining well network and its mining method, which constructs a multi-mode collaborative mining well network of "dual horizontal wells + multi-functional wells". The multi-functional wells realize the integration of multiple functions such as monitoring production parameters, gas extraction, injection of carbon dioxide reaction slurry and cementing fluid, and realize the synergy of CO2 filling, reinforcement, sealing and storage. It solves the problem that the existing well network organization of goaf areas caused by abandoned mine goaf gas drainage (CSG) or deep coal in-situ gasification (UCG) in difficult mining has no dedicated CCUS channel wells, which leads to difficulties in goaf management and deep coal seam mining.

[0061] Furthermore, the multi-working-mode collaborative well network in this application can be improved from the existing horizontal well network, with a short construction cycle;

[0062] Furthermore, the multi-functional well in this application can achieve the coordination of working mode B, working mode C and working mode D by simply dividing it into multiple sections (first section, second section and third section) and setting up the reversing valve group and interface flange at the wellhead, as well as realize the activation or switching of working mode B based on real-time monitored production parameter data.

[0063] Furthermore, the multi-functional well in this application is equipped with a fourth section, which enhances the ignition and combustion control of the multi-functional well and realizes the working mode A of the well network.

[0064] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0065] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0066] Figure 1 A schematic diagram of a multi-working-mode collaborative well network is shown according to certain embodiments of this application;

[0067] Figure 2A schematic diagram of the structure of a multifunctional well according to certain embodiments of this application is shown;

[0068] In the picture:

[0069] 100. Surface; 101. Filtration device; 102. Storage tank; 103. Mixing device; 200. Multifunctional well; 201. Injection port; 202. Drainage port; 203. Cable port; 210. First section; 211. First sensor; 212. Second sensor; 213. Outer casing; 220. Second section; 221. Cementing layer; 230. Third section; 231. Construction hole; 232. Valve; 240. Fourth section; 241. Drainage screen; 242. Ignition element; 250. Packer; 260. Central tubing string; 300. Overburden layer; 400. Target coal seam; 500. Bottom strata; 600. First horizontal well; 700. Second horizontal well. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0071] like Figure 1 As shown, a multi-operation mode collaborative mining well network according to certain embodiments of this application includes a first horizontal well 600 and a second horizontal well 700. The first horizontal well 600 and the second horizontal well 700 form a connecting channel in the target coal seam 400. The connecting channel is used to selectively accelerate the extraction of coalbed methane or to implement the in-situ coal gasification process.

[0072] It also includes a multi-functional well 200, which is connected to the communication channel and generates fluid and pressure coupling with the communication channel;

[0073] The first horizontal well 600 and the second horizontal well 700 serve as underground connecting channels for coalbed methane extraction, constructing a gasification flow field, and as backflow monitoring channels during grouting operations to regulate filling pressure and slurry circulation.

[0074] The multi-functional well 200 is used to monitor production parameters, gas production and drainage, injection of carbon dioxide reaction slurry and cementing fluid, and realizes functions such as drainage, grouting and production parameter monitoring. The production parameters include temperature, pressure, fluid properties, and recovery / return volume.

[0075] The multi-functional well 200 is also used for ignition and injection of gas medium to realize ignition and combustion control functions;

[0076] In this application, the multi-functional well 200 is a vertical well or an inclined well.

[0077] like Figure 1 As shown, for ease of understanding of stratigraphic division, in the vertical direction, the stratum covering the target coal seam 400 is the overburden 300, the surface of the overburden 300 is the surface 100, and the stratum below the target coal seam 400 is the base stratum 500.

[0078] like Figure 2 As shown, in some embodiments of this application, the multi-functional well 200 is provided with a central tubing string 260 to ensure the multi-functional configuration of the multi-functional well 200. Along the well depth direction, the multi-functional well 200 is divided into a first segment 210, a second segment 220 and a third segment 230. A packer 250 is provided between each pair of the first segment 210, the second segment 220 and the third segment 230. Along the well depth direction, the second segment 220 and the third segment 230 are arranged sequentially.

[0079] The first segment 210 is used to realize the production parameter monitoring function of the multi-functional well 200. Correspondingly, several sensors are provided in the first segment 210 for monitoring temperature and pressure. The central tubing 260 located in the first segment 210 is covered with an outer tube 213. The materials of the central tubing 260 and the outer tube 213 are materials well known in the art, and this application does not make specific limitations on them.

[0080] For example, the sensor includes a first sensor 211 and a second sensor 212, wherein the first sensor 211 is a temperature sensor and a pressure sensor, and the second sensor 212 is a distributed optical fiber sensor;

[0081] The second segment 220 is used to realize the cementing function of the multi-functional well 200 (the output port of the first injection channel is set in the second segment 220). The central tubing 260 located in the second segment 220 is covered with a cementing layer 221, which is obtained by solidification of cementing fluid. The second segment 220 is located in the overburden 300.

[0082] The third section 230 is used to realize the grouting function of the multi-functional well 200 (the output port of the second injection channel is set in the third section 230). A number of construction holes 231 are provided on the cylinder wall of the central tubing 260 located in the third section 230. The construction holes 231 are set as perforation windows or nozzles to facilitate the injection of carbon dioxide reaction slurry into the target coal seam 400 through the construction holes 231.

[0083] A valve 232 is also provided on the wellbore of the central tubing 260 located in the third section 230. The valve 232 is a one-way valve, a check valve, or a back pressure valve to prevent the injected slurry or cementing fluid from flowing out and backflowing. The valve 232 or the access port 231 is configured to open under a specific pressure so as to remain closed when injecting gas medium into the fourth section 240 to prevent gas from leaking prematurely in the third section 230.

[0084] To ensure that the second segment 220 is located in the overburden 300, the interface between the second segment 220 and the third segment 230 shall not be lower than the interface between the target coal seam 400 and the overburden 300;

[0085] The wellhead of the multi-functional well 200 is equipped with a reversing valve group and an interface flange, which facilitates the rapid switching between the injection and pumping functions of the multi-functional well 200.

[0086] For example, the reversing valve assembly and interface flange include an injection port 201 (connecting the first injection channel and the second injection channel), a pumping port 202, and a cable port 203. The injection port 201 is used to connect to the output port of the injection equipment, the pumping port 202 is used to connect to the power unit of the pumping unit and discharge the produced gas, and the cable port 203 is used for laying power lines, signal control lines, and data acquisition lines for sensors and other electrical equipment in the multifunctional well 200.

[0087] The first segment 210 can be located at the upper end or the bottom end of the multi-functional well 200. For example, Figure 2 In the well, the first segment 210, the second segment 220 and the third segment 230 are arranged in sequence along the well depth direction.

[0088] In some embodiments of this application, the multi-functional well 200 is further provided with a fourth section 240. Along the well depth direction, the third section 230 and the fourth section 240 are arranged in sequence, and a packer 250 is provided between the third section 230 and the fourth section 240.

[0089] The fourth section 240 is used to realize the ignition and combustion control functions of the multi-functional well 200. A extraction screen pipe 241 is connected to the central tubing 260 located in the fourth section 240. An ignition element 242 is installed at the bottom of the fourth section 240.

[0090] For example, the ignition element 242 is preferably a high-energy discharge electric ignition head (often a heating probe based on molybdenum disilicide (MoSi2) or silicon carbide (SiC) material), which is installed in the end tubing of the fourth section 240. The high-voltage pulse current output by the high-energy ignition unit at the wellhead generates a spark at the bottom of the well to ignite the coal seam.

[0091] Injecting a gaseous medium into the fourth section 240 (through the injection port 201 and the injection channel) completes the combustion-supporting / flame-extinguishing control in some embodiments of this application (when supporting combustion, a flame-retardant gas such as oxygen is injected; when extinguishing, a non-flammable gas such as carbon dioxide or air can be injected, or the volume ratio of the combustion-supporting gas and the non-flammable gas can be adjusted to achieve flame-extinguishing control).

[0092] In some embodiments of this application, the multi-operating-mode collaborative well network further includes a surface supply unit, a pumping unit, a data unit, an ignition unit, and a monitoring unit.

[0093] The surface supply unit is used to connect to the multi-functional well 200 and inject cementing fluid into the second section 220 of the multi-functional well 200, inject carbon dioxide reaction slurry into the third section 230 of the multi-functional well 200, or inject gas medium into the fourth section 240 of the multi-functional well 200.

[0094] The pumping unit is used to connect to the multi-functional well 200, provide power to the multi-functional well 200, and perform gas production pumping or well testing.

[0095] The ignition unit is used to control the connection of the ignition element 242 in the multi-functional well 200;

[0096] The monitoring unit is used to connect with the sensors in the multi-functional well 200 to monitor the pressure, temperature, fluid properties, and recovery / slurry volume data in the multi-functional well 200.

[0097] The data unit is used to store the pressure, temperature, fluid properties, and recovery / return volume data obtained from the monitoring of the multi-functional well 200.

[0098] like Figure 1 As shown, in some embodiments of this application, the ground supply unit, for example, includes a filter device 101, a storage tank 102, and a stirring device 103;

[0099] The carbon dioxide reaction slurry is injected through the third section 230 of the multi-functional well 200, and is filled and transported in the connecting channel of the target coal seam 400. When the grouting pressure or volume reaches the design requirements, the overflow slurry is returned to the surface through the first horizontal well 600 and the second horizontal well 700, filtered in the filter device 101, and stored in the storage tank 102, which can be used as a circulating grouting material for reinjection.

[0100] The carbon dioxide reaction slurry in storage tank 102 is stirred by the stirring device 103 and then injected into the multifunctional well 200.

[0101] In the embodiments of this application, the sensors, ignition element 242, exhaust power component, and injection power component involved are all devices well known in the art, and their installation is also well known in the art. Therefore, this application does not make specific limitations.

[0102] According to a certain example of the present application, a multi-operation mode collaborative mining method is adopted, which employs a multi-operation mode collaborative mining well network, including operation mode B, operation mode C and operation mode D.

[0103] The working mode B is the extraction and sorting mode (i.e., CSG extraction and sorting), which includes:

[0104] By connecting the extraction port 202 of the wellhead of the multi-functional well 200 to the extraction equipment in the ground supply unit, gas production extraction or well testing can be carried out in the fourth section (240) of the target coal seam 400 and its extraction screen pipe (241) through the multi-functional well 200.

[0105] The working mode C is the injection mode (i.e., CCUS grouting / injection, which can achieve synergy in the mining of 400 gas in the target coal seam, goaf treatment, and engineered CO2 trapping), including:

[0106] By connecting the injection port 201 at the wellhead of the multi-functional well 200 to the injection equipment (storage tank 102, stirring device 103, etc.) in the ground supply unit, cementing fluid is injected into the second section 220 of the multi-functional well 200 or carbon dioxide reaction slurry is injected into the target coal seam 400 through the multi-functional well 200. The target coal seam 400 is a mining area, which is also a goaf in the goaf treatment. Therefore, the working mode C can realize both CO2 reaction grouting backfilling (i.e. goaf treatment) and cementing (which can be used for secondary cementing in the case of wellbore leakage during injection and production).

[0107] The working mode D is for production parameter monitoring, including:

[0108] By connecting the sensors deployed in the first section 210 of the multifunctional well 200 to the monitoring unit, real-time measurement and monitoring of pressure, temperature, fluid properties and recovery / slurry volume can be achieved.

[0109] In some embodiments of this application, in secondary cementing, the cementing fluid is a CO2-resistant slurry well known to those skilled in the art; the CO2-resistant slurry needs to have high fluidity and corrosion resistance, preferably a commercially available modified CO2-resistant cement slurry (such as a composite material incorporating fly ash or aluminate cement) or a high-performance synthetic resin (such as epoxy resin or polyurethane plugging agent) to meet the needs of wellbore microfracture plugging and long-term sealing in acidic environments.

[0110] The high-performance synthetic resin includes epoxy resin or polyurethane plugging agent, does not contain solid particles, and is used to repair wellbore micro-leakage. It is a material well known in the art. This application does not specifically limit the high-performance synthetic resin.

[0111] The CO2-resistant foamed cementing material is a well-known material in this field. It improves the bonding state between the casing and the formation by introducing inert gas into the slurry to form a microbubble structure. This application does not specifically limit the high-performance synthetic resin.

[0112] In some embodiments of this application, the operating mode B is applicable to the following scenarios:

[0113] Scenario 1: The gas pressure in the target coal seam 400 is greater than or equal to a preset value. For example, the preset value is 0.1 MPa. Scenario 1 means that the gas pressure in the target coal seam 400 reaches the preset value, and the working mode B (starting CSG drainage) is activated.

[0114] Scenario 2: When the gas concentration of the target coal seam 400 reaches the utilization standard, the utilization standard is the same as the preset value of gas pressure in Scenario 1. That is, when the gas concentration of the target coal seam 400 reaches the threshold, the working mode B (starting CSG drainage) is activated.

[0115] Scenario 3: When it is necessary to coordinate with "dual horizontal wells" ("dual horizontal wells" refer to the first horizontal well 600 and the second horizontal well 700) to accelerate gas source recovery, the multi-functional well 200 is activated for auxiliary extraction to accelerate gas source recovery;

[0116] In operating mode B, due to the fluid pressure coupling between the multi-functional well 200 and the first horizontal well 600 and the second horizontal well 700, the intervention of the multi-functional well 200 will significantly reduce the local pressure, thereby accelerating the gas source recovery in the "dual horizontal well" control area (i.e., the radiation area of ​​the first horizontal well 600 and the second horizontal well 700).

[0117] In some embodiments of this application, the operating mode C is switched when one of the following conditions is met:

[0118] Scenario 4: When the extraction of the target gas source ends, the target gas source includes coalbed methane (CSG) and syngas produced by underground coal gasification (UCG);

[0119] Scenario 5: When the volume of the goaf in the target coal seam 400 reaches the design value for filling;

[0120] Scenario 6: When implementing engineered CO2 storage to meet emission reduction targets.

[0121] In some embodiments of this application, the operating mode D is adapted to the following scenarios:

[0122] Scenario 10: During the entire operation cycle of the project, the project refers to the mining of the target coal seam with 400 methane, the treatment of the goaf, and the engineering-based storage of CO2, which serves as real-time monitoring data for production parameters.

[0123] Scenario 11: Long-term stability assessment and inventory audit phase after operation is stopped.

[0124] In some embodiments of this application, the multi-working-mode collaborative mining method further includes working mode A;

[0125] The operating mode A is the ignition and combustion control mode (UCG ignition and combustion control mode), including:

[0126] Ignition is achieved through the ignition element 242 of the fourth section 240 in the multi-functional well 200;

[0127] During the gasification process, combustion / extinguishing control is achieved by injecting gas medium into the fourth section 240 of the multi-functional well 200;

[0128] During ignition or combustion / extinguishing control, pressure and temperature changes are monitored by sensors in the multi-functional well 200.

[0129] In some embodiments of this application, the operating mode A is adapted to the following scenarios:

[0130] Scenario 7: When obtaining energy through underground coal gasification, it is generally used for deep and difficult-to-mine coal seams. Working mode A can assist in ignition and improve the ignition success rate.

[0131] Scenario 8: Underground gasification is in the initial stage of ignition. Working mode A can assist in ignition and improve the ignition success rate.

[0132] Scenario 9: When the combustion surface morphology needs to be adjusted during underground coal gasification, auxiliary ignition is performed using working mode A to expand the combustion range or correct the direction of the combustion front, that is:

[0133] When uneven propulsion or localized flameout occurs at the combustion front (combustion surface) of the main gasification channel, the multi-functional well 200 can be used for targeted auxiliary ignition, which can induce the fire zone to move to that position or reactivate the reaction zone.

[0134] In some embodiments of this application, the mining method includes:

[0135] Deploy a mining well network with multiple working modes (working mode A, working mode B, working mode C and working mode D) in coordination;

[0136] Multiple working modes are selected for construction based on production needs, including actual process requirements for gas extraction, goaf treatment, and CO2 engineering storage.

[0137] Control the switching between multiple working modes based on the production data obtained from monitoring.

[0138] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A multi-mode collaborative well network for mining operations, characterized in that, It includes a first horizontal well (600) and a second horizontal well (700), the first horizontal well (600) and the second horizontal well (700) forming a connecting channel in the target coal seam (400), the connecting channel being used to selectively accelerate the extraction of coalbed methane, or as a reaction channel for underground coal gasification; It also includes a multi-functional well (200), which is connected to the connecting channel; Along the depth direction, the multi-functional well (200) is divided into multiple segments, including a first segment (210), a second segment (220) and a third segment (230), and packers (250) are provided between each pair of the first segment (210), the second segment (220) and the third segment (230). Along the well depth direction, the second segment (220) and the third segment (230) are arranged in sequence, and the interface between the second segment (220) and the third segment (230) is not lower than the interface between the target coal seam (400) and the overburden layer (300) covering the target coal seam (400); The multi-functional well (200) is also provided with a fourth section (240). Along the well depth direction, the third section (230) and the fourth section (240) are arranged in sequence, and a packer (250) is provided between the third section (230) and the fourth section (240). The multi-working-mode collaborative well network realizes the integration of multiple functions such as monitoring production parameters, gas production and drainage, injection of carbon dioxide reaction slurry and cementing fluid on the multi-functional well (200), and achieves the synergy of CO2 filling, reinforcement, sealing and storage. The first segment (210) is used to realize the production parameter monitoring function of the multi-functional well (200). Correspondingly, several sensors are provided in the first segment (210) for monitoring temperature and pressure. The second segment (220) is used to realize the cementing function of the multi-functional well (200). The central tubing string (260) located in the second segment (220) is covered with a cementing layer (221). The cementing layer (221) is obtained by solidification of cementing fluid. The second segment (220) is located in the overburden layer (300). The third section (230) is used to realize the grouting function of the multi-functional well (200), and a number of construction holes (231) are provided on the cylinder wall of the central tubing (260) located in the third section (230). A valve (232) is also provided on the wellbore of the central tubing (260) located in the third section (230). The valve (232) is a one-way valve, a check valve, or a back pressure valve. The fourth section (240) is used to realize the ignition and combustion control functions of the multi-functional well (200). A extraction screen pipe (241) is connected to the well barrel located in the fourth section (240), and an ignition element (242) is installed at the bottom of the fourth section (240).

2. The multi-working-mode collaborative well network according to claim 1, characterized in that, The wellhead of the multi-functional well (200) is equipped with a reversing valve assembly and an interface flange.

3. A multi-operation mode collaborative well network according to any one of claims 1-2, characterized in that, It also includes a ground supply unit, an extraction unit, a data unit, an ignition unit, and a monitoring unit; The surface supply unit is used to connect to the injection port (201) of the multi-functional well (200); The pumping unit is used to connect to the pumping port (202) of the multi-functional well (200); The ignition unit is used to connect to the ignition element (242) in the multi-functional well (200); The monitoring unit is used to connect to the sensors in the multifunctional well (200); The data unit is used to store the pressure, temperature, fluid properties, and recovery / return volume data of the multi-functional well (200) obtained from monitoring.

4. A multi-mode collaborative mining method, characterized in that, A multi-working-mode collaborative well network as described in any one of claims 1-3, comprising working mode B, working mode C and working mode D; The working mode B is the extraction mode, which includes: gas extraction or well testing in the target coal seam (400) through a multi-functional well (200); The working mode C is the injection mode, which includes: injecting cementing fluid into the second section (220) of the multi-functional well (200) or injecting carbon dioxide reaction slurry into the target coal seam (400) through the multi-functional well (200); The working mode D is the production parameter monitoring mode, which includes: measuring and monitoring pressure, temperature, fluid properties and recovery / return volume; It also includes working mode A; The operating mode A is the ignition and combustion control mode, including: Ignition is achieved through the ignition element (242) of the fourth section (240) in the multi-functional well (200); During the gasification process, combustion / extinguishing control is achieved by injecting gas medium into the fourth section (240) of the multi-functional well (200); During ignition or combustion / extinguishing control, pressure and temperature changes are monitored by sensors in the multi-functional well (200).

5. The multi-working-mode collaborative mining method according to claim 4, characterized in that, The working mode B is applicable to the following scenarios: Scenario 1: The gas pressure of the target coal seam (400) is greater than or equal to the preset value; Scenario 2: When the gas concentration of the target coal seam (400) reaches the utilization standard; Scenario 3: Accelerating gas source recovery through coordinated "dual horizontal wells".

6. The multi-working-mode collaborative mining method according to claim 4, characterized in that, Switch to operating mode C when one of the following conditions is met: Scenario 4: When the extraction of the target gas source ends; Scenario 5: When the volume of the goaf in the target coal seam (400) reaches the design value for filling; Scenario 6: When performing CO2 engineering trapping.

7. The multi-working-mode collaborative mining method according to claim 4, characterized in that, The working mode D is suitable for the following scenarios: Scenario 10: During the entire project lifecycle; Scenario 11: Long-term stability assessment and inventory audit phase after operation is stopped.

8. The multi-working-mode collaborative mining method according to claim 4, characterized in that, The working mode A is suitable for the following scenarios: Scenario 7: Obtaining energy through underground coal gasification; Scene 8: Underground gasification is in the initial ignition stage; Scenario 9: When the combustion surface shape needs to be adjusted during underground coal gasification.

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