Sand control well completion structure with easy pullout downhole sand control string

Abstract

The application belongs to the technical field of oil exploitation, and is especially a sand prevention well completion structure of an easily-pulled-out downhole sand prevention pipe column, which comprises a loose sandstone formation, an isolation body filling layer and a sand prevention pipe column, an inner part of the loose sandstone formation is provided with a well mouth, the sand prevention pipe column is arranged in the inner part of the well mouth, an inner part of the sand prevention pipe column is provided with the isolation body filling layer, an upper end of the well mouth is provided with a positioning mechanism, an upper end of the positioning mechanism is provided with a sealing mechanism, the positioning mechanism comprises a seat ring, a limiting plug and a positioning sliding cylinder, the bottom end of the seat ring is fixedly connected with the limiting plug, the limiting plug is inserted into the upper end of the well mouth, and the inner part of the limiting plug is provided with the positioning sliding cylinder, the positioning mechanism and the sealing mechanism are arranged, the downhole running and pulling-out operation of the sand prevention pipe column relative to the well mouth is facilitated, the upper part of the isolation body filling layer can be sealed and protected, and the use effect is better.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a sand control well completion structure with an easily removable downhole sand control tubing string. Background Technology

[0002] Global oil and gas fields contain a large number of loose sandstone reservoirs prone to sand production. For oil and gas wells in loose sandstone reservoirs, whether vertical, deviated, or horizontal, sand production is one of the most frequently encountered problems in oilfield development. Therefore, preventing sand production from the formation is extremely important. Currently, there are two commonly used mechanical sand control technologies for oil and gas wells: one is to run a sand control tubing string into the well, and the other is to first run a sand control tubing string and then fill the annulus between the sand control tubing string and the well wall with gravel, using the gravel layer to block formation sand from entering the wellbore. When the tubing is pulled out, the formation sand or gravel will generate huge frictional resistance with the sand control tubing string that it is tightly wrapped with, making it difficult to pull out the sand control tubing and making the operation inconvenient.

[0003] In the prior art, Chinese invention patent with publication number CN201320799528.0 discloses a sand control well completion structure that allows for easy removal of downhole sand control tubing. This invention establishes a permeable isolation body in the annulus between the well wall and the sand control tubing, which generates low resistance to the tubing when it is pulled up. This is referred to as a permeable, low-resistance isolation body. When the tubing is pulled up, the frictional resistance generated between the isolation body and the tubing is very low, and the tubing can be easily pulled out.

[0004] However, existing sand control well completion structures with easily removable downhole sand control tubing still have the following shortcomings during use: First, the sand control tubing lacks proper positioning relative to the wellhead, making it difficult to center the tubing during insertion and removal. The sand control tubing in the wellhead is prone to deflection, further causing uneven thickness of the isolator filling layer around the tubing, thus affecting the smooth removal of the tubing. Second, during tubing removal operations, isolator particles from the isolator filling layer adhere to and are carried out around the outer wall of the sand control tubing in the wellhead. Cleaning these isolator particles around the outer wall of the sand control tubing is difficult, causing inconvenience for subsequent maintenance and future use. Furthermore, the upper sealing effect of the isolator filling layer is poor after filling, and the upper part of the isolator filling layer lacks good protection. External flying sand can easily enter the isolator filling layer from the upper part and mix with the isolator particles inside, increasing the difficulty of repeated screening and reuse of the isolator particles in the isolator filling layer. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a sand control well completion structure with an easily removable downhole sand control tubing string, featuring simple positioning, convenient wall scraping, and quick sealing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a sand control well completion structure with an easily removable downhole sand control tubing string, comprising a loose sandstone formation, an isolating filler layer, and a sand control tubing string. A wellhead is formed within the loose sandstone formation, and the sand control tubing string is installed inside the wellhead. An isolating filler layer is installed around the sand control tubing string within the wellhead. A positioning mechanism is provided at the upper end of the wellhead, and a sealing mechanism is provided at the upper end of the positioning mechanism. The positioning mechanism includes a seat ring, a limiting insert, and a positioning slide. The bottom end of the seat ring is fixedly connected to the limiting insert, and the limiting insert is inserted into the upper end of the wellhead. The device includes an internal positioning slide cylinder. An upper scraper ring is fixedly connected to the upper end of the positioning slide cylinder, and a lower scraper ring is fixedly connected to the bottom end of the positioning slide cylinder. Both the upper and lower scraper rings are fixedly connected to reinforcing scraper heads. Several roller grooves are formed around the inside of the positioning slide cylinder. Ball bearings are movably connected inside the roller grooves, and oil passage pipes are formed between adjacent roller grooves. Several oil injection pipes are formed around the inside of the upper end of the positioning slide cylinder, and the oil injection pipes communicate with the oil passage pipes. The sealing mechanism includes a sealing ring and a sealing ring. The sealing ring is fixed to the bottom end of the sealing ring, and the sealing ring is engaged in the gap between the seat ring and the positioning slide cylinder.

[0007] As a preferred technical solution of the sand control well completion structure for easy-to-pull-out downhole sand control tubing of the present invention, lower handles are fixedly connected to the left and right ends of the middle positions on both sides of the seat ring, and a limiting recess is opened at the upper end of one side of the lower handle. Upper handles are fixedly connected to the left and right ends of the middle positions on both sides of the sealing ring, and a limiting retaining shaft is fixedly connected to the bottom end of one side of the upper handle. The limiting recess and the limiting retaining shaft are engaged with each other.

[0008] As a preferred technical solution of the sand control well completion structure of the present invention, which is easy to pull out downhole sand control tubing, the bottom end of the seat ring is fixedly connected with several limiting inserts, the limiting inserts are conical in shape and interlock with the loose sandstone formation.

[0009] As a preferred technical solution of the sand control well completion structure of the present invention, which is an easy-to-pull-out downhole sand control tubing string, the bottom end of the seat ring is in contact with the upper end of the loose sandstone formation, a shock-absorbing washer is fixedly connected inside the upper end of the seat ring and the shock-absorbing washer is a rubber component, the bottom end of the sealing ring is in contact with the upper end of the seat ring and the bottom end face of the sealing ring is in elastic contact with the shock-absorbing washer.

[0010] As a preferred technical solution of the sand control well completion structure of the present invention, which is an easy-to-pull-out downhole sand control tubing string, a plurality of connecting rods are provided between the limiting insert and the positioning slide, and the two ends of the connecting rods are respectively fixedly connected to the inner wall of the limiting insert and the outer wall of the positioning slide.

[0011] As a preferred technical solution of the sand control well completion structure of the present invention, which is an easy-to-pull-out downhole sand control tubing string, the upper scraper ring, the lower scraper ring and the reinforcing scraper head are all triangular in cross-section, and the reinforcing scraper head is a manganese steel component.

[0012] As a preferred technical solution of the sand control well completion structure of the present invention, which is easy to pull out downhole sand control tubing, a number of connecting strips are fixedly connected around the upper outer wall of the positioning slide tube, a sealing block is fixedly connected to one side of the connecting strip, a sealing plug is fixedly connected to the bottom end of the sealing block, and the sealing plug is interlocked with the upper end of the oil injection pipe.

[0013] As a preferred technical solution of the sand control well completion structure of the present invention, which is an easy-to-pull-out downhole sand control tubing string, the connecting strip and the sealing plug are both rubber components.

[0014] As a preferred technical solution of the sand control well completion structure of the present invention, which is an easy-to-pull-out downhole sand control pipe string, the upper end of the sealing ring is fixedly connected with a reinforcing rib ring, and the inner wall of the reinforcing rib ring is in contact with the outer wall of the positioning slide.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. In use, the positioning mechanism and the sealing mechanism are placed centrally above the wellhead. The limiting cylinder in the positioning mechanism is inserted centrally into the upper end of the wellhead for limiting, thereby completing the installation of the positioning mechanism and the sealing mechanism relative to the wellhead. Then, the sand control pipe string is inserted centrally into the wellhead and lowered to the predetermined position. During the lowering of the sand control pipe string, the positioning slide in the positioning mechanism facilitates the centered lowering of the sand control pipe string, and the sand control pipe string in the wellhead is not prone to deflection. Similarly, when performing pipe pulling operations, the positioning slide in the positioning mechanism facilitates the smooth upward pulling of the sand control pipe string.

[0017] 2. In use, the upper scraper ring at the top of the positioning slide can scrape away the ash residue adhering to the outer wall of the sand-proof pipe column during the lowering process, ensuring that the outer wall of the sand-proof pipe column is flat and smooth, facilitating the smooth lowering and subsequent pulling out of the sand-proof pipe column. The lower scraper ring at the bottom of the positioning slide can scrape away the isolation particles adhering to the outer wall of the sand-proof pipe column during the pulling process, preventing the isolation particles in the isolation filling layer from being adhered and carried out by the sand-proof pipe column, eliminating unnecessary cleaning time, and facilitating the subsequent maintenance and use of the sand-proof pipe column. Furthermore, the upper and lower scraper rings with reinforced scraper heads are durable, not easily deformed or damaged, and have a good scraping effect.

[0018] 3. In use, the rolling balls inside the lower scraper ring facilitate the smooth movement of the sand-proof tube relative to the positioning slide, so as to facilitate the smooth insertion and removal of the sand-proof tube. Furthermore, through the oil passage and oil injection pipe connected to the lower scraper ring, lubricating fluid can be injected into the roller groove to facilitate low-wear rolling of the balls inside the lower scraper ring, improve the performance of the balls, and extend the service life of the balls.

[0019] 4. In use, the sealing mechanism is raised by the relative positioning mechanism, which separates the sealing ring in the sealing mechanism from the positioning mechanism and causes the sealing ring in the sealing mechanism to come out of the positioning mechanism. Then, the wellhead is filled with separator particles through the gap between the seat ring and the positioning slide in the positioning mechanism to form a separator filling layer. After that, the sealing mechanism is lowered by the relative positioning mechanism, which makes the sealing ring fit with the seat ring and seals the gap between the seat ring and the positioning slide, thereby completing the better sealing of the upper part of the separator filling layer. This facilitates the sealing and protection of the upper part of the separator filling layer, and prevents external flying sand from entering the separator filling layer from the upper part. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 for Figure 1 An enlarged structural diagram at point A;

[0023] Figure 3 This is a schematic diagram of a partial cross-sectional structure of the positioning slide and the sand-proof pipe column of the present invention;

[0024] Figure 4 for Figure 1 A magnified structural diagram at point B;

[0025] Figure 5 This is a cross-sectional structural diagram of the connection state between the positioning mechanism and the sealing mechanism of the present invention;

[0026] Figure 6 This is a schematic diagram of the connection structure between the positioning mechanism and the sealing mechanism of the present invention;

[0027] Figure 7 This is a schematic cross-sectional view of the positioning mechanism and the sealing mechanism of the present invention in a separated state;

[0028] Figure 8 This is a schematic diagram of the positioning mechanism and the sealing mechanism of the present invention in a separated state;

[0029] Figure 9 This is a top view of the positioning mechanism of the present invention;

[0030] Figure 10 This is a bottom view schematic diagram of the positioning mechanism of the present invention;

[0031] Figure 11 This is a top view of the sealing mechanism of the present invention;

[0032] Figure 12 This is a bottom view of the sealing mechanism of the present invention.

[0033] In the diagram: 1. Positioning mechanism; 2. Seat ring; 3. Lower grip; 4. Limiting insert; 5. Shock-absorbing washer; 6. Limiting insert; 7. Connecting rod; 8. Positioning slide; 9. Sealing mechanism; 10. Sealing ring; 11. Upper grip; 12. Sealing ring; 13. Reinforcing rib ring; 14. Upper scraper ring; 15. Lower scraper ring; 16. Groove; 17. Ball bearing; 18. Oil passage pipe; 19. Oil injection pipe; 20. Connecting strip; 21. Sealing block; 22. Sealing plug; 23. Reinforcing scraper head; 24. Limiting recess; 25. Limiting retainer; 26. Loose sandstone stratum; 27. Isolator filling layer; 28. Sand control pipe column. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example

[0036] Please see Figure 1-12 The present invention provides the following technical solution: a sand control well completion structure with an easily removable downhole sand control string, comprising a loose sandstone formation 26, an isolator filling layer 27, and a sand control string 28. A wellhead is provided inside the loose sandstone formation 26, and the sand control string 28 is installed inside the wellhead. An isolator filling layer 27 is installed around the sand control string 28 inside the wellhead. The loose sandstone formation 26, the isolator filling layer 27, and the sand control string 28 are all prior art. Please refer to the Chinese invention patent with publication number CN201320799528.0 for a sand control well completion structure with an easily removable downhole sand control string, which will not be described in detail here.

[0037] Reference Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 As shown, a positioning mechanism 1 is provided at the upper end of the wellhead. The positioning mechanism 1 includes a seat ring 2, a limiting insert 6, and a positioning slide 8. The bottom end of the seat ring 2 is fixedly connected to the limiting insert 6, and the limiting insert 6 is inserted into the upper end of the wellhead. The positioning slide 8 is provided inside the limiting insert 6. Several limiting strips 4 are fixedly connected to the bottom end of the seat ring 2. The limiting strips 4 have a conical structure and are inserted into the loose sandstone stratum 26. The bottom end of the seat ring 2 is in contact with the upper end of the loose sandstone stratum 26. A shock-absorbing washer 5, which is a rubber component, is fixedly connected inside the upper end of the seat ring 2. The bottom end of the sealing ring 10 is in contact with the upper end of the seat ring 2, and the bottom end face of the sealing ring 10 is in elastic contact with the shock-absorbing washer 5. Several connecting rods 7 are provided between the limiting insert 6 and the positioning slide 8, and the two ends of the connecting rods 7 are respectively connected to the inner wall of the limiting insert 6 and the positioning slide 8. The outer wall of the cylinder 8 is fixedly connected. During use, the positioning mechanism 1 and the sealing mechanism 9, which are connected together, are placed in the center above the wellhead. The limiting insert 6 in the positioning mechanism 1 is inserted into the upper end of the wellhead for limiting, thereby completing the installation of the positioning mechanism 1 and the sealing mechanism 9 relative to the wellhead. Then, the sand control pipe string 28 is inserted into the wellhead in the center and lowered to the predetermined position. During the lowering of the sand control pipe string 28, the positioning slide 8 in the positioning mechanism 1 facilitates the centering of the sand control pipe string 28. The sand control pipe string 28 in the wellhead is not easy to deviate. Similarly, when the pipe is pulled out, the positioning slide 8 in the positioning mechanism 1 facilitates the smooth upward pulling of the sand control pipe string 28. The limiting insert 4 is used to reinforce the seat ring 2 relative to the loose sandstone stratum 26 and prevent the positioning mechanism 1 from rotating. The shock-absorbing washer 5 is used to reduce shock and wear after the sealing ring 10 falls relative to the seat ring 2.

[0038] Reference Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 7 , Figure 9 and Figure 10As shown, an upper scraper ring 14 is fixedly connected to the upper end of the positioning slide cylinder 8, and a lower scraper ring 15 is fixedly connected to the bottom end of the positioning slide cylinder 8. Both the upper scraper ring 14 and the lower scraper ring 15 are fixedly connected to a reinforcing scraper head 23. The cross-sections of the upper scraper ring 14, the lower scraper ring 15, and the reinforcing scraper head 23 are triangular structures, and the reinforcing scraper head 23 is a manganese steel component. During use, the upper scraper ring 14 at the upper end of the positioning slide cylinder 8 can be used to scrape away the ash residue adhering to the outer wall of the sand-proof pipe column 28 during the lowering process, ensuring that the outer wall of the sand-proof pipe column 28 is smooth and flat. During the smooth lowering and subsequent pulling out of the sand control tube 28, the lower scraper ring 15 at the bottom of the positioning slide cylinder 8 can scrape off the isolation particles adhering to the outer wall of the sand control tube 28 during the upward pulling process. This prevents the isolation particles in the isolation filling layer 27 from being adhered and carried out by the sand control tube 28, eliminating unnecessary cleaning time and facilitating the subsequent maintenance and use of the sand control tube 28. Furthermore, the upper scraper ring 14 and lower scraper ring 15 with reinforced scraper heads 23 are durable, not easily deformed or damaged, and have a good scraping effect.

[0039] Reference Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 7 , Figure 9 and Figure 10 As shown, the positioning slide cylinder 8 has several grooves 16 around its interior, with ball bearings 17 movably connected inside each groove 16. Oil pipes 18 are provided between adjacent grooves 16. Several oil injection pipes 19 are provided around the interior of the upper end of the positioning slide cylinder 8, and these pipes communicate with the oil pipes 18. Several connecting strips 20 are fixedly connected around the outer wall of the upper end of the positioning slide cylinder 8. A sealing block 21 is fixedly connected to one side of each connecting strip 20, and a sealing plug 22 is fixedly connected to the bottom of each sealing block 21. The sealing plug 22 engages with the upper end of each oil injection pipe 19. Both the connecting strips 20 and the sealing plug 22 are rubber components. During use, the ball bearings 17 rolling inside the lower scraper ring 15... 7. Facilitates the smooth movement of the sand-proof tube string 28 relative to the positioning slide cylinder 8, enabling the smooth insertion and removal of the sand-proof tube string 28. Furthermore, through the oil passage pipe 18 and oil injection pipe 19 connected to the lower scraper ring 15, lubricant can be injected into the roller groove 16 to facilitate low-wear rolling of the ball bearings 17 within the lower scraper ring 15, improving the performance of the ball bearings 17 and extending their service life. The connecting strip 20 is used to connect the sealing block 21 and the positioning slide cylinder 8, making it less likely for the sealing block 21 and sealing plug 22 to fall off or be lost after being removed. The sealing block 21 and sealing plug 22 are used to seal the oil injection pipe 19, preventing dust and dirt from entering the oil injection pipe 19, the roller groove 16, and the oil passage pipe 18.

[0040] Reference Figure 1 , Figure 2 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 11 and Figure 12 The upper end of the positioning mechanism 1 is provided with a sealing mechanism 9, which includes a sealing ring 10 and a sealing ring 12. The sealing ring 12 is fixed to the bottom end of the sealing ring 10 and is engaged in the gap between the seat ring 2 and the positioning slide cylinder 8. The upper end of the sealing ring 10 is fixedly connected with a reinforcing rib ring 13, and the inner wall of the reinforcing rib ring 13 is in contact with the outer wall of the positioning slide cylinder 8. In use, by lifting the sealing mechanism 9 relative to the positioning mechanism 1, the sealing ring 10 in the sealing mechanism 9 is separated from the positioning mechanism 1, and the sealing ring 12 in the sealing mechanism 9 is dislodged from the positioning mechanism 1. Then, the seat ring in the positioning mechanism 1 can be opened. The gap between the positioning cylinder 2 and the positioning slide 8 is filled with isolating particles to form an isolating filling layer 27. Then, the sealing mechanism 9 falls relative to the positioning mechanism 1, so that the sealing ring 10 and the seat ring 2 fit together vertically, and the sealing ring 12 seals the gap between the seat ring 2 and the positioning slide 8, thereby completing the better sealing of the upper part of the isolating filling layer 27. This facilitates the sealing and protection of the upper part of the isolating filling layer 27, and prevents external flying sand from entering the isolating filling layer 27 from the upper part. Among them, the reinforcing rib ring 13 is used to reinforce the upper periphery of the positioning slide 8 by the sealing ring 10, increasing the support area and improving the support strength.

[0041] Reference Figure 1 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 and Figure 12 The lower handle 3 is fixedly connected to the middle of both sides of the seat ring 2, and a limiting recess 24 is opened on the upper side of one side of the lower handle 3. The upper handle 11 is fixedly connected to the middle of both sides of the sealing ring 10, and a limiting pin 25 is fixedly connected to the bottom side of one side of the upper handle 11. The limiting recess 24 and the limiting pin 25 engage with each other. In use, the lower handle 3 and the upper handle 11 facilitate the lifting and placement of the positioning mechanism 1 and the sealing mechanism 9 relative to the wellhead. The upper handle 11, which is separate from the lower handle 3, facilitates the lifting and placement of the sealing mechanism 9 relative to the positioning mechanism 1. Furthermore, the lower handle 3 and the upper handle 11 can connect the sealing mechanism 9 and the positioning mechanism 1 together, making it difficult for the positioning mechanism 1 on the positioning mechanism 1 to rotate and move, so as to facilitate the stable use of the sealing mechanism 9.

[0042] The usage process and working principle of this invention: In use, the positioning mechanism 1 and the sealing mechanism 9, which are interconnected, are moved to the top of the wellhead via the lower handle 3 and the upper handle 11. The limiting insert 6 is then inserted downwards into the wellhead, and the limiting strip 4 is inserted into the loose sandstone formation 26 for reinforcement. This completes the installation of the positioning mechanism 1 and the sealing mechanism 9 relative to the wellhead. Afterwards, the sand control tubing 28 is lowered relative to the positioning slide 8 and the wellhead. During the lowering of the sand control tubing 28… The upper scraper ring 14 and the reinforced scraper head 23 at the end of the upper scraper ring 14 can scrape off the dirt and grime adhering to the outer wall of the sand control string 28 during the lowering process. Furthermore, the rolling balls 17 inside the roller groove 16 facilitate the smooth lowering of the sand control string 28 relative to the positioning mechanism 1. Once the sand control string 28 has been lowered to the predetermined position in the wellhead, the upper handle 11 lifts the sealing ring 10 relative to the seat ring 2, separating the sealing ring 10 from the seat ring 2. Then, the gap between the seat ring 2 and the positioning slide cylinder 8... Insulator particles are filled into the wellhead to form an insulator filling layer 27. After the insulator particles are filled, the sealing ring 10 is lowered relative to the seat ring 2, so that the sealing ring 12 is locked in the gap between the seat ring 2 and the positioning slide cylinder 8, sealing the upper part of the insulator filling layer 27. The limiting pin 25 at the bottom of the upper handle 11 is locked downward into the limiting recess 24 at the upper end of the lower handle 3, limiting the seat ring 2 at the upper end of the positioning mechanism 1, so that the positioning mechanism 1 and the seat ring 2 are connected. The sand control pipe string 28 is not easily rotated. When the pipe is pulled out, the sand control pipe string 28 is easily pulled out by the sand control filling layer 27, which is filled with sand control particles between the sand control pipe string 28 and the positioning mechanism 1. At the same time, the sand control particles adhering to the outer wall of the sand control pipe string 28 can be scraped off by the lower scraper ring 15 at the bottom of the positioning slide 8 and the reinforcing scraper head 23 at the end of the lower scraper ring 15, so as to prevent the sand control pipe string 28 from being adhered to and carried out by the sand control pipe string 28.

[0043] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sand control well completion structure with an easily removable downhole sand control string, comprising a loose sandstone formation (26), a separator filling layer (27), and a sand control string (28), characterized in that: A wellhead is provided inside the loose sandstone stratum (26). A sand control pipe string (28) is installed inside the wellhead, and an isolation filling layer (27) is provided around the sand control pipe string (28) inside the wellhead. A positioning mechanism (1) is provided at the upper end of the wellhead, and a sealing mechanism (9) is provided at the upper end of the positioning mechanism (1). The positioning mechanism (1) includes a seat ring (2), a limiting insert (6), and a positioning slide (8). The bottom end of the seat ring (2) is fixedly connected to the limiting insert (6), and the limiting insert (6) is inserted into the upper end of the wellhead. A positioning slide (8) is provided inside the limiting insert (6). An upper scraper ring (14) is fixedly connected to the upper end of the positioning slide (8), and a lower scraper ring (14) is fixed to the bottom end of the positioning slide (8). The scraper ring (15) is fixedly connected to the ends of the upper scraper ring (14) and the lower scraper ring (15). The positioning slide cylinder (8) has several roller grooves (16) around its interior. The roller grooves (16) are movably connected to the interior of the rollers (17). An oil passage pipe (18) is provided between the upper and lower adjacent roller grooves (16). The positioning slide cylinder (8) has several oil injection pipes (19) around its upper interior. The oil injection pipes (19) are connected to the interior of the oil passage pipes (18). The sealing mechanism (9) includes a sealing ring (10) and a sealing ring (12). The sealing ring (12) is fixed at the bottom end of the sealing ring (10). The sealing ring (12) is stuck in the gap between the seat ring (2) and the positioning slide cylinder (8).

2. The sand control well completion structure with an easily removable downhole sand control string according to claim 1, characterized in that: The lower handle (3) is fixedly connected to the middle of both sides of the seat ring (2), and a limiting recess (24) is opened on the upper side of one side of the lower handle (3). The upper handle (11) is fixedly connected to the middle of both sides of the sealing ring (10), and a limiting pin (25) is fixedly connected to the bottom side of one side of the upper handle (11). The limiting recess (24) and the limiting pin (25) engage with each other.

3. The sand control well completion structure with an easily removable downhole sand control string according to claim 1, characterized in that: The bottom end of the seat ring (2) is fixedly connected with several limiting inserts (4), which are conical in shape and interlock with the loose sandstone stratum (26).

4. The sand control well completion structure with an easily removable downhole sand control tubing string according to claim 3, characterized in that: The bottom end of the seat ring (2) is in contact with the upper end of the loose sandstone stratum (26). A shock-absorbing washer (5) is fixedly connected inside the upper end of the seat ring (2), and the shock-absorbing washer (5) is a rubber component. The bottom end of the sealing ring (10) is in contact with the upper end of the seat ring (2), and the bottom end face of the sealing ring (10) is in elastic contact with the shock-absorbing washer (5).

5. The sand control well completion structure with an easily removable downhole sand control tubing string according to claim 1, characterized in that: A plurality of connecting rods (7) are provided between the limiting insert (6) and the positioning slide (8), and the two ends of the connecting rods (7) are fixedly connected to the inner wall of the limiting insert (6) and the outer wall of the positioning slide (8), respectively.

6. The sand control well completion structure with an easily removable downhole sand control tubing string according to claim 1, characterized in that: The upper scraper ring (14), lower scraper ring (15) and reinforcing scraper head (23) all have triangular cross-sections, and the reinforcing scraper head (23) is a manganese steel component.

7. The sand control well completion structure with an easily removable downhole sand control string according to claim 1, characterized in that: The upper outer wall of the positioning slide (8) is fixedly connected with several connecting strips (20), and a sealing block (21) is fixedly connected to one side of the connecting strip (20). A sealing plug (22) is fixedly connected to the bottom end of the sealing block (21), and the sealing plug (22) is interlocked with the upper end of the oil injection pipe (19).

8. The sand control well completion structure with an easily removable downhole sand control string according to claim 7, characterized in that: Both the connecting strip (20) and the sealing plug (22) are rubber components.

9. The sand control well completion structure with an easily removable downhole sand control string according to claim 1, characterized in that: The upper end of the sealing ring (10) is fixedly connected to a reinforcing rib ring (13), and the inner wall of the reinforcing rib ring (13) is in contact with the outer wall of the positioning slide cylinder (8).

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