Coal mine area well-ground combined rock burst-gas composite disaster treatment method

Abstract

This invention discloses a method for managing the combined rockburst and gas disaster in coal mines, comprising: Step 1, determining the trajectory and location of a long directional borehole in the coal mine; Step 2, implementing the long directional borehole in the coal mine and the surface directional well; Step 3, connecting and pressure-bearing the combined well-surface fracturing pipeline; Step 4, using a single-seal retraction dragged perforation fracturing tool string for segmented perforation fracturing with sandblasting, or using a double-seal retraction dragged perforation fracturing tool string for segmented perforation fracturing within the open hole of the long directional borehole; Step 5, using a double-seal retraction dragged perforation fracturing tool string for casing-reinforced perforation within the entire open hole of the long directional borehole, or installing screen pipes within the open hole of the long directional borehole. This invention effectively manages the risk of rockburst disasters while ensuring that the fracturing fractures are tangent to or coincide with the fracture zone formed after coal seam mining, achieving gas control through mining-induced pressure relief, and realizing the coordinated management of rockburst and gas disasters through a single borehole along the coal seam roof.

Description

Technical Field

[0001] This invention belongs to the field of coal mine area rockburst-gas composite disaster control engineering, and relates to a method for controlling coal mine area rockburst-gas composite disasters in conjunction with mine-ground joint control. Background Technology

[0002] Rockbursts and gas hazards are two serious threats to safe production in mines. Different mining areas may experience one or both of these hazards before coal seam mining begins. The management of mines with both rockbursts and gas hazards is particularly complex. The overall management methods can be categorized into two main types: underground management and surface management. For mines with combined rockburst and gas hazards, one or a combination of these two methods is typically used to achieve the management objective. Surface management: Its advantages lie in the larger surface operating space, lower safety risks, and the ability to conduct large-scale regional management, effectively reducing the number of boreholes in the coal face or roof. However, this method is easily limited by surface terrain; for example, suitable locations for surface well locations include high mountains and ecological protection zones, making this method unsuitable for normal application. Coal mine underground treatment mode: Its main advantage is that it is not affected by factors such as surface topography, and the layout of holes underground is relatively flexible; however, this mode is limited by the small underground working space and the high risk of safety hazards, making it difficult to implement large-scale treatment, and it is necessary to appropriately increase the number of holes in the coal mining face or roof. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for controlling combined rockburst and gas disasters in coal mines, thereby solving the problems that the above-mentioned surface control methods are easily limited by the terrain and cannot be applied normally, and that the underground control methods in coal mines are constrained by the small underground working space, have greater safety risks, and are difficult to implement on a large scale.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A combined mine-ground approach to managing rockburst-gas complex disasters in coal mining areas includes the following steps: Step 1: Determine the three-dimensional spatial position of the directional long borehole trajectory in the coal mine; The location of the hard key layer and the fracture zone of the overlying strata of the coal seam are determined by calculation, and the vertical position of the directional long borehole trajectory in the coal mine is determined; and the position of the directional long borehole trajectory in the coal mine is determined on the horizontal projection surface. Step 2: Based on the location of the underground directional long borehole determined in Step 1, implement the underground directional long borehole with a two-section borehole structure, and at the same time implement the surface through directional well with a two-section well structure. Among them, the first opening structure of the directional long borehole in the coal mine is to be cemented with casing, and the second opening structure is to implement one of the following two structures: Second opening structure I is to be ... Step 3: Connection and pressure test of the well-to-surface fracturing pipeline; A high-pressure resistant hose is used to connect the surface-through directional well fracturing pipeline to the underground fracturing pipe in the coal mine; the pressure-bearing sealing connection effect between the surface-through directional well fracturing pipeline, the underground fracturing pipe, and the high-pressure resistant hose is verified by pressure test. Step 4: Use a single-seal retractable drag perforation fracturing tool string to perform sandblasting perforation segmented fracturing and use it as fracturing method I for the two-section structure I in step 2; or use a double-seal retractable drag perforation fracturing tool string to perform perforation segmented fracturing in the open hole of a directional long borehole and use it as fracturing method II for the two-section structure II in step 2. Step 5: If step 4 uses fracturing method I, then a double-sealed, retractable drag perforation fracturing tool string is used to perform directional long drilling with casing reinforcement perforation throughout the entire hole; if step 4 uses fracturing method II, then a screen pipe is installed in the open hole of the directional long drilling.

[0005] The present invention also includes the following technical features: Specifically, in step 1, calculating and determining the location of the hard, critical layer of the overlying strata of the coal seam includes: Step a1, Analysis of Hard Key Layers Based on Overburden Structure Characteristics: Using the comprehensive geological columnar section of the coal seam roof overburden, based on the thickness and lithology discrimination method of the rock strata as key layers, the thick and hard rock strata that may become hard key layers are initially identified as the basic hard key layers; through the hard key layer stiffness condition discriminant formula, it is determined whether the basic hard key layer meets the stiffness condition. If it does, the rock strata is a hard key layer, and this is extrapolated to the last hard rock layer. Step a2, based on the analysis of the main induced impact hard key layers: the overburden strata of the coal seam fracture in sequence and release energy. This energy decays exponentially in the rock mass. By calculating the amount of energy released and transferred to the coal body after decay, the hard rock strata that pose an impact risk to the working face are identified, and the hard key layers are determined. Step a3: Based on the two types of hard key layers determined in steps a1 and a2, select the rock strata within the height range of the intersection of the two as the hard key layers to be fracturing.

[0006] Specifically, in step 1, the location of the fracture zone in the overlying strata of the coal seam is: H K ~H K +H L , where H K H represents the thickness of the caving zone in the overlying strata. LThis represents the thickness of the fracture zone in the overlying strata.

[0007] Specifically, in step 1, based on the location of the hard key layer and the location of the fracture zone in the overlying strata of the coal seam, when the hard key layer is located above or below the fracture zone, under given fracturing parameters, the upward and downward fracture propagation height along the vertical position of the directional long borehole must meet the following requirements: the fracturing fracture propagates to the hard key layer to half the thickness of the hard rock layer, and the fracturing fracture propagates to the fracture zone to at least the outer edge of the fracture zone boundary.

[0008] Specifically, in step 1, determining the position of the directional long borehole trajectory on the horizontal projection plane in the coal mine includes: The trajectory of a long directional borehole in a coal mine is located on one side of the return airway of the coal seam working face. The formula for calculating the distance between the location of the long directional borehole on the horizontal projection plane and the return airway is as follows:

[0009] In the formula, The distance from the location of the long directional borehole in the coal mine to the return airway on the horizontal projection plane is expressed in meters. Let the thickness of the caving zone be m; B is the thickness of the fracture zone, in meters; B is the distance from the outer boundary of the directional long borehole in the coal mine to the O-ring, in meters. The dip angle of the coal seam is °; The angle between the line connecting the outer boundary of the O-shaped ring and the mining boundary and the coal seam.

[0010] Specifically, in step 2, the trajectory of the directional long borehole drilling process is controlled within the range of 1~1.5° in the downdip direction; the first section of the directional long borehole is drilled at least 10m; in the second section I, a centralizer is installed on the outside of the casing every three casings to ensure that the casing is centered; the entire section of the surface-penetrating directional well is cemented with casing.

[0011] Specifically, in step 3, the fracturing pipeline in the surface-penetrating directional well is made of tubing, and the tubing is connected by threads to achieve pressure-bearing sealing; the fracturing pipes in the mine are connected by oil hoses to achieve pressure-bearing sealing; the fracturing pipeline in the surface-penetrating directional well, the fracturing pipes in the mine, and the high-pressure resistant hose have the same inner diameter after being connected, and the joint is flat inside. Step 3, the pressure test includes: on the surface, multiple fracturing pump trucks are connected in parallel to the main pipeline at the wellhead and connected to the oil pipe in the directional well. Then, the fracturing pipeline at the end of the long directional borehole in the coal mine is sealed with a high-pressure resistant valve. Finally, on the surface, multiple fracturing pump trucks pump clean water until the pressure on the main pipeline at the wellhead reaches 5MPa. The discharge rate is adjusted intermittently for 5 minutes to ensure that the pressure on the main pipeline at the wellhead reaches 50MPa and is stabilized for 30 minutes. If the pressure drop is less than 0.5MPa, the pressure test of the well-to-surface fracturing pipeline is qualified.

[0012] Specifically, in step 4, fracturing method I includes: connecting the tubing to the perforation fracturing tool string; using the drilling rig to lower the perforation fracturing tool string into the bottom of the directional long borehole; the pressure-bearing device at the borehole opening of the directional long borehole achieves borehole opening sealing; using a surface fracturing pump truck to inject high-pressure clean water to separate the packer connected to the front section of the perforation fracturing tool string, achieving bottom sealing of the directional long borehole; using the drilling rig to drag the tubing backward to the designed borehole depth position; the surface fracturing pump truck injects high-pressure sand-carrying clean water, which, under the action of the pressure difference inside and outside the tool string, sprays the casing; when the pressure on the main pipeline at the wellhead on the surface suddenly decreases and then rises again, the casing is perforated to form a perforation hole; adjusting the injected clean water fracturing discharge rate and sand content as the initial fracturing design parameters; after the designed fracturing volume is injected, the injection is stopped, the pressure is released and the perforation fracturing tool string in the hole is removed, and this fracturing section is completed. This process is repeated until all designed fracturing sections are completed.

[0013] Specifically, in step 4, fracturing method II includes: connecting the perforation fracturing tool string to the tubing; using a coal mine drilling rig to lower the perforation fracturing tool string into the designed fracturing section position within the directional long borehole; the pressure-bearing device at the borehole opening of the directional long borehole achieves borehole sealing; the surface fracturing pump truck begins injecting high-pressure clean water to inflate the expansion packers connected to the front and rear ends of the perforation fracturing tool string; the inflated packers are pressure-bearing and sealingly fitted against the open hole wall of the directional long borehole, achieving full fracturing within the directional long borehole within the section length between the front and rear expansion packers. In a sealed state, the surface fracturing pump truck injects high-pressure, sand-carrying water, which, under the pressure difference between the inside and outside of the tool string, is sprayed onto the wall of the directional long borehole. When the pressure on the main pipeline at the wellhead suddenly decreases and then rises again, the open hole wall is perforated to form a perforation hole. The injection water fracturing flow rate and sand content are adjusted to the initial fracturing design parameters. After the designed fracturing volume of the current fracturing section is injected, the injection is stopped, the pressure is released, and the perforation fracturing tool string is dragged to the next adjacent designed fracturing section until all designed fracturing sections are completed.

[0014] Specifically, in step 5, the use of a double-sealed, retractable drag-type perforation fracturing tool string to implement casing-enhanced perforation throughout the directional long borehole includes: Use the coal mine drilling rig, drill rod and drill bit to remove the packer set in the casing. The packer located at the bottom of the directional long borehole is retained. The residual packer debris in the casing is flushed out. The tubing connects to the perforation fracturing tool string. The drilling rig lowers the perforation fracturing tool string into the designed position within the directional long borehole via the tubing. The pressure-bearing device at the borehole opening ensures a seal. A surface fracturing pump truck then injects high-pressure water to seal the expansion packers connected to the front and rear ends of the perforation fracturing tool string. The section between the front and rear expansion packers avoids the perforation hole formed in step 4. At this point, the entire directional long borehole within the section between the front and rear expansion packers is sealed. The surface fracturing pump truck injects high-pressure, sand-carrying water that flows through the tool string under the pressure difference, jetting the casing. When the pressure on the main wellhead pipeline at the surface experiences a sudden drop followed by a rise, the casing perforates, forming a densified perforation. Injection stops, and the process continues to the next designed densified perforation section, completing all designed densified perforation sections. The strength of the casing after perforation must be greater than the vertical stress of the overlying strata.

[0015] Specifically, step 5, which involves inserting a screen tube into the open hole during directional long drilling, includes: Using a coal mine drilling rig, a drill bit of the same size as the final hole was lowered into the directional long borehole and drilled to the bottom of the hole to finish the entire hole. At the same time, the drilling time at different hole depths was recorded when the drill bit finished the hole. The residual rock cuttings in the open hole of the directional long borehole were washed clean. The screen pipe and casing are connected by threaded connections using a coal mine drilling rig and sent to the bottom of the directional long borehole. Based on the recorded drilling time, the screen pipes in the long drilling sections are either small-aperture density screen pipes or unperforated casings that match the screen pipe size. In the short drilling sections or where the drill bit is directly lowered through the borehole depth, normally designed large-aperture density screen pipes are used. When the screen pipe is lowered to the section overlapping with the first-stage casing, an unperforated second-stage casing is used, with this section extending 0.5~1m beyond the borehole opening. A threaded sealing short section is used to seal the first-stage and second-stage casings at the borehole opening. The portion of the second-stage casing extending beyond the borehole opening is used to connect to the gas extraction pipeline. The screen pipes lowered into the directional long borehole have an external extrusion resistance greater than the vertical stress of the overlying strata at the corresponding formation depth of the directional long borehole.

[0016] Compared with the prior art, the present invention has the following technical effects: This invention employs a drag-and-drop segmented fracturing process using a moving tubing string. By dragging the tubing string, segmented fracturing can be achieved, eliminating the need for multiple tubing string trips, reducing construction time and difficulty, and improving construction efficiency. This technology can reduce the number of boreholes and repetitive construction cycles. High-pressure water is applied to the coal and rock mass, weakening the hard roof and top coal, causing the roof to collapse as mining progresses, effectively transferring the stress field of the surrounding rock. Simultaneously, the coal body undergoes internal displacement and structural damage under the action of high-pressure water, reducing its elasticity, increasing its plasticity, and reducing the accumulation of elastic deformation energy, fundamentally reducing the possibility of rockbursts and creating a favorable stress environment for gas migration and extraction. The optimally designed location of long directional boreholes in coal mines not only ensures that the fracturing fractures extend to at least half the thickness of the key layer in the hard roof, effectively mitigating the risk of rockburst disasters, but also ensures that the fracturing fractures are tangential or coincident with the fracture zone formed after coal seam mining, effectively achieving mining-driven decompression and gas control. By integrating gas extraction and anti-impact pressure relief functions into a single borehole through the "multi-purpose long borehole" technology, the waste of resources and operational interference caused by independent construction of multiple types of boreholes can be avoided.

[0017] This invention utilizes a second-stage retraction fracturing technique primarily for re-perforating the casing. A dual-sealed, retraction-type drag-type fracturing perforation tool string is employed to achieve this re-perforation. The dragging of the tubing string allows for segmented, continuous re-perforation without the need for multiple tripping operations, reducing construction time and difficulty and improving efficiency. Simultaneously, two expandable packers isolate the perforated sections from the existing fracturing and re-perforation holes on the casing, effectively ensuring a seal between the expanded sections of the two packers. This prevents injected fracturing fluid from flowing into the existing fracturing and re-perforation holes, thus affecting the re-perforation effect. Furthermore, the pressure changes on the surface fracturing wellhead manifold effectively determine the success of the re-perforation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the vertical position of a long directional borehole located above a fracture zone in a hard, critical layer.

[0019] Figure 2 This is a schematic diagram showing the vertical position of a long borehole oriented to coincide with a hard, critical layer and a fracture zone.

[0020] Figure 3 This is a schematic diagram showing the vertical position of a long directional borehole located below a fracture zone in a hard, critical layer.

[0021] Figure 4 This is a schematic diagram of the position on the horizontal projection profile of a directional long borehole.

[0022] Figure 5 A schematic diagram of the inclination angle design for a directional long borehole trajectory.

[0023] Figure 6This is a schematic diagram of a combined well-to-surface single-seal retractable dragged perforation fracturing tool string for segmented sandblasting and perforation fracturing.

[0024] Figure 7 This is a partial schematic diagram of a single-seal, retractable, drag-type perforation fracturing tool string for segmented fracturing via sandblasting and perforation.

[0025] Figure 8 This is a schematic diagram of a well-to-surface combined dual-sealed retractable dragged perforation fracturing tool string for sandblasting and densification.

[0026] Figure 9 This is a partial schematic diagram of a double-sealed, retractable, drag-type perforation fracturing tool string with sandblasting and densification.

[0027] Figure 10 This is a schematic diagram of a well-to-surface combined dual-sealed retractable dragged perforation fracturing tool string for segmented sandblasting and perforation fracturing.

[0028] Figure 11 This is a schematic diagram of the screen pipe being lowered after segmental fracturing of a long directional borehole in a coal mine. Detailed Implementation

[0029] The method for controlling combined rockburst and gas disasters in coal mines provided by this invention includes two implementation methods: Method 1: First, drill a directional breakthrough well on the surface to connect with the given underground roadway. Simultaneously, drill a long directional borehole underground along the determined coal seam roof strata. After the surface breakthrough well and underground borehole are completed, lower fracturing pipelines to the bottom of the shaft on the surface and connect the fracturing pipelines from the opening of the long directional borehole to the bottom of the breakthrough well underground. After the pressure test of the fracturing pipelines from the opening of the surface breakthrough well to the opening of the long directional borehole is successfully completed, use a high-pressure pump truck on the surface in conjunction with the underground drilling rig. A retractable single-seal dragged perforation fracturing tool string is used for segmented fracturing of directional long boreholes via sandblasting perforation. After all designed fracturing sections are completed within the directional long borehole, the single-seal perforation fracturing tool string is replaced with a double-seal perforation fracturing tool string. The perforation fracturing tool string is then re-inserted into the bottom of the directional long borehole using a coal mine drilling rig. Then, a high-pressure pump truck and the coal mine drilling rig work together to perform additional perforation work in the directional long borehole using the retractable double-seal dragged perforation fracturing tool string, without further fracturing. The fracturing holes formed during the segmented fracturing process are used for water-induced fracturing of the formation to control rockburst. The additional holes formed by the additional perforation work in conjunction with the fracturing holes to extract gas during coal seam mining. This method can efficiently achieve the coordinated control of rockburst and gas hazards through a single borehole along the coal seam roof.

[0030] Method Two: First, drill a directional breakthrough well on the surface to connect with a given underground roadway. Simultaneously, drill a long directional borehole underground along the determined coal seam roof stratum, without running casing into the final borehole. After the surface breakthrough well and underground borehole are completed, then lower fracturing pipelines from the surface to the bottom of the shaft, and connect and install fracturing pipelines from the opening of the long directional borehole to the bottom of the breakthrough well underground. The line installation and pressure test were successfully completed. On the surface, a high-pressure pump truck and a coal mine drilling rig were used in conjunction with a retractable double-sealed drag perforation fracturing tool string to perform segmented fracturing of the directional long borehole using sandblasting and perforation. All designed fracturing sections within the directional long borehole were completed. After the high-pressure relief of the segmented fracturing was completed, the coal mine drilling rig was used again to drill into the directional long borehole with a drill bit of the same final borehole size until the bottom of the hole was finished. Finally, a screen pipe was installed in the finished directional long borehole. The fracturing network formed in the formation during the segmented fracturing process not only fractures hard, critical layers, but also, in conjunction with the screen pipe installed in the well, extracts mining-induced depressurized gas during coal seam mining. This method can efficiently achieve the coordinated management of rockburst and gas disasters through a single borehole along the coal seam roof.

[0031] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0032] Example 1: This embodiment provides a method for managing combined rockburst and gas disasters in coal mine areas, such as... Figures 1 to 9 As shown, it includes: Step 1: Three-dimensional spatial layout of directional long borehole trajectory in coal mine. The three-dimensional spatial layout of directional borehole trajectory in coal mine mainly includes the vertical and horizontal projection planes. A reasonable directional long borehole trajectory must simultaneously ensure that the vertical fracture propagation height along the segmented hydraulic fracturing of the directional long borehole can extend to the height of the hard rock strata of the coal seam roof to achieve rockburst control, while the fracturing fractures can extend to the range of the overlying rock fracture zone formed after coal seam excavation.

[0033] Step 11: Determine the vertical position of the directional long borehole trajectory in the coal mine.

[0034] (a) To determine the location of the hard key layer in the overlying strata of the coal seam, two methods were adopted: hard key layer analysis based on overlying strata structure characteristics and hard key layer analysis based on major induced impacts. In this way, multiple factors were considered to determine the hard key layer for fracturing.

[0035] First, based on the analysis method of hard key layers with overburden structure characteristics: using the comprehensive columnar section of the geological structure of the overburden of the coal seam, based on the thickness of the rock layer that may be a key layer (thickness > 10m) and the lithology discrimination method, the thick hard rock layer that may become a key layer is initially determined as the basis for determining the location of the key layer; second, the stiffness condition formula of the key layer is used to further determine whether the aforementioned basic key layer meets the stiffness condition discrimination, the discrimination formula is as shown in discrimination formula (1), if it meets the condition, the rock layer may become a key layer, and this can be extrapolated to the last hard rock layer; finally, the strength condition formula of the key layer is used to determine whether the nth, n+1th, etc. layers are key layers, the discrimination formula (2) is that the fracture distance of the overlying hard rock layer is greater than the fracture distance of the lower hard rock layer.

[0036] (1) (2) In the formula: n is the number of hard rock layers; h i For the first i Thickness of the rock strata, in meters (m). γ i For the first i Unit weight of rock strata (kg / m³) 3 ; E i For the first i Elastic modulus of rock strata, GPa; l i For the first i The fracture distance of the rock strata, in meters; R Ti For the first i Tensile strength of rock strata, MPa; q i For the first i The load borne by the rock strata, kPa.

[0037] Secondly, based on the analysis method of the main induced impact hard key layer: the induced impact key layer is the rock layer in the overlying strata of the coal seam that plays a major role in the impact hazard of the coal seam. The induced impact key layer is determined from the energy perspective. The elastic energy in the coal seam consists of three parts: volumetric elastic energy, deformation elastic energy and roof bending elastic energy. Among them, the roof bending elastic energy is divided into the energy released during fracture under the two conditions of initial collapse and periodic collapse. The calculation formula is shown in formula (3).

[0038] (3) In the formula, E n1 The energy released during the initial fracture, J;E n2 φ is the energy released during periodic fracture, J; M is the bending moment of the roof strata above the coal face, N·m; φ is the angle of deflection of the roof strata, °. qI is the unit-length equivalent load of the top stratum mass and the additional load of the overlying stratum, in Pa; I is the moment of inertia of the top stratum cross section, in m. 4 I=bh 3 / 12, h is the thickness of the overburden stratum, m, b is the width, m, taken as 1; L is the overhang length of the overburden stratum, m; E is the elastic modulus, Pa.

[0039] Based on the energy value calculated by formula (3), the nth layer of the overburden rock in the coal seam fractures sequentially and releases energy, and the released energy is denoted as follows: E 1. E 2. ... E n-1 , E n The distance from the epicenter to the mined coal seam is r 1. r 2. ... r n-1 , r n This energy decays exponentially within the rock mass, with a decay exponent (damping) of η. The energy released and transferred to the coal mass after decay is E´. n The calculation formula is as follows (4): (4) The energy E' transferred to the coal body was obtained through calculation. n The relative size can be used to determine the hard rock layer that has a certain impact on the impact risk of the working face, and thus the hard key layer can be identified.

[0040] Finally, based on the hard rock layers identified by the two hard key layer analysis methods mentioned above, the rock layers within the height range of their intersection position are selected as the hard key layers to be fractured. Therefore, the target fracture layers under different factor conditions can be determined.

[0041] (b) Determine the location of the fracture zone in the overlying strata of the coal seam. Utilize the empirical calculation formulas for the thickness of the caving zone and fracture zone in the "upper three zones" of the overlying strata during coal seam mining, as shown in Table 1. Obtain the thickness H of the caving zone respectively. K m and the thickness of the fracture zone H L The location of the fracture zone in the overlying strata of the coal seam is: H. K ~H K +H L .

[0042] Table 1. Empirical formulas for calculating the thickness of the caving zone and fracture zone in the overlying strata of coal seam mining.

[0043] (c) Based on the above calculations, the locations of the hard key strata in the overlying strata of the coal seam and the locations of the fracture zones in the overlying strata for coal seam mining can be divided into three types: hard strata located above the fracture zones, hard strata coinciding with the fracture zones, and hard strata located below the fracture zones, such as... Figures 1 to 3 As shown. When the hard rock strata coincide with the fracture zone, the borehole trajectory is positioned at the midpoint of the vertical thickness of the hard key stratum. When the hard rock strata are located above or below the fracture zone, the vertical position of the directional long borehole must meet the following requirements under given fracturing parameters: the fracturing fracture must extend to half the thickness of the hard rock strata in the hard key stratum, and the fracturing fracture must extend to at least the outer edge of the fracture zone boundary.

[0044] Step 12: Determine the position of the directional long borehole trajectory on the horizontal projection plane in the coal mine. The designed directional long borehole trajectory is located on one side of the return airway of the coal seam working face, such as... Figure 4 As shown, this facilitates decompression gas extraction during coal seam mining. Based on the "O"-ring theory of decompression gas extraction, the layout of decompression gas extraction boreholes is designed and guided. Therefore, the formula for calculating the distance from the location of the long directional borehole in the coal mine underground to the return airway on the horizontal projection plane is as follows:

[0045] In the formula, The distance from the location of the long directional borehole in the coal mine to the return airway on the horizontal projection plane is expressed in meters. Let the thickness of the caving zone be m; B is the thickness of the fracture zone, in meters; B is the distance from the outer boundary of the "O"-shaped long borehole in the coal mine, in meters. The dip angle of the coal seam is °; The "O"-shaped zone is the angle between the line connecting the outer boundary of the "O"-shaped zone and the mining boundary, and the coal seam. The "O"-shaped zone refers to the transversely connected delamination zone within the overlying strata above the goaf, a typical distribution pattern of mining-induced fractures. The "O"-shaped zone is a gas-rich area, and gas can be extracted and depressurized through directional long boreholes, such as... Figure 4 .

[0046] Step 2: Based on the location of the underground directional long borehole determined in Step 1, implement the underground directional long borehole, and simultaneously construct a surface directional through-hole. The borehole opening is designed to be slightly higher than the bottom, and the drilling trajectory is controlled within a downward dip range of 1~1.5°. Figure 5As shown, ensuring the drilled directional long borehole trajectory is downward-sloping and smooth is crucial for the smooth installation of casing throughout the entire borehole and for achieving high-quality cementing. This also effectively facilitates the natural separation of depressurized gas and formation water during coal seam gas extraction, enabling efficient depressurized gas extraction. The implemented underground directional long borehole design is a two-section structure. The first section involves drilling at least 10 meters and installing high-quality casing for cementing. This must ensure sufficient pressure on the wellhead device during fracturing. The second section involves installing casing throughout the entire borehole. For every three casing sections, a centralizer must be installed on the outside of the casing to ensure it is centered. This ensures a seamless cementing process throughout the entire borehole of the underground directional long borehole, efficiently filling the gap between the second section casing and the borehole. The surface directional breakthrough well to be implemented must be designed with casing cementing throughout the entire well section, and a two-section wellbore structure can be designed.

[0047] Step 3: Connect the well-to-surface fracturing pipeline, such as... Figure 6 As shown, it mainly includes fracturing pipeline connection and fracturing pipeline pressure resistance test.

[0048] Step 31: The combined well-to-surface fracturing pipeline mainly includes: surface-to-surface directional well fracturing pipeline, mining fracturing pipeline, and high-pressure resistant hose. The surface-to-surface directional well fracturing pipeline is designed with high-pressure resistant tubing, and the tubing is connected by threads. The threaded connection between the tubing is tightened by the surface drilling rig, which can effectively achieve a pressure-bearing and sealing connection between the tubing. The coal fracturing pipeline is designed with oil-specific fracturing pipelines, but it is shorter than the oil-specific fracturing pipelines, which is convenient for underground pipeline transportation in coal mines. The mining fracturing pipeline is connected by a hydraulic jack, and the connection between the hydraulic jacks is tightened by intermittent impact on the hydraulic jack head with a heavy hammer, which can effectively achieve a pressure-bearing and sealing connection between the fracturing pipelines, and the hydraulic jack connection method facilitates the dismantling of the fracturing pipelines. The connection between the directional well and the underground fracturing pipeline is mainly through high-pressure resistant hose, and the connection between them is through a hydraulic jack. After the fracturing pipeline, mining fracturing pipeline, and high-pressure resistant hose are successfully connected in the directional well on the surface, their inner diameters are the same, and the joints are flat.

[0049] Step 32: Pressure-bearing test of surface-underground combined fracturing pipelines, which is mainly used to inspect the pressure-bearing and sealing connection effect among fracturing pipelines passing through the surface directional well, mining fracturing pipelines and high-pressure resistant flexible pipelines. On the ground, the total fracturing pipelines converged to the wellhead by multiple parallel fracturing pump trucks are connected with the oil tubing in the directional well passing through the ground, then the fracturing pipeline at the orifice end of the directional long borehole in the coal mine is blocked by a high-pressure resistant valve, finally multiple fracturing pump trucks on the ground pump clean water into the fracturing pipelines until the pressure on the main pipeline of the surface wellhead reaches 5 MPa, then the displacement is adjusted back and forth intermittently within a certain range, and this lasts for 5 minutes. After ensuring that the pressure on the main pipeline of the surface wellhead reaches 50 MPa and stabilizes for 30 minutes, if the pressure drop is less than 0.5 MPa, the pressure test of the surface-underground combined fracturing pipelines is qualified; otherwise, the pressure-bearing sealing connection of the fracturing pipelines shall be re-performed until the pressure test is qualified.

[0050] Step 4: Perform staged perforation fracturing by sand blasting using a single-packer backward dragging perforation fracturing tool string, as Figure 6 shown. The oil tubing is connected to the perforation fracturing tool string, then the coal mine underground drilling rig is used to run the perforation fracturing tool string into the bottom of the directional long borehole through continuous tubing thread connection, then the orifice pressure-bearing device of the directional long borehole realizes the sealing of the orifice, and the surface fracturing pump truck starts to inject clean water. The injected high-pressure clean water causes the packer connected to the front section of the perforation fracturing tool string to expand and seal, realizing the sealing of the bottom of the directional long borehole. The coal mine underground drilling rig is used to drag the oil tubing backward to drag the perforation fracturing tool string to the designed borehole depth position. At this time, the entire borehole of the directional long borehole is in a sealed state, and a certain proportion of fine sand is started to be mixed into the clean water injected by the surface fracturing pump truck. The high-pressure sand-carrying clean water flows through the perforation fracturing tool string in the directional long borehole, and jets the casing under the action of the pressure difference inside and outside the tool string. When the pressure on the main pipeline of the surface wellhead has a sudden change of sudden drop and then rise, it indicates that the casing has been perforated and perforation holes have been formed on the casing. After the perforation holes are formed on the casing, the injection displacement of clean water and sand content are adjusted to the initial fracturing design parameters. After the designed fracturing volume of the current fracturing section is injected, the surface injection of fracturing clean water is stopped, and pressure relief in the directional long borehole is started. When the pressure is relieved to zero, the orifice pressure-bearing device of the directional long borehole is removed, the coal mine underground drilling rig is used to drag the oil tubing backward, and the perforation fracturing tool string in the borehole is taken out, and the implementation of this fracturing section is completed. Continue the next fracturing: install a packer at the front section of the perforation fracturing tool string, use the coal mine underground drilling rig to run the perforation fracturing tool string to the designed borehole depth position of the directional long borehole again through continuous tubing thread connection, then the orifice pressure-bearing device of the directional long borehole realizes the sealing of the orifice, and the surface fracturing pump truck starts to inject clean water. The injected high-pressure clean water causes the packer connected to the front section of the perforation fracturing tool string to expand and seal, realizing the sealing and isolation of the previous fracturing section of the directional long borehole, as Figure 7As shown, the perforation fracturing tool string is dragged to the designed drilling depth using a retractable tubing system from the underground coal mine drilling rig. At this point, the entire directional long borehole is sealed. A certain proportion of fine sand is mixed into the clean water injected from the surface fracturing pump truck. The high-pressure, sand-carrying clean water flows through the perforation fracturing tool string in the directional long borehole. Under the pressure difference between the inside and outside of the tool string, the casing is ejected. When the pressure on the main pipeline at the wellhead suddenly decreases and then rises again, it indicates that the casing has been perforated and a perforation hole has been formed on the casing. After the hole is formed on the casing at the surface, the injection water fracturing flow rate and sand content are adjusted to the initial fracturing design parameters. After the designed fracturing volume for the current fracturing section is injected, the injection of fracturing water at the surface is stopped, and the pressure is released from the directional long borehole. When the pressure is released to zero, the pressure-bearing device at the orifice of the directional long borehole is removed. The perforation fracturing tool string is then removed from the borehole using a retractable tubing system from the underground coal mine drilling rig. This completes the fracturing section. The same process is applied to each subsequent fracturing segment designed in this way, until all designed fracturing segments are completed.

[0051] Step 5: Use a double-sealed, retractable drag-type perforation fracturing tool string to perform directional drilling with casing reinforcement throughout the entire hole, such as... Figure 8 As shown.

[0052] Step 51: Using a coal mine drilling rig, the packer set in the casing in step 4 is removed by continuously connecting the drill rod threads and using the drill bit. The packer at the bottom of the directional long borehole is retained. The remaining packer debris in the casing of the directional long borehole is cleaned by using the coal mine drilling rig with a large displacement circulation.

[0053] Step 52: Connect the perforation fracturing tool string to the tubing. Then, using a coal mine drilling rig, lower the perforation fracturing tool string into the designed position within the directional long borehole through continuous tubing thread connections. The pressure-bearing device at the borehole opening seals the opening. A surface fracturing pump truck then begins injecting clean water. The injected high-pressure water seals the expansion packers connected to the front and rear ends of the perforation fracturing tool string. At this point, the section between the expansion packers at the front and rear ends of the perforation fracturing tool string must avoid the fracturing perforation hole described in Step 4. The entire directional long borehole within the section between the expansion packers at the front and rear ends is then sealed. Figure 9As shown, a certain proportion of fine sand is mixed into the clean water injected by the surface fracturing pump truck. The high-pressure, sand-carrying clean water flows through the perforation fracturing tool string in the directional long borehole. Under the action of the pressure difference inside and outside the tool string, the casing is ejected. When the pressure on the main pipeline at the wellhead on the surface suddenly decreases and then rises again, it indicates that the casing has been perforated and a densified perforation has been formed on the casing. The injection of fracturing clean water on the surface is stopped, the pressure bearing device at the orifice of the directional long borehole is removed, and the oil pipe is dragged by the reverse of the coal mine drilling rig, dragging the perforation fracturing tool string to the next designed densified perforation section. Construction of another reinforced perforation section begins. Again, using a surface fracturing pump, high-pressure water is injected to seal the expansion packers connected to the front and rear ends of the perforation fracturing tool string. At this point, the section between the expansion packers must avoid the fracturing perforation holes described in step 4. The entire directional borehole within this section is now sealed. A certain proportion of fine sand is mixed into the water injected by the surface fracturing pump. The high-pressure, sand-laden water flows through the perforation fracturing tool string within the directional borehole. Under the pressure difference between the inside and outside of the tool string, the casing is ejected. When the pressure on the main wellhead pipeline at the surface suddenly decreases and then increases, it indicates that the casing has been perforated, and reinforced perforations have been formed on the casing. This process is repeated for each subsequent designed reinforced perforation section until all designed reinforced perforation sections are completed. Implementing a denser perforation density with directional long-hole casing ensures that the reduced strength of the casing must be sufficient to resist the outward extrusion strength of the casing against the vertical stress of the overlying strata. In other words, the casing strength after perforation must be greater than the vertical stress of the overlying strata.

[0054] Example 2: This embodiment provides a method for managing combined rockburst and gas disasters in coal mine areas, such as... Figures 10 to 11 As shown, this embodiment also includes steps 1 to 5, and is the same as steps 1 and 3 in embodiment 1, except that: In step 2 of this embodiment, the first section of the directional long borehole in the coal mine is cemented with casing, while the second section is an open hole without casing; specifically including: Based on the location of the underground directional long borehole determined in step 1, an underground directional long borehole is drilled, and a surface directional through-hole is simultaneously constructed. The borehole opening is designed to be slightly higher than the bottom, and the drilling trajectory is controlled within a downward dip range of 1~1.5°. Figure 5As shown, ensuring the drilled directional long borehole trajectory is downward sloping and smooth is crucial to guarantee the smooth installation of the internal screen throughout the entire borehole after the segmented fracturing process. This also effectively facilitates the natural separation of depressurized gas and formation water during the coal seam mining process, achieving efficient depressurized gas extraction. The implemented underground directional long borehole design is a two-section borehole structure. The first section must be drilled at least 10m and have high-quality casing cemented, ensuring sufficient pressure on the wellhead equipment during fracturing. The second section is an open hole without casing. For surface directional through-holes, a two-section borehole structure is sufficient, requiring casing cementing throughout the entire well.

[0055] Step 4 of this embodiment includes: A combined well-to-surface dual-sealed retractable perforation fracturing tool string was used to perform segmented perforation fracturing throughout the open hole of a directional long borehole, such as... Figure 10 As shown, the tubing connects to the perforation fracturing tool string. Then, using a coal mine drilling rig, the perforation fracturing tool string is lowered into the designed fracturing section of the directional long borehole via continuous tubing thread connections. The borehole opening is then sealed by a pressure-bearing device. A surface fracturing pump truck begins injecting water. The injected high-pressure water causes the expansion packers connected to the front and rear ends of the perforation fracturing tool string to expand. The expanded packers pressurize and seal against the borehole wall of the directional long borehole, achieving a sealed state throughout the entire length of the directional long borehole between the front and rear expansion packers. Figure 10 As shown, a certain proportion of fine sand is mixed into the clean water injected by the surface fracturing pump truck. The high-pressure, sand-carrying clean water flows through the perforation fracturing tool string in the directional long borehole. Under the pressure difference inside and outside the tool string, it is sprayed onto the wall of the directional long borehole. When the pressure on the main pipeline at the wellhead suddenly decreases and then rises, it indicates that the wall of the directional long borehole has been perforated, and a perforation hole has been formed on the wall of the directional long borehole. The surface begins to adjust the injection water fracturing flow rate and sand content to the initial fracturing design parameters. After the designed fracturing volume of the current fracturing section is injected, the injection of fracturing water on the surface is stopped, and the pressure is released in the directional long borehole. When the pressure is released to zero, the pressure-bearing device at the directional long borehole opening is removed, and the perforation fracturing tool string is dragged to the next adjacent designed fracturing section by using the reverse dragging of the tubing by the coal mine drilling rig. This process is repeated for each subsequent designed fracturing section until all designed fracturing sections are completed.

[0056] Step 5 of this embodiment includes: Step 5: A screen pipe is installed inside the open hole of a long directional borehole in the coal mine, such as... Figure 11 As shown.

[0057] Step 51: After completing all the fracturing sections designed in Step 4 within the directional long borehole, the same drill bit as the final borehole size is lowered again using a coal mine drilling rig within the directional long borehole to drill to the bottom and finish the entire borehole. Simultaneously, the drilling time at different depths during borehole finishing is recorded. A longer drilling time indicates that the original formation structure was damaged during fracturing, making borehole narrowing more likely at that depth. A shorter drilling time, or the drill bit directly passing through the borehole depth, indicates that borehole narrowing is less likely at that depth. Finally, when the drill bit reaches the bottom of the borehole, a high-volume circulating fracturing pump truck is used to flush away any remaining rock cuttings from the open borehole.

[0058] Step 52: Utilize the threaded connection of the screen pipes to each other and the casing pipes in the coal mine underground drilling rig, such as... Figure 11 As shown, it is then fed into the bottom of the directional long borehole. Based on the drilling time recorded during the process of trimming the directional long borehole in step 51, the screen pipes installed in the sections with larger drilling times are designed to be small-aperture density screen pipes or un-apertured sleeves that match the size of the screen pipes. This can prevent the screen pipes from being squeezed, deformed, or cut off due to further diameter reduction in this section of the hole. For sections with smaller drilling times or where the drill bit is directly lowered through the hole depth, normally designed large-aperture density screen pipes are installed. When the screen pipe is lowered to the section overlapping with the first-opening sleeve, an un-apertured second-opening sleeve is used, and this section of the second-opening sleeve extends 0.5~1m beyond the borehole opening. Figure 7 As shown, a threaded sealing short section is then used to seal the opening of the directional long borehole between the first and second casing sections. The portion of the second casing extending out of the borehole is used to connect the gas extraction pipeline. Overall, the screen pipes lowered into the directional long borehole must have an external extrusion resistance strength greater than the vertical stress of the overlying strata at the corresponding formation depth of the directional long borehole.

[0059] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0060] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for controlling combined rockburst and gas disasters in coal mining areas, characterized in that: Includes the following steps: Step 1: Determine the three-dimensional spatial position of the directional long borehole trajectory in the coal mine; The location of the hard key layer and the fracture zone of the overlying strata of the coal seam are determined by calculation, and the vertical position of the directional long borehole trajectory in the coal mine is determined; and the position of the directional long borehole trajectory in the coal mine is determined on the horizontal projection surface. Step 2: Based on the location of the underground directional long borehole determined in Step 1, implement the underground directional long borehole with a two-section borehole structure, and at the same time implement the surface through directional well with a two-section well structure. Among them, the first opening structure of the directional long borehole in the coal mine is to be cemented with casing, and the second opening structure is to implement one of the following two structures: Second opening structure I is to be ... Step 3: Connection and pressure test of the well-to-surface fracturing pipeline; A high-pressure resistant hose is used to connect the surface-through directional well fracturing pipeline to the underground fracturing pipe in the coal mine; the pressure-bearing sealing connection effect between the surface-through directional well fracturing pipeline, the underground fracturing pipe, and the high-pressure resistant hose is verified by pressure test. Step 4: Use a single-seal retractable drag perforation fracturing tool string to perform sandblasting perforation segmented fracturing and use it as fracturing method I for the two-section structure I in step 2; or use a double-seal retractable drag perforation fracturing tool string to perform perforation segmented fracturing in the open hole of a directional long borehole and use it as fracturing method II for the two-section structure II in step 2. Step 5: If step 4 uses fracturing method I, then a double-sealed, retractable drag perforation fracturing tool string is used to perform directional long drilling with casing reinforcement perforation throughout the entire hole; if step 4 uses fracturing method II, then a screen pipe is installed in the open hole of the directional long drilling.

2. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 1, calculating and determining the location of the hard, critical layer of the overlying strata of the coal seam includes: Step a1, Analysis of Hard Key Layers Based on Overburden Structure Characteristics: Using the comprehensive geological columnar section of the coal seam roof overburden, based on the thickness and lithology discrimination method of the rock strata as key layers, the thick and hard rock strata that may become hard key layers are initially identified as the basic hard key layers; through the hard key layer stiffness condition discriminant formula, it is determined whether the basic hard key layer meets the stiffness condition. If it does, the rock strata is a hard key layer, and this is extrapolated to the last hard rock layer. Step a2, based on the analysis of the main induced impact hard key layers: the overburden strata of the coal seam fracture in sequence and release energy. This energy decays exponentially in the rock mass. By calculating the amount of energy released and transferred to the coal body after decay, the hard rock strata that pose an impact risk to the working face are identified, and the hard key layers are determined. Step a3: Based on the two types of hard key layers determined in steps a1 and a2, select the rock strata within the height range of the intersection of the two as the hard key layers to be fracturing.

3. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 2, characterized in that, In step 1, the location of the fracture zone in the overlying strata of the coal seam is: H K ~H K +H L , where H K H represents the thickness of the caving zone in the overlying strata. L This represents the thickness of the fracture zone in the overlying strata.

4. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 3, characterized in that, In step 1, based on the location of the hard key layer and the location of the fracture zone in the overlying strata of the coal seam, when the hard key layer is located above or below the fracture zone, under the given fracturing parameters, the upward and downward fracture propagation height along the vertical position of the directional long borehole must meet the following requirements: the fracturing fracture propagates to the hard key layer to half the thickness of the hard rock layer, and the fracturing fracture propagates to the fracture zone to at least the outer edge of the fracture zone boundary.

5. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 1, determining the position of the directional long borehole trajectory on the horizontal projection plane in the coal mine includes: The trajectory of a long directional borehole in a coal mine is located on one side of the return airway of the coal seam working face. The formula for calculating the distance between the location of the long directional borehole on the horizontal projection plane and the return airway is as follows: In the formula, The distance from the location of the long directional borehole in the coal mine to the return airway on the horizontal projection plane is expressed in meters. Let the thickness of the caving zone be m; B is the thickness of the fracture zone, in meters; B is the distance from the outer boundary of the directional long borehole in the coal mine to the O-ring, in meters. The dip angle of the coal seam is °; The angle between the line connecting the outer boundary of the O-shaped ring and the mining boundary and the coal seam.

6. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 2, the trajectory of the directional long borehole drilling process is controlled within the range of 1~1.5° in the downward dip direction; the first opening of the directional long borehole is drilled for at least 10m; In the two-section structure I, a centralizer is installed on the outside of every three casings to ensure that the casings are centered; the entire section of the surface-penetrating directional well is cemented with casing.

7. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 3, the fracturing pipeline in the surface-penetrating directional well is made of tubing, and the tubing is connected by threads to achieve pressure-bearing sealing; the fracturing pipes in the mine are connected by oil hoses to achieve pressure-bearing sealing; the fracturing pipeline in the surface-penetrating directional well, the fracturing pipes in the mine, and the high-pressure resistant hose have the same inner diameter after being connected, and the joint is flat inside. Step 3, the pressure test includes: on the surface, multiple fracturing pump trucks are connected in parallel to the main pipeline at the wellhead and connected to the oil pipe in the directional well. Then, the fracturing pipeline at the end of the long directional borehole in the coal mine is sealed with a high-pressure resistant valve. Finally, on the surface, multiple fracturing pump trucks pump clean water until the pressure on the main pipeline at the wellhead reaches 5MPa. The discharge rate is adjusted intermittently for 5 minutes to ensure that the pressure on the main pipeline at the wellhead reaches 50MPa and is stabilized for 30 minutes. If the pressure drop is less than 0.5MPa, the pressure test of the well-to-surface fracturing pipeline is qualified.

8. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 4, fracturing method I includes: connecting the tubing to the perforation fracturing tool string; using the drilling rig to lower the perforation fracturing tool string into the bottom of the directional long borehole; the pressure-bearing device at the borehole opening of the directional long borehole achieves borehole opening sealing; using a surface fracturing pump truck to inject high-pressure clean water to separate the packer connected to the front section of the perforation fracturing tool string, achieving bottom sealing of the directional long borehole; using the drilling rig to drag the tubing backward to the designed borehole depth position; the surface fracturing pump truck injects high-pressure sand-carrying clean water, which, under the action of the pressure difference inside and outside the tool string, sprays the casing; when the pressure on the main pipeline at the wellhead on the surface suddenly decreases and then rises again, the casing is perforated to form a perforation hole; adjusting the injected clean water fracturing discharge rate and sand content as the initial fracturing design parameters; after the designed fracturing volume is injected, the injection is stopped, the pressure is released and the perforation fracturing tool string in the hole is removed, and this fracturing section is completed. This process is repeated until all designed fracturing sections are completed.

9. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 1, characterized in that, In step 4, fracturing method II includes: connecting a perforation fracturing tool string to tubing; using a coal mine drilling rig to lower the perforation fracturing tool string into the designed fracturing section position within the directional long borehole; a pressure-bearing device at the borehole opening to achieve a borehole seal; and the surface fracturing pump truck injecting high-pressure water to inflate the expansion packers connected to the front and rear ends of the perforation fracturing tool string. The inflated packers pressurize and seal against the open hole wall of the directional long borehole, achieving a sealed directional long borehole within the length range between the front and rear expansion packers. In this state, the surface fracturing pump truck injects high-pressure, sand-carrying water, which, under the pressure difference between the inside and outside of the tool string, is sprayed onto the wall of the directional long borehole. When the pressure on the main pipeline at the wellhead suddenly decreases and then rises again, the open hole wall is perforated, forming a perforation hole. The injection water fracturing discharge rate and sand content are adjusted to the initial fracturing design parameters. After the designed fracturing volume of the current fracturing section is injected, the injection is stopped, the pressure is released, and the perforation fracturing tool string is dragged to the next adjacent designed fracturing section until all designed fracturing sections are completed.

10. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 8, characterized in that, In step 5, the use of a double-sealed, retractable drag-type perforation fracturing tool string to implement casing-reinforced perforation throughout the directional long borehole includes: Use the coal mine drilling rig, drill rod and drill bit to remove the packer set in the casing. The packer located at the bottom of the directional long borehole is retained. The residual packer debris in the casing is flushed out. The tubing connects to the perforation fracturing tool string. The drilling rig lowers the perforation fracturing tool string into the designed position within the directional long borehole via the tubing. The pressure-bearing device at the borehole opening ensures a seal. A surface fracturing pump truck then injects high-pressure water to seal the expansion packers connected to the front and rear ends of the perforation fracturing tool string. The section between the front and rear expansion packers avoids the perforation hole formed in step 4. At this point, the entire directional long borehole within the section between the front and rear expansion packers is sealed. The surface fracturing pump truck injects high-pressure, sand-carrying water that flows through the tool string under the pressure difference, jetting the casing. When the pressure on the main wellhead pipeline at the surface experiences a sudden drop followed by a rise, the casing perforates, forming a densified perforation. Injection stops, and the process continues to the next designed densified perforation section, completing all designed densified perforation sections. The strength of the casing after perforation must be greater than the vertical stress of the overlying strata.

11. The method for controlling combined rockburst and gas disasters in coal mine areas as described in claim 9, characterized in that, Step 5, which involves inserting a screen tube into the open hole of a directional long borehole, includes: Using a coal mine drilling rig, a drill bit of the same size as the final hole was lowered into the directional long borehole and drilled to the bottom of the hole to finish the entire hole. At the same time, the drilling time at different hole depths was recorded when the drill bit finished the hole. The residual rock cuttings in the open hole of the directional long borehole were washed clean. The screen pipe and casing are connected by threaded connections using a coal mine drilling rig and sent to the bottom of the directional long borehole. Based on the recorded drilling time, the screen pipes in the long drilling sections are either small-aperture density screen pipes or unperforated casings that match the screen pipe size. In the short drilling sections or where the drill bit is directly lowered through the borehole depth, normally designed large-aperture density screen pipes are used. When the screen pipe is lowered to the section overlapping with the first-stage casing, an unperforated second-stage casing is used, with this section extending 0.5~1m beyond the borehole opening. A threaded sealing short section is used to seal the first-stage and second-stage casings at the borehole opening. The portion of the second-stage casing extending beyond the borehole opening is used to connect to the gas extraction pipeline. The screen pipes lowered into the directional long borehole have an external extrusion resistance greater than the vertical stress of the overlying strata at the corresponding formation depth of the directional long borehole.

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