A flexible shaft, a universal shaft, a drilling system and use of a universal shaft

Abstract

The application discloses a flexible shaft, a universal shaft, a drilling machine system and application of the universal shaft. The flexible shaft can comprise a flexible shaft body and a first connecting head arranged at one end of the flexible shaft body. The first connecting head is used for connecting with a flexible shaft lower connector and is connected with a drill bit through the flexible shaft lower connector. The first connecting head comprises an engaging part, a hinge ball connected with the engaging part and a limiting column connected with the hinge ball. An outer surface of the engaging part is provided with a spline tooth in at least a partial region. The engaging part is used for engaging with a spline type slot on the flexible shaft lower connector through the spline tooth, and the hinge ball is used for hingedly connecting with a ball seat on the flexible shaft lower connector. The limiting column is used for connecting a safety ball for limiting. The flexible shaft in the application greatly reduces the severe impact and vibration from a rotor and a drill bit. The spline tooth of the flexible shaft is engaged with the spline type slot of the flexible shaft lower connector for transmission, high torque and high rotating speed are transmitted, and the service life of the flexible shaft and the universal shaft is prolonged.

Description

Technical Field

[0001] This invention relates to the field of drilling equipment, and particularly to a flexible shaft, a universal joint, a drilling rig system, and the application of the universal joint. Background Technology

[0002] Oil and gas exploration is becoming increasingly complex. Conventional reservoirs are evolving into unconventional reservoirs such as tight oil and gas and shale gas, while homogeneous reservoirs are developing into heterogeneous, thin-layered, faulted, and fractured reservoirs. Shale oil lithology varies greatly, and formation occurrence is difficult to predict. To improve the sweet spot rate of horizontal wells, multi-branch wells, and extended reach wells, it is urgent to improve the drilling efficiency of screw drilling tools and downhole drilling instruments, that is, to increase the drilling time of a single trip of screw drilling tools or downhole drilling instruments.

[0003] Screw drills paired with high-efficiency PDC drill bits are currently the main means of improving drilling speed and directional drilling in complex well structures, and screw drills are used in very large quantities. The most commonly used universal joint structures in screw drills are flexible universal joints, flap universal joints, and spherical universal joints.

[0004] Flexible universal joints have a relatively simple structure. One end connects to the rotor, and the other end connects to the drive shaft. The drive shaft has an angle with the stator centerline, typically 1°, 1.25°, 1.5°, 1.75°, and 2°. Currently, the most commonly used method is the "bent shell screw drill bit combination" for directional drilling. The angle of the commonly used bent shell screw drill bit is generally around 1.5°. Therefore, the left end of the flexible shaft experiences planetary motion, while the right end connects to the bent drive shaft. This results in complex stress, requiring the shaft to withstand large torques and bending moments. Under cyclic load fatigue failure, fatigue fracture occurs after working for more than 100 hours.

[0005] The characteristic of a flap-type universal joint assembly is that each end of the intermediate shaft is connected to a flap-type universal joint. These universal joints consist of flaps of various shapes that mesh with each other. During operation, torque transmission between the flaps occurs through meshing flap teeth, while the intermediate shaft generally plays an auxiliary role in torque transmission. Some flap-type universal joints are structurally designed so that the flap teeth and the intermediate shaft transmit torque together. However, during operation, the flap teeth experience sliding friction and are also subjected to the scouring effect of high-pressure drilling fluid, resulting in rapid wear and a service life of less than 50 hours.

[0006] The third type of universal joint is the spherical universal joint. Its structural feature is point or line contact at the contact surface. The connecting rod swings at a certain angle around the transmission steel ball, simultaneously transmitting speed and torque. This enables the use of adjustable-bend screw drills. However, it requires special reinforcement treatment for certain components, such as the connecting rod and the hinge, to increase their surface wear resistance. Its sealing design requirements are extremely stringent. Tracking field usage revealed frequent issues with wear-resistant parts or seal failure, resulting in a service life of only about 100 hours, necessitating the removal of the drill string. Analysis revealed two main problems: first, the rubber seal sleeve was too thin (5 mm thick), resulting in low mechanical strength, leading to rubber tearing during operation and causing universal joint failure; second, the transmission area of ​​the cylindrical block, ball, or other types of blocks transmitting torque was small, with an effective area of ​​only 700 mm². 2 The left and right sides caused the transmission block to collapse, resulting in the failure of the universal joint.

[0007] Downhole drilling instruments are instrumented screw drill tools, essentially a screw drill tool with a measuring section added to the housing-like parts of the universal joint assembly. The measuring section's interior must pass through the universal joint. Due to the structural characteristics of the measuring section, sensors, batteries, and circuit boards are mounted on its sidewalls, limiting the internal bore size. Downhole drilling instruments are generally used in horizontal sections and have directional requirements, necessitating connection to an adjustable or fixed-angle curved housing. Only two types of universal joints can be used: flexible shafts or spherical universal joints. Given that the service life of flexible shafts and spherical universal joints is only around 100 hours, this limits the instrument's operating time in long horizontal sections of extended reach wells.

[0008] Therefore, developing a universal joint that is truly impact-resistant and has a long service life is a technology that urgently needs to be solved. Summary of the Invention

[0009] In view of the above problems, the present invention is proposed to provide a flexible shaft, universal joint, drilling system and application of universal joint that overcomes or at least partially solves the above problems.

[0010] In a first aspect, embodiments of the present invention provide a flexible shaft, which may include: a flexible shaft body and a first connector disposed at one end of the flexible shaft body; the first connector is used to externally connect to a lower connector of the flexible shaft and to connect to a drill bit through the lower connector of the flexible shaft.

[0011] The first connector includes: an engagement portion, a hinge ball connected to the engagement portion, and a limiting post connected to the hinge ball; at least a portion of the outer surface of the engagement portion is provided with splines.

[0012] The engagement part is used to engage with the spline groove on the external flexible shaft lower connector through the spline teeth, and is connected to the ball seat on the flexible shaft lower connector through the hinge ball, and the limiting post is used to connect to the safety ball for limiting.

[0013] Optionally, the flexible shaft may further include: a second connector disposed at the other end of the flexible shaft body;

[0014] The second connector is used to connect to an external flexible shaft connector and is connected to the motor rotor through the flexible shaft connector.

[0015] Optionally, the diameter ratio of the meshing part, the flexible shaft body and the second connector is (1.4~1.5):1:(1.2~1.3).

[0016] Optionally, the flexible shaft may further include a boss located between the flexible shaft body and the meshing portion; the diameter of the boss is not greater than the diameter of the meshing portion.

[0017] Optionally, the flexible shaft body and the boss, as well as the flexible shaft body and the second connector, are connected by a chamfer of less than 20°.

[0018] Optionally, the chamfered portions between the flexible shaft body and the boss, and between the flexible shaft body and the second connector, are transitioned with a radius greater than R150mm.

[0019] Optionally, the number of teeth in the spline is 6 to 8; the surface area of ​​the spline teeth is not less than 1500 mm². 2 .

[0020] Optionally, the outer surface of the second connector is threaded, and the flexible shaft is used for threaded connection with the upper connector of the flexible shaft via the second connector; and / or

[0021] The outer surface of the limiting post is threaded, and the flexible shaft is used to connect to the safety ball through the limiting post, and is limited to the ellipsoidal groove of the lower connector of the flexible shaft by the safety ball.

[0022] In a second aspect, embodiments of the present invention provide a universal joint, which may include: a housing, a flexible shaft lower connector disposed in the housing, a safety ball, a sealing assembly, and a flexible shaft as described in the first aspect;

[0023] The flexible shaft lower connector is connected to the first connector and sealed by the sealing assembly;

[0024] The flexible shaft lower connector is a hollow structure, and a spline groove matching the spline teeth is opened on the inner side of its sidewall. The flexible shaft lower connector includes a ball seat matching the hinge ball and an ellipsoidal groove matching the safety ball.

[0025] The flexible shaft is disposed within the housing, engages with the spline groove on the lower connector of the flexible shaft via the spline teeth, is connected to the ball seat on the lower connector of the flexible shaft via the hinge ball, and is connected to the safety ball via the limiting post and confined within the ellipsoidal groove on the lower connector of the flexible shaft.

[0026] Optionally, the sealing assembly includes: a sealing ring, a sealing piston, a sealing sleeve, a lock nut, and a sealing plug;

[0027] The flexible shaft further includes a boss located between the flexible shaft body and the meshing portion; the diameter of the boss is not greater than the diameter of the meshing portion.

[0028] The protrusion has an annular groove, and the sealing ring is located in the annular groove;

[0029] The sealing piston is sleeved outside the boss and the sealing ring; the sealing sleeve is sleeved outside at least a portion of the boss and the sealing piston, and abuts against the engagement portion and / or the flexible shaft lower connector;

[0030] The lock nut is fitted onto at least a portion of the sealing sleeve and the outside of the upper end of the flexible shaft lower connector;

[0031] The sealing plug is connected to the lower end of the flexible shaft lower connector to form a sealing cavity between the first connector and the flexible shaft lower connector.

[0032] Optionally, the sealing plug is provided with a plug hole and a plug, the plug hole being used to inject lubricating oil or lubricating fluid into the sealing cavity.

[0033] Optionally, the upper end of the flexible shaft lower connector is provided with an external thread, and the lower end of the flexible shaft lower connector is provided with an internal thread;

[0034] The lock nut and the sealing plug are respectively threaded to the lower connector of the flexible shaft.

[0035] Optionally, the outer surface of the sealing piston is provided with a dovetail groove; the inner surface of the sealing sleeve is provided with a dovetail-shaped protrusion that matches the dovetail groove.

[0036] Optionally, the lower end of the flexible shaft connector is provided with an external thread, and the flexible shaft connector is used for threaded connection with the water cap.

[0037] Optionally, the spherical curvature of the hinge ball is greater than that of the ball seat.

[0038] Optionally, the universal joint may further include: a flexible shaft connector disposed in the housing; the flexible shaft includes a second connector disposed at the other end of the flexible shaft body;

[0039] The flexible shaft is connected to the upper connector of the flexible shaft via the second connector, and the motor rotor is externally connected to the upper connector of the flexible shaft.

[0040] Optionally, the housing includes a fixed bending housing / adjustable bending housing and a stator housing, wherein the fixed bending housing / adjustable bending housing and the stator housing are detachably connected;

[0041] The lower flexible shaft connector, the safety ball, and the sealing assembly are located in the fixed bending housing / the adjustable bending housing, and the upper flexible shaft connector is located in the stator housing; a portion of the flexible shaft is located in the fixed bending housing / the adjustable bending housing, and a portion is located in the stator housing.

[0042] Thirdly, embodiments of the present invention provide an application of the universal joint described in the second aspect in a drilling rig system.

[0043] Fourthly, embodiments of the present invention provide a drilling system, which may include: a motor, a drill bit, and the universal joint described in the second aspect;

[0044] The lower flexible shaft connector in the universal joint is connected to the drill bit via a water cap, and the upper flexible shaft connector in the universal joint is connected to the motor rotor in the motor.

[0045] The beneficial effects of the above-mentioned technical solutions provided in the embodiments of the present invention include at least the following:

[0046] This invention provides a flexible shaft, a universal joint, a drilling system, and the application of the universal joint. The flexible shaft may include: a flexible shaft body and a first connector disposed at one end of the flexible shaft body; the first connector is used to connect to an external flexible shaft lower connector and to a drill bit through the flexible shaft lower connector; the first connector includes: a meshing part, a hinge ball connected to the meshing part, and a limiting post connected to the hinge ball; at least a portion of the outer surface of the meshing part is provided with spline teeth; the meshing part is used to mesh with a spline groove on the external flexible shaft lower connector through the spline teeth, and is connected to a ball seat on the flexible shaft lower connector through the hinge ball; the limiting post is used to connect to a safety ball for limiting.

[0047] The flexible shaft provided in this embodiment of the invention rotates planetarily with the rotor. Under the limiting action of the safety ball, the flexible shaft can only rotate around its centerline within the ball joint of the lower connector. The safety ball rotates simultaneously with the flexible shaft within the ellipsoidal groove of the lower connector, limiting the axial movement of the flexible shaft and significantly reducing the severe impacts and vibrations from the rotor and drill bit. The splined teeth of the flexible shaft mesh with the splined groove of the lower connector, transmitting high torque and high speed. Because the flexible shaft in this embodiment of the invention can effectively alleviate the severe impacts and vibrations from the rotor and drill bit, it improves the service life of both the flexible shaft and the universal joint.

[0048] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0049] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0050] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0051] Figure 1 This is a schematic diagram of the flexural shaft provided in an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the universal joint structure provided in an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of the structure of the flexible shaft lower connector provided in an embodiment of the present invention;

[0054] Figure 4 This is a diagram showing the meshing relationship between spline teeth and spline grooves provided in an embodiment of the present invention.

[0055] Figure 5 This is a schematic diagram illustrating the matching relationship between the safety ball and the ellipsoidal groove of the lower joint of the flexural shaft provided in an embodiment of the present invention;

[0056] Wherein, 1 is the flexible shaft; 2 is the lower connector of the flexible shaft; 3 is the drill bit; 4 is the safety ball; 5 is the upper connector of the flexible shaft; 6 is the motor rotor; 7 is the housing; 8 is the sealing assembly; and 9 is the water cap.

[0057] 11 is the flexible shaft body; 12 is the first connector; 13 is the second connector; 14 is the boss; 121 is the meshing part; 122 is the hinge ball; 123 is the limiting post; 1211 is the spline tooth;

[0058] 21 is a spline groove; 22 is a ball seat; 23 is an ellipsoidal groove;

[0059] 71 is a fixed bending housing; 72 is a stator housing;

[0060] 81 is a sealing ring; 82 is a sealing piston; 83 is a sealing sleeve; 84 is a lock nut; 85 is a sealing plug; 821 is a dovetail groove; 831 is a dovetail protrusion; 851 is a threaded plug. Detailed Implementation

[0061] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0062] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "far," "near," "front," and "rear," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this 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 this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0064] The inventors of this invention aim to solve the technical problem that existing ordinary universal joints cannot meet the short working time of screw drilling tools or downhole drilling instruments in long horizontal sections and build-up sections of horizontal wells and multi-branch wells. The invention provides a working time of more than 250 hours for the "one-trip drilling" stage of horizontal wells, large branch wells, and extended reach wells, or for drilling instruments in long horizontal sections. Its structure is easy to process, can be mass-produced, has strong operability in assembly and disassembly, low processing cost, wear resistance, and long service life.

[0065] This invention provides a flexible shaft that can be applied to the universal joint structure of screw drill bits or downhole drilling instruments. It transmits the high torque and high speed output from the screw motor to the universal joint, which then transmits the torque to the drive shaft and finally to the drill bit. (See reference...) Figures 1-3 As shown, the flexible shaft 1 may include: a flexible shaft body 11 and a first connector 12 disposed at one end of the flexible shaft body 11; the first connector 12 is used to externally connect to the lower connector 2 of the flexible shaft and to connect to the drill bit 3 through the lower connector 2 of the flexible shaft.

[0066] The first connector 12 may include: a meshing part 121, a hinge ball 122 connected to the meshing part 121, and a limiting post 123 connected to the hinge ball 122. At least a portion of the outer surface of the meshing part 121 is provided with spline teeth 1211.

[0067] The meshing part 121 is used to mesh with the spline groove 21 on the external flexible shaft lower connector 2 through the spline teeth 1211, and is ball-jointed with the ball seat 22 on the flexible shaft lower connector 2 through the hinge ball 122. The limiting post 123 is used to connect to the safety ball 4 for limiting.

[0068] The flexible shaft provided in this embodiment of the invention rotates planetarily with the rotor. Under the limiting action of the safety ball, the flexible shaft can only rotate around its centerline within the ball joint of the lower connector. The safety ball rotates simultaneously with the flexible shaft within the ellipsoidal groove of the lower connector, effectively limiting the axial movement of the flexible shaft and mitigating severe impacts and vibrations from the rotor and drill bit. The splined teeth of the flexible shaft mesh with the splined groove of the lower connector, transmitting high torque and high speed. Because the flexible shaft in this embodiment of the invention effectively mitigates severe impacts and vibrations from the rotor and drill bit, it extends the service life of both the flexible shaft and the universal joint.

[0069] In an optional embodiment, refer to Figures 1-3 As shown, the flexible shaft 1 may further include: a second connector 13 disposed at the other end of the flexible shaft body 11;

[0070] The second connector 13 is used to connect to the external flexible shaft connector 5, and is connected to the motor rotor 6 through the flexible shaft connector 5. The motor rotor rotates to transmit torque and speed to the flexible shaft.

[0071] In another alternative embodiment, refer to Figures 1-2 As shown, the diameter ratio of the meshing part 121, the flexible shaft body 11, and the second connector 13 is (1.4~1.5):1:(1.2~1.3).

[0072] In the embodiments of the present invention, the meshing portion is directly the diameter of the tip circle of the spline tooth.

[0073] In another alternative embodiment, refer to Figures 1-2 As shown, the flexible shaft 1 may further include a boss 14 located between the flexible shaft body 11 and the engagement portion 121; the diameter of the boss 14 is not greater than the diameter of the engagement portion 121.

[0074] The boss in this embodiment of the invention is used to seal the connection between the first connector and the lower connector of the flexible shaft.

[0075] In another alternative embodiment, refer to Figures 1-2As shown, the flexible shaft body 11 and the boss 14, as well as the flexible shaft body 11 and the second connector 13, are transitioned by a chamfer of less than 20°.

[0076] In another alternative embodiment, refer to Figures 1-2 As shown, the chamfered portions between the flexible shaft body 11 and the boss 14, and between the flexible shaft body 11 and the second connector 13, are transitioned with a radius greater than R150mm.

[0077] In another alternative embodiment, refer to Figures 1-2 As shown, the number of teeth in spline 1211 is 6 to 8; the surface area of ​​the tooth surface of spline 1211 is not less than 1500 mm². 2 .

[0078] The flexible shaft in this embodiment of the invention differs from current ball joint meshing transmissions or other transmission block meshing transmissions. The spline gear transmission in this embodiment features relatively long spline teeth, resulting in an effective transmission contact area of ​​1500 mm². 2 The area is more than twice that of existing technologies. During operation, the contact stress on the tooth surface is small, the mechanical properties are excellent, the fatigue life is effectively improved, and the service life of the universal joint assembly is increased.

[0079] In another alternative embodiment, refer to Figures 1-2 As shown, the outer surface of the second connector 13 is threaded, and the flexible shaft 1 is used to connect to the connector 5 on the flexible shaft via the second connector 13; and / or

[0080] The outer surface of the limiting post 123 is threaded, and the flexible shaft 1 is used to connect with the safety ball 4 through the limiting post 123, and is limited by the safety ball 4 to be located in the ellipsoidal groove 23 of the lower connector 2 of the flexible shaft.

[0081] The aforementioned flexible shaft in this embodiment of the invention is a slender shaft, wider at both ends and narrower in the middle, transmitting the high torque and high speed output from the motor to the drive shaft of the drill bit. The upper end of the flexible shaft is threaded to a connector on the flexible shaft, which in turn is threaded to the rotor. The middle section of the flexible shaft is the thinnest, transitioning from the middle section to both ends with a small-angle chamfer (less than 20 degrees), and the chamfered section has a large-angle fillet transition (greater than R150mm) to reduce stress concentration. The engaging portion of the first connector on the right end has splines. The length and number of splines are calculated based on structural requirements and mechanical strength. The surface of the splines is reinforced and wear-resistant. The effective area for torque transmission in this patent reaches 1500mm². 2There is still room to increase the effective area; behind the spline teeth is a ball joint, which can rotate with the rotor in the ball seat of the lower joint of the flexible shaft. The ball surface requires high smoothness, with a roughness of less than Ra≤1.6, and the ball surface also needs to be surface-strengthened. Moreover, the curvature of the ball is greater than that of the ball seat. Behind the ball is a cylindrical limiting post with a thread at the end. The outer surface of the flexible shaft exposed in the water hole must have high smoothness, be polished, and indicate that surface strengthening treatment is required. The material selected for the flexible shaft is high-strength alloy steel with a yield strength of approximately 750MPa and a tensile strength of approximately 980MPa.

[0082] Based on the same inventive concept, this invention also provides a universal joint in its embodiments, referring to... Figures 1-3 As shown, the universal joint may include: a housing 7, a flexible shaft lower connector 2 disposed in the housing 7, a safety ball 4, a sealing assembly 8, and the aforementioned flexible shaft 1;

[0083] The lower flexible shaft connector 2 is connected to the first connector 12 and sealed by the sealing assembly 8;

[0084] The flexible shaft lower connector 2 is a hollow structure, and a spline groove 21 matching the spline tooth 1211 is opened on the inner side of its side wall. The flexible shaft lower connector 2 includes a ball seat 22 matching the hinge ball 122 and an ellipsoidal groove 23 matching the safety ball 4.

[0085] The flexible shaft 1 is disposed inside the housing 7. It engages with the spline groove 21 on the lower connector 2 of the flexible shaft via spline teeth 1211, is ball-jointed to the ball seat 22 on the lower connector 2 of the flexible shaft via a hinge ball 122, and is connected to the safety ball 4 via a limiting post 123 and is confined within the ellipsoidal groove 23 on the lower connector 2 of the flexible shaft.

[0086] In this embodiment of the invention, the surface of the safety ball needs to be reinforced. Holes or other flat shapes for disassembly and assembly can be machined on its surface, and an adhesive is applied to its threaded connection to improve the connection strength.

[0087] In this embodiment of the invention, the ball seat and ellipsoidal groove of the flexural shaft lower connector are part of the hollow structure of the aforementioned flexural shaft lower connector.

[0088] In this embodiment of the invention, the flexural shaft is connected to a safety ball, which can rotate simultaneously with the flexural shaft. The safety ball and the flexural shaft are integrated and move together. The safety ball plays a limiting role, which greatly reduces the impact and vibration of the hinge ball, and makes the flexural shaft rotate safely and smoothly. In addition, the safety ball pulls the flexural shaft, giving the flexural shaft an anti-drop function, effectively reducing the occurrence of tripping and drilling safety accidents, and reducing drilling costs.

[0089] Furthermore, the universal joint described above in this embodiment of the invention has a compact overall structure, is easy to machine and manufacture, has low cost, a long service life of more than 250 hours, and is simple for workers to assemble and disassemble.

[0090] In an optional embodiment, Figure 4 This mainly shows the cross-sectional view of the lower connector of the flexible shaft and the flexible shaft, and shows the shape of the spline teeth. The fillet radius of the spline teeth of the flexible shaft must be larger than the fillet radius of the spline groove of the lower connector of the flexible shaft to avoid interference. The size of the gap between the spline teeth and the spline groove is determined by calculation based on the bending angle of the fixed bent shell and the overall length of the lower connector of the flexible shaft, that is: δ1>L×tanθ.

[0091] Figure 5 The gap between the safety ball and the ellipsoidal groove of the lower joint of the deflector shaft is determined by the bending angle of the fixed bent shell and the distance between the center point of the ellipsoidal groove and the center point of the ball seat, i.e., δ2>L1×tanθ.

[0092] In another optional embodiment, the sealing assembly in this invention requires pressing using a specific mold. The sealing sleeve (sealing rubber sleeve) is made of nitrile rubber, which has a certain degree of hardness. The sealing rubber sleeve is relatively thick, with a designed thickness of 20mm according to the structural dimensions, which is four times the thickness of rubber sleeves currently used in technology. It is bonded integrally with the metal sealing piston, and its mechanical strength is at least four times that of existing rubber sleeves. The integrated sealing structure composed of rubber and metal is a dynamic seal, which moves automatically with the rise and fall of the hydraulic pressure inside the cavity. This balances the internal and external pressures and prevents accidents caused by excessive pressure leading to rubber rupture, high-pressure drilling fluid intrusion into the cavity, and the universal joint stopping instantly, forcing the drill string to be pulled out.

[0093] Reference Figure 2 As shown, the sealing assembly 8 may include: a sealing ring 81, a sealing piston 82, a sealing sleeve 83, a lock nut 84, and a sealing plug 85;

[0094] The flexible shaft 1 may further include a boss 14 located between the flexible shaft body 11 and the engagement portion 121; the diameter of the boss 14 is not greater than the diameter of the engagement portion 121.

[0095] The boss 14 has an annular groove (the location of the sealing ring in the figure), and the sealing ring 81 is located in the annular groove;

[0096] The sealing piston 82 is fitted over the boss 14 and the sealing ring 81; the sealing sleeve 83 is fitted over at least a portion of the area of ​​the boss 14 and the sealing piston 82, and abuts against the engagement part 121 and / or the flexible shaft lower connector 2.

[0097] Lock nut 84 is sleeved on at least a portion of the sealing sleeve 83 and the outside of the upper end of the flexible shaft lower joint 2;

[0098] The sealing plug 85 is connected to the lower end of the flexible shaft lower connector 2 so that a sealing cavity is formed between the first flexible shaft lower connector 12 and the flexible shaft lower connector 2.

[0099] The sealing piston and sealing rubber sleeve serve to seal and maintain the internal and external hydraulic balance. The sealing piston, sealing rubber sleeve, and two O-rings can move left and right with the hydraulic pressure within the hydraulic chamber. Utilizing the elasticity of rubber, the sealing rubber sleeve and sealing piston employ a dovetail groove interlocking sealing method, with the lock nut and rubber interlocking to achieve a sealing effect. The sealing plug on the right end has a tapered thread for sealing, and it also has a plug hole and a plug. Hydraulic oil is injected through the plug hole, and the plug provides the seal. Therefore, a closed hydraulic chamber is formed internally, allowing the ball joint universal joint to operate in a sealed environment, free from the erosion of high-pressure drilling fluid, ensuring smooth transmission of torque and speed. The hydraulic oil also provides shock absorption, buffering, and cooling.

[0100] In another alternative embodiment, refer to Figure 2 As shown, the sealing plug 85 is provided with a plug hole and a plug 851. The plug hole is used to inject lubricating oil or lubricating fluid into the sealing cavity. The lubricating oil or lubricating fluid has the functions of shock absorption and cooling, which greatly improves the service life of the universal joint assembly.

[0101] In another alternative embodiment, refer to Figure 2 As shown, the upper end of the flexible shaft lower connector 2 is provided with an external thread, and the lower end of the flexible shaft lower connector 2 is provided with an internal thread.

[0102] Lock nut 84 and sealing plug 85 are threadedly connected to the lower connector 2 of the flexible shaft.

[0103] In this embodiment of the invention, the left end of the flexible shaft lower connector is threaded to a lock nut, and the right end is threaded to a water cap. The spline groove needs to be machined by a CNC milling machine. The keyway milling machine will have rounded corners, or the ball socket needs to be machined by a CNC lathe. There is a gap between the right end of the spline teeth of the flexible shaft and the flexible shaft lower connector. The spherical curvature of the ball joint flexible shaft is larger than the curvature of the ball seat of the flexible shaft lower connector. The arc groove of the flexible shaft lower connector is CNC machined to ensure machining accuracy. The internal thread on the right end is a tapered thread. The sealing plug is connected to the flexible shaft lower connector by a tapered thread. It needs to be sealed with glue when tightened.

[0104] In another alternative embodiment, refer to Figure 2 As shown, the outer surface of the sealing piston 82 is provided with a dovetail groove 821; the inner surface of the sealing sleeve 83 is provided with a dovetail-shaped protrusion 831 that matches the dovetail groove 821.

[0105] The outer surface of the sealing piston is a dovetail groove, and the surface is sandblasted. After that, an adhesive is applied and it is bonded to the sealing sleeve to become a single part for use.

[0106] In another alternative embodiment, refer to Figure 2 As shown, the lower end of the flexible shaft lower connector 2 is provided with an external thread, and the flexible shaft lower connector 2 is used to connect with the water cap 9 by thread.

[0107] In another alternative embodiment, refer to Figure 2 As shown, the spherical curvature of the hinge ball 122 is greater than that of the ball seat 22.

[0108] In another alternative embodiment, refer to Figure 2 As shown, the universal joint may further include: a flexible shaft upper connector 5 disposed in the housing 7; the flexible shaft 1 may include a second flexible shaft lower connector 13 disposed at the other end of the flexible shaft body 11;

[0109] The flexure shaft 1 is connected to the upper flexure shaft 5 via the second lower flexure shaft connector 13, and the motor rotor 6 is externally connected via the upper flexure shaft connector 5 so that the motor rotor 6 drives the flexure shaft 1 to rotate.

[0110] In another alternative embodiment, refer to Figure 2 As shown, the housing 7 includes a fixed bending housing 71 / adjustable bending housing and a stator housing 72, and the fixed bending housing 71 / adjustable bending housing and stator housing 72 are detachably connected.

[0111] The lower flexible shaft connector 2, the safety ball 4, and the sealing assembly 8 are located in the fixed bending housing 71 / adjustable bending housing, and the upper flexible shaft connector 5 is located in the stator housing 762; a portion of the flexible shaft 1 is located in the fixed bending housing 71 / adjustable bending housing, and a portion is located in the stator housing 72.

[0112] In this embodiment of the invention, the housing is an adjustable curved housing or a fixed-angle curved housing configured with a screw drill bit, or the downhole drilling instrument is also configured with an adjustable curved housing or a fixed-angle curved housing, causing the water cap to form a certain angle with the centerline of the screw drill bit housing. Commonly used structural curved angle specifications are generally 1°, 1.25°, 1.5°, 1.75°, and 2°. Currently, the most commonly used method is "curved housing screw drill bit combination" for directional drilling, and the commonly used curved housing screw drill bit angle is generally around 1.5°.

[0113] In a specific example, the deflector shaft follows the motor rotor in planetary rotation. Limited by the safety ball, the deflector shaft can only rotate around its centerline within the ball seat of the lower connector. The safety ball rotates simultaneously with the deflector shaft within the ellipsoidal groove of the lower connector. The safety ball pulls the deflector shaft, significantly reducing the severe impacts and vibrations from the rotor and drill bit. The splined teeth of the deflector shaft mesh with the splined groove of the lower connector, transmitting high torque and high speed. The sealing piston and sealing sleeve function to seal and maintain the internal and external hydraulic balance. The sealing piston, sealing rubber sleeve, and two O-rings can move left and right with the hydraulic lifting and lowering of the deflector shaft within the hydraulic chamber. Utilizing the elasticity of rubber, the sealing sleeve and sealing piston employ a dovetail groove interlocking sealing method, with the lock nut and sealing sleeve interlocking to achieve a sealing effect. The sealing plug on the right end has a tapered thread for sealing and has a plug hole and plug on it. Hydraulic oil is injected through the plug hole, and the plug provides a seal. Therefore, a closed hydraulic cavity is formed between the first connector of the flexible shaft and the lower connector of the flexible shaft, so that the flexible shaft works in a closed environment without the erosion of high-pressure drilling fluid. The torque and speed are transmitted smoothly, and the hydraulic oil has the functions of shock absorption, buffering and cooling.

[0114] Based on the same inventive concept, this embodiment of the invention also provides an application of the above-mentioned universal joint in a drilling rig system.

[0115] Based on the same inventive concept, this invention also provides a drilling system, which may include: a motor and a drill bit, as well as the aforementioned universal joint;

[0116] The lower flexible shaft connector 2 in the universal joint is connected to the drill bit 3 via the water cap 9, and the upper flexible shaft connector 5 in the universal joint is connected to the motor rotor 6 in the motor.

[0117] The technical effects and specific descriptions of the above-described system and the application of the universal joint in the drilling rig system in the embodiments of the present invention can be found in the specific descriptions of the flexible shaft and the universal joint mentioned above. The embodiments of the present invention will not be repeated here.

[0118] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. This disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims. Thus, if these modifications and variations of the invention fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A universal joint, characterized in that, include: Housing, flexible shaft lower connector disposed in the housing, safety ball, sealing assembly and flexible shaft; The flexure shaft includes: a flexure shaft body and a first connector disposed at one end of the flexure shaft body; the first connector is used to connect to an external flexure shaft lower connector and to a drill bit through the flexure shaft lower connector. The first connector includes: an engagement portion, a hinge ball connected to the engagement portion, and a limiting post connected to the hinge ball; at least a portion of the outer surface of the engagement portion is provided with splines. The meshing part is used to mesh with the spline groove on the external flexible shaft lower connector through the spline teeth, and is connected to the ball seat ball joint on the flexible shaft lower connector through the hinge ball, and the limiting post is used to connect to the safety ball for limiting; The flexible shaft lower connector is connected to the first connector and sealed by the sealing assembly; The flexible shaft lower connector is a hollow structure, and a spline groove matching the spline teeth is opened on the inner side of its sidewall. The flexible shaft lower connector includes a ball seat matching the hinge ball and an ellipsoidal groove matching the safety ball. The flexible shaft is disposed within the housing, engages with the spline groove on the lower connector of the flexible shaft via the spline teeth, is connected to the ball seat on the lower connector of the flexible shaft via the hinge ball, and is connected to the safety ball via the limiting post and confined within the ellipsoidal groove on the lower connector of the flexible shaft.

2. The universal joint according to claim 1, characterized in that, The flexible shaft further includes: a second connector disposed at the other end of the flexible shaft body; The second connector is used to connect to an external flexible shaft connector and is connected to the motor rotor through the flexible shaft connector.

3. The universal joint according to claim 2, characterized in that, The diameter ratio of the meshing part, the flexible shaft body and the second connector is (1.4~1.5):1:(1.2~1.3).

4. The universal joint according to claim 3, characterized in that, Also includes: A boss located between the flexible shaft body and the meshing part; the diameter of the boss is not greater than the diameter of the meshing part.

5. The universal joint according to claim 4, characterized in that, The flexible shaft body and the boss, as well as the flexible shaft body and the second connector, are transitioned by a chamfer of less than 20°.

6. The universal joint according to claim 5, characterized in that, The chamfered portions between the flexible shaft body and the boss, and between the flexible shaft body and the second connector, are transitioned with a radius greater than R150mm.

7. The universal joint according to any one of claims 1 to 6, characterized in that, The number of teeth in the spline is 6 to 8; the surface area of ​​the spline teeth is not less than 1500 mm². 2 .

8. The universal joint according to any one of claims 2 to 6, characterized in that, The outer surface of the second connector is threaded, and the flexible shaft is used for threaded connection with the upper connector of the flexible shaft via the second connector; and / or The outer surface of the limiting post is threaded, and the flexible shaft is used to connect to the safety ball through the limiting post, and is limited to the ellipsoidal groove of the lower connector of the flexible shaft by the safety ball.

9. The universal joint according to claim 1, characterized in that, The sealing assembly includes: a sealing ring, a sealing piston, a sealing sleeve, a lock nut, and a sealing plug; The flexible shaft further includes a boss located between the flexible shaft body and the meshing portion; the diameter of the boss is not greater than the diameter of the meshing portion. The protrusion has an annular groove, and the sealing ring is located in the annular groove; The sealing piston is sleeved outside the boss and the sealing ring; the sealing sleeve is sleeved outside at least a portion of the boss and the sealing piston, and abuts against the engagement portion and / or the flexible shaft lower connector; The lock nut is fitted onto at least a portion of the sealing sleeve and the outside of the upper end of the flexible shaft lower connector; The sealing plug is connected to the lower end of the flexible shaft lower connector to form a sealing cavity between the first connector and the flexible shaft lower connector.

10. The universal joint according to claim 9, characterized in that, The sealing plug is provided with a plug hole and a plug, and the plug hole is used to inject lubricating oil or lubricating fluid into the sealing cavity.

11. The universal joint according to claim 9, characterized in that, The upper end of the flexible shaft lower connector is provided with an external thread, and the lower end of the flexible shaft lower connector is provided with an internal thread. The lock nut and the sealing plug are respectively threaded to the lower connector of the flexible shaft.

12. The universal joint according to claim 9, characterized in that, The outer surface of the sealing piston is provided with a dovetail groove; the inner surface of the sealing sleeve is provided with a dovetail-shaped protrusion that matches the dovetail groove.

13. The universal joint according to claim 9, characterized in that, The lower end of the flexible shaft connector is provided with an external thread, and the flexible shaft connector is used for threaded connection with the water cap.

14. The universal joint according to any one of claims 9 to 13, characterized in that, The spherical curvature of the hinge ball is greater than that of the ball seat.

15. The universal joint according to any one of claims 9 to 13, characterized in that, Also includes: A connector is disposed on the flexible shaft within the housing; the flexible shaft includes a second connector disposed at the other end of the flexible shaft body; The flexible shaft is connected to the upper connector of the flexible shaft via the second connector, and the motor rotor is externally connected to the upper connector of the flexible shaft.

16. The universal joint according to any one of claims 9 to 13, characterized in that, The housing includes a fixed bending housing / adjustable bending housing and a stator housing, wherein the fixed bending housing / adjustable bending housing and the stator housing are detachably connected; The lower flexible shaft connector, the safety ball, and the sealing assembly are located in the fixed bending housing / the adjustable bending housing, and the upper flexible shaft connector is located in the stator housing; A portion of the deflector shaft is located within the fixed bending housing / the adjustable bending housing, and a portion is located within the stator housing.

17. An application of a universal joint as described in any one of claims 1 to 16 in a drilling rig system.

18. A drilling rig system, comprising: The motor and drill bit are characterized in that they further include: a universal joint as described in any one of claims 1 to 16; The lower flexible shaft connector in the universal joint is connected to the drill bit via a water cap, and the upper flexible shaft connector in the universal joint is connected to the motor rotor in the motor.

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