A cross universal joint type ultra-short radius sidetracking flexible drilling tool and a sidetracking construction method

Abstract

The present application relates to the field of oil and gas field old well window sidetracking, and discloses a cross universal joint type ultra-short radius sidetracking flexible drilling tool and a sidetracking construction method, which comprises a flexible drilling tool main body, one end of the flexible drilling tool main body is connected with a clamping end, and the end of the clamping end away from the flexible drilling tool main body is connected with a drill bit main body. Through the clamping end, the clamping seat, the turntable and the socket and other structures arranged, the quick alignment assembly and stable torque transmission between the drill bit main body and the flexible drilling tool main body can be realized. Compared with the rigid threaded connection method used in the prior art, the assembly and disassembly operation is more convenient and efficient, and the connection pair micromotion wear, pre-tightening force attenuation and joint root fatigue fracture caused by the continuous rock breaking impact vibration, build angle alternating lateral eccentric load and torsional stick-slip vibration in the drilling process can be avoided, the risks of drill bit back-off falling, falling into the well and other downhole accidents are avoided from the root, and the continuous and stable development of the drilling operation is ensured.

Description

Technical Field

[0001] This invention relates to the field of side-drilling technology for opening windows in old wells in oil and gas fields, specifically to a cross-shaped universal joint type ultra-short radius flexible side-drilling tool and a side-drilling construction method. Background Technology

[0002] As the development of old onshore oilfields and heavy offshore oilfields in China enters the middle and late stages, the production capacity of the main oil layers is declining year by year, and the near-wellbore zone is seriously polluted. Thin interbedded reservoirs and low-permeability thin-layer reservoirs are restricted by the wellbore trajectory, and conventional horizontal wells cannot achieve close-distance branching sidetracking. Ultra-short radius sidetracking horizontal well technology can complete a 90° turn within a very small section of the vertical well, with the curvature radius of the build-up controlled at 1~3m and the build-up rate reaching more than 15° / m. It can avoid the original wellbore pollution zone, drill multiple branching horizontal wells in close proximity, and significantly increase the oil drainage area of ​​the reservoir. It is a core technical means for stabilizing and increasing production of old wells and tapping the potential of remaining oil at low cost.

[0003] Currently, the mainstream ultra-short radius sidetracking technologies in the industry are divided into two categories: hydraulic jet radial sidetracking technology and articulated flexible drill tool mechanical rock breaking sidetracking technology. Both types of technologies have inherent technical shortcomings and cannot meet the four core requirements of large-diameter drilling, efficient torque transmission, small curvature bending adaptation, and drill tool service life.

[0004] The inventors of this application discovered in their research that the core defect of the aforementioned prior art lies in the following: Under ultra-short radius sidetracking operations, existing drill bits and universal joint-type flexible drill tools generally use rigid threaded joints for transmission connection. During drilling, the drill bit simultaneously bears axial drilling pressure, circumferential rock-breaking torque, and continuous alternating lateral loads caused by the high curvature bending of the build-up section. In addition, the impact loads caused by the alternating soft and hard formations and the stick-slip vibrations generated by the PDC cutting teeth breaking the rock will cause the threaded connection pair to be in a complex alternating stress environment for a long time. After long-term operation, the thread tooth surface is prone to fretting wear and fatigue relaxation, the connection preload continues to decrease, and the rigid joint has significant stress concentration at the root under repeated bending, which easily leads to fatigue cracks that gradually propagate. The above problems can lead to drill bit connection loosening and increased radial runout, resulting in wellbore trajectory loss and abnormal wear of cutting teeth. In severe cases, they can lead to downhole accidents such as drill bit backing off, breakage and falling into the well, forcing the interruption of construction operations and the commencement of salvage operations, significantly increasing construction costs and time losses, and the overall operational reliability and engineering practicality are insufficient. Summary of the Invention

[0005] This invention provides a cross-shaped universal joint type ultra-short radius flexible drilling tool and a side-drilling construction method, which solves the problem that the existing technology mostly uses rigid threaded connections between drill bits and drilling tools, which are prone to falling off due to vibration, and achieves a stable connection of the drill bit and the effect of preventing it from falling off.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a cross-shaped universal joint type ultra-short radius flexible side-drilling tool, comprising a flexible tool body, one end of which is connected to a snap-fit ​​end, and the end of the snap-fit ​​end away from the flexible tool body is connected to a drill bit body. A connecting section is fixedly provided at the end of the drill bit body near the snap-fit ​​end, and a snap-fit ​​seat is fixedly provided at the other end of the connecting section. A protrusion is fixedly provided on the outer periphery of one end surface of the snap-fit ​​seat. A hexagonal snap-fit ​​seat is fixedly provided at the center of the same end face as the protrusion at one end of the snap-fit ​​seat. A slot is provided on the side wall of the hexagonal snap-fit ​​seat, and a locking hole is provided on the end face of the hexagonal snap-fit ​​seat. A turntable is provided between the snap-fit ​​seat and the snap-fit ​​end. An arc-shaped groove is provided on the surface of the turntable, and a recess is distributed on one side of the arc-shaped groove. A push rod extends from the inner side of the arc-shaped groove, and a socket is fixedly connected to the other end of the push rod. A hexagonal frame is provided on the inner side of the snap-fit ​​end, and a through groove is provided on the side wall of the hexagonal frame.

[0007] The outer diameter of the hexagonal card holder is adapted to the inner diameter of the hexagonal frame, and the hexagonal card holder is rotatably connected to the card holder through the bearing seat.

[0008] The push rod and the arc-shaped groove are connected by a snap-fit ​​mechanism.

[0009] As the locking seat comes into contact with the end face of the turntable, multiple protrusions fixed on the outer periphery of one end surface of the locking seat will be engaged in the grooves opened on the surface of the turntable.

[0010] Since the push rod is engaged inside the arc-shaped groove, the push rod can move along with the turntable as it rotates.

[0011] The push rod pushes the socket to move laterally, thereby causing one end of the socket to pass through the inside of the through groove and extend into the slot.

[0012] When the drill bit body moves the locking seat towards the locking end, the locking seat will cause the protrusion to engage with the groove. Therefore, as the locking seat rotates, the protrusion will drive the entire turntable to rotate.

[0013] By adopting the above technical solution, rapid alignment and assembly and stable torque transmission between the drill bit body and the flexible drill tool body can be achieved. Compared with the rigid threaded connection method used in the existing technology, its assembly and disassembly operations are more convenient and efficient. Moreover, it will not cause micro-wear of the connection pair, preload attenuation and fatigue fracture of the joint root due to the continuous rock-breaking impact vibration, lateral load of the drilling, and torsional stick-slip vibration during the drilling process. It avoids the risk of downhole accidents such as drill bit backing off and falling into the well from the root, and ensures the continuous and stable operation of drilling.

[0014] Preferably, the end face of the snap-fit ​​end is provided with an annular groove, and a guide ring is fixed on the surface of the turntable away from the groove.

[0015] Preferably, a return spring is fixedly connected to the bottom of the inner cavity of the snap-fit ​​end, and a locking rod is fixedly connected to the other end of the return spring. An auxiliary sliding plate is sleeved on the outer ring surface of one end of the locking rod, and a dial ring is fixedly connected to one side of the outer ring surface of the auxiliary sliding plate via a rod.

[0016] Preferably, the sidewall of the connecting section is provided with an inclined groove, one end of the inclined groove is connected to a first guide groove, one side of the first guide groove is connected to a second guide groove, an inclined stop block is engaged inside the inclined groove, one end surface of the inclined stop block is fixedly provided with a first guide block engaged inside the first guide groove, and the sidewall of the first guide block is fixedly provided with a second guide block engaged inside the second guide groove.

[0017] Preferably, the flexible drill bit body is connected to a linkage shaft at one end away from the snap-fit ​​end, and a sleeve is fitted on the outer side of the flexible drill bit body.

[0018] Preferably, the protrusions are arranged in a circular array along the center point of the mounting base, and the outer diameter of the protrusions matches the inner diameter of the groove.

[0019] Preferably, the arc-shaped grooves are arranged in a circular array along the center point of the turntable, and the arc-shaped grooves and the turntable form an integrated structure.

[0020] Preferably, the locking rod is slidably connected to the locking end via a return spring, and the outer diameter of the locking rod is adapted to the inner diameter of the locking hole.

[0021] Preferably, a side-drilling construction method for a cross-shaped universal joint type ultra-short radius flexible side-drilling tool includes the following steps: Step 1: When using, first move the clamping seat by moving the drill bit body. At this time, the clamping seat moves the hexagonal clamping seat towards the clamping end. As the hexagonal clamping seat is clamped into the hexagonal frame set on the inner side of the clamping end, the slot and through groove opened on the side wall of the hexagonal clamping seat are on the same horizontal line. Then rotate the drill bit body. As the drill bit body rotates, the clamping seat will rotate accordingly.

[0022] Step Two: As the drill bit body moves towards the locking end, the locking seat causes the protrusion to engage with the groove. As the locking seat rotates, the protrusion drives the entire turntable to rotate. At this time, the rotation of the turntable causes the push rod engaged inside the arc groove to move as well. Under the action of the arc groove, the push rod moves laterally. At this time, the push rod pushes the socket, causing the socket to pass through the inside of the through groove and extend into the slot, realizing a quick connection between the socket and the hexagonal locking seat, and achieving the initial limiting treatment of the hexagonal locking seat.

[0023] Step 3: As the hexagonal chuck is initially positioned, the force applied to the dial ring is released. When the dial ring is moved longitudinally, it drives the auxiliary slide plate to pull the locking rod, which in turn causes the locking rod to deform and generate a reverse force on the return spring. Therefore, when the longitudinal force applied to the dial ring disappears, the reverse force generated by the deformation of the return spring will push the locking rod in the opposite direction, thus inputting one end of the locking rod into the locking hole opened on the end face of the hexagonal chuck. This further achieves the positioning of the hexagonal chuck. With the hexagonal chuck being positioned in multiple ways, a fast and stable connection between the drill bit body and the chuck end can be achieved.

[0024] Step 4: After the main body of the drill string is assembled, the casing is inserted into the wellbore along with the main body of the flexible drill string. The rotation of the linkage shaft can realize the rotation of the entire structure, which facilitates the subsequent use of the rotation of the drill bit body to achieve the purpose of side-drilling. Since the main body of the flexible drill string is a cross universal joint structure, the drilling angle of the drill bit body can be adjusted according to the actual drilling requirements.

[0025] Step 5: Since the inclined block and the inclined groove form a sliding connection, when the drill bit body rotates, the inclined block will expand outward along the inclined groove under the action of centrifugal force. After expansion, the distance between multiple inclined blocks is greater than the diameter of the casing, which can effectively prevent the drill bit body from retracting to the inside of the casing due to external force during drilling operations. Conversely, when the drill bit body stops drilling, the inclined block will reset along the inclined groove under the action of gravity. At this time, the inclined block does not affect the drill bit body from retracting to the inside of the casing, which facilitates the subsequent quick separation of the drill bit body from the casing.

[0026] This invention provides a cross-shaped universal joint type ultra-short radius flexible drilling tool and a side-drilling construction method. It has the following beneficial effects: 1. This invention, through its designed snap-fit ​​end, snap-fit ​​seat, turntable, and socket, enables rapid alignment and assembly and stable torque transmission between the drill bit body and the flexible drill tool body. Compared with the rigid threaded connection method used in the prior art, its assembly and disassembly operations are more convenient and efficient. Moreover, it avoids the micro-wear of the connection pair, preload attenuation, and fatigue fracture at the joint root caused by the continuous rock-breaking impact vibration, lateral load of the drilling, and torsional stick-slip vibration during drilling. It fundamentally avoids the risks of downhole accidents such as drill bit backing off and falling into the well, ensuring the continuous and stable operation of drilling.

[0027] 2. The invention, with its combination of locking rods, inserts, locking holes, and slots, can achieve multi-directional limiting of the drill bit as it connects to the flexible drill bit body. This prevents radial vibration of the drill bit body during subsequent operation, which would otherwise lead to accelerated wear and reduced service life. Overall, the invention has higher practicality and can significantly improve the service life of the drill bit body.

[0028] 3. The present invention, combined with the inclined blocks, inclined grooves, and guide blocks, allows the inclined blocks to expand outward under centrifugal force when the drill bit body rotates. Since the diameter of the circle formed between the inclined blocks after expansion is larger than the size of the casing, it can prevent the drill bit body from retracting into the inner wall of the casing under external force. Conversely, when the drill bit body stops rotating, the inclined blocks will reset under gravity. At this time, simply lifting the drill bit body longitudinally can separate it from the casing, which is convenient, quick, and more flexible. Attached Figure Description

[0029] Figure 1 This is a perspective view of the present invention; Figure 2 This is a side view of the main body of the flexible drill bit of the present invention; Figure 3 This is a side view of the snap-fit ​​end of the present invention; Figure 4 This is a side view of the drill bit body of the present invention; Figure 5 This is a side view of the card holder of the present invention; Figure 6 This is a schematic diagram of the cross-section of the connecting section of the present invention; Figure 7 For the present invention Figure 6 Enlarged view of point A in the middle; Figure 8 This is a schematic diagram of the cross-section of the snap-fit ​​end of the present invention; Figure 9 This is a side view of the turntable of the present invention; Figure 10 This is a schematic diagram of the internal structure of the snap-fit ​​terminal of the present invention; Figure 11 This is a side view of the inclined stop block of the present invention.

[0030] The components are as follows: 1. Flexible drill bit body; 2. Snap-fit ​​end; 3. Drill bit body; 4. Connecting section; 5. Snap-fit ​​seat; 6. Protrusion; 7. Hexagonal snap-fit ​​seat; 8. Slot; 9. Locking hole; 10. Rotary disk; 11. Arc groove; 12. Groove; 13. Push rod; 14. Socket; 15. Hexagonal frame; 16. Through groove; 17. Annular groove; 18. Guide ring; 19. Return spring; 20. Locking rod; 21. Auxiliary slide plate; 22. Dial ring; 23. Inclined groove; 24. First guide groove; 25. Second guide groove; 26. Inclined stop block; 27. First guide block; 28. Second guide block; 29. ​​Linkage shaft; 30. Tubing sleeve. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see the appendix Figure 1 -Appendix Figure 11 This invention provides a cross-shaped universal joint type ultra-short radius flexible drilling tool and a side-drilling construction method, including a flexible drilling tool body 1, a locking end 2 connected to one end of the flexible drilling tool body 1, a drill bit body 3 connected to the end of the locking end 2 away from the flexible drilling tool body 1, a connecting section 4 fixedly provided at the end of the drill bit body 3 near the locking end 2, a locking seat 5 fixedly provided at the other end of the connecting section 4, a protrusion 6 fixedly provided on the outer periphery of one end surface of the locking seat 5, and one end of the locking seat 5 located on the same end face as the protrusion 6. A hexagonal card holder 7 is fixedly provided at the center. The side wall of the hexagonal card holder 7 is provided with a slot 8. The end face of the hexagonal card holder 7 is provided with a locking hole 9. A turntable 10 is provided between the card holder 5 and the card end 2. An arc-shaped groove 11 is provided on the surface of the turntable 10. A groove 12 is distributed on one side of the arc-shaped groove 11. A push rod 13 extends from the inner side of the arc-shaped groove 11. The other end of the push rod 13 is fixedly connected to a socket 14. A hexagonal frame 15 is provided on the inner side of the card end 2. A through groove 16 is provided on the side wall of the hexagonal frame 15.

[0033] The outer diameter of the hexagonal bracket 7 is compatible with the inner diameter of the hexagonal frame 15, and the hexagonal bracket 7 is rotatably connected to the bracket 5 through the bearing seat.

[0034] The push rod 13 and the arc-shaped groove 11 are engaged.

[0035] As the locking seat 5 comes into contact with the end face of the turntable 10, the multiple protrusions 6 fixed on the outer periphery of one end surface of the locking seat 5 will be engaged in the grooves 12 opened on the surface of the turntable 10.

[0036] Since the push rod 13 is engaged inside the arc groove 11, the push rod 13 can move along with the turntable 10 as it rotates.

[0037] The push rod 13 pushes the socket 14 to move laterally, thereby causing one end of the socket 14 to pass through the inside of the through groove 16 and extend into the slot 8.

[0038] When the drill bit body 3 moves the locking seat 5 toward the locking end 2, the locking seat 5 will cause the protrusion 6 to engage with the groove 12. Therefore, as the locking seat 5 rotates, the protrusion 6 will drive the entire turntable 10 to rotate.

[0039] Specifically, during use, the drill bit body 3 drives the connecting section 4 to move. At this time, the connecting section 4 drives the locking seat 5 to move towards the locking end 2. As the locking seat 5 moves, it pushes the hexagonal locking seat 7 to move accordingly. At this time, the hexagonal locking seat 7 will move towards the hexagonal frame 15 set inside the locking end 2. As the hexagonal locking seat 7 connects with the hexagonal frame 15, the end face of the locking seat 5 will contact the end face of the turntable 10, and the slot 8 opened on the side wall of the hexagonal locking seat 7 will move to be on the same horizontal line as the through slot 16.

[0040] It is worth noting that as the locking seat 5 contacts the end face of the turntable 10, the multiple protrusions 6 fixed on the outer periphery of one end surface of the locking seat 5 will be engaged in the groove 12 opened on the surface of the turntable 10, thereby achieving a stable connection between the locking seat 5 and the turntable 10. Then, the locking seat 5 is rotated, and the turntable 10 will also rotate with it. Since the push rod 13 is engaged in the inner side of the arc groove 11, the push rod 13 will also move with it as the turntable 10 rotates. At this time, the push rod 13 pushes the socket 14 to move laterally, so that one end of the socket 14 passes through the inner side of the through groove 16 and extends into the slot 8, thereby achieving the limiting treatment of the hexagonal locking seat 7 and realizing the initial connection between the drill bit body 3 and the locking end 2.

[0041] The bottom of the inner cavity of the snap-fit ​​end 2 is provided with a certain protrusion, and the bottom surface of the socket 14 is attached to the upper surface of the protrusion. The protrusion can provide a certain support for the socket 14, thereby preventing the socket 14 and the push rod 13 from being suspended in the air.

[0042] When the entire device is rotating, the centrifugal force ensures the stability of the connection. When the device stops rotating and remains stationary, the tensile force of the snap-fit ​​structure, such as the socket 14, effectively provides load-bearing capacity. Since the weight of the drill bit body 3 is limited, the load-bearing capacity provided by the snap-fit ​​structure can be used to provide load-bearing effect for the drill bit body 3.

[0043] Please see the appendix Figure 9 and attached Figure 10 The end face of the snap-fit ​​end 2 is provided with an annular groove 17, and a guide ring 18 is fixed on the surface of the turntable 10 away from the groove 12.

[0044] Specifically, during use, as the turntable 10 rotates, the guide ring 18 will rotate along the annular groove 17, thereby improving the stability of the turntable 10 during movement. Since both the guide ring 18 and the annular groove 17 are "L" shaped, the turntable 10 can be engaged with the snap-fit ​​end 2 through the guide ring 18.

[0045] When assembling the guide ring 18 and the annular groove 17, the side of the turntable 10 with the guide ring 18 is aligned with the annular groove 17 of the snap-fit ​​end 2 and pressed axially. The radial flange of the guide ring 18 is snapped into the L-shaped inner cavity of the annular groove 17 by the elastic expansion and contraction of the L-shaped guide ring 18 or the guide chamfer at the entrance of the annular groove 17, thus completing the axial engagement. After engagement, the radial folds of the L-shaped structure hook each other, restricting the axial separation between the turntable 10 and the snap-fit ​​end 2 and preventing the turntable 10 from coming off the snap-fit ​​end 2.

[0046] Please see the appendix Figure 10 A return spring 19 is fixedly connected to the bottom of the inner cavity of the snap-fit ​​end 2. A locking rod 20 is fixedly connected to the other end of the return spring 19. An auxiliary slide plate 21 is sleeved on the outer ring surface of one end of the locking rod 20. A dial ring 22 is fixedly connected to one side of the outer ring surface of the auxiliary slide plate 21 through a rod.

[0047] Specifically, when installing the drill body 3, the dial ring 22 is pre-moved longitudinally. Under the action of the dial ring 22, the auxiliary slide plate 21 moves within the cavity of the locking end 2. The longitudinal movement of the auxiliary slide plate 21 causes the locking rod 20 to press down. As the locking rod 20 is pressed down, the return spring 19 deforms, generating a reverse force. When the longitudinal downward pressure applied to the dial ring 22 disappears, the reverse force generated by the deformation of the return spring 19 pushes the locking rod 20 in the opposite direction, thus inputting one end of the locking rod 20 into the inner side of the locking hole 9. As the locking rod 20 is input into the locking hole 9, one end of the locking rod 20 extends into a hole of the same size at the bottom of the socket 14. This ensures the stability of the socket 14 when it is inserted into the slot 8, and also ensures a stable connection between the drill body 3 and the locking end 2, which is convenient and quick.

[0048] Please see the appendix Figure 6 Appendix Figure 7 and attached Figure 11 The side wall of the connecting section 4 is provided with an inclined groove 23. One end of the inclined groove 23 is connected to a first guide groove 24. One side of the first guide groove 24 is connected to a second guide groove 25. An inclined stop block 26 is engaged inside the inclined groove 23. A first guide block 27 is fixedly provided on the surface of one end of the inclined stop block 26 and engaged inside the first guide groove 24. A second guide block 28 is fixedly provided on the side wall of the first guide block 27 and engaged inside the second guide groove 25.

[0049] Specifically, during use, as the drill bit body 3 rotates, the inclined block 26 slides along the inclined groove 23 under the action of centrifugal force. At this time, the inclined block 26 will drive the first guide block 27 to slide along the first guide groove 24, while the second guide block 28 fixed on both sides of the first guide block 27 will slide along the second guide groove 25, thereby improving the stability of the inclined block 26 during movement. When multiple inclined blocks 26 move to the maximum distance, they stop moving, thereby achieving the limiting treatment of the drill bit body 3.

[0050] The inclined block 26 is slidably connected to the first guide groove 24 via the first guide block 27, while the first guide block 27 is slidably connected to the second guide groove 25 via the second guide block 28.

[0051] Please see the appendix Figure 1 Appendix Figure 2 and attached Figure 3 The flexible drill bit body 1 is connected to a linkage shaft 29 at the end away from the clamping end 2, and a sleeve 30 is fitted on the outer side of the flexible drill bit body 1.

[0052] Specifically, during use, the linkage shaft 29 is connected to an external drive source. The operation of the external drive source enables the linkage shaft 29 to drive the flexible drill body 1 to rotate, which facilitates the subsequent rotation of the drill bit body 3 by utilizing the rotation of the flexible drill body 1. The casing 30 can wrap the flexible drill body 1 and lower it into the wellbore, providing a matching outer casing structure for downhole side-drilling operations. Together with the linkage shaft 29 and the flexible drill, the downhole lowering operation is completed.

[0053] The sleeve 30 can cover the ring 22 fitted on the outside of the snap-fit ​​end 2, preventing impurities such as gravel from entering the ring 22 during the subsequent operation of the entire structure, which would affect the normal movement of the ring 22.

[0054] Please see the appendix Figure 4 Appendix Figure 5 and attached Figure 8 The protrusions 6 are arranged in a circular array along the center point of the snap-fit ​​seat 5, and the outer diameter of the protrusions 6 is matched with the inner diameter of the groove 12.

[0055] Specifically, as the locking seat 5 moves toward the turntable 10, the locking seat 5 will cause the protrusion 6 to engage with the groove 12, thereby realizing the connection between the locking seat 5 and the turntable 10.

[0056] Please see the appendix Figure 9 The arc-shaped grooves 11 are arranged in a circular array along the center point of the turntable 10, and the arc-shaped grooves 11 and the turntable 10 form an integrated structure.

[0057] Specifically, as the turntable 10 rotates, the arc-shaped groove 11 moves synchronously. At this time, as the arc-shaped groove 11 rotates, it pushes the push rod 13, converting the rotational motion into linear motion, so that the push rod 13 pushes the socket 14.

[0058] Please see the appendix Figure 10 The locking rod 20 is slidably connected to the locking end 2 via the return spring 19, and the outer diameter of the locking rod 20 is adapted to the inner diameter of the locking hole 9.

[0059] Specifically, as the locking rod 20 moves, the return spring 19 will also deform and generate a reverse force. This reverse force can then be used to facilitate the subsequent longitudinal reset of the locking rod 20.

[0060] Workflow: During use, the drill bit body 3 drives the connecting section 4 to move. At this time, the connecting section 4 drives the locking seat 5 to move towards the locking end 2. As the locking seat 5 moves, it pushes the hexagonal locking seat 7 to move accordingly. At this time, the hexagonal locking seat 7 will move towards the hexagonal frame 15 set inside the locking end 2. As the hexagonal locking seat 7 connects with the hexagonal frame 15, the end face of the locking seat 5 will contact the end face of the turntable 10, and the slot 8 opened on the side wall of the hexagonal locking seat 7 will move to be on the same horizontal line as the through slot 16.

[0061] It is worth noting that as the locking seat 5 contacts the end face of the turntable 10, the multiple protrusions 6 fixed on the outer periphery of one end surface of the locking seat 5 will be engaged in the grooves 12 opened on the surface of the turntable 10, thereby achieving a stable connection between the locking seat 5 and the turntable 10. Then, the locking seat 5 is rotated, and the turntable 10 is also rotated as the locking seat 5 rotates. As the turntable 10 rotates, the guide ring 18 is rotated along the annular groove 17, thereby improving the stability of the turntable 10 during movement. Since the push rod 13 is engaged in the inner side of the arc groove 11, the push rod 13 is also moved as the turntable 10 rotates. At this time, the push rod 13 pushes the socket 14 to move laterally, so that one end of the socket 14 passes through the inner side of the through groove 16 and extends into the slot 8, thereby achieving the limiting treatment of the hexagonal locking seat 7 and realizing the initial connection between the drill bit body 3 and the locking end 2.

[0062] Subsequently, after the hexagonal retainer 7 is initially limited, the longitudinal pressure applied to the dial ring 22 is released. When the longitudinal downward pressure applied to the dial ring 22 disappears, the reverse force generated by the deformation of the return spring 19 will push the locking rod 20 in the opposite direction, thereby inputting one end of the locking rod 20 into the inside of the locking hole 9, thereby achieving the limiting treatment of the socket 14 and ensuring a stable connection between the drill bit body 3 and the retaining end 2, which is convenient and quick.

[0063] When the overall structure is in operation, it is connected to an external drive source via the linkage shaft 29. The operation of the external drive source enables the linkage shaft 29 to rotate the flexible drill bit body 1, facilitating the subsequent rotation of the drill bit body 3 using the rotation of the flexible drill bit body 1. The casing 30 can wrap the flexible drill bit body 1 and lower it into the wellbore, providing a matching outer casing structure for downhole sidetracking operations. Together with the linkage shaft 29 and the flexible drill bit, the downhole lowering operation is completed. As the drill bit body 3 rotates, the inclined block 26 slides along the inclined groove 23 under the action of centrifugal force. At this time, the inclined block 26 drives the first guide block 27 to slide along the first guide groove 24, while the second guide blocks 28 fixed on both sides of the first guide block 27 slide along the second guide groove 25, thereby improving the stability of the inclined block 26 during movement. When multiple inclined blocks 26 move to the maximum distance, they stop moving, thereby achieving the limiting treatment of the drill bit body 3.

[0064] A side-drilling construction method for a cross-shaped universal joint type ultra-short radius flexible side-drilling tool includes the following steps: Step 1: When in use, the drill bit body 3 drives the locking seat 5 to move in advance. At this time, the locking seat 5 drives the hexagonal locking seat 7 to move towards the locking end 2. As the hexagonal locking seat 7 is locked in the hexagonal frame 15 set on the inner side of the locking end 2, the slot 8 and the through slot 16 opened on the side wall of the hexagonal locking seat 7 are on the same horizontal line. Then rotate the drill bit body 3. As the drill bit body 3 rotates, the locking seat 5 will rotate accordingly.

[0065] Step 2: When the drill bit body 3 moves the locking seat 5 towards the locking end 2, the locking seat 5 will cause the protrusion 6 to engage with the groove 12. Therefore, as the locking seat 5 rotates, the protrusion 6 will drive the entire turntable 10 to rotate. At this time, under the rotation of the turntable 10, the push rod 13 engaged inside the arc groove 11 will also move. Under the action of the arc groove 11, the push rod 13 will move laterally. At this time, the push rod 13 pushes the socket 14, causing the socket 14 to pass through the inside of the through groove 16 and extend into the slot 8, realizing the quick connection between the socket 14 and the hexagonal locking seat 7, and realizing the initial limiting treatment of the hexagonal locking seat 7.

[0066] Step 3: As the hexagonal clasp 7 is initially limited, the force applied to the dial ring 22 is released. When the dial ring 22 is moved longitudinally, it will drive the auxiliary slide plate 21 to pull the locking rod 20, which will cause the locking rod 20 to deform and generate a reverse force. Therefore, when the longitudinal force applied to the dial ring 22 disappears, the reverse force generated by the deformation of the return spring 19 will push the locking rod 20 in the opposite direction, thereby inputting one end of the locking rod 20 into the locking hole 9 opened on the end face of the hexagonal clasp 7, so as to further limit the hexagonal clasp 7. With the hexagonal clasp 7 being limited in multiple ways, a fast and stable connection between the drill bit body 3 and the clamping end 2 can be achieved.

[0067] Step 4: After the main body of the drill string is assembled, the casing 30 is fed into the wellbore along with the flexible drill string body 1. The rotation of the linkage shaft 29 can realize the rotation of the entire structure, which facilitates the subsequent use of the rotation of the drill bit body 3 to achieve the purpose of side drilling. Since the flexible drill string body 1 is a cross universal joint structure, the drilling angle of the drill bit body 3 can be adjusted according to the actual drilling requirements.

[0068] Step 5: Since the inclined block 26 and the inclined groove 23 form a sliding connection, when the drill body 3 rotates, the inclined block 26 will expand outward along the inclined groove 23 under the action of centrifugal force. After expansion, the distance between the multiple inclined blocks 26 is greater than the diameter of the sleeve 30, which can effectively prevent the drill body 3 from retracting to the inside of the sleeve 30 due to external force during drilling. Conversely, when the drill body 3 stops drilling, the inclined block 26 will reset along the inclined groove 23 under the action of gravity. At this time, the inclined block 26 does not affect the drill body 3 from retracting to the inside of the sleeve 30, which facilitates the subsequent quick separation of the drill body 3 from the sleeve 30.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cross-shaped universal joint type ultra-short radius flexible drilling tool, comprising a flexible drilling tool body (1), characterized in that, One end of the flexible drill body (1) is connected to a snap-fit ​​end (2), and the end of the snap-fit ​​end (2) away from the flexible drill body (1) is connected to a drill bit body (3). The drill bit body (3) is fixedly provided with a connecting section (4) at one end near the snap-fit ​​end (2), and a snap-fit ​​seat (5) is fixedly provided at the other end of the connecting section (4). A protrusion (6) is fixedly provided on the outer periphery of one end surface of the snap-fit ​​seat (5), and a hexagonal snap-fit ​​seat (7) is fixedly provided at the center of the same end face as the protrusion (6) at one end of the snap-fit ​​seat (5). A slot is provided on the side wall of the hexagonal snap-fit ​​seat (7). 8) The end face of the hexagonal card holder (7) is provided with a locking hole (9), and a turntable (10) is provided between the card holder (5) and the card end (2). The surface of the turntable (10) is provided with an arc groove (11). A groove (12) is distributed on one side of the arc groove (11). A push rod (13) extends from the inner side of the arc groove (11). The other end of the push rod (13) is fixedly connected to a socket (14). A hexagonal frame (15) is provided on the inner side of the card end (2). A through groove (16) is provided on the side wall of the hexagonal frame (15). The outer diameter of the hexagonal card holder (7) is adapted to the inner diameter of the hexagonal frame (15), and the hexagonal card holder (7) is rotatably connected to the card holder (5) through the bearing seat; The push rod (13) and the arc groove (11) are connected by a snap-fit ​​connection; As the contact seat (5) comes into contact with the end face of the turntable (10), a plurality of protrusions (6) fixed on the outer periphery of one end surface of the contact seat (5) will be engaged in the groove (12) opened on the surface of the turntable (10); Since the push rod (13) is engaged with the inner side of the arc groove (11), the push rod (13) can move along with the rotation of the turntable (10); The push rod (13) pushes the socket (14) to move laterally, thereby causing one end of the socket (14) to pass through the inside of the through groove (16) and extend into the slot (8); When the drill bit body (3) moves the locking seat (5) toward the locking end (2), the locking seat (5) will cause the protrusion (6) to engage with the groove (12). Therefore, as the locking seat (5) rotates, the protrusion (6) will drive the entire turntable (10) to rotate.

2. The cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to claim 1, characterized in that, The end face of the snap-fit ​​end (2) is provided with an annular groove (17), and a guide ring (18) is fixed on the surface of the turntable (10) away from the groove (12).

3. The universal joint type ultra-short radius flexible side-drilling tool according to claim 1, characterized in that, A reset spring (19) is fixedly connected to the bottom of the inner cavity of the snap-fit ​​end (2), and a locking rod (20) is fixedly connected to the other end of the reset spring (19). An auxiliary slide plate (21) is sleeved on the outer ring surface of one end of the locking rod (20), and a dial ring (22) is fixedly connected to one side of the outer ring surface of the auxiliary slide plate (21) through a rod.

4. The universal joint type ultra-short radius flexible side-drilling tool according to claim 1, characterized in that, The side wall of the connecting section (4) is provided with a sloping groove (23). One end of the sloping groove (23) is connected to a first guide groove (24). One side of the first guide groove (24) is connected to a second guide groove (25). A sloping block (26) is engaged with the inner side of the sloping groove (23). A first guide block (27) is fixedly provided on the surface of one end of the sloping block (26) and engaged with the inner side of the first guide groove (24). A second guide block (28) is fixedly provided on the side wall of the first guide block (27) and engaged with the inner side of the second guide groove (25).

5. A cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to claim 1, characterized in that, The flexible drill body (1) is connected to a linkage shaft (29) at one end away from the snap-fit ​​end (2), and a sleeve (30) is fitted on the outer side of the flexible drill body (1).

6. A cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to claim 1, characterized in that, The protrusions (6) are arranged in a circular array along the center point of the card holder (5), and the outer diameter of the protrusions (6) is adapted to the inner diameter of the groove (12).

7. A cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to claim 2, characterized in that, The arc-shaped groove (11) is arranged in a circular array along the center point of the turntable (10), and the arc-shaped groove (11) and the turntable (10) form an integrated structure.

8. A cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to claim 3, characterized in that, The locking rod (20) is slidably connected to the snap-fit ​​end (2) via a return spring (19), and the outer diameter of the locking rod (20) is matched with the inner diameter of the locking hole (9).

9. A side-drilling construction method for a cross-shaped universal joint type ultra-short radius flexible side-drilling drill bit, characterized in that, A cross-shaped universal joint type ultra-short radius flexible side-drilling tool according to any one of claims 1-8 includes the following steps: Step 1: When in use, the drill bit body (3) drives the locking seat (5) to move in advance. At this time, the locking seat (5) drives the hexagonal locking seat (7) to move towards the locking end (2). As the hexagonal locking seat (7) is locked in the hexagonal frame (15) set inside the locking end (2), the slot (8) and the through slot (16) opened on the side wall of the hexagonal locking seat (7) are on the same horizontal line. Then rotate the drill bit body (3). As the drill bit body (3) rotates, the locking seat (5) will rotate accordingly. Step 2: When the drill body (3) drives the snap-fit ​​seat (5) to move towards the snap-fit ​​end (2), the snap-fit ​​seat (5) will cause the protrusion (6) to engage with the groove (12). Therefore, as the snap-fit ​​seat (5) rotates, the protrusion (6) will drive the entire turntable (10) to rotate. At this time, under the rotation of the turntable (10), the push rod (13) engaged in the inner side of the arc groove (11) will also move. Under the action of the arc groove (11), the push rod (13) will move laterally. At this time, the push rod (13) pushes the socket (14), so that the socket (14) passes through the inner side of the through groove (16) and extends into the slot (8), realizing the quick connection between the socket (14) and the hexagonal snap-fit ​​seat (7), and realizing the initial limiting treatment of the hexagonal snap-fit ​​seat (7). Step 3: As the hexagonal clasp (7) is initially limited, the force applied to the dial ring (22) is released. When the dial ring (22) is moved longitudinally, it will drive the auxiliary slide plate (21) to pull the locking rod (20), which will cause the locking rod (20) to deform and generate a reverse force. Therefore, when the longitudinal force applied to the dial ring (22) disappears, the reverse force generated by the deformation of the reset spring (19) will push the locking rod (20) in the opposite direction, and then input one end of the locking rod (20) into the locking hole (9) opened on the end face of the hexagonal clasp (7) to further realize the limiting treatment of the hexagonal clasp (7). With the hexagonal clasp (7) being limited in multiple ways, the drill body (3) and the clamping end (2) can be quickly and stably connected. Step 4: After the main body of the drill bit is assembled, the casing (30) is inserted into the wellbore along with the main body of the flexible drill bit (1). The rotation of the linkage shaft (29) can realize the rotation of the entire structure, which makes it convenient to use the rotation of the drill bit body (3) to achieve the purpose of side drilling. Since the main body of the flexible drill bit (1) is a cross universal joint structure, the drilling angle of the drill bit body (3) can be adjusted according to the actual drilling requirements. Step 5: Since the inclined block (26) and the inclined groove (23) form a sliding connection, when the drill body (3) rotates, the inclined block (26) will expand outward along the inclined groove (23) under the action of centrifugal force. After expansion, the distance between multiple inclined blocks (26) is greater than the diameter of the sleeve (30), which can effectively prevent the drill body (3) from retracting to the inside of the sleeve (30) under the influence of external force during drilling. Conversely, when the drill body (3) stops drilling, the inclined block (26) will reset along the inclined groove (23) under the action of gravity. At this time, the inclined block (26) will not affect the drill body (3) from retracting to the inside of the sleeve (30), which makes it convenient for the drill body (3) to be quickly separated from the sleeve (30) in the future.

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