Offshore oilfield sand washing process pipe column and using method thereof

Abstract

The invention discloses an offshore oilfield sand washing process pipe column and a using method thereof. The offshore oilfield sand washing process pipe column comprises a liquid flow reverser, a safety connector, a centralizing packer assembly, a double-wall drill rod and a sand washing assembly which are sequentially connected from top to bottom. Inner annuluses of the liquid flow reverser, the safety connector, the centralizing and packing assembly, the double-wall drill rod and the sand washing assembly are communicated with one another and form a sand washing flow channel allowing sand washing liquid to flow through, and inner cavities of the liquid flow reverser, the safety connector, the centralizing and packing assembly, the double-wall drill rod and the sand washing assembly are communicated with one another and form a flow-back channel allowing sand-carrying liquid to flow through. A liquid inlet hole is formed in the liquid flow reverser, a sand washing hole and a bypass pipe are arranged on the sand washing assembly, the liquid inlet hole and the sand washing hole are communicated with the sand washing flow channel, and the bypass pipe is communicated with the flow-back channel. A sand washing circulation channel can be self-built, sand washing fluid leakage of the low-pressure leakage well is reduced, and the sand washing operation effect can be improved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development technology, specifically relating to a sand flushing process tubing for offshore oil fields and its usage method. Background Technology

[0002] Currently, marine oil and gas resources are not only abundant, but modern science and technology have also given us the enormous capacity to develop them. The marine oil and gas industry has developed into a leading emerging industry with high output value in the marine economy.

[0003] Offshore oilfields are mostly composed of loose sandstone reservoirs. With oilfield exploitation, reservoir pressure depletion leading to severe sand production in wells has become a major cause of low production and inefficiency. Currently, during well workover and sand flushing, conventional water-based fluid flushing operations for low-pressure lost circulation wells and horizontal wells suffer from drawbacks such as severe leakage, difficulty in establishing circulation, weak sand-carrying capacity, and difficulty in bringing formation sand back to the surface. Some large lost circulation wells typically use temporary plugging agents followed by sand flushing, but this still suffers from low success rates, difficulty in fully circulating formation sand, formation contamination by the plugging agent, and incompatibility with other agents. The sand flushing problem in low-pressure lost circulation wells and large lost circulation wells remains unresolved. Summary of the Invention

[0004] In order to solve all or part of the above problems, the purpose of this invention is to provide a sand flushing process string for offshore oilfields and its usage method, which can build its own sand flushing circulation channel, reduce the loss of sand flushing fluid in low-pressure lost circulation wells, meet the sand flushing operation requirements of offshore low-pressure lost circulation wells and large lost circulation wells, and improve the sand flushing operation effect.

[0005] In a first aspect, the present invention provides a sand flushing process string for offshore oilfields, comprising, from top to bottom, a fluid flow diverter, a safety joint, a centralizing and packer assembly, a double-wall drill pipe, and a sand flushing assembly. The internal annulus of the fluid flow diverter, safety joint, centralizing and packer assembly, double-wall drill pipe, and sand flushing assembly are interconnected to form a sand flushing channel through which the sand flushing fluid flows. The internal cavities of the fluid flow diverter, safety joint, centralizing and packer assembly, double-wall drill pipe, and sand flushing assembly are interconnected to form a return flow channel through which the sand-carrying fluid flows. The fluid flow diverter is provided with a fluid inlet, and the sand flushing assembly is provided with a sand flushing hole and a bypass pipe. The fluid inlet and the sand flushing hole are respectively connected to the sand flushing channel, and the bypass pipe is connected to the return flow channel.

[0006] Optionally, the centralizing and packing assembly includes a first centralizer, a packer, and a second centralizer connected sequentially from top to bottom. The top of the first centralizer is connected to the safety joint, and the bottom of the second centralizer is connected to the double-wall drill pipe.

[0007] Optionally, the fluid flow reversing device, safety joint, first stabilizer, packer, second stabilizer, double-wall drill pipe, and sand flushing assembly each include a coaxially arranged body assembly and a flow channel inner tube. The bottom of the flow channel inner tube of the fluid flow reversing device, safety joint, first stabilizer, packer, second stabilizer, and double-wall drill pipe is provided with a female plug, and the top of the flow channel inner tube of the safety joint, first stabilizer, packer, second stabilizer, double-wall drill pipe, and sand flushing assembly is provided with a male plug, and the male plug is tightly inserted and matched with the corresponding female plug. The liquid inlet is disposed on the main body assembly of the flow converter. The top of the inner tube of the flow converter is provided with an upper connector, which is connected to the main body assembly of the flow converter. The sand flushing hole and the bypass pipe are respectively disposed on the main body assembly of the sand flushing assembly. The bottom of the inner tube of the flow converter is provided with a lower connector, which is connected to the main body assembly of the sand flushing assembly.

[0008] Optionally, a first limiting ring is provided in the main body assembly of the fluid flow reversing device, and the first limiting ring is used to prevent the upper connector from moving upward. A second limiting ring is provided in the main body assembly of the safety connector, the first stabilizer, the packer, the second stabilizer, the double-wall drill pipe and the sand flushing assembly, and the second limiting ring is used to prevent the corresponding male plug from moving upward.

[0009] Optionally, each of the male plugs is provided with a centralizing rotor, and the safety connector, the first centralizer, the packer, the second centralizer, the double-wall drill pipe, and the main body assembly of the sand flushing assembly are respectively provided with centralizing grooves for the corresponding centralizing rotors to be tightly engaged.

[0010] Optionally, each of the male plugs is provided with a sealing ring, and the sealing ring can seal with the corresponding female plug.

[0011] Optionally, the safety connector body assembly includes an upper outer tube and a lower outer tube, the upper outer tube and the lower outer tube being inserted into each other, and the upper outer tube and the lower outer tube being connected by a shear pin.

[0012] Optionally, the main body assembly of the sand-washing assembly includes a sand-washing outer tube and a sand-washing head, the lower connector is connected between the sand-washing outer tube and the sand-washing head, and the sand-washing hole is located at the bottom of the sand-washing head.

[0013] Optionally, the inner tube of the sand flushing assembly includes a supporting inner tube, a central tube, an adjusting cylinder, a diffuser, a throat, a sand suction nozzle assembly, a sand flushing nozzle assembly, and a flow divider. The adjusting cylinder, diffuser, and throat are arranged sequentially from top to bottom inside the central tube. The top of the supporting inner tube is connected to the male plug of the sand flushing assembly, and the bottom is connected to the central tube. The supporting inner tube presses and fixes the adjusting cylinder, diffuser, and throat inside the central tube. The sand suction nozzle assembly is disposed inside the central tube and is located below the throat tube. The top of the diverter tube is connected to the central tube and the bottom is connected to the lower connector. The diverter tube presses and fixes the sand suction nozzle assembly inside the central tube. The sand flushing nozzle assembly is disposed inside the lower connector. The flow divider pipe is provided with a flow divider hole. Part of the sand flushing fluid in the internal annulus of the sand flushing assembly can enter the flow divider pipe through the flow divider hole and flow through the sand flushing nozzle assembly, the lower connector and the sand flushing head in sequence, and finally be ejected through the sand flushing hole. The port of the bypass pipe is located between the throat and the sand suction nozzle assembly. Part of the sand flushing fluid in the internal annulus of the sand flushing assembly can flow upward through the sand suction nozzle assembly, and form a negative pressure zone between the throat and the sand suction nozzle assembly, so that the sand-carrying fluid in the annulus of the casing can be sucked into the negative pressure zone through the bypass pipe, and finally mixed with the sand flushing fluid and discharged back.

[0014] Secondly, the present invention provides a method for using a sand flushing process tubing in offshore oilfields, comprising the following steps: S1 connects the components of the offshore oilfield sand flushing process string in sequence and connects the fluid flow reversing device to the bottom of the drill pipe; S2, the offshore oilfield sand flushing process tubing is lowered into the preset position inside the production casing via the drill pipe, at which point the uprighting and packer assembly is set on the inner wall of the production casing; S3, inject flushing fluid into the annulus of the production casing. The flushing fluid enters the inlet hole and flows sequentially through the fluid flow reversing device, safety joint, centralizing and sealing assembly, double-wall drill pipe and the flushing channel formed by the internal annulus of the flushing assembly, and finally sprays out through the flushing hole. At the same time, the sand-carrying fluid in the production casing annulus enters the bypass pipe and flows sequentially through the sand flushing assembly, double-wall drill pipe, centralizing and sealing assembly, safety joint, and the return channel formed by the fluid flow reversing device, and finally returns to the wellhead for discharge.

[0015] As can be seen from the above technical solution, the offshore oilfield sand flushing process tubing and its usage method provided by the present invention have the following advantages: This offshore oilfield sand flushing process string can create its own sand flushing circulation channel, reducing the loss of sand flushing fluid in low-pressure lost circulation wells, thus meeting the sand flushing operation needs of offshore low-pressure lost circulation wells and large lost circulation wells, and improving the sand flushing operation effect. At the same time, the operation of this offshore oilfield sand flushing process string is very convenient, effectively improving the operation efficiency.

[0016] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0018] Figure 1 This is a schematic diagram of the overall structure of the offshore oilfield sand flushing process tubing in Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view of the fluid flow commutator in Embodiment 1 of the present invention; Figure 3 This is a cross-sectional view of the safety connector in Embodiment 1 of the present invention; Figure 4 This is a cross-sectional view of the first straightening device in Embodiment 1 of the present invention; Figure 5 This is a cross-sectional view of the packer in Embodiment 1 of the present invention; Figure 6 This is a cross-sectional view of the second centralizer in Embodiment 1 of the present invention; Figure 7 This is a cross-sectional view of the double-walled drill pipe in Embodiment 1 of the present invention; Figure 8 This is a cross-sectional view of the sand flushing assembly in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the usage status of the offshore oilfield sand flushing process tubing in Embodiment 2 of the present invention, mainly showing the flow direction of the sand flushing fluid and the sand-carrying fluid at the sand flushing assembly.

[0019] Explanation of reference numerals in the attached figures: 1. Fluid flow reversing device; 2. Safety joint; 3. Centralizing and packer assembly; 31. First centralizer; 32. Packer; 33. Second centralizer; 4. Double-wall drill pipe; 5. Sand flushing assembly; 51. Sand flushing outer tube; 52. Sand flushing head; 53. Support inner tube; 54. Central tube; 55. Adjusting cylinder; 56. Diffuser; 57. Throat; 58. Sand suction nozzle assembly; 59. Sand flushing nozzle assembly; 60. Diverter pipe ; 61. Diverter hole; 6. Liquid inlet hole; 7. Sand flushing hole; 8. Bypass pipe; 9. Main body assembly; 10. Inner tube of flow channel; 11. Female plug; 12. Male plug; 13. Upper connector; 14. Lower connector; 15. First limit retaining ring; 16. Second limit retaining ring; 17. Straightening rotor; 18. Straightening groove; 19. Straightening block; 20. Sealing ring; 21. Upper outer tube; 22. Lower outer tube; 23. Shear pin. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0021] Example 1 like Figures 1-8 The illustration shows an embodiment of the present invention, which discloses a sand flushing process tubing for offshore oilfields. The tubing includes a fluid flow diverter 1, a safety joint 2, a centralizing and packer assembly 3, a double-wall drill pipe 4, and a sand flushing assembly 5, which are coaxially connected from top to bottom. The internal annular spaces of the fluid flow diverter 1, the safety joint 2, the centralizing and packer assembly 3, the double-wall drill pipe 4, and the sand flushing assembly 5 are interconnected to form a sand flushing channel through which the sand flushing fluid flows. The internal cavities of the fluid flow diverter 1, the safety joint 2, the centralizing and packer assembly 3, the double-wall drill pipe 4, and the sand flushing assembly 5 are interconnected to form a return flow channel through which the sand-carrying fluid flows.

[0022] In one embodiment, such as Figure 1 As shown, the fluid flow converter 1 is provided with a fluid inlet 6, and the sand flushing assembly 5 is provided with a sand flushing hole 7 and a bypass pipe 8. The fluid inlet 6 and the sand flushing hole 7 are respectively connected to the sand flushing channel, and the bypass pipe 8 is connected to the return channel. That is, the sand flushing fluid can enter the sand flushing channel through the fluid inlet 6 and be ejected through the sand flushing hole 7. The sand-carrying fluid can enter the return channel through the bypass pipe 8 and return to the wellhead for discharge.

[0023] The offshore oilfield sand flushing process string in this embodiment can build its own sand flushing circulation channel, reduce the loss of sand flushing fluid in low-pressure lost circulation wells, meet the sand flushing operation requirements of offshore low-pressure lost circulation wells and large lost circulation wells, and improve the sand flushing operation effect.

[0024] In one embodiment, such as Figure 1As shown, the centralizing and packing assembly 3 includes a first centralizer 31, a packer 32, and a second centralizer 33 connected sequentially from top to bottom. The top of the first centralizer 31 is connected to the safety joint 2, and the bottom of the second centralizer 33 is connected to the double-wall drill pipe 4.

[0025] By setting two centralizers, the centralizing effect is effectively improved, ensuring that the offshore oilfield sand flushing process tubing is centered within the production casing. In this embodiment, the first centralizer 31 is an elastic centralizer, the second centralizer 33 is a vortex centralizer, and the packer 32 is a double-cup packer 32. Of course, in other embodiments, other types of centralizers and packers 32 can also be selected, which will not be listed in detail here.

[0026] In one embodiment, such as Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown, the fluid flow reversing device 1, safety joint 2, first centralizer 31, packer 32, second centralizer 33, double-wall drill pipe 4, and sand flushing assembly 5 each include a coaxially arranged main body assembly 9 and flow channel inner tube 10. An annular space is formed between the main body assembly 9 and the flow channel inner tube 10, and two adjacent main body assemblies 9 are connected by threads to facilitate the rapid assembly and disassembly of the offshore oilfield sand flushing process tubing by the staff.

[0027] In one embodiment, such as Figures 2-8 As shown, the bottom of the inner tube 10 of the flow channel of the fluid flow reversing device 1, safety connector 2, first stabilizer 31, packer 32, second stabilizer 33 and double-wall drill pipe 4 is provided with a female plug 11, and the top of the inner tube 10 of the flow channel of the safety connector 2, first stabilizer 31, packer 32, second stabilizer 33, double-wall drill pipe 4 and sand flushing assembly 5 is provided with a male plug 12, and the male plug 12 is tightly inserted with the corresponding female plug 11, that is, two adjacent inner tubes 10 are connected by plugging.

[0028] In one embodiment, such as Figure 2 , Figure 8 As shown, the liquid inlet 6 is located on the main body assembly 9 of the flow converter 1. An upper connector 13 is located at the top of the inner tube 10 of the flow channel of the flow converter 1, and the upper connector 13 is connected to the main body assembly 9 of the flow converter 1. A sand flushing hole 7 and a bypass pipe 8 are respectively located on the main body assembly 9 of the sand flushing assembly 5. A lower connector 14 is located at the bottom of the inner tube 10 of the flow channel of the sand flushing assembly 5, and the lower connector 14 is connected to the main body assembly 9 of the sand flushing assembly 5.

[0029] In one embodiment, such as Figures 2-8As shown, a first limiting ring 15 is provided inside the body assembly 9 of the fluid flow reversing device 1, and the first limiting ring 15 is used to prevent the upper connector 13 from moving upward. A second limiting ring 16 is provided inside the body assembly 9 of the safety connector 2, the first stabilizer 31, the packer 32, the second stabilizer 33, the double-wall drill pipe 4, and the sand flushing assembly 5, respectively, and the second limiting ring 16 is used to prevent the corresponding male connector 12 from moving upward.

[0030] In one embodiment, such as Figures 2-8 As shown, each male plug 12 is provided with a centralizing rotor 17, and the safety connector 2, the first centralizer 31, the packer 32, the second centralizer 33, the double-wall drill rod 4, and the main body assembly 9 of the sand flushing assembly 5 are provided with centralizing grooves 18 for the corresponding centralizing rotor 17 to be tightly inserted, so as to improve the support, limiting and centering effect.

[0031] In one embodiment, such as Figures 2-8 As shown, the inner tube 10 of the flow channel is connected to the corresponding male plug 12 and female plug 11 by a plug-in mating method. Each female plug 11 is provided with a straightening block 19, and the straightening block 19 can abut against the inner wall of the corresponding body assembly 9 to limit the movement, thereby further improving the support, limiting and straightening effect.

[0032] In one embodiment, such as Figures 2-8 As shown, each male plug 12 is provided with a sealing ring 20, and the sealing ring 20 can seal with the corresponding female plug 11 to ensure the sealing effect between the corresponding male plug 12 and female plug 11. At the same time, the upper connector 13 can also be provided with a sealing ring 20 to ensure the sealing effect.

[0033] In one embodiment, such as Figure 3 As shown, the main body assembly 9 of the safety connector 2 includes an upper outer pipe 21 and a lower outer pipe 22. The upper outer pipe 21 and the lower outer pipe 22 are inserted into each other and connected by a shear pin 23. If the offshore oilfield sand flushing process tubing gets stuck in the production casing, the drill pipe can be lifted and the shear pin 23 can be broken to achieve emergency release.

[0034] In one embodiment, such as Figure 5 As shown, the main body assembly 9 of the sandblasting assembly 5 includes a sandblasting outer tube 51 and a sandblasting head 52, a lower connector 14 is connected between the sandblasting outer tube 51 and the sandblasting head 52, and a sandblasting hole 7 is provided at the bottom of the sandblasting head 52.

[0035] In one embodiment, such as Figure 5As shown, the inner tube 10 of the sand flushing assembly 5 includes a supporting inner tube 53, a central tube 54, an adjusting cylinder 55, a diffuser 56, a throat 57, a sand suction nozzle assembly 58, a sand flushing nozzle assembly 59, and a diverter 60. The adjusting cylinder 55, the diffuser 56, and the throat 57 are arranged sequentially from top to bottom inside the central tube 54. The top of the supporting inner tube 53 is connected to the male plug 12 of the sand flushing assembly 5, and the bottom is connected to the central tube 54. The supporting inner tube 53 presses and fixes the adjusting cylinder 55, the diffuser 56, and the throat 57 inside the central tube 54.

[0036] In one embodiment, such as Figure 5 As shown, the sand suction nozzle assembly 58 is disposed inside the central tube 54 and is located below the throat tube 57. The top of the diversion tube 60 is connected to the central tube 54 and the bottom is connected to the lower connector 14. The diversion tube 60 presses and fixes the sand suction nozzle assembly 58 inside the central tube 54.

[0037] In one embodiment, such as Figure 5 As shown, the sand flushing nozzle assembly 59 is disposed inside the lower connector 14, and the diversion pipe 60 is provided with a diversion hole 61. Part of the sand flushing fluid in the internal annulus of the sand flushing assembly 5 can enter the diversion pipe 60 through the diversion hole 61 and flow through the sand flushing nozzle assembly 59, the lower connector 14 and the sand flushing head 52 in sequence, and finally be ejected through the sand flushing hole 7.

[0038] In one embodiment, such as Figure 5 As shown, the port of the bypass pipe 8 is located between the throat pipe 57 and the sand suction nozzle assembly 58. Part of the sand flushing fluid in the internal annulus of the sand flushing assembly 5 can flow upward through the sand suction nozzle assembly 58, and a negative pressure zone is formed between the throat pipe 57 and the sand suction nozzle assembly 58, so that the sand-carrying fluid in the casing annulus can be sucked into the negative pressure zone through the bypass pipe 8, and finally mixed with the sand flushing fluid and discharged back.

[0039] Example 2 like Figure 9 The image shows Embodiment 2 of the present invention, which discloses a method for using a sand flushing process tubing in offshore oilfields, including the following steps: S1, connect the components of the offshore oilfield sand flushing process string in sequence, and connect the fluid flow reversing device 1 to the bottom of the drill pipe; S2, the offshore oilfield sand flushing process tubing is lowered into the preset position inside the production casing via the drill pipe, at which point the centralizing and sealing assembly 3 is set on the inner wall of the production casing; S3, inject flushing fluid into the annulus of the production casing. The flushing fluid enters the inlet hole 6 and flows sequentially through the flushing channel formed by the internal annulus of the fluid flow reversing device 1, safety joint 2, centralizing and sealing assembly 3, double-wall drill pipe 4, and flushing assembly 5, and finally sprays out through the flushing hole 7. At the same time, the sand-carrying fluid in the production casing annulus enters the bypass pipe 8 and flows sequentially through the backflow channel formed by the sand flushing assembly 5, the double-wall drill pipe 4, the centralizing and sealing assembly 3, the safety joint 2, and the fluid flow reversing device 1, and finally returns to the wellhead for discharge.

[0040] As described above, using this offshore oilfield sand flushing process string for sand flushing operations offers several advantages. Firstly, the string can create its own sand flushing circulation channel, reducing the loss of flushing fluid in low-pressure lost circulation wells. This meets the sand flushing requirements of both low-pressure and large lost circulation wells, and improves the effectiveness of the sand flushing operation. Secondly, this offshore oilfield sand flushing process string is very easy to operate, effectively improving operational efficiency, and it also has an emergency release capability, enhancing safety during use.

[0041] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0042] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A tubing string for offshore oilfield sand flushing process, characterized in that, The assembly includes a fluid flow diverter (1), a safety connector (2), a centralizing and sealing assembly (3), a double-wall drill pipe (4), and a sand flushing assembly (5) connected sequentially from top to bottom. The internal annulus of the fluid flow diverter (1), safety connector (2), centralizing and sealing assembly (3), double-wall drill pipe (4), and sand flushing assembly (5) are interconnected to form a sand flushing channel through which the sand flushing fluid flows. The internal cavities of the fluid flow diverter (1), safety connector (2), centralizing and sealing assembly (3), double-wall drill pipe (4), and sand flushing assembly (5) are interconnected to form a return channel through which the sand-carrying fluid flows. The fluid flow diverter (1) is provided with a fluid inlet (6), and the sand flushing assembly (5) is provided with a sand flushing hole (7) and a bypass pipe (8). The fluid inlet (6) and the sand flushing hole (7) are respectively connected to the sand flushing channel, and the bypass pipe (8) is connected to the return channel.

2. The offshore oilfield sand flushing process tubing according to claim 1, characterized in that, The centralizing and packing assembly (3) includes a first centralizer (31), a packer (32) and a second centralizer (33) connected sequentially from top to bottom. The top of the first centralizer (31) is connected to the safety joint (2), and the bottom of the second centralizer (33) is connected to the double-wall drill pipe (4).

3. The offshore oilfield sand flushing process tubing according to claim 2, characterized in that, The fluid flow converter (1), safety connector (2), first stabilizer (31), packer (32), second stabilizer (33), double-wall drill pipe (4), and sand flushing assembly (5) each include a coaxially arranged body assembly (9) and flow channel inner tube (10). The bottom of the flow channel inner tube (10) of the fluid flow converter (1), safety connector (2), first stabilizer (31), packer (32), second stabilizer (33), and double-wall drill pipe (4) is provided with a female plug (11). The top of the flow channel inner tube (10) of the safety connector (2), first stabilizer (31), packer (32), second stabilizer (33), double-wall drill pipe (4), and sand flushing assembly (5) is provided with a male plug (12). The male plug (12) and the corresponding female plug (11) are tightly inserted and matched. The inlet hole (6) is provided on the body assembly (9) of the flow converter (1). The top of the inner tube (10) of the flow channel of the flow converter (1) is provided with an upper connector (13), and the upper connector (13) is connected to the body assembly (9) of the flow converter (1). The sand flushing hole (7) and the bypass pipe (8) are respectively provided on the body assembly (9) of the sand flushing assembly (5). The bottom of the inner tube (10) of the flow channel of the sand flushing assembly (5) is provided with a lower connector (14), and the lower connector (14) is connected to the body assembly (9) of the sand flushing assembly (5).

4. The offshore oilfield sand flushing process tubing according to claim 3, characterized in that, The main body assembly (9) of the fluid flow converter (1) is provided with a first limiting ring (15), which is used to prevent the upper connector (13) from moving upward. The main body assembly (9) of the safety connector (2), the first stabilizer (31), the packer (32), the second stabilizer (33), the double-wall drill pipe (4) and the sand flushing assembly (5) are respectively provided with a second limiting ring (16), which is used to prevent the corresponding male plug (12) from moving upward.

5. The offshore oilfield sand flushing process tubing according to claim 3, characterized in that, Each of the male plugs (12) is provided with a centralizing rotor (17), and the safety connector (2), the first centralizer (31), the packer (32), the second centralizer (33), the double-wall drill pipe (4), and the main body assembly (9) of the sand flushing assembly (5) are respectively provided with centralizing grooves (18) for the corresponding centralizing rotor (17) to be tightly engaged.

6. The offshore oilfield sand flushing process tubing according to claim 3, characterized in that, Each of the male plugs (12) is provided with a sealing ring (20), and the sealing ring (20) can be sealed and fitted with the corresponding female plug (11).

7. The offshore oilfield sand flushing process tubing according to claim 3, characterized in that, The safety connector (2) body assembly (9) includes an upper outer tube (21) and a lower outer tube (22), the upper outer tube (21) and the lower outer tube (22) are inserted into each other, and the upper outer tube (21) and the lower outer tube (22) are connected by a shear pin (23).

8. The offshore oilfield sand flushing process tubing according to claim 3, characterized in that, The main body assembly (9) of the sand-washing assembly (5) includes a sand-washing outer tube (51) and a sand-washing head (52). The lower connector (14) is connected between the sand-washing outer tube (51) and the sand-washing head (52), and the sand-washing hole (7) is located at the bottom of the sand-washing head (52).

9. The offshore oilfield sand flushing process tubing according to claim 8, characterized in that, The inner tube (10) of the sand flushing assembly (5) includes a supporting inner tube (53), a central tube (54), an adjusting cylinder (55), a diffuser (56), a throat (57), a sand suction nozzle assembly (58), a sand flushing nozzle assembly (59), and a diverter pipe (60). The adjusting cylinder (55), the diffuser (56), and the throat (57) are arranged sequentially from top to bottom inside the central tube (54). The top of the supporting inner tube (53) is connected to the male plug (12) of the sand flushing assembly (5), and the bottom is connected to the central tube (54). The supporting inner tube (53) presses and fixes the adjusting cylinder (55), the diffuser (56), and the throat (57) inside the central tube (54). The sand suction nozzle assembly (58) is disposed inside the central tube (54) and is located below the throat tube (57). The top of the diverter tube (60) is connected to the central tube (54) and the bottom is connected to the lower connector (14). The diverter tube (60) presses and fixes the sand suction nozzle assembly (58) inside the central tube (54). The sand-flushing nozzle assembly (59) is disposed inside the lower connector (14), and the diversion pipe (60) is provided with a diversion hole (61). Part of the sand-flushing liquid in the internal annulus of the sand-flushing assembly (5) can enter the diversion pipe (60) through the diversion hole (61), and flow through the sand-flushing nozzle assembly (59), the lower connector (14) and the sand-flushing head (52) in sequence, and finally be ejected through the sand-flushing hole (7). The port of the bypass pipe (8) is located between the throat pipe (57) and the sand suction nozzle assembly (58). Part of the sand flushing fluid in the internal annulus of the sand flushing assembly (5) can flow upward through the sand suction nozzle assembly (58) and form a negative pressure zone between the throat pipe (57) and the sand suction nozzle assembly (58), so that the sand-carrying fluid in the annulus of the casing can be sucked into the negative pressure zone through the bypass pipe (8) and finally mixed with the sand flushing fluid before being discharged back.

10. A method of using a offshore oilfield sand flushing process tubing according to any one of claims 1-9, characterized in that, Includes the following steps: S1, connect the components of the offshore oilfield sand flushing process string in sequence, and connect the fluid flow converter (1) to the bottom of the drill pipe; S2, the offshore oilfield sand flushing process tubing is lowered into the preset position inside the production casing by the drill pipe, at which time the uprighting and sealing assembly (3) is set on the inner wall of the production casing; S3, inject flushing fluid into the annulus of the production casing. The flushing fluid enters the inlet hole (6) and flows through the flushing channel formed by the internal annulus of the fluid flow reversing device (1), safety joint (2), centralizing and sealing assembly (3), double-wall drill pipe (4) and flushing assembly (5) in sequence, and finally sprays out through the flushing hole (7). At the same time, the sand-carrying fluid in the production casing annulus enters the bypass pipe (8) and flows sequentially through the sand flushing assembly (5), double-wall drill pipe (4), centralizing and sealing assembly (3), safety joint (2), and the internal cavity of the fluid flow diverter (1) to form a return channel, and finally returns to the wellhead for discharge.

Images