Multi-stage blowout preventer for testing high-pressure gas injection well

Abstract

The utility model discloses a multi-stage blowout preventer for testing a high-pressure gas injection well, which comprises two blowout prevention units connected in series, sealing bottom joints of the two blowout prevention units are respectively screwed at a lower port of a lower sealing cylinder, a rubber block pressed on the sealing bottom joints is arranged in the lower sealing cylinder, and a sealing gland is arranged above the rubber block; the upper port of the lower sealing cylinder is screwed with a double-male joint, and the central hole of the double-male joint is communicated with the central holes of the sealing gland, the rubber block and the sealing bottom joint; the middle section of a center hole of the double-male connector is provided with an expanded drainage cavity, one side of the double-male connector is connected with a confluence tee joint in a screwed mode, and a middle inlet of the confluence tee joint is communicated with the drainage cavity; an axial hydraulic channel is arranged in the axial direction of the double-male connector, and a lower port of the axial hydraulic channel is communicated with the space above the sealing gland. The other side of the double-male connector is connected with a hydraulic connector in a screwed mode, and an inner port of the hydraulic connector is communicated with the middle section of the axial hydraulic channel. The device can realize reliable sealing of the wellhead, and is good in safety and long in service life.

Description

Technical Field

[0001] The utility model relates to a wellhead blowout prevention device, in particular to a multi-stage blowout prevention device for testing a high-pressure gas injection well, belonging to the technical field of blowout prevention equipment for self-flowing wells. Background Art

[0002] The wellhead pressure of high-pressure gas injection wells often reaches more than 15MPa. When conducting downhole testing, it is necessary to lower the test instrument into the wellhead. The test instrument is usually suspended at the lower end of the wire rope, and the wire rope goes down along the blowout preventer, and the test instrument is gradually lowered from the wellhead to the position where the test is required. In order to prevent the wellhead from overflowing and damaging the ecological environment, it is necessary to install a blowout preventer on the well plug. Its main function is to raise the wellhead to increase the static pressure of the liquid column in the wellbore, and to recover the workover fluid in the wellbore into a designated container for treatment before it overflows, so as to prevent overflow pollution.

[0003] The top port of the blowout preventer is usually screwed with a high-pressure blowout preventer plug, which includes a coaxial blowout preventer plug joint, a center rod, a water drainage chamber and a pressure cap. The lower end of the blowout preventer plug joint is provided with a male thread screwed with the upper joint of the blowout preventer, and the upper end of the blowout preventer plug joint is provided with a countersunk hole extending along the axis. The inner circumference of the countersunk hole is provided with a female thread and is screwed with the male thread at the lower end of the center rod. The upper end of the center rod is screwed into the lower port of the water drainage chamber, and the lower end of the pressure cap is screwed into the upper port of the water drainage chamber. The side wall of the water drainage chamber is connected with a water nozzle, and the channel of the water nozzle is communicated with the inner cavity of the water drainage chamber. The centers of the pressure cap, the center rod and the blowout preventer plug joint are all provided with a through hole extending along the axis, and a sealing ring is provided between the lower end surface of the center rod and the bottom surface of the countersunk hole.

[0004] The upper part of the blowout preventer is fixed with a sky pulley through a bracket, and the logging wire passes through the rope groove of the sky pulley and the center hole of the blowout preventer plug, and then goes down along the blowout preventer to connect with the testing instrument downhole. Although the blowout preventer has a certain height, due to the high downhole pressure of the self-flowing well, the well body will still overflow upward from the center hole of the blowout preventer plug joint, enter the drainage chamber through the center hole of the center rod, and flow out from the water nozzle on the side of the drainage chamber.

[0005] After the logging wire is in place or liquid is still flowing out of the nozzle, the center rod needs to be screwed in to tighten the sealing ring to prevent the underground liquid from overflowing upward from the center hole of the blowout preventer plug joint. Since the blowout preventer plug is about three meters above the ground, it is difficult for the operator to climb more than three meters to use a wrench to turn the center rod, which poses a safety risk; when liquid flows out, the speed of tightening the plug is relatively slow, and water leakage can easily cause pollution to the well site. If the center rod is not tightened in place, it is easy to cause water leakage, causing the wellhead and pipeline to be slippery, leaving workers prone to stepping on empty space and other safety hazards.

[0006] The Chinese utility model patent with publication number CN 204040985U discloses a high-pressure blowout prevention plug, including a coaxial blowout prevention plug joint, a center rod, a water discharge chamber and a pressure cap. The lower end of the blowout prevention plug joint is provided with a male thread screwed with the upper joint of the blowout prevention pipe, the upper end of the blowout prevention plug joint is provided with a countersunk hole extending along the axis, the inner circumference of the countersunk hole is provided with a female thread and is screwed with the male thread at the lower end of the center rod, the upper end of the center rod is screwed into the lower port of the water discharge chamber, and the pressure cap is provided with a female thread screwed with the male thread at the lower end of the center rod. The lower end is screwed into the upper port of the drainage chamber, the side wall of the drainage chamber is connected with a water nozzle, the channel of the water nozzle is communicated with the inner cavity of the drainage chamber, the centers of the pressure cap, the center rod and the anti-blowout plug joint are all provided with a through hole extending along the axis, a sealing ring is provided between the lower end surface of the center rod and the bottom surface of the countersunk hole, the middle periphery of the center rod in the height direction is a regular hexagonal cross-section, and a ratchet wrench adapted to the regular hexagonal cross-section is mounted, and the handle of the ratchet wrench extends in the horizontal direction.

[0007] This technical solution eliminates the need to clamp the wrench at high altitude, but still requires climbing to a certain height and rotating the wrench forcefully at high altitude, which still presents a large safety risk. When a puncture occurs, the handling action is slow, which not only pollutes the surrounding environment, but also causes certain harm to the operator. Utility Model Content

[0008] The purpose of this section is to summarize some aspects of the embodiments of the utility model and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and utility model name of this application to avoid blurring the purpose of this section, specification abstract and utility model name, and such simplifications or omissions cannot be used to limit the scope of the utility model.

[0009] In view of the above problems and / or the problems existing in the prior art, the present utility model is proposed.

[0010] The purpose of the utility model is to overcome the problems existing in the prior art and provide a multi-stage blowout preventer for testing a high-pressure gas injection well, which can achieve reliable sealing of the wellhead without high-altitude climbing, has good safety, and can extend the service life of the sealing material.

[0011] In order to solve the above technical problems, the utility model provides a multi-stage blowout prevention device for testing a high-pressure gas injection well, comprising two blowout prevention units connected in series, the two blowout prevention units respectively comprising a sealing bottom joint, the sealing bottom joint being respectively screwed to the lower port of the lower sealing cylinder, the lower sealing cylinder being provided with a rubber block pressed on the sealing bottom joint, and a sealing gland being provided above the rubber block; a double male joint being screwed to the upper port of the lower sealing cylinder, the center hole of the double male joint being connected to the center hole of the sealing gland, the rubber block and the sealing bottom joint; a drainage chamber with an enlarged diameter is provided in the middle section of the center hole of the double male joint, a confluence tee being screwed to one side of the double male joint, and a middle inlet of the confluence tee being connected to the drainage chamber; an axial hydraulic channel being provided along the axial direction of the double male joint, the lower port of the axial hydraulic channel being connected to the space above the sealing gland; a hydraulic joint being screwed to the other side of the double male joint, the inner port of the hydraulic joint being connected to the middle section of the axial hydraulic channel.

[0012] Furthermore, the upper periphery of the double male connector is screwed to the lower end of the upper sealing cylinder, the upper center of the double male connector is filled with packing, a packing gland is provided above the packing, and the space above the packing gland is communicated with the upper port of the axial hydraulic channel.

[0013] Furthermore, an upper sealing tube reduced diameter section is provided at the lower part of the upper sealing tube, and an upper choke tube extending upward is connected to the center of the packing gland, and the root of the upper choke tube passes through the center hole of the upper sealing tube reduced diameter section.

[0014] Furthermore, a plurality of choke tube drainage holes are evenly arranged along the height direction and circumferential direction of the upper choke tube, the lower side wall of the upper sealing cylinder is connected with a drainage elbow, the outlet of the drainage elbow is connected with the upper inlet of the converging tee through an external thread joint, and the lower end outlet of the converging tee is connected with a drainage interface.

[0015] Furthermore, a gland center tube extending upward is provided at the top center of the sealing gland, and the gland center tube is inserted into the center hole of the double male connector.

[0016] Furthermore, the lower end of the sealing bottom joint of the lower blowout preventer unit is screwed to the upper port of the wellhead blowout preventer.

[0017] Furthermore, a lower choke tube is screwed into the central screw hole at the lower end of the sealing bottom joint of the lower blowout preventer unit, and the lower end of the lower choke tube is inserted into the upper port of the wellhead blowout preventer.

[0018] Furthermore, the upper end of the upper sealing cylinder of the lower blowout prevention unit is reduced in diameter to form a cone, and is screwed to the lower end center screw hole of the sealing bottom joint of the upper blowout prevention unit.

[0019] Furthermore, sealing tube support ears for supporting the sky pulley are symmetrically arranged on the outer periphery of the upper sealing tube of the upper blowout prevention unit.

[0020] Furthermore, a top sealing gasket is embedded in the upper port of the upper sealing cylinder of the upper blowout prevention unit and a blowout prevention cap is screwed thereon, and a center hole for the wire rope to pass through is provided at the center of the blowout prevention cap.

[0021] Compared with the prior art, the utility model has achieved the following beneficial effects: 1. During the process of entering the well, the wire rope passes through the top sealing pad and the two-stage upper choke tube, packing, rubber block, and multi-stage decompression and sealing of the lower choke tube in sequence, which can ensure the sealing effect of the high-pressure well fluid of the self-flowing well;

[0022] 2. In the absence of overflow, it can avoid excessive compression of sealing materials at all levels, avoid excessive friction between the wire rope and sealing materials at all levels, reduce wear, and enable the test instrument to quickly descend and quickly reach the test position to complete the test;

[0023] 3. In case of overflow, the hydraulic pump will automatically compress the sealing materials at all levels to avoid overflow at the wellhead;

[0024] 4. A small amount of overflow can be smoothly discharged and collected in the drainage pipeline, completely avoiding wellhead pollution;

[0025] 5. Operators do not need to climb high to work, which avoids the risk of falling during high-altitude work and the risk of high-altitude tools slipping and falling and injuring people, which is beneficial to protecting the physical and mental health of operators. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. The drawings are only provided for reference and explanation, not for limiting the present utility model. Among them:

[0027] Figure 1 It is a cross-sectional view of a multi-stage blowout prevention device for testing a high-pressure gas injection well according to the utility model;

[0028] In the figure: 1. spray cap; 2. top sealing gasket; 3. upper sealing cylinder; 4. sealing cylinder support ear; 5. upper choke tube; 5a. choke tube drain hole; 6. drain elbow; 7. external thread joint; 8. packing gland; 9. packing; 10. double male joint; 11. drain chamber; 12. axial hydraulic channel; 13. converging tee; 14. drain interface; 15. hydraulic joint; 16. sealing gland; 17. gland center tube; 18. rubber block; 19. lower sealing cylinder; 20. sealing bottom joint; 21. lower choke tube. DETAILED DESCRIPTION

[0029] In the following description of the present invention, the terms "upper", "lower", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific direction.

[0030] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below with reference to specific figures. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0032] like Figure 1 As shown, the multi-stage blowout preventer for testing a high-pressure gas injection well of the utility model comprises two blowout preventer units connected in series, the two blowout preventer units respectively comprising an upper sealing cylinder 3, an upper choke tube 5, a drain elbow 6, a packing gland 8, a packing 9, a double male joint 10, a drain chamber 11, an axial hydraulic channel 12, a converging tee 13, a drain interface 14, a hydraulic joint 15, a sealing gland 16, a rubber block 18, a lower sealing cylinder 19 and a sealing bottom joint 20, and the center holes of the components on the axis of the device are sequentially connected for the wire rope to pass through.

[0033] The sealing bottom joint 20 is screwed to the lower port of the lower sealing cylinder 19 respectively. The lower sealing cylinder 19 is provided with a rubber block 18 pressed on the sealing bottom joint 20. Two rubber blocks 18 are stacked, and the end faces in contact with each other are flat, and the outer end faces are convex arc surfaces, that is, the top of the upper rubber block 18 is raised upward, and the bottom of the lower rubber block 18 is raised downward, so that after the two rubber blocks 18 are stacked, the thickness of the central hole area for the steel wire rope to pass through is the thickest, which is conducive to extending the sealing length and improving the sealing effect. A sealing gland 16 is provided above the rubber block 18, and the bottom of the sealing gland 16 is a concave arc surface that matches the rubber block 18, which is convenient for pressing the lower rubber block 18. The outer periphery of the sealing gland 16 is embedded with a gland sealing ring to achieve sealing with the inner wall of the lower sealing cylinder 19.

[0034] The upper end of the lower sealing cylinder 19 is screwed with a double male joint 10, and the center hole of the double male joint 10 is connected with the center holes of the sealing gland 16, the rubber block 18 and the sealing bottom joint 20. A drainage chamber 11 is provided in the middle section of the center hole of the double male joint, and the drainage chamber 11 collects overflow from below by expanding the diameter.

[0035] The top center of the sealing gland 16 is provided with a gland center tube 17 extending upward, and the gland center tube 17 is inserted into the center hole of the double male connector 10 to center the sealing gland 16 and prevent the sealing gland 16 from being skewed. A sealing ring is provided at the outer periphery of the root of the gland center tube 17, and the sealing ring is embedded in the inner wall of the center hole of the double male connector 10.

[0036] A confluence tee 13 is screwed onto one side of the double male connector 10 , and a middle inlet of the confluence tee 13 is communicated with the drainage chamber 11 , so as to discharge a small amount of well fluid collected in the drainage chamber 11 .

[0037] The upper periphery of the double male joint 10 is screwed to the lower end of the upper sealing cylinder 3, and the upper center of the double male joint 10 is filled with packing 9. A packing gland 8 is provided above the packing 9. A gland sealing ring is embedded in the outer periphery of the packing gland 8 to achieve sealing with the inner wall of the center hole of the double male joint 10.

[0038] An axial hydraulic channel 12 is provided along the axial direction of the double male connector 10, and a hydraulic connector 15 is screwed on the other side of the double male connector 10. The inner port of the hydraulic connector 15 is communicated with the middle section of the axial hydraulic channel 12, and the inlet of the hydraulic connector 15 is connected to the outlet oil pipe of the hydraulic pump.

[0039] The lower port of the axial hydraulic passage 12 is in communication with the upper space of the sealing gland 16, and the upper space of the packing gland 8 is in communication with the upper port of the axial hydraulic passage 12. Start the hydraulic pump, and the pressure oil enters the axial hydraulic passage 12 of the double male connector 10 through the hydraulic connector 15, and then pressurizes the top of the sealing gland 16 and the packing gland 8, so that the rubber block 18 and the packing 9 further hold the wire rope to prevent leakage.

[0040] The lower part of the upper sealing cylinder 3 is provided with an upper sealing cylinder reduced diameter section, and the center of the packing gland 8 is connected with an upper choke tube 5 extending upward, and the root of the upper choke tube 5 passes through the center hole of the upper sealing cylinder reduced diameter section. An O-type sealing ring is embedded in the inner wall of the center hole of the upper sealing cylinder reduced diameter section to achieve sealing with the outer periphery of the root of the upper choke tube 5.

[0041] Multiple groups of choke tube drain holes 5a are arranged along the height direction of the upper choke tube 5, and the phases of two adjacent groups of choke tube drain holes 5a are staggered. The inner diameter of the upper choke tube 5 is 0.2 to 0.4 mm larger than the outer diameter of the wire rope, which ensures that the wire rope can slide smoothly and reduces the leakage gap. A small amount of well fluid can only flow upward slowly, discharged through each group of choke tube drain holes 5a, and fall into the bottom of the inner cavity of the upper sealing cylinder 3.

[0042] The lower side wall of the upper sealing cylinder 3 is connected with a drain elbow 6, the outlet of the drain elbow 6 is connected to the upper inlet of the converging tee 13 through an external thread joint 7, and the lower outlet of the converging tee 13 is connected with a drain interface 14. A small amount of well fluid collected at the bottom of the inner cavity of the upper sealing cylinder 3 flows out through the drain elbow 6, flows into the converging tee 13 through the external thread joint 7, and flows into the overflow collection pipe through the drain interface 14 below.

[0043] The lower end of the sealing bottom joint 20 of the lower blowout preventer unit is screwed to the upper port of the wellhead blowout preventer, and the lower choke tube 21 is screwed into the lower center screw hole of the sealing bottom joint 20 of the lower blowout preventer unit, and the lower end of the lower choke tube 21 is inserted into the upper port of the wellhead blowout preventer. The inner diameter of the lower choke tube 21 is also 0.2 to 0.4 mm larger than the outer diameter of the wire rope, which ensures that the wire rope can slide smoothly and reduces the leakage gap.

[0044] The upper end of the upper sealing cylinder of the lower blowout preventer unit is reduced in diameter to form a cone, and is screwed to the lower center screw hole of the sealing bottom joint 20 of the upper blowout preventer unit, so that the two-stage blowout preventer units are connected in series.

[0045] The top sealing gasket 2 is embedded in the upper port of the upper sealing cylinder 3 of the upper blowout prevention unit and is screwed with a blowout prevention cap 1. The center of the blowout prevention cap 1 is provided with a central hole for the wire rope to pass through. The middle periphery of the blowout prevention cap 1 is embedded with a blowout prevention cap sealing ring, which abuts against the inner wall of the upper port of the upper sealing cylinder 3 as the last seal of the device.

[0046] The upper end of the spray cap 1 is provided with a spray cap flange, and the outer periphery of the spray cap flange is provided with a square tenon or a hexagonal head, which is convenient for rotating the spray cap 1 to pre-tighten the spray cap sealing ring.

[0047] The upper sealing cylinder 3 of the upper blowout preventer unit is symmetrically provided with sealing cylinder support ears 4 for supporting the sky pulley. The base of the sky pulley is sleeved on the outer periphery of the upper sealing cylinder 3, and the bottom is supported on the sealing cylinder support ears 4 to support the bracket of the sky pulley. The sky pulley bracket extends upward so that the sky pulley groove is tangent to the axis of the device, and the wire rope bypasses the sky pulley and extends from the center hole of the blowout preventer cap 1 to the underground well.

[0048] During the operation, the wire rope first passes through the blowout preventer cap 1 and the top sealing gasket 2 to enter the upper choke tube 5 of the upper blowout preventer unit, then passes through the packing gland 8, the packing 9, and the double male joint 10 to enter the gland center pipe 17, and then continues to pass through the sealing gland 16, the rubber block 18 and the center hole of the sealing bottom joint 20, and then enters the upper choke tube 5 in the lower blowout preventer unit, then passes through the packing gland 8, the packing 9, the double male joint 10 to enter the gland center pipe 17, and then continues to pass through the sealing gland 16, the rubber block 18 and the center hole of the sealing bottom joint 20, and preferably passes through the lower choke tube 21 into the well.

[0049] The downhole liquid first passes through the gap between the lower choke tube 21 and the wire rope to form a decompression. After the decompression, a small amount of well liquid passes through the center hole of the rubber block of the lower sealing tube 19 in the lower blowout prevention unit, enters the drainage chamber 11 of the double male joint 10, and is discharged from the converging tee 13; an even smaller amount of well liquid passes through the packing 9 in the lower blowout prevention unit, enters the upper choke tube 5, and flows upward along the gap between the upper choke tube 5 and the wire rope. It flows out from the drainage holes 5a of each choke tube, falls into the bottom of the upper sealing tube 3, is discharged from the drainage elbow 6, and is merged into the converging tee 13 through the external thread joint 7, and finally enters the overflow collection pipe from the drainage interface 14. Then it passes through the various levels of decompression and sealing in the upper blowout prevention unit, and finally passes through the sealing of the top sealing pad 2 to ensure that no well liquid leaks from the top.

[0050] A boss is provided at the top center of the sealing gland 16, and the boss abuts against the bottom of the double male connector 10. When the double male connector 10 is screwed into the lower sealing cylinder 19, the sealing gland 16 can be pressed down to compress the rubber block 18. If there is no sign of leakage at the wellhead, the hydraulic pressure can be temporarily not applied to reduce the friction between the wire rope and the rubber block 18, the packing 9, etc., to extend their service life and reduce the downward resistance of the wire rope.

[0051] For oil and water wells with low formation pressure, one blowout preventer unit can be removed and only one set can be used.

[0052] The above description is only the preferred feasible embodiment of the utility model, which shows and describes the basic principle, main features and advantages of the utility model, but does not limit the scope of patent protection of the utility model. The technicians in this industry should understand that the utility model is not limited by the above embodiments. In addition to the above embodiments, the utility model can also have other implementation modes without departing from the spirit and scope of the utility model. The utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the utility model. The scope of protection required by the utility model is defined by the attached claims and their equivalents. The technical features not described in the utility model can be achieved by or using existing technologies, which will not be repeated here.

Claims

1. A multi-stage blowout prevention device for testing a high-pressure gas injection well, comprising two blowout prevention units connected in series, characterized in that: The two blowout prevention units respectively include a sealing bottom joint, which is screwed to the lower port of the lower sealing cylinder, a rubber block pressed on the sealing bottom joint is arranged in the lower sealing cylinder, and a sealing gland is arranged above the rubber block; a double male joint is screwed to the upper port of the lower sealing cylinder, and the center hole of the double male joint is connected with the center hole of the sealing gland, the rubber block and the sealing bottom joint; a drainage chamber with an enlarged diameter is arranged in the middle section of the center hole of the double male joint, a confluence tee is screwed to one side of the double male joint, and the middle inlet of the confluence tee is connected to the drainage chamber; an axial hydraulic channel is arranged along the axial direction of the double male joint, and the lower port of the axial hydraulic channel is connected to the space above the sealing gland; a hydraulic joint is screwed to the other side of the double male joint, and the inner port of the hydraulic joint is connected to the middle section of the axial hydraulic channel.

2. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 1, characterized in that: The upper periphery of the double male joint is screwed to the lower end of the upper sealing cylinder, the upper center of the double male joint is filled with packing, a packing gland is provided above the packing, and the space above the packing gland is communicated with the upper port of the axial hydraulic channel.

3. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 2, characterized in that: An upper sealing tube reduced diameter section is provided at the lower part of the upper sealing tube, and an upper choke tube extending upward is connected to the center of the packing gland, and the root of the upper choke tube passes through the central hole of the upper sealing tube reduced diameter section.

4. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 3, characterized in that: A plurality of choke tube drainage holes are evenly arranged along the height direction and the circumferential direction of the upper choke tube, a drainage elbow is connected to the lower side wall of the upper sealing cylinder, the outlet of the drainage elbow is connected to the upper inlet of the converging tee through an external thread joint, and the lower end outlet of the converging tee is connected to a drainage interface.

5. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 1, characterized in that: A gland center tube extending upward is provided at the top center of the sealing gland, and the gland center tube is inserted into the center hole of the double male connector.

6. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 1, characterized in that: The lower end of the sealing bottom joint of the lower blowout preventer unit is screwed to the upper port of the wellhead blowout preventer.

7. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 6, characterized in that: A lower flow-blocking pipe is screwed into the central screw hole at the lower end of the sealing bottom joint of the lower blowout prevention unit, and the lower end of the lower flow-blocking pipe is inserted into the upper port of the wellhead blowout prevention pipe.

8. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 1, characterized in that: The upper end of the upper sealing cylinder of the lower blowout prevention unit is reduced in diameter to form a cone, and is screwed to the lower end center screw hole of the sealing bottom joint of the upper blowout prevention unit.

9. The multi-stage blowout preventer for testing a high-pressure gas injection well according to claim 1, characterized in that: The outer periphery of the upper sealing cylinder of the upper blowout prevention unit is symmetrically provided with sealing cylinder support ears for supporting the sky pulley.

10. The multi-stage blowout preventer for testing a high-pressure gas injection well according to any one of claims 1 to 9, characterized in that: A top sealing gasket is embedded in the upper port of the upper sealing cylinder of the upper blowout prevention unit and a blowout prevention cap is screwed on it. A central hole for the steel wire rope to pass through is arranged at the center of the blowout prevention cap.

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