A method of fishing a casing mill

Abstract

A reaming fishing method relates to the technical field of mine drilling tool fishing, and comprises the following steps: S1: fishing a fractured primary reaming drilling tool; S11: fixing the primary reaming drilling tool, lowering the fishing end to the outside of the primary reaming drilling rod through a reaming process in cooperation with a rigid fishing part, or setting a flexible fishing part, lowering the connecting end of the flexible fishing part into the primary reaming drilling rod and fixing it; S12: lifting the primary reaming drilling tool; S2: continuing to expand the primary fishing hole; S3: fishing a fractured drilling tool. The reaming fishing method is designed by stages and adapted to different scenes, first specifically completes fishing of the primary reaming drilling tool, and then continues to expand the hole and fishes the fractured drilling tool. On the one hand, the rigid or flexible fishing part accurately fixes the fractured primary reaming drilling tool, avoiding secondary damage to the hole wall during fishing.

Description

Technical Field

[0001] This invention relates to the field of drilling tool retrieval technology in mining areas, specifically a milling and retrieval method. Background Technology

[0002] In the directional drilling and pre-exploration of water drainage in the burned areas of the mining area, multiple directional main holes and branch holes need to be arranged to solve the safety hazards of water accumulation in the burned areas and to accurately explore the boundaries of the coal seam burned areas. The drilling operation relies on drill rods and drill bits. Due to the complex geological conditions in the burned areas, such as fractured rock strata and uneven stress, hole collapse and drill bit seizing are prone to occur during drilling, resulting in drill rod breakage. The broken drill rods and drill bits are left in the borehole and need to be retrieved through special salvage technology to restore the function of the borehole.

[0003] The core process of the current mainstream reaming technology is as follows: using a reaming drill bit and drill rod with a diameter larger than the broken drill rod (i.e., a first-stage reaming tool), the hole is reamed downwards to the location of the broken drill rod, forming a channel for the reaming tools to pass through; the drill rod carries a reaming cone into the hole, and by rotating the reaming cone, its internal thread taps the outer wall of the broken drill rod, forming a threaded connection; the drill rod is then driven upwards to pull the broken drill rod and drill bit out of the hole together. However, in actual engineering, the inventors and many engineers have reported that when the first-stage reaming tool breaks during the reaming process and remains inside the hole, there is a lack of effective reaming methods in this field due to geological conditions or large loads. It may be necessary to use hole-breaking excavation to remove the reaming tool and drilling bit, which requires a large investment of manpower and resources and cannot guarantee the normal use of the drilled channel. Summary of the Invention

[0004] To address the problem of retrieving broken drilling tools and retrieval tools from boreholes in mining areas without damaging the borehole, this invention provides a milling and retrieval method.

[0005] The technical solution of this invention is as follows: A milling and fishing method includes the following steps: S1: Retrieve the broken primary reaming drill bit; S11: Fixing of the primary reaming drill bit; The retrieval end is lowered to the outside of the first-stage reaming drill rod by using a reaming process in conjunction with a rigid retrieval component, or a flexible retrieval component is set up and the connecting end of the flexible retrieval component is lowered into the first-stage reaming drill rod and fixed. S12: Upgrade of the first-stage reaming drill bit. Lift the retrieval end or connecting end fixed to the first-stage reaming drill rod upwards until the first-stage reaming drill rod and the first-stage reaming drill bit are completely lifted out of the hole. S2: Continued expansion of the primary retrieval hole; A complete reaming drill rod and a first-stage reaming drill bit of the same size as the first-stage reaming drill bit in S1 are lowered into the hole and the hole is continued to be reamed downward from the break point until it falls to the first preset position and the first-stage reaming drill bit is withdrawn. S3: Retrieve the broken drilling tool; S31: Fixing the drilling tool The retrieval drill rod is connected to the retrieval mother cone and lowered into the hole until the bottom of the retrieval mother cone contacts the broken drilling rod. The retrieval drill rod is then rotated to drive the retrieval mother cone and the drilling rod to be threaded and fixed. S32: Improvement of drilling tools Lift the retrieval drill rod upwards, causing the retrieval mother cone to move upwards along the borehole until the retrieval drill rod and retrieval drill bit are completely lifted out of the borehole.

[0006] To prevent the drill rod from breaking further during retrieval, a suitable retrieval method is selected. Before proceeding to step S11, a geological survey is conducted inside the borehole. Based on a comparison of the rock layer hardness fluctuation range and the fluctuation threshold, the retrieval method is selected to use a hole-reaming process in conjunction with a rigid retrieval component or a flexible retrieval component for the retrieval of the first-stage hole-reaming drill bit.

[0007] To minimize the risk of fracture due to improper operation when rock hardness fluctuations are small, it is advisable to continue using larger-sized retrieval drill rods and bits for retrieval, saving time on equipment replacement. When the rock hardness fluctuation range does not exceed the fluctuation threshold, a hole-reaming process combined with rigid retrieval components is used for retrieval, including the following steps: S111: Use a secondary reaming drill rod and a secondary reaming drill bit with a size larger than the primary reaming drill bit to ream the hole vertically downward along the channel until it is expanded to the second preset position; S112: Lower the rigid retrieval component along the hole to the upper end of the first-stage reaming drill rod, align and fix it, and lift the rigid retrieval component upward to drive the first-stage retrieval drill rod and the first-stage retrieval drill bit to be lifted out of the hole.

[0008] The rigid retrieval component is specifically designed as follows: the rigid retrieval component includes a secondary drill rod, the bottom of which is equipped with a secondary female cone. The secondary female cone can fall down with the secondary drill rod onto the primary retrieval drill rod and be fixed thereto by milling threads through a rotating sleeve.

[0009] To address the issue of high breakage rates when using retrieval drill rods and bits in situations with large fluctuations in rock hardness, and to reduce the number of retrieval attempts and improve retrieval efficiency, when the rock hardness fluctuation exceeds a threshold, a flexible retrieval component is installed on the ground around the borehole to retrieve the primary reaming drill bit. This flexible retrieval component includes a retrieval rope, with the connecting end fixed to the end of the retrieval rope. The process includes the following steps: S111: Lower the connecting end along the ditch along the salvage rope until the connecting end moves into the broken first-stage reaming drill rod and is fixed. S112: Install a hydraulic cylinder on the ground around the borehole, with its output end pointing vertically upward. Fix a rope to its output end and secure it to the retrieval rope. Start the hydraulic cylinder to pull the retrieval rope upward until the first-stage reaming drill rod and the first-stage reaming drill bit are completely lifted out of the borehole.

[0010] The connection end is specifically designed as follows: the connection end includes a main body block that is fixed to the salvage rope; multiple first limiting blocks are arranged circumferentially at intervals on the outer side of the main body block; and multiple second limiting blocks are arranged circumferentially at intervals on the inner wall of the first-stage reaming drill rod. The minimum distance between adjacent second limiting blocks along the circumferential direction of the wall is not less than the width of the first limiting block. In step S111, during the falling process of the connecting end, the main body block passes between multiple second limiting blocks, the first limiting block passes between adjacent second limiting blocks, rotates and lifts the salvage rope upward, and fixes the first limiting block and the second limiting block in contact.

[0011] To improve the limiting effect of the second limiting block on the first limiting block, two second limiting blocks are arranged opposite each other along the inner wall of the first-stage reaming drill rod, and two first limiting blocks are set accordingly. The circumferential length of the second limiting block is at least twice the length of the first limiting block.

[0012] According to claim 6, the milling and fishing method is characterized in that the second limiting block is disposed near the bottom end of the first-stage reaming drill rod, and the distance between the end of the second limiting block and the bottom end of the first-stage reaming drill rod is greater than the axial length of the first limiting block.

[0013] In order to improve the strength of the first limiting block and the second limiting block and the stability of their limiting, and to improve the strength of the connection end fixed to the first-stage reaming drill rod, the length of the second limiting block along the axial direction of the first-stage reaming drill rod is greater than the length of the first limiting block along the same direction, and the length of the first limiting block is not less than the inner diameter of the first-stage reaming drill rod. The bottom of the second limiting block is provided with a receiving groove, and after the first limiting block is lifted, it can enter the receiving groove.

[0014] To accommodate the stroke of the hydraulic cylinder, the first-stage reaming drill rod is lifted step by step. The retrieval rope has multiple connectors spaced apart along its length, and each connector can be fixed to the connecting rope. In step S112, when the stroke of the hydraulic cylinder reaches its maximum, the connection to the current connector is released, and the output end is retracted. The connecting rope is then fixed to the connector below in sequence, and the rope is lifted step by step.

[0015] The beneficial effects of this invention are as follows: This invention is a milling and retrieval method, which effectively solves the industry pain point of difficulty in retrieving the first-stage reaming drill bit after it breaks during the directional advanced exploration construction of water drainage in the burned area of ​​the mine. It completely abandons the traditional extensive treatment method of hole breaking and excavation, and significantly improves the effectiveness of drill bit retrieval and the utilization rate of the duct. Compared to existing technologies that lack specific solutions for dealing with the breakage of primary reaming drill bits, require significant manpower and resources for excavation, and cannot guarantee the reuse of drilled channels, this milling and retrieval method, through its core design of phased retrieval and scenario-specific adaptation, first retrieves the primary reaming drill bit, then continues to expand the channel and retrieves the broken drill bit. On the one hand, the broken primary reaming drill bit is precisely fixed by rigid or flexible retrieval components, avoiding secondary damage to the channel wall during the retrieval process; on the other hand, after retrieval, a reaming drill bit of the same size is used to continue expanding the hole from the breakage location, eliminating the need for re-drilling, maximizing the integrity of the already constructed channel, ensuring the continuity of subsequent drainage and exploration operations, and significantly reducing the risk of project delays caused by drill bit breakage. Regarding adaptability to complex geological scenarios, this method dynamically selects the retrieval method to accurately respond to different rock strata conditions, significantly improving the retrieval success rate. Through pre-construction geological testing, the range and threshold of rock hardness fluctuations are compared. When the rock hardness is stable, a secondary reaming drill bit is used in conjunction with a rigid retrieval component. First, the hole is enlarged to create a safe working space. Then, milling and tapping are used to achieve a rigid connection with the primary reaming drill bit, ensuring stable stress during retrieval and adapting to scenarios where the rock strata are intact and not prone to collapse. When the rock hardness fluctuates greatly, rigid retrieval can easily lead to breakage. A flexible retrieval component is used, with the first limiting block and the second limiting block on the inner wall of the primary reaming drill rod acting as a contact point. Fixation can be completed without additional hole enlargement, avoiding disturbance to the fractured rock strata caused by rigid operation, reducing the risk of hole collapse, and effectively preventing the risk of breakage when using larger retrieval drill rods. This allows the retrieval operation to adapt to the complex geological environment of fractured and unevenly stressed rock strata in fire-affected areas. This method also offers ease of operation and cost-effectiveness, significantly reducing construction costs and workload in mining areas. Rigid retrieval components are quickly connected via milling and tapping, while flexible retrieval components are fixed using limiting blocks. Neither method requires complex equipment or cumbersome procedures; the operation process is simple and easy to understand, allowing on-site workers to quickly master it. Attached Figure Description

[0016] The solutions and advantages of this application will become clear to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] In the attached diagram: Figure 1 A schematic diagram of drill rod fracture inside the borehole; Figure 2 This is a schematic diagram of a two-stage borehole expansion. Figure 3 Diagram showing the connection for the secondary mother cone salvage operation; Figure 4 A schematic diagram of retrieving a drill rod; Figure 5 Schematic diagram for raising the retrieval drill rod; Figure 6 This is a schematic diagram of retrieving the first-stage reaming drill rod in Example 2; Figure 7 This is a schematic diagram of the first-stage borehole enlargement. Figure 8 A schematic diagram showing the first limiting block passing through the second limiting block; Figure 9 This is a top view of the drill rod in Example 2; The components represented by the various reference numerals in the diagram are: 1. Primary reaming drill rod; 2. Hole channel; 3. Primary reaming drill bit; 4. Complete reaming drill rod; 5. Retrieval drill rod; 6. Retrieval mother cone; 7. Drilling drill rod; 8. Drilling drill bit; 9. Secondary reaming drill rod; 10. Secondary reaming drill bit; 11. Secondary drill rod; 12. Secondary mother cone; 13. Retrieval rope; 14. Hydraulic cylinder; 15. Connecting rope; 16. Main block; 17. First limiting block; 18. Second limiting block; 19. Receiving groove; 20. Connecting parts. Detailed Implementation

[0018] Exemplary embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. It should be noted that these embodiments are provided to enable a more thorough understanding of this disclosure and to fully convey the scope of this disclosure to those skilled in the art. This disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0019] like Figure 1-9 The milling and retrieval method shown is mainly aimed at the retrieval work after the drilling drill bit 8, drilling drill rod 7, and the primary retrieval drill tool used for retrieval break in the borehole 2 due to geological or operational factors during drilling in a mining area. One of the core technical points of this invention is that it combines... Figure 1 After the primary retrieval drill bit broke again inside borehole 2, the geological conditions inside borehole 2 were first tested, and a suitable retrieval method and equipment were selected based on the test results.

[0020] Example 1 In actual drilling and retrieval operations, the breakage of the drilling bit 8, drilling rod 7, and the primary retrieval drilling tools used for both drilling and retrieval is usually affected by many factors, the most important being the geological conditions and human error. In terms of geological conditions, the characteristics of rock strata vary significantly in different mining areas. In some mining areas, the rock strata are extremely hard, and when the drilling bit 8 or drill rod comes into contact with them, the huge reaction force may cause the drill bit or drill rod to break instantly. In other mining areas, the rock strata are more broken and loose, and during the drilling process, the unstable structure of the rock strata can easily cause the hole to collapse, which in turn causes the drill rod to get stuck or break.

[0021] Firstly, this embodiment discloses a milling and salvage method, combined with... Figures 2-5 When the retrieval drill bit breaks in borehole 2, the milling and retrieval method of this invention is followed. First, a geological survey is conducted. If the survey results show that the rock hardness fluctuation range does not exceed the fluctuation threshold, meaning the rock hardness is relatively stable, it may be due to an operational error by the construction personnel. In this case, a borehole enlargement process combined with a rigid retrieval component is used for retrieval. This eliminates the need to replace the retrieval equipment; only the rigid retrieval component needs to be replaced. The specific steps include: S1: Retrieve the broken first-stage reaming drill bit. S11: The retrieval of the primary reaming drill bit is carried out using a hole-reaming process in conjunction with a rigid retrieval component. S111: Combination Figure 2 Using a secondary reaming drill rod 9, which is larger than the primary reaming drill bit, and a secondary reaming drill bit 10, the hole is slowly and vertically expanded downward along the channel 2 until it reaches the second preset position. This is to perform secondary reaming operation on the channel 2 in order to retrieve the primary reaming drill bit. During the reaming process, the drilling pressure and rotation speed are controlled to avoid the secondary reaming drill bit from breaking due to excessive load. It should also be noted that the reaming drill bits are all hollow to ensure that the reaming drill rod can be accommodated during the reaming process. The second preset position is determined by prior surveying, and the expansion extends to expose the upper part of the primary reaming drill rod 1, which facilitates the subsequent cooperation with the secondary mother cone 12.

[0022] S112: Combination Figure 3The rigid retrieval component is lowered along the borehole 2 to the upper end of the first-stage reaming drill rod 1, aligned and fixed. The rigid retrieval component is then lifted upwards, causing the first-stage retrieval drill rod 5 and the first-stage retrieval drill bit to be fully lifted out of the borehole 2. The rigid retrieval component includes a second-stage drill rod 11, with a second-stage female cone 12 installed at its bottom. The internal thread specification of the second-stage female cone 12 is compatible with the outer wall of the first-stage reaming drill rod 1. After connecting the second-stage drill rod 11 and the second-stage female cone 12, it is slowly lowered into the reaming section of the borehole 2 until the bottom of the second-stage female cone 12 contacts the upper end face of the first-stage reaming drill rod 1. The drill rotation system is activated, causing the second-stage drill rod 11 and the second-stage female cone 12 to rotate synchronously. The second-stage female cone 12, through rotation, mills matching external threads on the outer wall of the first-stage reaming drill rod 1, forming a threaded connection and completing the fixation of the rigid retrieval component to the first-stage reaming drill rod 1.

[0023] S12: Upgrade of the first-stage reaming drill bit. The drill string rotation system is shut down, the lifting equipment is started, and the top of the secondary drill string 11 is connected to the lifting wire rope. The secondary drill string 11 is slowly lifted upwards. During the lifting process, the lifting load is monitored in real time to avoid secondary breakage of the drill string due to sudden load changes. The process continues until the primary reaming drill string 1 and the primary reaming drill bit 3 are completely lifted out of the borehole 2, completing the retrieval of the broken primary reaming drill string.

[0024] S2: Continued expansion of the primary retrieval hole; Select a complete reaming drill rod 4 and a first-stage reaming drill bit 3 of the same size as the first-stage reaming drill bit in S1, and combine them. Figure 7 For ease of illustration, Figure 4 , 5 The hole drilled by the secondary reamer 10, which is not shown in section 7, is slowly lowered into hole 2 after being assembled via the drill string connection device. Once the primary reamer 3 reaches the fracture location within hole 2, i.e., the fracture point of the original primary reamer, the drilling system is activated, and the reaming parameters are controlled to continue reaming downwards from the fracture location. This continues until the hole reaches the first preset position, where, after surveying, the upper end of the fractured drilling rod 7 must be exposed to facilitate coordination with the subsequent retrieval cone 6. The drilling system is then shut down, and the primary reamer is slowly withdrawn.

[0025] S3: Retrieve the broken drilling tool; S31: Fixing the drilling tool Select a retrieval cone 6 that is compatible with the 7-specification drilling rod, and combine it with... Figure 4The drill string 7 is fixed to the bottom of the retrieval drill rod 5 via a threaded connection. The assembled retrieval drill rod 5 and retrieval cone 6 are slowly lowered into the borehole 2. During the descent, the depth is monitored in real time using a depth counter until the bottom of the retrieval cone 6 contacts the top of the broken drilling drill rod 7. The drill rotation system is then activated, causing the retrieval drill rod 5 and retrieval cone 6 to rotate synchronously. The retrieval cone 6, through rotation, mills matching threads onto the outer wall of the broken drilling drill rod 7, forming a stable threaded connection and completing the fixing of the drilling tool.

[0026] S32: Improvement of drilling tools Shut down the drill string rotation system, start the hoisting equipment, and combine... Figure 5 The top of the retrieval drill rod 5 is connected to the lifting device, and the retrieval drill rod 5 is slowly lifted upwards. During the lifting process, a uniform speed is maintained to avoid loosening of the threaded connection due to excessive lifting speed, until the retrieval drill rod 5 drives the retrieval mother cone 6, the broken drilling drill rod 7, and the drilling drill bit 8 to be lifted out of the hole 2, completing the entire milling and retrieval operation.

[0027] The above are salvage methods used in areas with good geological conditions. Using the above methods, the salvage drill rod 5 and drill bit can be directly replaced on the original equipment, which can save the time of replacing salvage equipment. However, after the geological test of the borehole 2, the geological test results show that the rock hardness fluctuation range exceeds the fluctuation threshold, that is, the rock hardness fluctuates greatly. Using rigid salvage parts is prone to breakage. The salvage is carried out using the method in the following embodiments.

[0028] Example 2 This embodiment discloses a milling and retrieval method for borehole 2 with poor geological conditions, specifically including the following steps: S1: Retrieve the broken first-stage reaming drill bit. S11: Fixing the first-stage reaming drill string. Before performing this step, geological testing is conducted within borehole 2. Data such as rock hardness and porosity are collected using a multi-parameter logging tool, and the rock hardness fluctuation range is calculated. After confirming that this range exceeds the preset fluctuation threshold, a flexible retrieval device is used to retrieve the first-stage reaming drill string.

[0029] Firstly, in this embodiment, combined with Figure 6 , 89. The flexible retrieval component includes a retrieval rope 13, made of high-strength steel wire rope, with a fixed connecting end. The connecting end includes a main body block 16 fixed to the end of the retrieval rope 13. Two first limiting blocks 17 are arranged circumferentially at intervals on the outer side of the main body block 16. Simultaneously, two second limiting blocks 18 are arranged circumferentially at intervals on the inner wall of the first-stage reaming drill rod 1. The second limiting blocks 18 are positioned close to the bottom end of the first-stage reaming drill rod 1, which increases the strength of the bottom end of the first-stage reaming drill rod 1. Through several experimental analyses by the inventors, even if the first-stage reaming drill rod 1 breaks, the breakage location is usually above the second limiting blocks 18. This ensures that the second limiting blocks 18 remain intact within the borehole 2 along with the first-stage reaming drill rod 1. The distance from the end of the second limiting block 18 to the bottom end of the first-stage reaming drill rod 1 is greater than the axial length of the first limiting blocks 17. Figure 9 Furthermore, the bottom of the second limiting block 18 is provided with a receiving groove 19 that is adapted to the first limiting block 17, and the receiving groove 19 extends upward.

[0030] S111: Combination Figure 6 The connecting end is lowered along the retrieval rope 13 along the borehole 2 until it moves into and is fixed inside the broken first-stage reaming drill rod 1. After connecting the connecting end to the retrieval rope 13, the retrieval rope 13 is slowly lowered using the borehole guide device, causing the connecting end to fall along the borehole 2. Figure 8 As shown, when the main block 16 falls to the first limiting block 17, the retrieval rope 13 can be rotated to ensure that the first limiting block 17 passes smoothly through the gap between the adjacent second limiting blocks 18. After the main body block 16 reaches below the first limiting block 17 inside the first-stage reaming drill rod 1, the retrieval rope 13 drives the main body block 16 to rotate 90°, and the retrieval rope 13 is slowly lifted upward, so that the first limiting block 17 enters the receiving groove 19 at the bottom of the second limiting block 18, thereby fixing the connecting end to the first-stage reaming drill rod 1.

[0031] Furthermore, it should be noted that the circumferential length of the second limiting block 18 is at least twice the length of the first limiting block 17, which can increase the limiting area of ​​the second limiting block 18 on the first limiting block 17, effectively preventing the two from separating and improving the fixing strength between the connecting end and the first-stage reaming drill rod 1. The guide length of the first limiting block 17 is not less than the inner diameter of the first-stage reaming drill rod 1, so that both the first limiting block 17 and the second limiting block 18 have greater structural strength, so that they will not break or fall off due to uneven force during the lifting process.

[0032] S112: Hydraulic cylinders 14 are installed on the ground around the borehole 2, with their output ends pointing vertically upwards. Multiple hydraulic cylinders 14 can be arranged along the borehole 2, with each output end fixedly connected to a rope 15, which is then fixed to the retrieval rope 13. The hydraulic cylinder 14 is activated to pull the retrieval rope 13 upwards until the first-stage reaming drill rod 1 and the first-stage reaming drill bit 3 are completely lifted out of the borehole 2. It should be noted that multiple connectors 20 are arranged at intervals along the length of the retrieval rope 13. Each connector 20 can be a locking ring. When the stroke of the hydraulic cylinder 14 reaches its maximum, the hydraulic cylinder 14 is paused, the connection rope 15 is released from the current connector 20, the output end of the hydraulic cylinder 14 is retracted, the connection rope 15 is re-fixed to the adjacent connector 20 below, and the hydraulic cylinder 14 is activated again to continue lifting. It should be noted that the hydraulic cylinder 14 can be disconnected one by one from the current connector 20 and then from the next connector 20. The remaining hydraulic cylinder 14 can maintain the retrieval rope 13. Repeat the above operation until the first-stage reaming drill rod 1 and the first-stage reaming drill bit 3 are all lifted out of the hole 2, thus completing the retrieval of the broken first-stage reaming drill tool.

[0033] S2: Continued expansion of the primary retrieval hole; Select a complete reaming drill rod 4 and a first-stage reaming drill bit 3 of the same size as the first-stage reaming drill bit in S1, and combine them. Figure 7 After being assembled via the drill string connection device, the drill string is slowly lowered into borehole 2. Once the first-stage reaming bit 3 reaches the fracture location within borehole 2, i.e., the fracture point of the original first-stage reaming bit, the drilling system is activated, and the reaming parameters are controlled to continue reaming downwards from the fracture location. It should be noted that, due to the poor geological conditions of borehole 2, but without needing to start drilling from scratch, a stronger first-stage reaming bit 3 can be used to adapt to the geological strength requirements of the fracture location. During drilling, the rotation speed and descent speed are reasonably controlled until the borehole is reamed to the first preset position. This position, after surveying, also needs to ensure that the upper end of the fractured drilling rod 7 is exposed to facilitate coordination with the subsequent retrieval mother cone 6. The drilling system is then shut down, and the first-stage reaming bit is slowly withdrawn.

[0034] S3: Retrieve the broken drilling tool; S31: Fixing the drilling tool Select a retrieval cone 6 that is compatible with the 7-specification drilling rod, and combine it with... Figure 4The drill string 7 is fixed to the bottom of the retrieval drill rod 5 via a threaded connection. The assembled retrieval drill rod 5 and retrieval cone 6 are slowly lowered into the borehole 2. During the descent, the depth is monitored in real time using a depth counter until the bottom of the retrieval cone 6 contacts the top of the broken drilling drill rod 7. The drill rotation system is then activated, causing the retrieval drill rod 5 and retrieval cone 6 to rotate synchronously. The retrieval cone 6, through rotation, mills matching threads onto the outer wall of the broken drilling drill rod 7, forming a stable threaded connection and completing the fixing of the drilling tool.

[0035] S32: Improvement of drilling tools Shut down the drill string rotation system, start the lifting equipment, and slowly lift the top of the fishing drill rod 5 upwards via the lifting device. Figure 5 During the lifting process, maintain a constant speed to avoid loosening of the threaded connection due to excessive lifting speed, until the retrieval drill rod 5 drives the retrieval mother cone 6, the broken drilling drill rod 7 and the drilling drill bit 8 to be lifted out of the channel 2, completing the entire set of milling and retrieval operations.

[0036] Both of the above-mentioned milling and retrieval embodiments are designed to address the retrieval challenges of broken primary reaming drill bits during directional advanced exploration for drainage in burned areas of mines. The core of both embodiments involves a three-step process: retrieving the primary reaming drill bit, expanding the primary retrieval hole, and retrieving the drilling drill bit. This process ensures the complete removal of the broken drill bit from the borehole 2, avoiding resource waste and damage to the borehole 2 caused by excavation. Embodiment 1 is suitable for scenarios with minimal fluctuations in rock hardness. It utilizes a secondary reaming stage combined with a rigid retrieval component featuring a secondary mother cone 12, achieving stable retrieval through a threaded connection. This method offers high precision, is suitable for boreholes with stable geological conditions, and saves time on replacing retrieval equipment. Embodiment 2 is suitable for complex scenarios with significant fluctuations in rock hardness. It combines a connecting end with a limiting block with a multi-stage lifting hydraulic cylinder 14 and a retrieval rope 13, using mechanical limiting and flexible lifting to mitigate the risk of impact from hard rock, making it suitable for boreholes with complex geological conditions.

Claims

1. A milling and salvage method, characterized in that, Includes the following steps: Geological testing was conducted before construction to compare the fluctuation range of rock layer hardness with the threshold. S1: Retrieve the broken primary reaming drill bit; S11: Fixing the first-stage reaming drill bit. When the rock hardness is stable, first reaming the hole to form a safe working space, and then using milling and tapping to achieve a rigid connection with the first-stage reaming drill bit. By using a hole-reaming process in conjunction with a rigid retrieval component, the retrieval end is lowered and fixed to the outside of the first-stage hole-reaming drill rod. When the rock hardness fluctuates greatly, a flexible retrieval component is used. The connecting end of the flexible retrieval component is lowered into the first-stage hole-reaming drill rod and fixed by the first limiting block against the second limiting block on the inner wall of the first-stage hole-reaming drill rod. S12: Upgrade of the first-stage reaming drill bit. Lift the retrieval end or connecting end fixed to the first-stage reaming drill rod upwards until the first-stage reaming drill rod and the first-stage reaming drill bit are completely lifted out of the hole. S2: Continued expansion of the primary retrieval hole; A complete reaming drill rod and a first-stage reaming drill bit of the same size as the first-stage reaming drill bit in S1 are lowered into the hole and the hole is continued to be reamed downward from the break point until it falls to the first preset position and the first-stage reaming drill bit is withdrawn. S3: Retrieve the broken drilling tool; S31: Fixing the drilling tool The retrieval drill rod is connected to the retrieval mother cone and lowered into the hole until the bottom of the retrieval mother cone contacts the broken drilling rod. The retrieval drill rod is then rotated to drive the retrieval mother cone and the drilling rod to be threaded and fixed. S32: Improvement of drilling tools Lift the retrieval drill rod upwards, causing the retrieval mother cone to move upwards along the borehole until the retrieval drill rod and retrieval drill bit are completely lifted out of the borehole.

2. The milling and fishing method according to claim 1, characterized in that, When the hardness fluctuation range of the rock strata does not exceed the fluctuation threshold, a hole-enlarging process combined with a rigid retrieval device is used for retrieval, which includes the following steps: S111: Use a secondary reaming drill rod and a secondary reaming drill bit with a size larger than the primary reaming drill bit to ream the hole vertically downward along the channel until it is expanded to the second preset position; S112: Lower the rigid retrieval component along the hole to the upper end of the first-stage reaming drill rod, align and fix it, and lift the rigid retrieval component upward to drive the first-stage retrieval drill rod and the first-stage retrieval drill bit to be lifted out of the hole.

3. The milling and salvage method according to claim 2, characterized in that, The retrieval end of the rigid retrieval component includes a secondary drill rod, the bottom of which is equipped with a secondary female cone. The secondary female cone can fall down with the secondary drill rod onto the primary retrieval drill rod and be fixed to it by milling threads through a rotating sleeve.

4. The milling and fishing method according to claim 1, characterized in that, When the rock hardness fluctuation range exceeds the fluctuation threshold, the primary reaming drill bit is retrieved by setting a flexible retrieval component on the ground around the borehole. The flexible retrieval component includes a retrieval rope, with the connecting end fixed to the end of the retrieval rope. The process includes the following steps: S111: Lower the connecting end along the ditch along the salvage rope until the connecting end is moved into the broken first-stage reaming drill rod and fixed. S112: Install a hydraulic cylinder on the ground around the borehole, with its output end pointing vertically upward. Fix a rope to its output end and secure it to the retrieval rope. Start the hydraulic cylinder to pull the retrieval rope upward until the first-stage reaming drill rod and the first-stage reaming drill bit are completely lifted out of the borehole.

5. The milling and fishing method according to claim 4, characterized in that, The connecting end includes a main body block fixed to the salvage rope. Multiple first limiting blocks are arranged circumferentially at intervals on the outer side of the main body block, and multiple second limiting blocks are arranged circumferentially at intervals on the inner wall of the first-stage reaming drill rod. The minimum distance between adjacent second limiting blocks along the circumferential direction of the wall is not less than the width of the first limiting block. In step S111, during the falling process of the connecting end, the main body block passes between multiple second limiting blocks, the first limiting block passes between adjacent second limiting blocks, rotates and lifts the salvage rope upward, and fixes the first limiting block and the second limiting block in contact.

6. The milling and fishing method according to claim 5, characterized in that, Two second limiting blocks are arranged opposite each other along the inner wall of the first-stage reaming drill rod, and two first limiting blocks are set accordingly. The length of the second limiting block along the circumferential direction is at least twice the length of the first limiting block.

7. The milling and fishing method according to claim 5, characterized in that, The second limiting block is positioned close to the bottom end of the first-stage reaming drill rod, and the distance between the end of the second limiting block and the bottom end of the first-stage reaming drill rod is greater than the axial length of the first limiting block.

8. The milling and fishing method according to claim 7, characterized in that, The length of the second limiting block along the axial direction of the first-stage reaming drill rod is greater than the length of the first limiting block along the same direction, and the guide length of the first limiting block is not less than the inner diameter of the first-stage reaming drill rod. The bottom of the second limiting block is provided with a receiving groove, and after the first limiting block is lifted, it can enter the receiving groove.

9. The milling and fishing method according to claim 4, characterized in that, The salvage rope is provided with multiple connectors spaced apart along its length, and each connector can be fixed to the connecting rope. In step S112, when the hydraulic cylinder reaches its maximum stroke, the connection to the current connector is released and the output end is retracted. The connecting rope is then fixed to the connectors below in sequence, and the rope is lifted step by step.

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