Through-layer drilling and extraction drilling tool and anti-blowout hole gas extraction while drilling method

Abstract

The present invention discloses a through-layer drilling extraction drilling tool and a blowout prevention hole while drilling gas extraction method, the extraction drilling tool comprises a plurality of extraction drill rods, an extraction high-low pressure conversion valve, a sieve hole air intake device, an open-close drill bit, and an extraction water braid; the extraction drill rod is composed of an outer tube and an inner tube, the extraction high-low pressure conversion valve is composed of a valve outer tube, a valve inner tube and a high-low pressure conversion assembly, the sieve hole air intake device is composed of a convex rib-shaped outer tube, a convex rib-shaped inner tube and an air intake sieve hole plate, inner tubes with different names are sealed and connected with each other to form a gas extraction channel of the drilling tool, the axial space between the inner tube with the same name and the outer tube with the same name is the flow supply channel of the drilling tool, the space between the outer surface of the drilling tool and the borehole wall is the slag discharge channel, the extraction drilling tool is equipped with a controlled-spray drainage box at the orifice, the blowout prevention hole while drilling gas extraction method in this patent is aimed at forward slitting and punching, and the hole protection screen tube needs to be lowered when withdrawing the drill.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine gas extraction drilling, and specifically to the technical field of drilling, slitting and punching of through-layer drilling holes in protruding coal seams. Aiming at the problem of gas exceeding the limit in the blowholes during the slitting, punching and drilling withdrawal operations of through-layer drilling holes in protruding coal seams, the present invention proposes a through-layer drilling extraction drilling tool and a blowout-prevention hole while-drilling gas extraction method, which, on the one hand, helps to prevent accidents of gas exceeding the limit in the through-layer drilling blowholes, and on the other hand, provides support for lowering a hole protection screen pipe before drilling withdrawal. Background Art

[0002] The main measures for gas extraction and control of protruding coal seams are to construct through-layer drilling holes in the bottom rock tunnel of the protruding coal seam, and to implement gas extraction in the areas to be excavated or mined in the protruding coal seam to eliminate the protrusion and achieve extraction standards. In order to give full play to the extraction and elimination of protrusion by through-layer drilling holes, hydraulic permeability enhancement operations such as "cutting" or "punching" are generally carried out in the coal hole section of the through-layer drilling holes. The current state of the art is that the drill rods used are generally grooved drill rods, rib drill rods, triangular grooved drill rods or triangular drill rods, etc. Among them, the original applicant of the patents of the first three types of drill rods is the present applicant, namely Henan Polytechnic University, and the patent numbers are ZL200610111830.7, ZL200920088879.4, and ZL200910064973.0, respectively. A high-low pressure conversion device with a high-pressure water jet nozzle is installed between these drill rods and the drill bit. The inner hole of the drill rod is a flow supply channel, and the coal hole section is cut or punched. Some scholars also call it hydraulic cutting, hydraulic cavitation, hydraulic grooving, hydraulic coal digging, etc. Since the drill rod used is a single-tube structure, after the high-low pressure conversion device is set, the function of lowering the hole protection screen when withdrawing the drill is lost. For extremely soft coal seams, there is no need for a high-low pressure conversion device. A water jet nozzle for punching can be directly installed on the drill head. Once the drill bit enters the coal seam, punching and drilling will be carried out simultaneously or at intervals. Also, since the drill rods used are all single-tube structures, after the water jet nozzle is installed on the drill head, the function of lowering the hole protection screen when withdrawing the drill is also lost.

[0003] When drilling through the layers, cutting or punching holes, high-pressure water is used as the drill bit cooling, jet power and slag removal power. The slag removal channel is located between the outer wall of the drill pipe and the inner wall of the borehole, which is called the external slag removal channel. In the process of cutting or punching in the coal hole section during the drilling of protruding coal seams, a large amount of water coal slag and gas will be generated. The coal and gas outbursts and coal cannons often occur in the coal hole section. The output of coal slag is extremely uneven, and the particle size of coal slag is also uneven. The coal slag itself does not have fluidity. It is necessary to use the water flow and the rotary stirring and slag crushing effect of the drill pipe to transform these coal slags into a flowing solid-liquid water coal slag fluid and discharge it out of the hole through the external slag removal channel of the borehole. Since the amount of coal slag produced by cutting or punching the coal hole section is sudden and unbalanced, the coal slag flows to the slag discharge channel outside the narrow rock hole section under the action of self-weight and water flow. The water flow and the rotary stirring of the drill pipe cannot timely transform these coal slag into a flowable solid-liquid phase water coal slag body, which often leads to non-permeable blockage of the slag discharge channel outside the rock hole section, that is, the water coal slag occupies 100% of the cross section of the slag discharge channel, the water coal slag leaks down, and the gas is retained in the loose coal body and caves formed by the cutting or punching, and the gas is constantly Desorption will cause the gas pressure in the loose coal body and caves in the coal hole section to be much greater than the atmospheric pressure outside the hole. Under the action of water flow and rotary stirring of the drill rod, once the non-permeable blocked external slag channel of the rock hole section is unblocked, high-pressure gas and water-coal slag will be ejected from the hole mouth in large quantities, and even form continuous and long-term spray holes. Such spray holes often lead to excessive gas in tunnels and excessive gas in through-layer drilling spray holes, accounting for 30% to 80% of the total number of excessive gas accidents in protruding mines, and have become an important safety hazard in protruding mines.

[0004] When drilling through the existing protruding coal seams, a blowout prevention device is generally installed at the hole mouth. The blowout prevention device is generally composed of a collection box, an air extraction pipe, and a water-coal slag discharge pipe to prevent the gas generated by the blowout hole from spreading to the tunnel space. When the blowout is serious, the blowout prevention device will fail, resulting in excessive gas concentration in the tunnel at the drilling site. Many patents have been applied for gas extraction drilling blowout prevention technology. According to the specific underground environment, a variety of hole mouth blowout prevention devices have been designed according to local conditions. For example, the patents related to blowout prevention holes applied for in 2021 alone include: blowout prevention hole device and system (CN202120284095X); a gas control dust prevention and blowout prevention hole device (CN202120183981.3); a coal mine drilling blowout prevention hole dust removal device (CN202120116187.7); a semi-open blowout prevention hole assembly and gas control, collection and emission device (CN202120080173.4); a gas extraction system An automatic blowout prevention hole device (CN202120006760.9); an underground hydraulic punching blowout prevention hole and coal quantity metering device in a coal mine (CN202121828212.0); a gas control blowout prevention hole device (CN202121728316.4); a gas control blowout prevention hole device (CN202121249379.1); an easy-to-install gas control blowout prevention hole device (CN202120004386.9). The basic starting point of these anti-blowout hole technology patents is similar, that is, to collect and separate the water coal ash and gas sprayed from the borehole outside the hole, the gas enters the exhaust pipe, the water coal ash enters the water coal ash discharge pipe or further enters the water coal ash gas separation box, and the gas is prevented from pouring into the tunnel space as much as possible. If there is an abnormal gas zone, coal and gas protrusion in the hole, etc., when the blowout hole is serious, these anti-blowout devices will crack due to insufficient collection box volume, insufficient extraction speed of the exhaust pipe and disconnection or collapse, insufficient volume of the buffer air bag and burst, etc., which will still lead to gas over-limit accidents of the blowout hole. In terms of strict causality, the current anti-blowout hole device cannot prevent the occurrence of the blowout hole phenomenon, but is used to prevent gas over-limit accidents during the blowout hole.

[0005] A large number of engineering practices of drilling, cutting or punching holes in protruding coal seams show that the current passive anti-blowout method cannot fundamentally solve the problem of gas exceeding the limit of blowout holes. To solve the problem of gas exceeding the limit of blowout holes, the gas power source that induces blowout holes should be eliminated from the source. The gas power source of the blowout hole is located in the loose coal body formed by the cutting or punching of the coal hole section and in the cave formed by the cutting and punching. The loose coal body and the cave contain a large amount of free gas. For the convenience of subsequent description, it is referred to as "loose cave gas bag". There are solid (coal slag), liquid (water) and gas (gas) inside it at the same time. The gas is at a high position and the water coal slag is at a lower position. The gas is the gas power source for the blowout hole. Cutting or punching holes can relieve the pressure of coal body in a large range, and coal body will continuously desorb a large amount of gas. When coal and gas in the hole burst, a large amount of coal slag and gas will suddenly be produced. The range of "Songdong gas bag" will expand, and the gas volume and gas pressure inside it will increase, accumulating a large amount of gas energy for the occurrence of spray holes. In the inclined annular external slag discharge channel of the through-layer drilling hole, the solid, liquid and gas three-phase separation medium cannot be mixed evenly and cannot be moved synchronously. Solids and liquids can use their own weight to move to the external slag discharge channel of the rock hole section, and gas can be discharged from the gap of the external slag discharge channel by pressure difference. Only when the sum of the volume of solids and liquids cannot fill the external slag discharge channel 100%, the gas has the opportunity to discharge downward by pressure difference. The actual situation on site is: the external slag discharge channel is continuously filled with water coal slag, gas cannot be discharged downward in time, and the gas pressure in the "Songdong gas bag" continues to increase, thereby accumulating gas power source for the occurrence of spray holes. Based on the above background technology analysis, the applicant proposed the idea of ​​discharging water-coal slag and gas separately for the "Songdong Gas Bag" which is an implicit power source for the blowholes. That is, through the design of the drill bit, the water-coal slag is made to flow through the external slag discharge channel between the surface of the drill bit and the borehole wall, and the gas in the "Songdong Gas Bag" is made to flow through the gas extraction channel in the center of the drill bit. An extraction drill bit with drilling function, slitting and punching function, gas extraction while drilling function and drill withdrawal and lowering of the hole protection screen pipe function is designed. The extraction drill bit is used to implement gas extraction while drilling, so as to eliminate the gas power source that induces the blowholes from the source. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a through-layer drilling extraction drill tool and a matching anti-blowout hole gas extraction method while drilling, and uses the extraction drill tool to implement gas extraction while drilling, solves the blowout hole phenomenon and the gas over-limit accident of the blowout hole during the water jet cutting or punching process of the through-layer drilling, improves the safety of the hydraulic permeability enhancement operation of the through-layer drilling, and at the same time uses the gas extraction channel of the drill tool as a channel for lowering the hole protection screen when withdrawing the drill.

[0007] The technical solutions adopted to achieve the above objectives are:

[0008] The through-layer drilling extraction drilling tool includes an extraction water braid, multiple extraction drill rods, an extraction high-low pressure conversion valve, a screen hole air intake device and an open-close drill bit connected in sequence; a controlled spray drainage box installed in conjunction with the extraction drill rod is provided at the orifice. A gas extraction channel is constructed in the central part of the inner cavity of the through-layer drilling extraction drilling tool, and a flow supply channel of the drilling tool is constructed between the outer tube and the inner tube of the extraction drill rod of the through-layer drilling extraction drilling tool. The gas in the "Songdong gas bag" goes through the gas extraction channel, and the water coal slag in the "Songdong gas bag" goes through the external slag discharge channel. By extracting the gas in the "Songdong gas bag" while drilling, the gas power source that induces the spray hole is eliminated in time, and the gas extraction channel is used as a channel for lowering the hole protection screen when withdrawing the drill.

[0009] Furthermore, the extraction drill pipe includes an outer tube and an inner tube that are inserted and matched. The outer tube is protruded from the inner hole of the outer tube by local hot extrusion along the length direction to form two groups of local arc surface protrusions. The local arc surface protrusions match the outer circle of the inner tube, and support and install the inner tube so that the outer tube and the inner tube remain coaxial. The number of each group of local arc surface protrusions is two or three evenly distributed along the circumference of the inner hole of the outer tube. The outer surface shape of the outer tube is spiral groove-shaped or spiral rib-shaped or triangular-shaped or quadrangular-shaped or triangular-shaped or quadrangular-shaped grooves to increase the slag crushing, stirring and conveying capacity of the drill pipe; the axial space between the outer tube and the inner tube is the flow supply channel of the extraction drill, the center hole of the inner tube is the gas extraction channel, and the annular gap between the outer tube and the borehole wall is the slag discharge channel.

[0010] Furthermore, the extraction drill pipe comprises an outer tube, an inner tube and two groups of arc-surface support blocks brazed on the inner wall of the outer tube. The extraction drill pipe comprises an outer tube, an inner tube and two groups of arc-surface support blocks welded on the inner wall of the outer tube. Each group of support blocks is evenly distributed with two or three along the circumference of the inner hole of the outer tube. The support blocks are provided with support block welding holes welded to the inner tube, and the outer tube is provided with outer tube welding holes welded to the support blocks. The radius of the outer arc surface of the support block is equal to the radius of the inner hole of the outer tube, and the radius of the inner arc surface of the support block is equal to the radius of the outer circle of the inner tube. The outer surface shape of the outer tube is spiral groove-shaped or spiral rib-shaped or triangular-shaped or quadrangular-shaped or triangular-shaped or quadrangular-shaped to increase the slag crushing, stirring and conveying capacity of the drill pipe. The axial space between the outer tube and the inner tube is the flow supply channel of the extraction drill, the center hole of the inner tube is the gas extraction channel, and the annular gap between the outer tube and the borehole wall is the slag discharge channel.

[0011] Furthermore, the extraction drill pipe includes an outer tube and an inner tube, the outer tube is a special-shaped outer tube, the outer surface of the special-shaped outer tube is provided with an axial groove, the inner hole of the special-shaped outer tube is provided with an axial arc-surface protrusion corresponding to the axial groove, the axial arc-surface protrusion of the inner hole of the special-shaped outer tube is installed in cooperation with the outer circle of the inner tube, and supports the inner tube so that the outer tube and the inner tube remain coaxial, the number of axial grooves and axial arc-surface protrusions is evenly distributed as two or three around the circumference, and spiral grooves or spiral ribs are provided on the outer surface of the outer tube to increase the slag crushing, stirring and conveying capacity of the drill pipe; the axial space between the outer tube and the inner tube is the flow supply channel of the extraction drill bit, the center hole of the inner tube is the gas extraction channel, and the annular gap between the outer tube and the borehole wall is the slag discharge channel.

[0012] Furthermore, the extraction drill pipe includes an outer tube and an inner tube that are inserted into each other. The outer tube is a hot-twisted special-shaped outer tube formed by a hot-twisting method under a constrained state. The outer surface of the hot-twisted special-shaped outer tube forms a large spiral groove, and the inner hole of the hot-twisted special-shaped outer tube forms a large-pitch arc-surface protrusion corresponding to the large spiral groove. The large-pitch arc-surface protrusion of the inner hole of the hot-twisted special-shaped outer tube is installed in cooperation with the outer circle of the inner tube, and supports the inner tube so that the outer tube and the inner tube remain coaxial. The number of large spiral grooves and large-pitch arc-surface protrusions is two or three; the axial space between the outer tube and the inner tube is a flow supply channel for the extraction drill, the center hole of the inner tube is a gas extraction channel, and the annular gap between the outer tube and the borehole wall is a slag discharge channel.

[0013] Furthermore, the extraction drill pipe can also be composed of an outer tube, an inner tube and a support, and the support is installed between the outer tube and the inner tube, and the support keeps the outer tube and the inner tube coaxial. The outer surface shape of the outer tube can be spiral groove, spiral rib, triangular or triangular groove, and the number of grooves or ribs is set to two or more; the groove can be a rectangular groove, a trapezoidal groove, an arc groove, or a rifle linear groove; the rib can be a welded rib, a machined rib, or a wear-resistant clad rib, and the rib surface can be a flat rib or an arc rib. The shape of the rib is not limited, and the width of the rib is equal to or greater than the height of the rib. The grooves, ribs, arc edges, etc. set on the outer surface of the outer tube have the function of increasing the slag crushing function, stirring function and conveying function of the outer tube. There are many types of double-wall drill rods used in the fields of soft formation drilling, coal seam gas content fixed-point sampling, oil drilling, etc. Similar double-wall drill rods, when used in conjunction with the extraction-type high- and low-pressure conversion valve, sieve hole air intake device, etc. included in the present invention, are also within the protection scope of the present invention.

[0014] Furthermore, the end of the outer tube is transformed into a thick-walled circular outer tube by extrusion molding or friction welding joint method, and male buckles and female buckles are arranged at both ends of the thick-walled circular outer tube. Adjacent outer tubes are connected by sealed threaded connections, and adjacent inner tubes are connected by lap seals or plug seals.

[0015] Further, the extraction type high-low pressure conversion valve comprises a valve outer tube, a valve inner tube and a high-low pressure conversion assembly, the valve outer tube and the valve inner tube are coaxially mounted, and the high-low pressure conversion assembly is mounted in a flow supply channel formed between the valve outer tube and the valve inner tube;

[0016] The central hole of the valve inner tube is a gas extraction channel; the two ends of the valve outer tube are respectively provided with a male buckle and a female buckle, the female buckle of the valve outer tube is connected to the male buckle of the extraction drill pipe, and the male buckle of the valve outer tube is connected to the female buckle of the sieve hole air intake device, one end of the valve inner tube is sealed with the inner tube of the extraction drill pipe, and the other end of the valve inner tube is sealed with the rib-shaped inner tube of the sieve hole air intake device, and a sealing member is provided at one end of the valve inner tube.

[0017] Furthermore, the outer surface of the valve outer tube is provided with two to four axial ribs or spiral ribs whose two ends gradually become inclined surfaces, and a cutting blade is provided on the side of the inclined surface; radial water jet nozzles or oblique water jet nozzles are provided on the two axial ribs or two spiral ribs of the valve outer tube; intermittent spiral grooves are provided on the axial ribs or spiral ribs of the valve outer tube, and the intermittent spiral grooves enable the valve outer tube to have slag crushing, stirring and conveying functions.

[0018] Furthermore, the jet nozzle of the extraction-type high-low pressure conversion valve can be replaced. When a small-diameter nozzle is used, hydraulic slitting of medium-hard coal can be achieved, and when a large-diameter nozzle is used, hydraulic punching of soft coal seams can be achieved. Two groups of nozzles can also be set on the convex rib of the valve body, one group is two radial slitting nozzles, and the other group is two radial or oblique punching nozzles. The above-mentioned three-station high-low pressure conversion assembly is designed as a four-station high-low pressure conversion assembly, namely the locking station, low-pressure drilling station, medium-pressure punching station and high-pressure slitting station, which is also within the protection scope of the present invention. However, due to the influence of the medium pressure in the hole outside the valve outer tube, the switching accuracy between the punching station and the slitting station will be reduced, the difficulty of spring selection will increase, and the reliability will be reduced. If the extraction-type high-low pressure conversion valve is designed with four stations, it is also within the protection scope of the present invention.

[0019] Furthermore, the high-low pressure conversion assembly includes a sliding valve core, a spring, a front support, a rear support and a fixing pin; a sliding valve core is installed between the front support and the rear support, a spring is installed between the sliding valve core and the valve inner tube, and the front support and the rear support are connected to the valve outer tube through a fixing pin; when working, both ends of the spring are in contact and cooperate with the sliding valve core and the rear support.

[0020] Furthermore, the sliding valve core has three working positions: one is the stop-drilling locking position, which prevents the water-coal slag in the hole from flowing back to the flow supply channel of the extraction drill pipe when drilling is stopped such as loading and unloading the drill pipe; the second is the low-pressure drilling position, where all low-pressure fluids are supplied to the open-and-close drill bit; the third is the water jet slitting or punching position, where high-pressure fluids are supplied to the jet nozzle, and a small amount of fluid is supplied to the open-and-close drill bit through leakage or micro-pore leakage to cool the drill bit. There are many ways to supply a small amount of water flow to the open-and-close drill bit under high pressure. Generally, engineers can make slight changes to the sliding valve core and the support as needed, which is also within the protection scope of the present invention.

[0021] Further, the sieve hole air intake device comprises a convex rib-shaped outer tube, a convex rib-shaped inner tube and an air intake sieve hole plate, the convex rib-shaped outer tube and the convex rib-shaped inner tube are coaxially mounted, preferably, the convex rib-shaped inner tube is embedded in the convex rib-shaped outer tube, and the convex rib-shaped inner tube and the convex rib-shaped outer tube are integrated by a method combining impregnation sealing and fixing pins, the space between the convex rib-shaped outer tube and the convex rib-shaped inner tube is a flow supply channel, and the inner hole of the convex rib-shaped inner tube is a gas extraction channel; male buckles and female buckles are respectively provided at both ends of the convex rib-shaped outer tube, and a seal is installed at one end of the convex rib-shaped inner tube;

[0022] The ribs of the rib-shaped outer tube and the rib-shaped inner tube are configured as axial ribs or spiral ribs, and the number of ribs of the rib-shaped outer tube and the rib-shaped inner tube is two, three or four; radial air intake holes penetrating the inner and outer ribs are configured on the ribs of the rib-shaped outer tube and the rib-shaped inner tube, and the air intake sieve plate is welded on the ribs of the rib-shaped outer tube and covers the radial air intake holes.

[0023] Furthermore, the air inlet sieve plate is provided with inverted cone-shaped sieve holes, the air inlet diameter of the sieve holes is one-half to one-fifth of the diameter of the radial air inlet through hole, and the sum of the air inlet areas of all the sieve holes is larger than the inner hole cross-sectional area of ​​the convex rib-shaped inner tube.

[0024] Furthermore, the ribs on the rib-shaped outer tube are removed, or the rib-shaped outer tube is changed into a groove-shaped outer tube, and the radial through holes are arranged in the grooves of the groove-shaped outer tube. This change will not only further increase the amount of coal slag in the gas extraction channel, but also increase the amount of water entering the gas extraction channel. The air intake function is weakened, but the air intake function is still available. This change is also within the protection scope of the present invention.

[0025] Furthermore, the open-and-close drill bit includes a drill bit body, a short-section inner tube and an opening cover; a short-section inner tube is coaxially installed in the drill bit body; a female buckle that cooperates with a convex rib-shaped outer tube is provided at one end of the drill bit body; an end tooth is installed at the outer edge of the other end of the drill bit body, and an opening cover covering the short-section inner tube is installed at the center of the other end of the drill bit body; two pairs of pin holes are provided on the opening cover, one pair of pin holes is installed with a high-strength pin shaft, and the other pair of pin holes is installed with a low-strength shear pin. In the actual implementation process, there are many ways to open the opening cover. Generally, mechanical engineers can make selective designs according to the double-channel structure and geometric space of the open-and-close drill bit with a short-section inner tube, such as a shear pin type opening cover, a self-locking bevel type opening cover and a hinged hinge type opening cover. If these changes are used in conjunction with the components of the present invention, they are also within the protection scope of the present invention.

[0026] Furthermore, the extraction type water braid includes a hollow water braid outer body, an extraction pipe, a pressure gauge, an extraction switch and a flow supply port. The inner cavity of the hollow water braid outer body is hollow and is equipped with a hollow water braid inner tube. The inner hole of the hollow water braid inner tube is a gas extraction channel. One end of the hollow water braid outer body is connected to the outer tube of the extraction type drill pipe by a thread. The other end of the hollow water braid outer body is equipped with an extraction pipe connected to the hollow water braid inner tube. The other end of the hollow water braid inner tube is connected to the inner tube of the extraction type drill pipe by a thread. A pressure gauge and an extraction switch are installed on the extraction pipe. The pressure gauge displays the gas pressure in the inner cavity of the drill tool and the gas pressure in the "Songdong gas bag" during the gas extraction while drilling. The gas pressure in the "Songdong gas bag" can also be understood by turning off the switch. According to the gas pressure in the inner cavity of the drill tool and the gas pressure in the "Songdong gas bag", the slitting or punching operation method is adjusted, and necessary auxiliary control measures are taken.

[0027] Furthermore, other combinations of through-layer drilling and extraction drilling tools are described as follows: the sieve hole air intake device can be designed and processed into an integral whole with the open and close drill bit, the extraction type high and low pressure conversion valve can be processed into an integral whole with the sieve hole air intake device, which can also realize the anti-blowout function of the extraction drilling tool and the function of lowering the hole protection screen pipe before lifting the drill, which is also within the protection scope of the present invention.

[0028] Furthermore, to realize the anti-blowout function of the through-layer drilling and extraction drilling tool, it is necessary to use a control-blowout drainage box at the hole mouth, the control-blowout drainage box includes a hole sealer, a drainage box, a gas drainage pipe, a water coal ash drainage pipe, a dust-proof brush and a control-blowout plug installed in the drainage box; during installation, the control-blowout drainage box is installed at the hole mouth through the hole sealer;

[0029] A hole sealer is provided at one end of the drainage box, a dust-proof brush is provided inside the other end of the drainage box, a gas drainage pipe is provided at the upper part of the drainage box, and a water-coal slag drainage pipe is provided at the lower part of the drainage box; two symmetrical spray control plug plates are installed at one end of the hole sealer in the drainage box, and the cross-sectional area of ​​the slag inlet channel in the drainage box is controlled by moving the position of the plug plates. When coal and gas protrusion occurs in the coal hole section, compulsory spray prevention and spray control are implemented. During operation, the position of the plug plates is manually moved to reduce the cross-sectional area of ​​the slag discharge channel in the drainage box. A plurality of circular holes are provided on the spray control plug plate, and the diameter of the circular holes is equivalent to the annular gap width of the slag discharge channel in the drainage box.

[0030] Furthermore, when the inclination angle of the drilling hole is small, the sieve hole air intake device is easily submerged by water coal slag and affects the radial air intake function. An extraction type drill rod can be installed between the extraction type high and low pressure conversion valve and the sieve hole air intake device to increase the height difference between the sieve hole air intake device and the extraction type high and low pressure conversion valve to avoid the sieve hole air intake device being submerged by water and weakening the air intake function.

[0031] Furthermore, when drilling in extremely soft and protruding coal seams that are difficult to drill, the extraction high-low pressure conversion valve is removed, and 2 to 4 oblique punching water jet nozzles are installed on the open-close drill head. The outlet direction of the water jet nozzle forms an angle of about 45 degrees with the drilling direction, and drilling and punching are carried out simultaneously in the coal hole section. Although this method of gas extraction while drilling will cause a small amount of water in the gas extraction channel, when the drilling and punching speed is slow, the screen hole air intake device will be suspended in the punching hole, and the water inflow into the gas extraction channel can be controlled by the punching progress.

[0032] Furthermore, when drilling in a medium-hard protruding coal seam that is easy to drill, the screen hole air intake device is removed, and no slitting or punching and gas extraction while drilling are performed during the drilling of the coal hole section. Conventional drilling is performed in the coal hole section. After the drill bit enters the coal seam roof, the hole protection screen pipe is lowered, and slitting or punching and gas extraction while drilling are performed during the drilling withdrawal. The hole protection screen pipe is used to perform gas extraction while drilling during the drilling withdrawal slitting or punching. This simplified processing method is suitable for medium-hard coal seams in non-protruding areas of protruding coal seams. If coal and gas protrusion occurs in the hole during the drilling withdrawal slitting or punching process, the hole protection screen pipe may be damaged. After the hole protection screen pipe is damaged, it will be difficult to perform gas extraction while drilling.

[0033] Furthermore, the gas extraction while drilling method for preventing blowout holes using the through-layer drilling extraction drilling tool can adopt the gas extraction while drilling method of forward slitting and punching, or the gas extraction while drilling method of backward slitting and punching. Here, the gas extraction while drilling method of preventing blowout is described by taking the forward slitting and punching as an example. When the forward slitting and punching are used, the following steps are included:

[0034] Step 1: Preparation

[0035] The hole is enlarged, a controlled-spray drainage box is installed at the hole mouth, the extraction pipe on the extraction water braid is removed, the extraction pipe is connected to the existing slag discharger through a retractable hose, and the slag discharger is connected to the extraction pipe network.

[0036] Because no gas is generated during the drilling of the rock hole section, gas extraction while drilling is not required. Removing the extraction pipe (including pressure gauge) at the tail of the extraction water braid can reduce the labor intensity of workers loading and unloading the water braid. A light extraction water braid dedicated to the rock hole section can also be designed, because the rock hole section does not require high-pressure water, and the extraction water braid can be processed more lightly.

[0037] The second step is drilling the rock hole section

[0038] The rock hole section drilling does not implement gas extraction while drilling. Similar to the current drilling, static water of about 3MPa is supplied to the extraction water braid to implement rock hole section drilling. For a mine with a depth of 300m, the pressure of static water is about 3Mpa. The actual use pressure is controlled by flow rate. Using static water can save power consumption of the pump station.

[0039] Step 3: Preparation before slitting and punching

[0040] Once the borehole enters the coal seam, first install the extraction pipe at the tail of the extraction water braid, turn on the high-pressure pump station used for cutting and punching, and connect the relevant pipelines of the controlled spray drainage box.

[0041] Step 4: Gas extraction while drilling through blowout prevention holes

[0042] The forward slotting and punching process is similar to the current forward slotting and punching process. The through-layer drilling extraction drill tool acts as a "extraction pipe" that rotates and moves while drilling, and the sieve hole air intake device acts as a "sieve hole pipe" that rotates and moves while drilling. The gas in the "loose hole gas bag" formed by the slotting and punching is extracted while drilling. During the gas extraction while drilling, the drilling worker observes the pressure gauge on the extraction water braid. The pressure gauge shows the gas pressure in the inner cavity of the drill tool during the gas extraction while drilling. Three situations will occur during the gas extraction while drilling of the forward slotting and punching:

[0043] Case I: Under normal circumstances, the gas pressure in the inner cavity of the through-layer drilling and extraction drilling tool is under negative pressure, and normal water jet cutting or punching operations and drill rod installation are carried out to implement gas extraction while drilling for the gas in the "songdong gas bag". Other external manifestations of normal conditions are: the slag discharge of the controlled spray drainage box is normal, the water coal slag is discharged normally, and a small amount of gas is discharged. If air is found to enter the borehole from the controlled spray drainage box, it means that the extraction is in transition, and the switch on the extraction water braid can be appropriately turned off.

[0044] Case II: Abnormal situation. When the gas pressure in the inner cavity of the through-layer drilling extraction drill is at positive pressure or high pressure, reduce the flow rate of the through-layer drilling extraction drill, reduce the rotation speed of the through-layer drilling extraction drill, stop the forward and backward movement of the through-layer drilling extraction drill, and suspend the installation of the drill rod. When the gas pressure in the inner cavity of the through-layer drilling extraction drill drops to negative pressure or normal pressure, perform normal cutting or punching operations and install drill rods to extract gas from the "Songdong gas bag" while drilling. Other external manifestations of abnormal situations are: intermittent impact sound of the controlled-spray drainage box, intermittent blockage of the borehole, and abnormal discharge of coal ash.

[0045] Case III: Coal and gas outburst in the hole. When dynamic phenomena such as coal and gas outburst in the hole occur, the gas pressure in the inner cavity of the through-layer drilling extraction drill will rise sharply to positive pressure. In this case, the controlled spraying operations are: 1. Reduce the flow rate of the through-layer drilling extraction drill, reduce the rotation speed of the through-layer drilling extraction drill, and strictly prohibit the forward and backward movement of the through-layer drilling extraction drill; 2. Properly control the opening degree of the switch of the extraction pipe of the extraction water braid to prevent the retractable hose and the slag discharger from being destroyed and causing gas to exceed the limit; 3. Move the position of the controlled spray plug in the controlled spray drainage box to prevent the orifice from spraying and causing gas to exceed the limit. Take the above measures, and when the gas pressure in the inner cavity of the through-layer drilling extraction drill is reduced to negative pressure or normal pressure, resume normal slitting or punching operations and drill rod installation, and implement drilling-while-drilling gas extraction for the gas in the "Songdong Gas Bag";

[0046] Step 5: Lower the hole screen before drilling back out

[0047] When the slitting and punching operation advances to the roof of the coal seam or the drill bit enters the roof of the coal seam, the extraction pipe and pressure gauge at the tail of the extraction water braid are removed, and the hole protection screen is lowered before drilling back. The hole protection screen with barbs is placed on the top of the coal hole section through the inner hole of the extraction water braid, the inner tube of the extraction drill pipe, the valve inner tube, the rib-shaped inner tube, the short section inner tube of the open and close drill bit, and the open cover; after the hole protection screen is lowered, the extraction pipe and pressure gauge of the extraction water braid are reinstalled, and drilling and gas extraction while drilling begins.

[0048] Step 6: Drilling and gas extraction while drilling

[0049] During the process of drilling back, the normal extraction of the extraction water braid is maintained, and repeated operations of backward cutting or punching are carried out as needed. The gas extraction while drilling is to replace the air intake function of the screen hole air intake device with the inserted hole protection screen pipe, and the gas on the top of the "pine hole gas bag" is extracted while drilling. The gas pressure in the inner cavity of the through-layer drilling extraction drill bit is kept in a negative pressure or normal pressure state to avoid blowouts during the drilling back process.

[0050] Other notes on the gas extraction while drilling method:

[0051] For the extraction drilling tool of the present invention, the gas extraction while drilling method using forward slitting and punching is the best gas extraction while drilling method. In addition, there is also a backward slitting and punching gas extraction while drilling method. The backward slitting and punching gas extraction while drilling method uses wind drilling in the coal hole section. After drilling to the coal seam roof, a hole protection screen is lowered in the coal hole. During the process of withdrawing the drill, slitting and punching are performed while drilling gas extraction. The risk of this method is that during the process of withdrawing the drill, once coal and gas protrusion occurs in the hole, the hole protection screen hole may be damaged. Since there is a hole protection screen in the screen hole air intake device, the hole protection screen and the screen hole air intake device will both fail, which will bring difficulties to the subsequent slitting and punching gas extraction while drilling. Therefore, the backward slitting and punching gas extraction while drilling method is only suitable for medium-hard coal seams in non-protruding areas of protruding coal seams.

[0052] The beneficial effects of the present invention are:

[0053] 1. The current blowout prevention technology does not involve the improvement of the drilling tool itself, and only solves the problem from the blowout prevention device at the orifice, which cannot eliminate the gas power source that induces the blowout. The present invention points out that the gas power source that induces the blowout is located in the "loose hole gas bag" formed by the slit or punching of the coal hole section, and proposes a drainage drilling tool and a blowout prevention hole while drilling gas extraction method. The principle method and technical means of the blowout prevention hole are essentially different from the current blowout prevention technology.

[0054] 2. The extraction drilling tool is composed of multiple extraction drill rods, extraction high and low pressure conversion valves, sieve hole air inlet devices, open and close drill bits and extraction water braids. Its overall characteristics are: the extraction drilling tool acts as a "extraction pipe" that rotates and moves while drilling, and the sieve hole air inlet device acts as a "sieve hole pipe" that rotates and moves while drilling, and implements gas extraction while drilling for the gas in the "pine hole gas bag" formed by cutting and punching; the gas in the "pine hole gas bag" goes through the gas extraction channel of the extraction drilling tool, and the water coal slag in the "pine hole gas bag" goes through the slag discharge channel between the surface of the drilling tool and the borehole wall, realizing the separate extraction and discharge of water coal slag and gas in the hole, which can solve the problem of gas exceeding the limit in the through-layer drilling blowhole from the source.

[0055] 3. The current blowout prevention hole device outside the hole collects the extracted gas at the hole mouth. The concentration of the extracted gas is extremely low. After the low concentration enters the gas extraction network, it has a great impact on the gas concentration of the network, which has a serious negative interference on the utilization of coal mine gas. The gas extracted by the extraction drilling tool is pure gas without air mixed in the top of the "pine hole gas bag" in the borehole, which has a positive effect on the utilization of coal mine gas.

[0056] 4. In order to avoid gas over-limit accidents in through-layer drilling holes, many mines adopt the passive measure of "drilling first, then extraction, and then cutting and punching holes", which not only greatly reduces the engineering efficiency, but also greatly increases the engineering cost, and also loses the opportunity to use the natural power of the protruding coal seam (coal and gas protrusion in the hole) to break the coal. Using extraction drilling tools, cutting and punching holes and anti-blowout holes in the coal hole section to extract gas while drilling will not only improve the efficiency of gas extraction and management of through-layer drilling holes, but also reduce the cost of gas extraction and management of through-layer drilling holes.

[0057] 5. Accidents of gas exceeding the limit in through-layer drilling and blowout holes in coal seams account for 30% to 80% of the total number of gas exceeding the limit accidents in coal seams, and have become the main safety hazard in coal seams. Through-layer drilling and extraction drilling tools and anti-blowout hole while drilling gas extraction methods are of great significance to coal mine safety production. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is the overall plan diagram of the extraction drilling tool and its on-site construction;

[0059] Figure 2 Appearance and structure diagram of local groove extraction drill pipe;

[0060] Figure 3 Structural diagram of welded arc support block type extraction drill pipe;

[0061] Figure 4 The appearance and structure of the special-shaped pipe extraction drill pipe;

[0062] Figure 5 Appearance and structure diagram of extraction drill pipe with support;

[0063] Figure 6 Diagram of the sealed connection between the extraction drill pipes;

[0064] Figure 7 Stereoscopic diagram of the components of the extraction type high and low pressure conversion valve;

[0065] Figure 8 Illustration of the working position of the extraction type high and low pressure conversion valve;

[0066] Fig. 9 Sieve hole air intake device structure illustration;

[0067] Fig.10 Open and closed drill parts diagram;

[0068] Fig.11 Diagram of extraction drilling tools for drilling through layers at low angles;

[0069] Fig.12 Diagram of extraction drilling tools for drilling holes through extremely soft and protruding coal seams;

[0070] Fig.13 Diagram of extraction drilling tools for drilling holes through medium-hard protruding coal seams;

[0071] Fig.14 Diagram of the structure of the extraction water braid;

[0072] Fig.15 Illustration of the structure of the controlled-spray drainage box. DETAILED DESCRIPTION

[0073] The present invention is further described below in conjunction with the accompanying drawings.

[0074] like Figure 1 The figure shows the overall scheme of the through-layer drilling extraction drilling tool, which includes an extraction water braid 5, a plurality of extraction drill rods 1, an extraction high-low pressure conversion valve 2, a sieve hole air intake device 3 and an open-and-close drill bit 4 connected in sequence; in order to better realize the anti-blowout function of the drilling tool of the present invention, the existing orifice drainage box is improved, and a blowout control drainage box 6 installed in conjunction with the extraction drill rod 1 is provided at the orifice position. A gas extraction channel is constructed in the central part of the inner cavity of the through-layer drilling extraction drill tool, and a flow supply channel of the drill tool is constructed between the outer tube and the inner tube of the extraction drill rod of the through-layer drilling extraction drill tool. The gas in the "Songdong gas bag" goes through the gas extraction channel, and the water-coal slag in the "Songdong gas bag" goes through the external slag discharge channel. By extracting the gas in the "Songdong gas bag" while drilling, the gas power source inducing the blowhole is eliminated in time, and the gas extraction channel is used as a channel for lowering the hole protection screen when withdrawing the drill.

[0075] like Figure 2 As shown, the extraction drill pipe 1 also includes an outer tube 11 and an inner tube 12 arranged coaxially. The outer tube 11 is formed with two groups of local arc-surface protrusions 111 in the inner hole of the outer tube by local hot extrusion. The local arc-surface protrusions 111 of the inner hole of the outer tube cooperate with the outer circle of the inner tube and support the inner tube 12, so that the outer tube 11 and the inner tube 12 remain coaxial. The number of each group of arc-surface protrusions 111 is two or three. The outer surface shape of the outer tube 11 can be a spiral groove shape (such as Figure 2 a-like Figure 2 b), spiral ribs (as shown in Figure 2 c), the drill rod can also be three (four) prism-shaped or three (four) prism-shaped grooved to increase the slag crushing, stirring and conveying capabilities of the drill rod. The axial space between the outer tube 11 and the inner tube 12 of the extraction drill rod 1 is the flow supply channel 14 of the drilling tool, the center hole of the inner tube of the extraction drill rod is the gas extraction channel 15, and the annular gap between the outer tube and the borehole wall is the slag discharge channel.

[0076] like Figure 3As shown, the extraction drill pipe 1 also includes an outer tube 11, an inner tube 12 and an arc-surface support block 13 welded to the inner wall of the outer tube 11. Each group of support blocks 13 has two or three evenly distributed along the circumference of the inner hole of the outer tube. Support block welding holes 131 are provided on the support blocks 13, and outer tube welding holes 112 are provided on the outer tube 11. The radius of the outer arc surface of the support block 13 is equal to the radius of the inner hole of the outer tube 11, and the radius of the inner arc surface of the support block 13 is equal to the radius of the outer circle of the inner tube 12. The support block 13 is welded to the inner wall of the outer tube 11 by using the outer tube welding holes 112 on the outer tube 11, and the support block 13 is welded to the outer circle of the inner tube 12 by using the support block welding holes 131. The outer surface shape of the outer tube 11 is spiral groove-shaped or spiral rib-shaped or triangular-shaped or quadrangular-shaped or triangular-grooved or quadrangular-grooved, so as to increase the slag crushing, stirring and conveying capacity of the drill pipe;

[0077] like Figure 4 As shown, the extraction drill pipe 1 also includes a special-shaped outer tube 11 and an inner tube 12. The outer surface of the special-shaped outer tube 11 is provided with an axial groove 113, and the inner hole is provided with an axial arc surface protrusion 114 corresponding to the axial groove. The axial arc surface protrusion 114 of the inner hole of the special-shaped outer tube cooperates with the outer circle of the inner tube and supports the inner tube 12, so that the outer tube 11 and the inner tube 12 remain coaxial. The number of axial grooves 113 and axial arc surface protrusions 114 is 2 or 3. Spiral grooves or spiral ribs are provided on the arc surface of the outer surface of the outer tube to increase the slag crushing, stirring and conveying capacity of the drill pipe.

[0078] like Figure 4 As shown in c, the extraction drill pipe 1 includes an outer tube 11 and an inner tube 12 arranged coaxially, the outer tube 11 is a hot-twisted special-shaped outer tube 11 formed by a hot-twisting method under a constrained state, the outer surface of the hot-twisted special-shaped outer tube 11 forms a large spiral groove 115, the inner hole of the hot-twisted special-shaped outer tube 11 forms a large pitch cambered surface protrusion corresponding to the large spiral groove 115, the large pitch cambered surface protrusion of the inner hole of the hot-twisted special-shaped outer tube 115 cooperates with the outer circle of the inner tube 12, and supports the inner tube 12 so that the outer tube 11 and the inner tube 12 remain coaxial, so that the outer tube 11 and the inner tube 12 remain coaxial, the number of large spiral grooves 115 and large pitch cambered surface protrusions is two or three; the axial space between the outer tube 11 and the inner tube 12 is the flow supply channel 14 of the extraction drill, the center hole of the inner tube 12 is the gas extraction channel, and the annular gap between the outer tube 11 and the borehole wall is the slag discharge channel.

[0079] like Figure 5 As shown, the extraction drill pipe 1 includes an outer tube 11, an inner tube 12 and a support 16. The support 16 is installed between the outer tube 11 and the inner tube 12. The support keeps the outer tube 11 and the inner tube 12 coaxial. The outer shape of the outer tube 11 can be a spiral rib shape (such as Figure 5 a), spiral groove (as shown in Figure 5 b), triangular (as shown in Figure 5 c) or triangular grooved (as shown in Figure 5 d), the number of grooves and ribs is two or more; the grooves may be rectangular grooves, trapezoidal grooves, arcuate grooves, or rifled linear grooves; the ribs may be welded ribs, machined ribs, or wear-resistant clad ribs, and the rib surfaces may be flat ribs or arcuate ribs. The shape of the ribs is not limited, and the width of the ribs is equal to or greater than the height of the ribs. The grooves, ribs, and arc edges arranged on the surface of the outer tube 11 serve to increase the slag crushing, stirring, and conveying functions of the outer tube. There are many types of double-wall drill pipes used in the fields of soft formation drilling, coal seam gas content fixed-point sampling, and oil drilling. When similar double-wall drill pipes are used in conjunction with the extraction-type high- and low-pressure conversion valve 2 and the sieve hole air intake device 3 included in the present invention, they are also within the protection scope of the present invention.

[0080] like Figure 6 As shown, for Figure 2~Figure 5 Several types of extraction drill pipes 1 are introduced. The outer tubes 11 of the extraction drill pipe 1 with different shapes are transformed into thick-walled circular outer tubes at the ends by extrusion molding or friction welding joints. Male buckles and female buckles are arranged at both ends of the thick-walled circular outer tubes. Adjacent outer tubes 11 are connected by sealed threads, and adjacent inner tubes 12 are connected by overlapping seals ( Figure 6 a) or plug-in seal ( Figure 6 b) Connection. In order to reduce the influence of the plug seal or the lap seal on the flow supply channel 14, one end of the inner tube 12 extends out of the male buckle so that the plug seal or the lap seal is located in the outer tube 11 with a larger inner hole diameter.

[0081] like Figure 7 The figure shows an extraction type high-low pressure conversion valve 2, which includes an outer valve tube 21, an inner valve tube 22 and a high-low pressure conversion assembly; the central hole of the inner valve tube 22 is a gas extraction channel, and male buckles and female buckles are respectively provided at both ends of the outer valve tube 21, the female buckle of the outer valve tube 21 is connected to the male buckle of the extraction type drill pipe 1, and the male buckle of the outer valve tube 21 is connected to the female buckle of the sieve hole air intake device 3, one end of the inner valve tube 22 is sealed and connected to the inner tube 12 of the extraction type drill pipe 1, and the other end of the inner valve tube 22 is sealed and connected to the rib-shaped inner tube 32 of the sieve hole air intake device 3, and a sealing member is provided at one end of the inner valve tube 22.

[0082] like Figure 7As shown, the valve outer tube 21 is provided with two, three or four axial convex ribs or spiral convex ribs 211 whose two ends gradually become inclined surfaces 212, and a cutting blade 213 is provided on the side of the inclined surface 212; two radial or oblique water jet nozzles 214 are provided on the two convex ribs of the valve outer tube 21; intermittent spiral grooves 215 are provided on the convex ribs of the valve outer tube, so that the valve outer tube 21 has the functions of crushing and conveying. The convex ribs provided on the valve outer tube 21 are mainly used for: first, to provide more space for the slag discharge of the drilling tool; second, to provide a larger radial dimension for the installation of the nozzle; and third, to allow the valve outer tube 21 to have a stirring function. If the wall thickness of the valve outer tube 21 is increased, the outer surface of the valve outer tube 21 is not provided with convex ribs, and the outer shape of the valve body is designed to be polygonal or circular, etc., it is also within the protection scope of the present invention.

[0083] like Figure 7 As shown, the high-low pressure conversion assembly is installed in the annular flow supply channel 24 between the valve outer tube 21 and the valve inner tube 22, and the high-low pressure conversion assembly includes a sliding valve core 231, a spring 232, a front support 233, a rear support 234 and a fixing pin 235; the sliding valve core 231 is installed between the front support 233 and the rear support 234, and the spring 232 is installed between the sliding valve core 231 and the valve inner tube 22, and the front support 233 and the rear support 234 are connected to the valve outer tube 21 through a fixing pin; when working, both ends of the spring 232 are in contact and cooperate with the sliding valve core 231 and the rear support 234.

[0084] like Figure 8 As shown, the sliding valve core 231 has three working positions: Figure 8 The first picture in the first row shows the stop-drilling lockout station, which prevents the water-coal slag in the hole from flowing back to the flow supply channel of the extraction drill pipe when the drilling is stopped for loading and unloading the drill pipe; Figure 8 The second figure in the first row shows a low-pressure drilling station, where all low-pressure fluid is supplied to the open-close drill bit 4; Figure 8 The third figure in the first row shows a water jet cutting or punching station, where high-pressure fluid is supplied to the jet nozzle 214, and a small amount of fluid is supplied to the open-close drill bit 4 through leakage or micro-pore leakage to cool the drill bit. There are many ways to supply a small amount of water flow to the drill bit under high pressure. Generally, engineers can make slight changes to the sliding valve core and the support as needed, which is also within the scope of protection of the present invention.

[0085] During the implementation of the present invention, the jet nozzle 214 of the extraction type high-low pressure conversion valve 2 can be replaced. When a small-diameter nozzle is used, hydraulic slitting of medium-hard coal can be achieved, and when a large-diameter nozzle is used, hydraulic punching of soft coal seams can be achieved. Two groups of nozzles 214 can also be set on the convex rib 211 of the valve body, one group is two radial slitting nozzles, and one group is two radial or oblique punching nozzles. The above three-station high-low pressure conversion assembly is designed as a four-station high-low pressure conversion assembly, namely the locking station, low-pressure drilling station, medium-pressure punching station and high-pressure slitting station, which is also within the protection scope of the present invention. However, due to the influence of the medium pressure in the hole outside the valve outer tube 21, the switching accuracy of the punching station and the slitting station will be reduced, the difficulty of spring selection will increase, and the reliability will be reduced. If the extraction type high-low pressure conversion valve 2 is designed with four stations, it is also within the protection scope of the present invention.

[0086] Fig. 9 The figure shows the structure of the sieve hole air intake device 3, the sieve hole air intake device 1 comprises a rib-shaped outer tube 31, a rib-shaped inner tube 32 and an air intake sieve plate 33; male buckles and female buckles are respectively provided at both ends of the rib-shaped outer tube 31, the female buckle is connected to the extraction type high and low pressure conversion valve 2, and the male buckle is connected to the open and close drill bit 4; a sealing member is installed at one end of the rib-shaped inner tube 32, and the central hole of the rib-shaped inner tube 32 is a gas extraction channel, the rib-shaped inner tube 32 is embedded in the rib-shaped outer tube 31, and the rib-shaped inner tube 32 and the rib-shaped outer tube 31 are integrated into one by combining an impregnation seal and a fixing pin, and the space between the rib-shaped outer tube 31 and the rib-shaped inner tube 32 is a flow supply channel 14. The outer tube convex rib 311 and the inner tube convex rib 321 can be axial convex ribs or spiral convex ribs, with two, three or four convex ribs, and radial air inlet holes 312 penetrating the outer convex rib and radial air inlet holes 322 of the inner convex rib are provided on the convex ribs; the air inlet sieve plate 33 is welded on the convex rib 311 of the convex rib-shaped outer tube 31 and covers the radial air inlet holes 312; the sieve holes 331 of the air inlet sieve plate 33 are tapered holes, and the air inlet diameter of the tapered holes 331 is much smaller than the diameter of the radial air inlet holes 312 of the outer convex rib and the diameter of the radial air inlet holes 322 of the inner convex rib, and the sum of the air inlet areas of all tapered holes 331 is larger than the inner hole cross-sectional area of ​​the convex rib-shaped inner tube 32.

[0087] Furthermore, the rib 311 on the rib-shaped outer tube 31 is removed, or even the rib-shaped outer tube 31 is changed into a groove-shaped outer tube, and the radial air inlet hole 312 is arranged in the groove of the groove-shaped outer tube. This change will not only further increase the amount of coal slag in the gas extraction channel, but also increase the amount of water inlet into the gas extraction channel. The air intake function is weakened, but the air intake function is still available. This change is also within the protection scope of the present invention.

[0088] like Fig.10The open-and-close drill bit 4 is shown, and the open-and-close drill bit 4 includes a drill bit body 41, a short-section inner tube 42 and an opening cover 43; the drill bit body 41 is coaxially installed with the short-section inner tube 42; one end of the drill bit body 41 is provided with a female buckle that matches the convex rib-shaped outer tube 31; the outer edge of the other end of the drill bit body 41 is provided with end teeth, and the center of the other end of the drill bit body 41 is provided with an opening cover 43 covering the short-section inner tube 42; the opening cover 43 is provided with two pairs of pin holes, one pair of pin holes is provided with a high-strength pin shaft, and the other pair of pin holes is provided with a low-strength shear pin. In the actual implementation process, there are many ways to open the opening cover 43. Generally, mechanical engineers can selectively design according to the double-channel structure and geometric space of the open-and-close drill bit 4 with the short-section inner tube 42, such as a shear pin type opening cover 43, a self-locking bevel type opening cover 43 and a hinged hinge type opening cover 43. If these changes are used in conjunction with the components of the present invention, they are also within the protection scope of the present invention.

[0089] like Fig.11 As shown, the extraction drilling tool is composed of multiple extraction drill rods 1, extraction high and low pressure conversion valves 2, sieve hole air intake devices 3, open and close drill bits 4 and extraction water braids 5. When the inclination angle of the borehole is small, the sieve hole air intake device 3 is easily submerged by water coal slag and affects the radial air intake function. For this reason, a certain length of extraction drill rod 7 can be installed between the high and low pressure conversion valve 2 and the sieve hole air intake device 3. The purpose is to increase the height difference between the sieve hole air intake device 3 and the extraction high and low pressure conversion valve 2 to avoid the sieve hole air intake device 3 being submerged by water.

[0090] like Fig.12 As shown, the extraction drilling tool is composed of multiple extraction drill rods 1, extraction high and low pressure conversion valves 2, sieve hole air intake device 3, open and close drill bit 4 and extraction water braid 5. For extremely soft and protruding coal seams that are difficult to drill holes, the extraction high and low pressure conversion valve 2 is cancelled, and 2 to 4 oblique punching water jet nozzles 45 are installed at the end of the open and close drill bit 4. The outlet direction of the water jet nozzle 45 forms an angle of about 45 degrees with the drilling direction, and drilling and punching are carried out simultaneously in the coal hole section. Although this gas extraction while drilling method will cause a small amount of water in the gas extraction channel, when the drilling speed is slow, the sieve hole air intake device 3 will be suspended in the punching cave, and the water inflow in the gas extraction channel can be controlled by the punching progress.

[0091] like Fig.13As shown, the extraction drilling tool is composed of a plurality of extraction drill rods 1, an extraction high-low pressure conversion valve 2, a sieve hole air intake device 3, an open-close drill bit 4 and an extraction water braid 5. For the medium-hard protruding coal seam that is easy to drill, the sieve hole air intake device 3 is cancelled, and no slitting or punching and gas extraction while drilling are carried out during the drilling of the coal hole section. Conventional drilling is carried out in the coal hole section. After the drill bit enters the coal seam roof, the hole protection screen pipe is lowered, and slitting or punching and gas extraction while drilling are carried out during the drilling withdrawal. The hole protection screen pipe is used to implement gas extraction while drilling during the drilling withdrawal slitting or punching. This simplified processing method is suitable for medium-hard coal seams in non-protruding areas of protruding coal seams. If coal and gas protrude in the hole during the drilling withdrawal slitting or punching process, the hole protection screen pipe will be damaged. After the hole protection screen pipe is damaged, it will be difficult to implement gas extraction while drilling.

[0092] like Fig.14 As shown, the extraction water braid 5 includes a hollow water braid outer body 51, an extraction pipe 52, a pressure gauge 53, an extraction switch 54 and a flow port 55. The inner cavity of the hollow water braid outer body 51 is hollow and is equipped with a hollow water braid inner tube 56. An annular liquid flow channel is formed between the hollow water braid outer body 51 and the hollow water braid inner tube 56. The inner hole of the hollow water braid inner tube 56 is a gas extraction channel. One end of the hollow water braid outer body 51 is connected to the outer tube of the extraction drill pipe by a thread, and the other end of the hollow water braid outer body 51 is equipped with an extraction pipe 52 connected to the hollow water braid inner tube 56. The other end of the hollow water braid inner tube 56 is connected to the inner tube of the extraction drill pipe by a thread. A flow port 55 is opened on the outside of the hollow water braid outer body 51, and the flow port 55 is connected to the annular liquid flow channel. A pressure gauge 53 and a drainage switch 54 are installed on the extraction pipe 52. The pressure gauge 53 displays the gas pressure in the borehole cavity and the gas pressure in the "Songdong gas bag" during gas extraction while drilling. The gas pressure in the "Songdong gas bag" can also be known by turning off the switch. According to the gas pressure in the borehole cavity and the gas pressure in the "Songdong gas bag", the cutting or punching operation method is adjusted and necessary auxiliary control measures are taken.

[0093] In addition, it is necessary to explain other combinations of extraction drilling tools: for the extraction drilling tools composed of multiple extraction drill rods 1, extraction high and low pressure conversion valves 2, sieve hole air intake devices 3, open and close drill bits 4 and extraction water braids 5, the sieve hole air intake device 3 can be designed and processed as one piece with the open and close drill bit 4, and the extraction high and low pressure conversion valve 2 can be processed as one piece with the sieve hole air intake device 3. The function of preventing blowout holes of the extraction drilling tools and the function of lowering the hole protection screen before lifting the drill can also be realized, which is also within the protection scope of the present invention.

[0094] In order to realize the anti-blowout function of the through-layer drilling and extraction drilling tool, it is necessary to use a controlled-blowout drainage box 6 at the orifice, and the controlled-blowout drainage box 6 includes a hole sealer 61, a drainage box 62, a gas drainage pipe 63, a water-coal slag drainage pipe 64, a dust-proof brush 65 and a controlled-blowout plug-in plate 66 installed in the drainage box 62; during installation, the controlled-blowout drainage box 6 is installed at the orifice through the hole sealer 61; a hole sealer 61 is provided at one end of the drainage box 62, and the drainage box 63 is provided with a gas drainage pipe 63, a water-coal slag drainage pipe 64, a dust-proof brush 65 and a controlled-blowout plug-in plate 66 installed in the drainage box 62. A dust-proof brush 65 is provided inside the other end of the flow box 62, a gas drainage pipe 63 is provided at the upper part of the drainage box 62, and a water-coal slag drainage pipe 64 is provided at the lower part of the drainage box 62; two symmetrical spray control plug plates 66 are installed at one end of the hole sealer 61 in the drainage box 62, and the cross-sectional area of ​​the slag inlet channel in the drainage box 62 is controlled by moving the position of the spray control plug plate 66. When coal and gas protrusion occurs in the coal hole section, compulsory spray prevention and spray control are implemented. During operation, the position of the spray control plug plate 66 is manually moved to reduce the cross-sectional area of ​​the slag discharge channel in the drainage box 62. A plurality of circular holes are provided on the spray control plug plate 66, and the diameter of the circular hole is equivalent to the annular gap width of the slag discharge channel in the drainage box 62.

[0095] This embodiment does not impose any formal limitation on the shape, material, structure, etc. of the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0096] In the description of the present invention, it is necessary to understand that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection content of the present invention.

[0097] If the words "first", "second", etc. are used in this document to limit components, those skilled in the art should know that the use of "first" and "second" is only to facilitate the description of the present invention and simplify the description. Unless otherwise stated, the above words have no special meaning.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A through-layer drilling and extraction drilling tool, characterized in that: It includes a drainage water braid, multiple drainage drill rods, a drainage high-low pressure conversion valve, a sieve hole air intake device and an open-close drill bit connected in sequence; a controlled spray drainage box installed in conjunction with the through-layer drilling drainage drill tool is provided at the hole mouth; The extraction drill pipe adopts scheme 1, scheme 2, scheme 3 or scheme 4; Solution 1: The extraction drill pipe comprises an outer pipe and an inner pipe which are inserted and matched. The outer pipe is protruded from the inner hole of the outer pipe by local hot extrusion along the length direction to form two groups of local arc surface protrusions. The local arc surface protrusions match the outer circle of the inner pipe and support and install the inner pipe so that the outer pipe and the inner pipe remain coaxial. The number of each group of local arc surface protrusions is two or three evenly distributed along the circumference of the inner hole of the outer pipe. The outer surface shape of the outer pipe is spiral groove shape or spiral rib shape or triangular shape or quadrangular shape or triangular groove shape or quadrangular groove shape, so as to increase the slag crushing, stirring and conveying capacity of the drill pipe; The axial space between the outer tube and the inner tube is a flow supply channel of the extraction drilling tool, the central hole of the inner tube is a gas extraction channel, and the annular gap between the outer tube and the borehole wall is a slag discharge channel; Option 2: The extraction drill pipe comprises an outer tube, an inner tube and two groups of arc surface support blocks welded to the inner wall of the outer tube, each group of support blocks has two or three evenly distributed along the circumference of the inner hole of the outer tube, the support blocks are provided with support block welding holes welded to the inner tube, the outer tube is provided with outer tube welding holes welded to the support blocks, the radius of the outer arc surface of the support block is equal to the radius of the inner hole of the outer tube, and the radius of the inner arc surface of the support block is equal to the radius of the outer circle of the inner tube; the outer surface shape of the outer tube is spiral groove shape or spiral rib shape or triangular shape or quadrangular shape or triangular groove shape or quadrangular groove shape, so as to increase the slag crushing, stirring and conveying capacity of the drill pipe; The axial space between the outer tube and the inner tube is a flow supply channel of the extraction drilling tool, the central hole of the inner tube is a gas extraction channel, and the annular gap between the outer tube and the borehole wall is a slag discharge channel; Option 3: The extraction drill pipe comprises an outer pipe and an inner pipe, the outer pipe is a special-shaped outer pipe, the outer surface of the special-shaped outer pipe is provided with an axial groove, the inner hole of the special-shaped outer pipe is provided with an axial cambered protrusion corresponding to the axial groove, the axial cambered protrusion of the inner hole of the special-shaped outer pipe is installed in cooperation with the outer circle of the inner pipe, and supports the inner pipe so that the outer pipe and the inner pipe remain coaxial, the number of axial grooves and axial cambered protrusions is evenly distributed as two or three around the circumference, and the outer surface of the outer pipe is provided with spiral grooves or spiral ribs to increase the slag crushing, stirring and conveying capacity of the drill pipe; The axial space between the outer tube and the inner tube is a flow supply channel of the extraction drilling tool, the central hole of the inner tube is a gas extraction channel, and the annular gap between the outer tube and the borehole wall is a slag discharge channel; Option 4: The extraction drill pipe comprises an outer tube and an inner tube which are inserted and matched. The outer tube is a hot-twisted special-shaped outer tube formed by a hot-twisting method under a constrained state. The outer surface of the hot-twisted special-shaped outer tube forms a large spiral groove. The inner hole of the hot-twisted special-shaped outer tube forms a large pitch cambered surface protrusion corresponding to the large spiral groove. The large pitch cambered surface protrusion of the inner hole of the hot-twisted special-shaped outer tube is installed in cooperation with the outer circle of the inner tube and supports the inner tube so that the outer tube and the inner tube remain coaxial. The number of the large spiral grooves and the large pitch cambered surface protrusions is two or three. The axial space between the outer tube and the inner tube is a flow supply channel of the extraction drilling tool, the central hole of the inner tube is a gas extraction channel, and the annular gap between the outer tube and the borehole wall is a slag discharge channel.

2. The through-layer drilling and extraction drilling tool according to claim 1, characterized in that: When the inclination angle of the borehole is small, an extraction type drill rod is installed between the extraction type high-low pressure conversion valve and the sieve hole air intake device to increase the height difference between the sieve hole air intake device and the extraction type high-low pressure conversion valve to prevent the sieve hole air intake device from being submerged in water and weakening the air intake function.

3. The through-layer drilling and extraction drilling tool according to claim 1, characterized in that: When drilling in extremely soft and protruding coal seams that are difficult to drill holes in, the extraction high- and low-pressure conversion valve is removed, and 2 to 4 oblique punching water jet nozzles are installed in the open and close drill head. The outlet direction of the water jet nozzle forms an angle of 45 degrees with the drilling direction, and drilling and punching are carried out simultaneously in the coal hole section.

4. The through-layer drilling and extraction drilling tool according to claim 1, characterized in that: When drilling in a medium-hard protruding coal seam that is easy to drill a hole, the screen hole air intake device is removed, no slitting or punching is performed during the drilling of the coal hole section, and no gas extraction while drilling is performed. The hole-protecting screen pipe is lowered before drilling back out, and slitting or punching is performed during drilling back out. Gas extraction while drilling is performed using the hole-protecting screen pipe during the slitting or punching when drilling back out.

5. The through-layer drilling and extraction drilling tool according to any one of claims 1 to 4, characterized in that: The ends of the outer tube are transformed into thick-walled circular outer tubes by extrusion molding or friction welding joints. Male buckles and female buckles are arranged at both ends of the thick-walled circular outer tube. Adjacent outer tubes are connected by sealed threads, and adjacent inner tubes are connected by lap seals or plug seals.

6. The through-layer drilling and extraction drilling tool according to claim 5, characterized in that: The extraction type high-low pressure conversion valve comprises a valve outer tube, a valve inner tube and a high-low pressure conversion assembly, wherein the valve outer tube and the valve inner tube are coaxially mounted, and the high-low pressure conversion assembly is mounted in a flow supply channel formed between the valve outer tube and the valve inner tube; The central hole of the valve inner tube is a gas extraction channel; the two ends of the valve outer tube are respectively provided with a male buckle and a female buckle, the female buckle of the valve outer tube is connected to the male buckle of the extraction drill pipe, and the male buckle of the valve outer tube is connected to the female buckle of the sieve hole air intake device, one end of the valve inner tube is sealed with the inner tube of the extraction drill pipe, and the other end of the valve inner tube is sealed with the rib-shaped inner tube of the sieve hole air intake device, and a sealing member is provided at one end of the valve inner tube.

7. The through-layer drilling and extraction drilling tool according to claim 6, characterized in that: The outer surface of the valve outer tube is provided with two to four axial convex ribs or spiral convex ribs whose two ends gradually become inclined surfaces, and a cutting blade is provided on the side of the inclined surface; radial water jet nozzles or oblique water jet nozzles are provided on the two axial convex ribs or two spiral convex ribs of the valve outer tube; intermittent spiral grooves are provided on the axial convex ribs or spiral convex ribs of the valve outer tube, and the intermittent spiral grooves enable the valve outer tube to have slag crushing, stirring and conveying functions.

8. The through-layer drilling and extraction drilling tool according to claim 7, characterized in that: The high-low pressure conversion assembly includes a sliding valve core, a spring, a front support, a rear support and a fixing pin; the sliding valve core is installed between the front support and the rear support, a spring is installed between the sliding valve core and the valve inner tube, and the front support and the rear support are connected to the valve outer tube through the fixing pin; when working, the two ends of the spring are in contact and cooperate with the sliding valve core and the rear support.

9. The through-layer drilling and extraction drilling tool according to claim 8, characterized in that: The sieve hole air intake device comprises a convex rib-shaped outer tube, a convex rib-shaped inner tube and an air intake sieve hole plate, the convex rib-shaped outer tube and the convex rib-shaped inner tube are coaxially mounted, the space between the convex rib-shaped outer tube and the convex rib-shaped inner tube is a flow supply channel, and the inner hole of the convex rib-shaped inner tube is a gas extraction channel; male buckles and female buckles are respectively provided at both ends of the convex rib-shaped outer tube, and a sealing member is installed at one end of the convex rib-shaped inner tube; The ribs of the rib-shaped outer tube and the rib-shaped inner tube are configured as axial ribs or spiral ribs, and the number of ribs of the rib-shaped outer tube and the rib-shaped inner tube is two, three or four; radial air intake holes penetrating the inner and outer ribs are configured on the ribs of the rib-shaped outer tube and the rib-shaped inner tube, and the air intake sieve plate is welded on the ribs of the rib-shaped outer tube and covers the radial air intake holes.

10. The through-layer drilling and extraction drilling tool according to claim 9, characterized in that: The air inlet sieve plate is provided with inverted cone-shaped sieve holes, the air inlet diameter of the sieve holes is one-half to one-fifth of the diameter of the radial air inlet through hole, and the sum of the air inlet areas of all the sieve holes is larger than the inner hole cross-sectional area of ​​the convex rib-shaped inner tube.

11. The through-layer drilling and extraction drilling tool according to claim 10, characterized in that: The open-and-close drill bit consists of a drill bit body, a short-section inner tube and an opening cover; a short-section inner tube is coaxially installed in the drill bit body; a female buckle that cooperates with a convex rib-shaped outer tube is provided at one end of the drill bit body; end teeth are installed at the outer edge of the other end of the drill bit body, and an opening cover covering the short-section inner tube is installed at the center of the other end of the drill bit body; two pairs of pin holes are provided on the opening cover, a high-strength pin shaft is installed in one pair of pin holes, and a low-strength shear pin is installed in the other pair of pin holes.

12. According to the through-layer drilling extraction drilling tool of claim 11, the extraction water braid comprises a hollow water braid outer body, an extraction pipe, a pressure gauge, an extraction switch and a flow supply port, a hollow water braid inner tube is coaxially installed in the inner cavity of the hollow water braid outer body, the inner hole of the hollow water braid inner tube is a gas extraction channel, one end of the hollow water braid outer body is connected to the outer tube of the extraction drill pipe, and the other end of the hollow water braid inner tube is connected to the inner tube of the extraction drill pipe, characterized in that: The other end of the hollow water braid outer body is equipped with an extraction pipe connected to the hollow water braid inner tube, and a pressure gauge and an extraction switch are installed on the extraction pipe. The pressure gauge displays the gas pressure in the inner cavity of the drill bit and the gas pressure in the "loose hole gas bag" during gas extraction while drilling; the "loose hole gas bag" refers to the gas power source of the spray hole located in the loose coal body formed by cutting or punching the coal hole section and in the cave formed by cutting and punching, and the loose coal body and the cave contain a large amount of free gas.

13. The through-layer drilling and extraction drilling tool according to claim 12, characterized in that: The control-spray drainage box comprises a hole sealer, a drainage box, a gas drainage pipe, a water-coal ash drainage pipe, a dust-proof brush and a control-spray plug-in plate installed in the drainage box; A hole sealer is provided at one end of the drainage box, a dust-proof brush is provided inside the other end of the drainage box, a gas drainage pipe is provided at the upper part of the drainage box, and a water-coal slag drainage pipe is provided at the lower part of the drainage box; two symmetrical blowout control plug plates are installed at one end of the hole sealer in the drainage box, and the cross-sectional area of ​​the slag inlet channel in the drainage box is controlled by moving the position of the blowout control plug plates. When coal and gas protrusion occurs in the coal hole section, compulsory blowout prevention and control are implemented.

14. A method for gas extraction while drilling using a blowout prevention hole of the through-layer drilling extraction drilling tool according to claim 13, wherein the gas extraction while drilling is performed by forward slitting and punching, characterized in that: The steps include: Step 1: Preparation The hole is enlarged, a controlled spray drainage box is installed at the hole mouth, the extraction pipe on the extraction water braid is removed, the extraction pipe is connected to the existing slag discharger through a retractable hose, and the slag discharger is connected to the extraction pipe network; The second step is drilling the rock hole section The rock hole section drilling does not implement gas extraction while drilling. Similar to the current drilling, 3MPa static pressure water is supplied to the extraction water braid to implement the rock hole section drilling; Step 3: Preparation before slitting and punching Once the borehole enters the coal seam, first install the extraction pipe at the tail of the extraction water braid, turn on the high-pressure pump station used for slot punching, and connect the relevant pipelines of the controlled spray drainage box; Step 4: Gas extraction while drilling through blowout prevention holes The forward slotting and punching process is similar to the current forward slotting and punching process. The through-layer drilling extraction drill tool acts as a "extraction pipe" that rotates and moves while drilling, and the sieve hole air intake device acts as a "sieve hole pipe" that rotates and moves while drilling. The gas in the "loose hole gas bag" formed by the slotting and punching is extracted while drilling. During the gas extraction while drilling, the drilling worker observes the pressure gauge on the extraction water braid. The pressure gauge shows the gas pressure in the inner cavity of the drill tool during the gas extraction while drilling. Three situations will occur during the gas extraction while drilling of the forward slotting and punching: Case I: Under normal circumstances, the gas pressure in the inner cavity of the through-layer drilling extraction drilling tool is under negative pressure, and normal water jet cutting or punching operations are carried out, and the drill rod is installed to implement gas extraction while drilling for the gas in the "songdong gas bag"; Case II: Abnormal situation, when the gas pressure in the inner cavity of the through-layer drilling extraction drill is at positive pressure or high pressure, reduce the flow rate of the through-layer drilling extraction drill, reduce the rotation speed of the through-layer drilling extraction drill, stop the forward and backward movement of the through-layer drilling extraction drill, and suspend the installation of the drill rod. When the gas pressure in the inner cavity of the through-layer drilling extraction drill drops to negative pressure or normal pressure, perform normal cutting or punching operations, install drill rods, and implement gas extraction while drilling for the gas in the "songdong gas bag"; Case III: Coal and gas outburst in the hole. When the dynamic phenomenon of coal and gas outburst in the hole occurs, the gas pressure in the inner cavity of the through-layer drilling extraction drill will rise sharply to positive pressure. In this case, the controlled spraying operation is:

1. Reduce the flow rate of the through-layer drilling extraction drill, reduce the rotation speed of the through-layer drilling extraction drill, and strictly prohibit the forward and backward movement of the through-layer drilling extraction drill; 2. Control the opening degree of the switch of the extraction pipe of the extraction water braid to prevent the retractable hose and the slag discharger from being destroyed and causing gas to exceed the limit; 3. Move the position of the controlled spraying plug plate in the controlled spraying drainage box to prevent the orifice from spraying and causing gas to exceed the limit; take the above measures, when the gas pressure in the inner cavity of the through-layer drilling extraction drill is reduced to negative pressure or normal pressure, resume normal slitting or punching operations, and install drill rods to implement gas extraction while drilling for the gas in the "songdong gas bag"; Step 5: Lower the hole screen before drilling back out When the slotting and punching operation advances to the roof of the coal seam or the drill bit enters the roof of the coal seam, the extraction pipe and pressure gauge at the tail of the extraction water braid are removed, and the hole protection screen is lowered before the drill is withdrawn. The hole protection screen with barbs is placed on the top of the coal hole section through the inner hole of the extraction water braid, the inner tube of the extraction drill pipe, the valve inner tube, the rib-shaped inner tube, the short inner tube of the open-and-close drill bit, and the open cover; after the hole protection screen is lowered, the extraction pipe and pressure gauge of the extraction water braid are reinstalled, and the gas extraction while drilling is started; Step 6: Drilling and gas extraction while drilling During the process of drilling back, the normal extraction of the extraction water braid is maintained, and repeated operations of backward cutting or punching are carried out as needed. The gas extraction while drilling is to replace the air intake function of the screen hole air intake device with the inserted hole protection screen pipe, and the gas on the top of the "pine cave gas bag" is extracted while drilling. The gas pressure in the inner cavity of the through-layer drilling extraction drill bit is kept in a negative pressure or normal pressure state to avoid blowouts during the drilling back process.

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