A safety joint for oilfield sucker rods

Abstract

The present application relates to a kind of oilfield sucker rod safety joint. Mainly solve the problem that the existing sucker rod safety joint is easy to appear not to open phenomenon when unjamming. The upper joint (1) lower end is provided with double-acting sliding sleeve (6), the upper joint (1) is connected with double-acting sliding sleeve (6) by the rectangular convex edge (62) of axial direction, the upper joint (1) lower end is connected with shear clamp spring (7) by clamping groove (13), and shear clamp spring (7) is located in the lower end of double-acting sliding sleeve (6);The lower end of double-acting sliding sleeve (6) is connected with lower joint (5) by thread, and double-acting sliding sleeve (6) and lower joint (5) are provided with radial torque shear pin (4).The oilfield sucker rod safety joint is not affected by liquid medium scaling solidification in well, can be through lifting the rated load of sucker rod to make safety joint break away or reverse break away, avoid the phenomenon that joint is not opened when unjamming.

Description

Technical Field

[0001] This invention relates to the field of oil production engineering, specifically to a safety joint for oilfield sucker rods. Background Technology

[0002] Currently, during sucker rod removal operations in oilfields, jamming often occurs due to the sucker rod, piston, or rotor becoming stuck inside the pump or tubing with sand, wax, or scale. When methods such as moving, vibrating, and hot washing fail to remove the jamming, methods such as reverse pulling, upward pulling, and simultaneous rod and tubing removal can be employed. However, reverse pulling can easily cause multiple loosenings in the sucker rod connections, requiring repeated retrieval, resulting in high time and cost. Upward pulling can lead to breakage when the load exceeds the sucker rod's tensile strength, often requiring multiple retrievals, again resulting in high time and cost. Simultaneous rod and tubing removal requires removing a section of tubing and cutting off a section of sucker rod, further contributing to high time and cost.

[0003] To prevent the aforementioned phenomena, oilfields currently install pin-shear or disengageable safety joints on the sucker rod string. When conventional unblocking of the rod string fails and the rod string is pulled up to the breaking load of the sucker rod safety joint, the pin-shear safety joint will shear off and disengage, while the male and female parts of the disengageable safety joint will separate, achieving segmental unblocking and improving construction efficiency. However, in practical applications, sucker rod safety joints often fail to disengage. The reason for this is that the various parts of the safety joint, after long-term immersion in the liquid medium in the well, cause scale to form and solidify together, thus negating the function of the sucker rod safety joint. Summary of the Invention

[0004] To overcome the shortcomings of existing sucker rod safety joints that are prone to failure to detach during unblocking, this invention provides an oilfield sucker rod safety joint that is unaffected by scaling and solidification of the liquid medium in the well. The safety joint can be disengaged by pulling the sucker rod under its rated load or by reverse-clamping it off, thus avoiding the phenomenon of the joint failing to detach during unblocking.

[0005] The technical solution of the present invention is: a safety connector for oilfield sucker rods, comprising an upper connector and a lower connector. The upper end of the upper connector is connected to an upper sucker rod via an internal thread, and the lower connector is connected to a lower sucker rod via an external thread. A double-acting sleeve is provided on the outer side of the lower end of the upper connector. The upper connector and the double-acting sleeve are connected by an axial rectangular protrusion. A shear spring is connected to the lower end of the upper connector via a slot, and the shear spring is located at the lower end of the double-acting sleeve. The lower connector is connected to the outer side of the double-acting sleeve via a thread, and a radial torque shear pin is provided between the double-acting sleeve and the lower connector.

[0006] The outer surface of the upper connector where it mates with the double-acting sleeve has several axial rectangular grooves, and the inner surface of the double-acting sleeve has rectangular protrusions that mate with the rectangular grooves. The mate between the rectangular grooves and the rectangular protrusions prevents axial rotation between the upper connector and the double-acting sleeve.

[0007] An upper O-ring is provided between the upper connector and the double-acting sliding sleeve, and a lower O-ring is provided between the double-acting sliding sleeve and the lower connector.

[0008] The thread between the double-acting sleeve and the lower connector is a four-start trapezoidal thread.

[0009] The double-acting sleeve has a radial circular hole, and the torque shear pin passes through the side wall of the lower connector and is located inside the circular hole.

[0010] The torque shear pin includes a left cylinder and a right cylinder, which are connected by a central steel plate.

[0011] The shear spring includes an inner ring and an outer ring. The inner ring is located in the slot of the upper connector, and there are two inner grooves at the connection between the inner ring and the outer ring.

[0012] The present invention has the following beneficial effects: Due to the above-mentioned solution, the safety joint is not affected by the scaling and solidification of the liquid medium in the well, overcoming the shortcomings of the existing safety joints which cannot safely detach under rated lifting load due to the scaling and solidification of the liquid medium in the oil well; when the sucker rod is pulled up during the pump sticking operation in the oil well, the rated load of the sucker rod can be pulled up to detach at the safety joint or reversed to detach, depending on the working conditions. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the upper connector; Figure 3 It is a 3D diagram of the upper connector; Figure 4 This is a schematic diagram of a torque shear pin; Figure 5 This is a schematic diagram of the lower connector; Figure 6 This is a schematic diagram of a double-acting sliding sleeve; Figure 7 This is a schematic diagram of a shear snap ring.

[0014] In the diagram: 1-Upper connector, 2-Upper connector O-ring, 3-Lower connector O-ring, 4-Torque shear pin, 5-Lower connector, 6-Double-acting sleeve, 7-Shear snap ring, 11-Internal thread, 12-Slot A, 13-Slot, 14-Rectangular groove, 41-Left cylinder, 42-Right cylinder, 43-Center steel plate, 51-Round hole, 52-Four-start trapezoidal internal thread, 53-External thread, 61-Four-start trapezoidal external thread, 62-Rectangular ridge, 63-Round hole, 64-Slot B, 71-Internal groove, 72-Inner ring, 73-Outer ring. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings: Depend on Figures 1 to 7 As shown, an oilfield sucker rod safety connector includes an upper connector 1 and a lower connector 5. The upper end of the upper connector 1 is connected to the upper sucker rod via an internal thread 11, and the lower connector 5 is connected to the lower sucker rod via an external thread 53. A double-acting sleeve 6 is provided on the lower exterior of the upper connector 1. The upper connector 1 and the double-acting sleeve 6 are connected by an axial rectangular protrusion 62, preventing them from rotating relative to each other. A shear spring 7 is connected to the lower end of the upper connector 1 via a groove 13, and the shear spring 7 is located at the lower end of the double-acting sleeve 6. The lower connector 5 is connected to the outside of the double-acting sleeve 6 via threads, and a radial torque shear pin 4 is provided between the double-acting sleeve 6 and the lower connector 5.

[0016] The upper connector 1 is a stepped shaft, with a large cylinder at the top and a small cylinder at the bottom. The large cylinder has an internal thread 11, and the outer surface of the small cylinder where it connects to the large cylinder has a groove A12 for placing an O-ring seal 2, thus achieving a seal between the upper connector 1 and the double-acting sliding sleeve 6 and preventing well fluid from entering the gap between the upper connector 1 and the double-acting sliding sleeve 6 and forming scale. A groove 13 is formed on the lower outer surface of the small cylinder for placing a shear spring 7. Several axial rectangular grooves 14 are formed on the outer surface of the small cylinder, which mate with rectangular protrusions 62 on the double-acting sliding sleeve 6 to prevent axial rotation between the upper connector 1 and the double-acting sliding sleeve 6.

[0017] The upper end of the lower connector 5 is provided with a four-headed trapezoidal internal thread 52, which cooperates with the double-acting sliding sleeve 6, and the lower end is provided with an external thread 53, which is connected to the lower sucker rod.

[0018] The double-acting sleeve 6 is also a stepped shaft, with a large cylinder at the top and a small cylinder at the bottom. The small cylinder has a rectangular protrusion 62 inside that mates with the rectangular groove 14, and a four-start trapezoidal external thread 61 on its outer surface that mates with the lower connector 5. The four-start trapezoidal thread, also known as a four-thread trapezoidal thread, can improve the smoothness of the safety connector's backlash disengagement and reduce the number of backlash turns while ensuring the thread's tensile strength. A groove B64 is opened at the connection between the small cylinder and the large cylinder to place the lower connector O-ring 3, achieving a seal between it and the lower connector 5 and preventing well fluid from entering the gap between the lower connector 5 and the double-acting sleeve 6 and forming scale. A radial cylinder 63 is opened on the outer wall of the large cylinder, and the torque shear pin 4 passes through the side wall of the lower connector 5 and is located in the circular hole 63.

[0019] The torque shearing pin 4 includes a left cylinder 41 and a right cylinder 42, which are connected by a middle steel plate 43. The thickness of the middle steel plate 43 depends on the torque force required to shear the upper connector 5 and the double-acting sliding sleeve 6 when they are unhooked. When the unhooking torque reaches the preset torque, the middle steel plate 43 is sheared off.

[0020] The shear spring 7 is C-shaped, comprising an inner ring 72 and an outer ring 73. The axial height of the inner ring 72 is less than the height of the outer ring 73. The inner ring 72 is located within the groove 13 of the upper connector 1, while the outer ring is located outside the groove 13. Two inner grooves 71 are formed at the junction of the inner ring 72 and the outer ring 73, concentrating stress at these two grooves 71. When the upward load between the upper connector 1 and the double-acting sliding sleeve 6 exceeds the preset shear breakage load between the two inner grooves 71, the shear spring 7 breaks at this point.

[0021] During operation, the oilfield sucker rod safety joint is connected between the first and second sucker rods at the upper end of the pumping unit piston, between the first and second sucker rods at the upper end of the screw pump rotor, or at the actual installation location required during sucker rod string construction. When the pumping unit piston, screw pump rotor, or sucker rod body becomes stuck inside the pump barrel or tubing during downhole operations, requiring the safety joint to be disengaged, two construction methods can be adopted: First, when the sucker rod is lifted to the shearing breaking load force of the shearing spring 7, the shearing spring 7 will disengage, thus disengaging the joint; Second, after lifting the sucker rod to the point above the jamming point and then adding an additional 10KN~20KN load force, the sucker rod is rotated clockwise at the wellhead using sucker rod hydraulic tongs. When the torque reaches the shearing torque of the torque shearing pin 4, the torque shearing pin 4 will shear off, and the lower joint 5 and the double-acting sliding sleeve 6 will disengage under the clockwise torque of the sucker rod hydraulic tongs.

Claims

1. A safety connector for oilfield sucker rods, comprising an upper connector (1) and a lower connector (5), wherein the upper end of the upper connector (1) is connected to an upper sucker rod via an internal thread, and the lower connector (5) is connected to a lower sucker rod via an external thread, characterized in that: The upper connector (1) is provided with a double-acting sleeve (6) on the lower side. The lower end of the upper connector (1) is connected to a shear spring (7) through a slot (13), and the shear spring (7) is located at the lower end of the double-acting sleeve (6). The double-acting sleeve (6) is connected to the lower connector (5) through a thread, and a radial torque shear pin (4) is provided between the double-acting sleeve (6) and the lower connector (5). The outer surface of the upper connector (1) where it mates with the double-acting sliding sleeve (6) has several axial rectangular grooves (14), and the inner surface of the double-acting sliding sleeve (6) has rectangular protrusions (62) that mate with the rectangular grooves (14). The shear spring (7) is C-shaped in general, including an inner ring (72) and an outer ring (73). The axial height of the inner ring (72) is less than the height of the outer ring (73). The inner ring (72) is located in the slot (13) of the upper connector (1), and the outer ring is located outside the slot (13). There are two inner grooves (71) at the connection between the inner ring (72) and the outer ring (73).

2. The oilfield sucker rod safety joint according to claim 1, characterized in that: An upper connector O-ring (2) is provided between the upper connector (1) and the double-acting sliding sleeve (6), and a lower connector O-ring (3) is provided between the double-acting sliding sleeve (6) and the lower connector (5).

3. The oilfield sucker rod safety joint according to claim 2, characterized in that: The thread between the double-acting sleeve (6) and the lower connector (5) is a four-start trapezoidal thread.

4. The oilfield sucker rod safety joint according to claim 3, characterized in that: The double-acting sleeve (6) has a radial circular hole (63), and the torque shear pin (4) passes through the side wall of the lower connector (5) and is located in the circular hole (63).

5. The oilfield sucker rod safety joint according to claim 4, characterized in that: The torque shear pin (4) includes a left cylinder (41) and a right cylinder (42), which are connected by a central steel plate (43).

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