A deep coal seam dynamic self-adaptive regulation and control fracture network capacity-increasing device and method

Abstract

The application discloses a kind of deep coal seam dynamic self-adaptive regulation and control fracture network capacity-increasing device and method, belong to CO2 geological storage technical field;Capacity-increasing device includes cylinder and gas pressure sensor;Fixed CO2 injection nozzle and second laser nozzle and angle adjustable first laser nozzle are arranged on cylinder;Gas pressure sensor detects CO2 concentration and pressure change in horizontal well in real time, adjusts the laser emission angle of first laser nozzle;By adjusting the angle of first laser nozzle, laser forms cross fracture network in target coal seam distal end or near end, expands reservoir space;The application is modified in situ by laser heating and cooperates with CO2 synchronous injection, and self-adaptive near end, distal end full coverage cross fracture network is constructed for different tightness degree coal seam, substantially improves coal seam porosity and permeability, solves deep unmineable coal seam reservoir reconstruction problem.

Description

Technical Field

[0001] This invention belongs to the field of CO2 geological storage technology, specifically a device and method for dynamically adaptively controlling fracture network expansion in deep coal seams. Background Technology

[0002] As a major coal-producing country, my country has a wide distribution of coal seams, providing potential sites for geological CO2 sequestration. This technology utilizes the strong adsorption capacity of coal for CO2 to safely and stably sequester it within the coal seam. This method not only achieves effective CO2 sequestration but also produces coalbed methane through displacement, which has dual strategic significance for ensuring energy security and promoting a green and low-carbon transformation.

[0003] However, deep, unminable coal seams often possess characteristics such as high density, low porosity, strong adsorption capacity, and reserves far exceeding those of mineable coal seams. Due to their extremely low permeability, conventional injection techniques cannot efficiently inject CO2 and allow it to diffuse within the reservoir. Therefore, how to modify the reservoir area to increase the capacity of the sequestration zone is a key technical issue in CO2 sequestration in coal seams.

[0004] Currently, common methods for enhancing the fracture network in coal seams include hydraulic fracturing, gas injection displacement, controlled electrical pulse shock waves, deep-hole pre-fracturing blasting, and CO2 phase transformation fracturing. These methods all achieve a certain degree of fracture network enhancement, but they have the following drawbacks:

[0005] 1. Hydraulic fracturing: This method involves injecting high-pressure water into the coal seam to create fractures. Cross-linked gel fracturing or liquid CO2 fracturing are commonly used. However, this method is prone to coal dust clogging the fractures, the fracturing fluid may damage the reservoir, and the equipment cost is high.

[0006] 2. Gas displacement (e.g., CO2 / N2): Injecting gas to replace methane improves desorption efficiency. This method requires controlling the risk of gas leakage, and its long-term effectiveness is limited by the reservoir's adsorption characteristics.

[0007] 3. Controlled electrical pulse shock wave: This method utilizes underwater discharge to generate shock waves, creating multi-directional fissures. It is technically complex and requires precise control of the shock wave amplitude to avoid excessive damage.

[0008] 4. Deep-hole pre-splitting blasting: By creating a fracture network through blasting, the permeability can be increased by 10-100 times. This method involves large vibrations and may cause roof collapse accidents, so strict safety measures are required.

[0009] 5. CO2 phase change fracturing: Liquid CO2 gasification and expansion fracturing of coal seams. This method requires high equipment pressure resistance, and the permeability enhancement effect is significantly affected by the hardness of the coal body. Summary of the Invention

[0010] This invention overcomes the shortcomings of existing technologies and proposes a dynamic adaptive control device and method for increasing the capacity of fracture networks in deep coal seams. It addresses the problem of low CO2 sequestration efficiency and limited capacity caused by low porosity and poor permeability in deep, unminable coal seams (usually buried at a depth of 800-1000m). The invention employs an integrated injection and expansion technology system of "laser in-situ modification - synergistic injection - dynamic control" to achieve efficient CO2 sequestration.

[0011] This invention is achieved through the following technical solution:

[0012] A dynamic adaptive control device for enhancing the fracture network in deep coal seams includes a cylinder and a gas pressure sensor. Adjustable angle support devices are installed on both sides of the outer wall of the cylinder. Each adjustable angle support device consists of multiple support plates circumferentially hinged to the outer wall of the cylinder. These support plates are connected to a drive mechanism, which drives the support plates to rotate around the hinge points. Multiple first laser nozzles are mounted on the support plates. A CO2 injection nozzle and a second laser nozzle are arranged on the outer wall of the cylinder, positioned between the first laser nozzles on both sides. A laser interlacing network is formed by the first and second laser nozzles. The gas pressure sensor is signal-connected to the drive mechanism. The gas pressure sensor is used to detect changes in CO2 concentration and pressure within the horizontal well in real time, thereby adjusting the laser emission angle of the first laser nozzles.

[0013] Furthermore, multiple rows of CO2 injection nozzles are evenly arranged along the length of the outer wall of the cylinder, and a second laser nozzle is set between two adjacent rows of CO2 injection nozzles. The laser emitted by the second laser nozzle is perpendicular to the axis of the cylinder.

[0014] Furthermore, the CO2 injection nozzle has a long, cross-shaped structure; the spray range of the CO2 injection nozzle covers both the first and second laser nozzles.

[0015] Furthermore, the front end of the cylinder is provided with an end head, which is a hemispherical structure, and the gas pressure sensor is integrated inside the end head; the rear end of the cylinder is provided with a threaded part, through which the cylinder is connected to the gas injection pipeline; the gas injection pipeline is connected to the CO2 injection nozzle.

[0016] Furthermore, sliding shoes are provided along the front and rear circumferential edges of the outer wall of the cylinder, which are used to slide in contact with the inner wall of the horizontal well.

[0017] Furthermore, corrosion-resistant sleeves are wrapped around the first and second laser nozzles.

[0018] A method for dynamically adaptively controlling fracture network expansion in deep coal seams, employing the aforementioned expansion device, includes the following steps:

[0019] Step 1: Drill a vertical shaft from the surface into the deep, unminable coal seam, and then continue drilling a horizontal shaft along the direction of the deep, unminable coal seam, slowly pushing the capacity enhancement device along the shaft wall to the predetermined position at the far end of the horizontal shaft.

[0020] Step 2: Based on the preset parameters, adjust the laser power and the initial angle of the first laser nozzle so that the first laser nozzle and the second laser nozzle form cross irradiation, and start in-situ heating and modification of the target coal seam;

[0021] Step 3: The gas pressure sensor monitors the CO2 concentration and pressure changes in the horizontal well in real time, enabling adaptive adjustment of the first laser nozzle angle: When the detected CO2 pressure is less than the limit range, the elastic support angle α between the support plate and the outer wall of the cylinder is reduced, and the laser forms a cross-fracture network at the far end of the target coal seam, expanding the reservoir space; when the detected CO2 pressure is greater than the limit range, the elastic support angle α is increased, preferentially constructing a near-end fracture network in the near-horizontal well area; as CO2 is continuously injected and the pressure gradually decreases, the elastic support angle α is gradually reduced, pushing the fracture network to extend further; during laser heating, CO2 gas is continuously injected through the CO2 injection nozzle.

[0022] Furthermore, in the initial stage, CO2 is injected through the CO2 injection nozzle in a constant flow mode to remove air from the horizontal well and form an initial gas drive environment; then step three is implemented.

[0023] Furthermore, after step three, the drive capacity enhancement device moves at a constant speed along the horizontal well from far to near, while laser heating and CO2 injection continue during the movement.

[0024] Furthermore, when the capacity expansion device moves to the turning point between the vertical and horizontal wells, it stops moving, stops laser emission, and maintains CO2 injection until the sealing cement grouting is completed.

[0025] The beneficial effects of this invention compared to the prior art are as follows:

[0026] 1. Significantly improved reservoir stimulation efficiency: Through the synergistic effect of in-situ modification by laser heating and synchronous CO2 injection, combined with a dynamic adjustment system for the laser nozzle angle driven by CO2 concentration feedback, a cross-fracture network covering both the near and far ends can be adaptively constructed for coal seams with different densities, greatly improving the porosity and permeability of the coal seam and solving the problem of deep, unminable coal seam reservoir stimulation.

[0027] 2. Dual optimization of storage capacity and efficiency: The high-density construction of the fracture network expands the contact area between the coal body and CO2. Combined with the uniform injection design of the "+" shaped nozzle, it accelerates CO2 adsorption and diffusion, significantly improving storage efficiency. At the same time, by extending the fracture network to the far end, it effectively expands the reservoir storage space and increases the CO2 storage capacity per unit coal seam.

[0028] 3. Enhanced operational safety and stability: The gas shield formed by CO2 injection can prevent coal fragments from collapsing and blocking the laser nozzle, avoiding blockage of the injection channel; the slipper can reduce damage caused by friction between the device and the well wall, the corrosion-resistant sleeve protects the laser nozzle, and the leak-proof sealing structure prevents CO2 leakage, ensuring continuous and stable operation in all aspects; at the same time, the CO2 pressurization effect alleviates the risk of collapse caused by coal seam expansion and depressurization, reducing the incidence of disasters and accidents.

[0029] 4. Excellent adaptability and practicality: The device can adaptively adjust its operating parameters according to changes in coal seam density, porosity and CO2 pressure, making it suitable for deep, unminable coal seams with different characteristics; the core components are made of corrosion-resistant and wear-resistant materials, and the wellhead and sealing system are designed with targeted anti-corrosion features, extending the service life of the device and reducing operation and maintenance costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the location of the capacity expansion device within the horizontal well;

[0031] Figure 2 A schematic diagram illustrating the formation of an intersecting fracture network;

[0032] Figure 3 This is a schematic diagram of the dynamic control process of the cross-slit network;

[0033] Figure 4 This is a schematic diagram illustrating the change in the angle of the elastic support.

[0034] Figure 5 This is a schematic diagram of the capacity expansion device;

[0035] Figure 6 This is the front view of the capacity expansion device;

[0036] Figure 7 for Figure 6 AA section diagram;

[0037] Figure 8 This is a cross-sectional view of the capacity expansion device;

[0038] Figure 9 This is a cross-sectional view of the shoes / boots.

[0039] Explanation of icon numbers:

[0040] 1 is a CO2 pressurization and injection device; 2 is a cable winding wheel; 3 is a laser emitting device; 4 is a sealing sleeve; 5 is a capacity-enhancing device; 6 is a near-surface rock layer; 7 is an aquifer; 8 is a dense rock layer; 9 is a deep coal seam overburden; 10 is a deep, unminable coal seam; 11 is a deep coal seam underburden; 12 is a cross-fracture network formation zone; 13 is a gas injection pipeline.

[0041] 501 is the end head, 502 is the slip shoe, 503 is the adjustable angle support device, 504 is the second laser nozzle, 505 is the cylinder, 506 is the first laser nozzle, and 507 is the CO2 injection nozzle. Detailed Implementation

[0042] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto. Example 1

[0043] See Figure 1 , Figure 2 , Figures 4 to 9 This embodiment proposes a dynamic adaptive control fracture network expansion device for deep coal seams. The expansion device 5 includes a cylindrical body 505. The front end of the body 505 is provided with an end head 501, which has a hemispherical structure. The end head 501 facilitates the movement of the body 505 in a horizontal well. The rear end of the body 505 is provided with a threaded part, which connects the body 505 to a gas injection pipeline 13. The gas injection pipeline 13 allows the body 505 to be lowered along the wellbore to the target area.

[0044] Adjustable angle support devices 503 are provided on both sides of the outer wall of the cylinder 505. The adjustable angle support device 503 consists of multiple elastic support plates circumferentially hinged to the outer wall of the cylinder 505. The multiple support plates are connected to the drive mechanism. The extension and retraction of the drive mechanism drives the support plates to rotate around the hinge point. In this embodiment, the drive mechanism is a hydraulic cylinder. Multiple first laser nozzles 506 are evenly installed on the support plates. The angle at which the first laser nozzles 506 emit lasers can be adjusted by the rotation angle of the support plates. The elastic support angle α between the support plates and the outer wall of the cylinder 505 is in the range of 0°~90°.

[0045] Multiple rows of cross-shaped CO2 injection nozzles 507 are evenly arranged along the length of the outer wall of the cylinder 505. A second laser nozzle 504 is arranged between two adjacent rows of CO2 injection nozzles 507. The laser emitted by the second laser nozzle 504 is perpendicular to the axis of the cylinder 505. The CO2 injection nozzles 507 and the second laser nozzle 504 are located between the first laser nozzles 506 on both sides. The first laser nozzles 506 and the second laser nozzles 504 can form a laser interlacing network within a certain range, which can enhance the laser impact on a specific area. The CO2 injection nozzles 507 are generally elongated structures, and the nozzle spray range can cover the first laser nozzles 506 and the second laser nozzles 504. This can achieve uniform CO2 spray while forming a gas protective barrier covering the laser nozzles, preventing coal fragments from collapsing and blocking the laser nozzles.

[0046] A gas pressure sensor is integrated inside the end 501. The gas pressure sensor is connected to the hydraulic cylinder built into the cylinder 505. The gas pressure sensor is used to detect the CO2 concentration and pressure changes in the horizontal well in real time, and convert the detection signal into a control command to drive the hydraulic cylinder to extend and retract, thereby adjusting the support angle of the support plate and realizing the dynamic adjustment of the emission direction of the first laser nozzle 506.

[0047] To facilitate the movement of the cylinder 505 within the horizontal well, sliding shoes 502 are provided along the front and rear circumferential directions of the outer wall of the cylinder 505. The sliding shoes 502 slide in contact with the inner wall of the horizontal well, reducing the jamming of the cylinder 505 during movement.

[0048] To better adapt to the downhole environment, the first laser nozzle 506 and the second laser nozzle 504 are wrapped with corrosion-resistant sleeves.

[0049] A CO2 pressurization and injection device 1, a cable winding reel 2, and a laser emitting device 3 are installed on the ground. From the ground downwards, the internal structure consists of a near-surface rock layer 6, an aquifer 7, a dense rock layer 8, a deep coal seam overburden 9, a deep unminable coal seam 10, and a deep coal seam underburden 11. A well is drilled along the ground towards the deep unminable coal seam 10 and continues drilling into a horizontal well along the deep unminable coal seam 10. The CO2 pressurization and injection device 1 is connected to a capacity-enhancing device 5 through a gas injection pipeline 13, and the capacity-enhancing device 5 is lowered into the horizontal well through the gas injection pipeline 13. The cable winding reel 2 winds up a cable, which is set along the gas injection pipeline 13 and bundled together with the gas injection pipeline 13. One end of the cable is connected to the laser emitting device 3, and the other end of the cable is connected to several first laser nozzles 506 and second laser nozzles 504. The gas injection pipeline 13 is connected to the CO2 injection nozzle 507.

[0050] A sealing sleeve 4 is installed between the wellbore and the gas injection pipeline 13 to prevent gas leakage.

[0051] The working principle of the capacity expansion device 5 is as follows: based on the signal of the gas pressure sensor, the support angle of the adjustable angle support device 503 is adjusted in real time, so that the first laser nozzle 506 and the second laser nozzle 504 of the fixed structure perpendicular to the cylinder 505 emit lasers to form the cross-crack network forming zone 12.

[0052] Specifically, considering the characteristics of the target coal seam density and fracture development, a constant flow CO2 injection mode is adopted in the initial stage. When the CO2 pressure is detected to be too high (diffusion is hindered), the hydraulic cylinder moves backward to increase the elastic support angle α, so that the lasers emitted by the first laser nozzle 506 and the second laser nozzle 504 intersect in the near-horizontal well region, preferentially constructing a near-end fracture network. When the CO2 pressure is low (diffusion is faster), the hydraulic cylinder moves forward to decrease the elastic support angle α, and the lasers intersect at the far end away from the horizontal well. The elastic support angle α is adjusted in real time according to the pressure sensor signal to promote the formation of the fracture network. Example 2

[0053] See Figures 1 to 3 This embodiment proposes a method for dynamically adaptively controlling fracture network expansion in deep coal seams, employing the expansion device 5 described in Embodiment 1, and including the following steps:

[0054] Step 1: Using a combination of 3D seismic exploration, comparison of adjacent well logging data, and core sampling experiments, comprehensively obtain core parameters of the coal seam in the target area, such as thickness, depth, density, porosity, and the degree of development of primary pores and fractures. Simultaneously, identify geological risk points such as faults and fracture zones. A comprehensive assessment of the caprock's sealing capacity, geological stability, and environmental protection requirements is conducted to delineate the sealing target area—prioritizing areas without faults, with continuous and intact caprocks, uniform coal seam thickness (≥3m), and far from surface water source protection areas. The boundary coordinates and extent of the target area are then clearly defined.

[0055] Step Two: Vertical Shaft Construction: Drill from the surface to the center of the upper and lower overburden layers of the deep, unminable coal seam 10 (depth 800-1000m), and complete the casing cementing in stages. Specifically, this includes:

[0056] Drilling begins: Drill to the bottom boundary of the near-surface rock layer 6 (depth 50-80m), run in the surface casing, inject cement into the annular space to seal the shallow aquifer and prevent contamination.

[0057] Second-stage drilling: Drill to 50m above the roof of the deep, unminable coal seam 10, run in casing and cement well to seal the upper strata of the deep, unminable coal seam 10 and build an independent operating passage.

[0058] Three-stage drilling: Drill to the middle of the deep, unminable coal seam 10, using foam drilling fluid as the circulating medium (to avoid contaminating the coal seam), and do not perform conventional cementing after well completion, reserving a connection channel for horizontal wells.

[0059] Step 3, Horizontal Well Construction: Using directional drilling technology, a horizontal well is constructed by drilling from the bottom of the vertical well along the strike of the deep, unminable coal seam 10. The wellbore trajectory is adjusted in real time through the measurement while drilling system to ensure that the axis of the horizontal well is located in the center of the coal seam thickness and runs through the entire sealing target area. The length of the horizontal section is set according to the target area range (usually 500-1000m).

[0060] Step 4: Slowly push the capacity expansion device 5 along the well wall to the predetermined position at the far end of the horizontal well (500-1000m horizontal distance from the vertical well), ensuring that the slipper 502 fits well with the well wall and that the first laser nozzle 506, the second laser nozzle 504, and the CO2 injection nozzle 507 are unobstructed.

[0061] Step 5: Connect the capacity expansion device 5 to the laser emitting device 3 and the CO2 pressurization and injection device 1. Ensure that the cable and gas injection pipeline 13 are precisely connected to the leak-proof sealing sleeve 4 and tighten the fasteners to ensure a reliable seal.

[0062] Step 6: Debug the device operation status: Start the gas pressure sensor and verify the signal transmission stability; test the angle adjustment function of the first laser nozzle 506 to ensure smooth linkage between the support plate and the hydraulic cylinder; test run the CO2 pressurization injection device 1 and check the uniformity and airtightness of the CO2 injection nozzle 507.

[0063] Step 7: Simultaneously start the laser emitting device 3 and the CO2 pressurized injection device 1. In the initial stage, CO2 is injected in a constant flow mode to remove air from the well and form an initial gas drive environment. Based on the preset parameters, adjust the laser power and the initial angle of the first laser nozzle 506 so that the first laser nozzle 506 and the vertically fixed second laser nozzle 504 form cross irradiation, and begin in-situ heating and modification of the target coal seam.

[0064] Step 8: The gas pressure sensor inside end cap 501 monitors the CO2 concentration and pressure changes in the horizontal well in real time and dynamically feeds back to the control system to achieve adaptive adjustment of the angle of the first laser nozzle 506: When the detected CO2 pressure is low (≤3MPa, corresponding to a loose coal seam with well-developed pores and fractures), the hydraulic cylinder moves forward, reducing the elastic support angle α, and the laser forms a cross-fracture network at the far end of the target coal seam, expanding the reservoir space. When the detected CO2 pressure is high (≥5MPa, corresponding to a dense coal seam), the hydraulic cylinder moves backward, increasing the elastic support angle α, preferentially constructing a near-horizontal fracture network in the near-horizontal well region; as CO2 is continuously injected and the pressure gradually decreases, the elastic support angle α is gradually reduced, pushing the fracture network to extend further.

[0065] Step 9: Rotate the cable reel 2 to drive the capacity expansion device 5 to move at a constant speed (0.5-2 m / h) along the horizontal well from far to near. During the movement, laser heating and CO2 injection continue: CO2 injection nozzle 507 continuously sprays, forming an air curtain protective cover to prevent coal fragments from collapsing and obstructing the laser nozzle. The slipper 502 reduces frictional wear between the device and the well wall, ensuring stability during movement; the corrosion-resistant sleeve outside the laser nozzle isolates it from CO2 corrosion, extending the equipment's service life.

[0066] Step 10: When the capacity expansion device 5 moves to the turning point between the vertical and horizontal wells, stop moving, turn off the laser emitting device 3 first, and maintain the CO2 injection state (pressure 3-4MPa) until the sealing cement grouting is completed.

[0067] Step 11: Inject high-strength, corrosion-resistant grouting material into the vertical shaft in sections, sealing the entire shaft from the bottom to the caprock to ensure complete sealing of the storage area. Monitor the cement grout level and solidification state during the grouting process. After the cement has fully set (usually cured for 72 hours), increase the CO2 injection pressure through the wellhead device (not exceeding the caprock fracture pressure, typically 8-10 MPa) to promote CO2 penetration into the deep fracture network, increase the coal body adsorption saturation, and maximize CO2 storage.

[0068] This invention provides an efficient injection and expansion method for CO2 sequestration in deep, unminable coal seams. The specially designed expansion device 5 can automatically adjust the laser emission angle according to different coal seam characteristics, forming a more extensive fracture network, thereby increasing the CO2 sequestration capacity.

[0069] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0070] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this invention.

Claims

1. A deep coal seam dynamic self-adaptive regulation and control fracture network capacity-increasing device, characterized in that, The capacity expansion device (5) includes a cylinder (505) and a gas pressure sensor; adjustable angle support devices (503) are provided on both sides of the outer wall of the cylinder (505). The adjustable angle support devices (503) are multiple support plates circumferentially hinged to the outer wall of the cylinder (505). The multiple support plates are connected to the drive mechanism, which drives the support plates to rotate around the hinge point; multiple first laser nozzles (506) are installed on the support plates; a CO2 injection nozzle (507) and a second laser nozzle (504) are arranged on the outer wall of the cylinder (505). The CO2 injection nozzle (507) and the second laser nozzle (504) are located between the first laser nozzles (506) on both sides; a laser interlacing network is formed by the first laser nozzles (506) and the second laser nozzles (504); the gas pressure sensor is connected to the drive mechanism; the gas pressure sensor is used to detect the CO2 concentration and pressure changes in the horizontal well in real time, and then adjust the laser emission angle of the first laser nozzle (506).

2. The device according to claim 1, wherein, Multiple rows of CO2 injection nozzles (507) are evenly arranged along the length of the outer wall of the cylinder (505). A second laser nozzle (504) is arranged between two adjacent rows of CO2 injection nozzles (507). The laser emitted by the second laser nozzle (504) is perpendicular to the axis of the cylinder (505).

3. The device according to claim 2, wherein, The CO2 injection nozzle (507) has a long strip-shaped "+" structure; the nozzle spray range of the CO2 injection nozzle (507) covers the first laser nozzle (506) and the second laser nozzle (504).

4. The device according to claim 1, wherein, The front end of the cylinder (505) is provided with an end head (501), which is a hemispherical structure, and the gas pressure sensor is integrated inside the end head (501); the rear end of the cylinder (505) is provided with a threaded part, through which the cylinder (505) is connected to the gas injection pipeline (13); the gas injection pipeline (13) is connected to the CO2 injection nozzle (507).

5. The device according to claim 1, wherein, Slippers (502) are provided along the front and rear circumferential sides of the outer wall of the cylinder (505). The slippers (502) are used to slide in contact with the inner wall of the horizontal well.

6. The deep coal seam dynamic adaptive control fracture network expansion device according to claim 1, characterized in that, The first laser nozzle (506) and the second laser nozzle (504) are wrapped with corrosion-resistant sleeves.

7. A method for dynamically adaptively controlling fracture network expansion in deep coal seams, characterized in that, The capacity expansion device (5) as described in any one of claims 1-6 is employed, and includes the following steps: Step 1: Drill a vertical shaft from the ground into the deep, unminable coal seam (10), and then continue along the deep, unminable coal seam (10) to construct a horizontal shaft. Slowly push the capacity-enhancing device (5) along the shaft wall to the predetermined position at the far end of the horizontal shaft. Step 2: Based on the preset parameters, adjust the laser power and the initial angle of the first laser nozzle (506) so that the first laser nozzle (506) and the second laser nozzle (504) form cross irradiation, and start in-situ heating and modification of the target coal seam; Step 3: The gas pressure sensor monitors the CO2 concentration and pressure changes in the horizontal well in real time to achieve adaptive adjustment of the angle of the first laser nozzle (506): When the CO2 pressure is detected to be less than the limit range, the elastic support angle α between the support plate and the outer wall of the cylinder (505) is reduced, and the laser forms a cross fracture network at the far end of the target coal seam to expand the reservoir space; when the CO2 pressure is detected to be greater than the limit range, the elastic support angle α is increased, and a near-end fracture network is preferentially constructed in the near-horizontal well area; as CO2 is continuously injected and the pressure gradually decreases, the elastic support angle α is gradually reduced to promote the fracture network to extend to the far end; during the laser heating process, CO2 gas is continuously injected through the CO2 injection nozzle (507).

8. The method according to claim 7, wherein, In the initial stage, CO2 is injected through the CO2 injection nozzle (507) in a constant flow mode to remove air from the horizontal well and form an initial gas drive environment. Then proceed to step three.

9. The method according to claim 7, wherein, After step three, the drive capacity expansion device (5) moves at a constant speed from far to near along the horizontal well, while laser heating and CO2 injection continue during the movement.

10. The method according to claim 9, wherein, When the capacity expansion device (5) moves to the turning point between the vertical and horizontal wells, it stops moving, stops laser emission, and maintains CO2 injection until the sealing cement grouting is completed.

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