CN114382437A

CN114382437A - Backflow preventer

Info

Publication number: CN114382437A
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: 2022-04-22
Anticipated expiration: 2040-10-21
Also published as: CN114382437B

Abstract

The utility model provides an anti-backflow device, belonging to the technical field of well cementation and comprising an outer shell and a backflow check valve component; the backflow check valve component comprises a valve body, a valve core, an elastic piece and a positioning piece, the valve body is located in an 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, a backflow hole and a plug hole are formed in the first end plate, the backflow hole is communicated with the backflow cavity, the valve core is inserted into the plug hole, the first end of the valve core is used for communicating or blocking the backflow 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 arranged in the moving direction of the valve core in a relative mode, the elastic piece is compressed between the valve core and the first end plate, the compression direction of the elastic piece is the same as 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 utility model belongs to the technical field of the well cementation, in particular to prevent refluence ware.

Background

In the process of oil and gas development, after the well drilling reaches a target layer, tail pipe descending operation can be carried out, and well cementation operation is carried out through a 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 designated position, the tail pipe is subjected to pressure building through ball throwing, so that the hanger is hung, and the tail pipe is fixed on the casing pipe. After the tail pipe is fixed, cement slurry is pumped to the tail pipe through ground cementing equipment, and in order to avoid the accident that the cement slurry flows back into the tail pipe to cause the blockage in the pipe, a floating collar is generally arranged at the end part of the tail pipe.

However, since the float collar acts like a check valve, only fluid is allowed to flow out of the tail pipe, but not into the tail pipe, during the tail pipe lowering process, the tail pipe is internally provided with a cavity, and well head grouting operation is required to balance the internal and external pressure difference of the tail pipe, so that the construction steps are complicated, and long construction time is required.

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 backflow check valve component comprises a valve body, a valve core, an elastic piece and a positioning piece, wherein the valve body is positioned 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 insertion hole, the backflow hole is communicated with the backflow cavity, the valve core is movably inserted in the insertion hole, the first end of the valve core is positioned in the backflow cavity and is used for communicating or blocking the backflow cavity and the first opening, the second end of the valve core is positioned outside the valve body, a first clamping groove is arranged at the position, close to the second end of the valve core, of the outer side wall of the valve core, a second clamping groove is arranged on one side of the first end plate, which is deviated from the backflow cavity, the second clamping groove is positioned at the edge of the insertion hole, and 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 compression direction of the elastic piece is the same as 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.

In an implementation manner of the present disclosure, the positioning element is a spherical structural element, the first clamping groove is annular, and the axis is parallel to the moving direction of the valve element, the radial joint surface of the first clamping groove is semicircular, the second clamping groove is annular, and the axis is parallel to the moving direction of the valve element, the radial section of the second clamping groove is in a sector shape with a central angle of 9 degrees, and the clamp is arranged between the first clamping groove and the second clamping groove the center of the positioning element, the central angle of the first clamping groove and the central angle of the second clamping groove coincide.

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

In another implementation manner of the present disclosure, the valve element 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 present disclosure, the flow back preventer further comprises a pressure-build-out shut-in assembly and an isolation cartridge;

the pressure-building well shut-off component comprises an inner shell, a pressure-building seat and a well shut-off shaft, 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 of the side wall of the inner shell, which is close to the second end plate, is provided with a flow hole, the pressure-building seat is movably inserted in the inner shell, a pressure-building channel is arranged in the pressure-building seat, the first end of the pressure-building channel is used for being in sealed contact with a pressure-building ball, when the pressure-building seat is connected with the inner shell through a first shear pin, the second end of the pressure-building channel is communicated with the first opening through the flow hole, the first end of the well shut-off shaft is positioned outside the inner shell, the second end of the well shut-off shaft is passed through the second opening and movably inserted in the inner shell and is connected through a second shear pin, the second end of the shut-off shaft is communicated with the first end of the pressure building channel;

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 spaced from each other.

In yet another implementation manner of the present disclosure, a side of the pressure building base facing away from the second end plate has an insertion platform, and the insertion platform is configured to be inserted into the second end of the shut-off shaft.

In yet another implementation of the present disclosure, the pressure build-up channel comprises a conical mouth, a first channel, and a second channel;

the conical opening is positioned in the insertion platform and is used for being in sealing contact with a pressure-building ball-throwing machine;

one end of the first channel is communicated with one end with smaller inner diameter of the conical port, 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 overflowing hole.

In another implementation manner of the present disclosure, the inner side wall of the inner housing has a plurality of backstop teeth, each of the backstop teeth is sequentially arranged along the moving direction of the closing shaft, the outer side wall of the closing shaft has an elastic backstop block, and the elastic backstop block is compressed between the outer side wall of the closing shaft and the inner side wall of the inner housing.

In another implementation manner of the present disclosure, an end of the outer side wall of the inner casing, which is close to the second opening, has an outer flange, an outer edge of the outer flange is connected to the outer casing, and a side of the outer flange, which faces the second end plate, abuts against the isolation cylinder.

In still another implementation manner of the present disclosure, the first end of the shut-in hole has a latch seat protruding from an outer sidewall of the shut-in hole in a radial direction of the shut-in hole.

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

when the backflow preventer provided by the embodiment of the disclosure is arranged on the tail pipe, the outer shell is connected with the tail pipe. In the process that the backflow preventer goes into the well together with the tail pipe, the first clamping groove and the second clamping groove clamp the positioning piece under the action of the elastic piece to limit the valve core to move towards the first opening, so that 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 backwards into the backflow cavity through the backflow hole and flow backwards into the tail pipe through the gap, and therefore grouting operation is not needed for balancing the internal and external pressure difference of the tail pipe.

After the liner is lowered to a designated position, pump circulation of the surface cementing equipment is started, so that the valve core is subjected to excitation pulses to move a distance away from the first opening and compress the elastic 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 the gravity of the positioning piece, namely the limitation that the valve core moves towards the first opening is removed, the reverse flow check valve assembly can have the function of a check valve, only fluid is allowed to flow out of a drilling well from the reverse flow check valve assembly, and the fluid is not allowed to flow into the reverse flow check valve assembly from the drilling well.

That is to say, in the process of the tail pipe running into the well, the backflow check valve assembly can allow fluid to flow out of the drilling well from the backflow check valve assembly and also can allow fluid to flow into the backflow check valve assembly from the drilling well, so that the drilling fluid in the drilling well can flow back into the tail pipe through the backflow check valve assembly, the influence of the internal and external pressure difference on the tail pipe can be reduced, and the tail pipe can run into the well smoothly. After the tail pipe is put into the well, the reverse flow check valve assembly only allows the fluid to flow out of the well from the reverse flow check valve assembly, but does not allow the fluid to flow into the reverse flow check valve assembly from the well, so that the cement slurry can be prevented from returning to the interior of the tail pipe, and the accident of plug left in the pipe can be avoided.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

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

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

FIG. 3 is a cross-sectional view of the reverse flow check valve assembly in the check valve position provided by the disclosed embodiment;

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-build-out shut-in assembly provided by an embodiment of the disclosure;

fig. 6 is a cross-sectional view of a pressure-build-up state of a pressure-build-up shut-in assembly provided by an embodiment of the present disclosure;

FIG. 7 is a cross-sectional view of a pressure-build-out shut-in assembly in a slurry replacement state provided by an embodiment of the disclosure;

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

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

The symbols in the drawings represent the following meanings:

1. an outer housing; 2. a back-flow check valve assembly; 21. a valve body; 211. pouring the cavity; 212. a first opening; 213. a first end plate; 2131. a second limit table; 214. pouring the water into the hole; 215. inserting holes; 216. a second card slot; 217. a first valve body; 218. a second valve body; 22. a valve core; 221. a first card slot; 222. a core body; 223. a valve stem; 224. a first limit table; 23. an elastic member; 24. a positioning member; 3. a pressure-building well shut-in component; 31. an inner housing; 311. a second opening; 312. a second end plate; 313. an overflowing hole; 314. an outer flange; 315. stopping and chamfering; 32. a pressure building seat; 321. a pressure building channel; 3211. a tapered mouth; 3212. a first channel; 3213. a second channel; 322. an inserting table; 33. closing the shaft; 331. a bumping seat; 332. an elastic backstop block; 34. a first shear pin; 35. a second shear pin; 4. an isolation cylinder; 100. and (5) pressing and throwing the ball.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

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

In order to solve the above technical problem, an embodiment of the present disclosure provides a backflow preventer, as shown in fig. 1, the backflow preventer includes an outer housing 1 and a backflow check valve assembly 2.

Fig. 2 is a cross-sectional view of the backflow check valve assembly 2 in a backflow state, referring to fig. 2, the backflow 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 connected to the outer housing 1, the valve body 21 has a backflow cavity 211 therein, one end of the valve body 21 has a first opening 212, the other end has a first end plate 213, the first end plate 213 has a backflow hole 214 and an insertion hole 215, the backflow hole 214 is communicated with the backflow cavity 211, the valve core 22 is movably inserted into the insertion hole 215, the first end of the valve core 22 is located in the backflow cavity 211 and used for communicating or blocking the backflow cavity 211 and the first opening 212, the second end is located outside the valve body 21, a first locking groove 221 is located at a position of an outer side wall of the valve core 22 close to the second end thereof, a second locking groove 216 is located at a side of the first end plate 213 facing away from the backflow cavity 211, the second locking groove 216 is located at an edge of the insertion hole 215, the second engaging groove 216 and the first engaging groove 221 are disposed opposite to each other in the moving direction of the spool 22, the elastic member 23 is compressed between the spool 22 and the first end plate 213, the compression direction of the elastic member 23 is the same as the moving direction of the spool 22, and the elastic member 23 is used to clamp the positioning member 24 between the first engaging groove 221 and the second engaging groove 216.

When the backflow preventer provided by the embodiment of the present disclosure is disposed on the tail pipe, the outer casing 1 is connected to the tail pipe (not shown). With continued reference to fig. 2, during the process of lowering the anti-backflow device with the tail pipe, the first engagement groove 221 and the second engagement groove 216 clamp the positioning member 24 under the action of the elastic member 23 to limit the valve core 22 from moving toward the first opening 212, so that a gap exists between the valve core 22 and the first opening 212. Since there is a gap between the spool 22 and the first opening 212, the drilling fluid in the well can flow back into the back-flow cavity 211 through the back-flow hole 214 and flow back into the tail pipe through the gap, so that there is no need to perform a grouting operation in order to balance the pressure difference between the inside and outside of the tail pipe.

Fig. 3 is a cross-sectional view of the reverse flow check valve assembly 2 in the check valve state, and with reference to fig. 3, after the liner is lowered to the desired position, the pump cycle of the surface cementing equipment is started, so that the spool 22 is subjected to an activation pulse to move a short distance away from the first opening 212 and compress the resilient member 23. During the movement of the spool 22, the first engaging groove 221 and the second engaging groove 216 release the clamping of the positioning element 24, so that the positioning element 24 falls off under the action of its own weight, i.e., the restriction of the spool 22 moving toward the first opening 212 is released, so that the reverse 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 reverse check valve assembly 2, but not fluid is allowed to flow into the reverse check valve assembly 2 from the well.

That is to say, in the process of the tail pipe running into the well, the backflow check valve assembly 2 can allow fluid to flow out of the drilling well from the backflow check valve assembly 2 and also can allow fluid to flow into the backflow check valve assembly 2 from the drilling well, so that the drilling fluid in the drilling well can flow back into the tail pipe through the backflow check valve assembly 2, the influence of the internal and external pressure difference on the tail pipe can be reduced, and the tail pipe can run into the well smoothly. After the tail pipe is put into the well, the reverse flow check valve assembly 2 only allows the fluid to flow out of the well from the reverse flow check valve assembly 2, but does not allow the fluid to flow into the reverse flow check valve assembly 2 from the well, so that the cement slurry can be prevented from being returned to the interior of the tail pipe, and the accident of plug remaining in the pipe can be avoided.

From the foregoing, the reverse flow check valve assembly 2 plays a key role in smooth lowering of the tail pipe, and the reverse flow check valve assembly 2 will be described in the following.

Fig. 4 is a partially enlarged view of a portion a of fig. 2, in order to clearly show the relationship between the first locking groove 221, the second locking groove 216 and the positioning element 24, a gap between the three is enlarged in fig. 4, and actually, the three are in close contact with each other under the action of the elastic element 23.

Referring to fig. 4, in the present embodiment, the positioning element 24 is a spherical structural element, the first engaging groove 221 is annular, the axis of the first engaging groove 221 is parallel to the moving direction of the valve core 22, the radial contact surface of the first engaging groove 221 is semicircular, the second engaging groove 216 is annular, the moving direction of the valve core 22 is parallel, the radial cross section of the second engaging groove 216 is sector with a central angle of 90 °, and the spherical center of the positioning element 24, the central angle of the first engaging groove 221, and the central angle of the second engaging groove 216 clamped between the first engaging groove 221 and the second engaging groove 216 coincide with each other.

When the first engaging groove 221 and the second engaging groove 216 are engaged with the positioning member 24, the first engaging groove 221 and the second engaging groove 216 together form an annular engaging space. Since the radial section of the second engaging groove 216 is a sector with a central angle of 90 °, on the radial section of the clamping space, the clamping space is a sector with a central angle of 270 °, so that a sector notch with a central angle of 90 ° is reserved in the clamping space, and the positioning element 24 can move away from the backflow cavity 211 along with the valve core 22. In the process of assembling the positioning member 24, the valve plug 22 is driven to move away from the backflow cavity 211 to compress the elastic member 23, so that the first engaging groove 221 is located outside the valve body 21. Then, the positioning element 24 is placed in the first clamping groove 221, the valve core 22 is released, so that the valve core 22 drives the second clamping groove 216 to move towards the first clamping groove 221 under the action of the elastic element 23, and finally, the positioning element 24 is clamped through the first clamping groove 221 and the second clamping groove 216 under the action of the elastic element 23, and the assembly of the positioning element 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 connected by screw threads and are inserted with pins. The outer side wall of the first valve body 217 is in threaded connection with the inner side wall of the outer housing 1, and the first opening 212 is located in 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 222 and a stem 223, the core 222 is connected to a first end of the stem 223, a part of the outer contour of the core 222 facing the first opening 212 matches with the inner contour of the first opening 212, and the elastic member 23 is compressed between a part of the core 222 facing the stem 223 and the first end plate 213.

In the above implementation, the core 222 is used to cooperate with the first opening 212 to communicate or block the backflow cavity 211 with 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 forced away from the first opening 212 by the pressure of the fluid, the reverse flow cavity 211 communicates with the first opening 212. A valve stem 223 is movably inserted in the insertion hole 215 for providing a mounting base for the core 222 such that the core 222 can move relative to the valve body 21.

Illustratively, the end of the first opening 212 facing the core 222 is tapered, and the corresponding portion of the core 222 facing the first opening 212 is tapered, so as to enable the core 222 to be matched with the first opening 212, thereby ensuring effective sealing of the core 222 with respect to the first opening 212.

Optionally, the outer wall of the core 222 is coated with an anti-corrosive coating to prevent corrosion of the core 222 and 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. In order to avoid unnecessary shaking of the elastic member 23 due to neutral position uncertainty, 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 is provided with 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 to say, the both ends of elastic component 23 cup joint respectively on first spacing platform 224 and second spacing platform 2131, and first spacing platform 224 and second spacing platform 2131 can play spacing effect to elastic component 23 for elastic component 23 stretches out and draws back between first spacing platform 224 and second spacing platform 2131 all the time.

Optionally, the elastic element 23 is a coil spring, the first limiting table 224 and the second limiting table 2131 are cylindrical structural members, the first limiting table 224 and the second limiting table 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 table 224 and the second limiting table 2131, so that the limitation on the coil spring can be realized.

Illustratively, the core 222, the stem 223, and the first stop 224 are a unitary structural member, thereby improving the structural integrity of the valve cartridge 22, improving the manufacturing efficiency of the valve cartridge 22, and reducing the manufacturing cost.

Referring to fig. 1 again, in order to completely prevent cement slurry from flowing back into the tail pipe after the well is lowered, the backflow preventer further comprises a pressure-holding well shut-in assembly 3 and an isolation cylinder 4.

Fig. 5 is a cross-sectional view of a downhole state of the pressure-controlled well shut-in assembly, referring to fig. 5, the pressure-controlled well shut-in assembly 3 includes an inner housing 31, a pressure-controlled seat 32 and a well shut-in shaft 33, the inner housing 31 is located in the outer housing 1 and connected to 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 lateral wall of the inner housing 31 has a through hole 313 near the second end plate 312, the pressure-controlled seat 32 is movably inserted in the inner housing 31, a pressure-controlled passage 321 is provided in the pressure-controlled seat 32, a first end of the pressure-controlled passage 321 is used for sealing contact with the pressure-controlled ball 100, when the pressure-controlled seat 32 and the inner housing 31 are connected by a first shear pin 34, a second end of the pressure-controlled passage 321 is communicated with the first opening 212 by the through hole 313, the first end of the well shut-in shaft 33 is located outside the inner housing 31, the second end of the shut-off shaft 33 passes through the second opening 311 and is movably inserted in the inner housing 31 and connected through the second shear pin 35, the second end of the shut-off shaft 33 is communicated with the first end of the pressure-holding channel 321, the isolation cylinder 4 is positioned in the outer housing 1, one end of the isolation cylinder abuts against the inner housing 31, and the other end of the isolation cylinder abuts against the valve body 21, so that the second end plate 312 and the first opening 212 are spaced from each other.

In the process that the backflow preventer goes down the well along with the tail pipe, the pressure building base 32 is connected with the inner shell 31 through the first shear pin 34, and the shut-off shaft 33 is connected with the inner shell 31 through the second shear pin 35. In this state, the shut-in hole 33, the pressure-holding channel 321, the overflowing hole 313 and the first opening 212 are communicated in sequence, and drilling fluid in the drilling well can enter the tail pipe through the backflow check valve assembly 2 and the pressure-holding shut-in hole assembly 3 in sequence. After the back-flow check valve assembly 2 is changed to the check valve state, the pressure build-up pitching ball 100 is thrown into the tailpipe such that the pressure build-up pitching ball 100 is in sealing contact with the first end of the pressure build-up channel 321 (see fig. 6). At this time, the shut-in shaft 33 and the pressure-building channel 321 are blocked, and pressure building begins above the pressure-building channel 321 (towards the wellhead direction), so that the hanger is hung. Along with the pressure building, the pressure acting on the pressure building seat 32 is gradually increased, the pressure building seat 32 shears the first shear pin 34 and moves towards the second end plate 312, and the shut-off shaft 33 is directly communicated with the overflowing hole 313 (see fig. 7), so that cement slurry and displacement fluid can sequentially pass through the pressure building well shut-off assembly 3 and the backflow check valve assembly 2 to enter the bottom of the well, and therefore circulation operation and displacement operation are conducted. After the circulation operation and the slurry replacement operation are completed, the well cementation rubber plug is released, so that the well cementation rubber plug generates impact pressure with the first end of the shut-in well bore 33, the shut-in well bore 33 cuts off the second shear pin 35 along with the gradual increase of the pressure acting on the shut-in well bore 33 and moves towards the pressure building seat 32, and the side wall of the shut-in well bore 33 blocks the overflowing hole 313 (see fig. 8), so that the fluid in the well is completely blocked from returning to the interior of the tail pipe.

That is to say, not only will not influence the normal work of flowing backward check valve subassembly 2 through suppressing pressure shut-in well subassembly 3, can also play the effect of suppressing pressure and shut-in well.

In addition, set up an isolation section of thick bamboo 4 between flowing backward check valve subassembly 2 and suppress pressure and shut the well subassembly 3, can keep apart between flowing backward check valve subassembly 2 and the suppress pressure and shut the well subassembly 3 for can not produce the mutual interference influence between flowing backward check valve subassembly 2 and the suppress pressure and shut the well subassembly 3, also guaranteed the normal circulation of fluid in preventing the refluence ware.

Referring again to fig. 5, in the present embodiment, a side of the pressure build-up seat 32 facing away from the second end plate 312 has an insertion stage 322, and the insertion stage 322 is configured to be inserted into the second end of the shut-in hole 33.

The insertion platform 322 is used for ensuring the assembling stability between the shut-off shaft 33 and the pressure building 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 shut-off shaft 33 and the pressure building seat 32 is avoided.

Illustratively, the platform 322 is a cylindrical structure, and the outer peripheral wall of the platform 322 is in sliding contact with the inner peripheral wall of the shut-in well bore 33.

Optionally, the pressure-building channel 321 includes a tapered port 3211, a first channel 3212 and a second channel 3213, the tapered port 3211 is located in the insertion platform 322 and is configured to be in sealing contact with the pressure-building pitching ball 100, one end of the first channel 3212 is communicated with the end of the tapered port 3211 with the smaller inner diameter, 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 flow passing hole 313.

In the above implementation, the tapered opening 3211 is used to accommodate the pressure-controlled ball pitching machine 100, and since the insertion platform 322 is inserted into the shut-off shaft 33, the pressure-controlled ball pitching machine 100 can accurately fall into the tapered opening 3211 to block the shut-off shaft 33 and the pressure-controlled passage 321. The first and

second passages

3212, 3213 serve to provide a communication path between the tapered opening 3211 and the overflow aperture 313.

Illustratively, the first passage 3212 is coaxial with the tapered port 3211, which enables better fluid communication between the first passage 3212 and the tapered port 3211. The second channel 3213 is perpendicular to the first channel 3212, and when the pressure building seat 32 and the inner housing 31 are connected by the first shear pin 34, the second channel 3213 is coaxial with the flow hole 313, which enables better fluid communication between the second channel 3213 and the flow hole 313.

With continued reference to fig. 5, in the present embodiment, an end of the outer side wall of the inner casing 31 near the second opening 311 is provided with an outer flange 314, an outer edge of the outer flange 314 is connected with the outer casing 1, and a side of the outer flange 314 facing the second end plate 312 is abutted against the insulating cylinder 4.

Alternatively, the outer edge of the outer flange 314 is screwed to the inner side wall of the outer housing 1, so that the inner housing 31 and the outer housing 1 can be attached and detached. Further, since the outer flange 314 protrudes from the outer wall of the inner housing 31 in the radial direction of the inner housing 31, the outer wall of the inner housing 31 does not directly contact the inner wall of the outer housing 1. In this way, it is possible to provide a space for the fluid to flow through the flow hole 313 to ensure a normal flow of the fluid.

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

Fig. 9 is a partial enlarged view of fig. 5 at B, and referring to fig. 9, in this embodiment, the inner side wall of the inner housing 31 has a plurality of anti-back-up teeth 315, each anti-back-up tooth 315 is sequentially arranged along the moving direction of the closed shaft 33, the outer side wall of the closed shaft 33 has an elastic anti-back-up block 332, and the elastic anti-back-up block 332 is compressed between the outer side wall of the closed shaft 33 and the inner side wall of the inner housing 31.

Through the cooperation between stopping pawl 315 and the elasticity stopping block 332, can avoid closing shaft 33 and deviate from second end plate 312 and remove, guaranteed to close shaft 33 and after blocking discharge orifice 313, can remain throughout to block, improved the reliability of preventing flowing back ware.

Illustratively, the backstop pawl 315 includes a slope that is inclined with respect to the axis of the inner housing 31 and faces the second opening 311, and a vertical 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, thereby enabling a normal passage. While the resilient backstop 332 has a tendency to move away from the second end plate 312, the vertical surface will block the resilient backstop 332, i.e., the shut-in well bore 33, from moving away from the second end plate 312.

The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.

Claims

1. The backflow preventer is characterized by comprising an outer shell (1) and a backflow check valve assembly (2);

the backflow 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 located in the outer shell (1) and connected with the outer shell (1), a backflow cavity (211) is arranged in the valve body (21), 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 backflow hole (214) and an insertion hole (215), the backflow hole (214) is communicated with the backflow cavity (211), the valve core (22) is movably inserted in the insertion hole (215), the first end of the valve core (22) is located in the backflow cavity (211) and used for communicating or blocking the backflow cavity (211) and the first opening (212), and the second end of the valve core is located outside the valve body (21), the outer side wall of the valve core (22) is provided with a first clamping groove (221) at a position close to the second end of the valve core, one side, away from the backflow cavity (211), of the first end plate (213) is provided with a second clamping groove (216), the second clamping groove (216) is located at the edge of the insertion hole (215), the second clamping groove (216) and the first clamping groove (221) are oppositely arranged in the moving direction of the valve core (22), 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).

2. The anti-backflow device according to claim 1, wherein the positioning member (24) is a spherical structural member, the first engaging groove (221) is annular, an axis of the first engaging groove is parallel to a moving direction of the valve element (22), a radial contact surface of the first engaging groove (221) is semicircular, the second engaging groove (216) is annular, the axis of the second engaging groove is parallel to the moving direction of the valve element (22), a radial cross section of the second engaging groove (216) is a sector with a central angle of 90 °, and a spherical center of the positioning member (24), a central angle of the first engaging groove (221), and a central angle of the second engaging groove (216) interposed between the first engaging groove (221) and the second engaging groove (216) coincide with each other.

3. The flow reverser according to claim 1, wherein the valve core (22) comprises 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 part of the outer contour of the core body (222) facing the first opening (212) is matched with the inner contour of the first opening (212), and the elastic member (23) is compressed between a part of the core body (222) facing the valve rod (223) and the first end plate (213).

4. The 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 a included angle between the core body (222) and the valve rod (223), a second limiting table (2131) is arranged 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. The flow back preventer according to any one of claims 1-4, further comprising a pressure-build-up shut-in assembly (3) and an isolation cartridge (4);

the suppress pressure shut-in well subassembly (3) includes interior casing (31), suppress pressure seat (32) and shut down shaft (33), interior casing (31) is located in shell body (1), and with shell body (1) links to each other, the one end of interior casing (31) has second opening (311), and the other end has second end plate (312), the lateral wall of interior casing (31) is close to the position of second end plate (312) has through-hole (313), suppress pressure seat (32) position movably insert and establish in interior casing (31), suppress pressure seat (32) and have suppress pressure passageway (321) in, the first end of suppressing pressure passageway (321) is used for throwing ball (100) sealing contact with suppressing pressure, works as suppress pressure seat (32) and when linking to each other through first shear pin (34) between interior casing (31), the second end of suppressing pressure passageway (321) passes through-hole (313) with first opening (212) intercommunication, the first end of the shut-off shaft (33) is positioned outside the inner shell (31), the second end of the shut-off shaft (33) penetrates through the second opening (311) and is movably inserted into the inner shell (31) and is connected through a second shear pin (35), and the second end of the shut-off shaft (33) is communicated with the first end of the pressure-holding channel (321);

the isolation cylinder (4) is positioned 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 spaced from each other.

6. The backflow preventer according to claim 5, characterized in that a side of the pressure build-up seat (32) facing away from the second end plate (312) has a plug-in table (322), the plug-in table (322) being intended for being inserted into a second end of the shut-off shaft (33).

7. The flow back preventer of claim 6, wherein the pressure build-up channel (321) comprises a tapered mouth (3211), a first channel (3212), and a second channel (3213);

the conical opening (3211) is positioned in the insertion platform (322) and is used for being in sealing contact with a pressure-building ball (100);

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

one end of the second passage (3213) communicates with the first passage (3212), and the other end of the second passage (3213) extends toward the overflowing hole (313).

8. The backflow preventer according to claim 5, characterized in that the inner side wall of the inner housing (31) has a plurality of anti-backup teeth (315), each anti-backup tooth (315) is arranged in sequence along the moving direction of the shut-off shaft (33), the outer side wall of the shut-off shaft (33) has an elastic anti-backup block (332), and the elastic anti-backup block (332) is compressed between the outer side wall of the shut-off shaft (33) and the inner side wall of the inner housing (31).

9. The backflow preventer according to claim 5, characterized in that the outer side wall of the inner shell (31) at the end close to the second opening (311) has an outer flange (314), the outer edge of the outer flange (314) is connected to the outer shell (1), and the side of the outer flange (314) facing the second end plate (312) abuts against the insulating cylinder (4).

10. The flow back preventer according to claim 5, characterized in that the first end of the shut-off shaft (33) has a striker (331), and the striker (331) protrudes from the outer sidewall of the shut-off shaft (33) in the radial direction of the shut-off shaft (33).