Hydraulic fracturing device with multiple sections mounted simultaneously and method of operation

Abstract

The application provides a serial connection array unit one-time installation multi-section hydraulic fracturing device and a working method, and belongs to the technical field of underground coal mine hydraulic fracturing. The device comprises a high-pressure pipe column arranged in a drilling hole. A plurality of groups of fracturing units comprising packers are arranged on the high-pressure pipe column at intervals. The groups of fracturing units comprising packers are arranged in a serial connection mode and are provided with a packer high-pressure rubber pipe. A fracturing flow metering control switch is arranged on the high-pressure pipe column between each group of fracturing units comprising packers. The device is simple to operate, friendly to the environment, low in labor intensity of workers, high in hydraulic fracturing efficiency, dense in hydraulic fracturing cracks, and can realize the effect of single-time installation dense hydraulic fracturing.

Description

Technical Field

[0001] This invention relates to a series of units for installing multiple hydraulic fracturing devices and their operating methods, belonging to the field of hydraulic fracturing technology in underground coal mines. Background Technology

[0002] Thick, hard roofs in underground coal mines are strong and structurally intact, making them difficult to collapse in a timely manner during mining, easily leading to large-area roof overhangs in the goaf. Large-scale roof overhangs and their sudden collapse can easily generate impact loads, large-area roof pressure, and storm surges. On-site engineering methods typically use explosive blasting, carbon dioxide blasting, and hydraulic fracturing to reduce the integrity of the hard roof, thereby promoting the safe and stable collapse of thick, hard roofs. Traditional manual blasting forcibly caving methods involve large amounts of work and explosives, are costly, have poor safety, and easily pollute underground air. Carbon dioxide blasting methods have disadvantages such as low efficiency, complex construction processes, cumbersome steps, high requirements for the goaf surface, and high cost. Hydraulic fracturing has significant advantages such as simple process, low disturbance, high safety, less work, large operating range, long control distance, low economic cost, and environmental friendliness, making it a widely used method for fracturing hard roofs. However, traditional hydraulic fracturing devices have many drawbacks due to structural limitations.

[0003] ① A single sealing device can only fracture a section within the range from the sealing device position to the bottom of the hole, and the location of the fracture development is uncontrollable.

[0004] ②Although the double sealing device can control the fracturing position between the two sealing devices, it is necessary to continuously adjust the fracturing position to achieve fracturing throughout the entire length of the borehole. The process is complex, the labor intensity of workers is high, and the time is long.

[0005] ③ To ensure effective sealing during high-pressure hydraulic fracturing, the double sealing device needs to be relatively long. This directly results in the distance between two adjacent fracturing sections during hydraulic fracturing in the borehole being greater than the length of one sealing device plus the length between the two sealing devices, making it impossible to achieve high-density fracturing in the borehole.

[0006] ④ If multiple sets of double sealing devices are connected in series in a borehole to cause cracking, the pressure relief caused by cracking at one location will lead to a decrease in pressure at other locations, preventing further cracking and resulting in insufficient crack development. Summary of the Invention

[0007] Technical Problem: The purpose of this invention is to address the problems of complex operation, low fracture development density, high labor intensity, and long operation time of current hydraulic fracturing devices and methods. It provides a series of interconnected units for installing multiple hydraulic fracturing devices and methods in a single operation. By utilizing a fracturing flow metering control switch and a series of interconnected fracturing units, it is possible to achieve automatic shut-off control with constant flow at multiple fracturing locations in the borehole, thereby achieving the effect of single-installation, dense multi-stage hydraulic fracturing.

[0008] To achieve the above technical objectives, the present invention provides a series unit for installing multiple hydraulic fracturing devices at one time. It includes a high-pressure tubing set in a borehole, with multiple fracturing units including sealing devices spaced apart on the high-pressure tubing. The multiple fracturing units including sealing devices are connected in series with high-pressure sealing hoses. Each fracturing unit including sealing device is provided with a fracturing flow metering and control switch on the high-pressure tubing.

[0009] The fracturing flow metering control switch includes a hollow outer shell structure, within which a switch valve core is installed. The quick-closing valve core includes a sealing plug. The outer shell structure comprises upper and lower parts: an upper housing and a lower housing. The sealing plug includes a conical structure at one end and a rod. The large end of the conical structure has an axially protruding visor. A conical hole matching the conical structure is provided between the upper housing and the conical structure, thereby controlling whether the inner cavity of the upper housing is open by the position of the conical structure. A sealing plug limiting plate is provided between the upper and lower housings. A sealing plug return spring is provided below the conical structure and on the top surface of the sealing plug limiting plate. The side of the sealing plug limiting plate is connected to the sealing plug. A sealing control device is provided between the conical structures at the ends. This device includes a sealing control clip, a sealing control clip spring, a transmission gear, and a pointed rack. The upper part of the sealing control clip has a buckle structure that matches the brim of the conical structure. The buckle structure is an F-shaped structure that can fix the brim of the sealing plug. The F-shaped structure has two fixing claws, one longer than the other. A rotating shaft is provided between the lower fixing claw and the upper housing, allowing the lower fixing claw to swing around the lever fulcrum of the rotating shaft. The lower end of the sealing control clip is connected to the side of the sealing plug limiting plate via the sealing control clip spring, providing thrust for the sealing control clip to rotate counterclockwise along the rotating shaft. The upper part of the pointed rack has a beveled structure with protrusions. The inclined structure of the pointed rack slides in contact with the gear rack. The lower half of the pointed rack is a gear rack set inside the lower housing. A propeller is fitted onto the rod of the sealing plug inside the lower housing. A sleeve connected to the rod is located at the center of the propeller. The end of the sleeve has external teeth, which are connected to the gear rack of the pointed rack through a transmission gear. In the initial state, the two fixing claws of the F-shaped structure of the sealing control card are locked onto the sealing plug cap, causing the sealing plug to compress the sealing plug return spring. At this time, the sealing plug leaves the conical hole, and the pointed rack is in the lowest position. When the flow rate drives the propeller to rotate the gear to reach the preset number of revolutions, it drives the pointed rack to move upward and uses the inclined surface to push the sealing control. The lower end of the card moves to the right, and under the lever action of the lower fixed claw with the rotation axis as the lever center, the upper end of the sealing control card moves to the left, releasing the sealing plug. The sealing plug moves forward under the action of the sealing plug return spring. At the same time, since the cap of the sealing plug is also a conical slope, it will push the sealing control card to continue to move to the left until the lower end of the cap of the sealing plug exceeds the upper end of the sealing control card and blocks the conical hole. Under the push action of the control card spring, the sealing control card rotates clockwise with the rotation axis as the lever center. The long fixed claw of the F-shaped structure at the front end of the sealing control card abuts against the lower end of the cap of the sealing plug, locking the sealing plug and making the sealing plug completely seal the channel.

[0010] The lower part of the propeller sleeve is provided with a propeller sealing plug limiting plate connected to the lower housing. The position of the sealing plug and the propeller is fixed by the propeller sealing plug limiting plate, so that the sealing plug and the propeller are always kept in the center position in the upper and lower housings. The transmission gear is fixed to the sealing plug limiting plate by the transmission gear shaft. The top of the propeller is provided with external teeth that mesh with the transmission gear. The transmission gear meshes with the gear rack of the lower half of the pointed rack.

[0011] Furthermore, each fracturing flow metering control switch has an inlet anti-clogging mesh cover at the connection between the upper housing and the high-pressure tubing, and an outlet anti-clogging mesh cover at the tail of the lower housing.

[0012] Furthermore, the lower and upper shells are movably connected, allowing relative rotation of 90° without disengagement. When the fracturing flow metering control switch is operational, the pointed rack engages with the transmission gear. When manual unsealing and resetting of the sealing plug is required, first remove the outlet anti-clogging screen. The lower shell rotates 10° counterclockwise relative to the upper shell. At this time, the pointed rack moves relative to the sealing control card spring and the transmission gear. During this process, only the pointed rack and the propeller sealing plug limit plate move relative to other components within the lower and upper shells. Simultaneously, the pointed rack disengages from the transmission gear. Manually advancing the pointed rack causes the lower protrusion of the sealing control card to move to the right under the push of the inclined surface of the pointed rack. The sealing control card rotates counterclockwise around the rotation axis as the lever center, thereby releasing the F-shaped fixing claw at the top of the sealing control card. The obstruction at the lower part of the sealing plug cap causes the sealing plug to disengage from the control of the sealing control card, allowing it to be pulled from the tail. Pulling the tail rod of the sealing plug compresses the sealing plug return spring, returning the sealing plug to its initial position and releasing the blockage of the channel. Simultaneously, by continuing to rotate the lower and upper housings counterclockwise to 90°, the inclined structure of the pointed rack disengages from the lower protrusion of the sealing control card. Under the action of the sealing control card spring, the sealing control card rotates clockwise to reset, using the rotation axis of the sealing control card as a lever fulcrum, and the F-shaped structure fixing claws re-engage the sealing plug cap. At this point, the pointed rack is pulled back to reset, and then the lower housing rotates 90° clockwise relative to the upper housing to reset, causing the pointed rack to re-engage with the transmission gear. The inclined structure of the pointed rack re-contacts the lower protrusion of the sealing control card, restoring the fracturing flow metering control switch to its initial state.

[0013] Furthermore, after the water flows through the high-pressure tubing into the fracturing flow metering control switch, it drives the propeller and transmission gear to rotate, and drives the pointed rack to move until it triggers the sealing control card to release and lock the sealing plug, thereby closing the fracturing flow metering control switch. The shape and size of the propeller and the tooth ratio between it and the transmission gear and the pointed rack are determined by the amount of water passing through the fracturing flow metering control switch.

[0014] A method for installing multiple hydraulic fracturing devices in a series of interconnected units, comprising the following steps:

[0015] 1) Drilling holes inside the rock mass using a drilling rig;

[0016] 2) Install the corresponding number of fracturing flow metering control switches and sealing devices on the high-pressure tubing according to the number of fracturing points in the borehole. Connect all the sealing devices in series through the high-pressure hoses of the sealing devices. Send the assembled multi-stage hydraulic fracturing device into the borehole. Inject water into all the sealing devices through the high-pressure hoses of the sealing devices to make them expand and seal the holes. Inject water through the high-pressure tubing and continuously pressurize it. The water flow flows through the tail end of the fracturing flow metering control switch into the cavity between the high-pressure tubing and the borehole wall between each sealing device.

[0017] 3) When the pressure inside the cavity between the plug, the high-pressure string and the borehole wall does not exceed the borehole wall cracking pressure at that location, after the water fills the cavity, the pressure in each cavity is equal before the borehole wall cracks, and it no longer flows through the plug.

[0018] 4) Continuous water injection and pressurization: when the pressure in the cavity between two plugs exceeds the borehole wall cracking pressure at that location, the borehole wall ruptures, and water flows continuously out through the fracturing flow metering control switch in the cavity at that location, entering the hydraulic fracturing cracks in the borehole wall and flowing continuously into the rock strata.

[0019] 5) Water flows through the high-pressure tubing into the fracturing flow metering control switch in the fracturing section of the borehole wall. Water flows into the lower housing from the borehole channel, driving the propeller to rotate. The propeller drives the gear to rotate, and the transmission gear drives the pointed rack to move upward. When the water flow reaches the maximum allowable flow of the fracturing flow metering control switch, the inclined structure of the pointed rack touches the sealing control card, causing the F-shaped structure fixing claw at the end of the sealing control card to release and lock the sealing plug, thereby closing the fracturing flow metering control switch.

[0020] 6) After the fracturing flow metering control switch at the location where the rock strata have been fractured is closed, continue to increase the water pressure in the high-pressure tubing until the high water pressure causes the borehole wall rock strata in another cavity to fracture. Repeat steps 1) and 2) until all sections separated by multiple plugs in the borehole hydraulically fracture the borehole wall rock strata, generating dense hydraulically fractured cracks at different locations in the borehole to facilitate subsequent gas extraction or rock breaking and tunneling.

[0021] 7) Remove the multi-stage hydraulic fracturing device from the borehole, manually reset each fracturing flow metering control switch, remove the outlet anti-clogging screen, rotate the lower housing counterclockwise by 10° relative to the upper housing to disengage the pointed rack from the transmission gear, push the pointed rack upwards to release the sealing control card from locking the sealing plug, and simultaneously pull down the sealing plug. Then rotate the lower housing counterclockwise by 90° to disengage the pointed rack from the transmission gear, and pull down the pointed rack to reset it. At this time, the sealing control card resets under the action of the sealing control card spring, re-locking the sealing plug. Finally, rotate the lower housing clockwise by 90° and replace the outlet anti-clogging screen to complete the reset of the fracturing flow metering control switch, ready for the next hydraulic fracturing use.

[0022] Furthermore, the fracturing flow metering control switch drives the propeller to rotate via water flow. The propeller drives the transmission gear to rotate, and the rotating gear drives the pointed rack to move forward. Under the push of the conical inclined surface at the head of the pointed rack, the protrusion at the rear of the sealing control card pushes the sealing control card to rotate counterclockwise along the rotating shaft, releasing the sealing plug to seal. During this process, the flow rate driving the propeller is determined by the number of times the propeller rotates, thus achieving the function of automatic sealing when the flow rate reaches the limit.

[0023] Furthermore, during fracturing, when water flows through the high-pressure tubing into the fracturing flow metering control switch, it enters the lower housing from the upper housing through the through-hole on the sealing plug limit plate and drives the propeller to rotate. The upper gear of the propeller drives the transmission gear to rotate, and the transmission gear pushes the pointed rack to move upward. The pointed rack pushes the lower part of the sealing control card to move to the right through its upper inclined surface, and the upper part of the sealing control card to move to the left. After the water flows through the fracturing flow metering control switch and reaches the set flow rate, the sealing control card unlocks the sealing plug. Under the action of the sealing plug return spring, the sealing plug moves upward to seal the water inlet in the upper housing. At the same time, the upper edge of the sealing control card abuts against the lower edge of the sealing plug cone head to lock the sealing plug, and the fracturing flow metering control switch is closed.

[0024] Beneficial effects: This invention provides a series of interconnected units for installing multiple hydraulic fracturing devices and methods in a single operation. It can automatically perform segmented hydraulic fracturing on the borehole wall. The method is simple to operate, environmentally friendly, reduces labor intensity for workers, and has high hydraulic fracturing efficiency and dense hydraulic fracturing fractures. By using a fracturing flow metering control switch and a series of interconnected fracturing units, it is possible to achieve automatic shut-off control of constant flow at multiple fracturing locations in the borehole, thereby achieving the effect of single installation and dense multi-segment hydraulic fracturing. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the multi-segment hydraulic fracturing device with series units installed at one time according to the present invention.

[0026] Figure 2(a) is a schematic diagram of the locked state when the fracturing flow metering control switch channel of the present invention is open;

[0027] Figure 2(b) is a schematic diagram of the release of the sealing plug by the sealing control card in the fracturing flow metering control switch of the present invention;

[0028] Figure 2(c) is a schematic diagram of the locked state when the fracturing flow metering control switch channel of the present invention is closed.

[0029] In the diagram: 1-Drill hole; 2-Sealing device; 3-Sealing device high-pressure hose; 4-High-pressure tubing string; 5-Water flow; 6-Fracturing flow metering control switch; 61-Sealing control card; 62-Sealing control card spring; 63-Drive gear; 631-Drive gear shaft; 64-Pointed rack; 651-Inlet anti-clogging screen; 652-Outlet anti-clogging screen; 66-Sealing plug; 67-Sealing plug return spring; 68-Sealing plug limit plate; 69-Propeller; 610-Propeller sealing plug limit plate; 601-Lower housing; 602-Upper housing; 611-Rotating shaft Detailed Implementation

[0030] An embodiment of the present invention will be further described below with reference to the accompanying drawings:

[0031] like Figure 1 As shown, a series unit for installing multiple hydraulic fracturing devices at one time includes a high-pressure tubing string 4 installed in a borehole 1. Multiple fracturing units including sealing devices 2 are spaced apart on the high-pressure tubing string 4. The multiple fracturing units including sealing devices 2 are connected in series and high-pressure hoses 3 are connected between the sealing devices. Each fracturing unit including sealing devices 2 is provided with a fracturing flow metering and control switch 6 on the high-pressure tubing string 4.

[0032] The fracturing flow metering control switch 6 includes a hollow outer shell structure, within which a switch valve core is installed. The quick-closing valve core includes a sealing plug 66. The outer shell structure comprises upper and lower parts: an upper housing 602 and a lower housing 601. The sealing plug 66 includes a conical structure at one end and a rod. The large end of the conical structure has an axially protruding brim. A conical hole matching the conical structure is provided between the upper housing 602 and the conical structure, thereby controlling whether the inner cavity of the upper housing 602 is open by controlling the position of the conical structure. A sealing plug limiting plate 68 is provided between the upper housing 602 and the lower housing 601. A sealing plug return spring 67 is provided below the conical structure and on the top surface of the sealing plug limiting plate 68. The side of the sealing plug limiting plate 68 and the end of the sealing plug 66 are connected. A sealing control device is provided between the conical structures. The sealing control device includes a sealing control card 61, a sealing control card spring 62, a transmission gear 63, and a pointed rack 64. The upper part of the sealing control card 61 is provided with a buckle structure that matches the brim of the conical structure. The buckle structure is an F-shaped structure that can fix the brim of the sealing plug 66. The F-shaped structure has two fixing claws, one longer than the other. A rotating shaft 611 is provided between the lower fixing claw and the upper housing 602, so that the lower fixing claw swings around the lever fulcrum of the rotating shaft 611. The lower end of the sealing control card 61 is connected to the side of the sealing plug limiting plate 68 through the sealing control card spring 62, which provides thrust for the sealing control card 61 to rotate counterclockwise along the rotating shaft (611). The upper part of the pointed rack 64 is a sloping structure with protrusions and a pointed tip. The inclined structure of the rack 64 makes sliding contact. The lower half of the pointed rack 64 is a gear rack set inside the lower housing 601. A propeller 69 is sleeved on the rod of the sealing plug 66 inside the lower housing 601. A sleeve connected to the rod is provided at the center of the propeller 69. The end of the sleeve is provided with external teeth, which are connected to the gear rack of the pointed rack 64 through the transmission gear 63. In the initial state, the two fixing claws of the F-shaped structure of the sealing control card 61 are locked on the cap of the sealing plug 66, causing the sealing plug 66 to compress the sealing plug return spring 67. At this time, the sealing plug 66 leaves the conical hole, and the pointed rack 64 is in the lowest position. When the flow pushes the propeller 69 to drive the gear 63 to rotate to the preset number of revolutions, it drives the pointed rack 64 to move upward and uses the inclined surface to push the sealing control card. The lower end of 61 moves to the right, and under the lever action of the lower fixed claw with the rotating shaft 611 as the lever center, the upper end of the sealing control card 61 moves to the left, releasing the sealing plug 66. The sealing plug 66 moves forward under the action of the sealing plug return spring 67. At the same time, since the cap of the sealing plug 66 is also a conical slope, it will push the sealing control card 61 to continue to move to the left until the lower end of the cap of the sealing plug 66 exceeds the upper end of the sealing control card 61 to block the conical hole. Under the push action of the control card spring 62, the sealing control card 61 rotates clockwise with the rotating shaft 611 as the lever center. The long fixed claw of the F-shaped structure at the front end of the sealing control card 61 abuts against the lower end of the cap of the sealing plug 66, locking the sealing plug 66 and making the sealing plug 66 completely seal the channel.

[0033] The lower part of the sleeve of the propeller 69 is provided with a propeller sealing plug limiting plate 610 connected to the lower housing 601. The position of the sealing plug 66 and the propeller 69 is fixed by the propeller sealing plug limiting plate 610, so that the sealing plug 66 and the propeller 69 are always kept in the center position in the upper housing 602 and the lower housing 601. The transmission gear 63 is fixed on the sealing plug limiting plate 68 through the transmission gear shaft 631. The top of the propeller 69 is provided with external teeth that mesh with the transmission gear 63. The transmission gear 63 meshes with the gear rack of the lower half of the pointed rack 64.

[0034] Each fracturing flow metering control switch 6 has an inlet anti-clogging mesh cover 651 at the connection between the upper housing 602 and the high-pressure tubing 4, and an outlet anti-clogging mesh cover 652 at the tail of the lower housing 601.

[0035] As shown in Figures 2(a), 2(b), and 2(c), the lower housing 601 and the upper housing 602 are movably connected, allowing them to rotate relative to each other by 90° without disengaging. When the fracturing flow metering control switch 6 is in operation, the pointed rack 64 engages with the transmission gear 63. When it is necessary to manually open and reset the sealing plug 66, first remove the outlet anti-clogging screen (652), and rotate the lower housing 601 counterclockwise by 10° relative to the upper housing 602. At this time, the pointed rack... The rack 64 moves relative to the sealing control card spring 62 and the transmission gear 63. During this process, only the rack 64 and the propeller sealing plug limiting plate 610 move relative to other components in the lower housing 601 and upper housing 602. At the same time, the rack 64 disengages from the transmission gear 63. Manually pushing the rack 64 forward causes the lower protrusion of the sealing control card (61) to move to the right under the push of the inclined surface of the rack 64. The sealing control card (61) rotates counterclockwise around the rotating shaft (611) as the lever center. The F-shaped fixing claw at the top of the sealing control card 61 releases its obstruction on the lower part of the cap of the sealing plug 66, allowing the sealing plug 66 to disengage from the control of the sealing control card 61 and be pulled from the tail. Pulling the tail rod of the sealing plug 66 compresses the sealing plug return spring 67, returning the sealing plug 66 to its initial position and releasing the blockage of the passage. Simultaneously, by continuing to rotate the lower housing 601 and upper housing 602 counterclockwise to 90°, the inclined structure of the pointed rack 64 disengages from the lower protrusion of the sealing control card 61, and the sealing control card 61... Under the action of the sealing control card spring 62, the sealing control card 61 rotates clockwise to reset with the rotating shaft 611 of the sealing control card 61 as the lever fulcrum, so that the F-shaped structure fixing claw can lock the cap of the sealing plug 66 again; at this time, the pointed rack 64 is pulled back to reset, and then the lower housing 601 rotates 90° clockwise relative to the upper housing 602 to reset, so that the pointed rack 64 and the transmission gear 63 re-mesh, and the inclined structure of the pointed rack 64 re-contacts the lower protrusion of the sealing control card 61, so that the fracturing flow metering control switch is reset to initialization.

[0036] Water flow 5 enters the fracturing flow metering control switch 6 through the high-pressure tubing 4, driving the propeller 69 and the transmission gear 63 to rotate, and driving the pointed rack 64 to move until it triggers the sealing control card 61 to release and lock the sealing plug 66, thereby closing the fracturing flow metering control switch 6. The shape and size of the propeller 69 and the tooth ratio between it and the transmission gear 63 and the pointed rack 64 are determined by the water volume passing through the fracturing flow metering control switch 6.

[0037] The single-installation multi-segment hydraulic fracturing construction process involved in this embodiment includes the following steps:

[0038] 1) Drilling hole 1 inside the rock mass using a drilling rig;

[0039] 2) Connect a series of fracturing units in series and connect the high-pressure hose 3 of the sealing device. Send the assembled hydraulic fracturing device into the borehole 1. Inject water into the sealing device 2 through the high-pressure hose 3 to make it expand and seal the borehole. Inject water through the high-pressure tubing 4. The water flow 5 flows into the cavity between the sealing device 2, the high-pressure tubing 4 and the borehole wall of the borehole 1 through the fracturing flow metering control switch 6.

[0040] 3) When the pressure inside the cavity between the plug 2, the high-pressure string 4 and the borehole wall of borehole 1 does not exceed the cracking pressure of the borehole wall at that position, the water flow 5 will no longer flow through the plug 2 after filling the cavity.

[0041] 4) When the pressure inside the cavity between the plug 2, the high-pressure tubing 4 and the borehole wall of borehole 1 at a certain location exceeds the cracking pressure of the borehole wall at that location, the water flow 5 continues to flow through the fracturing flow metering control switch 6 to achieve fracturing of the rock strata at that location.

[0042] 5) After the water flow 5 enters the fracturing flow metering control switch 6 through the high-pressure tubing 4, it drives the propeller 69 and the transmission gear 63 to rotate, and drives the pointed rack 64 to move. When the water flow reaches the maximum allowable flow of the fracturing flow metering control switch 6, the pointed rack 64 touches the sealing control card 61 to release and lock the sealing plug 66, thereby closing the fracturing flow metering control switch 6.

[0043] 6) After the fracturing flow metering control switch 6 of the rock stratum that has been fractured in step 5) is closed, continue to increase the water pressure in the high pressure tubing 4 until the water pressure of the high pressure water flow 5 reaches the fracturing pressure of the rock stratum at the next location. Repeat steps (4) and (5) until the hydraulic fracturing of the rock stratum at all locations of borehole 1 is completed, and dense hydraulic fracturing cracks are generated at different locations of the borehole.

[0044] 7) When resetting the fracturing flow metering control switch 6, first remove the outlet anti-clogging screen 652, rotate the lower housing (601) counterclockwise by 10° relative to the upper housing (602) to disengage the pointed rack (64) from the transmission gear (63), push the pointed rack 64 upward to release the sealing control card 61 from locking the sealing plug 66, and pull down the sealing plug 66. Then rotate the lower housing 601 counterclockwise by 90° to disengage the pointed rack 64 from the transmission gear 63, and pull down the pointed rack 64 to reset it. At this time, the sealing control card 61 is reset under the action of the sealing control card spring 62 to lock the sealing plug 66 again. Finally, rotate the lower housing 601 clockwise by 90° and install the outlet anti-clogging screen 652 to complete the reset of the fracturing flow metering control switch 6, in preparation for the next hydraulic fracturing.

[0045] The fracturing flow metering control switch 6 drives the propeller 69 to rotate via the water flow. The propeller 69 drives the transmission gear 63 to rotate. The rotation of the transmission gear 63 drives the pointed rack 64 to move forward. Under the push of the conical inclined surface at the head of the pointed rack 64, the protrusion at the rear of the sealing control card 61 will push the sealing control card 61 to rotate counterclockwise along the rotation axis 611, releasing the sealing plug 66 to seal. During this process, the flow rate of the propeller 69 is determined by the number of rotations of the propeller 69, thereby achieving the function of automatic sealing when the flow rate reaches the limit.

[0046] When water flow 5 enters the fracturing flow metering control switch 6 through the high-pressure tubing string 4 during fracturing, it enters the lower housing 601 through the through hole on the sealing plug limiting plate 68 from the upper housing 602 and drives the propeller 69 to rotate. The upper gear of the propeller 69 drives the transmission gear 63 to rotate, and the transmission gear 63 pushes the pointed rack 64 to move upward. The pointed rack 64 pushes the lower part of the sealing control card 61 to move to the right through its upper inclined surface, and the upper part of the sealing control card 61 moves to the left. After the water flow 5 reaches the set flow rate through the fracturing flow metering control switch 6, the sealing control card 61 unlocks the sealing plug 66. Under the action of the sealing plug return spring 67, the sealing plug 66 moves upward to seal the water inlet in the upper housing 602. At the same time, the upper edge of the sealing control card 61 abuts against the lower edge of the conical head of the sealing plug 66 to lock the sealing plug 66, and the fracturing flow metering control switch 6 closes.

Claims

1. A series of units for simultaneous installation of multiple hydraulic fracturing devices, characterized in that: It includes a high-pressure tubing string (4) installed in the borehole (1), and multiple sets of fracturing units including sealing devices (2) are spaced apart on the high-pressure tubing string (4). The multiple sets of fracturing units including sealing devices (2) are connected in series and a sealing device high-pressure hose (3) is provided between them. Each set of fracturing units including sealing devices (2) is provided with a fracturing flow metering control switch (6) on the high-pressure tubing string (4). The fracturing flow metering control switch (6) includes a hollow outer shell structure, and a switch valve core is provided inside the outer shell structure. The switch valve core includes a sealing plug (66). The outer shell structure includes upper and lower parts, the upper part being an upper shell (602) and the lower part being a lower shell (601). The sealing plug (66) includes a conical structure at the end and a rod. The large end of the conical structure is provided with an axially protruding brim. A conical hole matching the conical structure is provided between the upper shell (602) and the conical structure, thereby controlling whether the inner cavity of the upper shell (602) is open by the position of the conical structure; the upper shell (601) A sealing plug limiting plate (68) is provided between the 02) and the lower shell (601). A sealing plug return spring (67) is provided between the bottom of the conical structure and the top surface of the sealing plug limiting plate (68). A sealing control device is provided between the side of the sealing plug limiting plate (68) and the conical structure at the end of the sealing plug (66). The sealing control device includes a sealing control card (61), a sealing control card spring (62), a transmission gear (63), and a pointed rack (64). The upper part of the sealing control card (61) is provided with a buckle structure that matches the cap of the conical structure. The buckle structure is capable of fixing the sealing plug (66). 6) The F-shaped structure of the brim has two fixing claws, one longer than the other. The fixing claw at the lower end is connected to the upper housing (602) by a rotating shaft (611), which allows the fixing claw at the lower end to swing around the lever fulcrum of the rotating shaft (611). The lower end of the sealing control card (61) is connected to the side of the sealing plug limiting plate (68) through the sealing control card spring (62) to prevent the sealing control card (61) from shifting. The upper half of the pointed rack (64) is a sloping structure, and the protrusion slides in contact with the sloping structure of the pointed rack (64). The lower half of the pointed rack (64) is set in the lower housing. The gear rack inside (601), the rod of the sealing plug (66) inside the lower housing (601) is fitted with a propeller (69), the center of the propeller (69) is provided with a sleeve connected to the rod, the end of the sleeve is provided with external teeth, the external teeth are connected to the gear rack of the pointed rack (64) through the transmission gear (63); in the initial state, the two fixed claws of the F-shaped structure of the sealing control card (61) are locked on the cap of the sealing plug (66), so that the sealing plug (66) compresses the sealing plug return spring (67), at this time the sealing plug (66) leaves the conical hole, and the pointed rack (64) is located at the lowest position;When the flow rate drives the propeller (69) to rotate the transmission gear (63) to a preset number of revolutions, it drives the pointed rack (64) to move upward and uses the inclined plane to push the lower end of the sealing control card (61) to move to the right. Under the lever action of the lower fixed claw with the rotating shaft (611) as the lever center, the upper end of the sealing control card (61) moves to the left, releasing the sealing plug (66). The sealing plug (66) moves forward under the action of the sealing plug return spring (67). At the same time, due to the sealing plug (66) The brim of the cap is also a conical slope, which will push the sealing control card (61) to continue to move to the left until the lower end of the brim of the sealing plug (66) exceeds the upper end of the sealing control card (61) to block the conical hole. Under the pushing action of the control card spring (62), the sealing control card (61) rotates clockwise around the rotating shaft (611). The long fixing claw of the F-shaped structure at the front end of the sealing control card (61) abuts against the lower end of the brim of the sealing plug (66), which locks the sealing plug (66) and makes the sealing plug (66) completely seal the channel. The lower part of the sleeve of the propeller (69) is provided with a propeller sealing plug limiting plate (610) connected to the lower housing (601). The sealing plug (66) and the propeller (69) are fixed by the propeller sealing plug limiting plate (610) so that the sealing plug (66) and the propeller (69) are always kept in the center position in the upper housing (602) and the lower housing (601). The transmission gear (63) is fixed on the sealing plug limiting plate (68) through the transmission gear shaft (631). The top of the propeller (69) is provided with external teeth that mesh with the transmission gear (63). The transmission gear (63) meshes with the gear rack of the lower half of the pointed rack (64).

2. The series-connected multi-stage hydraulic fracturing device according to claim 1, characterized in that: Each of the fracturing flow metering control switches (6) has an inlet anti-clogging mesh cover (651) at the connection between the upper housing (602) and the high-pressure tubing (4), and an outlet anti-clogging mesh cover (652) at the tail of the lower housing (601).

3. The series-connected multi-stage hydraulic fracturing device according to claim 1, characterized in that: The lower housing (601) and the upper housing (602) are movably connected, and the lower housing (601) and the upper housing (602) are allowed to rotate relative to each other by 90° without disengaging; when the fracturing flow metering control switch (6) is working, the pointed rack (64) meshes with the transmission gear (63). When it is necessary to manually open the sealing plug (66) and reset it, the lower housing (601) rotates counterclockwise by 10° relative to the upper housing (602). At this time, the pointed rack (64) meshes with the sealing plug. The control card spring (62) and the transmission gear (63) move relative to each other. During this process, only the rack (64) and the propeller sealing plug limiting plate (610) move relative to other components inside the lower housing (601) and upper housing (602). At the same time, the rack (64) disengages from the transmission gear (63), and the F-shaped fixing claw at the top of the sealing control card (61) releases its obstruction on the lower part of the sealing plug (66) cap, causing the sealing plug (66) to disengage from the control of the sealing control card (61). It can be pulled from the tail; pulling the tail rod of the sealing plug (66) and compressing the sealing plug return spring (67) will return the sealing plug (66) to its initial position, releasing the blockage of the channel. At the same time, by continuing to rotate the lower housing (601) and the upper housing (602) counterclockwise to 90°, the inclined structure of the pointed rack (64) will disengage from the lower protrusion of the sealing control card (61). Under the action of the sealing control card spring (62), the sealing control card (61) will be closed. The rotating shaft (611) is reset as a lever fulcrum, and the F-shaped structure fixing claw is locked onto the cap of the sealing plug (66) again. At this time, the pointed rack (64) is pulled back to reset it. Then the lower housing (601) is rotated 90° clockwise relative to the upper housing (602) to reset it, so that the pointed rack (64) and the transmission gear (63) re-mesh. The inclined structure of the pointed rack (64) re-contacts the lower protrusion of the sealing control card (61), so that the fracturing flow metering control switch is reset to initialization.

4. The series-connected multi-stage hydraulic fracturing device according to claim 1, characterized in that: Water flow (5) enters the fracturing flow metering control switch (6) through the high-pressure tubing (4), driving the propeller (69) and transmission gear (63) to rotate, and driving the pointed rack (64) to move until it triggers the sealing control card (61) to release and lock the sealing plug (66), thereby closing the fracturing flow metering control switch (6). The shape and size of the propeller (69) and the tooth ratio between it and the transmission gear (63) and the pointed rack (64) are determined by the amount of water passing through the fracturing flow metering control switch (6).

5. A method for operating a multi-stage hydraulic fracturing device installed in a series of units according to claim 1, characterized in that... The steps are as follows: 1) Drilling holes inside the rock mass using a drilling rig (1); 2) Install the corresponding number of fracturing flow metering control switches (6) and sealing devices (2) on the high-pressure tubing string (4) according to the number of fracturing points in the borehole. Connect all sealing devices (2) through the sealing device high-pressure hose (3). Send the assembled multi-segment hydraulic fracturing device into the borehole (1). Inject water into all sealing devices (2) through the sealing device high-pressure hose (3) to make them expand and seal the holes. Inject water through the high-pressure tubing string (4) and continuously pressurize. The water flow (5) flows into the cavity between the high-pressure tubing string (4) and the borehole wall (1) between each sealing device (2) through the tail end of the fracturing flow metering control switch (6). 3) When the pressure inside the cavity of the sealing device (2), the high-pressure tubing (4) and the borehole (1) does not exceed the cracking pressure of the borehole (1) wall, after the water flow (5) fills the cavity, the pressure of each cavity is equal before the borehole wall is cracked, and it no longer flows through the sealing device (2). 4) Continuous water injection and pressurization. When the pressure in the cavity between two sealing devices (2) exceeds the cracking pressure of the borehole wall (1) at that location, the borehole wall will rupture, and the water flow (5) will continuously flow out through the fracturing flow metering control switch (6) in the cavity at that location and enter the hydraulic fracturing crack in the borehole wall to flow continuously into the rock strata. 5) Water flow (5) enters the fracturing flow metering control switch (6) in the fracturing section of the borehole wall through the high-pressure tubing (4). Water flow enters the lower shell (601) from the borehole and drives the propeller (69) to rotate. The propeller (69) drives the gear (63) to rotate. The transmission gear (63) drives the pointed rack (64) to move upward. When the water flow reaches the maximum allowable flow of the fracturing flow metering control switch (6), the inclined structure of the pointed rack (64) touches the sealing control card (61), causing the F-shaped structure fixing claw at the end of the sealing control card (61) to release and lock the sealing plug (66), thereby closing the fracturing flow metering control switch (6). 6) After the fracturing flow metering control switch (6) at the location where the rock strata have been fractured is closed, continue to increase the water pressure in the high-pressure tubing (4) until the high-pressure water flow (5) causes the borehole wall rock strata in another cavity to be fractured. Repeat steps 4) and 5) until all sections in the borehole (1) separated by multiple sealing devices (2) have hydraulically fractured the borehole wall rock strata and have been subsequently extracted by gas extraction or rock breaking and excavation. 7) Remove the multi-stage hydraulic fracturing device from the borehole (1), manually reset each fracturing flow metering control switch (6), remove the outlet anti-clogging screen (652), push the pointed rack (64) upwards to release the sealing control card (61) from locking the sealing plug (66), and pull down the sealing plug (66). Then rotate the lower housing (601) counterclockwise by 90° to disengage the pointed rack (64) from the transmission gear (63), and pull down the pointed rack (64) to reset it. At this time, the sealing control card (61) resets under the action of the sealing control card spring (62) to lock the sealing plug (66) again. Finally, rotate the lower housing (601) clockwise by 90° and replace the outlet anti-clogging screen (652) to complete the reset of the fracturing flow metering control switch (6) for the next hydraulic fracturing.

6. The working method according to claim 5, characterized in that: The fracturing flow metering control switch (6) drives the propeller (69) to rotate through the water flow. The propeller (69) drives the transmission gear (63) to rotate. The rotating gear (63) drives the rack (64) to move forward. Under the push of the conical inclined surface at the head of the rotating gear (63), the protrusion at the rear of the sealing control card (61) will push the sealing control card (61) to rotate counterclockwise along the rotating shaft (611), releasing the sealing plug (66) to seal. During this process, the flow rate of the propeller (69) is determined by the number of rotations of the propeller (69), thereby achieving the function of automatic sealing when the flow rate reaches the limit.

7. The working method according to claim 5, characterized in that: When water flow (5) enters the fracturing flow metering control switch (6) through the high-pressure tubing string (4) during fracturing, it enters the lower housing (601) through the through hole on the sealing plug limiting plate (68) from the upper housing (602) and drives the propeller (69) to rotate. The upper gear of the propeller (69) drives the transmission gear (63) to rotate. The transmission gear (63) pushes the pointed rack (64) to move upward. The pointed rack (64) pushes the lower part of the sealing control card (61) to move to the right through its upper inclined surface. When the water flow (5) passes through the fracturing flow metering control switch (6) and reaches the set flow rate, the sealing control card (61) unlocks the sealing plug (66). Under the action of the sealing plug reset spring (67), the sealing plug (66) moves upward to seal the water inlet in the upper shell (602). At the same time, the upper edge of the sealing control card (61) abuts against the lower edge of the cone head of the sealing plug (66) to lock the sealing plug (66) and the fracturing flow metering control switch (6) closes.

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