A safety connector

Abstract

This invention belongs to the field of downhole workover tool technology, specifically relating to a safety connector. The safety connector includes a lower connector for connecting to a workover tool and an upper connector for connecting to a workover string. The upper and lower connectors have an overlapping section in the axial direction. The upper connector is inserted into the top of the lower connector and locked by a locking structure provided between the upper and lower connectors. The locking structure includes a pressure-pressurizing sleeve to unlock when a pressure-pressurizing ball is inserted into the safety connector and strikes the pressure-pressurizing sleeve downwards. When the upper connector is moved upwards by the workover string, a flushing space is formed in the overlapping section. The upper part of the lower connector is provided with an anti-detachment structure to prevent the upper connector from detaching from the lower connector. Workover fluid is pumped into the flushing space through the annular space between the casing and the upper connector to flush solid debris on the workover tool.

Description

Technical Field

[0001] This invention belongs to the field of downhole working tools technology, and specifically relates to a safety connector. Background Technology

[0002] During well workover operations in oilfields, to remove solid materials adhering to the inner wall of the casing, such as steel slag, burrs, sand, salt deposits, and residual cement from construction, large-diameter workover tools, such as well gauges and scrapers with an outer diameter slightly smaller than the inner diameter of the casing, are typically connected to the lower end of the workover string. These tools are then lowered to the bottom of the well or the designed depth to scrape away the solid debris, thus cleaning and scraping the inner wall of the casing. Workover fluid is then used to circulate and flush the solid impurities to the surface. However, during the cleaning and scraping process, solid debris removed from the inner wall of the casing can easily accumulate on the well gauges, scrapers, and other tools, causing the tubing string to become stuck.

[0003] Currently, to prevent the tubing string from getting stuck, safety joints are generally installed between the gauge, scraper, and workover string. These safety joints include an upper joint for connecting to the lower end of the workover string and a lower joint for connecting workover tools. The gauge, scraper, and other workover tools are then connected to the workover string via the safety joint. In the event of a malfunction in the well, the upper and lower joints can be separated through wellhead operations to release the stuck tubing string.

[0004] Existing safety joints are classified into inverted safety joints, pull-up safety joints, and pressure-slip-sleeve safety joints. An inverted safety joint, such as the one disclosed in patent document CN201738832U, involves an upper and lower joint connected by shear studs. The upper and lower joints are separated by shearing the workover string, which is then cut off. A workover tool with connecting threads is then used to connect the lower joint to the workover string to remove the casing. A pull-up safety joint, such as the one disclosed in patent document CN202165024U, also involves an upper and lower joint connected by shear studs. The upper and lower joints are separated by shearing the string. A pressure-slip-type safety joint, as disclosed in patent document CN205063848U, has an upper part of the locking claw fixedly connected to the upper connector. The lower connector's lower connector groove engages with the inner boss of the locking claw, thus connecting the upper connector, lower connector, and locking claw together. Additionally, a pressure-slip sleeve is provided inside the locking claw. The upper end of the pressure-slip sleeve is connected to the locking claw via a shear pin, and the lower end of the pressure-slip sleeve has an outer boss of the locking claw that engages with the outer boss of the locking claw to stop the inner boss of the locking claw in the lower connector groove. By throwing a pressure ball onto the top of the pressure-slip sleeve and applying a downward force to the pressure-slip sleeve, the shear pin is cut, causing the pressure-slip sleeve to descend. The inner boss of the locking claw disengages from the lower connector groove, thereby disengaging the lower connector.

[0005] Although the aforementioned safety joints can all be removed from the casing by using the workover string, the lower joint remains stuck at the stuck point. Other downhole operations are required, and solid debris at the stuck point must be flushed out before the lower joint can be removed from the casing, resulting in low workover efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a safety connector to solve the technical problem in the prior art where the upper and lower connectors of the safety connector cannot be simultaneously pulled out of the casing, resulting in low well workover efficiency.

[0007] To achieve the above objectives, the safety connector technical solution provided by the present invention is as follows: a safety connector includes a lower connector for connecting to a workover tool and an upper connector for connecting to a workover string. The upper and lower connectors have an overlapping section in the axial direction. The upper connector is inserted into the top of the lower connector and locked by a locking structure provided between the upper and lower connectors. The locking structure includes a pressure-pressurizing sleeve to unlock when a pressure-pressurizing ball is inserted into the safety connector and the pressure-pressurizing ball strikes the pressure-pressurizing sleeve downwards. When the upper connector is moved upwards by the workover string, a flushing space is formed in the overlapping section. The upper part of the lower connector is provided with an anti-detachment structure to prevent the upper connector from detaching from the lower connector. Workover fluid is pumped into the flushing space through the annular space between the casing and the upper connector to flush solid debris on the workover tool.

[0008] The beneficial effects are as follows: Compared with the prior art where the lower and upper connectors completely separate when the safety connector is unstuck, the safety connector provided by this invention has an overlapping section between the upper and lower connectors. The overlapping section has a locking structure for locking the upper and lower connectors. It can be unlocked by inserting a pressure ball into the safety connector and having the pressure ball strike the pressure sleeve downwards. Then, when the upper connector is moved upwards by the workover string, an annular flushing space is formed at the original overlapping position of the upper and lower connectors. Furthermore, the anti-detachment structure set on the upper part of the lower connector can also prevent the upper connector from separating from the lower connector, resulting in the lower connector being suspended on the upper connector. Then, the workover tools can be flushed by the workover fluid entering the flushing space to achieve unstuckness and lift the workover string. This allows the upper connector to drive the lower connector upwards together, so that the workover string can directly bring the upper and lower connectors out of the casing together, avoiding multiple downhole operations, simplifying operation, and improving workover efficiency.

[0009] As a further improvement, the lower connector includes a central tube extending into the upper connector, the upper part of which is provided with a stop step for engaging with the inner circumferential surface of the upper connector, the stop step forming the anti-detachment structure.

[0010] The beneficial effects are: the central tube extends into the upper connector, which facilitates the fit between the lower connector and the upper connector; and the stop sleeve fitted on the central tube serves as an anti-detachment structure, which facilitates installation.

[0011] As a further improvement, an annular platform is protruding on the inner circumferential surface of the upper connector, and a stop sleeve is fitted on the upper part of the central tube. The stop sleeve includes a connecting part for threaded connection with the central tube, and an insert part located below the connecting part for insertion into the annular gap between the annular platform and the central tube from top to bottom. The diameter of the connecting part is larger than the diameter of the insert part, so as to form the stop step between the insert part and the connecting part for stop engagement with the upper end face of the annular platform.

[0012] The beneficial effect is that by setting a stop step on the stop sleeve, the strength of the central tube is avoided by processing the central tube.

[0013] As a further improvement, the lower connector also includes a connector body for connecting to the workover tool. The lower end of the central tube is threaded to the connector body. The external thread at the upper end of the central tube for connecting to the stop sleeve has the opposite rotation direction to the external thread at the lower end of the central tube for connecting to the connector body. An anti-rotation structure is provided between the central tube and the upper connector to achieve anti-rotation engagement between the central tube and the upper connector in the circumferential direction, so as to disengage the central tube from the connector body by rotating the workover string when the upper connector disengages from the lower connector.

[0014] The beneficial effect is that by setting an anti-rotation structure between the central tube and the upper connector, the torque applied to the workover string by the operator can be transferred to the central tube when flushing with workover fluid fails, so that the central tube is separated from the connector body, and then the upper connector is separated from the lower connector, so as to facilitate subsequent downhole operations and bring the upper and lower connectors out of the casing.

[0015] As a further improvement, the inner circumferential surface of the ring platform is prismatic, and the outer circumferential surface of the insert part is prismatic to fit the inner circumferential surface of the ring platform and prevent rotation.

[0016] The beneficial effects are: relying on the outer peripheral surface of the insert part to form an anti-rotation fit with the inner peripheral surface of the ring platform, the structure is simple and easy to manufacture.

[0017] As a further improvement, a transition anti-rotation component is provided between the connector body and the upper connector. One end of the transition anti-rotation component is engaged with the lower connector to prevent rotation, and the other end is engaged with the upper connector to prevent rotation, so as to transfer the torque of the upper connector to the lower connector when the upper and lower connectors have not been unlocked.

[0018] The beneficial effects are: the two ends of the transition anti-rotation component are respectively engaged with the upper and lower connectors to increase the torque transmission between the upper and lower connectors, and the workover tool can be made to swing in the casing by rotating the workover string, which facilitates the release of stuck parts.

[0019] As a further improvement, the transition anti-rotation component is cylindrical, and its outer circumferential surface is prismatic to fit the inner circumferential surface of the ring platform. A shoulder is provided in the middle of the outer circumferential surface. The portion of the transition anti-rotation component above the shoulder is used to insert into the annular gap between the ring platform and the central tube to prevent rotation. The shoulder and the lower end face of the ring platform provide a stop fit. The upper end of the connector body is provided with a press-fit section. The inner diameter of the press-fit section is larger than the inner diameter of the connector body. The inner circumferential surface of the press-fit section is also prismatic to allow the portion of the transition anti-rotation component below the shoulder to insert into the annular gap between the press-fit section and the central tube to prevent rotation.

[0020] The beneficial effects are: the cylindrical transition anti-rotation component is anti-rotationally engaged with the lower and upper joints through the prismatic outer circumferential surface, which is simple in structure and easy to manufacture.

[0021] As a further improvement, the pressure-pressurizing sleeve is connected to the lower connector via a shear pin. The locking structure also includes a movable pin disposed between the upper and lower connectors. The outer circumferential surface of the pressure-pressurizing sleeve is provided with a movable pin groove for the movable pin to fall into when the shear pin is sheared, the pressure-pressurizing sleeve moves down, and the workover string is lifted up, so as to unlock the lower connector from the upper connector.

[0022] As a further improvement, the movable pin groove is an annular groove.

[0023] The beneficial effects are: the larger space of the annular groove makes it easier for the movable pin to fall in, avoiding jamming and improving the reliability of the safety joint.

[0024] As a further improvement, the movable pin has an ellipsoidal structure, and the end of the mounting through hole on the lower connector that allows the movable pin to pass through is provided with a necked section away from the axis of the lower connector to stop the movable pin.

[0025] The beneficial effect is that the mounting hole on the lower connector through which the movable pin passes is provided with a necked section, which prevents the movable pin from falling off the lower connector after the upper and lower connectors are separated, thereby further improving the reliability of the safety connector. Attached Figure Description

[0026] Figure 1 A schematic diagram of the structure of the safety connector provided by the present invention;

[0027] Figure 2 for Figure 1 AA view;

[0028] Figure 3 for Figure 1 BB view;

[0029] Figure 4 A diagram showing the unlocked state of the upper and lower connectors;

[0030] Figure 5 This is a diagram showing the state where the upper and lower connectors are completely disconnected.

[0031] Explanation of reference numerals in the attached drawings: 1. Upper connector; 2. Upper cylinder; 3. Middle cylinder; 4. Lower cylinder; 5. Cylinder insertion section; 6. Locking mating section; 7. Lower connector; 8. Connector body; 9. Central tube; 10. Movable pin; 11. Circular groove; 12. Limiting step; 13. Pressurizing sleeve; 14. Transition anti-rotation component; 15. Shoulder; 16. Stop sleeve; 17. Connecting part; 18. Insertion part; 19. Stopping step; 20. Ring platform; 21. Stopping ring platform; 22. Connecting ring platform; 23. Supporting ring platform; 24. Shear pin; 25. Large diameter section; 26. Small diameter section; 27. Press-fitting section; 28. Shear pin mounting hole; 29. ​​Shear pin mounting groove; 30. Mounting through hole. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0034] It should be noted that, in specific embodiments of the present invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply such an actual relationship or order between these entities or operations. Furthermore, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the use of phrases such as "comprising a…" to define an element does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] In the description of this invention, unless otherwise explicitly specified and limited, terms such as "installation," "connection," and "linkage" 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, or they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] In the description of this invention, unless otherwise explicitly specified and limited, the term "provided with" should be interpreted broadly. For example, the object "provided with" can be a part of the body, or it can be separately arranged from the body and connected to the body. This connection can be a detachable connection or a non-detachable connection. Those skilled in the art can understand the specific meaning of the above terms in this invention through specific circumstances.

[0037] The present invention will be further described in detail below with reference to embodiments.

[0038] Embodiment 1 of the safety connector provided in this invention:

[0039] like Figure 1 As shown, the safety connector includes an upper connector 1 and a lower connector 7. The upper connector 1 is used to connect to the workover string, and the lower connector 7 is used to connect to the workover tool. The upper connector 1 and the lower connector 7 are locked together by a locking structure. The lower connector 7 is provided with a pressure-pressurizing sleeve 13 that can move up and down relative to the lower connector 7. When the safety connector gets stuck between the casing to be workovered, the pressure-pressurizing sleeve 13 can move downwards, causing the locking structure to fail and thus unlocking the upper and lower connectors.

[0040] like Figures 1 to 3 As shown, the upper connector 1 has a cylindrical structure, specifically composed of an upper cylinder 2, a middle cylinder 3, and a lower cylinder 4. The upper cylinder 2 includes a large-diameter section 25 and a small-diameter section 26. The large-diameter section 25 is located above the small-diameter section 26, and its inner circumferential surface has internal threads for connection with the workover string. The outer circumferential surface of the small-diameter section 26 has external threads for connection with the middle cylinder 3. The inner wall of the upper part of the middle cylinder 3 has internal threads for threaded connection with the upper cylinder 2. During connection, the upper end face of the middle cylinder 3 stops against the lower end face of the large-diameter section 25. The lower end of the middle cylinder 3 has a large-diameter cylinder wall section, the inner circumferential surface of which also has internal threads for connection with the lower cylinder 4. The lower cylinder 4 includes a cylinder insertion section 5 and a locking engagement section 6. The cylinder insertion section 5 is connected above the locking engagement section 6. The diameter of the cylinder insertion section 5 is smaller than the diameter of the locking engagement section 6. The outer circumferential surface of the cylinder insertion section 5 is provided with external threads for threaded connection with the middle cylinder 3. A ring platform 20 is protruding on the inner circumferential surface of the upper part of the locking engagement section 6. The inner circumferential surface of the ring platform 20 is prismatic and is used to prevent rotation engagement with the lower connector 7 through the transition anti-rotation member 14. A plurality of circular grooves 11 are provided on the lower inner circumferential surface of the locking engagement section 6. The circular grooves 11 are evenly distributed along the circumference of the lower cylinder 4 for the insertion of the movable pin 10. In addition, the groove opening of each circular groove 11 is a sloping avoidance slope, which allows the avoidance slope to push the movable pin 10 into the movable pin groove of the pressure sliding sleeve 13 when the well workover string and the upper connector 1 are raised. The details of the movable pin 10, the transition anti-rotation component 14, and the pressure-pressurizing sleeve will be explained in detail below.

[0041] The lower connector 7 includes a connector body 8 and a central tube 9. The connector body 8 is a cylindrical structure with a diameter smaller than that of the lower cylindrical body 4 of the upper connector 1. External threads are provided on the outer circumferential surface of the lower part of the connector body 8 for threaded connection with well-working tools such as gauges and scrapers. Multiple mounting through holes 30 are provided in the middle of the connector body 8. These mounting through holes 30 are evenly spaced along the circumference of the connector body 8 and correspond one-to-one with the circular grooves 11 on the lower cylindrical body 4, allowing the movable pin 10 to pass through. It should be noted that the movable pin 10 is generally ellipsoidal, and the diameter of each mounting through hole 30 decreases at the end furthest from the axis of the connector body 8 to form a necked section. During installation, the movable pin 10 needs to be inserted from inside the connector body 8 through the mounting through hole 30 into the circular groove 11 of the upper connector 1. Two shear pin mounting holes 28 are provided above the mounting through holes 30 on the connector body 8 for installing shear pins 24. The connector body 8 has a press-fit section 27 above the shear pin mounting hole 28. The diameter of the inner wall of the press-fit section 27 is larger than the diameter of the rest of the inner wall to press-fit the transition anti-rotation member 14 and to engage with the transition anti-rotation member 14 for anti-rotation. The connector body 8 has sealing ring mounting grooves on its outer circumferential surface below the mounting through hole 30 and above the shear pin mounting hole 28 for embedding the sealing ring and achieving a seal between the connector body 8 and the lower cylinder 4. The connector body 8 has an internal thread on its inner circumferential surface below the press-fit section 27 for connection with the central tube 9. A limiting step 12 is provided on the inner circumferential surface of the connector body 8 below the mounting through hole 30 to stop the pressure-pressing sleeve 13 installed in the connector body 8.

[0042] The central tube 9 has a cylindrical structure. A lower external thread is provided on the lower outer circumference of the central tube 9 for threaded connection with the connector body 8. A stop ring platform 21 is provided on the central tube 9 above the lower external thread for the transition anti-rotation element 14 to sit on the central tube 9. An upper external thread is provided on the upper outer circumference of the central tube 9 for threaded connection with the stop sleeve 16. It should be noted that the upper external thread and the lower external thread have opposite directions of rotation.

[0043] The stop sleeve 16 comprises two parts: a connecting part 17 and an insert part 18. The connecting part 17 is located above the insert part 18. The inner circumferential surface of the connecting part 17 has an internal thread for engaging with the upper internal thread of the central tube 9, allowing the stop sleeve 16 to be screwed onto the central tube 9. The outer circumferential surface of the connecting part 17 has a sealing ring mounting groove for installing a sealing ring to achieve a sealed assembly between the stop sleeve 16 and the upper cylinder 2. The diameter of the insert part 18 is smaller than the diameter of the connecting part 17, forming a stop step 19 between the insert part 18 and the connecting part 17. The outer circumferential surface of the insert part 18 is a prismatic shape adapted to the prismatic inner circumferential surface of the upper annular platform 20 of the lower cylinder 4, so that when the workover string pulls the upper connector 1 upward, the insert part 18 is inserted from top to bottom into the annular gap between the annular platform 20 and the central tube 9, and the insert part 18 engages with the annular platform 20 to prevent rotation. In addition, the stop step 19 and the upper end face of the ring platform 20 are stopped to limit the distance that the upper connector 1 travels with the workover string.

[0044] The transition anti-rotation component 14 is cylindrical, with its outer circumferential surface being a prismatic shape that matches the inner circumferential surface of the ring platform 20, so that both ends of the transition anti-rotation component 14 can respectively engage with the connector body 8 and the lower cylinder 4 to prevent rotation. A shoulder 15 is provided in the middle of the outer circumferential surface of the transition anti-rotation component 14. During installation, the portion of the transition anti-rotation component 14 located below the shoulder 15 is inserted from top to bottom into the gap between the press-fit section 27 of the connector body 8 and the central tube 9, with the shoulder 15 resting on the upper end face of the press-fit section 27. The portion of the transition anti-rotation component 14 located above the shoulder 15 is inserted into the gap between the ring platform 20 of the lower cylinder 4 and the central tube 9, with the lower end face of the ring platform 20 blocking the shoulder 15. Because the upper part of the transition anti-rotation component 14 engages with the ring platform 20 to prevent rotation and the lower part engages with the connector body 8 to prevent rotation, the torque transmission between the upper and lower connectors can be increased.

[0045] The pressure-pressing sleeve 13 has a cylindrical structure. A support ring platform 23 is located at the lower part of its outer circumference, and a connecting ring platform 22 is located at the upper part. Two shear pin mounting grooves 29 are located on the outer circumference of the connecting ring platform 22, corresponding one-to-one with two shear pin mounting holes 28 on the connector body 8 for installing shear pins 24, thereby connecting the pressure-pressing sleeve 13 to the connector body 8. This allows the support ring platform 23 to stop the movable pin 10. An annular movable pin groove is formed between the support ring platform 23 and the connecting ring platform 22, corresponding to the mounting through hole 30 on the connector body 8 when the pressure-pressing sleeve 13 moves downwards, causing the movable pin 10 to fall in and thus separating the upper and lower connectors. A sealing ring mounting groove is located on the outer circumference of the pressure-pressing sleeve 13 for installing a sealing ring to achieve a seal between the pressure-pressing sleeve 13 and the lower connector 7.

[0046] During installation, the lower cylinder 4 is inserted onto the connector body 8. Each movable pin 10 is inserted into the circular groove 11 of the lower cylinder 4 through the mounting through hole 30 on the connector body 8. The pressure sliding sleeve 13 is then installed into the connector body 8, so that the support ring 23 of the pressure sliding sleeve 13 stops inside the movable pin 10. The pressure sliding sleeve 13 is connected to the connector body 8 by the shear pin 24. Then, the transition anti-rotation member 14 is installed in the central tube 9, so that the shoulder 15 of the transition anti-rotation member 14 stops on the upper end face of the connector body 8. The central tube 9 is then screwed into the connector body 8. The diameter of the central tube 9 is smaller than the diameter of the pressure sliding sleeve 13 to stop the pressure sliding sleeve 13. Then, the middle cylinder 3 and the upper cylinder 2 are connected in sequence, so that the upper cylinder 2 and the stop sleeve 16 are sealed together. The part of the upper connector 1 inserted into the lower connector 7 forms an overlapping section between the two. The workover tools are then connected to the connector body 8, and the workover string is connected to the upper cylinder 2.

[0047] When workover tools become stuck between the workover tool and the casing, first rotate the workover string at the wellhead. This will cause the upper connector 1 to rotate, which in turn will cause the lower connector 7 to rotate. The lower connector 7 will then cause the workover tool to sway relative to the casing, dislodging solid debris between the workover tool and the casing to release the stuck part. If rotating the workover string fails to release the stuck part, try pumping workover fluid into the gap between the casing and the workover string. This will allow the workover fluid to flush away solid debris from the workover tool and release it. If the above operations still fail to unlock the device, a pressure ball is inserted downwards from the workover string, and pressure is applied to the pressure ball by pumping fluid into the workover string. This causes the pressure ball to exert a downward force on the pressure sleeve 13, making the pressure sleeve 13 tend to move downwards. At this time, the pressure sleeve 13 will generate a shearing force on the shear pin 24. When the shearing force exceeds the maximum bearing capacity of the shear pin 24, the shear pin 24 is sheared. At this time, the pressure sleeve 13 will move downwards to the limiting step 12, so that the annular movable pin groove on the pressure sleeve 13 is aligned with the mounting through hole 30 on the connector body 8. Then, the workover string is lifted, causing the workover string to drive the upper connector 1 upwards. During the upward movement of the upper connector 1, the avoidance slope on the upper connector 1 will push the movable pin 10 into the movable pin groove, thus unlocking the upper connector 1 and the lower connector 7. Then, the workover string is lifted again. Figure 4As shown, the workover string moves upward with the upper connector 1. When the annular platform 20 of the upper connector 1 engages with the stop step 19 on the stop sleeve 16 at the upper end of the central tube 9, the upper connector 1 reaches its upward limit. The stop step 19 forms an anti-detachment structure, creating an annular flushing space at the overlap section of the upper connector 1 and the lower connector 7 before unlocking. At this time, workover fluid is pumped from the wellhead into the annular space between the casing and the workover string, allowing the workover fluid to enter the flushing space and flush away solid debris on the workover tools. Since the workover tools are not visible from the wellhead, after pumping the workover fluid for a period of time, an attempt is made to lift the workover string. If it can be lifted, the workover string is then lifted to bring the upper and lower connectors 7 out of the casing together. If resistance is still encountered when lifting the workover string, the workover string is rotated. Figure 5 As shown, this causes the central tube 9 to detach from the connector body 8. The upper connector 1 and the central tube 9 are then pulled out of the casing by lifting the workover string. After that, the subsequent downhole unsticking and retrieval work is carried out on the connector body 8 and the workover tools.

[0048] The safety connector provided by this invention, compared with the prior art where the lower and upper connectors completely separate when the safety connector is unstuck, has an overlapping section between the upper and lower connectors. The overlapping section has a locking structure for locking the upper and lower connectors. It can be unlocked by inserting a pressure ball into the safety connector and having the pressure ball strike the pressure sleeve 13 downwards. Then, when the upper connector 1 is moved upward by the workover string, an annular flushing space is formed at the original overlapping position of the upper and lower connectors. Furthermore, the anti-detachment structure on the upper part of the lower connector 7 can prevent the upper connector 1 from separating from the lower connector 7, resulting in the lower connector 7 being suspended on the upper connector 1. Then, the workover fluid entering the flushing space can flush the workover tools to achieve unstuckness and lift the workover string. This allows the upper connector 1 to move the lower connector 7 upward together, so that the workover string can directly bring the upper and lower connectors out of the casing together, avoiding multiple downhole operations, simplifying operation and improving workover efficiency.

[0049] Embodiment 2 of the safety connector provided in this invention:

[0050] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, a stop sleeve 16 is fitted onto the central tube 9, and the stop step 19 on the stop sleeve 16 acts as an anti-detachment structure to stop the upper connector 1. In this embodiment, a stop block is provided on the outer circumferential surface of the central tube 9, and an upward-facing stop groove is provided on the inner circumferential surface of the lower cylinder 4. The stop groove and the stop block form an anti-detachment structure.

[0051] Embodiment 3 of the safety connector provided in this invention:

[0052] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the outer peripheral surface of the insert portion 18 of the stop sleeve 16 is prismatic to stop and cooperate with the prismatic inner peripheral surface of the annular platform 20 of the middle cylinder 3. In this embodiment, a guide block extending in the vertical direction is provided on the outer peripheral surface of the central tube 9, and a guide groove is provided on the outer peripheral surface of the lower cylinder 4. The guide block is inserted into the guide groove to achieve anti-rotation between the lower cylinder 4 and the central tube 9, and the guide block and the guide groove form an anti-rotation structure.

[0053] Embodiment 4 of the safety connector provided in this invention:

[0054] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the transition anti-rotation member 14 increases the torque transmission between the lower cylinder 4 and the lower connector 7. In this embodiment, the transition anti-rotation member 14 is no longer provided, and the torque is transmitted solely by the movable pin 10.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A safety sub comprising a lower sub (7) for connection with a workover tool and an upper sub (1) for connection with a workover string, characterized in that, The upper and lower connectors have an overlapping section in the axial direction. The upper connector (1) is inserted into the top of the lower connector (7) and locked by a locking structure between the upper connector (1) and the lower connector (7). The locking structure includes a pressure sliding sleeve connected to the lower connector (7) by a shear pin (24) to unlock when a pressure ball is inserted into the safety connector and the pressure ball pushes the pressure sliding sleeve (13) downward. When the upper connector (1) is moved upward by the workover string, a flushing space is formed in the overlapping section for pumping workover fluid into the flushing space through the annular space between the casing and the upper connector (1) to flush solid debris on the workover tool. The upper part of the lower connector (7) is provided with an anti-detachment structure to prevent the upper connector (1) from detaching from the lower connector (7) after the locking structure is unlocked.

2. The safety joint of claim 1, wherein, The lower connector (7) includes a central tube (9) extending into the upper connector (1). The upper part of the central tube (9) is provided with a stop step (19) for stopping and engaging with the inner circumferential surface of the upper connector (1). The stop step (19) forms the anti-detachment structure.

3. The safety connector according to claim 2, characterized in that, An annular platform (20) is protruding on the inner circumferential surface of the upper connector (1). A stop sleeve (16) is fitted on the upper part of the central tube (9). The stop sleeve (16) includes a connecting part (17) for threaded connection with the central tube (9) and an insert part (18) located below the connecting part (17) for insertion into the annular gap between the annular platform (20) and the central tube (9) from top to bottom. The diameter of the connecting part (17) is larger than the diameter of the insert part (18) to form the stop step (19) between the insert part (18) and the connecting part (17) for stop engagement with the upper end face of the annular platform (20).

4. The safety connector according to claim 3, characterized in that, The lower connector (7) also includes a connector body (8) for connecting with the workover tool. The lower end of the central tube (9) is threaded to the connector body (8). The external thread at the upper end of the central tube (9) for connecting with the stop sleeve (16) is opposite to the external thread at the lower end of the central tube (9) for connecting with the connector body (8). A non-rotation structure is provided between the central tube (9) and the upper connector (1) to achieve non-rotation engagement between the central tube (9) and the upper connector (1) in the circumferential direction of the central tube (9), so as to disengage the central tube (9) from the connector body (8) by rotating the workover string when the upper connector (1) disengages from the lower connector (7).

5. The safety connector according to claim 4, characterized in that, The inner circumferential surface of the ring platform (20) is prismatic, and the outer circumferential surface of the insert part (18) is prismatic to match the inner circumferential surface of the ring platform (20) and prevent rotation.

6. The safety connector according to claim 5, characterized in that, A transition anti-rotation component (14) is also provided between the connector body (8) and the upper connector (1). One end of the transition anti-rotation component (14) is engaged with the lower connector (7) to prevent rotation, and the other end is engaged with the upper connector (1) to prevent rotation, so that the torque of the upper connector (1) can be transmitted to the lower connector (7) before the upper and lower connectors are unlocked.

7. The safety connector according to claim 6, characterized in that, The transition anti-rotation component (14) is cylindrical. The outer circumferential surface of the transition anti-rotation component (14) is a prismatic shape that matches the inner circumferential surface of the ring platform (20). A shoulder (15) is provided in the middle of the outer circumferential surface. The part of the transition anti-rotation component (14) above the shoulder (15) is used to insert into the annular gap between the ring platform (20) and the central tube (9) to prevent rotation. The shoulder (15) and the lower end face of the ring platform (20) are in a stop-fitting relationship. The upper end of the connector body (8) is provided with a pressing section (27). The inner diameter of the pressing section (27) is larger than the inner diameter of the connector body (8). The inner circumferential surface of the pressing section (27) is also prismatic, so that the part of the transition anti-rotation component (14) below the shoulder (15) can be inserted into the annular gap between the pressing section (27) and the central tube (9) to prevent rotation.

8. The safety connector according to any one of claims 1 to 7, characterized in that, The locking structure also includes a movable pin (10) disposed between the upper connector (1) and the lower connector (7). The outer peripheral surface of the pressure sleeve (13) is provided with a movable pin groove for the movable pin (10) to fall into when the shear pin (24) is sheared, the pressure sleeve (13) moves down, and the workover string is lifted up, so as to unlock the lower connector (7) from the upper connector (1).

9. The safety connector according to claim 8, characterized in that, The movable pin groove is an annular groove.

10. The safety connector according to claim 8, characterized in that, The movable pin (10) has an ellipsoidal structure. The end of the mounting through hole (30) on the lower connector (7) that allows the movable pin (10) to pass through is provided with a necked section away from the axis of the lower connector (7) to stop the movable pin (10).

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