Method for increasing permeability of coal seam based on kilometer directional drilling and hydraulic flushing

Abstract

The present application relates to the technical field of coal seam permeability improvement, and particularly relates to a method for improving the permeability of coal seam based on kilometer directional drilling and hydraulic flushing, which comprises the following steps: 1) arranging drilling; 2) drilling opening and sealing; 3) directional drilling construction and gas blowout prevention and extraction; 4) hydraulic permeability improvement; and 5) gas extraction. Compared with the prior art, the present application uses kilometer directional drilling technology and high-pressure water to disturb the coal body in the whole drilling process, and the development of coal body fissures is more conducive to the release of gas, and the gas blowout prevention and collection device can achieve good gas control effect.

Description

Technical Field

[0001] This invention belongs to the field of gas control technology and relates to the research field of coal seam permeability enhancement technology. Specifically, it is a method for increasing the permeability of coal seams based on kilometer-long directional drilling and hydraulic perforation. Background Technology

[0002] After conventional drilling is carried out, it is difficult to guarantee the drilling trajectory because conventional drilling does not have a measurement system. If the trajectory is not properly constructed, there will be a large blind spot in the extraction, which will bring gas problems to the later mining. At best, the gas will exceed the limit, and at worst, a gas explosion will occur. Furthermore, the No. 2 coal seam in Jining has poor permeability (the absolute gas emission of Jining Mine is 105.42 m3 / min, the relative emission is 15.34 m3 / t, and the gas level assessment conclusion in 2021 is a high gas mine; the coal seam currently being mined is the No. 2 coal seam, the permeability coefficient of the No. 2 coal seam is 0.023008~0.085813 m2 / MPa2·d, and the borehole gas flow attenuation coefficient is 0.059d-1, which is a relatively difficult coal seam to extract). Even if the borehole can be drilled and the construction can be carried out according to the design trajectory, it is difficult to guarantee that the gas rich in the coal seam can be extracted smoothly.

[0003] Therefore, it is more important to improve the permeability of coal seams to enhance borehole extraction efficiency, in order to solve the problems of low extraction efficiency in low-permeability outburst coal seams and poor pressure relief effect in stress-dominated coal seams. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by proposing a method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation, comprising the following steps:

[0005] 1) Drill hole arrangement: Select the spacing, row spacing, angle, diameter and length of the drill holes according to the occurrence of the coal seam to be pumped and the pumping radius;

[0006] 2) Drilling and sealing: Determine the angle and orientation of the kilometer directional drilling rig, fix the kilometer directional drilling rig, and seal the hole after drilling is completed;

[0007] 3) Directional drilling and blowout gas extraction: After the borehole is sealed, a kilometer-long directional drilling rig is used and the first drilling tool is used to drill directionally to the final hole position, and then the drill rod is pulled out.

[0008] Install a gas blowout prevention and collection device on the borehole to carry out blowout prevention and extraction during directional drilling.

[0009] Hydraulic permeability enhancement: A second drilling tool is used to drill to the bottom of the hole, and a backward drilling method is adopted to enhance permeability and create a cavity. The diameter of the drilling extraction hole is increased by hydraulic permeability enhancement.

[0010] Gas extraction: After drilling is completed, the boreholes are connected to the extraction system for extraction.

[0011] Based on the above scheme, step 2) drilling and sealing: determining the angle and orientation of the kilometer directional drilling rig, fixing the kilometer directional drilling rig, and sealing the hole after drilling are completed, specifically includes:

[0012] Select a Φ120mm drill bit and directional drill rod to perform rotary drilling for hole opening;

[0013] Select a Φ165mm reaming drill bit and reaming drill rod and use rotary drilling to perform the first reaming operation;

[0014] Select a Φ194mm reaming drill bit and reaming drill rod and use rotary drilling to perform the second reaming;

[0015] A bottom sealing pipe is installed inside the borehole, and grouting and sealing are carried out using a two-plug-one-injection bag-type pressurized grouting process, with a pressure not lower than 1.5 MPa.

[0016] Based on the above scheme, in steps 3) and 4):

[0017] The first drilling tool includes a Φ120mm drill bit, a Φ73 guiding system, and a Φ73mm cable-connected high-pressure sealed triangular spiral groove directional drill rod;

[0018] The second drilling tool includes a Φ120mm drill bit, a water jet, and a Φ73mm cable-connected high-pressure sealed triangular spiral groove directional drill rod.

[0019] Based on the above scheme, step 3) directional drilling and blowout prevention gas extraction: After the borehole is sealed, a kilometer-long directional drilling rig is used and the first drilling tool is used to directionally drill to the final hole position, and then the drill rod is pulled out. The specific steps include:

[0020] The 1,000-meter directional drilling rig was used to drill to the designed depth of 320m (the designed depth can be adjusted according to the specific situation). After pulling out the drill rod and replacing it with a water jet, the drill was sent to the bottom of the hole.

[0021] Based on the above scheme, step 4) involves using a second drilling tool to drill to the bottom of the hole, employing a retraction method to enhance permeability and create a cavity, and increasing the borehole extraction diameter through hydraulic permeability enhancement. This step specifically includes:

[0022] Fixed-point cavity creation: During the permeability enhancement process, the flow rate and water pressure are adjusted at any time according to the permeability enhancement effect. The spacing between each point is 10m from the inside to the outside. Adjacent boreholes are created using a staggered permeability enhancement cavity creation method until the borehole opening. Each borehole creates 28 cavity segments, ultimately forming a permeability enhancement cavity segment with a length of 1m and a diameter of 800mm. The amount of slag coal returned in each cavity segment is not less than 0.7t, and the pump pressure is not less than 15MPa during permeability enhancement.

[0023] By increasing the permeability of the coal seam during coal extraction, the entire coal seam expands, thereby relieving pressure and eliminating outbursts.

[0024] Based on the above scheme, it also includes: after the permeability enhancement is completed, the amount of coal dust discharged from each permeability enhancement borehole is counted, and the borehole is sealed and pumped out, and a metering device is installed in each borehole.

[0025] The gas concentration, flow rate, and negative pressure data of the permeability enhancement orifice are measured once a day, and the recorded data are statistically analyzed.

[0026] Based on the above scheme, the gas blowout prevention and collection device in step 3) includes a blowout prevention structure for collecting gas.

[0027] The outlet end of the orifice blowout prevention structure is connected to the gas-slag separator for collecting water and drill cuttings and the inlet end of the first buffer bag for buffering, respectively.

[0028] and

[0029] The outlet end of the first buffer bag is connected to the pipeline of the blowout preventer extraction system used for gas extraction.

[0030] Based on the above scheme, the gas-slag separator includes a first cleaning water head installed on the housing for spraying water into the housing when a small amount of drill cuttings accumulate inside the housing;

[0031] Exhaust pipe used to discharge gas;

[0032] A negative pressure gauge used to measure the pressure inside the chamber;

[0033] An observation window for observing the amount of drill cuttings inside the chamber;

[0034] And a slag outlet for discharging drill cuttings and water from the tank.

[0035] Based on the above scheme, the gas-slag separator also includes a second cleaning head for spraying water into the tank when a large amount of drill cuttings accumulates inside the tank.

[0036] Based on the above scheme, when the drilling depth exceeds 200m, the gas blowout prevention and collection device further includes:

[0037] A second buffer bag for buffering, connected to the outlet end of the gas-sludge separator;

[0038] The outlet end of the second buffer bag is connected to the piping of the blowout prevention and extraction system.

[0039] Compared with existing technologies, this invention utilizes kilometer-long directional drilling technology combined with high-pressure water to disturb the coal seam throughout the borehole. The resulting coal seam fractures are more conducive to gas release. The kilometer-long directional drilling technology, operating along the designed borehole trajectory, eliminates blind spots. Large-diameter, long-distance drilling avoids the waste of sealing materials and labor through repeated sealing, improving production efficiency and creating favorable conditions for continuous mine production. The drilling rig is centralized, simple, convenient, flexible, and reliable, significantly reducing labor intensity. The rig can be moved independently, making installation quick and easy, greatly shortening preparation time. High-pressure water perforation throughout the coal seam enhances permeability, shortening extraction time and improving gas extraction efficiency, preventing mine production stoppages due to gas problems. Furthermore, the use of in-seam drilling with high-pressure water permeability enhancement technology improves gas extraction efficiency and reduces drilling workload. It also isolates the continuous gas output from the coal roadway to be excavated, eliminating the power source for coal seam outbursts. The coal seam and gas are uniformly depressurized, achieving the goal of rapid outburst-free excavation in the coal roadway. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the gas blowout prevention and collection device in Embodiment 3 of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0042] Example 1

[0043] A method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation includes the following steps:

[0044] 1) Drill hole arrangement: Select the spacing, row spacing, angle, diameter and length of the drill holes according to the occurrence of the coal seam to be pumped and the pumping radius;

[0045] 2) Drilling and sealing: Determine the angle and orientation of the kilometer directional drilling rig, fix the kilometer directional drilling rig, and seal the hole after drilling is completed;

[0046] 3) Directional drilling and blowout gas extraction: After the borehole is sealed, a kilometer-long directional drilling rig is used and the first drilling tool is used to drill directionally to the final hole position, and then the drill rod is pulled out.

[0047] Install a gas blowout prevention and collection device on the borehole to carry out blowout prevention and extraction during directional drilling.

[0048] Hydraulic permeability enhancement: A second drilling tool is used to drill to the bottom of the hole, and a backward drilling method is adopted to enhance permeability and create a cavity. The diameter of the drilling extraction hole is increased by hydraulic permeability enhancement.

[0049] Gas extraction: After drilling is completed, the boreholes are connected to the extraction system for extraction.

[0050] Example 2

[0051] This embodiment takes a certain mine as an example. The absolute gas emission rate of the mine is 105.42 m3 / min, the relative emission rate is 15.34 m3 / t, and the gas level assessment conclusion in 2021 is a high-gas mine. The coal seam currently being mined in the mine is No. 2 coal seam. The permeability coefficient of No. 2 coal seam is 0.023008~0.085813 m2 / MPa2·d, and the borehole gas flow attenuation coefficient is 0.059d-1, which is a relatively difficult coal seam to pump out.

[0052] In view of the actual situation of the mine, this embodiment provides a method for increasing the permeability of coal seams based on kilometer-long directional drilling and hydraulic perforation, which specifically includes the following steps:

[0053] 1) Drill hole arrangement: Select the spacing, row spacing, angle, diameter and length of the drill holes according to the occurrence of the coal seam to be pumped and the pumping radius;

[0054] 2) Drilling and sealing: Determine the angle and orientation of the kilometer directional drilling rig and fix the kilometer directional drilling rig. After drilling is completed, seal the hole.

[0055] Specifically, it includes:

[0056] Select a Φ120mm drill bit and directional drill rod to perform rotary drilling for hole opening;

[0057] Select a Φ165mm reaming drill bit and reaming drill rod and use rotary drilling to perform the first reaming operation;

[0058] Select a Φ194mm reaming drill bit and reaming drill rod and use rotary drilling to perform the second reaming;

[0059] A lower sealing pipe is installed inside the borehole. The lower sealing pipe is grouted using a two-plug-one-injection bag-type pressurized grouting sealing process, and the pressure shall not be lower than 1.5 MPa.

[0060] Specifically, the borehole sealing process employs a "two-plug-one-injection" bag-type pressurized grouting sealing technique. The borehole is sealed in one pass, using a 6-inch sealing tool to seal 18m of the borehole. A 6-inch to 4-inch reducer is installed at the borehole opening, and a 4-inch flanged flame-retardant buried conduit is used for connection, integrated into the Φ426mm extraction pipeline system within the roadway for drainage. The bag-type grouting sealing method is an early form of the "two-plug-one-injection" pressurized grouting sealing method. The bag-type sealing device uses two bags to plug the borehole, with a grout outlet between the two bags. Its sealing principle is as follows: grout is injected into the bags through the grouting pipe. After the bags expand, they make tight contact with the borehole wall. When the grouting pressure exceeds the opening pressure of the grout outlet, the grout is injected into the gap between the two bags, entering the gap between the bags and the borehole wall, as well as the coal seam fractures at a certain depth around the borehole, thus achieving the sealing of the extraction borehole.

[0061] Using one gas-water-slag separator and one 10m blowout preventer / buffer bag, a simultaneous drilling and extraction process was implemented, with a borehole diameter of 194mm and a sealing length of 18m. A "two-plug-one-injection" bag-type pressurized grouting sealing process was employed, using 6-inch PVC "two-plug-one-injection" bag-type pressurized sealing technology. The pressure must not be lower than 1.5MPa. Under normal geological conditions, the grouting sealing depth was 18m. In areas affected by geological structures (fractured zones), the sealing depth was not less than 24m, with two pressurized grouting operations to seal surrounding coal seam fractures and ensure extraction effectiveness. If surrounding fractures were well-developed, the sealing depth should be increased as needed.

[0062] Drilling and sealing process

[0063] ①Inspect the grouting pump

[0064] a. The grouting pump should be inspected each time it is used (except when the grouting pump is used continuously).

[0065] b. Clean the debris from the filling tank and check the connection status of each pipeline to ensure that the connection of each pipeline is reliable;

[0066] c. Fill the grouting pump's grouting tank with water and test whether the grouting pump's connecting pipeline is unobstructed (water should be coming out of the end of the pipeline). If there are any blockages, deal with them in time.

[0067] d. Drain the test water from the grouting pump and connecting pipelines;

[0068] Only after the above work is completed can the next step of sealing the hole be carried out.

[0069] ② Sealing steps

[0070] Place a set of sealing devices into the drilled holes in sequence. The 6-inch PVC pipes (small end inward, large end outward) must be tightly connected and airtight. Do not insert or remove the pipes back and forth. When encountering resistance, slow down the pipe insertion speed.

[0071] b. When the PVC pipe with the bladder is 300mm away from the borehole, stop feeding the pipe, wipe the end of the PVC pipe clean with new cotton yarn, and lead the grouting pipe out of the borehole about 20-30mm.

[0072] c. Mix cement and water in a weight ratio of 0.75-0.9:1 and pour into the mixing bucket, stirring evenly (stirring time should be 5 minutes). After stirring, firmly connect the grouting pipe to the pneumatic grouting pump and begin grouting. The grouting pressure should not be less than 1.5 MPa. When grout seeps out of the return pipe, it indicates that the hole is full. At this time, use wire to tie the vent pipe and continue grouting to allow the mortar to seep into the coal wall. When water seeps out of the coal wall and bubbles appear, stop grouting, tie the grouting pipe with wire, and cut the grouting pipe with a handsaw. After grouting, clean the sealing pump. During the grouting process, adhere to the principle of "small flow rate, long time" to gradually increase the pressure inside the hole, and then pressurize to allow more mortar to seep into the coal wall, ensuring the airtightness of the sealing hole.

[0073] d. Cleaning the grouting pump: Add water to the grouting pump and keep the agitator running to clean the grouting pump. Stop cleaning only after the water returning from the grouting port is clear to ensure normal use next time.

[0074] e. Cut the exposed grouting pipe at the orifice with a utility knife.

[0075] After drilling, the borehole must be sealed and pumped out in a timely manner, ensuring that each borehole is sealed and connected.

[0076] The purpose of setting up the kilometer directional drilling rig is to construct directional drilling holes for gas drainage in coal mines. Therefore, there are many forms of kilometer directional drilling rigs. For example, the "Kilometer Directional Drilling Rig for Coal Mine Underground Tunnel" involved in patent CN 107420036 A can be used directly, or other types of kilometer directional drilling rigs can be used, which will not be elaborated here.

[0077] 3) Directional drilling and blowout gas extraction: After the borehole is sealed, use a kilometer-long directional drilling rig and the first drilling tool to drill to the final hole position, and then pull out the drill rod; use a kilometer-long directional drilling rig to drill to the design depth, pull out the drill rod, replace it with a water jet and send the drill to the bottom of the hole.

[0078] Specifically, the first drilling tool includes a Φ120mm drill bit, a Φ73 guiding system, and a Φ73mm cable-connected high-pressure sealed triangular spiral groove directional drill rod;

[0079] The second drilling tool includes a Φ120mm drill bit, a water jet, and a Φ73mm cable-connected high-pressure sealed triangular spiral groove directional drill rod.

[0080] Specifically, after the borehole is sealed, a Φ120mm drill bit + Φ73 guide system + Φ73mm through-cable high-pressure sealed triangular spiral groove directional drill rod is used to directionally drill to the final hole position. Then, the drill rod is pulled out and a Φ120mm drill bit + special water jet + Φ73mm through-cable high-pressure sealed triangular spiral groove directional drill rod is used to send the drill to the bottom of the hole and a backward-retreating method is used to enhance the penetration and create a cavity.

[0081] In this embodiment, the ZYL-6000D type tracked fully hydraulic kilometer-long directional drilling rig for coal mines was selected for construction. It was equipped with a special high-pressure pump truck, a wired measurement while drilling system, a cable-connected high-pressure sealed triangular spiral groove drill rod, and a triangular spiral groove screw motor. The clean water slag removal process was adopted, and the directional drilling was carried out normally to the design depth of 320m (the design depth can be adjusted according to the specific situation) to complete the directional drilling of the long borehole.

[0082] The kilometer-long directional drilling rig is mainly used for directional drilling in various engineering projects in coal mines, including gas drainage, grouting for fire prevention and extinguishing, coal seam water injection, hydraulic permeability enhancement, hydraulic fracturing, anti-outburst pressure relief, and geological exploration. It is suitable for various coal seams and rock formations with a rock strength coefficient f ≤ 10. The rig can move independently and turn on the spot, requiring a roadway or drilling site height greater than 3m, a width greater than 4.5m, and a cross-section greater than 12m². It can also be used for small-diameter diamond drilling in the exploration of metallic and non-metallic solid mineral deposits. Currently, the ZYL-6000D kilometer-long directional drilling rig is commonly used with a dedicated high-pressure pump truck to complete the "drilling-permeability enhancement" operation.

[0083] Install a gas blowout prevention and collection device on the borehole to carry out blowout prevention and extraction during directional drilling.

[0084] Specifically, adjust the angle and fix the drilling rig according to the construction design requirements → drill 18m with a Ф120mm drill bit → enlarge the hole 18m with a Ф165mm drill bit → enlarge the hole 18m with a Ф194mm drill bit → seal the hole with a 6-inch PVC pipe for 18m → install the gas blowout prevention and collection device for simultaneous drilling and pumping. Drilling depth, diameter, and other parameters can be adapted to the actual construction requirements.

[0085] 4) Hydraulic permeability enhancement: Slowly increase the flow rate and pressure of the hydraulic permeability enhancement pump truck, the water jet opens automatically, and the permeability enhancement and cavity creation are carried out by retraction, thereby increasing the diameter of the borehole extraction hole through hydraulic permeability enhancement;

[0086] As a specific implementation plan, during construction, the kilometer-long directional drilling rig uses a Φ120mm drill bit and ordinary drill rod to directly open the hole using rotary drilling. For the hole sealing section, Φ165mm and Φ194mm reaming drill bits and ordinary drill rods are used to directly enlarge the hole using rotary drilling. After sealing, a Φ120mm drill bit + Φ73 guide system + Φ73mm cable-guided high-pressure sealed triangular spiral groove directional drill rod is used for directional drilling until the design position is reached. Then, after pulling out the drill rod, a Φ120mm drill bit + special water jet + Φ73mm cable-guided high-pressure sealed triangular spiral groove directional drill rod is used to drill to the bottom of the hole. A backward-retreating method is used for penetration enhancement, as shown in Table 1, which shows the combination of directional drilling and penetration enhancement tools.

[0087] Table 1. Combination of Directional Drilling and Permeability Enhancement Drilling Tools

[0088]

[0089] Among them, Φ120mm drill bit is a drill bit with a diameter of 120mm;

[0090] A Φ165mm reaming drill bit is a drill bit with a diameter of 165mm.

[0091] The Φ73 guide system includes a motor and a measuring system, which can be equipped with conventional equipment and will not be described in detail here.

[0092] The Φ73mm cable-connecting high-voltage sealed triangular spiral groove directional drill rod has a diameter of 73mm.

[0093] The wired high-pressure sealed triangular spiral groove drill pipe is mainly used in wired drilling directional hydraulic permeability enhancement systems (primarily composed of a mine-use explosion-proof and intrinsically safe computer, a mine-use intrinsically safe waterproof keyboard, and a measuring probe). The wired drill pipe transmits parameters such as the borehole inclination angle, azimuth angle, and tool face angle for drilling measurements, while simultaneously displaying the borehole parameter trajectory in real time. This allows the driller to monitor the drilling progress and adjust bend directions and process parameters promptly for precise drilling. The probe section uses a plug-in three-wing fixing method, making on-site assembly and disassembly simple and enabling composite directional drilling processes in complex formations. The drill pipe can withstand an internal pressure of 30 MPa, and its threads possess comprehensive performance characteristics of high torsional resistance, high bending resistance, and high sealing. It is suitable for wired drilling measurements in rotary drilling of extremely soft and fractured formations and coal seams with uneven hardness, and can also be used in drilling operations requiring high-pressure sealing. The drill pipe has high bending and torsional strength, good sealing performance, strong slag removal capacity, and can effectively solve borehole accidents such as stuck drill and buried drill.

[0094] As an exemplary implementation plan, after directional drilling reaches the designed depth of 320m (the designed depth can be adjusted according to specific circumstances), the drill rod is pulled out, replaced with a special water jet, and sent to the bottom of the hole. The flow rate and pressure of the hydraulic permeability enhancement pump are slowly increased (>15MPa), the water jet automatically opens, and the retreating hydraulic permeability enhancement operation begins. During the permeability enhancement process, the flow rate and water pressure are adjusted according to the permeability enhancement effect. Permeability enhancement cavity creation is carried out every 10m from the inside out until the hole opening. Each borehole creates 28 cavity segments, ultimately forming a permeability enhancement cavity segment with a length of 1m and a diameter of 800mm. The amount of slag and coal returned in each cavity segment is not less than 0.7t. The specific permeability enhancement process is as follows:

[0095] Fixed-point hole creation: The spacing between each point is 10m. Adjacent boreholes are created using a staggered permeability enhancement method. During permeability enhancement, the pump pressure is not less than 15MPa.

[0096] By enhancing permeability during coal extraction, the entire coal seam expands, achieving pressure relief and eliminating outbursts. During the experiment, the influence range of hydraulic permeability enhancement needs to be investigated to determine a reasonable branch spacing. The extraction rate during permeability enhancement should be controlled at 1.5 hours per cycle, and the coal output per cycle should not be less than 0.7t (0.5m³ of coal).

[0097] The principle of directional hydraulic permeability enhancement technology is as follows: After drilling to the designed depth using a kilometer-long directional drilling rig, high-pressure water jets are used to peel away the coal wall of the borehole, forming one or more sections of holes with a diameter much larger than the initial borehole diameter. This disrupts the stress balance of the original coal rock, causing the coal to shift in the direction of the holes (or inducing controllable small outbursts), thereby depressurizing the coal and achieving the combined effect of enhancing permeability and strengthening extraction.

[0098] Gas extraction: After drilling is completed, the boreholes are connected to the extraction system for extraction.

[0099] The extraction system uses conventional equipment in this field and is not a patentable feature of this patent; therefore, it will not be described further. An example of the extraction system's layout is as follows:

[0100] (a) After the drilling is completed, use the DN426mm high-concentration extraction pipeline in the roadway to pump.

[0101] (II) Pipeline system flow: 2210 secondary roadway high-concentration DN426mm gas extraction pipeline → centralized return air high-concentration DN720mm gas pipeline → main return air roadway high-concentration DN720mm gas pipeline → surface gas extraction pump station.

[0102] Among them, the gas extraction effect (including parameters such as extraction concentration, extraction mixed flow rate, and extraction pure volume) can intuitively reflect the pressure relief and permeability enhancement effect of high-pressure hydraulic permeability enhancement on the coal body. By statistically analyzing the daily extraction volume and extraction concentration of a single borehole, the ease of gas extraction from the enhanced permeability borehole can be characterized. The specific investigation is as follows:

[0103] Gas extraction effectiveness verification: Based on the original gas content of the coal body and the gas extraction volume, the extraction time to meet the standard is calculated, and then the residual gas content of the coal body is measured. If the residual gas content is less than 8 m3 / t (less than 6 m in the structural zone), the extraction is effective. 3 If the gas extraction rate is / t), then the scheme design is reasonable and can effectively prevent gas outbursts and effectively improve the gas extraction rate.

[0104] As a specific implementation method, the steps for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation also include: after permeability enhancement, calculating the amount of coal dust discharged from each enhanced borehole, sealing the boreholes and performing joint pumping, and installing metering devices in each borehole. Daily measurements of gas concentration, flow rate, negative pressure, and other data are taken from the enhanced boreholes, and the recorded data are statistically analyzed.

[0105] (1) Statistics on hydraulically enhanced chip removal

[0106] To more intuitively compare the exposed coal area in boreholes before and after permeability enhancement, the effect of permeability enhancement on increasing the exposed coal area was indirectly reflected by statistically analyzing the amount of coal chips removed. After conducting high-pressure hydraulic permeability enhancement tests on the test boreholes, the following data was recorded for each borehole: borehole depth / m, azimuth / °, dip angle / °, and amount of coal chips removed / m³. 3 The amount of coal dust discharged during construction.

[0107] This invention employs a novel "directional drilling + hydraulic permeability enhancement" process. Firstly, directional drilling ensures precise positioning, minimizing blind spots in the extraction process. Secondly, hydraulic permeability enhancement increases the overall extraction borehole diameter, ensuring stable extraction output and effectively reducing borehole blockage. Thirdly, hydraulic permeability enhancement improves coal seam permeability, expanding the extraction radius and significantly enhancing extraction efficiency. This technology, combined with kilometer-long directional drilling rig technology, utilizes a flow-controlled high-low pressure conversion mechanism to control the critical high and low pressure states under different flow rates. Low-pressure water is used during normal directional drilling; when permeability enhancement is needed, simply increasing the pump flow achieves high-pressure conversion, with high-pressure water automatically ejected from the alloy nozzle to enhance coal seam permeability. This effectively improves gas extraction efficiency and coverage, reduces drilling volume in the coal seam, and alleviates mine maintenance pressure.

[0108] Example 3

[0109] like Figure 1 As shown, a gas blowout prevention and collection device includes:

[0110] Blowout prevention structure 1 for gas collection orifice;

[0111] The outlet end of the orifice blowout prevention structure 1 is connected to the gas-slag separator 2 for collecting water and drill cuttings in the gas and the inlet end of the first buffer bag 3 for buffering, respectively.

[0112] and

[0113] The outlet end of the first buffer bag 3 is connected to the blowout preventer extraction system pipeline 4 used for gas extraction.

[0114] As a specific implementation, the gas-slag separator 2 includes a first cleaning water head 2-2 installed on the housing 2-1 for spraying water into the housing 2-1 when a small amount of drill cuttings accumulate in the housing 2-1;

[0115] Exhaust pipes 2-4 are used to discharge gas;

[0116] Negative pressure gauge 2-5 used to measure the pressure inside box 2-1;

[0117] Observation window 2-6 is used to observe the amount of drill cuttings inside the housing 2-1;

[0118] And a slag discharge port 2-7 for discharging drill cuttings and water from the housing 2-1.

[0119] The drill cuttings inside the box can be observed through the observation window 2-6. When a small amount of drill cuttings accumulates, the first cleaning water head 2-2 is used to flush the drill cuttings inside the box 2-1 into the box body 2-1 under the action of water force.

[0120] The drill cuttings inside the box can be observed through the observation window 2-6. When a large amount of drill cuttings accumulates, a large amount of water is needed to drain the drill cuttings. In order to increase the water volume, as a specific implementation method, a second cleaning head 2-3 is also provided to spray water into the box 2-1 when a large amount of drill cuttings accumulates inside the box 2-1.

[0121] As a specific implementation, it also includes a plurality of parallel inclined plates 2-8 for draining and discharging slag inside the housing 2-1. In use, when a large amount of drill cuttings accumulates, water is sprayed onto the housing 2-1 by the first slag-cleaning water head 2-2 and the second slag-cleaning water head 2-3. Under the action of water force, the drill cuttings in the housing 2-1 are flushed out of the housing 2-1 under the guidance of the inclined plates 2-8.

[0122] The number of inclined plates 2-8 can be adjusted according to the volume of the box 2-1 and the amount of drill cuttings.

[0123] When the drilling depth exceeds 200m, in order to reduce the excessive gas ejection pressure, a second buffer bag 5 is also included, which is connected to the outlet end of the gas-slag separator 2 for buffering. The outlet end of the second buffer bag 5 is connected to the blowout prevention and extraction system pipeline 4.

[0124] The first buffer bag 4 and the second buffer bag 5 are both 10m long and 1m in diameter, with a retractable rear end. The specific size can be adapted to different application scenarios.

[0125] As a specific implementation, a blowout and backflow prevention drill bit 1-1 and a hole protection structure 1-2 sleeved on the orifice blowout prevention structure 1 are provided. The hole protection structure 1-2 includes a rubber gasket and packing. The specific installation method adopts a conventional method and is not an innovation of this patent, so it will not be described in detail here.

[0126] When drilling stops or when adding drill rods, the blowout and backflow prevention drill bit 1-1 prevents gas and coal slag from entering the drill rod or overflowing through the drill rod; the hole protection structure 1-2 and the drill rod can fit tightly together to prevent gas in the hole from overflowing through the contact gap.

[0127] When drilling stops or drill pipes are added, the gas level in the borehole is very low. If the gas-slag separator 2 is not equipped with a check valve, air will flow into the blowout prevention and extraction system pipeline 4 through the slag outlet, thereby reducing the extraction concentration and affecting the extraction negative pressure. To solve this problem, as a specific implementation, it also includes: a pneumatic valve 2-9 with a check valve function installed on the gas-slag separator 2. In the event of continuous gas ejection from the borehole, in order to ensure that the downhole gas does not exceed the limit, the pneumatic valve 2-9 below the gas-slag separator 2 should be quickly activated to close it and prevent excessive gas ejection.

[0128] When gas is abnormally ejected, it flows into the air-water-slag separator 2 through the blowout prevention structure 1. Due to gravity, the water and drill cuttings sink to the bottom of the tank and are then discharged through the slag discharge port 2-7. The gas is carried away by the normally open negative pressure on the tank body 2-1.

[0129] When a large abnormal gas eruption occurs, some of the gas, water, and slag flow into the gas-water-slag separation box through the blowout prevention structure 1 at the orifice, while some flows into the buffer bag above the blowout prevention structure 1 under the impact of the strong airflow (the buffer bag is normally closed under negative pressure; when the impact pressure is too high, the buffer bag is quickly filled and inflated, connecting with the main negative pressure pipeline, allowing the ejected gas to be quickly extracted). A portion of the gas, water, and slag flowing through the gas-water-slag separation box sinks to the bottom of the box due to gravity, and is then discharged through the slag discharge port. The gas is carried away by the normally open negative pressure on the box body. Based on the above scheme, a second buffer bag 5 is also included, located at the outlet end of the gas-slag separator 2. The outlet end of the second buffer bag 5 is connected to the blowout prevention and extraction system pipeline 4.

[0130] Through the blowout prevention structure 1, a portion of the steam-water-slag flows into the gas-slag separator 2, while another portion, under the impact of the strong airflow, flows into the first buffer bag 3 above the blowout prevention structure 1 (the buffer bag is normally closed under negative pressure; when the impact pressure is too high, the buffer bag is quickly filled and inflated, connecting with the main negative pressure pipeline, and the ejected gas can be quickly drawn away). A portion of the steam-water-slag that flows through the gas-slag separator 2, due to gravity, sinks the water and drill cuttings to the bottom of the tank and is then discharged through the slag discharge port 2-7, while the gas is carried away by the normally open negative pressure on the tank body 2-1.

[0131] Using the method and apparatus of this embodiment, under the condition of ensuring safe production in the mine, high-pressure hydraulic permeability enhancement technology with in-seam drilling is adopted. Through the research and field application of new technologies and processes, on the one hand, the gas extraction efficiency is improved and the amount of drilling work is reduced; on the other hand, the continuous gas output of the coal roadway to be excavated is isolated, eliminating the power source of coal seam outburst, and the overall coal seam and gas are uniformly depressurized, so as to achieve the purpose of rapid excavation of coal roadway with outburst elimination. Combined with the actual field conditions, the hydraulic permeability enhancement process technology is tested on-site. The ZYL-6000D intelligent kilometer directional drilling rig is used. By determining different permeability enhancement flow rates, permeability enhancement pressures, permeability enhancement diameters and permeability enhancement devices, the permeability enhancement effect of the coal seam is improved, the stress of the coal and rock strata is rapidly reduced, the applicability of the series of equipment is improved, and the problems of low extraction efficiency of low-permeability outburst coal seams and poor depressurization effect of stress-dominant coal seams are solved.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation, characterized in that, Includes the following steps: 1) Drill hole arrangement: Select the spacing, row spacing, angle, diameter and length of the drill holes according to the occurrence of the coal seam to be pumped and the pumping radius; 2) Drilling and sealing: Determine the angle and orientation of the kilometer directional drilling rig, fix the kilometer directional drilling rig, and seal the hole after drilling is completed; Step 2) Drilling and Sealing: Determining the angle and orientation of the kilometer-long directional drilling rig, fixing the kilometer-long directional drilling rig, and sealing the hole after drilling are completed, specifically includes: Select a Φ120mm drill bit and directional drill rod to perform rotary drilling for hole opening; Select a Φ165mm reaming drill bit and reaming drill rod and use rotary drilling to perform the first reaming operation; Select a Φ194mm reaming drill bit and reaming drill rod and use rotary drilling to perform the second reaming; A lower sealing pipe is installed inside the borehole. The lower sealing pipe is grouted using a two-plug-one-injection bag-type pressurized grouting sealing process. The pressure shall not be lower than 1.5 MPa. 3) Directional drilling and blowout gas extraction: After the borehole is sealed, a kilometer-long directional drilling rig is used and the first drilling tool is used to drill directionally to the final hole position, and then the drill rod is pulled out. Install a gas blowout prevention and collection device on the borehole to carry out blowout prevention and extraction during directional drilling. The gas blowout prevention and collection device in step 3) includes: Blowout prevention structure for collecting gas (1); The outlet end of the orifice blowout prevention structure (1) is connected to the inlet end of the gas-slag separator (2) for collecting water and drill cuttings in the gas and the first buffer bag (3) for buffering, respectively. and The outlet end of the first buffer bag (3) is connected to the blowout prevention extraction system pipeline (4) for gas extraction; 4) Hydraulic permeability enhancement: A second drilling tool is used to drill to the bottom of the hole, and a backward drilling method is used to enhance permeability and create a cavity. The diameter of the borehole is increased by hydraulic permeability enhancement. The first drilling tool includes a Φ120mm drill bit, a Φ73 guiding system, and a Φ73mm cable-connected high-pressure sealed triangular spiral groove directional drill rod; The second drilling tool includes a Φ120mm drill bit, a water jet, and a Φ73mm cable-carrying high-pressure sealed triangular spiral groove directional drill rod; Step 4) involves using a second drill bit to drill to the bottom of the hole, employing a retraction method to enhance permeability and create a cavity, and increasing the borehole diameter through hydraulic permeability enhancement. This step specifically includes: Fixed-point cavity creation: During the permeability enhancement process, the flow rate and water pressure are adjusted at any time according to the permeability enhancement effect. The spacing between each point is 10m from the inside to the outside. Adjacent boreholes are created using a staggered permeability enhancement cavity creation method until the borehole opening. Each borehole creates 28 cavity segments, ultimately forming a permeability enhancement cavity segment with a length of 1m and a diameter of 800mm. The amount of slag coal returned in each cavity segment is not less than 0.7t, and the pump pressure is not less than 15MPa during permeability enhancement. By increasing the permeability of the coal seam, the entire coal seam expands, thereby relieving pressure and eliminating outbursts. 5) Gas extraction: After drilling is completed, the boreholes are connected to the extraction system for extraction.

2. The method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation according to claim 1, characterized in that, Step 3) Directional drilling and blowout gas extraction: After the borehole is sealed, a kilometer-long directional drilling rig is used, and the first drilling tool is used to drill directionally to the final hole position. Then, the drill rod is pulled out. The specific steps include: The drill was drilled to the designed depth using a kilometer-long directional drilling rig. After the drill rod was pulled out and replaced with a water jet, the drill was sent to the bottom of the hole.

3. The method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation according to claim 1, characterized in that, Also includes: After the permeability enhancement is completed, the amount of coal dust discharged from each enhanced permeability borehole is counted, and the borehole is sealed and pumped out. A metering device is installed in each borehole. The gas concentration, flow rate, and negative pressure data of the permeability enhancement orifice are measured once a day, and the recorded data are statistically analyzed.

4. The method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation according to claim 1, characterized in that, The gas-slag separator (2) includes a first cleaning head (2-2) installed on the housing (2-1) for spraying water into the housing (2-1) when a small amount of drill cuttings accumulate in the housing (2-1). Exhaust pipes (2-4) used to discharge gas. Negative pressure gauge (2-5) used to measure the pressure inside the chamber (2-1); The observation window (2-6) is used to observe the amount of drill cuttings inside the housing (2-1); And a slag outlet (2-7) for discharging drill cuttings and water from the housing (2-1).

5. The method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation according to claim 4, characterized in that, The gas-slag separator (2) also includes a second cleaning head (2-3) for spraying water into the housing (2-1) when a large amount of drill cuttings accumulate in the housing (2-1).

6. The method for increasing coal seam permeability based on kilometer-long directional drilling and hydraulic perforation according to claim 1, characterized in that, When the drilling depth exceeds 200m, the gas blowout prevention and collection device further includes: A second buffer bag (5) for buffering is connected to the outlet end of the gas-sludge separator (2); The outlet end of the second buffer bag (5) is connected to the blowout prevention and extraction system pipeline (4).

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