CN114382437B

CN114382437B - Backflow preventer

Info

Publication number: CN114382437B
Application number: CN202011133475.XA
Authority: CN
Inventors: 柳进; 韩冬; 秦玉江; 任宪忠; 刘津铭; 吕楠; 骆扬; 陈敏华; 郭立娜; 张铁铭; 张昕冉; 鲍旭光; 曾艳春; 戴运才; 朱高磊; 刘平全; 黄辉建; 罗欢; 任海阳; 李洋
Original assignee: China National Petroleum Corp; CNPC Great Wall Drilling Co
Current assignee: China National Petroleum Corp; CNPC Great Wall Drilling Co
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2024-04-30
Anticipated expiration: 2040-10-21
Also published as: CN114382437A

Abstract

The disclosure provides a backflow preventer, which belongs to the technical field of well cementation, and comprises an outer shell and a backflow one-way valve assembly; the reverse flow check valve assembly comprises a valve body, a valve core, an elastic piece and a positioning piece, wherein the valve body is arranged in the outer shell, a reverse flow cavity is formed in the valve body, a first opening is formed in one end of the valve body, a first end plate is arranged at the other end of the valve body, a reverse flow hole and an inserting hole are formed in the first end plate, the reverse flow hole is communicated with the reverse flow cavity, the valve core is inserted into the inserting hole, the first end of the valve core is used for communicating or blocking the reverse flow cavity and the first opening, a first clamping groove is formed in the position, close to the second end, of the outer side wall of the valve core, the first end plate is provided with a second clamping groove, the second clamping groove and the first clamping groove are oppositely arranged in the moving direction of the valve core, the elastic piece is compressed between the valve core and the first end plate, the compressing direction of the elastic piece is identical to the moving direction of the valve core, and the elastic piece is used for clamping the positioning piece between the first clamping groove and the second clamping groove. The method can simplify the construction steps and save the construction time.

Description

Backflow preventer

Technical Field

The disclosure belongs to the technical field of well cementation, and particularly relates to a backflow preventer.

Background

In the oil gas development process, after the well drilling reaches a target layer, tail pipe descending operation is performed, and well cementation operation is performed through the tail pipe, so that the subsequent construction difficulty and the construction cost can be reduced.

In the related art, after the tail pipe is lowered to a specified position, the tail pipe is pressed down by throwing a ball, so that the hanger is hung on a hanger, and the tail pipe is fixed on a sleeve. After the tail pipe is fixed, cement slurry is pumped to the tail pipe through the ground well cementation equipment, and in order to avoid the accident of plug retention in the pipe caused by the cement slurry flowing back into the tail pipe, a floating hoop is usually arranged at the end part of the tail pipe.

However, because the float collar acts like a one-way valve, only fluid is allowed to flow out of the tail pipe, but not flow into the tail pipe, in the process of discharging the tail pipe, the tail pipe is a cavity, well head grouting operation is needed to balance the internal and external pressure difference of the tail pipe, the construction steps are complicated, and long construction time is needed.

Disclosure of Invention

The embodiment of the disclosure provides a backflow preventer, which can simplify construction steps and save construction time. The technical scheme is as follows:

the embodiment of the disclosure provides a backflow preventer, which comprises an outer shell and a backflow check valve assembly;

The one-way valve assembly comprises a valve body, a valve core, an elastic piece and a positioning piece, wherein the valve body is arranged in the outer shell and is connected with the outer shell, a backflow cavity is arranged in the valve body, one end of the valve body is provided with a first opening, the other end of the valve body is provided with a first end plate, the first end plate is provided with a backflow hole and an inserting hole, the backflow hole is communicated with the backflow cavity, the valve core is movably inserted into the inserting hole, the first end of the valve core is arranged in the backflow cavity and is used for communicating or blocking the backflow cavity with the first opening, the second end of the valve core is arranged outside the valve body, a first clamping groove is formed in the position, close to the second end, of the outer side wall of the valve core, and is away from the backflow cavity, a second clamping groove is formed in one side of the first end plate, the second clamping groove is arranged at the edge of the inserting hole, the second clamping groove and the first clamping groove are oppositely arranged in the moving direction of the valve core, the elastic piece is compressed between the first clamping plate and the first clamping groove, and the elastic piece is arranged in the same direction between the first clamping groove and the first clamping groove.

In one implementation of the disclosure, the positioning piece is a spherical structural piece, the first clamping groove is annular, the axis is parallel to the moving direction of the valve core, the radial joint surface of the first clamping groove is semicircular, the second clamping groove is annular, the axis is parallel to the moving direction of the valve core, the radial section of the second clamping groove is a sector with a central angle of 9 degrees, and the spherical center of the positioning piece, the central angle of the first clamping groove and the central angle of the second clamping groove are clamped between the first clamping groove and the second clamping groove to coincide.

In another implementation of the present disclosure, the valve core includes a core body and a valve stem, the core body is connected to a first end of the valve stem, a portion of an outer contour of the core body facing the first opening matches an inner contour of the first opening, and the elastic member is compressed between a portion of the core body facing the valve stem and the first end plate.

In yet another implementation of the disclosure, the valve core further includes a first limiting table, the first limiting table is located at an included angle between the core body and the valve rod, a second limiting table is disposed on one side of the first end plate facing the backflow cavity, one end of the elastic member is sleeved on the first limiting table, and the other end of the elastic member is sleeved on the second limiting table.

In yet another implementation of the disclosure, the backflow preventer further includes a pressure-holding shut-in assembly and an isolation cylinder;

the pressure-holding well closing assembly comprises an inner shell, a pressure-holding seat and a well closing barrel, wherein the inner shell is positioned in the outer shell and is connected with the outer shell, one end of the inner shell is provided with a second opening, the other end of the inner shell is provided with a second end plate, the position, close to the second end plate, of the side wall of the inner shell is provided with an overflow hole, the pressure-holding seat is movably inserted in the inner shell, the pressure-holding seat is internally provided with a pressure-holding channel, the first end of the pressure-holding channel is used for being in sealing contact with a pressure-holding ball, when the pressure-holding seat is connected with the inner shell through a first shear pin, the second end of the pressure-holding channel is communicated with the first opening through the overflow hole, the first end of the well closing barrel is positioned outside the inner shell, and the second end of the well closing barrel is movably inserted in the inner shell through the second opening and is connected with the first end of the pressure-holding channel through the second shear pin;

the isolation cylinder is positioned in the outer shell, one end of the isolation cylinder is abutted against the inner shell, and the other end of the isolation cylinder is abutted against the valve body, so that the second end plate and the first opening are mutually spaced.

In yet another implementation of the disclosure, a side of the hold-down seat facing away from the second end plate has a cartridge table for being inserted into the second end of the shut-in shaft.

In yet another implementation of the present disclosure, the hold-down channel includes a tapered mouth, a first channel, and a second channel;

the conical opening is positioned in the inserting table and is used for being in sealing contact with the pressure-holding ball;

one end of the first channel is communicated with one end of the conical opening, which is smaller in inner diameter, and the other end of the first channel extends towards the second end plate;

One end of the second channel is communicated with the first channel, and the other end of the second channel extends towards the overflow hole.

In yet another implementation of the present disclosure, the inner sidewall of the inner housing has a plurality of backstop barbs, each of the backstop barbs being sequentially arranged along the direction of movement of the shut-in shaft, the outer sidewall of the shut-in shaft having an elastic backstop block compressed between the outer sidewall of the shut-in shaft and the inner sidewall of the inner housing.

In yet another implementation of the present disclosure, an outer side wall of the inner housing has an outer flange near an end of the second opening, an outer edge of the outer flange being connected to the outer housing, a side of the outer flange facing the second end plate being abutted against the isolation cylinder.

In yet another implementation of the present disclosure, the first end of the shut-in shaft has a bump-in seat protruding from an outer sidewall of the shut-in shaft in a radial direction of the shut-in shaft.

The technical scheme provided by the embodiment of the disclosure has the beneficial effects that:

When the backflow preventer provided by the embodiment of the disclosure is configured on the tail pipe, the outer shell is connected with the tail pipe. In the process that the backflow preventer goes down the well along with the tail pipe, the first clamping groove and the second clamping groove clamp the positioning piece under the action of the elastic piece so as to limit the valve core to move towards the first opening, and a gap exists between the valve core and the first opening. Because a gap exists between the valve core and the first opening, drilling fluid in the drilling well can flow into the backward flowing cavity through the backward flowing cavity Kong Daoguan and flow into the tail pipe through the gap, so grouting operation for balancing the internal and external pressure difference of the tail pipe is not needed.

After the tailpipe is lowered to a designated position, a pumping cycle of the surface cementing apparatus is started such that the valve spool is subjected to an activation pulse to move a distance away from the first opening and compress the resilient member. In the moving process of the valve core, the first clamping groove and the second clamping groove release the clamping of the positioning piece, so that the positioning piece falls off under the action of gravity, namely the restriction of the valve core moving towards the first opening is released, the reverse flow check valve assembly can have the function of a check valve, and only fluid is allowed to flow out of the drilling well from the reverse flow check valve assembly, but fluid is not allowed to flow into the reverse flow check valve assembly from the drilling well.

That is, in the process of the tail pipe going down the well, the backward flow check valve assembly can not only allow fluid to flow out of the well from the backward flow check valve assembly, but also allow fluid to flow into the backward flow check valve assembly from the well, so that drilling fluid in the well can flow into the tail pipe through the backward flow check valve assembly, the influence of internal and external pressure difference on the tail pipe can be reduced, and the tail pipe can be smoothly run down the well. After the tail pipe is in the well, the backward flow one-way valve assembly only allows the fluid to flow out of the drilling well through the backward flow one-way valve assembly, but does not allow the fluid to flow into the backward flow one-way valve assembly through the drilling well, so that the cement paste can be prevented from flowing back into the tail pipe, and the accident of plug remaining in the pipe is avoided.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings may be obtained according to these drawings without inventive effort for a person of ordinary skill in the art.

FIG. 1 is a cross-sectional view of a backflow preventer provided by an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of a reverse flow check valve assembly provided in an embodiment of the present disclosure in a reverse flow condition;

FIG. 3 is a cross-sectional view of a reverse flow check valve assembly provided in an embodiment of the present disclosure in a check valve state;

FIG. 4 is an enlarged view of a portion of FIG. 2 provided by an embodiment of the present disclosure;

Fig. 5 is a cross-sectional view of a downhole state of a pressure hold shut-in assembly provided by an embodiment of the present disclosure;

fig. 6 is a cross-sectional view of a pressure hold state of a pressure hold shut-in assembly according to an embodiment of the present disclosure;

Fig. 7 is a cross-sectional view of a slurry replacing state of a pressure holding shut-in assembly provided by an embodiment of the present disclosure;

fig. 8 is a cross-sectional view of a shut-in state of a pressure build shut-in assembly provided by an embodiment of the present disclosure;

fig. 9 is a partial enlarged view at B of fig. 5 provided by an embodiment of the present disclosure.

The symbols in the drawings are as follows:

1. An outer housing; 2. a reverse flow check valve assembly; 21. a valve body; 211. a back-flowing cavity; 212. a first opening; 213. a first end plate; 2131. the second limiting table; 214. a back-flowing hole; 215. a plug-in hole; 216. a second clamping groove; 217. a first valve body; 218. a second valve body; 22. a valve core; 221. a first clamping groove; 222. a core; 223. a valve stem; 224. a first limit table; 23. an elastic member; 24. a positioning piece; 3. a pressure-building well closing assembly; 31. an inner housing; 311. a second opening; 312. a second end plate; 313. an overflow hole; 314. an outer flange; 315. backstop pawl; 32. a pressure holding seat; 321. a pressure holding channel; 3211. a conical mouth; 3212. a first channel; 3213. a second channel; 322. a cartridge table; 33. closing a shaft; 331. a pressing seat; 332. an elastic stop block; 34. a first shear pin; 35. a second shear pin; 4. an isolation cylinder; 100. pressing and throwing the ball.

Detailed Description

For the purposes of clarity, technical solutions and advantages of the present disclosure, the following further details the embodiments of the present disclosure with reference to the accompanying drawings.

The well cementation operation is a conventional construction step in the oil gas development process, and can effectively reduce the construction difficulty and the construction cost of oil gas development. Since the cementing operation needs to be performed on a liner basis, a liner running operation is required before the cementing operation is performed.

To solve the above-mentioned technical problems, an embodiment of the present disclosure provides a backflow preventer, which includes an outer case 1 and a backflow preventing check valve assembly 2, as shown in fig. 1.

Fig. 2 is a cross-sectional view of the reverse flow check valve assembly 2 in a reverse flow state, and in combination with fig. 2, the reverse flow check valve assembly 2 includes a valve body 21, a valve core 22, an elastic member 23 and a positioning member 24, the valve body 21 is located in the outer housing 1 and is connected with the outer housing 1, the valve body 21 is internally provided with a reverse flow cavity 211, one end of the valve body 21 is provided with a first opening 212, the other end is provided with a first end plate 213, the first end plate 213 is provided with a reverse flow hole 214 and an inserting hole 215, the reverse flow hole 214 is communicated with the reverse flow cavity 211, the valve core 22 is movably inserted in the inserting hole 215, a first end of the valve core 22 is located in the reverse flow cavity 211 and is used for communicating or blocking the reverse flow cavity 211 with the first opening 212, a second end is located outside the valve body 21, a position of an outer side wall of the valve core 22 close to the second end of the valve body is provided with a first clamping groove 221, one side of the first end plate 213 is provided with a second clamping groove 216, the second clamping groove 216 is located at an edge of the inserting hole 215, the second clamping groove 216 and the first clamping groove 221 is arranged in a direction opposite to the first clamping groove 22, the direction of the first clamping groove 23 and the elastic member 23 is compressed between the valve core 23 and the first end 23 and the elastic member 23 in a direction identical.

When the backflow preventer provided by the embodiment of the present disclosure is disposed on the tail pipe, the outer case 1 is connected to the tail pipe (not shown). With continued reference to fig. 2, during the running of the backflow preventer along with the tailpipe, the first clamping groove 221 and the second clamping groove 216 clamp the positioning member 24 under the action of the elastic member 23, so as to limit the movement of the valve core 22 toward the first opening 212, so that a gap exists between the valve core 22 and the first opening 212. Since a gap exists between the spool 22 and the first opening 212, the drilling fluid in the drilling can be poured into the pouring cavity 211 through the pouring hole 214 and poured into the tail pipe through the gap, so that a grouting operation for balancing the internal and external pressure difference of the tail pipe is not required.

Fig. 3 is a cross-sectional view of the reverse flow check valve assembly 2 in a check valve configuration, in conjunction with fig. 3, after the liner has been lowered to a designated position, the pumping cycle of the surface cementing equipment is turned on such that the spool 22 is subjected to an activation pulse to move a small distance away from the first opening 212 and compress the resilient member 23. During the movement of the valve core 22, the first clamping groove 221 and the second clamping groove 216 release the clamping of the positioning piece 24, so that the positioning piece 24 falls off under the action of gravity, that is, the restriction of the movement of the valve core 22 towards the first opening 212 is released, so that the backflow check valve assembly 2 can have the function of a check valve, and only fluid is allowed to flow out of the well from the backflow check valve assembly 2, but fluid is not allowed to flow into the backflow check valve assembly 2 from the well.

That is, in the process of the tail pipe going down the well, the reverse flow check valve assembly 2 can allow fluid to flow out of the well from the reverse flow check valve assembly 2, and also can allow fluid to flow into the reverse flow check valve assembly 2 from the well, so that drilling fluid in the well can flow into the tail pipe through the reverse flow check valve assembly 2, the influence of internal and external pressure difference on the tail pipe can be reduced, and the tail pipe can be smoothly going down the well. After the tail pipe is put into the well, the backward flow one-way valve assembly 2 only allows fluid to flow out of the well drilling from the backward flow one-way valve assembly 2, but does not allow fluid to flow into the backward flow one-way valve assembly 2 from the well drilling, so that cement paste can be prevented from flowing back into the tail pipe, and a plug accident in the pipe is avoided.

From the foregoing, the reverse flow check valve assembly 2 plays a key role in smooth running of the tail pipe, and the description of the reverse flow check valve assembly 2 is continued.

Fig. 4 is a partial enlarged view of fig. 2 at a, and in order to clearly show the relationship between the first slot 221, the second slot 216 and the positioning member 24, the gap between the three is enlarged in fig. 4, and the three are actually in close contact under the action of the elastic member 23.

Referring to fig. 4, in the present embodiment, the positioning member 24 is a spherical structural member, the first clamping groove 221 is annular, the axis is parallel to the moving direction of the valve core 22, the radial joint surface of the first clamping groove 221 is semicircular, the second clamping groove 216 is annular, the moving direction of the axial valve core 22 is parallel, the radial section of the second clamping groove 216 is a sector with a central angle of 90 °, and the center of sphere of the positioning member 24 sandwiched between the first clamping groove 221 and the second clamping groove 216, the central angle of the first clamping groove 221 and the central angle of the second clamping groove 216 coincide.

When the first and second clamping grooves 221 and 216 clamp the positioning member 24 together, the first and second clamping grooves 221 and 216 together form an annular clamping space. Since the radial section of the second clamping groove 216 is a sector with a central angle of 90 °, the clamping space is a sector with a central angle of 270 ° in the radial section of the clamping space, so that a sector gap with a central angle of 90 ° can be reserved in the clamping space, so that the positioning piece 24 can move along with the valve core 22 away from the backflow cavity 211. During the process of assembling the positioning member 24, the valve core 22 is driven to move away from the backflow cavity 211 to compress the elastic member 23, so that the first clamping groove 221 is located outside the valve body 21. Then, the positioning piece 24 is placed in the first clamping groove 221, the valve core 22 is loosened, the valve core 22 drives the second clamping groove 216 to move towards the first clamping groove 221 under the action of the elastic piece 23, and finally, the positioning piece 24 is clamped through the first clamping groove 221 and the second clamping groove 216 under the action of the elastic piece 23, so that the assembly of the positioning piece 24 is completed.

Referring again to fig. 2, in the present embodiment, the valve body 21 includes a first valve body 217 and a second valve body 218, and the first valve body 217 and the second valve body 218 are screwed together and are inserted with pins. The first opening 212 is located in the first valve body 217, and the outer sidewall of the outer housing 1 is screw-coupled to the outer sidewall of the first valve body 217. The spool 22 is movably inserted on the second valve body 218.

In the present embodiment, the valve core 22 includes a core body 222 and a valve rod 223, the core body 222 is connected to a first end of the valve rod 223, a portion of the core body 222 facing the first opening 212 has an outer contour matching an inner contour of the first opening 212, and the elastic member 23 is compressed between a portion of the core body 222 facing the valve rod 223 and the first end plate 213.

In the above implementation, the core 222 is configured to cooperate with the first opening 212 to communicate or block the backflow cavity 211 from the first opening 212. It is easy to understand that when the core 222 is pressed against the first opening 212 by the elastic member 23, the core 222 blocks the backflow cavity 211 from the first opening 212; when the core 222 is biased away from the first opening 212 by the pressure of the fluid, the backflow cavity 211 communicates with the first opening 212. A valve stem 223 is movably inserted within the insertion bore 215 for providing a mounting base for the core 222 such that the core 222 is movable relative to the valve body 21.

Illustratively, the end of the first opening 212 facing the core 222 is tapered, and then the portion of the corresponding core 222 facing the first opening 212 is also tapered, so that the core 222 and the first opening 212 can be matched, and thus effective sealing of the core 222 to the first opening 212 is ensured.

Optionally, the outer wall of the core 222 is coated with an anti-corrosion coating to prevent corrosion of the core 222 and to avoid failure of the seal of the core 222 to the first opening 212.

During the movement of the spool 22, the elastic member 23 expands and contracts accordingly. In order to avoid unnecessary shake of the elastic member 23 caused by uncertainty in the middle position, in this embodiment, the valve core 22 further includes a first limiting table 224, the first limiting table 224 is located at an included angle between the core 222 and the valve rod 223, one side of the first end plate 213 facing the backflow cavity 211 has a second limiting table 2131, one end of the elastic member 23 is sleeved on the first limiting table 224, and the other end of the elastic member 23 is sleeved on the second limiting table 2131.

That is, the two ends of the elastic member 23 are respectively sleeved on the first limiting platform 224 and the second limiting platform 2131, and the first limiting platform 224 and the second limiting platform 2131 can play a role in limiting the elastic member 23, so that the elastic member 23 stretches and contracts between the first limiting platform 224 and the second limiting platform 2131 all the time.

Optionally, the elastic member 23 is a coil spring, the first limiting platform 224 and the second limiting platform 2131 are cylindrical structural members, the first limiting platform 224 and the second limiting platform 2131 are coaxially arranged with the valve rod 223, the coil spring is sleeved on the valve rod 223, and two ends of the coil spring are respectively sleeved on the first limiting platform 224 and the second limiting platform 2131, so that limiting on the coil spring can be achieved.

Illustratively, the core 222, the valve rod 223, and the first stop 224 are integrally formed, thereby improving the structural integrity of the spool 22, improving the manufacturing efficiency of the spool 22, and reducing the manufacturing cost.

Referring to fig. 1 again, in order to thoroughly avoid cement paste from flowing back into the tail pipe after the completion of the well, the backflow preventer further comprises a pressure-holding shut-in assembly 3 and an isolation cylinder 4.

Fig. 5 is a cross-sectional view of a downhole state of the pressure-holding well closing assembly, and in combination with fig. 5, the pressure-holding well closing assembly 3 includes an inner housing 31, a pressure-holding seat 32 and a well closing shaft 33, the pressure-holding well closing assembly 3 includes the inner housing 31, the pressure-holding seat 32 and the well closing shaft 33, the inner housing 31 is located in the outer housing 1 and is connected with the outer housing 1, one end of the inner housing 31 has a second opening 311, the other end has a second end plate 312, a position of a side wall of the inner housing 31 close to the second end plate 312 is provided with an overflow hole 313, the pressure-holding seat 32 is movably inserted in the inner housing 31, the pressure-holding seat 32 is internally provided with a pressure-holding channel 321, a first end of the pressure-holding channel 321 is used for being in sealing contact with the pressure-holding projection 100, when the pressure-holding seat 32 and the inner housing 31 are connected through the first shear pin 34, a second end of the well closing shaft 33 is located outside the inner housing 31 through the overflow hole 313, a second end of the well closing shaft 33 is movably inserted in the inner housing 31 through the second opening 311, the first end of the inner housing 31 is connected with the first end of the first end 212, the first end of the inner housing 21 is separated from the second end 21, and the other end of the inner housing 21 is connected with the first end 1 through the second end is separated from the first end of the first end.

In the process that the backflow preventer is lowered into the well along with the tail pipe, the pressure holding seat 32 is connected with the inner shell 31 through the first shear pin 34, and the well closing shaft 33 is connected with the inner shell 31 through the second shear pin 35. In this state, the shut-in shaft 33, the pressure-holding channel 321, the overflow hole 313 and the first opening 212 are sequentially communicated, and the drilling fluid in the drilling well can sequentially enter the tail pipe through the backflow check valve assembly 2 and the pressure-holding shut-in shaft assembly 3. After the reverse flow check valve assembly 2 is converted into the check valve state, the pressure-holding ball 100 is put into the tail pipe, so that the pressure-holding ball 100 is in sealing contact with the first end of the pressure-holding channel 321 (see fig. 6). At this time, the closing hole 33 and the pressure-holding channel 321 are blocked, and the pressure-holding channel 321 starts to hold pressure above (towards the wellhead direction), so that the hanger is hung. As the pressure is increased, the pressure acting on the pressure holding seat 32 gradually increases, the pressure holding seat 32 shears the first shear pin 34 and moves towards the second end plate 312, and the well closing hole 33 is directly communicated with the overflow hole 313 (see fig. 7), so that cement slurry and displacement fluid can enter the bottom of the well through the pressure holding well closing assembly 3 and the backflow check valve assembly 2 in sequence, and thus circulation operation and slurry replacement operation are performed. After the circulation operation and the slurry replacement operation are completed, the cementing plug is released, so that the cementing plug is in collision with the first end of the well closing shaft 33, the well closing shaft 33 shears the second shear pin 35 and moves towards the pressure holding seat 32 along with the gradual increase of the pressure acting on the well closing shaft 33, and the side wall of the well closing shaft 33 blocks the overflow hole 313 (see fig. 8), so that the fluid in the well is thoroughly blocked from returning to the inside of the tail pipe.

That is, the well closing assembly 3 can not influence the normal operation of the backflow check valve assembly 2, and can also play roles in pressure holding and well closing.

Besides, the isolation cylinder 4 is arranged between the backflow check valve assembly 2 and the pressure-holding well closing assembly 3, so that the backflow check valve assembly 2 and the pressure-holding well closing assembly 3 can be separated from each other, the backflow check valve assembly 2 and the pressure-holding well closing assembly 3 cannot be interfered with each other, and normal circulation of fluid in the backflow preventer is guaranteed.

Referring again to fig. 5, in this embodiment, the side of the hold-down seat 32 facing away from the second end plate 312 has a mounting stand 322, and the mounting stand 322 is configured to be inserted into the second end of the shutter bore 33.

The plug-in board 322 is used for ensuring the assembly stability between the closing shaft 33 and the pressure holding seat 32 when the first shear pin 34 and the second shear pin 35 are not sheared and when the first shear pin 34 and the second shear pin 35 are sheared, so that unnecessary shaking between the closing shaft 33 and the pressure holding seat 32 is avoided.

Illustratively, the mounting block 322 is a cylindrical structural member with the outer peripheral wall of the mounting block 322 in sliding contact with the inner peripheral wall of the well bore 33.

Optionally, the pressure holding channel 321 includes a tapered opening 3211, a first channel 3212 and a second channel 3213, where the tapered opening 3211 is located in the plug-in platform 322 and is used for being in sealing contact with the pressure holding ball 100, one end of the first channel 3212 is communicated with one end with a smaller inner diameter of the tapered opening 3211, the other end of the first channel 3212 extends toward the second end plate 312, one end of the second channel 3213 is communicated with the first channel 3212, and the other end of the second channel 3213 extends toward the overflow hole 313.

In the above implementation manner, the tapered opening 3211 is used for accommodating the pressure-building ball 100, and since the plugging stage 322 is plugged into the well bore 33, the pressure-building ball 100 can accurately fall into the tapered opening 3211 to block the well bore 33 and the pressure-building channel 321. The first and second channels 3212 and 3213 serve as channels providing communication between the tapered mouth 3211 and the overflow aperture 313.

Illustratively, the first passageway 3212 is coaxial with the tapered mouth 3211, which enables better fluid communication between the first passageway 3212 and the tapered mouth 3211. The second channel 3213 is perpendicular to the first channel 3212, and when the pressure holding seat 32 is connected to the inner housing 31 through the first shear pin 34, the second channel 3213 is coaxial with the overflow hole 313, so that fluid can be better communicated between the second channel 3213 and the overflow hole 313.

With continued reference to fig. 5, in this embodiment, the outer side wall of the inner case 31 near the end of the second opening 311 has an outer flange 314, the outer edge of the outer flange 314 is connected to the outer case 1, and the side of the outer flange 314 facing the second end plate 312 abuts against the isolation cylinder 4.

Optionally, the outer edge of the outer flange 314 is threaded with the inner sidewall of the outer housing 1, thereby enabling disassembly and assembly between the inner housing 31 and the outer housing 1. Further, since the outer flange 314 protrudes from the outer side wall of the inner case 31 in the radial direction of the inner case 31, the outer side wall of the inner case 31 does not directly come into contact with the inner side wall of the outer case 1. In this way, space can be provided for the fluid flow through the flow hole 313 to ensure the normal flow of the fluid.

In this embodiment, the first end of the well bore 33 has a pressing seat 331, the pressing seat 331 protrudes from the outer side wall of the well bore 33 along the radial direction of the well bore 33, and the pressing seat 331 is used for propping against the well cementing rubber plug and bearing the pressure applied by the well cementing rubber plug. Since the impact seat 331 protrudes from the outer sidewall of the well bore 33 in the radial direction of the well bore 33, the contact area between the well bore 33 and the well cementing plug is increased, so that impact energy can be stably generated.

Fig. 9 is a partial enlarged view of fig. 5B, and in connection with fig. 9, in this embodiment, the inner side wall of the inner housing 31 has a plurality of retaining barbs 315, each retaining barb 315 is sequentially arranged along the moving direction of the shutter shaft 33, the outer side wall of the shutter shaft 33 has an elastic retaining block 332, and the elastic retaining block 332 is compressed between the outer side wall of the shutter shaft 33 and the inner side wall of the inner housing 31.

Through the cooperation between the backstop pawl 315 and the elastic backstop piece 332, can avoid closing pit shaft 33 and deviate from second end plate 312 and remove, guaranteed closing pit shaft 33 and can remain blocking all the time after blocking the overflow hole 313, improved the reliability of preventing the backflow ware.

Illustratively, the backstop pawl 315 includes a bevel surface that is inclined with respect to the axis of the inner housing 31 and faces the second opening 311, and a perpendicular surface that is perpendicular with respect to the axis of the inner housing 31 and faces the second end plate 312. The elastic stopper 332 is pressed and compressed by the inclined surface when moving toward the second end plate 312 with respect to the inner case 31, and can pass through normally. While the resilient stop 332 has a tendency to move away from the second end plate 312, the vertical plane will block the resilient stop 332, i.e., block the wellbore 33 from moving away from the second end plate 312.

The foregoing description of the preferred embodiments of the present disclosure is provided for the purpose of illustration only, and is not intended to limit the disclosure to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, alternatives, and alternatives falling within the spirit and principles of the disclosure.

Claims

1. The backflow preventer is characterized by comprising an outer shell (1), a backflow one-way valve assembly (2), a pressure-holding shut-in assembly (3) and an isolation cylinder (4);

The reverse flow check valve assembly (2) comprises a valve body (21), a valve core (22), an elastic piece (23) and a positioning piece (24), wherein the valve body (21) is positioned in the outer shell (1) and is connected with the outer shell (1), the valve body (21) is internally provided with a reverse flow cavity (211), one end of the valve body (21) is provided with a first opening (212), the other end of the valve body is provided with a first end plate (213), the first end plate (213) is provided with a reverse flow hole (214) and a plug-in hole (215), the reverse flow hole (214) is communicated with the reverse flow cavity (211), the first end of the valve core (22) is positioned in the reverse flow cavity (211) and is used for communicating or blocking the reverse flow cavity (211) with the first opening (212), the second end of the valve body (21) is positioned outside the valve body (21), the outer side wall of the valve core (22) is close to the second end plate (213) and is provided with a reverse flow hole (214) and a plug-in hole (215), the first end plate (216) is provided with a reverse flow groove (216) and a second end plate (221) is arranged on the opposite side of the second end plate (216) and the second end plate (216) is provided with a reverse flow groove (221), the elastic piece (23) is compressed between the valve core (22) and the first end plate (213), the compression direction of the elastic piece (23) is the same as the moving direction of the valve core (22), and the elastic piece (23) is used for clamping the positioning piece (24) between the first clamping groove (221) and the second clamping groove (216);

The pressure-holding well closing assembly (3) comprises an inner shell (31), a pressure holding seat (32) and a well closing shaft (33), wherein the inner shell (31) is positioned in the outer shell (1) and is connected with the outer shell (1), one end of the inner shell (31) is provided with a second opening (311), the other end of the inner shell is provided with a second end plate (312), the side wall of the inner shell (31) is provided with an overflow hole (313) close to the position of the second end plate (312), the pressure holding seat (32) is movably inserted in the inner shell (31), the pressure holding seat (32) is internally provided with a pressure holding channel (321), a first end of the pressure holding channel (321) is used for being in sealing contact with a pressure throwing ball (100), when the pressure holding seat (32) and the inner shell (31) are connected through a first shear pin (34), the second end of the pressure holding channel (321) is communicated with the first opening (212) through the overflow pin (313), the first end of the pressure holding channel (321) is movably inserted in the inner shell (31) through the second end (33) through the first end (31), the second end of the shut-in shaft (33) is communicated with the first end of the pressure holding channel (321);

The isolation cylinder (4) is located in the outer shell (1), one end of the isolation cylinder is abutted against the inner shell (31), and the other end of the isolation cylinder is abutted against the valve body (21), so that the second end plate (312) and the first opening (212) are mutually spaced.

2. The backflow preventer according to claim 1, wherein the positioning member (24) is a spherical structural member, the first clamping groove (221) is annular, the axis is parallel to the moving direction of the valve core (22), the radial joint surface of the first clamping groove (221) is semicircular, the second clamping groove (216) is annular, the axis is parallel to the moving direction of the valve core (22), the radial section of the second clamping groove (216) is a sector with a central angle of 90 degrees, and the spherical center of the positioning member (24), the central angle of the first clamping groove (221) and the central angle of the second clamping groove (216) which are clamped between the first clamping groove (221) and the second clamping groove (216) are coincident.

3. The backflow preventer according to claim 1, wherein the valve core (22) comprises a core body (222) and a valve rod (223), the core body (222) being connected to the first end of the valve rod (223), the portion of the core body (222) facing the first opening (212) having an outer contour matching the inner contour of the first opening (212), the elastic member (23) being compressed between the portion of the core body (222) facing the valve rod (223) and the first end plate (213).

4. A backflow preventer according to claim 3, wherein the valve core (22) further comprises a first limiting table (224), the first limiting table (224) is located at an included angle between the core body (222) and the valve rod (223), a second limiting table (2131) is provided on one side of the first end plate (213) facing the backflow cavity (211), one end of the elastic member (23) is sleeved on the first limiting table (224), and the other end of the elastic member (23) is sleeved on the second limiting table (2131).

5. Backflow preventer according to any one of claims 1-4, wherein the side of the holding-down seat (32) facing away from the second end plate (312) is provided with a plug-in table (322), which plug-in table (322) is intended to be plugged into the second end of the shut-in shaft (33).

6. The backflow preventer according to claim 5, wherein the pressure holding channel (321) comprises a tapered mouth (3211), a first channel (3212) and a second channel (3213);

the conical opening (3211) is positioned in the inserting table (322) and is used for being in sealing contact with the pressure-holding throwing ball (100);

one end of the first channel (3212) is communicated with one end of the conical opening (3211) with smaller inner diameter, and the other end of the first channel (3212) extends towards the second end plate (312);

One end of the second channel (3213) is communicated with the first channel (3212), and the other end of the second channel (3213) extends towards the overflow hole (313).

7. The backflow preventer according to any one of claims 1-4, wherein the inner side wall of the inner housing (31) has a plurality of backstop barbs (315), each backstop barb (315) being arranged in sequence along the direction of movement of the shut-in shaft (33), the outer side wall of the shut-in shaft (33) having an elastic backstop block (332), the elastic backstop block (332) being compressed between the outer side wall of the shut-in shaft (33) and the inner side wall of the inner housing (31).

8. Backflow preventer according to any one of claims 1-4, wherein the outer side wall of the inner housing (31) near the second opening (311) has an outer flange (314), the outer edge of the outer flange (314) being connected to the outer housing (1), the side of the outer flange (314) facing the second end plate (312) being in abutment with the isolation cylinder (4).

9. The backflow preventer according to any one of claims 1 to 4, wherein the first end of the shut-in shaft (33) has a bump seat (331), the bump seat (331) protruding from the outer side wall of the shut-in shaft (33) in the radial direction of the shut-in shaft (33).