Ultrahigh-pressure subsurface safety valve

Abstract

The invention discloses an ultrahigh-pressure subsurface safety valve, belongs to the technical field of petroleum and natural gas well completion, and aims at solving the problem that an existing subsurface safety valve is prone to leakage under the high-pressure condition. The ultrahigh-pressure subsurface safety valve comprises an upper connector (1), a spring barrel (3) and a lower connector (4) which are sequentially connected from top to bottom, and a piston cavity (28) is formed in the side wall of the upper connector (1); a piston mechanism is connected into the piston cavity (28) in a sealing mode, a positioning sealing nut (9) is arranged in the lower end of the piston cavity (28), and when the valve plate sealing mechanism is in an open state, the piston mechanism is connected with the positioning sealing nut (9) in a metal sealing mode. When the valve plate sealing mechanism is in a closed state, the piston mechanism is in metal sealing connection with the surface of the piston cavity (28). Under the conditions of high pressure and high temperature, the metal sealing connection performance is not easy to change, the product stability is improved, and the purpose of reducing the leakage rate of the safety valve is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and natural gas well completion, in particular to an ultra-high pressure downhole safety valve. Background Art

[0002] In the field of oil and gas completion technology, downhole safety valve is a very important completion tool. Downhole safety valve is an emergency safety device for oil and gas production. When downhole operations are completed or unexpected safety accidents (such as blowouts and well kicks) occur, the safety valve is closed to avoid potential risks or accidents. In recent years, as the development of oil and gas resources has expanded to deep formations, deep wells and ultra-deep wells have grown rapidly. Generally, the deeper the well, the higher the bottom temperature and pressure.

[0003] At present, most downhole safety valves on the market have relatively low pressure ratings (generally not exceeding 10,000 psi), while safety valves with high pressure ratings often fail due to unstable performance. For example, the technical problems of high-pressure downhole safety valves on the market mainly include the following aspects: 1. The joints between the main parts of the downhole safety valve generally do not leak when subjected to low pressure, but leak from time to time under high pressure. 2. The piston structure of the downhole safety valve will leak after multiple reciprocating motions. The reason is that the machining accuracy of the piston chamber, piston and other parts is not enough, or the non-metallic sealing material is aged and deteriorated. Moreover, the moving parts will not move smoothly after multiple reciprocating motions, because friction occurs between the relatively moving parts, causing damage to the parts. 3. When the valve plate is subjected to low air pressure in a mud environment, the seal is not tight enough and leakage is prone to occur. Summary of the invention

[0004] In order to solve the problem that the above-mentioned downhole safety valve is prone to leakage under high pressure, the present invention provides an ultra-high pressure downhole safety valve, when the valve plate sealing mechanism is in an open state, the piston mechanism is connected to the positioning sealing nut by metal sealing; when the valve plate sealing mechanism is in a closed state, the piston mechanism is connected to the surface of the piston cavity by metal sealing. Under high pressure and high temperature conditions, the metal sealing connection performance is not easy to change, which improves the product stability and achieves the purpose of reducing the leakage rate of the safety valve.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A super-high pressure downhole safety valve comprises an upper joint, a spring cylinder and a lower joint which are connected in sequence from top to bottom, the spring cylinder contains a push tube and a power spring which are arranged inside and outside the spring tube, a piston cavity is arranged in the side wall of the upper joint, the upper part of the piston cavity is communicated with the outside of the upper joint, a piston mechanism is sealed in the piston cavity, the piston mechanism can move up and down, a positioning sealing nut is arranged in the lower end of the piston cavity, the positioning sealing nut is sealingly connected and fixed to the upper joint, the positioning sealing nut is sleeved outside the piston mechanism, the push tube can move up and down with the piston mechanism, the power spring can provide restoring force to the piston mechanism, and a valve plate sealing mechanism is arranged in the lower part of the spring cylinder; when the valve plate sealing mechanism is in an open state, the piston mechanism is located at the lower limit position, and the piston mechanism is connected to the positioning sealing nut in a metal sealing manner; when the valve plate sealing mechanism is in a closed state, the piston mechanism is located at the upper limit position, and the piston mechanism is connected to the surface of the piston cavity in a metal sealing manner.

[0007] The beneficial effects of the present invention are:

[0008] 1. The connection between the main parts of the safety valve adopts the form of thread + full metal seal, and the metal surface is sealed with the metal surface. Under high pressure and high temperature conditions, the performance is not easy to change, which improves the stability of the product and reduces the leakage rate of the safety valve.

[0009] 2. In addition to using non-elastic sealing materials with good sealing performance, the piston mechanism also adds metal seals to maintain stable and reliable performance under high-pressure working environments, playing a dual protection role; when the piston cavity and the piston mechanism put the downhole safety valve in a closed state, a metal seal is formed between the piston mechanism and the piston cavity, thereby improving the sealing reliability of the piston mechanism; when the length adapter mechanism puts the downhole safety valve in an open state, metal seals are simultaneously formed between the push pipe and the lower joint, as well as between the piston mechanism and the positioning sealing nut.

[0010] 3. The piston mechanism involving relative motion is made of special anti-corrosion metal materials, and the surface is treated with a special coating. This special coating treatment can effectively prevent the wear caused by the relative motion of parts and improve the stability of the product.

[0011] 4. A conical metal seal is used between the valve plate sealing mechanism and the spring tube, and a spherical metal seal + non-elastic seal is used inside the valve plate sealing mechanism, which solves the problem of easy failure of the valve plate seal of the high-pressure downhole safety valve and easy leakage when subjected to low air pressure in an environment containing impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0013] Figure 1 It is a schematic diagram of the valve plate sealing mechanism of the ultra-high pressure downhole safety valve of the present invention when it is in a closed state.

[0014] Figure 2 It is a schematic diagram of the valve plate sealing mechanism of the ultra-high pressure downhole safety valve of the present invention when it is in an open state.

[0015] Figure 3 yes Figure 1 A magnified schematic diagram of area A in the middle.

[0016] Figure 4 yes Figure 1 A magnified schematic diagram of area B in the middle.

[0017] Figure 5 is along Figure 1 Schematic diagram of the CC direction.

[0018] Figure 6 yes Figure 2 Enlarged schematic diagram of area D in the middle.

[0019] Figure 7 yes Figure 2 An enlarged schematic diagram of part E in the middle.

[0020] Figure 8 is a schematic diagram of the upper connector.

[0021] Fig. 9 is a schematic diagram of the lower connector.

[0022] Fig.10 It is a schematic diagram of positioning the sealing nut.

[0023] Fig.11 is a schematic diagram of the piston seat.

[0024] Fig.12 is a schematic diagram of the piston rod.

[0025] Fig.13 It is a schematic diagram of the push cylinder.

[0026] Fig.14 yes Figure 2 An enlarged schematic diagram of the sealing mechanism of the middle valve plate.

[0027] The following are the descriptions of the reference numerals:

[0028] 1. Upper joint; 2. Sealing ring; 3. Spring cylinder; 4. Lower joint; 5. Piston seat; 6. Sealing assembly; 7. Sealing rod; 8. Piston rod; 9. Positioning sealing nut; 10. Set screw; 11. Piston rod connector; 12. Elastic component; 13. Upper bearing ring; 14. Bearing ball; 15. Cage; 16. Lower bearing ring; 17. Scraping ring; 18. Pushing tube; 19. Power spring; 20. Extension cylinder; 21. Valve seat; 22. Valve plate pin; 23. Torsion spring; 24. Valve plate; 25. Locking section; 26. First smooth section; 27. Positioning groove; 28. Piston cavity; 29. Third annular groove; 30. Third inner sealing section; 31. Fourth inner sealing section; 32. Eighth inner sealing surface; 33. Second smooth section; 34. Fifth inner sealing surface; 35. Fourth outer sealing surface; 36. Third outer sealing surface; 37. Fifth outer sealing surface; 38. Transition section; 39. Radial vent hole; 40. First outer sealing surface; 41. Second outer sealing surface; 42. First small diameter section; 43. First medium diameter section; 44. First large diameter section; 45. Inner protruding section; 46. Second large diameter section; 47. Second small diameter section; 48. Sixth inner sealing surface; 49. Seventh inner sealing surface; 50. Seventh outer sealing surface. Detailed implementation mode

[0029] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0030] For the convenience of understanding and description, the following description of the present invention adopts absolute positional relationships. Unless otherwise specified, the orientation word "upper" represents Figure 1 the left direction in Figure 1 the right direction in Figure 1 the lower side direction in Figure 1 the upper side direction in

[0031] Please refer to Figure 1 to Figure 2As shown, the present invention provides an ultra-high pressure downhole safety valve, comprising an upper joint 1, a spring barrel 3 and a lower joint 4 connected in sequence from top to bottom, the spring barrel 3 contains a push tube 18 and a power spring 19 arranged inside and outside, a piston chamber 28 is arranged in the side wall of the upper joint 1, the upper part of the piston chamber 28 is communicated with the outside of the upper joint 1, a piston mechanism is sealed and connected in the piston chamber 28, the piston mechanism can move up and down, a positioning sealing nut 9 is arranged in the lower end of the piston chamber 28, the positioning sealing nut 9 is sealed and fixed with the upper joint 1, the positioning sealing nut 9 is sleeved outside the piston mechanism, the push tube 18 can move up and down synchronously with the piston mechanism, the power spring 19 can provide restoring force to the piston mechanism, and a valve plate sealing mechanism is arranged in the lower part of the spring barrel 3; when the valve plate sealing mechanism is in an open state, the piston mechanism is located at the lower limit position, and the piston mechanism is connected to the positioning sealing nut 9 in a metal sealing manner; when the valve plate sealing mechanism is in a closed state, the piston mechanism is located at the upper limit position, and the piston mechanism is connected to the surface of the piston chamber 28 in a metal sealing manner.

[0032] See also Figure 1 , Figure 2 , Figure 8 and Fig. 9 As shown, the axis of the upper joint 1, the axis of the spring barrel 3 and the axis of the lower joint 4 coincide with each other, the upper joint 1, the spring barrel 3 and the lower joint 4 are threadedly connected and fixed in sequence, the lower end of the upper joint 1 is sleeved in the upper end of the spring barrel 3, the upper end of the lower joint 4 is sleeved in the lower end of the spring barrel 3, a first outer sealing surface 40 is arranged outside the lower end of the upper joint 1, a first inner sealing surface is arranged inside the upper part of the spring barrel 3, the first outer sealing surface 40 is metal-sealed with the first inner sealing surface, a second outer sealing surface 41 is arranged outside the upper end of the lower joint 4, a second inner sealing surface is arranged inside the lower part of the spring barrel 3, the second outer sealing surface 41 is metal-sealed with the second inner sealing surface.

[0033] See also Figure 3 , Figure 6 , Figure 8 , Figures 10 to 12As shown, the piston mechanism comprises a piston seat 5, a sealing rod 7 and a piston rod 8 which are threadedly connected in sequence from top to bottom. The piston seat 5 and the sealing rod 7 are both sleeved with a sealing assembly 6, and the sealing assembly 6 can adopt a non-metallic sealing ring. The axis of the piston cavity 28 is parallel to the axis of the upper joint 1. The inner surface of the piston cavity 28 comprises a first small diameter section 42, a third inner sealing section 30, a first middle diameter section 43, a fourth inner sealing section 31 and a first large diameter section 44 which are arranged in sequence from top to bottom. The upper end of the piston seat 5 can be located in the first small diameter section 42. The outer surface of the piston seat 5 is provided with There is a first outer flange, a third outer sealing surface 36 is arranged outside the upper end of the first outer flange, the sealing assembly 6 is located in the first middle diameter section 43, the positioning sealing nut 9 is fixedly sleeved in the first large diameter section 44, the positioning sealing nut 9 is threadedly connected to the upper joint 1, the piston rod 8 passes through the positioning sealing nut 9, a fourth outer sealing surface 35 is arranged outside the upper end of the positioning sealing nut 9, a fifth inner sealing surface 34 is arranged inside the upper end of the positioning sealing nut 9, a second outer flange is arranged outside the upper end of the piston rod 8, and a fifth outer sealing surface 37 is arranged outside the lower end of the second outer flange.

[0034] See also Figure 3 As shown, the fourth outer sealing surface 35 of the positioning sealing nut 9 is metal-sealed and connected to the fourth inner sealing section 31 of the piston chamber 28; when the piston mechanism is located at the lower limit position, the fifth outer sealing surface 37 of the piston rod 8 is metal-sealed and connected to the fifth inner sealing surface 34 of the positioning sealing nut 9; when the piston mechanism is located at the upper limit position, the third outer sealing surface 36 of the piston seat 5 is metal-sealed and connected to the third inner sealing section 30 of the piston chamber 28.

[0035] See also Figure 4 and Figure 7 As shown, the lower end of the piston rod 8 is connected to the upper end of the push tube 18 through a length adapter mechanism. The length adapter mechanism is a cylindrical structure. The length adapter mechanism is sleeved between the push tube 18 and the spring tube 3. The length adapter mechanism contains a piston rod connector 11 and a bearing assembly connected up and down. The bearing assembly contains an upper bearing ring 13, a bearing ball 14 and a lower bearing ring 16 connected in sequence from top to bottom. A retaining frame 15 is also provided between the upper bearing ring 13 and the lower bearing ring 16. Along the axial direction of the push tube 18, the push tube 18 can move a set distance relative to the piston rod 8.

[0036] See also Figure 4 and Figure 7As shown, the piston rod connector 11 is a cylindrical structure, the piston rod 8, the piston rod connector 11 and the upper bearing ring 13 are threadedly connected and fixed in sequence, the upper end of the push tube 18 is sleeved in the upper bearing ring 13 and the lower bearing ring 16, and an annular cavity is formed between the upper end of the push tube 18 and the upper bearing ring 13, and an elastic component 12 is arranged in the annular cavity. The elastic component 12 can be a wave spring, and the wave spring adopts a matching assembly method, and has a preload in the assembled state. A third outer flange is arranged outside the upper end of the push tube 18, and the third outer flange is located in the annular cavity. The upper end of the elastic component 12 abuts against the piston rod connector 11, and the lower end of the elastic component 12 abuts against the third outer flange, and the third outer flange can abut against the lower end of the upper bearing ring 13. The function of setting the push tube of the length adaptation mechanism is that when the piston mechanism is located at the lower limit position, a metal sealing connection is formed between the push tube 18 and the lower joint 4 and between the piston rod 8 and the positioning sealing nut 9 at the same time.

[0037] See also Figure 1 and Figure 2 As shown, the inner surface of the lower part of the spring tube 3 is provided with an inner protruding section 45, which is located above the valve plate sealing mechanism. The upper end of the power spring 19 abuts against the lower bearing ring 16, and the lower end of the power spring 19 abuts against the inner protruding section 45.

[0038] See also Figure 1 , Figure 2 and Fig.13 As shown, an extension tube 20 is also sleeved in the spring tube 3, and the piston rod 8 is located between the spring tube 3 and the extension tube 20. The axis of the spring tube 3, the axis of the push tube 18 and the axis of the extension tube 20 coincide with each other. The inner surface of the push tube 18 contains a second large diameter section 46, a transition section 38 and a second small diameter section 47 which are arranged in sequence from top to bottom. The upper end of the extension tube 20 is fixedly sleeved in the upper joint 1, and a fourth outer flange is arranged outside the upper end of the extension tube 20. The upper end of the extension tube 20 is connected and fixed to the upper joint 1 by a set screw 10, and the lower end of the extension tube 20 is sleeved in the second large diameter section 46. The extension tube 20 and the push tube 18 have a clearance fit or a transition fit, and the inner diameter of the extension tube 20 is equal to the inner diameter of the second small diameter section 47. A first annular groove is arranged in the upper end of the push tube 18, and a scraper ring 17 is arranged in the first annular inner groove. The scraper ring 17 and the push tube 18 have a transition fit or an interference fit, and the scraper ring 17 can effectively prevent debris deposition. A radial vent hole 39 is provided at the lower portion of the push tube 18 , and the radial vent hole 39 is located in the second small diameter section 47 .

[0039] See also Figure 1 , Figure 2 , Figure 5 and Fig.14As shown, the valve plate sealing mechanism includes a valve seat 21, a valve plate pin 22 and a valve plate 24 connected in sequence, the valve seat 21 is a cylindrical structure, the valve seat 21 is threadedly connected and fixed to the spring tube 3, a torsion spring 23 is also connected between the valve seat 21 and the valve plate 24, a sixth inner sealing surface 48 is arranged inside the upper end of the valve seat 21, a sixth outer sealing surface is arranged outside the lower end of the inner protruding section 45, and the sixth inner sealing surface 48 is metal-sealably connected to the sixth outer sealing surface.

[0040] See also Figure 1 to Figure 2 As shown, a seventh inner sealing surface 49 is provided in the lower end of the valve seat 21, a second annular groove is provided in the seventh inner sealing surface 49, a sealing ring 2 is provided in the second annular groove, the sealing ring 2 is made of a non-metallic elastic material, the axis of the second annular groove, the axis of the sealing ring 2 and the axis of the valve seat 21 coincide, a seventh outer sealing surface 50 is provided at one end of the valve plate 24 facing the valve seat 21, and the seventh inner sealing surface 49 and the seventh outer sealing surface 50 can be connected in a metal seal. When the valve plate sealing mechanism is in a closed state, the valve seat 21 and the valve plate 24 are both sealed through the sealing ring 2, and the seventh inner sealing surface 49 and the seventh outer sealing surface 50 are also connected in a metal seal.

[0041] See also Figure 1 , Figure 2 and Figure 8 As shown, the inner surface of the axial inner flow channel of the upper joint 1 contains a locking section 25, a first smooth section 26 and a third annular groove 29 which are arranged in sequence from top to bottom. The locking section 25 contains a plurality of fourth annular grooves which are arranged at intervals along the axial direction of the upper joint 1. The inner surface of the axial inner flow channel of the upper joint 1 also contains a positioning groove 27 which is located between the first smooth section 26 and the third annular groove 29. The positioning groove 27 is arranged opposite to the piston cavity 28 on the left and right. Along the axial direction of the upper joint 1, the position of the third annular groove 29 corresponds to the position of the piston cavity 28. The wall thickness of the upper joint 1 between the third annular groove 29 and the piston cavity 28 is 3 mm-5 mm.

[0042] See also Figure 1 , Figure 2 , Figure 8 and Fig. 9 As shown, the inner surface of the axial inner flow channel of the lower joint 4 contains a second smooth section 33, an eighth inner sealing surface 32 is provided inside the upper end of the lower joint 4, and an eighth outer sealing surface is provided outside the lower end of the push tube 18. When the valve plate sealing mechanism is in an open state, the eighth outer sealing surface and the eighth inner sealing surface 32 can be connected in a metal seal. The inner diameters of the first smooth section 26, the inner diameters of the extension tube 20, and the inner diameters of the second smooth section 33 are the same, and the axial inner flow channel of the upper joint 1, the axial inner flow channel of the extension tube 20, the axial inner flow channel of the push tube 18, and the axial inner flow channel of the lower joint are connected in sequence.

[0043] The metal sealing connection means that both the inner sealing surface and the outer sealing surface are metal surfaces, and both the inner sealing surface and the outer sealing surface are in the shape of a ring. Along the axis direction of the ring, the inner diameter of one end of the ring is smaller than the inner diameter of the other end of the ring. Both the inner sealing surface and the outer sealing surface can be conical cylindrical surfaces or spherical surfaces (parts thereof), and the inner sealing surface and the outer sealing surface are matched inside and outside to form a sealing connection by relying on axial pressure.

[0044] For example, the spring cylinder 3 and the valve seat 21 are connected by threads, and both are provided with conical metal sealing surfaces. When the two threads are tightened, a seal is formed. A spherical metal sealing surface is provided between the valve seat 21 and the valve plate 24 to form a metal seal. The valve seat 21 is provided with the second annular groove, and the sealing ring 2 is installed in the second annular groove. The spherical metal sealing surfaces of the valve seat 21 and the valve plate 24 also form a non-elastic seal.

[0045] See also Figures 1 to 13 As shown, the working process of the ultra-high pressure downhole safety valve is introduced below. The ultra-high pressure downhole safety valve can be safely used in the high pressure range of 15000psi-25000psi.

[0046] Assembly status:

[0047] The power spring 19 is in a compressed state, the third outer sealing surface 36 of the piston seat 5 abuts against the third inner sealing section 30 on the rear end of the piston chamber 28 to form a metal seal, and the valve plate 24 is in a closed state under the action of the torsion spring 23, that is, the spherical metal sealing surface of the valve plate 24 and the spherical metal sealing surface of the valve seat 21 fit together to form a seal, and the seventh inner sealing surface 49 is connected to the seventh outer sealing surface 50 by metal sealing.

[0048] Opening the working principle of the downhole safety valve:

[0049] If there is a high pressure underground, it is necessary to first pressurize the central flow channel from the ground to balance the pressure difference on both sides of the valve plate, and then pressurize through the hydraulic control pipeline. The hydraulic control pipeline is sealed and connected to the upper end of the piston chamber 28, and the hydraulic oil enters the piston chamber 28 of the upper joint 1. The hydraulic pressure pushes the piston mechanism downward, and the piston mechanism pushes the length adapter mechanism downward to compress the power spring 19. At the same time, the elastic component 12 (wave spring) is compressed, driving the push tube 18 to move downward, and the push tube 18 pushes the valve plate 24 open, and the pressure of the hydraulic control pipeline is continued to increase. The lower end of the push tube 18 is positioned on the eighth inner sealing surface 32 of the lower joint 4, and the lower end of the push tube 18 is connected to the upper end of the lower joint 4 by metal sealing, and the valve plate 24 is isolated from the central flow channel. At the same time, the fifth outer sealing surface 37 of the piston rod 8 and the fifth inner sealing surface 34 of the positioning sealing nut 9 fit together to form a metal seal. At this time, the valve plate sealing mechanism (and the ultra-high pressure downhole safety valve) is in an open state, and the piston mechanism is at the lower limit position.

[0050] Working principle of closing downhole safety valve:

[0051] The ground hydraulic control pipeline is depressurized, the power spring 19 rebounds, driving the push tube 18, the length adapter mechanism and the piston mechanism upward, and the third outer sealing surface 36 of the piston seat 5 abuts against the third inner sealing section 30 on the rear end of the piston chamber 28. Under the action of the torsion spring 23, the valve plate 24 is closed. At this time, when the valve plate sealing mechanism (and the ultra-high pressure downhole safety valve) are in the closed state, the piston mechanism is at the upper limit position.

[0052] Working principle of forced opening of downhole safety valve:

[0053] When the downhole safety valve fails and needs to be forced open, a special forced opening tool is lowered, and the forced opening tool is positioned in the transition section 38 of the push tube 18 to drive the push tube 18 to move downward, so that the lower end of the push tube 18 is positioned on the eighth inner sealing surface 32 of the lower joint 4, and the valve plate 24 is opened. Then it is shaken downward, and the protrusion on the special forced opening tool lifts the extension tube 20, causing the extension tube 20 to deform, so that the length adaptation mechanism, the push tube 18 and the piston mechanism cannot move upward, and then the forced opening tool is pulled out, and the valve plate sealing mechanism (and the ultra-high pressure downhole safety valve) are in an open state. After forced opening, the downhole safety valve cannot be closed again.

[0054] Working principle of wire recovery downhole safety valve:

[0055] After the downhole safety valve is forcibly opened, a connecting tool is lowered to perform circumferential positioning through the positioning groove 27 on the upper joint 1, and the thin wall between the third annular groove 29 of the upper joint 1 and the piston cavity 28 is punctured to connect the piston cavity 28 with the central channel. Then, a wireline tool is used to lower the wire-recoverable downhole safety valve, and the wireline tool is seated on the locking section 25 of the upper joint 1. The sealing element of the wire-recoverable downhole safety valve forms a seal with the first smooth section 26 of the upper joint 1 and the second smooth section 33 of the lower joint 4. The hydraulic control pipeline can control the opening and closing of the wire-recoverable downhole safety valve.

[0056] The main invention points of the ultra-high pressure downhole safety valve are introduced below:

[0057] 1. The connection between the upper joint 1, the spring tube 3 and the lower joint 4 is in the form of thread + metal seal connection. The front end (nose end) of the external thread and the rear end of the internal thread are both provided with matching inclined surfaces of the same angle, and the cross-sectional thickness of the nose end of the external thread is relatively thin, which is more likely to produce plastic deformation when buckled, so that the metal surface and the metal surface seal bite more tightly, and the performance is not easy to change under high pressure and high temperature conditions, which improves the stability of the product and achieves the purpose of reducing the leakage rate of the safety valve.

[0058] 2. Adopting ground control and oil pipe recovery, the upper joint 1 and the lower joint 4 are connected to the oil pipe. A piston chamber 28 is provided in the side wall of the upper joint 1, and the piston rod 8 and the sealing assembly 6 slide in the piston chamber 28. The sealing assembly 6 is sleeved on the piston seat 5 and the sealing rod 7, and the outer diameter of the sealing assembly 6 is larger than the diameter of the piston chamber 28. The sealing assembly 6, the sealing rod 7 and the piston chamber 28 form a seal. During downhole operations, the valve plate is in an open state. When it is necessary to close the valve plate, the hydraulic control line pressure is released through the ground, and the piston retracts back under the action of the power spring, driving the push tube 18 to move upward. The valve plate 24 is no longer supported by the push tube 18. Under the action of the torsion spring, the valve plate 24 rotates upward and closes, forming a seal with the valve seat, which plays a role in isolating the downhole fluid and pressure. Conversely, when the valve plate 24 needs to be opened, pressure is applied to the upper end of the piston chamber 28 through the ground control pipeline, and the hydraulic control line pressure pushes the piston mechanism and the push tube 18 downward, while compressing the power spring 19, and the push tube 18 moves downward, pushing the valve plate 24 open, and continues to pressurize until the valve plate is fully opened. As long as the pressure of the control line is not released, the valve plate is always in the open state. The seal formed by the sealing rod, the sealing assembly and the piston chamber is the first main seal. All sealing systems may fail depending on the operating environment and the design of the seal. Typically, a seal between two metal components is required. In some environments, these "metal-to-metal" seals have a longer service life than elastomeric materials; however, elastomeric materials and other non-metallic, non-elastomeric materials also have unique advantages. Elastomers, polymers and metal-to-metal sealing systems have all been used in SCSSV (downhole safety valves). The upper part of the piston chamber 28 is provided with a third inner sealing section 30. When the hydraulic control line pressure is released, the piston mechanism moves upward under the action of the power spring 19, and the third outer sealing surface 36 of the piston seat 5 on the piston mechanism will eventually reach the third inner sealing section 30 to form a metal seal, so that the pressure and fluid at the upper end of the valve plate of the safety valve cannot enter the upper end cavity of the piston chamber, which serves the purpose of reducing the leakage rate of the safety valve. This is the second sealing barrier when the valve plate is closed. When the valve plate 24 needs to be opened, pressure is applied to the upper end of the piston chamber 28 through the ground control pipeline, and the hydraulic control line pressure pushes the piston mechanism downward. The downward thrust is transmitted to the piston rod connector 11, the bearing assembly, the elastic component 12 and the push tube 18 in turn, and the power spring 19 is compressed at the same time. The push tube 18 pushes the valve plate 24 open and continues to pressurize until the valve plate 24 is fully opened. When the valve plate 24 is fully opened, the fifth outer sealing surface 37 of the piston rod 8 abuts against the fifth inner sealing surface 34 of the positioning sealing nut 9 to form a metal seal, which is the second sealing barrier when the valve plate is in the open state.At the same time, due to the presence of the elastic component 12 (wave spring), under the action of the spring force, the eighth outer sealing surface at the lower end of the push tube 18 and the eighth inner sealing surface 32 at the upper end of the lower joint 4 are always sealed and connected, which can reduce the entry of dirt into the valve plate sealing surface and the spring cavity. However, in order to avoid the formation of a metal seal, a radial vent hole 39 is provided at the lower part of the push tube 18 so that a closed space will not be formed in the spring cavity.

[0059] 3. The sealing rod 7 and the piston rod 8 should be smooth and hard enough to slide in the piston cavity. The piston cavity should also be smooth enough. The smoothness of the piston cavity combined with the sealing assembly provides a better fluid barrier than a rough surface. The smoothness of the sealing rod and the piston rod also reduces friction, thereby reducing the working pressure requirement. The smoothness also allows the sealing rod and the piston rod to move the valve plate to the closed position more easily and quickly through the push tube 18. The sealing rod and the piston rod can be made of metals such as stainless steel, such as chrome alloy materials. Chromium alloy has good corrosion resistance, but the hardness is relatively low, and it is very easy to cause friction damage during relative sliding. Therefore, some special surface treatments are required. For example, xylitol coating treatment (xylan coating), that is, the surface of the sealing rod 7 and the piston rod 8 is provided with a xylitol coating. This surface coating treatment can effectively prevent wear caused by relative movement of parts and improve product stability. For the lower end of the push tube 18, the surface is nitrided and hardened, which can avoid the risk that the push tube 18 cannot open the valve plate normally due to repeated pushing of the valve plate, which may cause the front end of the push tube 18 to bend or be damaged.

[0060] 4. Other measures to improve the stability of the downhole safety valve include: a bearing assembly is installed between the upper end of the power spring 19 and the push tube 18. When installing and compressing the power spring, this bearing avoids the deformation and distortion that may be caused by transmitting excessive torque to the piston structure due to the installation and compression of the power spring.

[0061] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with technical features and technical solutions, with technical solutions and embodiments.

Claims

1. An ultra-high pressure downhole safety valve, characterized in that: The ultra-high pressure downhole safety valve comprises an upper joint (1), a spring cylinder (3) and a lower joint (4) which are connected in sequence from top to bottom. The spring cylinder (3) contains a push tube (18) and a power spring (19) which are arranged inside and outside the spring cylinder. A piston chamber (28) is arranged in the side wall of the upper joint (1). The upper part of the piston chamber (28) is communicated with the outside of the upper joint (1). A piston mechanism is sealed in the piston chamber (28). The piston mechanism can move up and down. A positioning sealing nut (9) is arranged in the lower end of the piston chamber (28). The positioning sealing nut (9) is sealed and fixed to the upper joint (1). , a positioning sealing nut (9) is sleeved outside the piston mechanism, the push tube (18) can move up and down with the piston mechanism, the power spring (19) can provide a restoring force to the piston mechanism, and a valve plate sealing mechanism is arranged in the lower part of the spring cylinder (3); when the valve plate sealing mechanism is in an open state, the piston mechanism is located at a lower limit position, and the piston mechanism is connected to the positioning sealing nut (9) by a metal seal; when the valve plate sealing mechanism is in a closed state, the piston mechanism is located at an upper limit position, and the piston mechanism is connected to the surface of the piston chamber (28) by a metal seal.

2. The ultra-high pressure downhole safety valve according to claim 1, characterized in that: The upper joint (1), the spring barrel (3) and the lower joint (4) are threadedly connected in sequence; the lower end of the upper joint (1) is sleeved in the upper end of the spring barrel (3); the upper end of the lower joint (4) is sleeved in the lower end of the spring barrel (3); a first outer sealing surface (40) is arranged outside the lower end of the upper joint (1); a first inner sealing surface is arranged inside the upper part of the spring barrel (3); the first outer sealing surface (40) is metal-sealed to the first inner sealing surface; a second outer sealing surface (41) is arranged outside the upper end of the lower joint (4); a second inner sealing surface is arranged inside the lower part of the spring barrel (3); the second outer sealing surface (41) is metal-sealed to the second inner sealing surface.

3. The ultra-high pressure downhole safety valve according to claim 1, characterized in that: The piston mechanism comprises a piston seat (5), a sealing rod (7) and a piston rod (8) which are connected in sequence from top to bottom. The piston seat (5) and the sealing rod (7) are both sleeved with a sealing assembly (6). The inner surface of the piston cavity (28) comprises a first small diameter section (42), a third inner sealing section (30), a first middle diameter section (43), a fourth inner sealing section (31) and a first large diameter section (44) which are arranged in sequence from top to bottom. The outer surface of the piston seat (5) is provided with a first outer flange, and the upper end of the first outer flange is provided with a A third outer sealing surface (36), the sealing assembly (6) is located in the first middle diameter section (43), the positioning sealing nut (9) is fixedly sleeved in the first large diameter section (44), the piston rod (8) passes through the positioning sealing nut (9), a fourth outer sealing surface (35) is arranged outside the upper end of the positioning sealing nut (9), a fifth inner sealing surface (34) is arranged inside the upper end of the positioning sealing nut (9), a second outer flange is arranged outside the upper end of the piston rod (8), and a fifth outer sealing surface (37) is arranged outside the lower end of the second outer flange.

4. The ultra-high pressure downhole safety valve according to claim 3, characterized in that: The fourth outer sealing surface (35) of the positioning sealing nut (9) is connected to the fourth inner sealing section (31) of the piston chamber (28) by metal sealing. When the piston mechanism is located at the lower limit position, the fifth outer sealing surface (37) of the piston rod (8) is connected to the fifth inner sealing surface (34) of the positioning sealing nut (9) by metal sealing. When the piston mechanism is located at the upper limit position, the third outer sealing surface (36) of the piston seat (5) is connected to the third inner sealing section (30) of the piston chamber (28) by metal sealing.

5. The ultra-high pressure downhole safety valve according to claim 3, characterized in that: The lower end of the piston rod (8) is connected to the upper end of the push tube (18) through a length adaptation mechanism. The length adaptation mechanism is a cylindrical structure. The length adaptation mechanism is sleeved between the push tube (18) and the spring tube (3). The length adaptation mechanism includes a piston rod connector (11) and a bearing assembly connected up and down. The bearing assembly includes an upper bearing ring (13), a bearing ball (14) and a lower bearing ring (16) connected in sequence from top to bottom. Along the axial direction of the push tube (18), the push tube (18) can move a set distance relative to the piston rod (8).

6. The ultra-high pressure downhole safety valve according to claim 5, characterized in that: The piston rod connector (11) is of a cylindrical structure. The piston rod (8), the piston rod connector (11) and the upper bearing ring (13) are connected and fixed in sequence. The upper end of the push tube (18) is sleeved in the upper bearing ring (13) and the lower bearing ring (16). An annular cavity is formed between the upper end of the push tube (18) and the upper bearing ring (13). An elastic component (12) is arranged in the annular cavity. A third outer flange is arranged outside the upper end of the push tube (18). The third outer flange is located in the annular cavity. The upper end of the elastic component (12) abuts against the piston rod connector (11), and the lower end of the elastic component (12) abuts against the third outer flange. The third outer flange can abut against the lower end of the upper bearing ring (13).

7. The ultra-high pressure downhole safety valve according to claim 5, characterized in that: An inner protruding section (45) is provided on the inner surface of the lower part of the spring tube (3), and the inner protruding section (45) is located above the valve plate sealing mechanism. The upper end of the power spring (19) abuts against the lower bearing ring (16), and the lower end of the power spring (19) abuts against the inner protruding section (45).

8. The ultra-high pressure downhole safety valve according to claim 5, characterized in that: An extension tube (20) is also sleeved in the spring tube (3), and the piston rod (8) is located between the spring tube (3) and the extension tube (20). The inner surface of the push tube (18) includes a second large diameter section (46), a transition section (38) and a second small diameter section (47) arranged in sequence from top to bottom. The upper end of the extension tube (20) is fixedly sleeved in the upper joint (1), and the lower end of the extension tube (20) is sleeved in the second large diameter section (46). The extension tube (20) and the push tube (18) are clearance-fitted or transition-fitted. The inner diameter of the extension tube (20) is equal to the inner diameter of the second small diameter section (47). A first annular groove is arranged in the upper end of the push tube (18), and a scraper ring (17) is arranged in the first annular inner groove.

9. The ultra-high pressure downhole safety valve according to claim 7, characterized in that: The valve plate sealing mechanism comprises a valve seat (21), a valve plate pin (22) and a valve plate (24) which are connected in sequence; the valve seat (21) is connected and fixed to a spring tube (3); a torsion spring (23) is also connected between the valve seat (21) and the valve plate (24); a sixth inner sealing surface (48) is arranged inside the upper end of the valve seat (21); a sixth outer sealing surface is arranged outside the lower end of the inner protruding section (45); and the sixth inner sealing surface (48) is connected to the sixth outer sealing surface in a metal sealing manner.

10. The ultra-high pressure downhole safety valve according to claim 1, characterized in that: The valve plate sealing mechanism comprises a valve seat (21), a valve plate pin (22) and a valve plate (24) which are connected in sequence, the valve seat (21) is connected and fixed to a spring tube (3), a torsion spring (23) is also connected between the valve seat (21) and the valve plate (24), a seventh inner sealing surface (49) is provided at the lower end of the valve seat (21), a second annular groove is provided in the seventh inner sealing surface (49), a sealing ring (2) is provided in the second annular groove, a seventh outer sealing surface (50) is provided at one end of the valve plate (24) facing the valve seat (21), and the seventh inner sealing surface (49) and the seventh outer sealing surface (50) can be connected in a metal seal.

11. The ultra-high pressure downhole safety valve according to claim 1, characterized in that: The inner surface of the axial inner flow channel of the upper joint (1) comprises a locking section (25), a first smooth section (26) and a third annular groove (29) which are arranged in sequence from top to bottom. The locking section (25) comprises a plurality of fourth annular grooves. The inner surface of the axial inner flow channel of the upper joint (1) further comprises a positioning groove (27). The positioning groove (27) is located between the first smooth section (26) and the third annular groove (29). The positioning groove (27) and the piston cavity (28) are arranged opposite to each other on the left and right. Along the axial direction of the upper joint (1), the position of the third annular groove (29) corresponds to the position of the piston cavity (28). The wall thickness of the upper joint (1) between the third annular groove (29) and the piston cavity (28) is 3 mm to 5 mm.

12. The ultra-high pressure downhole safety valve according to claim 1, characterized in that: The inner surface of the axial inner flow channel of the lower joint (4) includes a second smooth section (33), an eighth inner sealing surface (32) is provided inside the upper end of the lower joint (4), and an eighth outer sealing surface is provided outside the lower end of the push tube (18), and when the valve plate sealing mechanism is in an open state, the eighth outer sealing surface and the eighth inner sealing surface (32) can be connected in a metal seal.

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