CN105781419B - For broken ground drilling center deslagging injection type suction drilling tool and its application method - Google Patents

Abstract

The invention discloses a central slag ejection suction drilling tool for drilling in soft formations, which includes an air intake pipe, a slag discharge pipe, a power head and a drill pipe. The drill pipe is provided with a slag discharge passage and an air intake passage. The front end of the drill pipe is equipped with an ejection type suction drill bit, the end of the ejection type suction bit is provided with a cutting bit, the top side wall of the ejection type suction bit is provided with a slag inlet hole, and the inner side wall of the cutting bit is provided with a There are injection holes, and a high-pressure injection channel is provided in the injection-type suction drill bit. The present invention uses the high-pressure injection channel to jet into the central slag discharge channel, forming a negative pressure area in the slag discharge channel, and the slag inlet hole generates suction for drilling cuttings. Suction effect, the jet air ejected from the injection hole will stir the bottom of the drill hole, and push the cuttings at the bottom of the hole to move into the slag inlet hole, so that the cuttings at the bottom of the hole will enter the central slag discharge channel through the slag inlet hole, solving the problem The problems encountered in the drilling process of existing coal seam gas drainage holes, such as stuck drill, buried drill and difficult slag discharge in the hole, greatly improve the drilling efficiency and drilling depth.

Description

Central slag ejection suction drilling tool for drilling in soft formations and its application method

technical field

The invention belongs to the technical field of special methods or equipment for drilling, and in particular relates to an ejector-type suction drilling tool for slag discharge in the drilling center of soft formations and its application method.

Background technique

Coalbed methane has been widely concerned as an unconventional natural gas energy source and has an important impact on underground coalbed gas outbursts. The use of drilling methods to carry out advanced drilling in the coal seam working face and implement coalbed gas drainage operations is the key to realize the utilization and prevention of coalbed methane. The main method of underground coal seam gas outburst. The existing coal seam drilling adopts traditional positive circulation drilling technology and tools. Due to the development of coal seam cracks and soft texture, during the drilling process, the drilling flushing medium enters from the center of the drilling tool. During the process of returning the bottom of the hole and carrying cuttings from the annular gap between the drilling tool and the hole wall to the slag inlet, it is often caused by the disturbance of the hole wall by the flushing medium or the movement of the cuttings at the bottom of the hole. The drilling tool and the hole wall are jammed, resulting in problems such as stuck drill, buried drill and difficult discharge of cuttings at the bottom of the hole during the drilling process.

The Chinese patent application number is 201310566830.6, and the title of the invention is "drilling tool for slag removal and anti-blocking in double layers for drilling into soft and outburst coal seams and its use method". Blocking drilling tools, including double-layer internal slag discharge anti-blocking drill pipe, center return drill bit, rotary sealing water supply device or air supply device, the rotary sealing water supply device or air supply device is connected with the double-layer internal slag discharge anti-blocking drill pipe on the drilling rig , the center reflow drill bit is installed at the front end of the double-layer internal slag discharge and anti-blocking drill pipe. It consists of an outer drill pipe body, an inner connecting pipe and a porous pipe welded to the inner wall of the inner connecting pipe. The structure of the rod body is complicated, the processing is troublesome, and the strength is low, so it cannot be used for deep drilling. Slag, the slag inlet of the center hole is set in the middle of the cutter head. When the drill pipe rotates at a high speed, a large centrifugal force is likely to be generated at the center hole, so that the slag will be stuck at the slag inlet of the center hole. , resulting in problems such as drill sticking, buried drilling, and difficulty in discharging cuttings at the bottom of the hole during the drilling process.

The Chinese patent application number is 201310037786.X, and the title of the invention is "Cyclone Jet Drill Bit". The sampling port of the drill body is provided with a cutting head for drilling and sampling, and the wall of the drill body is provided with a swirl jet hole connected to the cavity near the cutting head, and the center line of the swirl jet hole is in line with the bit body. The axes intersect each other in the space; the center line of the swirl jet hole forms an included angle of 5°~60° with the drilling direction of the drill bit body, and the cutting surface of the cutting head forms an included angle of 30°~80°; in addition, the jet drill bit also adopts the center The slag is fed into the hole, and the slag inlet of the center hole is set in the middle of the cutter head. When the cutter head rotates at a high speed, it is easy to generate a large centrifugal force at the slag inlet of the center hole. The problem of centrifugal force is solved in the cutter head. Rotating compressed air is ejected from the side to press coal chips into the center hole, but this cyclone jet drill bit has higher requirements on the sealing requirements of the drill pipe and the wind pressure of the compressed air. Due to the diameter of the drill pipe Smaller than the diameter of the drill bit, there is a large gap between the drill pipe and the inner wall of the drill hole, and the soft and protruding coal seam contains gas, which is easy to hide wind, resulting in a large wind loss when the wind pressure of the compressed air reaches the slag inlet of the cutter head, especially During the deep hole drilling operation, it is difficult to avoid the clogging of waste slag at the slag inlet of the center hole, resulting in problems such as stuck drill, buried drill and difficult discharge of cuttings at the bottom of the hole during the drilling process.

Contents of the invention

In view of this, the object of the present invention is to provide a kind of ejection type suction drilling tool for drilling center slag discharge in soft formation and its use method. The drilling tool jets into the central slag discharge channel through the high-pressure injection channel, forming a negative pressure area in the central slag discharge channel, and produces a suction effect on the drilling cuttings at the bottom of the drilling hole through the slag inlet hole on the side of the drill bit, and sucks the drilling cuttings into The slag discharge is carried out in the central slag discharge channel, and at the same time, the jet air ejected from the injection hole on the side of the cutter head is used to stir the bottom of the drilling hole, and push the drilling cuttings at the bottom of the hole to move into the slag inlet hole, so as to promote the cuttings at the bottom of the hole Enter the central slag discharge channel through the slag inlet hole, improve the slag inlet efficiency of the slag inlet hole, and solve the problems encountered in the drilling process of the existing coal seam gas pumping and drainage holes, such as stuck drill, buried drill and difficult slag discharge in the hole. Improve drilling efficiency and drilling depth.

In order to achieve the above-mentioned purpose, the present invention is an ejector type suction drilling tool for drilling into the center of slag discharge in soft formations, including an air inlet pipe, a slag discharge pipe, a power head and a double-layer center slag discharge drill connected to the power head rod, the air intake pipe and the slag discharge pipe are connected to the power head through a rotary joint, and the double-layer central slag discharge drill pipe is provided with a slag discharge channel communicated with the slag discharge pipe and an air intake channel communicated with the intake pipe, The front end of the double-layer central slag discharge drill pipe is equipped with an ejection type suction drill bit, and the ejection type suction drill bit is provided with a drill bit air intake channel communicated with the air intake channel, and a drill bit row communicated with the drill bit air intake channel. The air chamber, the drill bit exhaust passage communicated with the drill exhaust chamber, the slag inlet chamber communicated with the slag discharge passage and the slag inlet passage communicated with the slag inlet chamber, the end of the ejector suction drill bit is provided with not less than 3 cutting bits for drilling and sampling, the top side wall of the ejection suction drill bit is provided with a slag feeding hole, the slag feeding hole communicates with the slag feeding channel, the inner side wall of the cutting head There is an injection hole on the top, and the injection hole communicates with the exhaust channel of the drill bit. There is a high-pressure injection channel connected between the air intake channel of the drill bit and the slag feeding bin. for the same direction.

Further, there are no less than three high-pressure injection channels and they are evenly distributed in the ejector suction drill bit.

Further, there are no less than three slag inlet holes, which are respectively located in the middle between adjacent cutting bits.

Further, a vertical structure is set between the drill bit exhaust channel and the drill bit intake channel, an inclined structure is set between the drill bit exhaust chamber and the drill bit exhaust channel, and the upper surface of the cutting head is provided with a The gas chamber is connected and is used to process the process hole of the drill bit exhaust chamber.

Further, the power head is provided with an inner pipe of the main shaft of the power head and an outer pipe of the main shaft of the power head. The drill pipes are fixedly connected by the main shaft male joint and the drill pipe female joint. The threaded connection of the outer pipe of the rod and the plug-in sealing connection of the inner pipe of the drill pipe. hole.

Further, the double-layer central slag discharge drill pipe is fixedly connected to the ejector suction drill bit through a drill pipe male joint and a transition joint, and one end of the drill pipe male joint is threadedly connected to the drill pipe outer pipe and the drill pipe inner pipe at the same time. The pipe is plugged and sealed, and the other end is plugged and sealed with the ejection type suction drill bit. The two ends of the transition joint are respectively threaded with the drill pipe male joint and the ejection type suction drill bit. The drill pipe male joint and the transition An axial through hole I is arranged between the outer wall and the inner wall of the joint.

Further, the double-layer central slag discharge drill pipe is formed by assembling and connecting multiple drill pipes, drill pipe female joints and drill pipe male joints.

The present invention also discloses a method for using an ejector-type suction drilling tool for slag discharge in the center of drilling into soft formations, the steps of which are as follows:

1) Complete the installation and connection of the drilling rig, drilling tool and its slag discharge system, use the rotary joint to send compressed air into the air intake channel I in the power head, the drill pipe air intake channel, and the drill bit air intake channel respectively along the high-pressure injection channel and The exhaust channel of the drill bit is ejected, and the power head is connected with the outer drill pipe body and keeps rotating synchronously to realize rotary drilling;

2) After part of the pressurized air flow along the high-pressure injection channel, a negative pressure area is formed in the slag feeding bin, so that the slag feeding channel connected with the slag feeding bin produces a suction effect, which facilitates the cuttings formed by the drill bit breaking coal along the slag feeding The hole and the slag inlet channel are sucked into the slag inlet bin, and are sent into the slag discharge channel of the double-layer central slag discharge drill pipe under the action of the pressurized airflow, and the other part of the pressurized airflow is ejected along the drill bit exhaust channel, and the The drilling cuttings at the bottom of the hole generate agitation and send the drilling cuttings to the slag inlet hole, so that the drill cuttings can be sucked into the slag bin along the slag inlet hole and the slag inlet channel, and the slag discharge is completed in the drill pipe cavity, which can effectively Avoid the impact of drilling shrinkage, hole wall instability and collapse on the drilling slag discharge space;

3) The air flow returns the drill cuttings formed by the drill bit breaking coal along the slag discharge channel of the double-layer center slagging drill pipe and enters the slag discharge dust collector connected with the slag discharge pipe to complete slag discharge and dust removal. The drill cuttings migrate in the closed space to avoid Air leakage and dust leakage channels.

The beneficial effects of the present invention are:

1. The ejector type suction drilling tool of the present invention is used for drilling into the central slag discharge channel through the high-pressure injection channel to jet into the central slag discharge channel, forming a negative pressure area in the central slag discharge channel, and passing through the side of the drill bit. The slag inlet hole has a suction effect on the drill cuttings at the bottom of the drill hole, and the drill chips are sucked into the central slag discharge channel for slag discharge, and at the same time, the jet air ejected from the injection hole on the side of the cutter head produces agitation on the bottom of the drill hole. And push the cuttings at the bottom of the hole to migrate into the slag inlet hole, so that the cuttings at the bottom of the hole enter the central slag discharge channel through the slag inlet hole, improve the slag inlet efficiency of the slag inlet hole, and solve the problem of the existing coal seam gas drainage hole drilling process Problems such as stuck drill, buried drill and difficult slag discharge in the hole encountered in the process, greatly improve the drilling efficiency and drilling depth;

2. The ejector type suction drill pipe of the present invention is used for drilling in soft formations and the central slag discharge. The outer pipe adopts the male joint and the female joint to realize threaded fastening connection, and the inner pipe realizes centering and positioning by plugging. , and the sealing ring of the inner pipe is used to realize the sealing effect, so that the operation and installation of the drill pipe is simple, the sealing is reliable, and the drilling operation of deep drilling can be realized.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the cross-sectional view of the power part of the ejection type suction drilling tool used for drilling the central slag discharge in the soft stratum according to the present invention;

Fig. 2 is the cross-sectional view of the drill bit part of the ejection type suction drilling tool used for drilling the central slag discharge in soft formations according to the present invention;

Fig. 3 is the cross-sectional view of the drill bit in the ejector type suction drilling tool for drilling into the center of slag discharge in soft formations according to the present invention;

Fig. 4 is a perspective view of the drill bit in the ejector suction drilling tool used for drilling in soft formations for central slag discharge according to the present invention.

Description of drawings: 1-slag discharge pipe; 2-rotary joint; 3-intake pipe; 4-power head; 5-power head spindle inner tube; 6-power head spindle outer tube; 7-inner tube O-ring; 8-Spindle male joint; 9-Sealing ring; 10-Drill pipe female joint; 11-Drill pipe outer pipe; 12-Drill pipe inner pipe; 13-Drill pipe male joint; 14-Transition joint; 15-Injection pump Suction drill bit; 16-cutting head; 17-slag inlet channel; 18-slag inlet hole; 19-jet hole; 20-bit exhaust channel; 21-bit exhaust chamber; 22-drill bit air intake channel; Slag bin; 24-high pressure injection channel; 25-intake channel I; 26-intake channel II; 27-intake channel III; 28-intake channel of drill pipe female joint; 29-slag discharge channel; Air intake channel; 31 - air intake channel of drill pipe male joint; 32 - air intake channel of transition joint; 33 - negative pressure area; 34 - process hole.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, it is a cross-sectional view of the power part of the ejection type suction drilling tool used for drilling the central slag discharge in soft formations; The cross-sectional view of the drill bit of the formula suction drilling tool; as shown in Figure 3, it is a cross-sectional view of the drill bit in the ejection type suction drilling tool of the present invention for drilling into the center of slagging in soft formations; as shown in Figure 4, it is used for the present invention A three-dimensional view of the drill bit in the ejector type suction drilling tool for drilling into the center of slagging in soft formations. The present invention is an ejection type suction drilling tool for drilling into the center of slag removal in soft strata, including an air inlet pipe 3 and a slag discharge pipe 1. The power head 4 and the double-layer center slag discharge drill pipe connected to the power head 4, the air inlet pipe 3 and the slag discharge pipe 1 are connected to the power head 4 through the rotary joint 2, and the double-layer center slag discharge drill A slag discharge channel 29 communicating with the slag discharge pipe 1 and an air intake channel communicated with the intake pipe 3 are provided inside the rod. The front end of the double-layer center slag discharge drill pipe is equipped with an ejector type suction drill bit 15, and the ejector Type suction drill bit 15 is provided with the drill bit air intake passage 22 that communicates with the air intake passage, the drill bit exhaust chamber 21 that communicates with the drill bit air intake passage 22, the drill bit exhaust passage 20 that communicates with the drill bit exhaust chamber 21, and the drill bit exhaust chamber 20 that communicates with the exhaust chamber 21. The slag inlet bin 23 communicated with the slag inlet bin 29 and the slag inlet channel 17 communicated with the slag inlet bin 23, and the end of the ejection suction drill bit 15 is provided with no less than three cutting bits for drilling and sampling 16. A slag inlet hole 18 is provided on the top side wall of the injection type suction drill bit 15, and the slag inlet hole 18 communicates with the slag inlet channel 17, and an injection hole 19 is provided on the inner side wall of the cutting bit 16 , the injection hole 19 communicates with the drill bit exhaust channel 20, and the high-pressure injection channel 24 communicates between the drill bit air intake channel 22 and the slag-feeding bin 23, and the jetting direction of the high-pressure jetting channel 24 is consistent with the slag-feeding direction of the slag-feeding bin 23. Direction is set to the same direction.

In this embodiment, the high-pressure injection channel is used to jet the central slag discharge channel to form a negative pressure area in the central slag discharge channel, and the slag inlet hole on the side of the drill bit produces a suction effect on the drilling cuttings at the bottom of the drill hole, and the drilling cuttings are pumped out. The slag is discharged into the central slag discharge channel, and at the same time, the jet air ejected from the jet hole on the side of the cutter head is used to stir the bottom of the drill hole, and push the drilling cuttings at the bottom of the hole to migrate into the slag inlet hole, so as to promote the rock at the bottom of the hole The cuttings enter the central slag discharge channel through the slag inlet hole, improve the slag inlet efficiency of the slag inlet hole, and solve the problems encountered in the drilling process of the existing coal seam gas drainage hole, such as stuck drill, buried drill and difficult slag discharge in the hole. Greatly improve drilling efficiency and drilling depth.

Further, preferably, the high-pressure injection channels 24 are set to be no less than 3 and are evenly distributed in the ejection suction drill bit 15. This structure is conducive to forming a stable negative pressure area 33 in the slag feeding bin 23, which is convenient for pumping. Suction cuttings.

Further, preferably, the number of slag inlet holes 18 is set to be no less than three and are respectively located in the middle between adjacent cutting bits 16. This structure is conducive to improving the suction efficiency of drill chips and facilitates the removal of drill chips by the cutting bits. 16 slides into the area between the cutting bits 16 after cutting, and just in time is sucked into the slag discharge channel 29 along the slag inlet hole 18.

Further, preferably, the drill bit exhaust channel 20 and the drill bit air intake channel 22 are arranged in a vertical structure, and the drill bit exhaust chamber 21 and the drill bit exhaust channel 20 are arranged in an inclined structure, and the cutting bit 16 The upper surface is provided with a process hole 34 communicating with the drill bit exhaust chamber 21 and used for processing the drill bit exhaust chamber 21 .

Further, preferably, the power head 4 is provided with a power head main shaft inner tube 5 and a power head main shaft outer tube 6, and the double-layer central slag discharge drill pipe includes a drill pipe outer pipe 11 and a drill pipe inner pipe 12, and the power head The head 5 and the double-layer central slag discharge drill pipe are fixedly connected through the main shaft male joint 8 and the drill pipe female joint 10, and the main shaft male joint 8 is threadedly connected with the power head main shaft outer pipe 6 and inserted into the power head main shaft inner pipe 7 at the same time. The drill pipe female joint 10 is threadedly connected with the drill pipe outer pipe 11 and the drill pipe inner pipe 12 is plugged and sealed connected at the same time. Axial through holes are provided between the outer wall and the inner wall of the joint 8 and the drill pipe female joint 10. In this embodiment, the inner tube 5 of the main shaft of the power head and the male joint 8 of the main shaft realize the centering and positioning by plugging in, and the internal The pipe O-shaped sealing ring 7 realizes the sealing function, and the inner pipe 12 of the two-channel drill pipe, the male joint 13 of the two-channel drill pipe and the female joint 10 of the two-channel drill pipe all adopt the inserting method to realize the center positioning, and the sealing ring 9 is used to realize the sealing. The structure adopts the thread fastening connection of the outer pipe with the male joint and the female joint, and the inner pipe is centered and positioned by inserting, and the sealing ring of the inner pipe is used to realize the sealing effect, so that the operation and installation of the drill pipe are simple and the sealing is reliable. It can realize the drilling operation of deep drilling. After being used in combination with the ejector suction drill 15, it can ensure the airflow pressure and operation drilling intensity of the ejector suction drill 15, and greatly improve the drilling efficiency and drilling depth. .

Further, preferably, the double-layer central slag discharge drill pipe is fixedly connected to the ejector suction drill bit through a drill pipe male joint 13 and a transition joint 14, and one end of the drill pipe male joint 13 is connected to the drill pipe outer pipe 11 at the same time. The threaded connection is plugged and sealed with the drill pipe inner tube 12, and the other end is plugged and sealed with the ejector suction drill bit 15. The two ends of the transition joint 14 are respectively connected with the drill pipe male joint 13 and the ejected suction drill bit 15 Threaded connection, the drill pipe male joint 13 and the transition joint 14 are provided with an axial through hole I between the outer wall and the inner wall.

Further, preferably, the double-layer central slag discharge drill pipe is formed by assembling and connecting multiple drill pipes, drill pipe female joints 10 and drill pipe male joints 13, and multiple two-channel drill pipes pass through the two-channel drill pipe male joint 13 The screw thread on the top and the threaded connection on the two-channel drill pipe female joint 10 realize the lengthening of the two-channel drill pipe, and this structure is conducive to improving the drilling depth of the drill tool.

The present invention also discloses a method for using an ejector-type suction drilling tool for slag discharge in the center of drilling into soft formations, the steps of which are as follows:

1) Complete the installation and connection of the drilling rig, drilling tool and its slag discharge system, use the rotary joint to send compressed air into the air intake channel I in the power head, the drill pipe air intake channel, and the drill bit air intake channel respectively along the high-pressure injection channel and The exhaust channel of the drill bit is ejected, and the power head is connected with the outer drill pipe body and keeps rotating synchronously to realize rotary drilling;

2) After part of the pressurized air flow along the high-pressure injection channel, a negative pressure area is formed in the slag feeding bin, so that the slag feeding channel connected with the slag feeding bin produces a suction effect, which facilitates the cuttings formed by the drill bit breaking coal along the slag feeding The hole and the slag inlet channel are sucked into the slag inlet bin, and are sent into the slag discharge channel of the double-layer central slag discharge drill pipe under the action of the pressurized airflow, and the other part of the pressurized airflow is ejected along the drill bit exhaust channel, and the The drilling cuttings at the bottom of the hole generate agitation and send the drilling cuttings to the slag inlet hole, so that the drill cuttings can be sucked into the slag bin along the slag inlet hole and the slag inlet channel, and the slag discharge is completed in the drill pipe cavity, which can effectively Avoid the impact of drilling shrinkage, hole wall instability and collapse on the drilling slag discharge space;

3) The air flow returns the drill cuttings formed by the drill bit breaking coal along the slag discharge channel of the double-layer center slagging drill pipe and enters the slag discharge dust collector connected with the slag discharge pipe to complete slag discharge and dust removal. The drill cuttings migrate in the closed space to avoid Air leakage and dust leakage channels.

The principle of central slag discharge process: Driven by the power head 4, the drilling tool system realizes the drilling operation of the formation. During the drilling process, compressed air enters the rotary joint 2 through the intake pipe 3, and passes through the rotary joint 2 and the power head 4. Enter the air inlet passage I25, the air inlet passage II26, the air inlet passage III27, the drill pipe female joint inlet passage 28, the drill pipe inlet passage 30, the drill pipe male joint inlet passage 31, the transition joint inlet passage 32 and In the drill bit air intake channel 22, and in the drill bit air intake channel 22, it is divided into two jets and enters the high pressure injection channel 24 and the drill bit exhaust chamber 21 respectively. The air jet entering the high pressure injection channel 24 generates negative pressure in the slag intake chamber 23 , through the slag inlet passage 17, the drilling cuttings at the bottom of the drill hole are sucked, so that the drilling cuttings in the drilling hole are sucked into the slag discharge passage 29, and the air jet through the drill bit exhaust chamber 21 and the drill bit exhaust passage 20 Agitation is generated at the bottom of the hole, and the cuttings at the bottom of the hole are pushed to move into the slag feeding channel 17, and the cuttings at the bottom of the hole are forced to enter the slag discharge channel 29 through the slag feeding channel 17, and the compressed air after entering the slag discharge channel 29 carries the drill cuttings. The chips are discharged out of the hole through the power head 4, the rotary joint 2 and the slag discharge pipe 1, realizing the drilling process of central slag discharge.

In this embodiment, the air intake channel I25 is composed of an annular channel formed by the inner tube 5 of the main shaft of the power head and the outer tube 6 of the main shaft of the power head; the air intake channel II26 is composed of a plurality of axial round holes processed on the male joint 8 of the main shaft; The air channel III 27 is composed of the annular gap formed by the main shaft male joint 8 and the two-channel drill pipe female joint 10; the drill pipe female joint air inlet passage 28 is composed of a plurality of axial round holes processed on the two-channel drill pipe female joint 10; The slag discharge channel 29 is composed of the power head spindle inner tube 5, the main shaft male joint 8, the two-channel drill pipe female joint 10, the two-channel drill pipe inner tube 12, the two-channel drill pipe male joint 13, and the center of the ejector suction drill bit 15. Channel connections; the drill pipe inlet passage 30 is composed of the annular gap formed by the two-channel drill pipe inner pipe 12 and the two-channel drill pipe outer pipe 11; the drill pipe male joint inlet passage 31 is formed by the two-channel drill pipe male joint 13 It consists of a plurality of processed axial holes; the transition joint air inlet channel 32 is formed by the annular gap formed by the ejector suction drill bit 15 and the transition joint 14 .

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (2)

1. An ejector suction drilling tool for central slag discharge when drilling into soft formations, comprising an air inlet pipe, a slag discharge pipe, a power head and a double-layer center slag discharge drill pipe connected to the power head, the suction The air pipe and the slag discharge pipe are connected to the power head through a rotary joint, and it is characterized in that: the double-layer central slag discharge drill pipe is provided with a slag discharge channel connected with the slag discharge pipe and an air intake channel connected with the intake pipe, so The front end of the double-layer central slag discharge drill pipe is equipped with an ejection type suction drill bit, and the ejection type suction drill bit is provided with a drill bit air intake channel communicated with the air intake channel, and a drill bit exhaust air channel communicated with the drill bit air intake channel. bin, the drill bit exhaust passage connected with the drill bit exhaust chamber, the slag inlet chamber connected with the slag discharge passage, and the slag inlet passage connected with the slag inlet chamber. A cutting cutter head for drilling and sampling, the top side wall of the ejection type suction drill bit is provided with a slag inlet hole, the slag inlet hole communicates with the slag inlet channel, and the inner side wall of the cutting cutter head An injection hole is provided, and the injection hole communicates with the exhaust channel of the drill bit, and a high-pressure injection channel is communicated between the air intake channel of the drill bit and the slag inlet bin, and the injection direction of the high-pressure injection channel and the slag discharge direction of the slag inlet bin are set as same direction; The high-pressure injection channels are set to no less than 3 and are evenly distributed in the ejector suction drill bit; The number of said slag inlet holes is not less than 3 and they are respectively located in the middle between adjacent cutting heads; The drill bit exhaust channel and the drill bit air intake channel are arranged in a vertical structure, the drill bit exhaust chamber and the drill bit exhaust passage are arranged in an inclined structure, and the upper surface of the cutting head is provided with a drill bit exhaust chamber. Connected and used to process the process hole of the drill bit exhaust chamber; The power head is provided with a main shaft inner tube of the power head and an outer tube of the main shaft of the power head. The double-layer central slagging drill pipe includes a drill pipe outer pipe and a drill pipe inner pipe. The power head and the double-layer central slagging drill pipe They are fixedly connected by the main shaft male joint and the drill pipe female joint. Pipe thread connection and drill pipe inner pipe plug-in seal connection, the spindle male joint and the drill pipe female joint are matched and connected, and the outer wall and the inner wall of the spindle male joint and the drill pipe female joint are provided with axial through holes; The double-layer central slag discharge drill pipe is fixedly connected to the ejector suction drill bit through a drill pipe male joint and a transition joint. The other end is plugged and sealed with the ejection type suction drill bit. The two ends of the transition joint are respectively threaded with the drill pipe male joint and the ejection type suction drill bit. The drill pipe male joint and the transition joint An axial through hole I is arranged between the outer wall and the inner wall; The double-layer central slag discharge drill pipe is formed by assembling and connecting multiple drill pipes, drill pipe female joints and drill pipe male joints. 2. A method for using the ejection type suction drilling tool for drilling into the center of slag discharge in soft formations according to claim 1, characterized in that: 1) Complete the installation and connection of the drilling rig, drilling tool and its slag discharge system, use the rotary joint to send compressed air into the air intake channel I in the power head, the drill pipe air intake channel, and the drill bit air intake channel respectively along the high-pressure injection channel and The exhaust channel of the drill bit is ejected, and the power head is connected with the outer drill pipe body and keeps rotating synchronously to realize rotary drilling; 2) After part of the pressurized air flow along the high-pressure injection channel, a negative pressure area is formed in the slag feeding bin, so that the slag feeding channel connected with the slag feeding bin produces a suction effect, which facilitates the cuttings formed by the drill bit breaking coal along the slag feeding The hole and the slag inlet channel are sucked into the slag inlet bin, and are sent into the slag discharge channel of the double-layer central slag discharge drill pipe under the action of the pressurized airflow, and the other part of the pressurized airflow is ejected along the drill bit exhaust channel, and the The drilling cuttings at the bottom of the hole generate agitation and send the drilling cuttings to the slag inlet hole, so that the drill cuttings can be sucked into the slag bin along the slag inlet hole and the slag inlet channel, and the slag discharge is completed in the drill pipe cavity, which can effectively Avoid the impact of drilling shrinkage, hole wall instability and collapse on the drilling slag discharge space; 3) The air flow returns the drill cuttings formed by the drill bit breaking coal along the slag discharge channel of the double-layer center slagging drill pipe and enters the slag discharge dust collector connected with the slag discharge pipe to complete slag discharge and dust removal. The drill cuttings migrate in the closed space to avoid Air and dust leaks.