Basic flush type coupling-free gas seal oil sleeve joint assembly

Abstract

The invention relates to the technical field of threaded connection of oil casings, in particular to a basically flush type coupling-free air-tight seal oil casing joint assembly which comprises an external thread joint and an internal thread joint, and after the external thread joint and the internal thread joint are screwed together, the external thread joint and the internal thread joint are screwed together. An outer metal sealing structure, an outer elastic sealing structure, meshing threads, an inner elastic sealing structure, an inner metal sealing structure, a torque shoulder and the like are sequentially formed. Through the cooperation of the external thread connector, the internal thread connector, the external metal sealing structure, the external elastic sealing structure, the meshing thread and the internal metal sealing structure, the connecting and sealing functions are provided, the connector is basically flush with the pipe body, the oil casing can enter a well easily, the well cementation gap is large, and the connector connecting efficiency can reach 65%-70%; and 2) the inner and outer seals are both metal / metal seal and elastic seal, and the double-seal structure greatly improves the sealing effect, and is suitable for ultra-deep wells and high-pressure natural gas wells with harsh conditions.

Description

Technical Field

[0001] This invention relates to the field of oil casing threaded connection technology, specifically to a basic flush type coupling-free gas-tight oil casing joint assembly. Background Technology

[0002] The casing and tubing are connected by threaded joints to form a casing string, which is mainly used for the extraction of oil and natural gas. The casing and tubing joints generally use couplings. Because the outer diameter of the coupling is significantly larger than that of the tubing, it often causes technical problems such as difficulty in running the casing and tubing and poor cementing quality.

[0003] To address this, many tubing and casing manufacturers have developed coupling-less joints, characterized by the absence of couplings and the direct machining of internal and external threads onto both ends of the pipe. Due to their smaller outer diameter, coupling-less joints can effectively improve downhole speed and cementing clearance, and have gained widespread use in recent years.

[0004] Couplingless joints are divided into two categories: one is the flush type, where the joint is exactly the same as the inner and outer diameter of the pipe. This type of joint can provide the maximum cementing clearance, but the disadvantage is that the joint connection strength is only 50-55% of that of the pipe body; the other is the thickened type, where the pipe end is first thickened on the inside and outside, and then the thickened part is machined with threads. This type of joint increases the connection strength to 70-100% of that of the pipe body, but the disadvantage is that it sacrifices the cementing clearance and increases the cost of thickening. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of this device by proposing a basic flush type coupling-free gas-tight oil sleeve joint assembly.

[0006] To achieve the above objectives, the present invention provides the following technical solution: Design a basic flush type couplingless gas-tight oil casing joint assembly, including an external threaded joint and an internal threaded joint, which are symmetrical about the axis. After the external threaded joint and the internal threaded joint are screwed together, they sequentially form an external metal sealing structure, an external elastic sealing structure, a meshing thread, an internal elastic sealing structure, an internal metal sealing structure, and a torque shoulder.

[0007] Preferably, the flaring length of the pipe end at the internal threaded joint is 100±10mm, the transition bevel angle after flaring is 7±1°, and the outer diameter increase is (0.01~0.02)D, where D is the outer diameter of the pipe.

[0008] Preferably, the large end of the external threaded connector is provided with a right-angled outer shoulder, an outer cylindrical surface, an outer sealing cone surface, and a transition outer cylindrical surface; the large end of the internal threaded connector is provided with an end face, an outer cylindrical hole, an outer sealing cone hole, and a transition outer cylindrical hole.

[0009] Preferably, the right-angled outer shoulder does not contact the end face, and the gap between them is δ1 = 0.5~0.8mm; the outer cylindrical surface does not contact the outer cylindrical hole, and the gap between them is δ2 = 0.2~0.5mm; the transition outer cylindrical surface does not contact the transition outer cylindrical hole, and the gap between them is δ3 = δ2 = 0.2~0.5mm; the outer sealing conical surface and the outer sealing conical hole form an outer metal sealing structure, the interference between them is 0.28~0.88mm, and the taper of both is 1:5.

[0010] Preferably, an outer sealing groove is machined on the transition outer cylindrical hole. The outer sealing groove is about 5mm wide and about 3mm deep. A first Teflon sealing ring with a rectangular cross section is placed in the sealing groove to form an outer elastic sealing structure.

[0011] Preferably, the meshing thread includes an external thread and an internal thread, both with a pitch A = 5.08 mm. The internal and external threads are tapered pipe threads with a taper of 1:16 to 1:10. The external and internal threads are sawtooth-shaped, with a bearing surface angle α1 = 3° and a guide surface angle α2 = 20°.

[0012] Preferably, after the external thread and the internal thread are engaged, there is a gap δ4 = 0.15~0.25mm between the tooth tip of the external thread and the tooth root of the internal thread; there is a gap δ5 = 0.15~0.25mm between the guide surfaces of the external thread and the internal thread, and the tooth tips of the external thread and the internal thread are parallel to the generatrix.

[0013] Preferably, the small end of the external threaded connector is provided with a small end transition cylindrical surface, an inner sealing conical surface, a small end cylindrical surface, and a right-angle inner end face; the small end of the internal threaded connector is provided with a small end transition cylindrical hole, an inner sealing conical hole, a small end cylindrical hole, and a right-angle inner shoulder.

[0014] Preferably, an inner sealing groove is machined on the small end transition cylindrical hole. The inner sealing groove is about 5mm wide and about 3mm deep. A second Teflon sealing ring with a rectangular cross section is placed in the sealing groove to form an inner elastic sealing structure. The inner sealing conical surface and the inner sealing conical hole form an inner metal sealing structure. The interference between the two is 0.28 to 0.88mm, and the taper of both is 1:8. The right-angled inner end face and the right-angled inner shoulder are axially interference-fitted to form a torque shoulder, which serves as an upper locking and positioning function.

[0015] Preferably, the small-end transition cylindrical surface and the small-end transition cylindrical hole do not contact each other, and the gap between them is δ6 = 0.15~0.25mm; the small-end cylindrical surface and the small-end cylindrical hole do not contact each other, and the gap between them is δ7 = 0.15~0.25mm.

[0016] The present invention proposes a basic flush-type coupling-free gas-tight oil casing joint assembly, which has the following advantages: Through the cooperation of the external threaded joint, internal threaded joint, external metal sealing structure, external elastic sealing structure, meshing thread, and internal metal sealing structure, the internal elastic sealing structure and threaded joint are machined on the end of the steel pipe without upsetting, while the internal threaded joint is machined on the end of the steel pipe after slight flaring. In use, the external threaded joint is screwed into the internal threaded joint with a certain torque to form a whole, providing connection and sealing functions. The joint is basically flush with the pipe body, making it easy to insert the oil casing into the well and allowing for a large cementing clearance; the joint connection efficiency can reach 65-70%. 2) Both the internal and external seals are metal / metal seals + elastic seals, and the double sealing structure greatly improves the sealing effect. It is suitable for use in harsh conditions in ultra-deep wells and high-pressure natural gas wells. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure of this invention; Figure 2 A partial enlarged view of the external sealing structure of this invention; Figure 3 Enlarged view of the threaded fit of this invention; Figure 4 A partially enlarged view of the internal sealing structure and torque shoulder of this invention.

[0018] In the diagram: 1. External threaded connector, 2. Internal threaded connector, 3. External metal seal structure, 4. External elastic seal structure, 5. Engaging thread, 6. Internal elastic seal structure, 7. Internal metal seal structure, 8. Torque shoulder, 9. Axis, 10. Pipe end flare length, 11. Transition bevel angle after flare, 12. Outer diameter increase, 13a. Right-angle external shoulder, 13b. End face, 14a. External cylindrical surface, 14b. External cylindrical hole, 3a. External sealing conical surface, 3b. External sealing conical hole, 4 a. First Teflon sealing ring; 4b. Outer sealing groove; 15a. Transition outer cylindrical surface; 15b. Transition outer cylindrical hole; 5a. External thread; 5b. Internal thread; 16. Thread generatrix; 6a. Second Teflon sealing ring; 6b. Inner sealing groove; 7a. Inner sealing conical surface; 7b. Inner sealing conical hole; 8a. Right-angle inner end face; 8b. Right-angle inner shoulder; 17a. Small end transition cylindrical surface; 17b. Small end transition cylindrical hole; 18a. Small end cylindrical surface; 18b. Small end cylindrical hole. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings: See attached document Figure 1-4In this embodiment, a basic flush-type couplingless gas-tight oil casing joint assembly includes an external threaded joint 1 and an internal threaded joint 2, which are symmetrical about axis 9. The external threaded joint is machined on the end of the steel pipe without upsetting, while the internal threaded joint is machined on the end of the steel pipe after slight flaring. In use, the external threaded joint is screwed into the internal threaded joint with a certain torque to form a whole, providing connection and sealing functions. After the external threaded joint 1 and the internal threaded joint 2 are screwed together, they sequentially form an external metal sealing structure 3, an external elastic sealing structure 4, an engaging thread 5, an internal elastic sealing structure 6, an internal metal sealing structure 7, and a torque shoulder 8.

[0020] To improve connection efficiency, the internal threaded connector requires a slight flaring of the pipe end. The flaring length 10 is 100±10mm, the transition bevel angle 11 after flaring is 7±1°, and the outer diameter increase 12 is 0.01~0.02D, where D is the outer diameter of the pipe.

[0021] The large end of the external threaded connector 1 is provided with a right-angled outer shoulder 13a, an outer cylindrical surface 14a, an outer sealing cone surface 3a, and a transition outer cylindrical surface 15a; the large end of the internal threaded connector 2 is provided with an end face 13b, an outer cylindrical hole 14b, an outer sealing cone hole 3b, and a transition outer cylindrical hole 15b.

[0022] The aforementioned right-angle outer shoulder 13a does not contact the end face 13b, and the gap between them is δ1 = 0.5–0.8 mm; the outer cylindrical surface 14a does not contact the outer cylindrical hole 14b, and the gap between them is δ2 = 0.2–0.5 mm; the transition outer cylindrical surface 15a does not contact the transition outer cylindrical hole 15b, and the gap between them is δ3 = δ2 = 0.2–0.5 mm. Setting these positions as clearance fits aims to improve the sealing effect of the joint's outer metal sealing structure 3 and outer elastic sealing structure 4.

[0023] The outer sealing conical surface 3a and the outer sealing conical hole 3b form the outer metal sealing structure 3, which plays the main sealing role. The interference between the two is 0.28 to 0.88 mm, and the taper of both is 1:5.

[0024] An outer sealing groove 4b is machined on 15b. The outer sealing groove 4b is about 5mm wide and about 3mm deep. A first Teflon sealing ring 4a with a rectangular cross section is placed in the sealing groove to form an outer elastic sealing structure 4, which plays an auxiliary sealing role.

[0025] In this way, the outer seal consists of a dual structure of outer elastic sealing structure 4 and outer metal sealing structure 3, which improves the sealing reliability of the joint.

[0026] The meshing thread 5 includes an external thread 5a and an internal thread 5b, which serve as a connection. The pitch of both threads is A=5.08mm. The internal and external threads are tapered pipe threads with a taper of 1:16 to 1:10.

[0027] The external thread 5a and the internal thread 5b are sawtooth-shaped, with a bearing surface angle α1=3° and a guide surface angle α2=20°. This type of threaded connection has high efficiency and good bending resistance.

[0028] After the external thread 5a and the internal thread 5b engage, there is a gap δ4 = 0.15–0.25 mm between the tooth crest of the external thread 5a and the tooth root of the internal thread 5b; there is also a gap δ5 = 0.15–0.25 mm between the guide surfaces of the external thread 5a and the internal thread 5b. These gaps are designed to store thread grease and improve the joint's anti-sticking ability.

[0029] The tooth tips of the external thread 5a and the internal thread 5b are parallel to the generatrix 16. This type of threaded connection is highly efficient and easy to machine and inspect. The small end of the external threaded connector 1 is provided with a small end transition cylindrical surface 17a, an inner sealing conical surface 7a, a small end cylindrical surface 18a, and a right-angle inner end surface 8a; the small end of the internal threaded connector 2 is provided with a small end transition cylindrical hole 17b, an inner sealing conical hole 7b, a small end cylindrical hole 18b, and a right-angle inner shoulder 8b.

[0030] An inner sealing groove 6b is machined on the small end transition cylindrical hole 17b. The inner sealing groove 6b is about 5mm wide and about 3mm deep. A second Teflon sealing ring 6a with a rectangular cross section is placed in the sealing groove to form an inner elastic sealing structure 6.

[0031] The inner sealing conical surface 7a and the inner sealing conical hole 7b form the inner metal sealing structure 7. The interference between the two is 0.28 to 0.88 mm, and the taper of both is 1:8.

[0032] The small-end transition cylindrical surface 17a and the small-end transition cylindrical hole 17b do not contact each other, and the gap between them is δ6 = 0.15~0.25mm; the small-end cylindrical surface 18a and the small-end cylindrical hole 18b do not contact each other, and the gap between them is δ7 = 0.15~0.25mm. Setting these positions as clearance fits aims to improve the sealing effect of the internal metal sealing structure 7 and the internal elastic sealing structure 6 of the joint.

[0033] In this way, the internal seal consists of a dual structure of internal elastic sealing structure 6 and internal metal sealing structure 7, which improves the sealing reliability of the joint.

[0034] The right-angled inner end face 8a and the right-angled inner shoulder 8b are axially interference-fitted to form a torque shoulder 8, which serves as an upper locking and positioning element.

[0035] Working principle: External threaded connector 1 and internal threaded connector 2 are symmetrical about axis 9. The external threaded connector is machined on the end of the steel pipe without upsetting, while the internal threaded connector is machined on the end of the steel pipe after slight flaring. In use, the external threaded connector is screwed into the internal threaded connector with a certain torque to form a whole, providing connection and sealing functions. After the external threaded connector 1 and the internal threaded connector 2 are screwed together, they sequentially form an external metal sealing structure 3, an external elastic sealing structure 4, an engaging thread 5, an internal elastic sealing structure 6, an internal metal sealing structure 7, and a torque shoulder 8. To improve connection efficiency, the internal threaded connector requires slight flaring at the pipe end.

[0036] The right-angle outer shoulder 13a does not contact the end face 13b, and the gap between them is δ1 = 0.5~0.8mm; the outer cylindrical surface 14a does not contact the outer cylindrical hole 14b, and the gap between them is δ2 = 0.2~0.5mm; the transition outer cylindrical surface 15a does not contact the transition outer cylindrical hole 15b, and the gap between them is δ3 = δ2 = 0.2~0.5mm. Setting these positions as clearance fits aims to improve the sealing effect of the joint's outer metal sealing structure 3 and outer elastic sealing structure 4.

[0037] The outer sealing conical surface 3a and the outer sealing conical hole 3b form the outer metal sealing structure 3, which plays the main sealing role. The interference between the two is 0.28 to 0.88 mm, and the taper of both is 1:5. An outer sealing groove 4b is machined on the transition outer cylindrical hole 15b. The outer sealing groove 4b is about 5 mm wide and about 3 mm deep. A rectangular cross-section first Teflon sealing ring 4a is placed in the sealing groove to form an outer elastic sealing structure 4, which plays the auxiliary sealing role.

[0038] In this way, the outer seal consists of a dual structure of outer elastic sealing structure 4 and outer metal sealing structure 3, which improves the sealing reliability of the joint.

[0039] After the external thread 5a and the internal thread 5b engage, there is a gap δ4 = 0.15–0.25 mm between the tooth crest of the external thread 5a and the tooth root of the internal thread 5b; there is also a gap δ5 = 0.15–0.25 mm between the guide surfaces of the external thread 5a and the internal thread 5b. These gaps are designed to store thread grease and improve the joint's anti-sticking ability.

[0040] An inner sealing groove 6b is machined on the small end transition cylindrical hole 17b. The inner sealing groove 6b is about 5mm wide and about 3mm deep. A second Teflon sealing ring 6a with a rectangular cross section is placed in the sealing groove to form an inner elastic sealing structure 6. The inner sealing conical surface 7a and the inner sealing conical hole 7b form an inner metal sealing structure 7. The interference between the two is 0.28~0.88mm, and the taper of both is 1:8.

[0041] The small-end transition cylindrical surface 17a and the small-end transition cylindrical hole 17b do not contact each other, and the gap between them is δ6 = 0.15~0.25mm; the small-end cylindrical surface 18a and the small-end cylindrical hole 18b do not contact each other, and the gap between them is δ7 = 0.15~0.25mm. Setting these positions as clearance fits aims to improve the sealing effect of the internal metal sealing structure 7 and the internal elastic sealing structure 6 of the joint.

[0042] In this way, the inner seal consists of a dual structure of inner elastic sealing structure 6 and inner metal sealing structure 7, which improves the sealing reliability of the joint. The right-angle inner end face 8a and the right-angle inner shoulder 8b are axially interference-fitted to form a torque shoulder 8, which plays the role of upper buckling and positioning.

[0043] This invention is simple and convenient to process, and can provide the most convenient downhole speed and the largest cementing clearance. At the same time, the joint has high connection strength and safe and reliable gas sealing performance, making it suitable for use in ultra-deep wells and high-pressure natural gas wells.

[0044] Although the present invention has been illustrated and described with reference to preferred embodiments, those skilled in the art will understand that various changes in form and detail are possible within the scope of the claims.

Claims

1. A basic flush-type couplingless gas-tight oil casing joint assembly, comprising an external threaded joint (1) and an internal threaded joint (2), which are symmetrical about an axis (9). Its characteristics are: After the external threaded connector (1) and the internal threaded connector (2) are screwed together, an external metal sealing structure (3), an external elastic sealing structure (4), a meshing thread (5), an internal elastic sealing structure (6), an internal metal sealing structure (7), and a torque shoulder (8) are formed in sequence.

2. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: The length (10) of the flared end of the pipe at the internal threaded connector (2) is 100±10mm, the transition slope angle (11) after flaring is 7±1°, and the increase in outer diameter (12) is (0.01~0.02)D, where D is the outer diameter of the pipe.

3. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: The large end of the external threaded connector (1) is provided with a right-angled outer shoulder (13a), an outer cylindrical surface (14a), an outer sealing cone surface (3a), and a transition outer cylindrical surface (15a). The large end of the internal threaded connector (2) is provided with an end face (13b), an outer cylindrical hole (14b), an outer sealing cone hole (3b), and a transition outer cylindrical hole (15b).

4. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 3, characterized in that: The right-angle outer shoulder (13a) does not contact the end face (13b), and the gap between them is δ1=0.5~0.8mm. The outer cylindrical surface (14a) does not contact the outer cylindrical hole (14b), and the gap between them is δ2=0.2~0.5mm. The transition outer cylindrical surface (15a) does not contact the transition outer cylindrical hole (15b), and the gap between them is δ3=δ2=0.2~0.5mm. The outer sealing conical surface (3a) and the outer sealing conical hole (3b) form an outer metal sealing structure (3), and the interference between them is 0.28~0.88mm. The taper of both is 1:

5.

5. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 4, characterized in that: An outer sealing groove (4b) is machined on the transition outer cylindrical hole (15b). The outer sealing groove (4b) is about 5mm wide and about 3mm deep. A first Teflon sealing ring (4a) with a rectangular cross section is placed in the sealing groove to form an outer elastic sealing structure (4).

6. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: The meshing thread (5) includes an external thread (5a) and an internal thread (5b), with a pitch A = 5.08 mm. The internal and external threads are tapered pipe threads with a taper of 1:16 to 1:

10. The external thread (5a) and the internal thread (5b) are sawtooth-shaped, with a bearing surface angle α1 = 3° and a guide surface angle α2 = 20°.

7. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: After the external thread (5a) and the internal thread (5b) are engaged, there is a gap δ4 = 0.15 to 0.25 mm between the tooth tip of the external thread (5a) and the tooth root of the internal thread (5b); there is a gap δ5 = 0.15 to 0.25 mm between the guide surfaces of the external thread (5a) and the internal thread (5b); and the tooth tips of the external thread (5a) and the internal thread (5b) are parallel to the generatrix (16).

8. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: The small end of the external threaded connector (1) is provided with a small end transition cylindrical surface (17a), an inner sealing conical surface (7a), a small end cylindrical surface (18a), and a right-angle inner end surface (8a). The small end of the internal threaded connector (2) is provided with a small end transition cylindrical hole (17b), an inner sealing conical hole (7b), a small end cylindrical hole (18b), and a right-angle inner shoulder (8b).

9. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 8, characterized in that: An inner sealing groove (6b) is machined on the small end transition cylindrical hole (17b). The inner sealing groove (6b) is about 5mm wide and about 3mm deep. A rectangular cross-section second Teflon sealing ring (6a) is placed in the sealing groove to form an inner elastic sealing structure (6). The inner sealing conical surface (7a) and the inner sealing conical hole (7b) form an inner metal sealing structure (7). The interference between the two is 0.28~0.88mm, and the taper of both is 1:

8. The right-angle inner end face (8a) and the right-angle inner shoulder (8b) are axially interference fitted to form a torque shoulder (8) which plays the role of upper buckling and positioning.

10. The basic flush-type couplingless gas-tight oil sleeve joint assembly according to claim 1, characterized in that: The small-end transition cylindrical surface (17a) does not contact the small-end transition cylindrical hole (17b), and the gap between them is δ6 = 0.15~0.25mm. The small-end cylindrical surface (18a) does not contact the small-end cylindrical hole (18b), and the gap between them is δ7 = 0.15~0.25mm.

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