Compression type metal seal structure for thermal recovery well

Abstract

The application discloses a compression type metal sealing structure for thermal recovery well, which comprises a center pipe, the upper end of the center pipe is connected with a liquid cylinder spindle, the lower part of the center pipe is connected with a pressure cap, a pressure transmission sleeve is arranged above the pressure cap, a pressure sleeve is arranged above the pressure transmission sleeve, the inner side of the pressure sleeve is connected with the outer wall of the upper end of the center pipe through a lock ring, metal sealing assemblies are arranged between the pressure cap and the pressure transmission sleeve and between the pressure transmission sleeve and the pressure sleeve, a storage cavity of heat-expanding fluid is arranged above the pressure sleeve, a push rod assembly is further arranged in the storage cavity, and the tail end of the push rod assembly is in contact with the upper end of the pressure sleeve. The two groups of metal sealing assemblies and the lock ring locking mechanism can meet the sealing requirements of multiple rounds of steam stimulation operation, the metal sealing assembly does not rub against the inner wall of the wellbore during the process of entering the well, and the metal sealing function is realized when steam injection is carried out in the thermal recovery well.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and in particular to a compression-type metal sealing structure for thermal recovery wells. Background Technology

[0002] In heavy oil extraction, due to differences in reservoir permeability and physical properties, uniform steam injection can easily lead to uneven steam absorption and low utilization rates in some well sections, objectively affecting the improvement of oil recovery. Segmented steam injection can ensure uniform steam absorption in each layer, increase the effective well section length, increase heat utilization, and improve thermal recovery efficiency.

[0003] During the staged steam injection process, high-temperature and high-pressure packing tools need to be installed in the well. Currently, the most commonly used packers in major oilfields are thermosensitive high-temperature packers and metal insertion sealing tools. As the number of steam injection cycles increases, the rubber sleeve of the thermosensitive high-temperature packer gradually ages or loses elasticity, and its effectiveness deteriorates. Conventional metal insertion sealing tools lack expansion compensation during installation, causing friction between their sealing surface and the pipe wall, and the sealing effect cannot be guaranteed. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a compression-type metal sealing structure for thermal recovery wells. This structure, designed for heavy oil wells with staged steam injection, employs a compression-type metal seal, enabling multiple rounds of steam injection and removal operations. This avoids seal failure caused by aging of the heat-sensitive, high-temperature packer sleeve and frictional damage to the sealing surface during metal insertion.

[0005] This application is achieved using the following technical solution.

[0006] A compression-type metal sealing structure for thermal recovery wells includes a central tube, the upper end of which is connected to a hydraulic cylinder spindle; the lower part of the central tube is connected to a pressure cap, a pressure transmission sleeve is provided above the pressure cap, and a pressure sleeve is provided above the pressure transmission sleeve. The inner side of the pressure sleeve is connected to the outer wall of the upper end of the central tube through a locking ring; metal sealing assemblies are provided between the pressure cap and the pressure transmission sleeve, and between the pressure transmission sleeve and the pressure sleeve; a storage chamber for thermally expanding fluid is provided above the pressure sleeve, and a push rod assembly is also provided in the storage chamber, with the tail end of the push rod assembly contacting the upper end of the pressure sleeve.

[0007] Furthermore, the inner wall of the upper end of the central tube is connected to the outer wall of the lower end of the hydraulic cylinder spindle via threads.

[0008] Furthermore, the pressure cap is connected to the central tube by a thread and is secured by an anti-loosening screw.

[0009] Furthermore, the metal sealing assembly includes a bidirectional pressure ring, multiple unidirectional pressure rings, and multiple C-shaped metal rings; the bidirectional pressure ring is located in the center of the metal sealing assembly, and the C-shaped metal rings and unidirectional pressure rings are alternately arranged on both sides of the bidirectional pressure ring.

[0010] Furthermore, the bidirectional pressure ring includes a central body and protrusions on both sides; the unidirectional pressure ring includes a body of 1 / 2 bidirectional pressure ring and a protrusion on one side of the body; the protrusion is inserted into the notch of the C-shaped metal ring.

[0011] Furthermore, the inner and outer sides of the locking ring are connected to the pressure sleeve and the central tube respectively through wedge-shaped threads of different tooth types.

[0012] Furthermore, a cylinder sleeve is fitted over the cylinder spindle, and the lower part of the outer wall of the cylinder spindle extends outward to form a boss; the outer wall of the cylinder spindle, the boss, and the cylinder sleeve form a storage cavity for the fluid that expands when heated.

[0013] Furthermore, the push rod assembly includes a push rod and a metal bellows, one end of which is connected to the push rod and the other end is connected to the boss of the hydraulic cylinder spindle; the lower end of the push rod passes through the boss and contacts the upper end of the pressure sleeve.

[0014] Furthermore, the lower end of the cylinder liner is sealed to the boss of the hydraulic cylinder spindle by a metal O-ring; the upper end of the cylinder liner is sealed to the outer wall of the hydraulic cylinder spindle by a high-temperature resistant sealing ring.

[0015] Furthermore, the upper end of the cylinder liner is provided with an injection hole, and a plug is provided inside the injection hole.

[0016] This application has the following beneficial effects.

[0017] 1. This invention, through two sets of metal sealing components and a locking ring mechanism, can meet the sealing requirements of multiple rounds of steam injection and discharge operations;

[0018] 2. The compression-type metal sealing structure of the present invention does not cause friction between the metal sealing component and the inner wall of the wellbore during the well insertion process, and realizes the function of metal sealing during steam injection in thermal recovery wells. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention;

[0020] Figure 2 This is a schematic diagram showing the state when the present invention achieves its sealing function;

[0021] Figure 3 This is a schematic diagram of the C-shaped metal ring of the present invention;

[0022] Figure 4 This is a schematic diagram of the bidirectional pressure ring of the present invention;

[0023] Figure 5 This is a schematic diagram of the unidirectional pressure ring of the present invention;

[0024] Figure 6 This is a schematic diagram of the push rod assembly of the present invention;

[0025] Figure 7 This is a schematic diagram of the locking ring structure of the present invention;

[0026] Figure 8 This is a schematic diagram of the tooth profiles on both sides of the locking ring of the present invention.

[0027] Among them, 1. central tube; 2. anti-loosening screw; 3. pressure cap; 4. C-shaped metal ring; 5. one-way pressure ring; 6. two-way pressure ring; 7. pressure transmission sleeve; 8. locking ring; 9. pressure sleeve; 10. hydraulic cylinder spindle; 11. metal O-ring; 12. push rod; 13. metal bellows; 14. cylinder liner; 15. heat-expanding fluid; 16. high-temperature resistant sealing ring; 17. plug; 18. sealing cylinder; 19. metal sealing assembly; 20. push rod assembly. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] like Figure 1-8 As shown, a compression-type metal sealing structure for thermal recovery wells includes a central pipe 1, a pressure cap 3, a metal sealing assembly 19, a pressure transmission sleeve 7, a locking ring 8, a pressure sleeve 9, a hydraulic cylinder spindle 10, a push rod assembly 20, and a cylinder liner 14 connected in sequence.

[0030] The upper outer side of the central tube 1 is threaded to the inner side of the locking ring 8, and the upper inner side of the central tube 1 is threaded to the hydraulic cylinder spindle 10. The locking ring 8 is an open C-shaped ring with different wedge-shaped threads on the inner and outer sides. The outer side of the locking ring 8 is threaded to the pressure sleeve 9. The different wedge-shaped threads on the inner and outer sides of the locking ring 8 in this application are all specially made threads. These threads ensure that the locking ring 8 can only move downwards after being pushed, and is locked upwards.

[0031] The pressure cap 3 is threaded to the lower part of the central tube 1 and fixed with anti-loosening screws 2. There is a metal sealing assembly 19 between the pressure cap 3 and the pressure transmission sleeve 7, and between the pressure transmission sleeve 7 and the pressure sleeve 9. The metal sealing assembly 19 consists of a bidirectional pressure ring 6, four unidirectional pressure rings 5, and six C-shaped metal rings 4. The unidirectional pressure rings 5 ​​and C-shaped metal rings 4 are alternately arranged on both sides of the bidirectional pressure ring 6, and the structures on both sides of the bidirectional pressure ring 6 are the same. The bidirectional pressure ring 6 includes a central body (the larger step surface in the axial direction of the pressure ring) and protrusions on both sides. The unidirectional pressure ring 5 includes half of the body of the bidirectional pressure ring 6 and a protrusion on one side of the body (two unidirectional pressure rings 5 ​​are combined to form a bidirectional pressure ring 6). Specifically, taking one side of the bidirectional pressure ring 6 as an example, the protrusion of the bidirectional pressure ring 6 is inserted into the notch of the first C-shaped metal ring 4 until the C-shaped metal ring 4 contacts the body of the bidirectional pressure ring 6; a first unidirectional pressure ring 5 is set on the first C-shaped metal ring 4, the protrusion of the first unidirectional pressure ring 5 is inserted into the notch of the second C-shaped metal ring 4, a second unidirectional pressure ring 5 is set on the second C-shaped metal ring 4, the protrusion of the second unidirectional pressure ring 5 is inserted into the notch of the third C-shaped metal ring 4, and the openings of the three C-shaped metal rings 4 all face the bidirectional pressure ring 6.

[0032] Above the pressure sleeve 9 is a storage cavity for the heat-expanding fluid 15. The storage cavity consists of the side wall of the hydraulic cylinder spindle 10, a boss protruding from the lower part of the hydraulic cylinder spindle 10, and a cylinder sleeve 14. The upper end of the cylinder sleeve 14 is provided with an injection hole, and a plug 17 is provided in the injection hole. The plug 17 seals the heat-expanding fluid 15 in the storage cavity. To improve the sealing performance of the storage cavity, the lower end of the cylinder sleeve 14 is sealed to the boss of the hydraulic cylinder spindle 10 by a metal O-ring 11; the upper end of the cylinder sleeve 14 is sealed to the outer wall of the hydraulic cylinder spindle 10 by a high-temperature resistant sealing ring 16.

[0033] The storage cavity is also equipped with a push rod assembly 20, which moves radially between the hydraulic cylinder spindle 10 and the cylinder sleeve 14. The lower end of the push rod assembly 20 contacts the upper end of the pressure sleeve 9, which can push the pressure sleeve 9 downward. The push rod assembly 20 includes a push rod 12 and a metal bellows 13. The upper end of the metal bellows 13 is welded and sealed to the push rod 12, and the lower end of the metal bellows 13 is welded and sealed to the boss of the hydraulic cylinder spindle 10. The metal bellows 13 contracts when the push rod 12 moves downward, so that the push rod 12 is in a dynamic sealing state.

[0034] The method of using the compression-type metal sealing structure for thermal recovery wells of the present invention includes the following steps:

[0035] 1) Fabricate and install the above-mentioned compression-type metal sealing structure for thermal recovery wells;

[0036] 2) Connect the tubing to the wellhead using a compression-type metal sealing structure;

[0037] 3) The compression-type metal sealing structure for the thermal recovery well is lowered into the sealing cylinder 18;

[0038] 4) Connect the heating tool to the wellhead tubing and perform heating;

[0039] 5) After heating, the C-shaped metal ring 4 in the metal sealing assembly 19 is compressed and comes into contact with the sealing cylinder 18 to form a sealing space and complete the sealing operation.

[0040] Specifically, the process for achieving the function of the metal sealing structure in step 5) is as follows: When the heating tool injects heat, the fluid 15 expands in volume upon heating, pushing the push rod 12 downwards and compressing the metal bellows 13. The push rod 12 pushes the pressure sleeve 9 downwards, and the pressure sleeve 9 drives the locking ring 8 downwards. The pressure sleeve 9 squeezes the metal sealing assembly 19 between the pressure sleeve 9 and the pressure transmission sleeve 7, the metal sealing assembly 19 squeezes the pressure transmission sleeve 7, and the pressure transmission sleeve 7 further squeezes the metal sealing assembly 19 between the pressure transmission sleeve 7 and the pressure cap 3. When the metal sealing assembly 19 is squeezed, the C-shaped metal ring 4 is squeezed by the pressure sleeve 9, the pressure transmission sleeve 7, and the pressure cap 3. Under the action of the unidirectional pressure ring 5 and the bidirectional pressure ring 6, the C-shaped metal ring 4 deforms and contacts the sealing cylinder 18, forming a sealing space and completing the sealing operation. The locking ring 8 has a special thread, which locks in position after the pressure sleeve 9 moves to its maximum displacement, ensuring that the C-shaped metal ring 4 and the sealing cylinder 18 always maintain a sealed contact.

[0041] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A compression-type metal sealing structure for thermal recovery wells, characterized in that: It includes a central tube (1), the upper end of which is connected to the hydraulic cylinder spindle (10); the lower part of the central tube (1) is connected to the pressure cap (3), a pressure transmission sleeve (7) is provided above the pressure cap (3), a pressure sleeve (9) is provided above the pressure transmission sleeve (7), and the inner side of the pressure sleeve (9) is connected to the outer wall of the upper end of the central tube (1) through a locking ring (8); metal sealing components (19) are provided between the pressure cap (3) and the pressure transmission sleeve (7) and between the pressure transmission sleeve (7) and the pressure sleeve (9); a storage chamber for a heat-expanding fluid (15) is provided above the pressure sleeve (9), and a push rod assembly (20) is also provided in the storage chamber, with the tail end of the push rod assembly (20) contacting the upper end of the pressure sleeve (9); The metal sealing assembly (19) includes a bidirectional pressure ring (6), multiple unidirectional pressure rings (5) and multiple C-shaped metal rings (4); the bidirectional pressure ring (6) is located in the center of the metal sealing assembly (19), and the C-shaped metal rings (4) and unidirectional pressure rings (5) are alternately arranged on both sides of the bidirectional pressure ring (6); The bidirectional pressure ring (6) includes a central body and protrusions on both sides; the unidirectional pressure ring (5) includes a body of 1 / 2 bidirectional pressure ring (6) and a protrusion on one side of the body; the protrusion is inserted into the notch of the C-shaped metal ring (4).

2. The compression-type metal sealing structure for thermal recovery wells according to claim 1, characterized in that: The inner wall of the upper end of the central tube (1) is connected to the outer wall of the lower end of the hydraulic cylinder spindle (10) by a thread.

3. The compression-type metal sealing structure for thermal recovery wells according to claim 1, characterized in that: The pressure cap (3) is connected to the central tube (1) by a thread and is fixed by an anti-loosening screw (2).

4. The compression-type metal sealing structure for thermal recovery wells according to claim 1, characterized in that: The inner and outer sides of the locking ring (8) are connected to the pressure sleeve (9) and the central tube (1) respectively through wedge-shaped threads of different tooth types.

5. The compression-type metal sealing structure for thermal recovery wells according to claim 1, characterized in that: The cylinder spindle (10) is fitted with a cylinder sleeve (14), and the lower part of the outer wall of the cylinder spindle (10) extends outward to form a boss; the outer wall of the cylinder spindle (10), the boss, and the cylinder sleeve (14) form a storage cavity for the fluid (15) that expands when heated.

6. The compression-type metal sealing structure for thermal recovery wells according to claim 5, characterized in that: The push rod assembly (20) includes a push rod (12) and a metal bellows (13). One end of the metal bellows (13) is connected to the push rod (12), and the other end is connected to the boss of the hydraulic cylinder spindle (10). The lower end of the push rod (12) passes through the boss and contacts the upper end of the pressure sleeve (9).

7. The compression-type metal sealing structure for thermal recovery wells according to claim 5, characterized in that: The lower end of the cylinder liner (14) is sealed to the boss of the hydraulic cylinder spindle (10) by a metal O-ring (11); the upper end of the cylinder liner (14) is sealed to the outer wall of the hydraulic cylinder spindle (10) by a high-temperature resistant sealing ring (16).

8. A compression-type metal sealing structure for thermal recovery wells according to claim 5, characterized in that: The upper end of the cylinder liner (14) is provided with an injection hole, and a plug (17) is provided in the injection hole.

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