Downhole falling block treatment tool and treatment method

Abstract

The invention provides an underground chipping processing tool and method. The tool comprises a drill rod and a power drilling tool arranged at the lower end of the drill rod. A hollow shaft is arranged at the lower end of the power drilling tool, and an inner milling head is arranged at the lower end of the hollow shaft; the internal milling head is arranged on the lower portion of the power drilling tool, the casing milling barrel is arranged below the power drilling tool in a sleeving mode, the casing milling barrel is arranged outside the internal milling head in a sleeving mode, and a casing milling drill bit is arranged at the lower end of the casing milling barrel.

Description

Technical Field

[0001] This invention relates to a tool and method for handling downhole rockfalls, belonging to the technical field of downhole processing devices and methods. Background Technology

[0002] During oil well drilling, wellbore collapse often occurs in the open hole section, generating a large number of boulders that partially fill the drilled wellbore. Some of these boulders are hard and strong, and cannot be broken by conventional drill bits. They cannot be removed from the wellbore by using heavy plugs or thick plugs. Moreover, large boulders can cause stuck pipe accidents, which seriously affect drilling speed and downhole safety.

[0003] The current solution is to use downhole tools to retrieve the fallen blocks from the wellbore. However, this method has obvious drawbacks. When the amount of fallen blocks is large, the amount that can be retrieved in a single operation is limited, requiring multiple trips to retrieve the blocks. In existing applications, this has already involved more than ten trips. In addition, retrieval in deep wells consumes a lot of time during trips, resulting in extremely low retrieval efficiency. Furthermore, prolonged immersion of the open hole section in drilling fluid increases downhole safety risks. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention proposes a tool and method for handling downhole rock spalling, which can be used not only for handling general rock spalling situations, but also for deep wells and situations involving large amounts of rock spalling with high hardness and strength.

[0005] According to one aspect of the present invention, a downhole block handling tool is provided, comprising: Drill pipe, A power drilling tool is installed at the lower end of the drill rod; a hollow shaft is installed at the lower end of the power drilling tool, and an internal milling head is installed at the lower end of the hollow shaft; and A milling sleeve is disposed below the power drill bit, the milling sleeve is fitted over the internal milling head, and a milling drill bit is disposed at the lower end of the milling sleeve.

[0006] A further improvement of the present invention is that the hollow shaft is configured to move along the axial direction of the milling sleeve, and a clutch is provided between the hollow shaft and the milling sleeve. The hollow shaft moves axially, thereby connecting or separating the hollow shaft from the milling sleeve via the clutch.

[0007] A further improvement of the present invention is that a thrust bearing is provided at the lower part of the hollow shaft, and the thrust bearing is arranged inside the milling sleeve; a spring seat is provided on the milling sleeve, the spring seat and the thrust bearing form a spring cavity, a spring is provided in the spring cavity, one end of the spring is connected to the thrust bearing, and the other end is connected to the spring seat.

[0008] A further improvement of the present invention is that the clutch includes a first clutch tooth disposed on the hollow shaft and a second clutch tooth disposed on the milling sleeve, the first clutch tooth and the second clutch tooth being capable of meshing.

[0009] A further improvement of the present invention is that the second clutch tooth is disposed at the lower end of the spring seat.

[0010] A further improvement of the present invention is that a retrieval cup is provided above the milling sleeve, the retrieval cup is connected to the hollow shaft, and the opening of the retrieval cup faces upward.

[0011] A further improvement of the present invention is that a ring of supporting ribs is provided on the upper part of the retrieval cup, so that the falling block can fall into the retrieval cup through the gaps between the supporting ribs.

[0012] A further improvement of the present invention is that a leakage hole is provided on the side wall of the retrieval cup.

[0013] A further improvement of the present invention is that the side wall of the milling sleeve is provided with a breathing hole and a chip removal hole.

[0014] According to another aspect of the present invention, a method for segmented compaction and milling of downhole rock is also proposed, wherein the downhole rock processing tool is used to perform segmented compaction and milling of the downhole rock, the method comprising: The dropped block is inserted into the milling sleeve and compacted. The dropped block is then milled into drill cuttings by the milling drill bit and the internal milling head, and returned to the surface with the drilling fluid. Raise the drill string again, start the pump, lower the drill string, put the remaining debris into the sleeve, compact it, and grind the debris into drill cuttings through the sleeve milling bit and the internal milling bit, and return it to the surface with the drilling fluid circulation; Repeat the above process until the downhole blocks are milled in sections.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The tool and method for handling downhole rock spalling according to the present invention can be used not only for handling general rock spalling situations, but also for deep wells and situations involving large amounts of rock spalling with high hardness and strength.

[0016] The downhole block removal tool according to the present invention does not require multiple trips to the drilling site; all downhole blocks can be removed in a single trip. The downhole tool can provide feedback on whether the downhole blocks have been removed, avoiding ineffective drilling and retrieval. During the removal of blocks, the drilling fluid is in a circulating state, effectively ensuring downhole safety. The downhole block handling tool described in this invention has an outer diameter that is much smaller than the wellbore diameter, which enhances the safety of tripping in and out of the well. Attached Figure Description

[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 The diagram shown is a structural schematic of a downhole block handling tool according to an embodiment of the present invention, illustrating the clutch engagement state; Figure 2 The diagram shown is a structural schematic of a downhole block handling tool according to an embodiment of the present invention, illustrating the clutch disengagement state; The accompanying drawings are not drawn to scale.

[0018] The meanings of the reference numerals in the attached figures are as follows: 1. Drill rod, 2. Power drill, 3. Fishing cup, 31. Leakage hole, 4. Hollow shaft, 5. Thrust bearing, 51. Bearing housing, 6. Spring, 7. Milling sleeve, 71. Spring chamber, 72. Breathing hole, 73. Spring seat, 74. Chip removal hole, 8. Clutch, 81. Second clutch tooth, 82. First clutch tooth, 9. Internal milling head, 10. Milling sleeve drill bit. Detailed Implementation

[0019] To make the technical solutions and advantages of the present invention clearer, exemplary embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. Furthermore, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0020] During oil well drilling, wellbore collapse often occurs in the open hole section, generating a large number of boulders that partially fill the drilled wellbore. Some of these boulders are hard and strong, and cannot be broken by conventional drill bits. They cannot be removed from the wellbore by using heavy plugs or thick plugs. Moreover, large boulders can cause stuck pipe accidents, which seriously affect drilling speed and downhole safety.

[0021] The current solution is to use downhole tools to retrieve the fallen blocks from the wellbore. However, this method has obvious drawbacks. When the amount of fallen blocks is large, the amount that can be retrieved in a single operation is limited, requiring multiple trips to retrieve the blocks. In existing applications, this has already involved more than ten trips. In addition, retrieval in deep wells consumes a lot of time during trips, resulting in extremely low retrieval efficiency. Furthermore, prolonged immersion of the open hole section in drilling fluid increases downhole safety risks.

[0022] To address the aforementioned problems, this invention proposes a tool and method for handling downhole rock spalling, which can be used not only for general rock spalling but also for deep wells and situations involving large quantities of rock spalling with high hardness and strength.

[0023] In such Figure 1In the illustrated embodiment, a downhole block handling tool includes: Drill pipe 1, The lower end of the drill rod 1 is provided with a power drill tool 2, which is preferably a turbine or a screw. The upper end of the power drill tool 2 is provided with a threaded interface connected to the drill rod 1, and the lower part of the power drill tool 2 is connected with a hollow shaft 4.

[0024] The lower end of the hollow shaft 4 is provided with an internal grinding head 9.

[0025] A milling sleeve 7 is disposed below the power drill 2. The milling sleeve 7 is sleeved outside the internal milling head 9, and a milling drill bit 10 is disposed at the lower end of the milling sleeve 7. When the milling sleeve 7 enters the block pile, the blocks enter the milling sleeve 7 and the drill string continues to be lowered. When the milling sleeve 7 can no longer hold the blocks, the blocks are compacted and the drilling pressure increases significantly. At this time, the drilling fluid discharge is increased, the power drill tool 2 rotates faster, and drives the internal milling head 9 and the milling sleeve drill bit 10 to mill the blocks.

[0026] In one embodiment, the hollow shaft 4 is configured to move along the axial direction of the milling sleeve 7, and a clutch 8 is provided between the hollow shaft 4 and the milling sleeve 7. The hollow shaft 4 moves axially, thereby connecting or separating the hollow shaft 4 from the milling sleeve 7 via the clutch 8.

[0027] When the hollow shaft 4 is connected to the milling sleeve 7 via the clutch 8, the rotation of the hollow shaft 4 will cause the milling sleeve 7 to rotate; when the hollow shaft 4 is separated from the milling sleeve 7 via the clutch 8, the milling sleeve 7 will not rotate with the rotation of the hollow shaft 4.

[0028] When using the tool according to this embodiment, after the milling sleeve 7 enters the block pile, the blocks enter the milling sleeve 7. The drill string continues to be lowered. When the milling sleeve 7 can no longer hold the blocks, they are compacted, and the drilling pressure increases significantly. At this time, the drilling fluid flow rate is increased, the power drill bit 2 rotates faster, and drives the internal milling head 9 and the milling sleeve 10 to mill the blocks. During the milling process, the number of blocks in the milling sleeve 7 decreases, and the internal milling head 9 moves axially downward relative to the milling sleeve 7. After moving a certain distance, the upper and lower teeth of the clutch 8 disengage, and the tool is in the following state: Figure 2 As shown, the milling sleeve 7 stops rotating, and only the internal milling head 9 performs high-speed milling on the fallen blocks. The ground blocks form fine rock cuttings that are discharged with the drilling fluid until the drilling pressure increases significantly, indicating that the fallen blocks inside the milling sleeve 7 have been milled out. At this point, the drilling fluid discharge rate is reduced, and the drill string is lifted. The above process is repeated.

[0029] In one embodiment, a thrust bearing 5 is provided at the lower part of the hollow shaft 4. The thrust bearing 5 is arranged inside the milling sleeve 7. A spring seat 73 is provided on the milling sleeve 7. The spring seat 73 has an annular structure. A spring cavity 6 is formed between the spring seat 73 and the thrust bearing 5. A spring 6 is provided in the spring cavity 6. One end of the spring 6 is connected to the thrust bearing 5, and the other end is connected to the spring seat 73.

[0030] The spring seat 73 has a circular structure, and its edge is fixedly connected to the inner wall of the sleeve 7. The center of the spring seat 73 is provided with a through hole. The inner diameter of the through hole is slightly larger than the outer diameter of the hollow shaft 4. The hollow shaft 4 is fitted in the through hole and can slide in the through hole.

[0031] During the milling process, the hollow shaft 4 can move relative to the milling sleeve 7, and the spring 6 will be compressed. After the spring 6 is compressed, it can provide a thrust for the hollow shaft 4 to move, so that it returns to its initial state.

[0032] In one embodiment, the interior of the milling sleeve 7 and the hollow shaft 4 are connected by a clutch 8. The clutch 8 includes a first clutch tooth 82 disposed on the hollow shaft 4 and a second clutch tooth 81 disposed on the milling sleeve 7, and the first clutch tooth 82 and the second clutch tooth 81 can engage. Under normal conditions, due to the elastic force of the spring 6, the first clutch tooth 82 and the second clutch tooth 81 are engaged, and the rotation of the hollow shaft 4 drives the milling sleeve 7 to rotate. When the hollow shaft 4 compresses the spring 6 and moves axially, the first clutch tooth 82 and the second clutch tooth 81 disengage from each other. At this time, the rotation of the hollow shaft 4 will not drive the milling sleeve 7 to rotate.

[0033] During the milling process using the tool described in this embodiment, after the milling sleeve 7 enters the block pile, the blocks enter the milling sleeve 7. The drill string continues to be lowered. When the milling sleeve 7 can no longer hold the blocks, they are compacted, and the drilling pressure increases significantly. At this point, the drilling fluid flow rate is increased, the power drill bit 2 rotates faster, and the internal milling head 9 and the milling sleeve bit 10 mill the blocks. The number of blocks in the milling sleeve 7 decreases, and the internal milling head 9 moves axially downward relative to the milling sleeve 7. The volume in the spring chamber 71 decreases. After moving a certain distance, the upper and lower teeth of the clutch 8 disengage, the spring 6 is further compressed, and the milling sleeve 7 stops rotating. Only the internal milling head 9 mills the blocks at high speed until the drilling pressure increases significantly, indicating that the blocks in the milling sleeve 7 have been milled out.

[0034] At this point, reducing the drilling fluid flow rate and raising the drill string will cause the internal milling head 9 to slide upward relative to the milling sleeve 7 under the action of the spring 6. The upper and lower teeth of the clutch 8 in the milling unit will re-engage, increasing the volume of the spring chamber 71. The milling sleeve 7 will be rotated, and the drill string will be lowered. The milling drill bit 10 will mill the block pile again, and the remaining blocks will enter the milling sleeve 7 again, repeating the previous procedure. After multiple milling operations, when all the downhole blocks have been milled, the above procedure will be repeated. Lowering the drill string will not result in a significant change in drilling pressure, indicating that all the downhole blocks have been milled. This is the feedback from the downhole tools on whether the downhole blocks have been processed. At this point, the drilling fluid will be circulated and the drill string will be pulled out.

[0035] The retrieval cup 3 has a cylindrical structure with a bottom at its lower end, which is connected to the hollow shaft 4.

[0036] If any blocks fall off the wellbore during the tripping process, some of the blocks can fall into the retrieval cup 3 and eventually be pulled to the surface with the drill string.

[0037] In one embodiment, a ring of support ribs is provided on the upper part of the retrieval cup 3, allowing the falling block to fall into the retrieval cup 3 through the gaps between the support ribs. By providing support ribs, it is possible to prevent the falling block from jumping out from the top of the retrieval cup 3.

[0038] In one embodiment, a drain hole 31 is provided on the side wall of the retrieval cup 3. There may be one or more drain holes 31, preferably located on the lower part or bottom of the side of the retrieval cup 3. During the lifting process, liquid entering the retrieval hole will flow out through the drain hole 31, while the fallen piece will not be discharged.

[0039] In one embodiment, the side wall of the milling sleeve 7 is provided with a breathing hole 72 and a chip removal hole 74.

[0040] During the milling process, the crushed rock fragments form fine rock cuttings that are discharged along with the drilling fluid through the chip removal hole 74 at the bottom of the milling sleeve 7 and the inner hole of the milling drill bit 10.

[0041] After milling is completed, the drilling fluid discharge is reduced and the drill string is lifted. Under the action of spring 6, the inner milling head 9 slides upward relative to the milling sleeve 7. The upper and lower teeth of the clutch 8 in the milling unit will re-engage, the volume in the spring chamber 71 will increase, and the drilling fluid will enter the spring chamber 71 through the breathing hole 72. The milling sleeve 7 is driven to rotate, the drill string is lowered, and the milling drill bit 10 mills the debris pile again. The remaining debris enters the milling sleeve 7 again.

[0042] The process of using the downhole block handling tool according to this embodiment includes: During the drilling process, before the tool string reaches the bottom of the well, such as Figure 1 As shown, the internal milling head 9 is positioned in the middle of the milling unit under the action of the spring 6, and the second clutch tooth 81 on the internal milling head 9 meshes with the second clutch tooth 81 on the sleeve milling cylinder 7. If obstruction is encountered during drilling, the pump can be started at a small displacement after the drill bit is lifted. The power drill bit 2 will then drive the hollow shaft 4, the internal milling head 9, and the sleeve milling drill bit 10 to rotate, milling the obstructed part and releasing the obstruction.

[0043] When the tool string reaches the bottom of the well, the pump is started at a low displacement, and the power drill 2 rotates, driving the hollow shaft 4 and the internal milling head 9 at its lower part to rotate. Since the first clutch tooth 82 and the second clutch tooth 81 of the clutch 8 are engaged, the milling sleeve 7 and the milling drill bit 10 also rotate. The milling drill bit 10 mills in the rock pile, and the drill string is slowly lowered. The milling sleeve 7 enters the rock pile, and the rock falls into the milling sleeve 7. The drill string continues to be lowered. When the milling sleeve 7 can no longer hold the rock, the rock is compacted, and the drilling pressure rises significantly. At this time, the drilling fluid discharge rate is increased, the power drill 2 rotates faster, and drives the internal milling head 9 and the milling drill bit 10 to mill the rock. The drilling fluid and fine rock cuttings will be discharged from the chip discharge hole 74 at the bottom of the milling sleeve 7 and the inner hole of the milling drill bit 10, and return to the surface through the annulus.

[0044] During the milling process, the amount of debris falling out inside the milling sleeve 7 will decrease, and the internal milling head 9 will move axially downward relative to the milling sleeve 7. The volume inside the spring chamber 71 will decrease, and the drilling fluid inside will flow out through the breather hole 72. After moving a certain distance, the first clutch tooth 82 and the second clutch tooth 81 will disengage, and the spring 6 will be further compressed. At this time, the tool is in the following state: Figure 2 As shown, the milling sleeve 7 no longer rotates, and only the internal milling head 9 performs high-speed milling on the dropped blocks. The ground dropped blocks form fine rock cuttings that are discharged with the drilling fluid through the chip removal hole 74 at the bottom of the milling sleeve 7 and the inner hole of the milling drill bit 10 until the drilling pressure increases significantly, indicating that the dropped blocks in the milling sleeve 7 have been milled.

[0045] At this point, reducing the drilling fluid flow rate and raising the drill string will cause the internal milling head 9 to slide upward relative to the milling sleeve 7 under the action of the spring 6. The upper and lower teeth of the clutch 8 in the milling unit will re-engage, increasing the volume of the spring chamber 71. The drilling fluid will enter the spring chamber 71 through the breathing hole 72, causing the milling sleeve 7 to rotate. The drill string will then be lowered, and the milling drill bit 10 will mill the fallen block pile again. The remaining fallen blocks will enter the milling sleeve 7 again, repeating the previous procedure. After multiple milling operations, when all the fallen blocks in the well have been milled, the above procedure will be repeated. Lowering the drill string will not result in a significant change in drilling pressure, indicating that all the fallen blocks in the well have been milled. This is the feedback from the downhole tools regarding whether the fallen blocks have been processed. At this point, the drilling fluid will be circulated before tripping the drill string.

[0046] If any blocks fall off the wellbore during the tripping process, some of the blocks can fall into the retrieval cup 3 and eventually be pulled to the surface with the drill string.

[0047] In the above embodiments, when the pump is turned on to mill the dropped blocks, ground equipment such as top drive or rotary table can also drive the drill string to rotate, thus forming a compound rotary milling, which can speed up the processing of dropped blocks.

[0048] According to another aspect of the present invention, a method for processing downhole rock fragments by segmented compaction and milling is also proposed, wherein the downhole rock fragment processing tool is used to perform segmented compaction and milling on the downhole rock fragments.

[0049] The method includes: The dropped block is inserted into the milling sleeve 7 and compacted. The dropped block is then milled into drill cuttings by the milling drill bit 10 and the internal milling head 9, and returned to the surface with the drilling fluid. Raise the drill string again, start the pump, lower the drill string, put the remaining debris into the sleeve, compact it, and grind the debris into drill cuttings through the sleeve milling bit 10 and the internal milling bit 9, and return it to the surface with the drilling fluid circulation. Repeat the above process until the downhole blocks are milled in sections.

[0050] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0051] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] Certain terms are used throughout this application to refer to specific system components. As those skilled in the art will recognize, the same components may often be referred to by different names, and therefore this application is not intended to distinguish components that differ only in name and not in function. The terms "an embodiment" or "embodiment" used in the specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0054] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0055] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and / or modifications falling within the scope of the invention, and all changes and / or modifications made according to embodiments of the invention should be covered within the protection scope of the invention.

Claims

1. A downhole rockfall treatment tool characterized by, include: Drill pipe (1). A power drilling tool (2) is provided at the lower end of the drill rod (1); a hollow shaft (4) is provided at the lower end of the power drilling tool (2), and an internal milling head (9) is provided at the lower end of the hollow shaft (4); and A milling sleeve (7) is disposed below the power drill (2), the milling sleeve (7) is sleeved outside the internal milling head (9), and a milling drill bit (10) is disposed at the lower end of the milling sleeve (7).

2. The downhole block handling tool according to claim 1, characterized in that, The hollow shaft (4) is configured to move along the axial direction of the milling sleeve (7), and a clutch (8) is provided between the hollow shaft (4) and the milling sleeve (7). The hollow shaft (4) moves in the axial direction, thereby connecting or separating the hollow shaft (4) from the milling sleeve (7) through the clutch (8).

3. The downhole block handling tool according to claim 2, characterized in that, A thrust bearing (5) is provided at the lower part of the hollow shaft (4), and the thrust bearing (5) is arranged inside the milling sleeve (7); a spring seat (73) is provided on the milling sleeve (7), and the spring seat (73) and the thrust bearing (5) form a spring (6) cavity, and a spring (6) is provided in the spring (6) cavity. One end of the spring (6) is connected to the thrust bearing (5), and the other end is connected to the spring seat (73).

4. The downhole block handling tool according to claim 3, characterized in that, The clutch (8) includes a first clutch tooth (82) disposed on the hollow shaft (4) and a second clutch tooth (81) disposed on the milling sleeve (7), the first clutch tooth (82) and the second clutch tooth (81) being able to mesh.

5. The downhole block handling tool according to claim 4, characterized in that, The second clutch tooth (81) is located at the lower end of the spring seat (73).

6. The downhole block handling tool according to claim 5, characterized in that, A retrieval cup (3) is provided above the milling sleeve (7). The retrieval cup (3) is connected to the hollow shaft (4), and the opening of the retrieval cup (3) faces upward.

7. The downhole block handling tool according to claim 6, characterized in that, A ring of support ribs is provided on the upper part of the retrieval cup, and the falling block can fall into the retrieval cup (3) through the gaps between the support ribs.

8. The downhole block handling tool according to claim 7, characterized in that, The retrieval cup (3) has a leakage hole (31) on its side wall.

9. The downhole block handling tool according to claim 8, characterized in that, The side wall of the milling sleeve (7) is provided with a breathing hole (72) and a chip removal hole (74).

10. A method for processing downhole block fragments through segmented compaction and milling, characterized in that, The method of using the downhole block handling tool according to any one of claims 1 to 9 to perform segmented compaction and milling of downhole blocks includes: The dropped block is inserted into the milling sleeve (7) and compacted. The dropped block is then milled into drill cuttings by the milling drill bit (10) and the internal milling head (9), and returned to the surface with the drilling fluid. Raise the drill string again, start the pump, lower the drill string, put the remaining scrap into the sleeve and compact it. Use the sleeve milling bit (10) and the internal milling bit (9) to mill the scrap into drill cuttings, and return them to the surface with the drilling fluid circulation. Repeat the above process until the downhole blocks are milled in sections.

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