A mixer

Abstract

The present invention discloses a mixer, which comprises a valve body, a core pipe, a valve core, a spring and a support seat; the upper part of the mixer is connected to a double-wall drill pipe, and the lower part is connected to a single-wall drill pipe. When the fluid flows downward through the annular gap A, it pushes the valve core to slide downward to the lower end of the passage F, and the fluid sequentially passes through the annular gap A, the annular gap B above the valve core and the passage F and enters the external space of the mixer; a step A protruding inward is machined in the passage B of the valve body. When the fluid stops flowing downward through the annular gap A, the spring pushes the valve core to move upward. After the upward-sliding valve core contacts the step A, it stops moving. The downward-sliding valve core squeezes the sealing ring C under the combined action of the spring force and the lower fluid pressure. The valve core and its seals C and D are used to isolate the fluid in the annular gap B above the valve core from the passage F. The advantage of the present invention is that the valve core squeezes the sealing ring C under the combined action of the spring and the lower fluid pressure. This kind of pressure-assisted sealing structure can realize the compensation for the wear of the sealing ring, and improves the sealing life and pressure-bearing capacity.

Description

Technical Field

[0001] The present invention relates to a mixer in the field of drilling and production tools, and particularly to a downhole mixer for gas injection drilling with double-wall drill pipes. Background Art

[0002] In recent years, during the drilling process in fields such as geothermal drilling and oil drilling, many wells have been affected by severe lost circulation, which seriously restricts the drilling progress and the formation penetration rate. Lost circulation formation drilling can be solved by using gas injection drilling methods. This technology can be divided into gas injection drilling technology inside the drill pipe, casing parasitic pipe gas injection technology, concentric casing gas injection technology, and double-wall drill pipe gas injection technology from the gas injection process. Among them, the double-wall drill pipe gas injection drilling technology has the following advantages compared with the traditional gas injection drilling technology inside the drill pipe: ① Gas and liquid are injected separately, with higher efficiency and easier control: The optimal wellbore ECD gradient distribution can be obtained and controlled by adjusting various parameters (drilling fluid density, displacement, double-wall drill pipe depth, gas volume, etc.); ② It does not reduce the drilling fluid density and displacement, and better exerts the advantages of downhole speed-up tools; ③ Fewer gas injection equipment is required, with low pressure and good economy; ④ Pure liquid phase can be injected inside the drill pipe to use conventional MWD for directional services. The implementation of the double-wall drill pipe gas injection drilling technology is expected to significantly reduce the problems such as the failure of lost circulation treatment in low-pressure and easy-to-lose circulation formations, and solve the problems of safe and efficient drilling in negative window formations with coexisting lost circulation and collapse, further ensuring the success rate of drilling operations, and having good promotion and application prospects. The main newly added equipment for double-wall drill pipe gas injection drilling includes double-wall drill pipes, gas boxes, and downhole gas-liquid mixers. Among them, the mixer is installed at the bottom of the double-wall drill pipe, and the gas injected into the annulus enters the large annulus between the drill pipe and the wellbore through the mixer, while the mud in the internal passage continues to be injected downward into the single-wall drill pipe. The existing mixer structures are too simple, and the seals are easily worn, resulting in seal failure. Once bottomhole overflow occurs, formation fluids will flow back along the annulus of the double-wall drill pipe, causing safety hazards. Therefore, a downhole mixer with reliable sealing and high reverse pressure-bearing capacity is one of the key components for realizing double-wall drill pipe gas injection drilling. Summary of the Invention

[0003] The purpose of the present invention is to provide a downhole mixer aiming at the problems existing in the prior art, so as to improve the reverse sealing and pressure-bearing capacity of the downhole mixer.

[0004] The upper part of the mixer is connected to the double-wall drill pipe, and the lower part is connected to the single-wall drill pipe. The inside of the single-wall drill pipe is passage D. The double-wall drill pipe includes an outer pipe and an inner pipe. The inner pipe is inserted into the outer pipe to form two flow channels. One is the annulus A between the inner pipe and the outer pipe, and the other is the inner flow channel of the inner pipe, which is passage A.

[0005] The purpose of the present invention is achieved as follows:

[0006] A mixer, comprising a valve body, a core pipe, a valve core, a spring and a support seat; wherein: the valve body is cylindrical, with a connection head for a double-wall drill pipe provided at the upper part of the valve body, a connection head for a single-wall drill pipe provided at the lower part, a through-hole B axially machined inside and penetrating up and down, and channels E and F radially machined at intervals in the middle section of the valve body; the core pipe is circular tubular, inserted into the through-hole B of the valve body, separating the through-hole B into two flow channels, one is the annular gap B between the core pipe and the valve body, and the other is the internal flow channel of the core pipe which is the through-hole C. The upper part of the core pipe and the lower part of the inner pipe of the double-wall drill pipe form a plug-in sealing structure; the valve core is sleeved in the annular gap B between the outside of the core pipe and the valve body, and the inner and outer surfaces of the valve core respectively form an axial sliding sealing fit with the core pipe and the valve body. The upper and lower stroke stop points of the valve core respectively form a closing fit with the channel F and the channel E; the spring is installed in the annular gap B below the valve core, and the lower part of the spring is installed with the support seat; the support seat is installed at the lower part of the annular gap B, and the inner and outer surfaces respectively form a fixed seal with the valve body and the core pipe.

[0007] The above solution further includes:

[0008] The valve core includes an upper pressing cap, an upper sliding valve core and a lower sliding valve core.

[0009] The lower sliding valve core is a stepped cylinder with a "convex" cross-section in the longitudinal direction, with a through-hole A axially machined inside. The smaller outer cylindrical surface at the upper part is the first outer cylindrical surface, and the larger outer cylindrical surface at the lower part is the second outer cylindrical surface. A shoulder A is formed between the first outer cylindrical surface and the second outer cylindrical surface. The through-hole A forms a first inner cylindrical surface. A sealing ring D is installed between the first inner cylindrical surface and the outer surface of the core pipe to form a sliding seal. The second outer cylindrical surface forms a clearance sliding fit with the internal through-hole B of the valve body; the upper sliding valve core is cylindrical, installed on the first outer cylindrical surface of the lower sliding valve core, and the inner cylindrical surface of the upper sliding valve core forms a clearance sliding fit with the first outer cylindrical surface. A sealing ring C is installed between the lower end of the upper sliding valve core and the shoulder A; the upper sliding valve core is axially limited by the upper pressing cap connected to the upper end of the first outer cylindrical surface of the lower sliding valve core.

[0010] The cross-section of the sealing ring C is triangular or trapezoidal; a sealing ring E is installed between the second outer cylindrical surface of the lower sliding valve core and the inner surface of the valve body to form a sliding sealing fit.

[0011] A filter screen is installed in the channel E.

[0012] Sealing rings A and B are installed between the support seat and the valve body and the core pipe respectively.

[0013] The advantage of the present invention is that it adopts a soft sealing form, which has good sealing reliability for both high and low pressure seals; the valve core squeezes the sealing ring under the combined action of the spring and the lower fluid pressure. This kind of pressure-assisted sealing structure can not only achieve high-pressure sealing, but also compensate for the wear of the sealing ring, improving the sealing life. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of a mixer of the present invention in the state where the valve core is closed.

[0015] Figure 2 It is a schematic diagram of a mixer of the present invention in the state where the valve core is open.

[0016] In the figure: 1. Valve body, 2. Core pipe, 3. Valve core, 4. Spring, 5. Filter screen, 6. Support seat, 7. Seal ring A, 8. Seal ring B, 9. Passage E, 10. Passage F, 11. Spline boss, 30. Upper pressing cap, 31. Upper sliding valve core, 32. Seal ring C, 33. Lower sliding valve core, 34. Seal ring D, 35. Seal ring E. Specific embodiments

[0017] The present invention will be further described below with reference to the accompanying drawings:

[0018] Embodiment 1

[0019] A mixer includes a valve body 1, a core pipe 2, a valve core 3, a spring 4 and a support seat 6; wherein: the valve body 1 is cylindrical, the upper part of the valve body 1 is provided with a connector connected to a double-wall drill pipe, the lower part is provided with a connector connected to a single-wall drill pipe, and an axially through hole B is machined inside, and passage E9 and passage F10 are radially machined at intervals in the middle section of the valve body 1; the core pipe 2 is a circular tube, the core pipe 2 is inserted into the hole B of the valve body 1, dividing the hole B into two flow channels, one is the annular gap B between the core pipe 2 and the valve body 1, and the other is the internal flow channel of the core pipe 2 which is the hole C, and the upper part of the core pipe 2 and the lower part of the inner pipe of the double-wall drill pipe form a plug-in sealing structure; the valve core 3 is sleeved in the annular gap B between the outside of the core pipe 2 and the valve body 1, the inner and outer surfaces of the valve core 3 respectively form an axially sliding sealing fit with the core pipe 2 and the valve body 1, and the upper and lower stroke stop points of the valve core 3 respectively form a closing fit with the passage F10 and the passage E9; the spring 4 is installed in the annular gap B below the valve core 3, and the lower part of the spring 4 is installed with the support seat 6; the support seat 6 is installed at the lower part of the annular gap B, and the inner and outer surfaces respectively form a fixed seal with the valve body 1 and the core pipe 2.

[0020] Embodiment 2

[0021] On the basis of Embodiment 1, it further includes:

[0022] The valve core 3 includes an upper pressing cap 30, an upper sliding valve core 31 and a lower sliding valve core 33.

[0023] The lower sliding spool 33 is a stepped cylinder with a "convex" cross-section. A through hole A is axially machined inside. The smaller upper outer cylindrical surface is the first outer cylindrical surface, and the larger lower outer cylindrical surface is the second outer cylindrical surface. A shoulder A is formed between the first outer cylindrical surface and the second outer cylindrical surface. The through hole A forms a first inner cylindrical surface. A sealing ring D34 is installed between the first inner cylindrical surface and the outer surface of the core pipe 2 to form a sliding seal. The second outer cylindrical surface forms a clearance sliding fit with the inner hole B of the valve body 1. The upper sliding spool 31 is cylindrical and is installed on the first outer cylindrical surface of the lower sliding spool 33. A clearance sliding fit is formed between the inner cylindrical surface of the upper sliding spool 31 and the first outer cylindrical surface. A sealing ring C32 is installed between the lower end of the upper sliding spool 31 and the shoulder A. The upper sliding spool 31 is axially limited by an upper pressing cap 30 connected to the upper end of the first outer cylindrical surface of the lower sliding spool 33.

[0024] The cross-section of the sealing ring C32 is triangular or trapezoidal. A sealing ring E35 is installed between the second outer cylindrical surface of the lower sliding spool 33 and the inner surface of the valve body 1 to form a sliding seal fit.

[0025] A filter screen 5 is installed in the passage E9.

[0026] Sealing rings A7 and B8 are installed between the support seat 6 and the valve body 1 and the core pipe 2 respectively.

[0027] Embodiment 3

[0028] Refer to the appendix Figure 1 , A mixer has its upper part connected to a double-wall drill pipe and its lower part connected to a single-wall drill pipe. The inside of the single-wall drill pipe is a passage D. The double-wall drill pipe includes an outer pipe and an inner pipe. The inner pipe is inserted into the outer pipe to form two flow channels. One is the annular gap A between the inner pipe and the outer pipe, and the other is the inner flow channel of the inner pipe which is the passage A.

[0029] A mixer includes a valve body 1, a core pipe 2, a spool 3, a spring 4 and a support seat 6. The valve body 1 is cylindrical, and a vertically connected passage B is axially machined inside. The core pipe 2 is tubular and is inserted into the passage B of the valve body 1, dividing the passage B into two flow channels. One is the annular gap B between the core pipe 2 and the valve body 1, and the other is the inner flow channel of the core pipe 2 which is the passage C. The support seat 6 is tubular and is installed at the lower part of the annular gap B, and sealing rings A7 and B8 are installed between it and the valve body 1 and the core pipe 2 respectively. The upper and lower parts of the valve body 1 are respectively connected to the double-wall drill pipe and the single-wall drill pipe by threads. The lower part of the inner pipe of the double-wall drill pipe and the upper part of the core pipe 2 form a plug-in seal. The annular gap A and the annular gap B are connected to form a first flow channel, and the passages A, C and D are connected to form a second flow channel. The plug-in seal between the inner pipe of the double-wall drill pipe and the core pipe 2, and the sealing rings A7 and B8 isolate the fluid between the first channel and the second channel.

[0030] The valve body 1 is radially machined with a passage E9 and a passage F10. The passage F10 is located above the passage E9. The valve core 3 and the spring 4 are installed in the annular gap B. The lower part of the valve core 3 is installed on the spring 4, and the lower part of the spring 4 is installed on the support seat 6. The valve core 3 includes an upper pressing cap 30, an upper sliding valve core 31, a lower sliding valve core 33, a sealing ring C32 and a sealing ring D34. The lower sliding valve core 33 is a stepped cylinder in the shape of a "convex" character, with a through hole A axially machined inside. The smaller outer cylindrical surface at the upper part is the first outer cylindrical surface, and the larger outer cylindrical surface at the lower part is the second outer cylindrical surface. A shoulder A is formed between the first outer cylindrical surface and the second outer cylindrical surface. The through hole A forms a first inner cylindrical surface. A sealing ring D34 is installed between the first inner cylindrical surface and the outer surface of the core pipe 2. A sliding seal is formed between the lower sliding valve core 33 and the core pipe 2. A sealing ring E35 is installed between the second outer cylindrical surface of the lower sliding valve core 33 and the inner passage B of the valve body 1 to form a sliding seal fit. The upper end of the first outer cylindrical surface is installed with the upper pressing cap 30. The upper sliding valve core 31 is in a cylindrical shape and is installed between the upper pressing cap 30 and the shoulder A. A clearance sliding fit is formed between the inner cylindrical surface of the upper sliding valve core 31 and the first outer cylindrical surface. A sealing ring C32 is installed between the lower end of the upper sliding valve core 31 and the shoulder A.

[0031] Refer to the appendix Figure 2 , when the fluid flows downward from the annular gap A (as shown by the dotted arrow in the appendix Figure 2 ), the fluid pushes the valve core 3 downward to the lower end of the passage F10. The passage F10 connects the inside and outside of the valve body 1. The fluid sequentially passes through the annular gap A, the annular gap B above the valve core, and the passage F10 and enters the external space of the mixer. A stepped A protruding inward is machined in the passage B of the valve body 1. When the fluid stops flowing downward from the annular gap A, refer to the appendix Figure 1 , the spring 4 pushes the valve core 3 upward to the upper end of the passage F10. After the upper sliding valve core 31 contacts the stepped A, it stops moving. The lower sliding valve core 33 squeezes the sealing ring C32 under the combined action of the spring force and the lower fluid pressure. The valve core 3 and its seals C32 and D34 are used to isolate the annular gap B above the valve core from the fluid in the passage F10; the passage E9 is communicated with the annular gap B below the valve core 3 and the external space of the mixer. The cross-section of the sealing ring C32 is trapezoidal, and the cross-section of the sealing ring C32 can also be preferably triangular. A filter screen 5 is installed in the passage E9. When the valve core 3 is in the closed and open states, the diameter of the inner passage B of the valve body 1 that cooperates with the valve core 3 is the same.

[0032] The upper end of the support seat 6 is machined with a boss A. When the valve core 3 is opened, the lower sliding valve core 33 moves downward until it contacts the boss A, and the boss A restricts the further descent of the valve core 3. The upper part of the core pipe 2 is machined with a spline boss for the centering and axial positioning of the core pipe.

[0033] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A mixer, comprising a valve body (1), a core pipe (2), a valve core (3), a spring (4) and a support seat (6); Characterized in that: The valve body (1) is cylindrical. The upper part of the valve body (1) is provided with a double-wall drill pipe connector, and the lower part is provided with a single-wall drill pipe connector. An axially-through hole B is machined inside. In the middle section of the valve body (1), a hole E (9) and a hole F (10) are machined at intervals along the radial direction; The core pipe (2) is tubular. The core pipe (2) is inserted into the hole B of the valve body (1), separating the hole B into two flow channels. One is the annular gap B between the core pipe (2) and the valve body (1), and the other is the internal flow channel of the core pipe (2) which is the hole C. The upper part of the core pipe (2) and the lower part of the inner pipe of the double-wall drill pipe form a plug-in sealing structure; The valve core (3) is sleeved in the annular gap B between the outside of the core pipe (2) and the valve body (1). The inner and outer surfaces of the valve core (3) respectively form an axially sliding sealing fit with the core pipe (2) and the valve body (1). The upper and lower stroke stop points of the valve core (3) respectively form a closing fit with the hole F (10) and the hole E (9); The spring (4) is installed in the annular gap B below the valve core (3), and the lower part of the spring (4) is installed with the support seat (6); The support seat (6) is installed at the lower part of the annular gap B, and its inner and outer surfaces respectively form a fixed seal with the valve body (1) and the core pipe (2); The valve core (3) includes an upper pressing cap (30), an upper sliding valve core (31), and a lower sliding valve core (33); The lower sliding valve core (33) is a stepped cylinder with a convex-shaped longitudinal section. A through hole A is axially machined inside. The smaller outer cylindrical surface in the upper part is the first outer cylindrical surface, and the larger outer cylindrical surface in the lower part is the second outer cylindrical surface. A shoulder A is formed between the first outer cylindrical surface and the second outer cylindrical surface. The through hole A forms a first inner cylindrical surface. A sealing ring D (34) is installed between the first inner cylindrical surface and the outer surface of the core pipe (2) to form a sliding seal. The second outer cylindrical surface forms a clearance sliding fit with the inner hole B of the valve body (1); The upper sliding valve core (31) is cylindrical and is installed on the first outer cylindrical surface of the lower sliding valve core (33). The inner cylindrical surface of the upper sliding valve core (31) forms a clearance sliding fit with the first outer cylindrical surface. A sealing ring C (32) is installed between the lower end of the upper sliding valve core (31) and the shoulder A; The upper sliding valve core (31) is axially limited by the upper pressing cap (30) connected to the upper end of the first outer cylindrical surface of the lower sliding valve core (33).

2. A mixer according to claim 1, Characterized in that: The cross section of the sealing ring C (32) is triangular or trapezoidal; A sealing ring E (35) is installed between the second outer cylindrical surface of the lower sliding valve core (33) and the inner surface of the valve body (1) to form a sliding sealing fit.

3. A mixer according to any one of claims 1-2, Characterized in that: A filter screen (5) is installed in the hole E (9).

4. A mixer according to claim 3, Characterized in that: Sealing rings A (7) and B (8) are installed between the support seat (6) and the valve body (1) and the core pipe (2) respectively.

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