A method for assembling and forming large-diameter borehole sections in coal mines

Abstract

This invention discloses a method for assembling and drilling large-diameter boreholes in coal mines, comprising a borehole reaming drill bit, multiple drill rods, and a water supply device connected in sequence. A centralizer is installed between some adjacent drill rods. The borehole reaming drill bit consists of a separate main body and an auxiliary drill bit body. The auxiliary drill bit body is axially movable on a sliding shaft. During retraction, the assembly acts like a piston, collecting sediment from the borehole and mechanically ejecting it outside the hole, creating favorable conditions for casing placement in different borehole configurations. Furthermore, the radial winglets of the main body and auxiliary drill bit body are misaligned with the guide groove, and the overall outer contour is cylindrical. During rotary drilling and axial pushing / pulling, the winglets of the drill bit body do not significantly damage the formation on the lower borehole wall, facilitating casing placement. The casing placement success rate can reach over 95%, solving the technical problems of complex multi-stage borehole reaming drill bit assemblies, large workload for drill bit replacement, and low efficiency in existing large-diameter boreholes.

Description

Technical Field

[0001] This invention belongs to the field of underground drilling in coal mines, and relates to a hole-reaming drill bit, specifically a combination of hole-reaming drill bits and a hole-forming method for large-diameter hole sections in underground coal mines. Background Technology

[0002] In coal mine drilling projects, most boreholes for gas control and water hazard prevention require borehole casing sealing to meet the needs of gas and water inflow control during drilling, as well as subsequent negative pressure extraction, drainage, and high-pressure grouting. For multi-branch directional long boreholes, pre-drilling casing sealing is usually required (i.e., before implementing directional drilling with measurement while drilling, a sealing section is constructed, a certain length of casing is installed and sealed, and directional drilling is carried out only after it passes inspection). The quality of casing sealing is crucial for the safe construction and efficient use of the borehole. On the one hand, it is a basic measure to prevent abnormal gas and formation water outflow during directional drilling and ensure construction safety; on the other hand, it is a basic prerequisite for fully utilizing the function of the directional borehole and achieving the expected project objectives.

[0003] Underground coal mine boreholes are typically designed with different opening directions based on varying engineering purposes. In cross-section, the sealing section's orientation can be categorized into three typical forms: near-horizontal, upward-sloping, and downward-sloping. Unlike most surface boreholes where the sealing section is vertically downward, the unique orientation of the sealing section in underground coal mine boreholes significantly impacts the ease of pipe laying operations due to the quality of the borehole formation. Currently, the sealing section of conventional large-diameter boreholes and directional boreholes in underground coal mines primarily employs a "pilot hole drilling + multi-stage reaming drilling" process. This method is rational: constructing a small-diameter pilot hole first facilitates straight drilling, and subsequent multi-stage reaming reduces the demands on drilling rig capabilities and allows for the creation of large-diameter boreholes using small equipment.

[0004] With the continuous improvement of conventional rotary drilling and directional drilling technology and equipment in coal mines, and the continuous improvement of automation and intelligence levels, the number of large-diameter and deep boreholes with a construction diameter of more than 200mm is increasing. The technology and equipment for directional drilling of 200mm diameter boreholes in a single operation has become increasingly sophisticated and has begun to be promoted and applied on a large scale, with the maximum enlarged diameter exceeding 300mm. The amount of conventional large-diameter boreholes being constructed is also increasing, and these boreholes have higher requirements for casing sealing. The increased diameter and depth of the sealing section in directional drilling in coal mines have brought new technical challenges to drilling operations: First, large-diameter reaming drilling presents difficulties in hydraulic slag removal, poor borehole cleaning, and sediment on the lower side of the borehole wall, leading to high resistance in pipe running and making it difficult to guarantee the pipe running depth. Second, during the retraction and pullback of large-diameter drill bits, the prismatic blades often damage the formation on the lower side of the borehole wall, producing "pseudo-drill cuttings." These technological factors reduce the regularity and integrity of the borehole wall in the sealing section, further increasing the difficulty and complexity of pipe running and reducing the quality of sealing. Third, due to limitations in hydraulic slag removal capacity, the multi-stage reaming drill bit combination in large-diameter sections is complex, resulting in a large workload and low efficiency in changing drill bits. Finally, during the reaming process in large-diameter sealing sections, the large stage difference between the drill rod and the borehole wall, the difficulty in adding and disassembling existing centralizers, poor compatibility, and decreased overall timeliness of drilling operations all contribute to the challenges. Currently, there is a lack of efficient and rapid drilling tool combinations and hole-forming methods suitable for conventional large-diameter holes and directional holes with large diameters and long sealing sections in underground coal mines. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for assembling and forming large-diameter borehole sections in coal mines, so as to solve the technical problems of complex multi-stage borehole reaming drill bit assemblies, large workload and low efficiency of drill bit replacement in existing large-diameter borehole sections.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A large-diameter borehole reaming drill assembly for coal mines includes a reaming drill bit, multiple drill rods, and a water supply device connected in sequence, with a centralizer provided between some adjacent drill rods. The reaming drill bit includes a sliding shaft, an auxiliary drill bit body movably sleeved in the middle of the sliding shaft, a limiting short section sleeved at the axial rear end of the sliding shaft, a reaming drill bit body sleeved at the axial front end of the sliding shaft, a fixed sleeve sleeved at the axial front end of the reaming drill bit body, an axial rear end of a ball-head hinge shaft disposed within the fixed sleeve, and a guide short section disposed at the axial front end of the ball-head hinge shaft.

[0008] The axial front end face of the fixed sleeve is evenly provided with multiple U-shaped grooves, and the inner cavity of the fixed sleeve is a connected spherical cavity and a conical cavity.

[0009] The reaming drill bit body includes a main body, on which multiple ribs are evenly arranged on the axial front end face. Each rib has a PDC composite piece of different diameter welded on its front end face. A guide groove is formed between adjacent ribs along the axial direction. A ball socket is provided in the middle of the main body. A plugging ball seat is provided at the axial rear end of the main body and communicates with the ball socket. A bottom flow channel is formed on the inner wall of the plugging ball seat and is evenly distributed along the circumference. The bottom flow channel includes a radial hole and an axial hole that are connected and evenly distributed along the circumference. The axial hole communicates with the outside of the reaming drill bit body.

[0010] The sliding shaft includes a first cylinder. Multiple guide keys are evenly spaced along the circumference on the outer wall of the first cylinder. The guide keys are provided with a first flow groove and a second flow groove of different depths that are connected. A radial flow channel is provided in the second flow groove, and the radial flow channel connects the inner cavity of the first cylinder, the first flow groove and the second flow groove.

[0011] The auxiliary drill bit body includes a second cylinder, and auxiliary ribs are uniformly arranged at the axial front end of the outer wall of the second cylinder. The auxiliary ribs correspond one-to-one with the guide grooves of the reaming drill bit body in the circumferential direction. Carbide cutting teeth are arranged at the axial rear end of the auxiliary ribs.

[0012] The circumferential width of the auxiliary wing is greater than the width of the guide groove on the main body of the reaming drill bit, and the circumferential width of the auxiliary guide groove is less than the width of the wing on the main body of the reaming drill bit.

[0013] The inner wall of the second cylinder is provided with multiple guide keyways at equal intervals along the circumference, and the multiple guide keyways correspond one-to-one with multiple guide keys on the outer wall of the sliding shaft; a connecting groove is provided on the inner wall of the second cylinder, and the connecting groove communicates with the guide keyways.

[0014] The inner wall of the second cylinder has a sliding cavity at its axial rear end, and multiple liquid flow holes are uniformly formed along the circumferential direction on the side wall of the sliding cavity.

[0015] This invention also includes the following technical features:

[0016] The straightener includes a front rod and a rear rod connected together; a plurality of straightening wings are sleeved at the connection between the front rod and the rear rod, and the plurality of straightening wings form a cylinder.

[0017] The front rod body includes a mounting rod body. The outer wall of the mounting rod body is provided with a plurality of dovetail grooves and a plurality of rectangular grooves arranged alternately along the circumference. A third mounting groove is provided on the outer wall of the mounting rod body. The third mounting groove is perpendicular to and communicates with the dovetail grooves and the plurality of rectangular grooves. A central flow channel is provided inside the front rod body.

[0018] The rear rod body includes a connecting and supporting section and a limiting frustum connected along the axial direction. The outer diameter of the connecting and supporting section is the same as that of the drill rod, and the outer diameter of the limiting frustum is the same as that of the mounting rod body of the front rod body. A central channel is opened inside the rear rod body.

[0019] Each of the straightening wings has a straight rib plate at both ends of its inner wall along the circumference. The straight rib plate is located in the rectangular groove. A dovetail rib plate is provided in the middle of the inner wall of the straightening wing. The dovetail rib plate is located in the dovetail groove. A limit groove is provided on the dovetail rib plate, and a limit block is provided in the limit groove.

[0020] A locking hole is provided in the limiting groove; a limiting hole is provided on the limiting block, and a bolt is provided in both the limiting hole and the locking hole.

[0021] The limiting block includes a rectangular block and a sector block. The rectangular block mates with the limiting groove on the straightening wing; the sector block mates with the third mounting groove on the front rod.

[0022] The outer wall of the first cylinder is stepped with an increasing diameter along the axial direction, and the outer wall of the axial rear end of the first cylinder is conical.

[0023] The rear end face of the prism of the reaming drill bit body is provided with a conical surface, and the front end face of the auxiliary prism of the auxiliary drill bit body is provided with a conical surface at the same angle as the rear end face of the prism.

[0024] The straightening wing has multiple windows.

[0025] A method for forming a borehole in a large-diameter borehole section in a coal mine, based on the aforementioned borehole reaming drill bit assembly, specifically includes the following steps:

[0026] Step 1: Use a small-diameter drill bit and drill rod to drill a pilot hole to the designed depth, then withdraw the drill rod and small-diameter drill bit in sequence;

[0027] Step 2: Insert the guide section of the reaming drill bit into the pilot hole obtained in Step 1, start the mud pump, and high-pressure water enters the water feeder through the pipeline. After the high-pressure water reaches the bottom of the hole, it cools the PDC composite plate and carries the drill cuttings back out of the borehole.

[0028] Step 3: After enlarging the hole to a certain depth, observe the slag return at the hole opening and perform mechanical slag removal in the local section of the hole.

[0029] The local borehole section drilling and slag removal mechanism uses a piston body composed of an auxiliary drill bit body and a reaming drill bit body to collect the drill cuttings deposited in the reamed section and push them out of the hole;

[0030] Step 4: Re-drill and continue enlarging the hole. Depending on the length of the enlarged section and the amount of slag returned during the enlargement process, repeat Step 3 at certain intervals until the hole is enlarged to the predetermined depth, resulting in a large-diameter borehole.

[0031] Step 5: Pull back the large-diameter borehole section reaming drill bit assembly in the coal mine over a short distance and rotate it slowly so that the auxiliary drill bit body and the reaming drill bit body fit together to form an assembly. Insert the plugging ball into the center hole of the drill rod and flush it with water to the bottom of the borehole into the reaming drill bit body.

[0032] Step 6: Start retracting the drill bit. The reaming drill bit collects the slag in the borehole at its rear end and discharges it mechanically. When the resistance to retracting the drill bit increases significantly during the process, turn on the mud pump to inject water into the hole, agitate and flush away the drill slag accumulated at the rear end of the reaming drill bit, and continue retracting the drill bit until the reaming drill bit body is removed from the hole, thus completing the slag removal and hole formation.

[0033] Step 7: Insert the casing into the obtained large-diameter borehole and seal it with grout as needed.

[0034] It also includes: attaching a centralizer to the drill rod at regular intervals inside the hole and sending it into the hole to continue reaming and drilling.

[0035] Compared with the prior art, the beneficial technical effects of this invention are:

[0036] (I) The reaming drill bit of this invention consists of a separate reaming drill bit body and an auxiliary drill bit body. The auxiliary drill bit body is axially movable and displaceable on the sliding shaft. During the retraction process, the assembly is 'piston' shaped, which can collect the sediment in the borehole and discharge it to the outside of the hole by mechanical ejection, creating favorable conditions for the casing to be laid in different hole sections with different postures. The overall casing laying efficiency can be improved by more than 30%. In addition, the radial wing of the reaming drill bit body and the auxiliary drill bit body are misaligned with the guide groove, and the overall outer contour is a cylindrical surface. During rotary drilling and axial pushing and pulling, the wing of the drill bit body will not cause significant damage to the formation on the lower side of the hole wall, will not produce 'false drill cuttings', can maintain the relative integrity of the hole wall and the regular cross section, and has a more obvious protective effect on the hole wall in softer strata, which is conducive to the laying of casing. The casing laying success rate can reach more than 95%, which solves the technical problems of complex combination of existing multi-stage reaming drill bits for large-diameter holes, large workload and low efficiency of drill bit replacement.

[0037] (II) The centralizer of the drill bit assembly of the present invention is a modular structure, which is mechanically assembled and disassembled with the drill rod. It has the characteristics of flexibility, high efficiency and low labor intensity. Compared with the integrated structure, the connection and disassembly efficiency is increased by more than 50%. The 'variable diameter' feature can adapt to the hole enlargement construction requirements of drill holes of different diameters.

[0038] (III) The drilling tool assembly of this invention enables one-time drilling and reaming of conventional large-diameter boreholes, large-diameter directional boreholes, and long-distance sealing sections in coal mines. The hole-forming quality is high, and the speed is fast, meeting the requirements for lowering sealing pipes with diameters of 200mm or more. Furthermore, this method has low requirements for flushing fluid discharge. Utilizing the special assembly structure and the drilling rig's pulling-out capability, sediment in the hole is mechanically discharged to the outside through retraction, allowing for progressive deep-hole reaming. This eliminates the need for multi-stage reaming drilling and the disassembly and replacement of different drill tool assemblies, reducing the workload by more than 30%. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a coal mine large-diameter hole enlarging drill assembly according to the present invention;

[0040] Figure 2(a) is a schematic diagram of the drilling state of the large-diameter reaming drill bit of the present invention;

[0041] Figure 2(b) is a schematic diagram of the retraction state of the large-diameter reaming drill bit of the present invention;

[0042] Figure 3 This is a schematic diagram of the fixing sleeve structure of the large-diameter reaming drill bit of the present invention;

[0043] Figure 4 This is a schematic diagram of the main structure of the large-diameter reaming drill bit of the present invention;

[0044] Figure 5 This is a schematic diagram of the sliding shaft structure of the large-diameter reaming drill bit of the present invention;

[0045] Figure 6 This is a schematic diagram of the auxiliary drill bit body structure for the large-diameter reaming drill bit of the present invention;

[0046] Figure 7 This is a schematic diagram of the centralizer structure for the large-diameter borehole reamer of the present invention;

[0047] Figure 8 This is a schematic diagram of the front rod structure of the straightener of the present invention;

[0048] Figure 9 This is a schematic diagram of the straightening wing structure of the straightening device of the present invention;

[0049] Figure 10 This is a schematic diagram of the positioning block structure of the straightening device of the present invention;

[0050] Figure 11 This is a schematic diagram of the rear rod structure of the drill string assembly and matching stabilizer of the present invention;

[0051] Figure 12 This is a schematic diagram of the principle of a combination of slag removal and hole forming for large-diameter borehole enlargement drill in coal mines according to the present invention;

[0052] The labels in the diagram represent: 1-reamer bit, 2-centralizer, 3-drill rod, 4-water feeder, 5-sealing ball, 6-pilot borehole, 7-large diameter borehole, 8-borehole wall sediment, 9-formation;

[0053] 101-Guide short section, 102-Ball head hinge shaft, 103-Fixing sleeve, 104-Reamer body, 105-Sliding shaft, 106-Auxiliary drill body, 107-Limiting short section;

[0054] 1031 - Inner conical surface, 1032 - U-shaped groove, 1033 - Inner spherical surface;

[0055] 1041-Prism, 1042-Guide groove, 1043-Bottom flow channel, 1044-Spherical socket, 1045-Blocking ball seat, 1046-PDC composite piece, 1047-Convex conical surface;

[0056] 1051-Guide key, 1052-First flow channel, 1053-Radial flow channel, 1054-Second flow channel, 1055-Central flow channel, 1056-First cylinder;

[0057] 1061-Auxiliary prism, 1062-Guide keyway, 1063-Auxiliary flow channel, 1064-Sliding cavity, 1065-Liquid flow hole, 1066-Concave cone surface, 1067-Connecting groove, 1068-Carbide cutting tooth; 1069-Second cylinder;

[0058] 201-Front rod body, 202-Straightening wing, 203-Bolt, 204-Limiting block, 205-Rear rod body;

[0059] 2011 - Mounting rod, 2012 - First mounting slot, 2013 - Second mounting slot, 2014 - Central flow channel, 2015 - Third mounting slot;

[0060] 2022 - Window, 2023 - Limiting groove, 2024 - Straight rib plate, 2025 - Dovetail rib plate, 2026 - Locking hole;

[0061] 2041 - Rectangular block, 2042 - Sector-shaped block, 2043 - Limiting hole;

[0062] 2051 - Connecting and blessing section, 2052 - Central channel, 2053 - Limiting round platform.

[0063] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0064] It should be noted that, unless otherwise specified, all components in this invention are those known in the art.

[0065] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0066] See Figures 1-6 The present invention provides a drilling tool assembly for large-diameter boreholes in coal mines, comprising a borehole reaming drill bit 1, multiple drill rods 3 and a water supply device 4 connected in sequence, with a centralizer 2 provided between some adjacent drill rods 3;

[0067] Referring to Figure 2, the reaming drill bit 1 includes a sliding shaft 105, an auxiliary drill bit body 106 is movably sleeved in the middle of the sliding shaft 105, a limiting short section 107 is sleeved at the axial rear end of the sliding shaft 105, a reaming drill bit body 104 is sleeved at the axial front end of the sliding shaft 105, a fixing sleeve 103 is sleeved at the axial front end of the reaming drill bit body 104, the axial rear end of a ball joint hinge shaft 102 is provided inside the fixing sleeve 103, and a guide short section 101 is provided at the axial front end of the ball joint hinge shaft 102.

[0068] See Figure 3 The axial front end face of the fixed sleeve 103 is evenly provided with multiple U-shaped grooves 1032, and the inner cavity of the fixed sleeve 103 is a spherical cavity 1033 and a conical cavity 1031 that are connected.

[0069] See Figure 4 The reaming drill bit body 104 includes a body, a plurality of ribs 1041 are evenly arranged on the axial front end face of the body, and PDC composite pieces 1046 with different diameters are arranged on the front end face of each rib 1041. A guide groove 1042 is formed between adjacent ribs 1041 along the axial direction. A ball socket 1044 is arranged in the middle of the body, and a sealing ball seat 1045 communicating with the ball socket 1044 is arranged at the axial rear end of the body. A bottom flow channel 1043 is evenly distributed in the circumferential direction on the inner wall of the sealing ball seat 1045. The bottom flow channel 1043 includes a radial hole and an axial hole that are connected and evenly distributed in the circumferential direction. The axial hole communicates with the outside of the reaming drill bit body 104.

[0070] See Figure 5 The sliding shaft 105 includes a first cylinder 1056. Multiple guide keys 1051 are evenly spaced along the circumference on the outer wall of the first cylinder 1056. The guide keys 1051 are provided with a first flow groove 1052 and a second flow groove 1054 of different depths that are connected. A radial flow channel 1053 is provided in the second flow groove 1054. The radial flow channel 1053 connects the inner cavity of the first cylinder 1056, the first flow groove 1052 and the second flow groove 1054.

[0071] See Figure 6The auxiliary drill bit body 106 includes a second cylinder 1069. The outer front end of the second cylinder 1069 is uniformly provided with auxiliary ribs 1061. The auxiliary ribs 1061 correspond one-to-one with the guide grooves 1042 of the reaming drill bit body 104 in the circumferential direction. The rear end of the auxiliary ribs 1061 is provided with carbide cutting teeth 1068.

[0072] The circumferential width of the auxiliary prism 1061 is greater than the width of the guide groove 1042 on the reaming drill bit body 104, and the circumferential width of the auxiliary guide groove 1063 is less than the width of the prism 1041 on the reaming drill bit body 104.

[0073] Multiple guide keyways 1062 are provided at equal intervals along the circumference on the inner wall of the second cylinder 1069. The multiple guide keyways 1062 correspond one-to-one with multiple guide keys 1051 on the outer wall of the sliding shaft 105. A connecting groove 1067 is provided on the inner wall of the second cylinder 1069, and the connecting groove 1067 communicates with the guide keyways 1062.

[0074] The inner wall of the second cylinder 1069 has a sliding cavity 1064 at its axial rear end, and a plurality of liquid flow holes 1065 are evenly provided on the side wall of the sliding cavity 1064 along the circumferential direction.

[0075] In the above technical solution, during the drilling state of the reaming drill bit 1, the auxiliary drill bit body 106 and the reaming drill bit main body 104 are axially separated, and the guide groove 1042 and the auxiliary guide groove 1063 are axially connected. During the retraction state of the reaming drill bit 1, due to the movement of the auxiliary drill bit body 106, the auxiliary guide groove 1063 of the auxiliary drill bit body 106 coincides with the wing 1041 of the reaming drill bit main body 104, and the guide groove 1042 of the reaming drill bit main body 104 coincides with the auxiliary wing 1061 of the auxiliary drill bit body 106, thus the guide groove 1042 and the auxiliary guide groove 1063 are axially shut off. Multiple guide keyways 1062 arranged axially on the inner side of the auxiliary drill bit body 106 cooperate with the guide key 1051 on the outer surface of the sliding shaft 105 to meet the requirements of axial sliding and circumferential torque transmission.

[0076] The U-shaped groove 1032 is used to rotate the fixed sleeve 103 so that it can be connected and disassembled with the reamer body 104 by threads; the conical cavity 1031 is used to limit the floating range of the guide section 101 and the ball joint shaft 102; the spherical cavity 1033 is used to cooperate with the ball joint shaft 102 to realize the conical swing function.

[0077] PDC composite sheet 1046 is used for cutting and crushing rock during borehole enlargement drilling; guide groove 1042 is a flow channel for drilling circulating water; ball socket 1044 is used to install ball head hinge shaft 102; bottom flow channel 1043 serves as a flow channel for water to flush the enlarged rock crushing surface and cool PDC composite sheet 1046.

[0078] The number of auxiliary winglets 1061 is the same as the number of winglets in the main body 104 of the reaming drill bit. The carbide cutting teeth 1068 at the rear end of the auxiliary winglets 1061 are used to assist in hole repair during the retraction process.

[0079] The auxiliary drill bit body has a circumferentially arranged connecting groove 1067 on its inner side, which serves as a water flow channel to ensure reliable sliding of the auxiliary drill bit; the inner rear end of the auxiliary drill bit body 106 has a sliding cavity 1064, which cooperates with the limiting short section 107 to achieve axial sliding and limiting; the side wall of the sliding cavity 1064 has a liquid flow hole 1065, which is used to assist in slag removal during the drill retraction process.

[0080] See Figure 12 The structure of the large-diameter borehole reaming drill bit assembly in coal mines is 'water feeder 4 + N × drill rod 3 + centralizer 2 + N × drill rod 3 + ... + reaming drill bit 1'. Drilling proceeds along the pilot hole 6 to form a large-diameter hole 7 at the designed depth. Before retraction, a sealing ball 5 is inserted through the central channel of the drill bit, and water is used to flush the water to the ball seat of the reaming drill bit 1 at the bottom of the hole, sealing the downward flow of water. During retraction, the reaming drill bit 1 uses a 'piston' action principle to collect the borehole wall sediment 8 and mechanically pushes it out of the hole. When the pulling force increases during retraction, a water feeder 4 is connected to the drill rod string to inject high-pressure water into the hole. With the cooperation of the sealing ball 5, the water flows directly into the annulus through the rear end of the combined reaming drill bit 1, cooperating with the rotation of the drill bit to agitate and disperse the drill cuttings accumulated at the rear end of the drill bit, carrying the cuttings upwards and reducing the resistance to drilling.

[0081] After the reaming drill bit 1 is pulled out, the drill cuttings deposited on the lower side of the hole are discharged to the outside of the hole. During the mechanical slag removal process using the reaming drill bit 1, its cylindrical 'piston' structure will not damage the formation 9 on the lower side of the hole wall during the drilling process, and can maintain the regularity of the hole wall, which is conducive to the lowering of the casing.

[0082] The reaming drill bit consists of a separate reaming drill bit body 104 and an auxiliary drill bit body 106. The auxiliary drill bit body is axially movable and displaceable on the sliding shaft 105. During the retraction process, the assembly is 'piston' shaped, which can collect the sediment in the borehole and discharge it to the outside of the hole by mechanical ejection. This creates favorable conditions for running casing in different hole sections with different postures, and the overall casing running efficiency can be improved by more than 30%. In addition, the radial wing of the reaming drill bit body 104 and the auxiliary drill bit body 106 is misaligned with the guide groove, and the overall outer contour is cylindrical. During rotary drilling and axial push-pull, the wing of the drill bit body will not cause significant damage to the formation on the lower side of the hole wall, will not produce 'false drill cuttings', and can maintain the relative integrity of the hole wall and the regular cross section. The protection effect of the hole wall in softer formations is more obvious, which is conducive to running casing. The success rate of running casing can reach more than 95%. This solves the technical problems of complex assembly of existing multi-stage reaming drill bits for large-diameter holes, large workload and low efficiency of drill bit replacement.

[0083] This invention also includes the following technical features:

[0084] See Figure 7 , Figure 8 , Figure 9 and Figure 11 The straightener 2 includes a front rod 201 and a rear rod 202 connected together; a plurality of straightening wings 202 are sleeved at the connection between the front rod 201 and the rear rod 202, and the plurality of straightening wings 202 form a cylinder.

[0085] The front rod body 201 includes a mounting rod body 2011. Multiple dovetail grooves 2012 and multiple rectangular grooves 2013 are arranged alternately along the circumferential direction on the outer wall of the mounting rod body 2011. A third mounting groove 2015 is formed on the outer wall of the mounting rod body 2011. The third mounting groove 2015 is perpendicular to and communicates with the dovetail grooves 2012 and the multiple rectangular grooves 2013. A central flow channel 2014 is formed inside the front rod body 201.

[0086] The rear rod body 202 includes a connecting and supporting section 2051 and a limiting frustum 2053 connected along the axial direction. The outer diameter of the connecting and supporting section 2051 is the same as that of the drill rod 3. The outer diameter of the limiting frustum 2053 is the same as that of the mounting rod 2011 of the front rod body 201. A central channel 2052 is provided inside the rear rod body 202.

[0087] Each straightening wing 202 has a straight rib plate 2024 at both ends of its inner wall in the circumferential direction. The straight rib plate 2024 is located in a rectangular groove 2013. A dovetail rib plate 2025 is provided in the middle of the inner wall of the straightening wing 202. The dovetail rib plate 2025 is located in a dovetail groove 2012. A limiting groove 2023 is provided on the dovetail rib plate 2025. A limiting block 204 is provided in the limiting groove 2023.

[0088] See Figure 7 , 8 9 and Figure 11 The central angle corresponding to a single straightening wing 202 is 120°, and its diameter corresponds to the diameter of the enlarged hole;

[0089] The central channel 2014 serves as a channel for water flow and pitching; the central channel 2052 also serves as a channel for water flow and pitching.

[0090] A locking hole 2026 is provided in the limiting groove 2023, and a limiting hole 2043 is provided on the limiting block 204. A bolt 203 is provided in both the limiting hole 2043 and the locking hole 2026.

[0091] In the above technical solution, a locking hole 2026 is provided at the corresponding position of the limiting groove 2023 for installing bolts 203.

[0092] When disassembling the centralizer 2 during drill retraction, first remove the bolt 203 and take off the limit block 204, then remove and remove the centralizer wing 202 from the first mounting slot 2012 and the second mounting slot 2013 of the front rod body 201; the assembly of the front rod body 201 and the rear rod body 205 is disassembled by the drilling rig through the connecting clamp rod body 2051.

[0093] The limiting block 204 includes a rectangular block 2041 and a sector block 2042. The rectangular block 2041 cooperates with the limiting groove 2023 on the straightening wing 202; the sector block 2042 cooperates with the third mounting groove 2015 on the front rod body 201.

[0094] In the above technical solution, the limiting block 204 is used to axially limit the straightening wing 202 on the front rod body 201.

[0095] The outer wall of the first cylinder 1056 is stepped with an increasing diameter along the axial direction, and the outer wall of the axial rear end of the first cylinder 1056 is conical.

[0096] In the above technical solution, it is used as a mating surface corresponding to the auxiliary drill bit body 106.

[0097] The rear end face of the wing 1041 of the reaming drill bit body 104 is provided with a conical surface, and the front end face of the auxiliary wing 1061 of the auxiliary drill bit body 106 is provided with a conical surface at the same angle as the rear end face of the wing 1041.

[0098] In the above technical solution, when the reaming drill bit 1 is in the retracted state, the conical surface of the auxiliary drill bit body 106 coincides with the conical surface of the reaming drill bit body 104 and the two are attached together, and the guide groove 1042 and the auxiliary guide groove 1063 are axially shut off.

[0099] The Fuzheng Wing 202 has multiple windows 2022.

[0100] In the above technical solution, the window 2022 is set up to provide operating space for the disassembly and assembly of the limit block 204, and to reduce weight.

[0101] Example:

[0102] This embodiment provides a method for forming holes in large-diameter boreholes in coal mines using a combination of drilling tools, including the following steps:

[0103] Step 1: Use a small-diameter drill bit and drill rod to drill a pilot hole to the designed depth, then withdraw the drill rod and small-diameter drill bit in sequence;

[0104] Step 2: Using the ball joint 102, fixed sleeve 103, and limiting short section 107, assemble and connect the guide short section 101, the reaming drill bit body 104, the sliding shaft 105, and the auxiliary drill bit body 106 together. Connect the drill rod 3 and the water supply device 4 to the limiting short section 107. Place the guide short section 101 into the pilot hole 6, start the mud pump to supply water circulation, rotate the drill rod 3, and drive the reaming drill bit body 104 and the auxiliary drill bit body 106 to rotate synchronously. Under the guidance of the guide short section 101, the drill advances along the pilot hole 6. During the reaming drilling process, due to the frictional resistance of the hole wall, the auxiliary drill bit body 106 axially separates from the reaming drill bit body 104, and the auxiliary drill bit body 106... The sliding cavity 1064 is occupied by the limiting short section 107, and the water flow channel of the fluid flow hole 1065 is closed. Most of the circulating water that reaches the central flow channel 1055 of the sliding shaft 105 through the central flow channel of the drill bit 105 flows out through the bottom flow channel 1043 on the reaming drill bit body 104. It cools the PDC composite plate 1046 and carries the drill cuttings through the guide groove 1042 and the auxiliary guide groove 1063 into the borehole annulus and returns. A small part of the circulating water enters the first flow channel 1052 and the connecting groove 1067 on the auxiliary drill bit body 106 through the radial flow channel 1053 of the sliding shaft 105 and then flows out from the space between the auxiliary drill bit body 106 and the reaming drill bit body 104, which can prevent drill cuttings from entering the guide keyway 1062.

[0105] Step 3: During the hole enlargement process, at intervals of 10m to 15m, attach the front rod body 201 and the rear rod body 205 of the centralizer to the drill rod 3 inside the hole. Then, attach the three centralizer wings 202 into the first mounting groove 2012 and the second mounting groove 2013 of the front rod body 201 through the straight rib plate 2024 and the dovetail rib plate 2025, and make the end face of the centralizer wing 202 fit against the end face of the upper limit frustum 2053 of the rear rod body 205. Install the three limit blocks 204 on the front rod body 201 through the window 2022 on the centralizer wing 202. The third mounting groove 2015 on the 01 is inserted, and the limiting hole 2043 on the limiting block 204 is aligned with the locking hole 2026 on the straightening wing 202. The bolt 203 is tightened, and the rectangular block 2041 of the limiting block 204 is located in the limiting groove 2023 of the straightening wing 202, and the fan-shaped block 2042 of the limiting block 204 is located in the third mounting groove 2015 of the front rod 201 of the straightener, so as to achieve axial positioning of the straightening wing 202 and the front rod 201. Then, the drill rod 3 is added to the rear rod 201 of the straightener, and the hole is enlarged and drilled.

[0106] Step 4: During the partial slag removal and inclined borehole expansion, the drill bit can be withdrawn at intervals of 15m to 30m borehole depth, taking into account the slag return situation at the borehole opening during the expansion drilling process, to perform mechanical slag removal in the partial borehole section. During the withdrawal process, under the action of reverse frictional resistance, the auxiliary drill bit body 106 slides relative to the guide key 1051 on the sliding shaft 105 and fits together with the main body of the expansion drill bit 104. That is, the front cone surface of the auxiliary drill bit body 106 coincides with the rear cone surface of the main body of the expansion drill bit 104. The auxiliary wing 1061 and auxiliary guide groove 1063 of the auxiliary drill bit body 106 correspond to the guide groove 1042 and wing 1041 of the expansion drill bit body 104, blocking the axial flow channel and forming a 'piston' body, so as to perform one-time efficient mechanical slag removal for the large-diameter borehole section.

[0107] Step 5: After removing slag from the partially drilled hole, drill again to continue enlarging the hole. Depending on the length of the enlarged section and the amount of slag returned during the enlargement process, Step 4 can be repeated at certain intervals until the predetermined depth is reached.

[0108] Step 6: Drill Retraction and Hole Formation Before drilling, a sealing ball 5 is inserted into the center channel of drill rod 3 and flushed with water to the sealing ball seat 1045 inside the reaming drill bit body 104 at the bottom of the hole to seal the flow channel 1043 at the bottom of the hole. During drilling, the reaming drill bit body 104 and the auxiliary drill bit body 106 are in contact. At this time, the limiting short section 107 exits from the sliding cavity 1064 of the reaming drill bit body 106, and the water flow channel of the fluid flow hole 1065 is opened. The reaming drill bit body 104 and the auxiliary drill bit body 106 act in a 'piston' manner. The principle is to collect the borehole sediment 8 at the rear end of the reaming drill bit 1 and push it towards the borehole opening; when the drilling force increases during the retraction of the drill bit, a water supply device 4 is connected to the drill rod string 3 to inject circulating water into the hole. The circulating water that reaches the reaming drill bit 1 through the central flow channel of the drill rod 3 all enters the sliding cavity 1064 of the auxiliary drill bit body 106 through the radial flow channel 1053 and the second flow channel 1054 of the sliding shaft 105, and then flows out through the liquid flow hole 1065, stirring and dispersing the borehole sediment 8 accumulated at the rear end of the reaming drill bit 1, thereby reducing the retraction resistance.

[0109] Step 7: Lowering and sealing the casing. Lower the casing into the large-diameter borehole and seal it with grout as needed.

[0110] When removing the centralizer 2 during the drill retraction process, the centralizer wing 202 is removed first, and then the front and rear rods are mechanically removed by the drilling rig. After the reaming drill bit 1 is pulled out, the drill cuttings deposited on the lower side of the hole are discharged to the outside of the hole. The cylindrical profile structure of the reaming drill bit 1 will not damage the formation 9 on the lower side of the hole wall during the drill retraction process, and will maintain the regularity of the hole wall, which is conducive to the lowering of the casing.

Claims

1. A drilling tool assembly for enlarging large-diameter boreholes in coal mines, comprising enlarging drill bits (1), multiple drill rods (3), and a water feeder (4) connected in sequence, wherein a centralizer (2) is provided between some adjacent drill rods (3), characterized in that, The reaming drill bit (1) includes a sliding shaft (105), an auxiliary drill bit body (106) is movably sleeved in the middle of the sliding shaft (105), a limiting short section (107) is sleeved at the axial rear end of the sliding shaft (105), a reaming drill bit body (104) is sleeved at the axial front end of the sliding shaft (105), a fixing sleeve (103) is sleeved at the axial front end of the reaming drill bit body (104), the axial rear end of a ball joint hinge shaft (102) is provided inside the fixing sleeve (103), and a guide short section (101) is provided at the axial front end of the ball joint hinge shaft (102). The axial front end face of the fixed sleeve (103) is uniformly provided with a plurality of U-shaped grooves (1032), and the inner cavity of the fixed sleeve (103) is a spherical cavity (1033) and a conical cavity (1031) that are connected. The reaming drill bit body (104) includes a body, on which a plurality of winglets (1041) are uniformly arranged on the axial front end face. Each winglet (1041) has a PDC composite piece (1046) of different diameter welded on its front end face. A guide groove (1042) is formed between adjacent winglets (1041) along the axial direction. A ball socket (1044) is provided in the middle of the body. A plugging ball seat (1045) communicating with the ball socket (1044) is provided at the axial rear end of the body. A bottom flow channel (1043) is opened on the inner wall of the plugging ball seat (1045) and is uniformly distributed along the circumference. The bottom flow channel (1043) includes a radial hole and an axial hole that are connected and uniformly distributed along the circumference. The axial hole is connected to the outside of the reaming drill bit body (104). The sliding shaft (105) includes a first cylinder (1056). Multiple guide keys (1051) are evenly spaced along the circumference on the outer wall of the first cylinder (1056). The guide keys (1051) are provided with a first flow groove (1052) and a second flow groove (1054) of different depths and connected to each other. A radial flow channel (1053) is provided in the second flow groove (1054). The radial flow channel (1053) connects the inner cavity of the first cylinder (1056), the first flow groove (1052), and the second flow groove (1054). The auxiliary drill bit body (106) includes a second cylinder (1069), and auxiliary ribs (1061) are uniformly arranged on the axial front end of the outer wall of the second cylinder (1069). The auxiliary ribs (1061) correspond one-to-one with the guide grooves (1042) of the reaming drill bit body (104) in the circumferential direction. The auxiliary ribs (1061) are provided with carbide cutting teeth (1068) on the axial rear end. The circumferential width of the auxiliary prism (1061) is greater than the width of the guide groove (1042) on the reaming drill bit body (104), and the circumferential width of the auxiliary guide groove (1063) is less than the width of the prism (1041) on the reaming drill bit body (104). The inner wall of the second cylinder (1069) is provided with a plurality of guide keyways (1062) at equal intervals along the circumference, and the plurality of guide keyways (1062) are in one-to-one correspondence with a plurality of guide keys (1051) on the outer wall of the sliding shaft (105); a connecting groove (1067) is provided on the inner wall of the second cylinder (1069), and the connecting groove (1067) is connected to the guide keyways (1062); The inner wall of the second cylinder (1069) has a sliding cavity (1064) at its axial rear end, and a plurality of liquid flow holes (1065) are uniformly opened along the circumferential direction on the side wall of the sliding cavity (1064).

2. The coal mine underground large-diameter borehole reamer assembly as described in claim 1, characterized in that, The straightener (2) includes a front rod (201) and a rear rod (205) connected together; a plurality of straightening wings (202) are sleeved at the connection between the front rod (201) and the rear rod (205), and the plurality of straightening wings (202) form a cylinder.

3. The coal mine underground large-diameter borehole reamer assembly as described in claim 2, characterized in that, The front rod body (201) includes a mounting rod body (2011). The outer wall of the mounting rod body (2011) is provided with a plurality of dovetail grooves (2012) and a plurality of rectangular grooves (2013) arranged alternately along the circumference. The outer wall of the mounting rod body (2011) is provided with a third mounting groove (2015). The third mounting groove (2015) is perpendicular to and communicates with the dovetail grooves (2012) and the plurality of rectangular grooves (2013). The front rod body (201) is provided with a central flow channel (2014) inside. The rear rod body (205) includes a connecting and supporting section (2051) and a limiting frustum (2053) connected along the axial direction. The outer diameter of the connecting and supporting section (2051) is the same as that of the drill rod (3), and the outer diameter of the limiting frustum (2053) is the same as that of the mounting rod (2011) of the front rod body (201). A central channel (2052) is provided inside the rear rod body (205). Each of the straightening wings (202) has a straight rib plate (2024) at both ends of its inner wall in the circumferential direction. The straight rib plate (2024) is located in the rectangular groove (2013). A dovetail rib plate (2025) is provided in the middle of the inner wall of the straightening wing (202). The dovetail rib plate (2025) is located in the dovetail groove (2012). A limiting groove (2023) is provided on the dovetail rib plate (2025). A limiting block (204) is provided in the limiting groove (2023).

4. The coal mine underground large-diameter borehole reamer assembly as described in claim 3, characterized in that, The limiting groove (2023) is provided with a locking hole (2026); the limiting block (204) is provided with a limiting hole (2043), and a bolt (203) is provided in both the limiting hole (2043) and the locking hole (2026).

5. The coal mine underground large-diameter borehole reamer assembly as described in claim 3, characterized in that, The limiting block (204) includes a rectangular block (2041) and a fan-shaped block (2042). The rectangular block (2041) cooperates with the limiting groove (2023) on the straightening wing (202); the fan-shaped block (2042) cooperates with the third mounting groove (2015) on the front rod body (201).

6. The coal mine underground large-diameter borehole reamer assembly as described in claim 1, characterized in that, The outer wall of the first cylinder (1056) is stepped with an increasing diameter along the axial direction, and the outer wall of the axial rear end of the first cylinder (1056) is conical.

7. The coal mine underground large-diameter borehole reamer assembly as described in claim 1, characterized in that, The rear end face of the wing (1041) of the reaming drill bit body (104) is provided with a conical surface, and the front end face of the auxiliary wing (1061) of the auxiliary drill bit body (106) is provided with a conical surface at the same angle as the rear end face of the wing (1041).

8. The coal mine underground large-diameter borehole reamer assembly as described in claim 2, characterized in that, The straightening wing (202) has multiple windows (2022).

9. A method for forming holes in large-diameter boreholes in coal mines using a combination of drilling tools, characterized in that... The coal mine large-diameter borehole enlargement drill bit assembly based on any one of claims 1 to 8 specifically includes the following steps: Step 1: Use a small-diameter drill bit and drill rod to drill a pilot hole to the designed depth, then withdraw the drill rod and small-diameter drill bit in sequence; Step 2: Insert the guide section of the reaming drill bit (1) into the pilot hole obtained in Step 1, start the mud pump, and high-pressure water enters the water delivery device (4) through the pipeline. After the high-pressure water reaches the bottom of the hole, it cools the PDC composite sheet (1046) and carries the drill cuttings back out of the hole. Step 3: After enlarging the hole to a certain depth, observe the slag return at the hole opening and perform mechanical slag removal in the local section of the hole. The local hole section drilling and slag removal mechanism is a 'piston' body composed of an auxiliary drill bit body (106) and a hole-reaming drill bit body (104) to collect the drill cuttings deposited in the reamed section and push them out of the hole; Step 4: Drill again to continue enlarging the hole. Depending on the length of the enlarged section and the amount of slag returned during the enlargement process, repeat step 3 at certain intervals until the hole is enlarged to the predetermined depth to obtain a large-diameter borehole (7). Step 5: Pull back the coal mine large-diameter hole section reaming drill bit assembly by a short distance and rotate it slowly so that the auxiliary drill bit body (106) and the reaming drill bit body (104) fit together to form an assembly. Insert the plugging ball into the center hole of the drill rod (3) and flush it with water to the bottom hole reaming drill bit body (104). Step 6: Start retracting the drill bit. The reaming drill bit (1) collects the slag in the borehole at its rear end and discharges it mechanically. When the resistance to retracting the drill bit increases significantly during the process, turn on the mud pump to inject water into the hole, stir and flush away the slag accumulated at the rear end of the reaming drill bit (1), and continue retracting the drill bit until the reaming drill bit (1) is removed from the hole, thus completing the slag removal and hole formation. Step 7: Insert the casing into the obtained large-diameter borehole and seal it with grout as needed.

10. The method for forming a borehole using the large-diameter borehole enlargement drill bit assembly in coal mines as described in claim 9, characterized in that, Also includes: At regular intervals, a stabilizer is attached to the drill rod inside the hole and inserted into the hole to continue reaming and drilling.

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