New bridge plug setting device for secondary segmented fracturing of coal measure gas horizontal well

Abstract

The application discloses a novel bridge plug setting device for secondary segmented fracturing of a coal measure gas horizontal well, belongs to the technical field of coal measure gas extraction, and aims to solve the problems of inaccurate positioning, limited displacement and poor transformation effect of the existing secondary fracturing technology. The device comprises a bridge plug setting device, a fracturing fluid migration bin and a stroke type piston pressurizing device which are coaxially nested. The bridge plug setting device realizes accurate setting anchoring and annular sealing of a target layer. The fracturing fluid migration bin constructs a controllable migration channel of the fracturing fluid. The stroke type piston pressurizing device realizes stroke type pressurization injection of the fracturing fluid through linkage of pistons. The application can realize accurate positioning, large-displacement high-pressure transformation of the secondary fracturing of the coal measure gas horizontal well, and the soluble structure does not need to be drilled and ground, so that the construction efficiency is high, the adaptability is strong, and the secondary fracturing stimulation effect is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane extraction technology, specifically relating to a novel bridge plug setting device for secondary staged fracturing of coalbed methane horizontal wells. Background Technology

[0002] Coal-series gas is a clean, low-carbon, unconventional natural gas resource. Its efficient development is of great significance for optimizing my country's energy structure and ensuring safe coal mine production. Horizontal well staged fracturing is currently the mainstream technology for coal-series gas reservoir stimulation. However, due to factors such as the strong heterogeneity of coal-series reservoirs, complex geostress, and uneven initial staged fracturing range, many coal-series gas horizontal wells experience low single-well gas production and rapid decline after commissioning. There are "residual resources" in the reservoirs that have not been effectively stimulated. Therefore, secondary staged fracturing is often used to repeatedly stimulate the reservoirs to tap the potential for increased production.

[0003] Currently, the mainstream methods for secondary staged fracturing in horizontal wells of coal-bearing gas include "coiled tubing + bottom seal drag" fracturing, temporary plugging and diversion fracturing, and nitrogen foam fracturing. Temporary plugging and diversion fracturing and nitrogen foam fracturing are mostly based on the "coiled tubing + bottom seal drag" process. All of the above processes have obvious defects: "coiled tubing + bottom seal drag" fracturing has limited flow capacity, low operating efficiency, high cost, and limited reservoir stimulation range; temporary plugging and diversion fracturing is prone to further fracturing of coal and rock when the coal body structure is broken, generating a large amount of coal dust, which aggravates the blockage in the near-wellbore area, and has poor fracturing adaptability; nitrogen foam fracturing is prone to inducing coal and rock fracturing and coal dust blockage, and in areas with deep coal seams and high in-situ stress, the breaking and filtration loss of foam fluid is difficult to control, and the scale of secondary stimulation is limited.

[0004] Meanwhile, while traditional pump-driven bridge plug technology can achieve high-volume hydraulic fracturing, it cannot meet the technical requirements of secondary stage fracturing in coal-bearing gas horizontal wells. Existing technologies all suffer from problems such as inaccurate secondary stage fracturing location, difficulty in adapting to the fracturing reservoir, small fracturing volume, severe filtration loss, and poor production enhancement. Therefore, there is an urgent need to develop a new type of bridge plug setting device adapted to secondary stage fracturing in coal-bearing gas horizontal wells, to achieve precise positioning of secondary fracturing, large-volume differentiated modification, and improve fracture length and fracture support effect. Summary of the Invention

[0005] This invention addresses the problems of inaccurate reservoir stimulation location, small displacement, and short fracture proppant length in existing secondary fracturing technologies for horizontal coal-bearing gas wells, which ultimately lead to poor secondary fracturing results. It provides a novel bridge plug setting device for secondary fracturing in horizontal coal-bearing gas wells. This device can achieve "double setting" by pumping fracturing fluid to the target double-setting segment of the horizontal well. Combined with smooth casing fracturing, it achieves the goals of "precise positioning, efficient stimulation, and increased production and efficiency" in secondary fracturing.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a novel bridge plug setting device for secondary staged fracturing of coalbed methane horizontal wells, comprising a bridge plug setting device, a fracturing fluid transport chamber and a stroke-type piston pressurizing device, wherein the fracturing fluid transport chamber is located inside the bridge plug setting device and the stroke-type piston pressurizing device is located inside the fracturing fluid transport chamber. The bridge plug setting device is used to accurately position the target double-setting section for secondary fracturing in the casing of a coal-bearing gas horizontal well, so that hydraulic fracturing can directly act on the target double-setting section. The fracturing fluid transport chamber is used to provide a channel for fracturing fluid to be transported from the casing in a stroke manner to the target section of the horizontal well with dual setting; The stroke-type piston pressurization device is used to control the pressure between the horizontal well casing and the double-set target section by pumping pressure, so as to achieve the effect of pumping fracturing fluid into the double-set target section and stroke-type pressurization.

[0007] Furthermore, the bridge plug setting device includes a first cylinder arranged along the front-rear direction with its centerline, and a second cylinder arranged coaxially inside the first cylinder. The front and rear ends of both the first and second cylinders are provided with first annular blocking plates. A sealed first annular cavity is formed between the inner circle of the first cylinder and the outer circle of the second cylinder. The middle part of the first annular cavity is provided with a power unit, an annular power piston, a power rod, an annular cone, a slip, a locking pin, and a sealing unit in sequence from front to back. The power unit is filled with gunpowder, and the rear conical surface of the annular cone is adapted to the inner inclined surface of the slip. The pressure-bearing components in the slip and the sealing unit are made of soluble magnesium alloy, which can be dissolved 10 hours after the fracturing is completed.

[0008] Furthermore, the fracturing fluid transport chamber includes a third cylinder coaxially arranged inside the second cylinder. The front and rear ends of both the second and third cylinders are provided with second annular blocking plates. A sealed second annular cavity is formed between the inner circle of the second cylinder and the outer circle of the third cylinder. The outer circle of the third cylinder is slidably connected to a first front slide cylinder and a first rear slide cylinder. A front annular piston plate located in front of the first front slide cylinder is slidably sealed on the front side of the second annular cavity. A rear annular piston plate located behind the first rear slide cylinder is slidably sealed on the rear side of the second annular cavity. At least two front fixed valve holes are arranged in a circumferential array on the front side of the first front slide cylinder covering surface on the cylinder wall of the third cylinder. At least two first front guide holes are arranged in a circumferential array on the rear side of the first front slide cylinder covering surface on the cylinder wall of the third cylinder. A front movable valve hole corresponding to the front fixed valve hole is opened on the front side of the first front slide cylinder. The third cylinder has at least two rear fixed valve holes arranged in a circumferential array on the rear side of the first rear sliding cylinder covering surface, and at least two first rear guide holes arranged in a circumferential array on the front side of the first rear sliding cylinder covering surface. The first rear sliding cylinder has a rear movable valve hole that corresponds one-to-one with the rear fixed valve holes on the front side. A front radial rod is provided inside the first front guide hole, which is arranged radially along the third cylinder. The front radial rod is fixedly connected to the first front slide cylinder. The outer end of the front radial rod passes through the first front slide cylinder and is connected to the rear side of the front annular piston plate through the front axial rod. A rear radial rod is provided inside the first rear guide hole, which is arranged radially along the third cylinder. The rear radial rod is fixedly connected to the first rear slide cylinder. The outer end of the rear radial rod passes through the first rear slide cylinder and is connected to the front side of the rear annular piston plate through the rear axial rod. The inner ends of both the front and rear radial rods are connected to the stroke-type piston pressurization device.

[0009] Furthermore, the stroke-type piston pressurizing device includes a partition plate fixedly disposed in the middle of the third cylinder, a fourth cylinder coaxially disposed in the front half of the third cylinder fixedly disposed on the front side of the partition plate, and a fifth cylinder coaxially disposed in the rear half of the third cylinder fixedly disposed on the rear side of the partition plate. The fourth cylinder has a front cylinder arranged coaxially on its inner circle. The rear end of the front cylinder is fixedly connected to the front side of the partition plate. The front piston is slidably arranged inside the front cylinder. The fifth cylinder has a rear cylinder arranged coaxially on its inner circle. The front end of the rear cylinder is fixedly connected to the rear side of the partition plate. The rear piston is slidably arranged inside the rear cylinder. The front piston and the rear piston are connected by a linkage rod that passes through the partition. A front spring is sleeved on the linkage rod between the rear side of the front piston and the front side of the partition, and a rear spring is sleeved on the linkage rod between the front side of the rear piston and the rear side of the partition. The fourth cylinder and the front cylinder are provided with second front guide holes that correspond one-to-one with the first front guide holes. The outer circle of the fourth cylinder is provided with a sealing second front slide cylinder that covers the second front guide holes. The front radial rod is fixedly connected to the second front slide cylinder and passes through the second front guide hole. The rear side of the front piston is connected to the inner end of the front radial rod through the front drive rod. The fifth cylinder and the rear cylinder are provided with second rear guide holes that correspond one-to-one with the first rear guide holes. The outer circle of the fifth cylinder is provided with a second rear slide cylinder that covers and seals the second rear guide holes. The rear radial rod is fixedly connected to the second rear slide cylinder and passes through the second rear guide hole. The front side of the rear piston is connected to the inner end of the rear radial rod through a rear drive rod.

[0010] Furthermore, the annular surface area of ​​the front annular piston plate is larger than the circular surface area of ​​the front piston, and the circular surface area of ​​the front piston is larger than the circular surface area of ​​the rear piston.

[0011] Furthermore, the front of the power unit is connected to a wire that connects to the ground-based electronic control unit.

[0012] The specific functions of each component using the above technical solution are as follows: (a) Bridge plug setting device Overall function: It completes the anchoring and sealing of the target layer in the casing of a horizontal coal-bearing gas well, realizes the precise positioning of the secondary fracturing section, isolates non-target layers, and allows the hydraulic fracturing energy to be fully applied to the target layer.

[0013] The first cylinder, the second cylinder, and the first annular blocking plate form a sealed first annular cavity, providing installation space and a pressure-bearing cavity for the setting power and actuation components, while also serving as the outer load-bearing body of the device.

[0014] Power unit: It is filled with gunpowder, which is ignited by a ground-based electronic control unit via wires. The combustion produces high-pressure gas, which provides the core power for the bridge plug setting seal.

[0015] Annular power piston and power rod: transmit the high-pressure thrust of the power unit, drive the annular cone to move axially, and realize the axial transmission of force.

[0016] Annular cone: Through the wedge structure of the cone surface and the inner inclined surface of the slip, the axial thrust is converted into the radial expansion force of the slip, so as to open and anchor the slip.

[0017] Kawa: Made of soluble magnesium alloy, it expands radially under the pressure of the cone and embeds itself into the inner wall of the casing, achieving a firm anchoring between the device and the casing. It can be dissolved after fracturing, eliminating the need for drilling.

[0018] Locking pin: Limits and locks the moved annular cone to prevent it from springing back and ensures long-term stability of anchoring and sealing.

[0019] Sealing unit: Composite rubber sleeve structure, the pressure-bearing component is soluble magnesium alloy. After radial expansion under axial thrust, it is pressed and sealed with the inner wall of the sleeve and the outer wall of the second cylinder respectively, realizing the annular isolation of the target layer. It can be dissolved after fracturing.

[0020] Wires: connect the ground control unit and the power unit to enable remote ground control of the sealing action.

[0021] (ii) Fracturing fluid transport compartment (fracturing fluid channel and stroke-type delivery assembly) Overall function: To construct a controllable transport channel for fracturing fluid from the casing to the double-set target section, and to achieve pressurized injection of fracturing fluid in conjunction with a stroke-type piston pressurization device.

[0022] The second cylinder, the third cylinder, and the second annular plug plate form a sealed second annular cavity, providing cavity space for the temporary storage and pressurization of fracturing fluid.

[0023] The first front slide, the front movable valve hole, and the front fixed valve hole constitute the fracturing fluid inlet control valve group. By axially sliding the first front slide, the valve hole is opened and closed, realizing the controllable injection of fracturing fluid from the casing into the second annular cavity.

[0024] The first rear sliding cylinder, the rear movable valve hole, and the rear fixed valve hole constitute the fracturing fluid discharge control valve group. By axially sliding the first rear sliding cylinder, the valve hole is opened and closed, realizing the controllable injection of pressurized fracturing fluid in the second annular cavity into the target layer.

[0025] The front annular piston plate, front axial rod, and front radial rod transmit pressure and displacement. Driven axially by the fracturing fluid pressure in the second annular cavity, they drive the slide cylinder to slide synchronously, thereby realizing the on / off control of the inlet valve group.

[0026] The rear annular piston plate, rear axial rod, and rear radial rod transmit linkage displacement and move axially synchronously with the stroke-type piston pressurization device, driving the slide cylinder to slide synchronously and realize the on / off control of the liquid outlet valve group.

[0027] The first front guide hole and the first rear guide hole provide installation and sliding channels for the radial rod, while ensuring the coaxiality and sliding stability of each component.

[0028] (iii) Stroke-type piston pressurization device (pressure control and booster drive assembly) Overall function: By changing the pump injection pressure, the reciprocating motion of the piston linkage mechanism is controlled to realize the alternating opening and closing of the valve group and the pressurization and amplification of the fracturing fluid, thus completing the stroke-type pressurized injection.

[0029] The partition, fourth cylinder, and fifth cylinder separate the front and rear chambers of the device, providing a fixed mounting base for the front and rear cylinders and ensuring the coaxiality of the front and rear piston mechanisms.

[0030] Front cylinder and front piston: Receive the pumping pressure of fracturing fluid inside the casing, drive the front piston to move axially, and provide initial power for the entire linkage mechanism.

[0031] Rear cylinder and rear piston: They are synchronously linked with the front piston through a linkage rod, and the fracturing fluid pressure is amplified by the area difference to increase the injection pressure of the target section.

[0032] Linkage rod: rigidly connects the front piston and the rear piston, enabling synchronous axial movement of the front and rear pistons and ensuring the coordination of the front and rear valve groups.

[0033] Front and rear springs: provide reset force for the piston mechanism, push the piston to reset when the pumping pressure is unloaded, prepare for the next stroke injection, and realize reciprocating cycle action.

[0034] Second front guide hole, second front slide cylinder, and front drive rod: connect the front piston and the front radial rod, transmit axial displacement, and at the same time ensure the sealing of the front cylinder to prevent fracturing fluid leakage.

[0035] The second rear guide hole, the second rear slide cylinder, and the rear drive rod connect the rear piston and the rear radial rod, transmitting axial displacement while ensuring the sealing of the rear cylinder, and enabling the front and rear valve groups to work synchronously.

[0036] In summary, the overall technical effects of the present invention are as follows: (1) Precise double-setting seal to solve the problem of uncontrolled positioning during fracturing: By combining this device with the end soluble bridge plug, a double-setting sealed cavity is formed, which can accurately lock the target fracturing layer and prevent the fracturing fluid from flowing to non-target layers. It is perfectly adapted to the characteristics of strong heterogeneity and complex geostress in coal-series reservoirs, and solves the core pain point of inaccurate secondary fracturing position in traditional processes.

[0037] (2) Stroke-type booster injection with large displacement, breaking through process limitations: The innovative piston linkage booster structure amplifies the fracturing fluid pressure through piston area difference. Combined with the valve group alternating switching, it realizes uninterrupted stroke-type high-pressure injection, breaking through the displacement limitation of coiled tubing process. It can realize large displacement and high-pressure fracturing, greatly improve the fracture length and fracture support effect, and solve the problems of small displacement, serious filtration loss and limited scale of modification in traditional process.

[0038] (3) Soluble structure design simplifies operation, reduces costs and increases efficiency: The pressure-bearing components of the slips and sealing units are all made of soluble magnesium alloy. They can automatically dissolve under formation conditions 10 hours after fracturing, eliminating the need for drilling and grinding bridge plugs, greatly shortening the construction cycle, reducing operating costs, and avoiding secondary damage to the reservoir caused by drilling and grinding operations.

[0039] (4) Strong adaptability to working conditions and reduced reservoir damage: The use of bare casing injection method eliminates the need for continuous tubing drag operation, avoiding problems such as coal and rock breakage and coal powder blockage caused by temporary plugging and turning, nitrogen foam fracturing, etc. It is suitable for complex working conditions such as broken coal body and deep high ground stress coal seam, greatly improving the adaptability and production increase effect of secondary fracturing.

[0040] (5) Automated cyclic operation improves construction efficiency: The piston mechanism can be reciprocated and injected by pump pressure, eliminating the need for frequent lifting and lowering of the tubing string. After a single stage of fracturing is completed, the operation can be directly switched to the next stage, greatly improving the construction efficiency of multi-stage secondary fracturing. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the pumping position during construction of the present invention in a horizontal coalbed methane well.

[0042] Figure label: Double-set target section-1, first cylinder-2, second cylinder-3, first annular plug-4, first annular cavity-5, power unit-6, annular power piston-7, power rod-8, annular cone-9, slip-on-10, locking pin-11, sealing unit-12, wire-13, third cylinder-14, second annular plug-15, second annular cavity-16, first front slide cylinder-17, first rear slide cylinder-18, front annular piston plate-19, rear annular piston plate-20, front fixed valve hole-21, first front guide hole-22, front movable valve hole-23, rear fixed valve hole-24, first Rear guide hole-25, rear movable valve hole-26, front radial rod-27, front axial rod-28, rear radial rod-29, rear axial rod-30, partition-31, fourth cylinder-32, fifth cylinder-33, front cylinder-34, front piston-35, rear cylinder-36, rear piston-37, linkage rod-38, front spring-39, rear spring-40, second front guide hole-41, second front slide cylinder-42, front drive rod-43, second rear guide hole-44, second rear slide cylinder-45, rear drive rod-46, sleeve-47, pumping soluble bridge plug-48, new bridge plug setting device-49. Detailed Implementation

[0043] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0044] like Figure 1 and Figure 2 As shown, the novel bridge plug setting device for secondary staged fracturing of a coal-bearing gas horizontal well according to the present invention includes a bridge plug setting device, a fracturing fluid transport chamber, and a stroke-type piston pressurizing device. The fracturing fluid transport chamber is located inside the bridge plug setting device, and the stroke-type piston pressurizing device is located inside the fracturing fluid transport chamber. The bridge plug setting device is used to precisely position the double-setting target segment 1 of the secondary fracturing within the casing 47 of the coal-bearing gas horizontal well, so that hydraulic fracturing directly acts on the double-setting target segment 1. The fracturing fluid transport chamber is used to provide a channel for the fracturing fluid to be transported from the casing 47 to the double-setting target segment 1 of the horizontal well in a stroke-type manner. The stroke-type piston pressurizing device is used to control the pressure between the casing 47 of the horizontal well and the double-setting target segment 1 by the pump injection pressure, so as to achieve the effect of pumping fracturing fluid to the double-setting target segment 1 and applying stroke-type pressurization.

[0045] The bridge plug setting device includes a first cylinder 2 with its centerline arranged along the front-to-back direction. A second cylinder 3 is coaxially arranged inside the first cylinder 2. Both the front and rear ends of the first cylinder 2 and the second cylinder 3 are provided with first annular blocking plates 4. A sealed first annular cavity 5 is formed between the inner circle of the first cylinder 2 and the outer circle of the second cylinder 3. Within the first annular cavity 5, from front to back, are arranged a power unit 6, an annular power piston 7, a power rod 8, an annular cone 9, a slip 10, a locking pin 11, and a sealing unit 12. The power unit 6 is filled with gunpowder. The rear conical surface of the annular cone 9 is adapted to the inner inclined surface of the slip 10. The pressure-bearing components in the slip 10 and the sealing unit 12 are made of soluble magnesium alloy, which can dissolve 10 hours after fracturing. A wire 13 is connected to the front of the power unit 6 for connection to a ground-based electrical control unit.

[0046] The fracturing fluid transport chamber includes a third cylinder 14 coaxially arranged inside a second cylinder 3. Both the second cylinder 3 and the third cylinder 14 have second annular blocking plates 15 at their front and rear ends. A sealed second annular cavity 16 is formed between the inner circle of the second cylinder 3 and the outer circle of the third cylinder 14. A first front sliding cylinder 17 and a first rear sliding cylinder 18 are slidably connected to the outer circle of the third cylinder 14. A front annular piston plate 19 located in front of the first front sliding cylinder 17 is slidably sealed on the front side of the second annular cavity 16. A rear annular piston plate 20 located behind the first rear sliding cylinder 18 is slidably sealed on the rear side of the second annular cavity 16. At least two front fixed valve holes 21 are arranged in a circumferential array on the front side of the first front sliding cylinder 17 covering surface on the cylinder wall of the third cylinder 14. At least two first front guide holes 22 are arranged in a circumferential array on the rear side of the first front sliding cylinder 17 covering surface on the cylinder wall of the third cylinder 14. A front movable valve hole 23 corresponding to the front fixed valve hole 21 is opened on the front side of the first front sliding cylinder 17. The third cylinder 14 has at least two rear fixed valve holes 24 arranged in a circumferential array on the rear side of the first rear sliding cylinder 18 covering surface. The third cylinder 14 has at least two first rear guide holes 25 arranged in a circumferential array on the front side of the first rear sliding cylinder 18 covering surface. The first rear sliding cylinder 18 has a rear movable valve hole 26 that corresponds one-to-one with the rear fixed valve holes 24 on the front side. A front radial rod 27 is provided inside the first front guide hole 22, which is radially arranged along the third cylinder 14. The front radial rod 27 is fixedly connected to the first front slide cylinder 17. The outer end of the front radial rod 27 passes through the first front slide cylinder 17 and is connected to the rear side of the front annular piston plate 19 through the front axial rod 28. A rear radial rod 29 is provided inside the first rear guide hole 25, which is radially arranged along the third cylinder 14. The rear radial rod 29 is fixedly connected to the first rear slide cylinder 18. The outer end of the rear radial rod 29 passes through the first rear slide cylinder 18 and is connected to the front side of the rear annular piston plate 20 through the rear axial rod 30. The inner ends of the front radial rod 27 and the rear radial rod 29 are both connected to the stroke-type piston pressurization device.

[0047] The stroke-type piston pressurizing device includes a partition 31 fixedly disposed in the middle of the third cylinder 14, a fourth cylinder 32 coaxially disposed in the front half of the third cylinder 14 fixedly disposed on the front side of the partition 31, and a fifth cylinder 33 coaxially disposed in the rear half of the third cylinder 14 fixedly disposed on the rear side of the partition 31. The fourth cylinder 32 has a front cylinder 34 coaxially arranged in the inner circle. The rear end of the front cylinder 34 is fixedly connected to the front side of the partition 31. The front piston 35 is slidably arranged inside the front cylinder 34. The fifth cylinder 33 has a rear cylinder 36 coaxially arranged in the inner circle. The front end of the rear cylinder 36 is fixedly connected to the rear side of the partition 31. The rear piston 37 is slidably arranged inside the rear cylinder 36. The front piston 35 and the rear piston 37 are connected by a linkage rod 38 that passes through the partition 31. A front spring 39 is sleeved on the linkage rod 38 between the rear side of the front piston 35 and the front side of the partition 31, and a rear spring 40 is sleeved on the linkage rod 38 between the front side of the rear piston 37 and the rear side of the partition 31. The fourth cylinder 32 and the front cylinder 34 are provided with second front guide holes 41 that correspond one-to-one with the first front guide hole 22. The outer circle of the fourth cylinder 32 is provided with a sealing second front slide cylinder 42 that covers the second front guide hole 41. The front radial rod 27 is fixedly connected to the second front slide cylinder 42 and passes through the second front guide hole 41. The rear side of the front piston 35 is connected to the inner end of the front radial rod 27 through the front drive rod 43. The fifth cylinder 33 and the rear cylinder 36 are provided with second rear guide holes 44 that correspond one-to-one with the first rear guide hole 25. The outer circle of the fifth cylinder 33 is provided with a second rear slide cylinder 45 that covers and seals the second rear guide hole 44. The rear radial rod 29 is fixedly connected to the second rear slide cylinder 45 and passes through the second rear guide hole 44. The front side of the rear piston 37 is connected to the inner end of the rear radial rod 29 through the rear drive rod 46.

[0048] The annular surface area of ​​the front annular piston plate 19 is larger than the circular surface area of ​​the front piston 35, and the circular surface area of ​​the front piston 35 is larger than the circular surface area of ​​the rear piston 37.

[0049] The technical solution of this invention was piloted in the Shizhuang South Block and achieved good results. The specific implementation method is briefly described below using the SZNL-01 well in the Shizhuang South Block as an example. This well has a depth of 1862m, a wellhead elevation of 222m, a vertical depth of 839m, and a horizontal section length of 801m. The initial hydraulic fracturing of the horizontal section is divided into ten stages, with the first stage being the end (rear end). Each stage has 2-4 perforations, and the number of perforations is the same across all stages. Based on the gas production of each stage of the horizontal well, secondary fracturing is performed on one or several stages with lower gas production, in a sequence from back to front. The specific implementation process of the secondary fracturing is as follows: S1. Pumping the soluble bridge plug 48 to the end of the horizontal section for setting: If the gas production in the second stage is small, connect the soluble bridge plug 48 to the setting tool on a cable and push it to 10m after the end of the second stage of fracturing in the horizontal well section by pumping. A command is issued from the surface, the propellant inside the setting tool is ignited, generating high-pressure gas that pushes the piston, causing the slips 10 of the soluble bridge plug 48 to open radially and bite into the casing 47 wall. Then, the setting tool is disengaged from the soluble bridge plug 48 and retracted. A temporary plugging ball is then dropped into the coalbed methane well, causing it to fall onto the ball seat of the soluble bridge plug 48, thus achieving end-stage setting.

[0050] S2. Pumping and setting the novel bridge plug setting device 49 of the present invention into the horizontal well section: Connect the novel bridge plug setting device 49 to the cable, and push the novel bridge plug setting device 49 to 10m before the front end of the second stage of fracturing in the horizontal well section by pumping; the ground issues a command. The ground control center ignites the gunpowder in the power unit 6 via wire 13. The combustion of the gunpowder generates a large amount of high-pressure gas, which pushes the annular power piston 7 and the power rod 8 to push the annular cone 9. The annular cone 9, like a wedge, squeezes into the inner inclined surface of the slip 10, forcing the slip 10 to expand radially and embed into the inner wall of the sleeve 47 until the annular cone 9 moves backward to the rear side of the locking pin 11 and is locked by the locking pin 11, so that the entire new bridge plug setting device 49 and the sleeve 47 form a firm anchor. At the same time, the thrust of the annular cone 9 strongly compresses the sealing unit 12, which is usually a composite rubber sleeve, causing the sealing unit 12 to expand radially. The outer circle of the sealing unit 12 presses against the inner circle of the sleeve 47 to seal, and the inner circle of the sealing unit 12 presses against the outer circle of the second cylinder 3 to seal, thus completing the setting. The pressure-bearing components in the slip 10 and sealing unit 12 are made of soluble magnesium alloy. Under the conditions of coal seam wellbore temperature and fracturing fluid, they can be completely dissolved 10 hours after fracturing is completed. After dissolution, the used new bridge plug setting device 49 can be pushed to the end of the horizontal well section through well cleaning.

[0051] S3. Secondary fracturing is performed on the double-setting target section 1 (second section) between the soluble bridge plug 48 and the new bridge plug setting device 49: Fracturing fluid is pumped into the casing 47 at the wellhead. As the pressure inside the casing 47 gradually increases with the injection of fracturing fluid, the front piston 35 slides backward in the front cylinder 34, the front spring 39 is compressed, and the front piston 35 drives the rear piston 37 to slide backward in the rear cylinder 36 via the linkage rod 38. The front piston 35 drives the front radial rod 27 to move backward via the front drive rod 43. The front radial rod 27 drives the second front slide cylinder 42, the first front slide cylinder 17, the front axial rod 28, and the front annular piston plate 19 to move backward in the second annular cavity 16. At this time, the rear piston 37 drives the rear radial rod 29 to move backward via the rear drive rod 46. The rear radial rod 29 drives the second rear slide cylinder 45, the first rear slide cylinder 18, the rear axial rod 30, and the rear annular piston plate 20 to move backward within the second annular cavity 16 until the front movable valve hole 23 on the first front slide cylinder 17 moves backward to correspond with the front fixed valve hole 21 on the wall of the third cylinder 14. At this time, the fracturing fluid enters the second annular cavity 16 through the front fixed valve hole 21 and the front movable valve hole 23. Since the annular surface area of ​​the front annular piston plate 19 is larger than the circular surface area of ​​the front piston 35, the pressure of the fracturing fluid on the rear side of the front annular piston plate 19 within the second annular cavity 16 is greater than the pressure of the fracturing fluid on the front movable valve hole 20. The pressure on the front side of the plug 35 causes the front annular piston plate 19 to move forward, which in turn drives the front radial rod 27 via the front axial rod 28, and then drives the front drive rod 43, the front piston 35, the second front slide cylinder 42, and the first front slide cylinder 17 to move forward. The front movable valve hole 23 on the first front slide cylinder 17 is misaligned with the front fixed valve hole 21 on the wall of the third cylinder 14, and the fracturing fluid no longer enters the second annular cavity 16. At the same time, the linkage rod 38 drives the rear annular piston plate 20 to move forward, which in turn drives the rear radial rod 29 via the rear axial rod 30, and then drives the rear drive rod 46, the rear piston 37, the second rear slide cylinder 45, and the first rear slide cylinder 18 to move forward. The rear movable valve hole 23 on the first rear slide cylinder 18 is misaligned with the front fixed valve hole 21 on the wall of the third cylinder 14, and the fracturing fluid no longer enters the second annular cavity 16. The movable valve hole 26 is connected to the rear fixed valve hole 24 on the wall of the third cylinder 14. The fracturing fluid in the second annular cavity 16 is injected into the double-setting target section 1 between the soluble bridge plug 48 and the new bridge plug setting device 49 through the rear movable valve hole 26 and the rear fixed valve hole 24, completing the first "stroke-type" fracturing fluid injection work and performing secondary fracturing on the coal seam of the double-setting target section 1. Since the circular area of ​​the front piston 35 is much larger than the circular area of ​​the rear piston 37, for example, the circular area of ​​the front piston 35 is twice the circular area of ​​the rear piston 37, the pressure of the fracturing fluid injected into the double-setting target section 1 can be twice the fracturing fluid pressure in the casing 47.After the front spring 39, rear spring 40, front piston 35, and rear piston 37 have reset, the pressure of the fracturing fluid in the second annular cavity 16 is completely released. The fracturing fluid is continuously injected through the wellhead casing 47. The fracturing fluid in the casing 47 drives the front piston 35 to move backward again, and the front movable valve hole 23 and the front fixed valve hole 21 are connected. The fracturing fluid enters the second annular cavity 16. The front annular piston plate 19 then moves forward, and the front movable valve hole 23 and the front fixed valve hole 21 are misaligned. The rear movable valve hole 26 and the rear fixed valve hole 24 are connected. The fracturing fluid with higher pressure in the second annular cavity 16 is injected into the target layer, completing the second "stroke-type" fracturing fluid injection. In this way, fracturing fluid is continuously pumped into the target layer in a "stroke-type" manner to achieve secondary fracturing of the coal seam in the target layer. During the secondary fracturing process, the mechanical strength of the soluble bridge plug 48 and the new bridge plug setting device 49 is sufficient to withstand extremely high fracturing pressure. S4. After the secondary fracturing operation of the target layer is completed, the well is shut in and the slips 10 and sealing unit 12 of the soluble bridge plug 48 and the new bridge plug setting device 49 are dissolved. The fracturing fluid and formation water in the wellbore come into full contact with the bridge plug. Under the combined action of formation temperature and environment, the slips 10 and sealing unit 12 begin to undergo electrochemical corrosion reaction, causing the soluble bridge plug 48 and the new bridge plug setting device 49 to dissolve and shrink in diameter, and no longer anchor the casing 47. S5. Repeat steps S1-S4 to perform secondary fracturing on other sections with low gas production: S6. Well Circulation and Drainage: After all the soluble bridge plugs 48 and the new bridge plug setting device 49 have dissolved, the well circulation tool is used to push the soluble bridge plugs 48 and the new bridge plug setting device 49 backward to the end of the coalbed methane horizontal well, and the coalbed methane well re-enters the drainage stage.

[0052] The field implementation results show that, using the construction method of this invention, the daily gas production of the well after secondary fracturing increased by 3.2 times compared with that before the modification, the reservoir modification effect was significant, the construction cycle was shortened by 45% compared with the traditional coiled tubing fracturing, the operating cost was reduced by 38%, and there were no problems such as coal dust blockage or secondary damage to the reservoir, achieving excellent production increase and economic benefits.

[0053] The above embodiments illustrate the basic principles and features of the present invention, but are merely preferred embodiments and are not limited to these embodiments. Those skilled in the art, inspired by this patent, can make many modifications and improvements without departing from the spirit and scope of the claims, all of which fall within the scope of protection of the present invention. Therefore, the scope of this patent and its protection should be determined by the appended claims.

Claims

1. A novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells, characterized in that: It includes a bridge plug setting device, a fracturing fluid transport chamber, and a stroke-type piston pressurization device. The fracturing fluid transport chamber is located inside the bridge plug setting device, and the stroke-type piston pressurization device is located inside the fracturing fluid transport chamber. The bridge plug setting device is used to accurately position the double-setting target section for secondary fracturing in the casing of a coal-bearing gas horizontal well, so that hydraulic fracturing can directly act on the double-setting target section. The fracturing fluid transport chamber is used to provide a channel for fracturing fluid to be transported from the casing in a stroke manner to the target section of the horizontal well with dual setting; The stroke-type piston pressurization device is used to control the pressure between the horizontal well casing and the double-set target section by pumping pressure, so as to achieve the effect of pumping fracturing fluid into the double-set target section and stroke-type pressurization.

2. The novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells according to claim 1, characterized in that: The bridge plug setting device includes a first cylinder with its centerline arranged along the front-to-back direction, and a second cylinder coaxially arranged inside the first cylinder. Both the front and rear ends of the first and second cylinders are provided with first annular blocking plates. A sealed first annular cavity is formed between the inner circle of the first cylinder and the outer circle of the second cylinder. The middle part of the first annular cavity is provided with a power unit, an annular power piston, a power rod, an annular cone, a slip, a locking pin, and a sealing unit in sequence from front to back. The power unit is filled with gunpowder, and the rear conical surface of the annular cone is adapted to the inner inclined surface of the slip. The pressure-bearing components in the slip and the sealing unit are made of soluble magnesium alloy, which can be dissolved 10 hours after the fracturing is completed.

3. The novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells according to claim 2, characterized in that: The fracturing fluid transport chamber includes a third cylinder coaxially arranged inside a second cylinder. The front and rear ends of both the second and third cylinders are provided with second annular blocking plates. A sealed second annular cavity is formed between the inner circle of the second cylinder and the outer circle of the third cylinder. A first front slide cylinder and a first rear slide cylinder are slidably connected to the outer circle of the third cylinder. A front annular piston plate located in front of the first front slide cylinder is slidably sealed on the front side of the second annular cavity. A rear annular piston plate located behind the first rear slide cylinder is slidably sealed on the rear side of the second annular cavity. At least two front fixed valve holes are arranged in a circular array on the front side of the first front slide cylinder covering surface on the cylinder wall of the third cylinder. At least two first front guide holes are arranged in a circular array on the rear side of the first front slide cylinder covering surface on the cylinder wall of the third cylinder. A front movable valve hole corresponding to the front fixed valve hole is opened on the front side of the first front slide cylinder. The third cylinder has at least two rear fixed valve holes arranged in a circumferential array on the rear side of the first rear sliding cylinder covering surface, and at least two first rear guide holes arranged in a circumferential array on the front side of the first rear sliding cylinder covering surface. The first rear sliding cylinder has a rear movable valve hole that corresponds one-to-one with the rear fixed valve holes on the front side. A front radial rod is provided inside the first front guide hole, which is arranged radially along the third cylinder. The front radial rod is fixedly connected to the first front slide cylinder. The outer end of the front radial rod passes through the first front slide cylinder and is connected to the rear side of the front annular piston plate through the front axial rod. A rear radial rod is provided inside the first rear guide hole, which is arranged radially along the third cylinder. The rear radial rod is fixedly connected to the first rear slide cylinder. The outer end of the rear radial rod passes through the first rear slide cylinder and is connected to the front side of the rear annular piston plate through the rear axial rod. The inner ends of both the front and rear radial rods are connected to the stroke-type piston pressurization device.

4. The novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells according to claim 3, characterized in that: The stroke-type piston pressurizing device includes a partition plate fixedly disposed in the middle of the third cylinder, a fourth cylinder coaxially disposed in the front half of the third cylinder fixedly disposed on the front side of the partition plate, and a fifth cylinder coaxially disposed in the rear half of the third cylinder fixedly disposed on the rear side of the partition plate. The fourth cylinder has a front cylinder arranged coaxially on its inner circle. The rear end of the front cylinder is fixedly connected to the front side of the partition plate. The front piston is slidably arranged inside the front cylinder. The fifth cylinder has a rear cylinder arranged coaxially on its inner circle. The front end of the rear cylinder is fixedly connected to the rear side of the partition plate. The rear piston is slidably arranged inside the rear cylinder. The front piston and the rear piston are connected by a linkage rod that passes through the partition. A front spring is sleeved on the linkage rod between the rear side of the front piston and the front side of the partition, and a rear spring is sleeved on the linkage rod between the front side of the rear piston and the rear side of the partition. The fourth cylinder and the front cylinder are provided with second front guide holes that correspond one-to-one with the first front guide holes. The outer circle of the fourth cylinder is provided with a sealing second front slide cylinder that covers the second front guide holes. The front radial rod is fixedly connected to the second front slide cylinder and passes through the second front guide hole. The rear side of the front piston is connected to the inner end of the front radial rod through the front drive rod. The fifth cylinder and the rear cylinder are provided with second rear guide holes that correspond one-to-one with the first rear guide holes. The outer circle of the fifth cylinder is provided with a second rear slide cylinder that covers and seals the second rear guide holes. The rear radial rod is fixedly connected to the second rear slide cylinder and passes through the second rear guide hole. The front side of the rear piston is connected to the inner end of the rear radial rod through a rear drive rod.

5. The novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells according to claim 4, characterized in that: The annular surface area of ​​the front piston plate is larger than the circular surface area of ​​the front piston, and the circular surface area of ​​the front piston is larger than the circular surface area of ​​the rear piston.

6. The novel bridge plug setting device for secondary staged fracturing of coal-bearing gas horizontal wells according to claim 5, characterized in that: The front of the power unit is connected to a wire that connects to the ground control unit.

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