Flexible drill rod

Abstract

The invention discloses a flexible drill rod in the technical field of drill rods. An outer-layer drill rod is composed of an outer-layer connecting male buckle, a female buckle, a plurality of sets of connecting rod assemblies distributed circumferentially and a connecting ring. Each connecting rod assembly comprises a plurality of connecting rods distributed along the circumference, the adjacent assemblies are movably connected through connecting rings, and the connecting rod at the outermost end is fixed to the male buckle and the female buckle. First sealing layers cover the inner and outer walls of the connecting rod assembly and the connecting ring. Supporting frames are fixed in the male buckle and the female buckle, gaps are reserved, the supporting frames are connected with the inner-layer male buckle and the inner-layer female buckle respectively, and the supporting frames and the inner-layer male buckle and the inner-layer female buckle are connected through a deformable inner-layer drill rod to form an inner-layer closed channel with a through axis; the outer-layer closed channel is defined by a male buckle, a female buckle and an inner-layer elastic body, and a double-layer closed structure is achieved. According to the flexible drill rod, the drilling efficiency and safety can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of drill rods, and in particular relates to a flexible drill rod. Background Art

[0002] Flexible drill pipe is a special drill pipe used in drilling operations, especially in coal seam drilling for gas extraction. Made of high-strength alloy steel or composite materials, flexible drill pipe is able to bend and deform and then return to its original shape. Flexible drill pipe generally consists of two drill pipe joints and multiple drill pipe short sections connected end to end. The free ends of the two drill pipe short sections at the outermost ends are fixedly connected to the two drill pipe joints. Compared with traditional rigid drill pipe, flexible drill pipe can better adapt to complex geological conditions and drilling trajectory requirements during the drilling process. It can achieve directional drilling with a smaller bending radius, reduce the occurrence of accidents such as drill sticking and drill breakage, and improve the success rate and efficiency of drilling.

[0003] However, the existing flexible drill rods generally have the following problems: 1. After the flexible drill rod completes drilling, it is necessary to remove the flexible drill rod, seal the hole mouth, and then extract the gas; resulting in the inability to extract the gas during the drilling and flexible drill rod extraction period, which wastes a lot of time. 2. During the drilling process of the flexible drill rod, the soft coal seam, ground stress, coal body structure and other factors can easily cause the coal body around the borehole to break. The flexible drill rod will disturb the hole wall during drilling, which will destroy the original stress balance of the hole wall, reduce the stability of the hole wall, and cause the inner wall of the slag discharge channel (i.e., the hole wall) to collapse easily, thereby blocking the slag discharge channel and affecting the slag discharge effect. 3. The flexible drill rod is affected by factors such as coal seam stress and its own bending in the borehole, and the contact state with the hole wall will continue to change, resulting in different sizes of gaps between the two; a smaller gap will hinder the discharge of slag powder, and a larger gap will slow down the slag discharge speed and easily cause slag powder to accumulate in the hole. 4. Commonly used wind or hydraulic slag removal methods, when removing slag from the surface of a flexible drill pipe, have a high resistance to fluid flow in the irregular annular space between the drill pipe and the hole wall, making it difficult to form a stable and efficient slag removal flow field. Furthermore, as the drilling depth increases, the fluid pressure loss also increases, and the pressure and flow rate when reaching the bottom of the hole may not be sufficient to effectively discharge the slag powder. 5. Because the particle size of the slag powder cannot be completely uniform and may contain a lot of sticky substances, it is easy to form local blockages in the spiral grooves, grooves, and other parts of the drill pipe. Once local blockages are formed, the effective cross-sectional area of ​​the slag discharge channel will be reduced, thereby affecting the overall slag discharge efficiency and may even cause the pressure in the borehole to increase, leading to safety accidents.

[0004] Therefore, designing a flexible drill rod with a fixed slag discharge channel has positive significance for improving gas mining efficiency. Summary of the Invention

[0005] The present invention is intended to provide a flexible drill rod to solve the problems existing in the flexible drill rod in the above-mentioned background technology.

[0006] A flexible drill rod in the present scheme includes an outer drill rod, which includes an outer connecting pin buckle, an outer connecting female buckle and a movable skeleton movably connected therebetween, the movable skeleton is axially penetrated, and the outer wall and inner wall of the movable skeleton are covered with a first sealing layer that is wear-resistant, pressure-resistant, corrosion-resistant and tough; the outer connecting pin buckle and the outer connecting female buckle are axially penetrated and are fixedly connected to support frames inside, and gaps are left between the support frames and the outer connecting pin buckle and the outer connecting female buckle; the two support frames are respectively fixedly connected with an inner connecting pin buckle and an inner connecting female buckle, and the same deformable inner drill rod is fixedly connected between the inner connecting female buckle and the inner connecting pin buckle, and an inner sealed passage that is axially penetrated is formed between the inner connecting female buckle, the inner connecting pin buckle and the inner drill rod; an outer sealed passage that is axially penetrated is formed between the outer connecting pin buckle, the outer connecting female buckle and the inner first sealing layer.

[0007] This solution works as follows: When drilling, select an appropriate drill bit based on the geological conditions of the coal stratum and the drilling requirements. The drill bit and downhole motor are installed at the front end of the flexible drill pipe, which is connected to the pintle. The drilling rig is connected to the flexible drill pipe near the box end, and the box end is connected to a high-pressure water pump. Ensure a secure connection between the downhole motor and the flexible drill pipe, ensuring smooth transmission. During drilling, the flexible drill pipe, coupled to the high-pressure water pump, allows for both forward and reverse circulation drilling.

[0008] During positive circulation operation, the high-pressure blower pumps drilling media (such as high-pressure water, mud, high-pressure liquid fire-retardant foam / high-pressure gas) into the inner closed channel of the flexible drill pipe. The drilling media drives the bottom hole motor to work and enters the bottom of the hole through the drill bit. After carrying the drill cuttings, it returns to the hole mouth through the outer closed channel, forming a positive circulation of "inside in and out".

[0009] During reverse circulation operation, the high-pressure blower pumps the drilling medium (such as high-pressure water, mud, high-pressure liquid fire-retardant foam / high-pressure gas) into the closed channel on the outer layer of the flexible drill pipe. The drilling medium drives the bottom hole motor to work and enters the bottom of the hole through the drill bit. After carrying the drill cuttings, it returns to the hole mouth through the closed channel on the inner layer of the flexible drill pipe, forming a reverse circulation of "outside in and inside out".

[0010] Beneficial effects of this program:

[0011] 1. During positive circulation, the outer closed channel (i.e., the annulus between the outer and inner drill pipes) is relatively regular, reducing resistance to fluid flow. Compared to traditional flexible drill pipe, this facilitates the formation of a stable and efficient slag discharge flow field. Even with increased drilling depth, the improved flow field stability effectively controls fluid pressure loss, ensuring sufficient pressure and flow rate upon reaching the hole bottom, effectively discharging slag powder.

[0012] 2. During reverse circulation, the outer enclosed channel delivers high-pressure liquid fire-retardant foam and gas to cool and lubricate the drill bit, while the inner enclosed channel is used for slag removal. The discharged gas contains gas. This means that gas can be extracted during the drilling process, eliminating the need to wait until drilling is complete and the flexible drill pipe is removed before extracting the gas. This significantly saves time and improves the overall efficiency of gas extraction.

[0013] 3. During reverse circulation, the slag discharge channel of the flexible drill pipe is composed of an inner closed channel. Its relatively regular shape and stable structure ensure that even if the slag powder particle size is uneven or contains sticky substances, the effective cross-sectional area of ​​the slag discharge channel is not easily reduced due to local blockage, thereby maintaining the stability of the overall slag discharge efficiency and effectively avoiding safety accidents caused by increased pressure in the borehole.

[0014] 4. The combined design of a movable skeleton and a deformable inner drill pipe gives the flexible drill pipe exceptional toughness. During the drilling process, the flexible drill pipe can flexibly adjust the drilling angle and direction based on complex geological conditions and the drilling trajectory. Even in confined spaces and complex geological structures, the drill pipe can achieve directional drilling with a small bending radius, reducing the chances of accidents such as drill sticking and breakage, and significantly improving the drilling success rate. Furthermore, it effectively prevents slag discharge caused by changes in the contact between the drill pipe and the hole wall, ensuring smooth discharge of slag powder.

[0015] Furthermore, an outer steel mesh tube is fixedly mounted on the outer wall of the movable frame, and the first outer sealing layer is coated on the outer wall of the outer steel mesh tube. The outer steel mesh tube enhances the overall structural strength of the outer drill pipe, making it less susceptible to deformation or damage due to external forces under complex geological conditions. The first sealing layer, coated on the outer wall of the outer steel mesh tube, protects the outer steel mesh tube from wear and tear. Furthermore, by leveraging its toughness, it better adapts to deformation when the flexible drill pipe bends, maintaining the stability of the slag discharge channel. Furthermore, the outer steel mesh tube forms an integral constraint on the movable frame, preventing structural collapse in the event of local overload fracture.

[0016] Furthermore, the inner drill pipe includes an inner steel wire mesh tube and a second sealing layer coated on the inner and outer surfaces of the inner steel wire mesh tube and having toughness, wear resistance, pressure resistance, and corrosion resistance. The inner steel wire mesh tube provides a certain structural strength, allowing the inner drill pipe to maintain its shape when subjected to external forces and not be easily flattened or excessively deformed, thereby ensuring the normal use of the inner closed channel. The second sealing layer not only enhances the wear resistance of the inner drill pipe and reduces the wear on the inner wall of the inner drill pipe during the transportation of high-pressure liquid fire retardant foam and gas, but also, due to its toughness, can adapt to the bending deformation of the flexible drill pipe during the drilling process, avoiding damage caused by stress concentration caused by the rigid structure, thereby increasing the service life of the inner drill pipe.

[0017] Furthermore, the first sealing layer and / or the second sealing layer is a rubber layer, a special plastic layer or a thermoplastic elastomer layer, which has good toughness, wear resistance, pressure resistance and corrosion resistance.

[0018] Furthermore, the first and second sealing layers are both rubber layers. The first sealing layer is fixed to the outer steel mesh tube and the movable frame by vulcanization bonding; the second sealing layer is fixed to the inner steel mesh tube by vulcanization bonding. Through vulcanization bonding, the gaps between the outer steel mesh tube and the movable frame are filled and solidified with fluid rubber, significantly improving the sealing, connection strength, structural stability, wear resistance, and corrosion resistance of the outer drill pipe. The elasticity of the rubber layer enables the entire structure to adapt to a certain degree of deformation and displacement. When affected by external factors such as vibration, impact, or temperature changes, the rubber layer can act as a buffer and shock absorber. At the same time, the firmness of the vulcanization bonding ensures that the components will not slide or detach relative to each other during deformation, allowing the structure to operate normally under complex and changing working conditions. The vulcanization process is used to bond the steel mesh and rubber at the molecular level, eliminating the interface weaknesses of traditional glue bonding. The inner steel mesh is embedded in the rubber layer to form a "reinforced concrete" structure. When the flexible drill rod is bent, the interface stress is evenly dispersed to avoid delamination and cracking, making it particularly suitable for frequent bending conditions.

[0019] Furthermore, the inner wall of the second sealing layer of the inner layer is provided with spiral blades made of rubber material with toughness, wear resistance, pressure resistance, and corrosion resistance. The spiral blades are integrally formed on the second sealing layer by vulcanization bonding. The spiral blades produce a swirl effect when conveying drill cuttings, causing the fluid to propel along the axial direction of the flexible drill pipe rather than being driven by simple pressure. This active conveying method can reduce fluid pressure loss and is particularly suitable for long-distance drilling. At the same time, the rotating flow can prevent slag powder from depositing on the inner wall of the flexible drill pipe and avoid clogging of the internal channel. When reverse circulation slag discharge is blocked or the drill is stuck, the drilling rig drives the flexible drill pipe to rotate, and the spiral blades are used to facilitate slag discharge and prevent drill sticking.

[0020] Furthermore, the outer wall of the first outer sealing layer is provided with spiral grooves. These grooves alter the fluid flow between the outer drill pipe and the hole wall, guiding the gas carrying drill cuttings during slag removal into a more orderly spiral flow, thereby enhancing slag removal. Furthermore, the spiral grooves also increase the friction between the outer drill pipe and the hole wall to a certain extent, making the flexible drill pipe less susceptible to relative slippage due to, for example, coal seam stress during drilling, thereby improving its stability within the hole. If slag removal is obstructed or the drill becomes stuck, the drill rig rotates the flexible drill pipe, using the spiral grooves to facilitate slag removal and prevent drill sticking.

[0021] Furthermore, the movable framework includes multiple groups of connecting rod assemblies and connecting rings located between adjacent connecting rod assemblies. Each connecting rod assembly includes multiple connecting rods, and the multiple connecting rods in a group are distributed along the circumference. The connecting rods of two adjacent connecting rod assemblies are movably connected by connecting rings. The ends of the outermost connecting rods, away from the connecting rings, are movably connected to the outer connecting pin and outer connecting box buckles, respectively. The movable framework is composed of multiple connecting rod assemblies and multiple connecting rings. During the drilling process, if a connecting rod breaks due to impact, the wire mesh can temporarily bear the load, maintaining the shape of the slag discharge channel until the current drilling cycle is completed, significantly improving the fault tolerance of the flexible drill pipe.

[0022] Furthermore, both ends of the connecting rod are provided with through holes extending through the thickness of the rod. The through holes at both ends of multiple connecting rods in the same group are connected in series by a fixed rope, and the head and tail ends of the fixed rope are fixedly connected. Multiple connecting blocks are circumferentially distributed on both sides of the connecting ring, and the ends of the connecting rods are located between adjacent connecting blocks. Fixed ropes are connected in series between multiple connecting rods and connecting blocks located in the same circumferential direction. The use of fixed ropes in series with the connecting rods allows a deflection angle of 0° to 30° between adjacent connecting rings, while maintaining circumferential rigidity through rope tension. Compared to a purely hinged structure, this design can provide the necessary torsional rigidity during vertical drilling, preventing the flexible drill rod from spinning out of control in the hole.

[0023] Furthermore, the number of connecting blocks on one side of the connecting ring is no less than the number of connecting rods in the same group. The connecting blocks on both sides of the connecting ring are provided with through slots and / or connection holes. The fixing ropes are connected to the through slots and / or through holes of the corresponding connecting blocks, and the connecting rods are located between adjacent connecting blocks on the connecting ring. The through slots and / or connection holes, combined with the fixing ropes, allow for easy connection of the connecting rods to the connecting ring, making operation simple.

[0024] Furthermore, the outer walls of the opposite ends of the outer connecting male buckle and the outer connecting female buckle are both provided with constrictions, and the ends are also provided with multiple connecting blocks distributed along the circumference. The connecting blocks are not less than the number of connecting rods in the same group, and the connecting blocks are also provided with through grooves and / or connecting holes. The fixing ropes on the connecting rod assemblies at both ends are connected to the through grooves and / or through holes of the corresponding connecting blocks, and the connecting rods are located between adjacent connecting blocks on the connecting ring. The two ends of the outer layer steel wire mesh tube are respectively sleeved on the constrictions of the outer walls of the outer layer connecting male buckle and the outer layer connecting female buckle, and the outer layer first sealing layer is fixed to the outer walls of the outer layer connecting male buckle and the outer layer connecting female buckle. The constriction design on the outer layer connecting male buckle and the outer layer connecting female buckle facilitates the installation and fixation of the outer layer steel wire mesh tube, so that it fits tightly with the outer layer connecting male buckle and the outer layer connecting female buckle, thereby enhancing the stability of the overall structure. The connection block, through-slot, and connection hole, combined with the fixed rope on the connecting rod assembly, achieve a flexible connection between the outer drill rod and the outer connecting pin and box buckles, enabling the flexible drill rod to flexibly adapt to different drilling trajectories during drilling. Furthermore, a first sealing layer secured to the outer walls of the outer connecting pin and box buckles further protects the connection, improving wear resistance and sealing.

[0025] Furthermore, the through-slots on the connecting blocks on either side of the connecting ring face inward and outward of the blocks, respectively, or the through-slots on multiple connecting blocks on the same side face alternately inward and outward. This distribution of through-slots allows for greater flexibility and variety in the attachment locations of the retaining ropes on the connecting blocks. When the flexible drill pipe bends and deforms, the retaining ropes in different locations can better coordinate with each other, adapting to the deformation requirements and preventing damage to the connection points due to uneven force on the retaining ropes. This design also increases the redundancy of the connection structure, improving the reliability and stability of the outer drill pipe under complex working conditions.

[0026] Furthermore, the outer female connector also has a constriction on the end away from the outer male connector. A retaining ring is located at this constriction, and the retaining ring is evenly distributed with multiple grooves. The outer wall of the outer female connector is provided with multiple stepped grooves that cooperate with the grooves. Wedges are located within the stepped grooves and extend into the corresponding grooves. The retaining ring and wedges at the constriction cooperate to provide a locking and sealing effect.

[0027] Furthermore, friction pads are mounted on both the inner connecting pin and box, located at the junction between the inner connecting pin and box and the support frame. These pads increase friction between the inner connecting pin and box and the support frame, preventing relative displacement of the inner drill pipe due to vibration or stress during operation. Furthermore, the pads act as a buffer, reducing the impact force transmitted from the inner drill pipe to the support frame, protecting the connection between the support frame and the inner drill pipe, extending the service life of the connecting components, and ensuring the stability and reliability of the inner sealed passage.

[0028] In this application, the fixing rope is made of steel wire rope, such as high-carbon steel 82B or 72A, or rope with similar properties. The thickness of the first and second sealing layers is 3-8 mm. The thickness of the outer steel mesh and inner steel mesh tube is 3-8 mm. After vulcanization and bonding, the first and second sealing layers are both tubular. The inner diameter of the inner second sealing layer is 60-120 mm, and the diameter of the outer steel mesh tube is 160-210 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a front view of a flexible drill rod according to embodiment 1 of the present invention;

[0030] Figure 2 for Figure 1 AA section view;

[0031] Figure 3 for Figure 2 A three-dimensional diagram of the middle connecting ring and the connecting block after connection;

[0032] Figure 4 for Figure 2 A three-dimensional diagram of the middle and outer layer connecting female buckles;

[0033] Figure 5 for Figure 2 Another perspective view of the connecting female buckle of the middle and outer layers;

[0034] Figure 6 for Figure 2 A three-dimensional diagram of the middle support frame;

[0035] Figure 7 for Figure 2 A three-dimensional diagram of the middle retaining ring;

[0036] Figure 8 for Figure 2 Three-dimensional view of the middle connecting rod

[0037] Figure 9 for Figure 2 Schematic diagram of the structure after the middle connecting rod assembly is connected to the connecting ring;

[0038] Figure 10 for Figure 2 Enlarged view of point B;

[0039] Figure 11 for Figure 2 Enlarged view of point C. DETAILED DESCRIPTION

[0040] The following is further described in detail through specific implementation methods:

[0041] The figure marks in the drawings of the specification include: outer layer connecting male buckle 1, connecting rod 2, connecting ring 3, fixing rope 4, first sealing layer 5, outer layer wire mesh tube 6, outer layer connecting female buckle 7, connecting tube 71, stepped groove 72, outer shrinkage 73, inner shrinkage 74, support frame 8, circular ring 81, support block 82, retaining ring 9, groove 91, wedge block 10, friction pad 11, inner layer connecting female buckle 12, inner layer wire mesh tube 13, second sealing layer 14, spiral blade 15, spiral groove 16, inner layer connecting male buckle 17, fixing ring 18, connecting block 19, through groove 20.

[0042] Example 1 is basically as shown in the attached Figures 1 to 11 As shown: a flexible drill pipe, including an outer connecting pin buckle 1, an outer connecting female buckle 7, an inner connecting pin buckle 17, an inner connecting female buckle 12, an outer drill pipe, an inner drill pipe and two support frames 8; the outer connecting pin buckle 1 and the outer connecting female buckle 7 are arranged opposite to each other and the main bodies are both connecting tubes 71 that pass through in the axial direction, the outer connecting pin buckle 1 and the outer connecting female buckle 7 have outer constrictions 73 on the outer walls of the opposite ends and the ends are integrally formed with eight connecting blocks 19 along the circumference, and the connecting blocks 19 are each provided with a through groove 20, the through groove 20 on the connecting block 19 connected to the outer connecting pin buckle 1 is arranged on its inner side, and the through groove on the connecting block 19 connected to the outer connecting female buckle 7 is arranged on its inner side. 20 is arranged on its outside, and the inner wall of the outer layer connecting male buckle 1 is integrally formed with a fixing ring 18 coaxial with it, and the end of the outer layer connecting male buckle 1 away from the outer layer connecting female buckle 7 is a retracted conical surface; the inner part of the outer layer connecting female buckle 7 away from the end of the outer layer connecting female buckle 7 is provided with an inwardly retracted opening 74, and a retaining ring 9 is provided at the inwardly retracted opening 74, and four grooves 91 are evenly distributed on the retaining ring 9. Four stepped grooves 72 for use with the grooves 91 are provided on the outer wall of the connecting tube 71 of the outer layer connecting female buckle 7, and the stepped groove 72 passes through the connecting tube 71. The cross-section of the stepped groove 72 is square, and a wedge block 10 is provided in the stepped groove 72, which extends into the corresponding groove 91.

[0043] The inner layer connecting male buckle 17 and the inner layer connecting female buckle 12 are arranged opposite to each other, and the axial direction of the inner layer connecting male buckle 17 is passed through. Both ends of the inner layer connecting male buckle 17 are provided with neckings. The end close to the inner layer connecting female buckle 12 is provided with two neckings and is stepped, and the end away from the inner layer connecting female buckle 12 is provided with three neckings and is stepped. For the convenience of description, the five neckings on the inner layer connecting male buckle 17 are named as the first necking, the second necking, the third necking, the fourth necking, and the fifth necking from left to right; the axial direction of the inner layer connecting female buckle 12 is passed through and has a stepped hole inside. The inner layer connecting female buckle 12 is also provided with two neckings and is stepped at the end close to the inner layer connecting male buckle 17, and the inner layer connecting female buckle 12 is also provided with a necking at the end away from the inner layer connecting male buckle 17. For the convenience of description, the three neckings on the inner layer connecting female buckle 12 are named as the sixth necking, the seventh necking, and the eighth necking from left to right.

[0044] The outer drill pipe includes an outer steel wire mesh tube 6, two first sealing layers 5 covered on the inner and outer surfaces of the outer steel wire mesh tube 6, six groups of connecting rod 2 assemblies and connecting rings 3 located between adjacent connecting rod 2 assemblies, each group of connecting rod 2 assemblies includes eight connecting rods 2, and the eight connecting rods 2 of the same group are distributed along the circumference. Both ends of the connecting rods 2 are provided with chamfers, and both ends of the connecting rods 2 are provided with through holes running through their thickness directions. The opposite ends of the connecting rods 2 of the two adjacent groups of connecting rod 2 assemblies are movably connected to the corresponding connecting rings 3, specifically: the through holes at both ends of the eight connecting rods 2 of the same group are respectively connected in series by a fixed rope 4, and the fixed rope 4 is a steel rope, and the head and tail ends of the fixed rope 4 are fixedly connected; eight connecting blocks 19 are distributed along the circumference on both side walls of the connecting ring 3, and the connecting blocks 19 on both sides of the connecting ring 3 are provided with through grooves 20, and the through grooves 20 on one side of the connecting ring 3 are located on the outside of the corresponding connecting block 19, and the through grooves 2 on the other side of the connecting ring 3 0 is located on the inner side of the corresponding connecting block 19; the fixing rope 4 is clamped in the through groove 20 of the corresponding connecting block 19, the connecting rod 2 is located between the adjacent connecting blocks 19 on the connecting ring 3, and the six groups of connecting rod 2 components and the five connecting rings 3 and the corresponding connecting blocks 19 form a movable skeleton through the fixing rope 4. The movable skeleton and the outer layer of steel wire mesh tube 6 are located between the two first sealing layers 5, and the first sealing layer 5 is made of wear-resistant rubber material; the movable skeleton, the outer layer of steel wire mesh tube 6 and the first sealing layer 5 are fixed by vulcanization bonding. Specifically: the outer layer of steel wire mesh tube 6 is meshed on the movable skeleton, and then the wear-resistant rubber material is bonded to the outer wall of the outer layer of steel wire mesh tube 6 and the inner wall of the movable skeleton by a vulcanization bonding process. The wear-resistant rubber material fills the gap between the outer layer of steel wire mesh tube 6 and the movable skeleton, and forms a first sealing layer 3 to 8 mm thick on the outer wall of the outer layer of steel wire mesh tube 6 and the inner wall of the movable skeleton; a spiral groove 16 is provided on the outer wall of the outer first sealing layer 5.

[0045] The length of the inner first sealing layer 5 is greater than the length of the outer first sealing layer 5 and the length of the outer steel wire mesh tube 6 and the length of the movable frame. The outer wall of the inner first sealing layer 5 that exceeds the movable frame is fixed to the inner wall of the outer connecting male buckle 1 and the inner wall of the outer connecting female buckle 7 by vulcanization bonding, and the inner first sealing layer 5 extends to the inner shrinkage 74 of the outer connecting female buckle 7. The inner wall of the outer first sealing layer 5 that exceeds the outer steel wire mesh tube 6 is fixed to the outer wall of the outer connecting male buckle 1 and the outer connecting female buckle 7 by vulcanization bonding, and the outer first sealing layer 5 Extending to the conical surface of the outer connecting male buckle 1; the part of the outer steel wire mesh tube 6 that exceeds the movable frame is respectively sleeved and fixed to the outer shrinkage 73 of the outer connecting male buckle 1 and the outer connecting female buckle 7 through vulcanization bonding of the outer first sealing layer 5; the fixing ropes 4 on the free ends of the connecting rods 2 of the two groups of connecting rods 2 assemblies at both ends of the movable frame are respectively clamped in the through grooves 20 of the outer connecting male buckle 1 and the outer connecting female buckle 7; an outer closed passage that passes through in the axial direction is formed between the outer connecting male buckle 1, the outer connecting female buckle 7 and the inner first sealing layer 5.

[0046] The inner drill rod includes an inner steel mesh tube 13 and a second sealing layer 14 covered on the inner and outer walls of the inner steel mesh tube 13. The second sealing layer 14 is made of wear-resistant rubber material. The inner steel mesh tube 13 and the second sealing layer 14 are fixed by vulcanization bonding. Specifically: the wear-resistant rubber material is bonded to the inner and outer walls of the inner steel mesh tube 13 by a vulcanization bonding process. The wear-resistant rubber material fills the gaps on the inner steel mesh tube 13 and forms a second sealing layer 3 to 8 mm thick on the inner and outer walls of the inner steel mesh tube 13. The inner steel mesh tube 13 is coaxial with the second sealing layer 14. A spiral blade 15 is provided on the inner wall of the inner second sealing layer 14. The length of the outer second sealing layer 14 is greater than the length of the inner steel wire mesh tube 13 and the length of the inner second sealing layer 14; the inner wall of the outer second sealing layer 14 exceeding the inner steel wire mesh tube 13 is fixed to the outer walls of the inner connecting male buckle 17 and the inner connecting female buckle 12 by vulcanization bonding, that is, fixed at the fourth and seventh shrinkages, and the portion of the inner steel wire mesh tube 13 exceeding the inner second sealing layer 14 is fixed to the outer walls of the inner connecting male buckle 17 and the inner connecting female buckle 12 by vulcanization bonding of the outer second sealing layer 14, that is, fixed at the fifth and sixth shrinkages; the two ends of the inner second sealing layer 14 are fixed to the opposite ends of the inner connecting male buckle 17 and the inner connecting female buckle 12 by vulcanization bonding; an inner closed passage, i.e., an inner passage, which passes through in the axial direction is formed between the inner connecting female buckle 12, the inner connecting male buckle 17 and the inner steel mesh tube 13.

[0047] The two support frames 8 both include a circular ring 81 and three integrally formed support blocks 82 evenly distributed on the outer wall of the circular ring 81. The inner diameters of the fixing ring 18 and the retaining ring 9 are both larger than the outer diameter of the circular ring 81, and the inner diameters of the fixing ring 18 and the retaining ring 9 are both smaller than the outer diameter of the circular ring 81 plus the length of the support blocks 82; the inner diameter of the circular ring 81 is smaller than the maximum outer diameter of the inner layer connecting male buckle 17 and the inner layer connecting female buckle 12; the circular rings 81 of the two support frames 8 are respectively sleeved on the third and eighth shrinkages, and friction pads 11 are provided at the connections between the circular rings 81 and the third and eighth shrinkages; the side of the circular ring 81 connected to the inner layer connecting male buckle 17 away from the inner layer connecting female buckle 12 abuts against the side wall of the fixing ring 18, and the side of the circular ring 81 connected to the inner layer connecting female buckle 12 away from the inner layer connecting male buckle 17 abuts against the side wall of the retaining ring 9; the ends of the support blocks 82 of the two support frames 8 both abut against the inner wall of the inner first sealing layer 5.

[0048] The only difference between Example 2 and Example 1 is that the through grooves 20 are alternately arranged on the inner and outer sides of the connecting block 19 on the same side.

[0049] The only difference between Example 3 and Example 1 is that the eight connecting blocks 19 on the same side are alternately provided with through slots 20 and connecting holes.

[0050] Taking Example 1 as an example, the specific implementation process is as follows:

[0051] Select an appropriate drill bit based on the geological conditions of the coal formation and the drilling requirements. Install the drill bit and downhole motor at the front end of the flexible drill pipe, which is the end connected to the outer connecting pin 1. Connect the drilling rig to the flexible drill pipe near the connecting box, and connect the high-pressure air blower to the connecting box. Ensure that the downhole motor is securely connected to the flexible drill pipe and that the transmission is smooth.

[0052] During drilling operations, the flexible drill rod, coupled with a high-pressure air blower, enables both forward and reverse circulation drilling. During forward circulation, high-pressure liquid fire-retardant foam and gas are delivered to the drill bit through the inner, sealed channel. The spiral blades 15 on the inner wall of the second inner sealing layer 14 create a swirling flow, enabling more efficient delivery to the drill bit. This swirling flow not only accelerates delivery but also reduces pressure loss during delivery, ensuring adequate cooling and lubrication when the fluid reaches the drill bit.

[0053] During the drilling process, the drill bit produces cuttings, which are carried by high-pressure gas through the cutting discharge channel into the annular gap of the outer sealed channel and returned to the surface. Because the outer wall of the first sealing layer 5 of the outer drill pipe is provided with spiral grooves 16, an orderly spiral flow is formed under the guidance of the spiral grooves 16 when the drill is stuck, preventing the drill pipe from being stuck by the hole wall. The spiral grooves 16 also increase the friction between the outer drill pipe and the hole wall, making the flexible drill pipe less susceptible to relative sliding due to factors such as coal seam stress during the drilling process, thereby improving the stability of the flexible drill pipe within the hole. Even if the contact state between the outer drill pipe and the hole wall changes due to factors such as coal seam stress during the drilling process, the first sealing layer 5 can adaptively adjust through its own elastic deformation.

[0054] During reverse circulation, a high-pressure blower pumps high-pressure liquid fire-retardant foam and high-pressure gas into the drill pipe through a sealed channel on the outer surface. This drilling medium drives the bottomhole motor and enters the hole through the drill bit. It then returns to the surface through the sealed channel on the inner surface of the flexible drill pipe, carrying drill cuttings with it, creating an "outside-in, inside-out" reverse circulation system. External circulation offers the following advantages: 1. High slag removal efficiency: The high flow rate in the inner sealed channel effectively carries large rock cuttings, reduces re-fracture at the bottom of the hole, and improves drilling efficiency. It is suitable for deep holes or complex formations (such as fractured zones and well-developed fractured formations), as it provides a short slag removal path with low resistance. 2. Excellent hole wall stability: The flushing medium enters the hole through the outer sealed channel, minimizing scouring effects on the hole wall and reducing the risk of hole collapse. 3. High safety: The closed slag removal system reduces gas and dust emissions, making it suitable for mines with high gas content or explosive environments. 4. Excellent drilling quality: Rock cuttings are discharged directly from the inner sealed channel, minimizing sample contamination and ensuring more accurate sampling.

[0055] The specific use of positive circulation and reverse circulation is based on comprehensive considerations such as the depth of the drilling hole, the ground conditions, and the gas content.

[0056] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A flexible drill rod, comprising an outer drill rod, the outer drill rod comprising an outer connecting male buckle, an outer connecting female buckle and a movable frame movably connected therebetween, characterized in that: The movable skeleton is penetrated in the axial direction, and the outer wall and the inner wall of the movable skeleton are covered with a first sealing layer that is wear-resistant, pressure-resistant, corrosion-resistant and tough; the outer layer connecting male buckle and the outer layer connecting female buckle are penetrated in the axial direction and are fixedly connected to support frames inside, and gaps are left between the support frames and the outer layer connecting male buckle and the outer layer connecting female buckle; the two support frames are respectively fixedly connected with the inner layer connecting male buckle and the inner layer connecting female buckle, and the same deformable inner layer drill rod is fixedly connected between the inner layer connecting female buckle and the inner layer connecting male buckle, and an inner layer closed passage that is penetrated in the axial direction is formed between the inner layer connecting female buckle, the inner layer connecting male buckle and the inner layer drill rod; an outer layer closed passage that is penetrated in the axial direction is formed between the outer layer connecting male buckle, the outer layer connecting female buckle and the inner layer first sealing layer.

2. A flexible drill rod according to claim 1, characterized in that: An outer steel wire mesh tube is fixedly sleeved on the outer wall of the movable frame, and the first outer sealing layer is coated on the outer wall of the outer steel wire mesh tube.

3. A flexible drill rod according to claim 2, characterized in that: The inner drill pipe comprises an inner steel wire mesh tube and a second sealing layer which is coated on the inner and outer surfaces of the inner steel wire mesh tube and has the properties of toughness, wear resistance, pressure resistance and corrosion resistance.

4. A flexible drill rod according to claim 3, characterized in that: The first sealing layer and / or the second sealing layer is a rubber layer, a special plastic layer or a thermoplastic elastomer layer.

5. A flexible drill rod according to claim 4, characterized in that: The first sealing layer and the second sealing layer are both rubber layers. The first sealing layer is fixed to the outer steel wire mesh tube and the movable frame by vulcanization bonding; the second sealing layer is fixedly connected to the inner steel wire mesh tube by vulcanization bonding.

6. A flexible drill rod according to claim 5, characterized in that: The inner wall of the second sealing layer of the inner layer is provided with a spiral blade made of rubber material with toughness, wear resistance, pressure resistance and corrosion resistance. The spiral blade is integrally formed on the second sealing layer by vulcanization bonding and fixing.

7. A flexible drill rod according to claim 6, characterized in that: The outer wall of the first sealing layer of the outer layer is provided with a spiral groove.

8. A flexible drill rod according to any one of claims 1 to 7, characterized in that: The movable skeleton includes multiple groups of connecting rod assemblies and connecting rings located between adjacent connecting rod assemblies, each group of connecting rod assemblies includes multiple connecting rods, and the multiple connecting rods in the same group are distributed along the circumference. The connecting rods of two adjacent groups of connecting rod assemblies are movably connected through connecting rings, and the ends of the outermost connecting rods away from the connecting rings are movably connected to the outer layer connecting male buckle and the outer layer connecting female buckle respectively.

9. A flexible drill rod according to claim 8, characterized in that: Both ends of the connecting rod are provided with through holes penetrating the thickness direction thereof, and the through holes at both ends of multiple connecting rods of the same group are respectively connected in series by a fixing rope, and the head and tail ends of the fixing rope are fixedly connected; multiple connecting blocks are circumferentially distributed on both sides of the connecting ring, and the ends of the connecting rods are located between adjacent connecting blocks, and the fixing ropes are connected in series between multiple connecting rods and connecting blocks located in the same circumferential direction.

10. A flexible drill rod according to claim 9, characterized in that: The number of connecting blocks on the same side of the connecting ring is not less than the number of connecting rods in the same group, and the connecting blocks on both sides of the connecting ring are provided with through grooves and / or connecting holes; the fixing rope is connected to the through grooves and / or through holes of the corresponding connecting blocks, and the connecting rods are located between adjacent connecting blocks on the connecting ring.

11. A flexible drill rod according to claim 10, characterized in that: The outer walls of the opposite ends of the outer layer connecting male buckle and the outer layer connecting female buckle are provided with neckings and the ends are also provided with multiple connecting blocks distributed along the circumference. The connecting blocks are not less than the number of connecting rods in the same group, and the connecting blocks are also provided with through grooves and / or connecting holes; the fixing ropes on the connecting rod assemblies at both ends are connected to the through grooves and / or through holes of the corresponding connecting blocks, and the connecting rods are located between adjacent connecting blocks on the connecting ring; the two ends of the outer layer steel wire mesh tube are respectively sleeved on the neckings of the outer layer connecting male buckle and the outer layer connecting female buckle outer wall, and the outer first sealing layer is fixed on the outer wall of the outer layer connecting male buckle and the outer layer connecting female buckle.

12. A flexible drill rod according to claim 11, characterized in that: The openings of the through slots on the connecting blocks on both sides of the connecting ring face the inside and outside of the connecting blocks respectively, or the openings of the through slots on multiple connecting blocks on the same side face the inside and outside of the connecting blocks alternately.

13. A flexible drill rod according to claim 12, characterized in that: The inner part of one end of the outer layer connecting female buckle away from the outer layer connecting male buckle is also provided with a necking, and a retaining ring is provided at the necking, and a plurality of grooves are evenly distributed on the retaining ring. The outer wall of the outer layer connecting female buckle is provided with a plurality of stepped grooves used in conjunction with the grooves, and a wedge block is provided in the stepped groove, and the wedge block extends into the corresponding groove.

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