A downhole expansion unit while drilling

Abstract

The invention discloses a downhole reaming unit while drilling, which belongs to the technical field of drilling tools. The unit comprises an outer shell and a float valve. A notch is provided on the outer shell, a blade is placed in the notch and is rotatably connected to the outer shell, a blade is provided on the side of the blade facing away from the float valve, and a sliding guide groove is provided on the side facing the float valve. The float valve is provided with a strike pin fixedly connected to the float valve, and an end of the strike pin away from the float valve is placed in the sliding guide groove, and the distance between the sliding guide groove and the float valve gradually shortens along the flow direction of the mud. The float valve is placed in the outer shell and is slidably connected to the outer shell, an elastic element is provided between the float valve and a first boss in the outer shell, a channel is provided in the float valve, the minimum inner diameter of the channel is not greater than the outer diameter of a metal ball thrown into the channel, the force applied by the elastic element to the float valve is greater than the impact force on the float valve during normal mud flow, and is less than the force applied by the mud to the float valve when the metal ball is thrown into the channel. The reaming unit can carry out reaming while drilling in a well section where reaming is required, thereby broadening the scope of application.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling tools, in particular to a downhole hole-reaming unit. Background Art

[0002] The general drilling process is drilling, reaming, casing and cementing. The purpose of reaming is to expand the size of the open hole section to make it larger than the outer diameter of the upper casing string to facilitate the insertion of casing.

[0003] Existing reaming drill tools, when used, create a pressure difference or pressure chamber in the drill tool by introducing mud into the drill tool, so that the blades are opened. However, the blades of this structure will open as soon as mud is introduced. Therefore, it is impossible to expand the hole in certain designed well sections that need to be expanded as needed during the drilling process. The drill tool can only be lowered after drilling is completed, which not only limits its scope of use but also increases the operation time.

[0004] Therefore, how to design a downhole reaming unit that can perform reaming while drilling in the well section that requires reaming and only perform drilling operations in other well sections that do not require reaming is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to address the defects and shortcomings in the existing technology and provide a downhole reaming unit that can carry out reaming while drilling in the well section that needs reaming, and only perform drilling operations in other well sections that do not need reaming, thereby broadening the scope of application of the reaming unit.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a downhole reaming while drilling unit, comprising an outer shell and a float valve disposed in the outer shell;

[0008] The outer shell is provided with a notch whose opening size is not smaller than the outer contour of the blade wing, the blade wing is placed in the notch and is rotatably connected to the outer shell, a blade is provided on the side of the blade wing facing away from the float valve, a sliding guide groove is provided on the side of the blade wing facing the float valve, a strike pin for driving the blade wing to open or retract is provided on the float valve, the strike pin is fixedly connected to the float valve, an end of the strike pin away from the float valve is placed in the sliding guide groove, and the distance between the sliding guide groove and the float valve gradually shortens along the flow direction of the mud;

[0009] A first through hole and a first boss are provided inside the outer shell, the float valve is placed in the first through hole and is slidably connected to the first through hole, along the flow direction of the mud, the first boss is located upstream of the notch, an elastic element is provided between the float valve and the first boss, the float valve is provided inside with a channel whose diameter gradually decreases along the flow direction of the mud, the minimum inner diameter of the channel is smaller than the outer diameter of the metal ball thrown into the channel, and the force applied to the float valve by the elastic element is no less than the impact force on the float valve during normal flow of the mud, and is less than the force applied to the float valve by the mud when the metal ball is thrown into the channel.

[0010] Preferably, the float valve is provided with a first water hole and a second water hole, the first water hole and the second water hole both pass through the inner and outer surfaces of the float valve, the inner surface of the outer shell is provided with a first sealing surface for sealing the first water hole and a second sealing surface for sealing the second water hole, a gap is provided between the inner wall of the first through hole and the float valve, along the flow direction of the mud, the gap is located at the lower part of the second sealing surface, the first water hole, the notch, the second water hole and the gap are arranged in sequence along the flow direction of the mud, and the first water hole can be connected with the notch to form a first flow channel for transporting mud to the expansion area, and the second water hole can be connected with the gap to form a second flow channel for transporting mud to the drilling tool.

[0011] Preferably, a second through hole is provided inside the float valve, a ball seat is provided inside the second through hole, a third through hole is provided inside the ball seat, the cross-sectional area of ​​which gradually decreases along the flow direction of the mud, the minimum inner diameter of the third through hole is smaller than the outer diameter of the metal ball thrown into the ball seat, the upstream of the ball seat is connected to the float valve through a shear pin, the downstream of the ball seat is provided with a shaft shoulder, the downstream of the float valve is provided with a boss that can be clamped with the shaft shoulder, and the ball seat is provided with a third water hole that can be connected with the second water hole.

[0012] Preferably, sealing components are provided on the upper and lower sides of the first water hole, the second water hole and the third water hole;

[0013] The blade is rotatably connected to the outer shell through a pin shaft, and the outer shell is also provided with the sealing component in an area between the pin shaft and the notch.

[0014] Preferably, along the flow direction of the mud, a limit block is provided downstream of the float valve, and the limit block is provided with a fourth water hole running through the upper and lower surfaces of the limit block.

[0015] Preferably, a straightening shaft is provided inside the first through hole, and the straightening shaft is detachably connected to the outer shell, and the second sealing surface is the part of the inner surface of the straightening shaft that fits with the float valve; the limit block is located inside the straightening shaft and is detachably connected to the straightening shaft.

[0016] Preferably, along the flow direction of the mud, a joint for connecting to a conventional drilling tool is provided downstream of the outer shell, and the joint is detachably connected to the outer shell.

[0017] Preferably, the centralizing shaft is connected to the outer shell by a snap-fitting manner, the centralizing shaft and the limit block, the joint and the outer shell are all connected by a threaded connection, and the joint abuts against the lower portion of the centralizing shaft.

[0018] Preferably, a limit block is provided on the front side and / or the rear side of the blade wing, and a limit portion is provided on the limit block. Along the rotation direction of the blade wing when the blade is opened, the limit portion is located on the right side of the blade wing, and the distance between the limit portion and the blade wing is adapted to the angle at which the blade is opened.

[0019] Preferably, an inwardly recessed groove is provided on the side of the blade facing the limiting surface, the bottom surface of the groove is a first inclined surface, and the closer to the blade, the deeper the first inclined surface is recessed inward, and a second inclined surface is provided on the limiting portion, and the first inclined surface cooperates with the second inclined surface to limit the opening angle of the blade.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] 1. The present invention provides a float valve and a strike pin fixedly connected to the float valve, and a sliding guide groove is provided on the blade. The strike pin extends into the sliding guide groove and can move relative to the sliding guide groove. An elastic element is provided between the float valve and the first boss. The force applied by the elastic element to the float valve is not less than the force applied to the float valve when the mud flows normally, but less than the force applied to the float valve when the mud is pressurized. When the metal ball is not inserted into the float valve, the drill tool connected to the reaming unit can drill normally. When the metal ball is inserted into the float valve, the blade is opened, and the drill tool connected to the reaming unit can reame while drilling. Compared with the reaming drill tool in which the blade is opened for reaming as long as mud is introduced, the reaming unit of the present application can expand the blade as needed so that it is only expanded in the well section that requires reaming, and other well sections that require conventional drilling remain retracted, thereby broadening the scope of application and shortening the operation time.

[0022] Other technical solutions of the present invention have achieved the following technical effects compared with the prior art:

[0023] 2. The present invention arranges a first water hole and a second water hole on the float valve, and arranges a gap between the inner wall of the first through hole and the float valve. When the float valve moves downstream and causes the blade to open, the first water hole is connected to the slot to form a first flow channel, and the second water hole is connected to the gap to form a second flow channel. Mud is sprayed to the reaming area through the first flow channel to promptly flush the drill tools in the reaming area to prevent mud bags. Mud is sprayed to the drilling area through the second flow channel to promptly flush the drill tools in the drilling area to prevent mud bags. This improves the efficiency of reaming and drilling, and avoids situations such as increased pump pressure, blockage of drill tools, and other situations that affect normal drilling. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a schematic diagram of the cross-sectional structure of the downhole expansion-while-drilling unit;

[0026] Figure 2 Schematic diagram of the cross-sectional structure of the downhole reaming while drilling unit after the metal ball is put in and only the ball seat is moved downward;

[0027] Figure 3 Schematic diagram of the cross-sectional structure of the downhole reaming unit after the float valve is moved downward;

[0028] Figure 4 It is a schematic diagram of the enlarged structure at A;

[0029] Figure 5 This is a schematic diagram of the assembly structure of the limit stopper and the blade;

[0030] Figure 6 It is a schematic diagram of the top cross-sectional structure of the assembly of the limit stopper and the blade;

[0031] Figure 7 Schematic diagram of the structure of the limit stop;

[0032] Figure 8 It is a schematic cross-sectional view of the portion of the limit stop connected to the outer shell;

[0033] Figure 9 Schematic diagram of the structure of the blade;

[0034] Figure 10 This is a schematic diagram of the structure on the other side of the blade;

[0035] Figure 11 It is a schematic diagram of a top view of the structure with a strike-through;

[0036] Figure 12 is a structural diagram of the shear pin;

[0037] Figure 13 Schematic diagram of the structure of the float valve.

[0038] Among them, 1. outer shell; 2. float valve; 3. blade; 4. notch; 5. blade; 6. sliding guide groove; 7. scratch pin; 8. first through hole; 9. first boss; 10. elastic element; 11. metal ball; 12. first water hole; 13. second water hole; 14. first sealing surface; 15. second sealing surface; 16. pore; 17. second through hole; 18. ball seat; 19. third through hole; 20. shear pin; 21. shoulder; 22. second boss; 23. third water hole; 24. sealing component; 25. pin shaft; 26. limit block; 27. fourth water hole; 28. straightening shaft; 29. ​​joint; 30. limit block; 31. limit part; 32. groove; 33. first inclined surface; 34. second inclined surface. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figures 1 to 13 As shown, the present invention provides a downhole reaming while drilling unit, comprising an outer shell 1 and a float valve 2 disposed in the outer shell 1; a notch 4 having an opening size not smaller than the outer contour of a blade wing 3 is provided on the outer shell 1, the notch 4 passes through the inner and outer surfaces of the outer shell 1, the blade wing 3 is disposed in the notch 4 and is rotatably connected to the outer shell 1, a blade 5 is provided on the side of the blade wing 3 facing away from the float valve 2, a sliding guide groove 6 is provided on the side of the blade wing 3 facing the float valve 2, a strike pin 7 for driving the blade wing 3 to open or retract is provided on the float valve 2 capable of axial movement, the strike pin 7 is fixedly connected to the float valve 2, an end of the strike pin 7 away from the float valve 2 is disposed in the sliding guide groove 6, and the distance between the sliding guide groove 6 and the float valve 2 gradually shortens along the flow direction of the mud;

[0042] A first through hole 8 and a first boss 9 are provided inside the outer shell 1. The float valve 2 is placed in the first through hole 8 and is slidably connected to the first through hole 8. Along the flow direction of the mud, the first boss 9 is located upstream of the notch 4. An elastic element 10 is provided between the float valve 2 and the first boss 9. The interior of the float valve 2 is provided with a channel with a diameter gradually decreasing along the flow direction of the mud. The minimum inner diameter of the channel is smaller than the outer diameter of the metal ball 11 thrown into the channel, and the force applied by the elastic element 10 to the float valve 2 is not less than the impact force on the float valve 2 during normal flow of the mud, but less than the force applied by the mud to the float valve 2 when the metal ball 11 is thrown into the channel.

[0043] During conventional drilling, the metal ball 11 is not inserted into the float valve 2, the elastic element 10 is in an extended state, and the float valve 2 is stably located inside the first through hole 8. When reaming is required, the metal ball 11 is inserted into the float valve 2, blocking the passage and causing the mud to be pressurized. After the pressure reaches a certain level, the float valve 2 drives the strike pin 7 downward. Since the distance between the sliding guide groove 6 and the float valve 2 gradually decreases along the direction of the mud flow, when the float valve 2 moves to a certain position, the strike pin 7 will lift the blade 3, causing the blade 3 to open outward to expand the hole, allowing reaming while drilling. After reaming is completed, the pump is stopped, the float valve 2 is reset under the drive of the elastic element 10, and the strike pin 7 follows the float valve 2 in the opposite direction, causing the blade 3 to retract into the notch 4 to remove the drilling tool from the well.

[0044] Compared with the prior art reaming drill tool in which the blade 3 extends as soon as mud is introduced, the downhole reaming unit of the present invention can first use a pilot drill bit for drilling, and after drilling to the designed well section, the ball is dropped to hold the pressure to carry out the reaming operation, thereby achieving controllable reaming. Moreover, drilling can also be carried out while reaming. Under the premise of ensuring the dual functions of reaming and drilling, the two functions of the drill tool can be separated downward, thereby improving the scope of application of the drill tool. After the reaming is completed, the pump is stopped, and under the action of the restoring force of the elastic element 10, the float valve 2 and the stroke pin 7 move upward, and the blade 3 is closed. The process and structural design of the opening and closing of the entire blade 3 are reasonable and easy to operate. In a feasible embodiment, the elastic element 10 is a spring, and the metal ball 11 is a steel ball. See the up and down directions and the left and right directions. Figure 1 , front and back directions see Figure 5 .

[0045] In a feasible embodiment, an area on the sliding guide groove 6 where the distance from the float valve 2 changes is provided with an arc structure, and a flat surface is provided at the lowest point of the arc structure. When the marking pin 7 is on the flat surface, the distance between the slide guide groove 6 and the float valve 2 is the longest, and the blade wing 3 is placed inside the slot 4. At this time, the blade wing 3 is in a retracted state; when the marking pin 7 is at the highest point of the arc structure, the distance between the slide guide groove 6 and the float valve 2 is the shortest, and the part of the blade wing 3 where the blade 5 is provided is pushed out. At this time, the blade wing 3 is in an open state.

[0046] The float valve 2 is provided with a first water hole 12 and a second water hole 13, and the first water hole 12 and the second water hole 13 both pass through the inner and outer surfaces of the float valve 2. The inner surface of the outer shell 1 is provided with a first sealing surface 14 for sealing the first water hole 12 and a second sealing surface 15 for sealing the second water hole 13. A gap 16 is provided between the inner wall of the first through hole 8 and the float valve 2. Along the flow direction of the mud, the gap 16 is located downstream of the second sealing surface 15. The first water hole 12, the slot 4, the second water hole 13 and the gap 16 are arranged in sequence along the flow direction of the mud, and the first water hole 12 can be connected with the slot 4 to form a first flow channel for transporting mud to the expansion area, and the second water hole 13 can be connected with the gap 16 to form a second flow channel for transporting mud to the drilling tool.

[0047] During conventional drilling, the float valve 2 is stably set in the first through hole 8. At this time, the first water hole 12 is in contact with the first sealing surface 14, and the second water hole 13 is in contact with the second sealing surface 15. The mud flows through the first through hole 8 and the channel in sequence to the downstream pilot drill water hole.

[0048] When it is necessary to expand the hole, the float valve 2 moves downward. When the float valve 2 is in the extreme position of downward movement, the first water hole 12 is connected with the slot 4 to form a first flow channel, and the second water hole 13 is connected with the pore 16 to form a second flow channel. A part of the mud flowing through the first through hole 8 and the channel flows to the expansion area through the first flow channel to wash the rock cuttings at the blade 3 to prevent mud bagging of the expansion drill tool; the other part flows to the downstream pilot drill bit water hole through the second flow channel to wash the rock cuttings at the pilot drill bit to prevent mud bagging of the drilling tool, so that the expansion-while-drilling unit can be used for various complex well conditions such as salt-gypsum layer drilling, ultra-deep wells, small clearance wells, side drilling wells, etc., to improve the drilling efficiency of the expansion-while-drilling unit and avoid situations such as increased pump pressure and blockage of drill tools that affect normal drilling.

[0049] A second through hole 17 is provided inside the float valve 2. The channel can be the second through hole 17 or a structure arranged in the second through hole 17. In order to improve the sealing between the float valve 2 and the outer shell 1 during normal drilling, a ball seat 18 is provided inside the second through hole 17. The inside of the ball seat 18 is provided with a third through hole 19 whose diameter gradually decreases along the flow direction of the mud. The minimum diameter of the third through hole 19 is smaller than the outer diameter of the metal ball 11 thrown into the ball seat 18. The upstream of the ball seat 18 is connected to the float valve 2 through a shear pin 20, and the downstream of the ball seat 18 is provided with a shaft shoulder 21. The downstream of the float valve 2 is provided with a second boss 22 that can be engaged with the shaft shoulder 21. A third water eye 23 is provided on the ball seat 18, and the third water eye 23 can be connected to the second water eye 13. At this time, the channel is the third through hole 19.

[0050] When the metal ball 11 is not put into the ball seat 18, the third water hole 23 is not connected to the second water hole 13. At this time, even if the pump pressure is unstable, the float valve 2 floats up and down in the first through hole 8, and the mud will not flow downward through the water hole, but will still flow downward along the route of the first through hole 8, the second through hole 17 and the third through hole 19. When the metal ball 11 is put into the ball seat 18, the metal ball 11 blocks the third through hole 19, so that the mud cannot flow normally. The mud is in a pressurized state. After the pressure reaches a certain level, the shear pin 20 is sheared off, and the ball seat 18 moves downstream along the flow direction of the mud until the shoulder 21 is engaged with the second boss 22. At this time, the third water eye 23 is connected to the second water eye 13, but the second water eye 13 is still in contact with the second sealing surface 15, so the mud continues to be pressurized. When the pressure applied by the mud to the float valve 2 is greater than the supporting force of the elastic element 10, the float valve 2 is pushed downward, thereby opening the blade 3, and connecting the first water eye 12 and the slot 4, and the second water eye 13 and the pore 16, so that the mud can flush the reaming area and the drilling area, so that the reaming unit can reame while drilling.

[0051] In order to further improve the sealing performance, sealing components 24 are provided on the upper and lower sides of the first water hole 12, the second water hole 13 and the third water hole 23. By designing upper and lower seals at the float valve 2 and the ball seat 18, it is ensured that the water holes will not be connected before the float valve 2 and the ball seat 18 move to the corresponding positions; the blade 3 is rotatably connected to the outer shell 1 through the pin shaft 25, and a sealing component 24 is also provided on the outer shell 1 between the pin shaft 25 and the slot 4, which ensures that when the pin shaft 25 is working underground, mud and sand cannot enter the hole where the pin shaft 25 is installed, so that the pin shaft 25 will not be blocked by mud and sand and cause rotation jamming, thereby greatly improving the reliability of the retraction of the blade 3.

[0052] In order to limit the downward movement of the ball seat 18, a limit block 26 is provided downstream of the float valve 2 along the flow direction of the mud. The limit block 26 is provided with a fourth water hole 27 that penetrates the upper and lower surfaces of the limit block 26. The mud flowing to the limit block 26 flows through the fourth water hole 27 to the downstream pilot drill bit water hole.

[0053] In one feasible embodiment, a centering shaft 28 is disposed within the first through hole 8 and is removably connected to the outer shell 1. The second sealing surface 15 is the portion of the inner surface of the centering shaft 28 that contacts the float valve 2. A stopper 26 is located within the centering shaft 28 and is removably connected to the stopper 26. A connector 29 for connecting to conventional drilling tools is disposed downstream of the outer shell 1 in the direction of mud flow. The connector 29 is removably connected to the outer shell 1. Specifically, the centering shaft 28 is connected to the outer shell 1 via a shoulder-to-boss snap-fit ​​connection. The centering shaft 28 and the stopper 26, as well as the connector 29 and the outer shell 1, are both threadedly connected. The connector 29 abuts against the lower portion of the centering shaft 28 to prevent the centering shaft 28 from dislodging. The provision of the connector 29 enables the reaming unit to be connected to conventional drilling tools without requiring dedicated drilling tools, thereby reducing the cost of the downhole reaming unit and improving its ease of use.

[0054] See also Figures 5 to 8 As shown, a limit block 30 is provided on the front and / or rear side of the blade 3. A limit portion 31 is provided on the limit block 30. Along the rotation direction of the blade 3 when the blade 3 is opened, that is, from left to right, the limit portion 31 is located on the right side of the blade 3, and the distance between the limit portion 31 and the blade 3 is adapted to the opening angle of the blade 3. By providing the limit block 30, the rotation angle of the blade 3 can be limited, preventing the blade 3 from increasing in size during the hole expansion process, affecting the hole expansion quality, or even causing damage to the blade 3, making it impossible to retract and leading to underground accidents.

[0055] In one feasible embodiment, the blade 3 is provided with an inwardly recessed groove 32 on the side facing the limiting surface. The bottom surface of the groove 32 is a first bevel 33, and the first bevel 33 is recessed more deeply the closer it is to the blade 5. The limiting portion 31 is provided with a second bevel 34, which cooperates with the second bevel 34 to limit the opening angle of the blade 3. If the blade 3 needs to be opened at a smaller angle, the first bevel 33 and the second bevel 34 are set to have the same inclination direction, and the limiting portion 31 is a protruding block structure. If the blade 3 needs to be opened at a larger angle, the first bevel 33 and the second bevel 34 are set to have opposite inclination directions, and the limiting portion 31 is an inwardly recessed structure. To facilitate replacement of the limit stop 30, the limit stop 30 is detachably connected to the outer shell 1. Specifically, the outer shell 1 is milled with four notches 4, each of which is equipped with a blade 3. The outer shell 1 is milled with eight platform steps, and the limit stop 30 is fixed to the platform steps via threaded connectors. When the opening angle of the blade wing 3 needs to be changed, it is sufficient to replace a different blade wing 3 and a limit block 30 , which is relatively simple and convenient to operate.

[0056] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

Claims

1. A downhole reaming while drilling unit, characterized by: comprising an outer shell and a float valve disposed in the outer shell; The outer shell is provided with a notch whose opening size is not smaller than the outer contour of the blade wing, the blade wing is placed in the notch and is rotatably connected to the outer shell, a blade is provided on the side of the blade wing facing away from the float valve, a sliding guide groove is provided on the side of the blade wing facing the float valve, a strike pin for driving the blade wing to open or retract is provided on the float valve, the strike pin is fixedly connected to the float valve, an end of the strike pin away from the float valve is placed in the sliding guide groove, and the distance between the sliding guide groove and the float valve gradually shortens along the flow direction of the mud; A first through hole and a first boss are provided inside the outer shell, the float valve is placed in the first through hole and is slidably connected to the first through hole, the first boss is located upstream of the notch along the flow direction of the mud, an elastic element is provided between the float valve and the first boss, the float valve is provided inside the float valve with a diameter gradually decreasing along the flow direction of the mud, the minimum inner diameter of the channel is smaller than the outer diameter of a metal ball thrown into the channel, and the force applied to the float valve by the elastic element is no less than the impact force on the float valve during normal mud flow, but less than the force applied to the float valve by the mud when the metal ball is thrown into the channel; The float valve is provided with a first water hole and a second water hole, and the first water hole and the second water hole both pass through the inner and outer surfaces of the float valve. The inner surface of the outer shell is provided with a first sealing surface for sealing the first water hole and a second sealing surface for sealing the second water hole. A gap is provided between the inner wall of the first through hole and the float valve, and the gap is located at the lower part of the second sealing surface along the flow direction of the mud. The first water hole, the notch, the second water hole and the gap are arranged in sequence along the flow direction of the mud, and the first water hole can be connected with the notch to form a first flow channel for transporting mud to the expansion area, and the second water hole can be connected with the gap to form a second flow channel for transporting mud to the drilling tool.

2. The downhole reaming while drilling unit according to claim 1, characterized in that: A second through hole is provided inside the float valve, a ball seat is provided inside the second through hole, a third through hole is provided inside the ball seat, the diameter of which gradually decreases along the flow direction of the mud, the minimum inner diameter of the third through hole is smaller than the outer diameter of the metal ball thrown into the ball seat, the upstream of the ball seat is connected to the float valve through a shear pin, the downstream of the ball seat is provided with a shaft shoulder, the downstream of the float valve is provided with a boss that can be clamped with the shaft shoulder, and the ball seat is provided with a third water hole that can be connected with the second water hole.

3. The downhole reaming while drilling unit according to claim 2, characterized in that: Sealing components are provided on the upper and lower sides of the first water hole, the second water hole and the third water hole; The blade is rotatably connected to the outer shell through a pin shaft, and the outer shell is also provided with the sealing component in an area between the pin shaft and the notch.

4. The downhole reaming while drilling unit according to any one of claims 1 to 3, characterized in that: Along the flow direction of the mud, a limit block is provided downstream of the float valve, and the limit block is provided with a fourth water hole running through the upper and lower surfaces of the limit block.

5. The downhole reaming while drilling unit according to claim 4, characterized in that: A righting shaft is provided inside the first through hole, and the righting shaft is detachably connected to the outer shell. The second sealing surface is the portion of the inner surface of the righting shaft that fits with the float valve. The limit block is located inside the righting shaft and is detachably connected to the righting shaft.

6. The downhole reaming while drilling unit according to claim 5, characterized in that: Along the flow direction of the mud, a joint for connecting with a conventional drilling tool is provided downstream of the outer shell, and the joint is detachably connected to the outer shell.

7. The downhole reaming while drilling unit according to claim 6, characterized in that: The centralizing shaft is connected to the outer shell by a clamping connection, the centralizing shaft is connected to the limit block, and the joint is connected to the outer shell by a threaded connection, and the joint abuts against the lower part of the centralizing shaft.

8. The downhole reaming while drilling unit according to claim 1 or 7, characterized in that: A limit block is provided on the front side and / or the rear side of the blade wing, and a limit portion is provided on the limit block. Along the rotation direction of the blade wing when the blade is opened, the limit portion is located on the right side of the blade wing, and the distance between the limit portion and the blade wing is adapted to the opening angle of the blade wing.

9. The downhole reaming while drilling unit according to claim 8, characterized in that: A groove recessed inward is provided on the side of the blade facing the limiting portion, the bottom surface of the groove is a first inclined surface, and the closer to the blade, the deeper the first inclined surface recesses inward. A second inclined surface is provided on the limiting portion, and the first inclined surface cooperates with the second inclined surface to limit the opening angle of the blade.

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