Integrated branch pipe telescopic downhole slitting device and method

Abstract

The application belongs to the technical field of coal mine and oil and gas field slotted device, and relates to an integrated branch pipe telescopic underground slotted device and method, which comprises a high-pass overflow valve, a valve bypass main flow channel, a low-pass check valve, a low-pressure fluid cavity and a telescopic branch pipe jetting system and the like; the high-pass overflow valve is arranged at the rear end of the shell inlet, fracturing fluid flow channels are arranged on the two sides of the high-pass overflow valve, the rear part of the fracturing fluid flow channels is sequentially communicated with a rubber cylinder and a fracturing fluid outlet, the valve bypass main flow channel arranged outside the high-pass overflow valve is respectively communicated with the inlet and the low-pressure fluid cavity at the front and rear ends, the low-pressure fluid cavity, the low-pass check valve and a drill bit are sequentially communicated, and the perforating flow channels distributed outside the low-pass check valve are respectively communicated with the low-pressure fluid cavity and the telescopic branch pipe jetting system at the front and rear ends; the device drives the telescopic branch pipe and the multi-stage pulse conical nozzle through the jet pressure difference, improves the depth, width and efficiency of the water jet slotted, realizes deeper and wider hydraulic slotted under the medium and low pressure water jet, and has low cost and remarkable effect.

Description

Technical fields:

[0001] This invention belongs to the technical field of hydraulic fracturing equipment in coal mines and oil and gas fields. It relates to a downhole tool and method for radial jet fracturing and permeation enhancement using a push-out branch pipe, and particularly to an integrated branch pipe telescopic downhole fracturing device and method, which can improve hydraulic fracturing capability and fracturing, permeation enhancement and permeability enhancement effects under medium and low pressure. Background technology:

[0002] High-pressure water jet radial slotting is a technique that assists in fracturing, permeability enhancement, and permeability improvement by increasing the flow channels in coal seams and oil and gas reservoirs. The flow capacity of the slot is positively correlated with the width and depth of the slot. Currently, hydraulic slotting is divided into medium-low pressure slotting and high-pressure slotting. Medium-low pressure (0.5-70MPa) water jet slotting has low efficiency, shallow slot depth, and poor flow capacity. Due to the contradiction between high pressure and high flow rate under limited pump power, high-pressure (70-140MPa) water jetting, although efficient, has a small slot width. In addition, the effective slot depth of high-pressure water jetting is positively correlated with the nozzle diameter, and the effective spray distance when the ambient medium is air is more than 400 times that of water. Taking a 100MPa high-pressure water jet with a nozzle diameter of 1mm as an example, if the water in the slot can be discharged in time, the slot depth can reach 1 to 2 meters; if water remains in the slot, the slot depth drops to less than 0.1 meters.

[0003] Among existing patent technologies, Chinese Patent Publication No. CN201915932U discloses a downhole hydraulic fracturing tool. This tool includes a mover, a resetter, and a nozzle. A hydraulic drive device moves the mover downwards, causing the nozzle to move downwards as well. At a designated depth, the nozzle uses high-pressure hydraulic pressure to perforate and fracture the coal seam, creating numerous artificial fractures within the original coal seam. This forms channels for coalbed methane outflow, increasing the permeability of the coal seam. Consequently, during gas extraction in the well, a large pressure drop occurs around the wellbore, increasing the surface area for gas desorption and ensuring rapid and relatively sustained release of coalbed methane. The tool uses a reset spring to reset the mover. Chinese Patent Publication No. CN105909228B discloses a pulsed high-pressure hydraulic fracturing device and method, relating to the field of coal mine gas extraction. The device includes a central control console, a water delivery unit, a hydraulic fracturing and cutting system, and a pulsed hydraulic pressure generation system. The pulsed hydraulic pressure generation system includes a high-pressure water subsystem and a pulsed high-pressure water frequency generation subsystem. The inlet of the high-pressure water subsystem and the water delivery unit are connected through a water injection pipe, and the outlet of the water delivery unit is connected to the hydraulic fracturing and cutting system. The pulsed high-pressure water frequency generation subsystem includes a motor and a ball valve. The ball valve is installed on the water injection pipe, and the motor is connected to the ball valve. The central control console is connected to both the high-pressure water subsystem and the motor.

[0004] In practical engineering applications, timely water drainage from the kerf is difficult to control technologically, and the depth of the kerf using high-pressure water jets is not ideal, limiting the permeability and infiltration enhancement effects after kerfing. To solve this problem, ultra-high-pressure water jets with even higher pressure can be used to increase the effective kerf distance, but this brings high costs and high risks, especially in densely populated and confined spaces like coal mines, where the safety issues of ultra-high-pressure water jets are particularly prominent. Summary of the Invention:

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as low efficiency and shallow cutting depth in low-pressure water jet cutting in existing downhole hydraulic fracturing equipment, as well as the unsatisfactory cutting depth and limited permeability and infiltration enhancement effects of high-pressure water jet cutting. By using extendable symmetrical branch pipes to increase the width and depth of low- and medium-pressure water jet cutting, and overcoming the dependence of water jet cutting on high pressure, an integrated push-out downhole fracturing device and method are designed to enhance the cutting and fracturing effects under low- and medium-pressure water jet conditions, thereby improving the permeability and infiltration enhancement effects.

[0006] To achieve the above objectives, this invention relates to an integrated branch-pipe telescopic downhole fracturing device. Its main structure includes an inlet, a high-flow overflow valve, a valve-side main channel, a rubber sleeve inlet, a rubber sleeve, a fracturing fluid outlet, a low-flow check valve, a perforation channel, a shell, a drill bit, a low-pressure fluid chamber, and a telescopic branch-pipe injection system. The tubular shell has an inlet at its front end and a high-flow overflow valve at its rear end. Fracturing fluid channels are located on both sides of the high-flow overflow valve. The middle and rear portions of the fracturing fluid channels communicate with the rubber sleeve inlet. The rubber sleeve is embedded in the outer side of the shell. The rear end of the fracturing fluid channels communicates with the fracturing fluid outlet. When the pressure difference between the front and rear ends of the high-flow overflow valve reaches 40 MPa, the high-flow overflow valve opens, and the fracturing fluid channels transmit fluid to the rubber sleeve and the fracturing fluid outlet. The rubber sleeve expands when the high-flow overflow valve opens, forming a seal between the device and the wellbore drilled by the drill bit, preventing fracturing fluid from flowing out of the wellbore. Four valve-side valves are arranged in a circular array on the outer side of the high-flow overflow valve. The main flow channel is connected to the inlet at its front end and to the low-pressure fluid chamber with a screw-like structure at its rear end. When the high-flow relief valve is closed, the main flow channel can transfer fluid to the low-pressure fluid chamber downstream of the device. The rear end of the low-pressure fluid chamber is connected to the input end of the low-flow check valve. The output end of the low-flow check valve is connected to the drill bit at the rear end of the housing. When the pressure difference between the front and rear ends of the low-flow check valve is below 5 MPa, the low-flow check valve opens, and fluid is supplied to the drill bit via the low-flow check valve to provide the necessary fluid for drilling. The drill bit drills and forms a wellbore deep into the coal or oil seam when the low-flow check valve is open. Four perforation channels are arranged in a circular array on the outer side of the low-flow check valve. The front end of each perforation channel is connected to the rear end of the low-pressure fluid chamber, and the rear end is connected to the telescopic branch pipe injection system. When the low-flow check valve is closed, the perforation channels can transfer fluid to the telescopic branch pipe injection system. The telescopic branch pipe injection system is equipped with a telescopic branch pipe.

[0007] The high-flow overflow valve of this invention comprises a valve inlet, a permanent magnet, a valve body, a fracturing fluid flow channel, a front valve return spring, a low-pressure flow channel, and a front valve chamber. The front valve chamber consists of a frustum-shaped front inlet cavity, a cylindrical front valve seat cavity in the middle, a cylindrical front limiting cavity in the middle and rear, and a cylindrical front valve stem cavity in the rear. The diameter of the front inlet cavity is smaller than the diameter of the front valve seat cavity, the diameter of the front valve seat cavity is larger than the diameter of the front limiting cavity, and the diameter of the front limiting cavity is larger than the diameter of the front valve stem cavity. The front end is connected to the valve inlet, and the front end of the valve inlet is connected to the middle of the inlet pipe; the valve body is installed in the front valve cavity, which is composed of a front valve core, a middle front valve seat, and a rear front valve stem. The front valve core can be plugged into the front inlet cavity and the valve inlet to seal the valve inlet; the rear of the front valve core is connected to the front valve seat, which is confined in the front valve seat cavity. Magnetic grooves are symmetrically arranged on the upper and lower parts of the front valve seat, and permanent magnets are symmetrically installed on the upper and lower parts of the front valve seat cavity. The permanent magnets and magnetic grooves match to achieve the desired effect. The valve features a slotted connection. The magnetic force of the permanent magnet allows the valve body to open when the pressure at the valve inlet reaches 40MPa. The valve body moves backward, separating the permanent magnet from the magnetic slot. The rear of the front valve seat connects to the front valve stem, which is fitted with a front valve return spring. The front valve return spring is confined within the front limit chamber, while the rear end of the front valve stem is confined within the front valve stem chamber. The maximum displacement force of the front valve return spring is less than 1 / 200th of the maximum attraction force of the permanent magnet. The front valve return spring allows the valve body to open at high-flow relief valve... When the pressure difference between the front and rear ends is 0.2MPa, the valve returns to its original position and closes. Low-pressure flow channels are provided on both sides of the rear end of the front valve stem cavity. The low-pressure flow channels are connected to the low-pressure fluid outside the device, so as to keep the valve body in the open state when the pressure difference between the front and rear ends of the high-pass relief valve is above 0.2MPa. Fracturing fluid flow channels are symmetrically arranged on the upper and lower sides of the front valve seat cavity. The low-pressure flow channels are set in the gap between the upper and lower sets of main flow channels beside the valve, and the fracturing fluid flow channels are set in the gap between the left and right sets of main flow channels beside the valve.

[0008] The low-flow check valve of this invention comprises a rear valve inlet, a rear valve body, a rear valve return spring, and a drill bit water channel. A rear valve stem cavity is centrally located at the front of the low-flow check valve. Four rear valve inlets are arranged in a circular array around the outer side of the rear valve stem cavity. The input ends of the rear valve inlets are connected to the rear end of the low-pressure fluid cavity. A funnel-shaped rear valve cavity is located at the rear of the low-flow check valve. The output end of the rear valve inlet is connected to the front end of the rear valve cavity. The rear valve cavity is integrally formed by a frustum-shaped rear valve cap cavity at the front and a cylindrical rear valve limiting cavity at the rear. A rear valve body is provided within the low-flow check valve. The rear valve body is integrally formed by a columnar rear valve stem at the front and a frustum-shaped rear valve cap at the rear. The rear valve stem is slotted into and limited within the rear valve stem cavity. The rear valve cap is limited within the rear valve cap cavity. The rear end of the rear valve cap is connected to the front end of the rear valve return spring. The rear valve return spring limits… The valve is installed in the rear valve limiting chamber, the rear end of which is connected to the front end of the drill bit water channel. The rear end of the drill bit water channel is connected to the front end of the fluid injection pipe in the drill bit. The fluid injection pipe is divided into two or more fluid injection branches. The preload of the rear valve return spring is equivalent to the force borne by the rear valve body when there is a 5MPa pressure difference between the front and rear ends of the low-pass check valve, so that the rear valve body can open under a low pressure of 5MPa. When the pressure difference between the front and rear ends of the low-pass check valve is below 5MPa, the rear valve body opens, and the fluid enters the drill bit water channel through the rear valve inlet and the rear valve chamber in sequence. The drill bit water channel provides the fluid required for drilling to the drill bit. When the pressure difference between the front and rear ends of the low-pass check valve is above 5MPa, the rear valve body moves backward under the action of fluid pressure, the rear valve return spring is compressed, and the rear valve body blocks the rear valve limiting chamber at the rear of the rear valve chamber, and the low-pass check valve closes.

[0009] The telescopic branch pipe injection system of this invention consists of two centrally symmetrical branches. Each branch includes a limiting ring, a piston ring, a branch pipe, a return spring, a steering rail, a jet nozzle, and a telescopic cavity in the drill bit water channel. The two branches are symmetrically arranged on both sides of the drill bit water channel. The front end of the telescopic cavity is connected to the rear end of the perforation channel. A ring-shaped limiting ring is provided at the front of the telescopic cavity, and a ring-shaped piston ring is installed at the rear of the limiting ring. The limiting ring is used to limit the piston ring, which can move within the telescopic cavity. The rear end of the piston ring is connected to the front end of the branch pipe, which is 2m-4m long and has an outer diameter of 4mm-8mm. The branch pipe is composed of a 1 mm elastic steel pipe. A return spring is sleeved on the outside of the branch pipe. The return spring is limited in the rear half of the telescopic cavity. The preload of the return spring can withstand the extension thrust of the branch pipe when there is a pressure difference of 20 MPa inside and outside the jet nozzle. When the branch pipe retracts, the return spring provides the return spring force for the branch pipe. The rear end of the telescopic cavity is connected to the front end of the steering track. The steering track is arc-shaped and can turn the branch pipe 90 degrees to extend radially from the telescopic cavity. The jet nozzle is installed at the rear end of the branch pipe. When the pressure difference between the front end of the piston ring and the outside of the jet nozzle reaches more than 20 MPa, the fluid can push the piston ring to provide the extension thrust for the branch pipe.

[0010] The jet nozzle of this invention consists of an angular nozzle, a secondary oscillating chamber, and a primary oscillating chamber. The primary oscillating chamber is a funnel-shaped cavity. The front circular tube of the primary oscillating chamber is connected to the output end of the branch pipe. The funnel-shaped output end of the primary oscillating chamber is connected to the front circular tube of the funnel-shaped secondary oscillating chamber. The funnel-shaped output end of the secondary oscillating chamber is connected to the front end of the trumpet-shaped angular nozzle. The primary oscillating chamber can generate a strengthened pulsed cavitation cone jet to efficiently break rocks, thereby forming a slit larger than the outer diameter of the branch pipe.

[0011] The integrated branch pipe telescopic downhole slotting device of the present invention realizes radial water jet slotting and fracturing of telescopic branch pipes, including: low-pressure drilling, medium-low pressure slotting, medium-pressure permeability enhancement, and device recovery; the specific steps are as follows:

[0012] (1) Low-pressure drilling: The integrated branch pipe telescopic downhole slotting device is connected to the surface booster pump through the drill pipe. The fluid pressure at the pump inlet is controlled to be below 5MPa. The high-pass overflow valve is closed. The main channel beside the valve transmits the fluid to the low-pressure fluid chamber downstream of the device. At this time, the pressure difference between the front and rear ends of the low-pass check valve is less than 5MPa and it remains open. The fluid in the low-pressure fluid chamber enters the drill bit water channel through the rear valve inlet and the rear valve chamber in sequence. The drill bit water channel provides the fluid required for drilling to the drill bit. The drill pipe drives the tool and the drill bit to rotate and advance, drilling a wellbore of tens of meters in the coal seam.

[0013] (2) Medium and low pressure slotting: Increase the fluid pressure at the pump inlet to 20MPa, close the high-pass overflow valve, and transfer the fluid to the low-pressure fluid chamber downstream of the device through the main flow channel beside the valve. At this time, the pressure difference between the front and rear ends of the low-pass check valve is greater than 5MPa and it is closed. The fluid in the low-pressure fluid chamber is transferred to the telescopic branch pipe jet system through the perforation channel. The fluid mainly flows out to the outside of the device through the branch pipe. The control device and drill bit rotate in place. The pressure difference between the front pressure of the piston ring and the pressure outside the jet nozzle can provide the extension thrust of the branch pipe. Slowly and gradually increase the fluid pressure at the inlet to 35MPa, so that the branch pipe and nozzle slowly extend while rotating the slotting. The jet nozzle strengthens the fluid into a pulse cavitation cone jet for efficient rock breaking and slotting. Then, reduce the fluid pressure at the inlet to 15MPa, so that the branch pipe and nozzle return to their original positions under the spring force of the return spring. The control device and drill bit retreat 0.5m-2m, and repeat the above slotting process to perform jet rotation slotting.

[0014] (3) Medium-pressure permeation enhancement: After the wellbore is filled with the predetermined slots by the jet, the fluid pressure at the inlet is increased to 45MPa. At this time, the high-pass overflow valve is opened, and the fluid enters the front valve seat cavity from the valve inlet. The fluid in the front valve seat cavity enters the fracturing fluid channel. The fluid enters the rubber sleeve from the fracturing fluid channel through the rubber sleeve inlet. The rubber sleeve expands and seals the annular space gap between the device and the wellbore. Then the fluid flows out through the fracturing fluid outlet to perform fracturing and permeation enhancement operations on the slots. At the same time, since the flow rate of the fracturing fluid outlet is more than 10 times that of the nozzle, and the annular pressure gradually increases, the pressure difference between the front pressure of the piston ring and the pressure outside the jet nozzle will be less than 20MPa. The branch pipe and the nozzle remain in a contracted state under the elastic force of the return spring.

[0015] (4) Equipment recovery: After the fracturing and permeation enhancement operations are completed, the pump is stopped and the pressure is released. After the rubber sleeve shrinks back to its original position, the drill rod and equipment are recovered.

[0016] Compared with existing technologies, the integrated branch pipe telescopic downhole slotting device and method designed in this invention has a reasonable main structure, forming an integrated tool and method for wellbore drilling, jet slotting, and fracturing and permeation enhancement, reducing construction complexity and improving construction efficiency. It proposes to improve the depth, width and efficiency of water jet slotting by using a telescopic branch pipe driven by jet pressure difference and a multi-stage pulse conical nozzle, thereby realizing deeper and wider hydraulic slotting under medium and low pressure water jetting, overcoming the current problems of low hydraulic slotting depth and width as well as the high cost and high risk under high pressure jet slotting. Attached image description:

[0017] Figure 1 This is a schematic diagram of the structural principle of the vertical section of the integrated branch pipe telescopic downhole slotting device involved in this invention.

[0018] Figure 2 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along the CC section.

[0019] Figure 3 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along point AA.

[0020] Figure 4 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along DD.

[0021] Figure 5 This is a schematic diagram of the structural principle of the high-pass overflow valve with a vertical cross-section, as per the present invention.

[0022] Figure 6 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along point BB.

[0023] Figure 7 This is a schematic diagram of the structural principle of the low-pass check valve with a vertical cross-section according to the present invention.

[0024] Figure 8 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along EE.

[0025] Figure 9 This is a schematic diagram of the structural principle of the device involved in the present invention, cut along FF.

[0026] Figure 10 This is a schematic diagram of the structural principle of the cross-section of the jet nozzle involved in this invention.

[0027] Figure 11 This is a schematic diagram illustrating the effect of the device involved in the present invention during low-pressure drilling.

[0028] Figure 12 This is a schematic diagram illustrating the effect of radial slit cutting in a branch pipe using the device involved in this invention.

[0029] Figure 13 This is a schematic diagram illustrating the effect of the device involved in the present invention on fracturing and permeation enhancement. Detailed implementation method:

[0030] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0031] Example 1:

[0032] This embodiment relates to an integrated branch pipe telescopic downhole slotting device, such as... Figure 1 As shown, the main structure includes an inlet 1, a high-flow overflow valve 2, a main flow channel beside the valve 3, a rubber sleeve inlet 4, a rubber sleeve 5, a fracturing fluid outlet 6, a low-flow check valve 7, a perforation channel 8, a limiting ring 9, a piston ring 10, a branch pipe 11, a return spring 12, a housing 13, a steering track 14, a jet nozzle 15, a drill bit 16, a low-pressure fluid chamber 17, and a telescopic chamber 18. The tubular housing 13 has an inlet 1 at its front end, a high-flow overflow valve 2 at its rear end, fracturing fluid channels 2-4 on both sides of the high-flow overflow valve 2, and the middle and rear parts of the fracturing fluid channels 2-4 are connected to the rubber sleeve inlet 4 of the rubber sleeve 5. Figure 2 As shown, the rubber sleeve 5 is embedded in the outer side of the casing 13. The rear end of the fracturing fluid flow channel 2-4 is connected to the fracturing fluid outlet 6. It opens when the pressure difference between the front and rear ends of the high-pass overflow valve 2 reaches 40MPa. The fracturing fluid flow channel 2-4 is used to transfer fluid to the rubber sleeve 5 and the fracturing fluid outlet 6. The rubber sleeve 5 can expand when the high-pass overflow valve 2 is opened, forming a seal between the device and the wellbore drilled by the drill bit 16, preventing the fracturing fluid from flowing out of the wellbore. Figure 3As shown, four main flow channels 3 are arranged in a circular array on the outer side of the high-pass overflow valve 2. The front end of the main flow channel 3 is connected to the inlet 1, and the rear end of the main flow channel 3 is connected to the low-pressure fluid chamber 17 with a screw-like structure. The main flow channel 3 can transfer fluid to the low-pressure fluid chamber 17 downstream of the device when the high-pass overflow valve 2 is closed. The rear end of the low-pressure fluid chamber 17 is connected to the input end of the low-pass check valve 7. The output end of the low-pass check valve 7 is connected to the drill bit 16 at the rear end of the housing 13. When the pressure difference between the front and rear ends of the low-pass check valve 7 is below 5MPa, it opens, and the fluid is supplied to the drill bit 16 through the low-pass check valve 7 to provide the fluid required for drilling. The drill bit 16 drills and forms a wellbore that penetrates deep into the coal seam or oil layer when the low-pass check valve 7 is open. Figure 4 As shown, four perforated flow channels 8 are arranged in a circular array on the outer side of the low-pass check valve 7. The front end of the perforated flow channel 8 is connected to the rear end of the low-pressure fluid chamber 17, and the rear end of the perforated flow channel 8 is connected to the telescopic branch pipe injection system. When the low-pass check valve 7 is closed, the perforated flow channel 8 can transfer fluid to the telescopic branch pipe injection system. The telescopic branch pipe injection system is equipped with a telescopic branch pipe 11.

[0033] The high-throughput overflow valve 2 involved in this embodiment consists of a valve inlet 2-1, a permanent magnet 2-2, a valve body 2-3, a fracturing fluid flow channel 2-4, a front valve return spring 2-5, a low-pressure flow channel 2-6, and a front valve chamber 2-7; as shown Figure 5 As shown, the front valve chamber 2-7 consists of a frustum-shaped front inlet cavity, a cylindrical front valve seat cavity in the middle, a cylindrical front limiting cavity in the middle and rear, and a cylindrical front valve stem cavity in the rear. The diameter of the front inlet cavity is smaller than the diameter of the front valve seat cavity, the diameter of the front valve seat cavity is larger than the diameter of the front limiting cavity, and the diameter of the front limiting cavity is larger than the diameter of the front valve stem cavity. The front end of the front valve chamber 2-7 is connected to the valve inlet 2-1, and the front end of the valve inlet 2-1 is connected to the middle of the inlet 1 pipe. A valve body 2-3 is installed in the front valve chamber 2-7. The valve body 2-3 is integrally composed of a front valve core, a front valve seat in the middle, and a front valve stem in the rear. The front valve core can be plugged into the front inlet cavity and the valve inlet 2-1 and seals the valve inlet 2-1. The rear of the front valve core is connected to the front valve seat, which is located in the front valve seat cavity. Magnetic grooves are symmetrically arranged on the upper and lower parts of the valve seat. Permanent magnets 2-2 are symmetrically installed on the upper and lower parts of the front valve seat cavity. The permanent magnets 2-2 and the magnetic grooves can be matched for a snap-fit ​​connection. The magnetic force of the permanent magnets 2-2 can cause the valve body 2-3 to open when the pressure at the valve inlet 2-1 reaches 40MPa. The valve body 2-3 moves backward, and the permanent magnets 2-2 separate from the magnetic grooves. The rear part of the front valve seat is connected to the front valve stem, and a front valve return spring 2-5 is fitted on the front valve stem. The front valve return spring 2-5 is limited in the front limit cavity, and the rear end of the front valve stem is limited in the front valve stem cavity. The maximum displacement force of the front valve return spring 2-5 is less than 1 / 200 of the maximum attraction force of the permanent magnets 2-2. The front valve return spring 2-5 can cause the valve body 2-3 to return and close when the pressure difference between the front and rear ends of the high-flow relief valve 2 is 0.2MPa. Figure 5 As shown, low-pressure flow channels 2-6 are provided on both sides of the rear end of the front valve stem cavity. These low-pressure flow channels 2-6 communicate with low-pressure fluid outside the device, thus ensuring that the valve body 2-3 remains open when the pressure difference between the front and rear ends of the high-flow relief valve 2 is above 0.2 MPa. Fracturing fluid flow channels 2-4 are symmetrically arranged on the upper and lower sides of the front valve seat cavity. Figure 6 As shown, the low-pressure flow channel 2-6 is located in the gap between the upper and lower sets of main flow channels 3 beside the valves, and the fracturing fluid flow channel 2-4 is located in the gap between the left and right sets of main flow channels 3 beside the valves.

[0034] The low-pass check valve 7 involved in this embodiment consists of a rear valve inlet 7-1, a rear valve body 7-2, a rear valve return spring 7-3, and a drill bit water hole channel 7-4; as Figure 1 , Figure 3 , Figure 7 As shown, the low-pass check valve 7 has a rear valve stem cavity at its front center. Four rear valve inlets 7-1 are arranged in a circular array around the outer side of the rear valve stem cavity. The input ends of the rear valve inlets 7-1 are connected to the rear end of the low-pressure fluid cavity 17. The rear part of the low-pass check valve 7 has a funnel-shaped rear valve cavity. The output ends of the rear valve inlets 7-1 are connected to the front end of the rear valve cavity. The rear valve cavity is integrally formed by a frustum-shaped rear valve cap cavity at the front and a cylindrical rear valve limiting cavity at the rear. A rear valve body 7-2 is provided, which is integrally formed by a front columnar rear valve stem and a rear frustum-shaped rear valve cap. The rear valve stem is connected to and limited within the rear valve stem cavity via a slot, and the rear valve cap is limited within the rear valve cap cavity. The rear end of the rear valve cap communicates with the front end of the rear valve return spring 7-3, which is installed in the rear valve limiting cavity. The rear end of the rear valve limiting cavity communicates with the front end of the drill bit water channel 7-4. Figure 1 As shown, the rear end of the drill bit water channel 7-4 is connected to the front end of the fluid injection pipe in the drill bit 16. The rear part of the fluid injection pipe is divided into two or more fluid injection branches. The preload of the rear valve return spring 7-3 is equivalent to the force borne by the rear valve body 7-2 when there is a pressure difference of 5MPa between the front and rear ends of the low-pass check valve 7, so that the rear valve body 7-2 can open under a low pressure of 5MPa. When the pressure difference between the front and rear ends of the low-pass check valve 7 is below 5MPa, the rear valve body 7-2 opens, and the fluid enters the drill bit water channel 7-4 through the rear valve inlet 7-1 and the rear valve cavity in sequence. The drill bit water channel 7-4 provides the fluid required for drilling to the drill bit 16. When the pressure difference between the front and rear ends of the low-pass check valve 7 is above 5MPa, the rear valve body 7-2 moves backward under the action of fluid pressure, the rear valve return spring 7-3 is compressed, and the rear valve body 7-2 blocks the rear valve limiting cavity at the rear of the rear valve cavity, and the low-pass check valve 7 closes.

[0035] The telescopic branch pipe injection system involved in this embodiment consists of two centrally symmetrical branches. Each branch includes a limiting ring 9, a piston ring 10, a branch pipe 11, a return spring 12, a steering track 14, a jet nozzle 15, and a telescopic cavity 18. Figure 8 As shown, the two branches are symmetrically arranged on both sides of the drill bit water channel 7-4; as Figure 1 As shown, the front end of the telescopic cavity 18 is connected to the rear end of the jet flow channel 8. A ring-shaped limiting ring 9 is provided at the front of the telescopic cavity 18, and a ring-shaped piston ring 10 is installed behind the limiting ring 9. The limiting ring 9 is used to limit the piston ring 10, which can move within the telescopic cavity 18. The rear end of the piston ring 10 is connected to the front end of the branch pipe 11. The branch pipe 11 is composed of an elastic steel pipe with a length of 2m-4m and an outer diameter of 4mm-8mm. A return spring 12 is sleeved on the outside of the branch pipe 11. The return spring 12 is limited in the rear half of the telescopic cavity 18. The preload of the return spring 12 can withstand the extension thrust of the branch pipe 11 when there is a 20MPa pressure difference inside and outside the jet nozzle 15. When the branch pipe 11 retracts, the return spring 12 provides a return force to the branch pipe 11. The rear end of the telescopic cavity 18 is connected to the front end of the steering track 14. The steering track 14 is arc-shaped, as shown... Figure 9 As shown, the steering track 14 can turn the branch pipe 11 90 degrees and extend it radially from the telescopic cavity 18; a jet nozzle 15 is installed at the rear end of the branch pipe 11. When the pressure difference between the front end pressure of the piston ring 10 and the outer pressure of the jet nozzle 15 reaches more than 20MPa, the fluid can push the piston ring 10 to provide an extension thrust for the branch pipe 11.

[0036] The jet nozzle 15 involved in this embodiment is composed of an angled nozzle 15-1, a secondary oscillation chamber 15-2, and a primary oscillation chamber 15-3, as follows: Figure 10 As shown, the primary oscillation chamber 15-3 is a funnel-shaped cavity. The front end of the primary oscillation chamber 15-3 is connected to the output end of the branch pipe 11. The funnel-shaped output end of the primary oscillation chamber 15-3 is connected to the front end of the funnel-shaped secondary oscillation chamber 15-2. The funnel-shaped output end of the secondary oscillation chamber 15-2 is connected to the front end of the trumpet-shaped angular nozzle 15-1. The primary oscillation chamber 15-3 can generate a strengthened pulsed cavitation cone jet to efficiently break rocks, thereby forming a slit larger than the outer diameter of the branch pipe 11.

[0037] The integrated branch pipe telescopic downhole slotting device involved in this embodiment achieves radial water jet slotting and fracturing of telescopic branch pipes, including: low-pressure drilling, medium-low pressure slotting, medium-pressure permeability enhancement, and device recovery; the specific steps are as follows:

[0038] (1) Low-pressure drilling: The integrated branch pipe telescopic downhole slotting device is connected to the surface booster pump via the drill pipe. The fluid pressure at the pump inlet 1 is controlled to be below 5 MPa. The high-flow overflow valve 2 is closed, and the main flow channel 3 beside the valve transfers the fluid to the low-pressure fluid chamber 17 downstream of the device. At this time, the pressure difference between the front and rear ends of the low-flow check valve 7 is less than 5 MPa and remains open. The fluid in the low-pressure fluid chamber 17 enters the drill bit water channel 7-4 sequentially through the rear valve inlet 7-1 and the rear valve chamber. The drill bit water channel 7-4 provides the fluid required for drilling to the drill bit 16. The drill pipe drives the tool and drill bit to rotate and advance. Figure 11 As shown, a wellbore tens of meters long was drilled in the coal seam;

[0039] (2) Medium and low pressure cutting: The fluid pressure at the pump inlet 1 is increased to 20MPa, the high-pass overflow valve 2 is closed, and the main flow channel 3 beside the valve transfers the fluid to the low-pressure fluid chamber 17 downstream of the device. At this time, the pressure difference between the front and rear ends of the low-pass check valve 7 is greater than 5MPa and it is closed. The fluid in the low-pressure fluid chamber 17 is transferred to the telescopic branch pipe injection system through the perforation channel 8. The fluid mainly flows out to the outside of the device through the branch pipe 11. The control device and the drill bit 16 rotate in place, and the pressure difference between the front end pressure of the piston ring 10 and the outer pressure of the jet nozzle 15 is... The system provides thrust for the extension of branch pipe 11, gradually increasing the fluid pressure at inlet 1 to 35 MPa, causing branch pipe 11 and nozzle 15 to extend slowly while rotating and cutting the rock. The jet nozzle 15 intensifies the fluid into a pulsed cavitation cone jet for efficient rock breaking and cutting. Then, the fluid pressure at inlet 1 is reduced to 15 MPa, causing branch pipe 11 and nozzle 15 to retract under the force of return spring 12. The control device and drill bit retract 0.5m-2m, and the cutting process is repeated to perform jet rotation cutting, with the cutting state as shown. Figure 12 As shown;

[0040] (3) Medium-pressure permeation enhancement: After the wellbore is filled with predetermined slots by jetting, the fluid pressure at inlet 1 is increased to 45MPa. At this time, the high-pass overflow valve 2 is opened, and the fluid enters the front valve seat cavity through valve inlet 2-1. The fluid in the front valve seat cavity enters the fracturing fluid channel 2-4, and the fluid enters the rubber sleeve 5 through the rubber sleeve inlet 4. The rubber sleeve 5 expands and seals the annular space gap between the device and the wellbore. Then the fluid flows out through the fracturing fluid outlet 6 to perform fracturing and permeation enhancement operations on the slots. At the same time, since the flow rate at the outer outlet of the fracturing fluid outlet 6 is more than 10 times that of the nozzle 15, and the annular pressure gradually increases, the pressure difference between the front end pressure of the piston ring 10 and the outer pressure of the jet nozzle 15 will be less than 20MPa. The branch pipe 11 and the nozzle 15 remain in a contracted state under the elastic force of the return spring 12. The permeation enhancement effect diagram is shown in the figure. Figure 13 As shown;

[0041] (4) Equipment recovery: After the fracturing and permeation enhancement operations are completed, the pump is stopped and the pressure is released. After the rubber sleeve 5 retracts back into place, the drill rod and equipment are recovered.

[0042] The working principle of the integrated branch pipe telescopic downhole slotting device described in this embodiment is as follows:

[0043] The well drilling, jet fracturing, and fracturing enhancement are divided into three processes by adjusting the inlet fluid pressure from low to high. The flow channels of the drill bit water inlet, jet fracturing nozzle, and fracturing channel can be switched by a valve that can be opened and closed under rated pressure, thereby realizing the integrated technology of drilling, fracturing, and fracturing enhancement. The jet fracturing at a small spray distance is achieved by gradually extending the branch pipe 11 and nozzle 15 under the drive of jet pressure difference, which reduces the energy loss of water jet and realizes jet fracturing at medium and low pressure. At the same time, the nozzle 15 with a multi-stage pulse cone structure increases the fracturing diameter and reduces the jet fracturing threshold pressure.

Claims

1. An integrated branch pipe telescopic downhole slotting device, characterized in that: The system includes an inlet, a high-flow relief valve, a main flow channel beside the valve, a cartridge inlet, a cartridge, a fracturing fluid outlet, a low-flow check valve, a perforation channel, a casing, a drill bit, a low-pressure fluid chamber, and a telescopic branch pipe injection system. The tubular casing has an inlet at its front end and a high-flow relief valve at its rear end. Fracturing fluid channels are located on both sides of the high-flow relief valve. The middle and rear parts of the fracturing fluid channels connect to the cartridge inlet of the cartridge. The cartridge is embedded in the outer side of the casing. The rear end of the fracturing fluid channels connects to the fracturing fluid outlet. When the pressure difference between the front and rear ends of the high-flow relief valve reaches 40 MPa, the high-flow relief valve opens, and the fracturing fluid channels transfer fluid to the cartridge and the fracturing fluid outlet. Four main flow channels beside the valve are arranged in a circular array on the outer side of the high-flow relief valve. The front end of each main flow channel connects to the inlet, and the rear end connects to the screw-shaped low-pressure fluid chamber. The main flow channel beside the valve can transfer fluid to the low-pressure fluid chamber downstream of the device when the high-flow relief valve is closed; the rear end of the low-pressure fluid chamber is connected to the input end of the low-flow check valve; the output end of the low-flow check valve is connected to the drill bit at the rear end of the housing. When the pressure difference between the front and rear ends of the low-flow check valve is below 5MPa, the low-flow check valve opens, and the fluid is supplied to the drill bit through the low-flow check valve to provide the fluid required for drilling. The drill bit drills and forms a wellbore deep into the coal seam or oil layer when the low-flow check valve is open; four perforation channels are arranged in a circular array on the outer side of the low-flow check valve. The front end of the perforation channel is connected to the rear end of the low-pressure fluid chamber, and the rear end of the perforation channel is connected to the telescopic branch pipe injection system. When the low-flow check valve is closed, the perforation channel can transfer fluid to the telescopic branch pipe injection system; the telescopic branch pipe injection system is equipped with a telescopic branch pipe.

2. The integrated branch pipe telescopic downhole slotting device according to claim 1, characterized in that: The high-flow overflow valve consists of a valve inlet, a permanent magnet, a valve body, a fracturing fluid flow channel, a front valve return spring, a low-pressure flow channel, and a front valve chamber. The front valve chamber comprises a frustum-shaped front inlet cavity, a cylindrical front valve seat cavity, a cylindrical front limiting cavity, and a cylindrical front valve stem cavity. The diameter of the front inlet cavity is smaller than the diameter of the front valve seat cavity, the diameter of the front valve seat cavity is larger than the diameter of the front limiting cavity, and the diameter of the front limiting cavity is larger than the diameter of the front valve stem cavity. The front end of the front valve chamber is connected to the valve inlet, and the front end of the valve inlet is connected to the middle of the inlet pipe. The valve body is installed in the front valve chamber, and the valve body is integrally composed of a front valve core, a middle front valve seat, and a rear front valve stem. It can be plugged into the front inlet cavity and valve inlet and block the valve inlet; the rear of the front valve core is connected to the front valve seat, which is limited in the front valve seat cavity. The front valve seat is symmetrically provided with magnetic grooves on the upper and lower sides. The front valve seat cavity is symmetrically installed with permanent magnets on the upper and lower sides. The permanent magnets and magnetic grooves can be matched and connected by a slot; the rear of the front valve seat is connected to the front valve stem, and the front valve return spring is fitted on the front valve stem. The front valve return spring is limited in the front limit cavity. The rear end of the front valve stem is limited in the front valve stem cavity. Low-pressure flow channels are provided on both sides of the rear end of the front valve stem cavity. The low-pressure flow channels are connected to the low-pressure fluid outside the device, so as to keep the valve body in the open state when the pressure difference between the front and rear ends of the high-pass overflow valve is above 0.2MPa.

3. The integrated branch pipe telescopic downhole slotting device according to claim 2, characterized in that: The magnetic force of the permanent magnet enables the valve body to open when the pressure at the valve inlet reaches 40MPa, and the valve body moves backward, separating the permanent magnet from the magnetic groove; the maximum displacement force of the front valve return spring is less than 1 / 200 of the maximum attraction force of the permanent magnet, and the front valve return spring enables the valve body to return and close when the pressure difference between the front and rear ends of the high-pass overflow valve is 0.2MPa.

4. The integrated branch pipe telescopic downhole slotting device according to claim 3, characterized in that: The upper and lower sides of the front valve seat cavity are symmetrically provided with fracturing fluid channels; the low-pressure channel is located in the gap between the upper and lower sets of main channels beside the valve, and the fracturing fluid channel is located in the gap between the left and right sets of main channels beside the valve.

5. The integrated branch pipe telescopic downhole slotting device according to claim 4, characterized in that: The low-pass check valve consists of a rear valve inlet, a rear valve body, a rear valve return spring, and a drill bit water channel. A rear valve stem cavity is located at the center of the front part of the low-pass check valve. Four rear valve inlets are arranged in a circular array around the outer side of the rear valve stem cavity. The input end of each rear valve inlet is connected to the rear end of the low-pressure fluid cavity. A funnel-shaped rear valve cavity is located at the rear of the low-pass check valve. The output end of each rear valve inlet is connected to the front end of the rear valve cavity. The rear valve cavity is integrally formed by a frustum-shaped rear valve cap cavity at the front and a cylindrical rear valve limiting cavity at the rear. The low-pass check valve contains a rear valve... The valve body is composed of a front columnar valve stem and a rear frustum-shaped valve cap. The rear valve stem is connected to the rear valve stem cavity by a slot and is limited in the rear valve stem cavity. The rear valve cap is limited in the rear valve cap cavity. The rear end of the rear valve cap is connected to the front end of the rear valve return spring. The rear valve return spring is limited and installed in the rear valve limiting cavity. The rear end of the rear valve limiting cavity is connected to the front end of the drill bit water eye channel. The rear end of the drill bit water eye channel is connected to the front end of the fluid injection pipe in the drill bit. The rear part of the fluid injection pipe is divided into two or more fluid injection branches.

6. The integrated branch pipe telescopic downhole slotting device according to claim 5, characterized in that: The preload of the rear valve return spring is equivalent to the force exerted on the rear valve body when there is a 5MPa pressure difference between the front and rear ends of the low-pass check valve, thus enabling the rear valve body to open under a low pressure of 5MPa. When the pressure difference between the front and rear ends of the low-pass check valve is below 5MPa, the rear valve body opens, and the fluid sequentially enters the drill bit water channel through the rear valve inlet and the rear valve chamber, providing the drill bit with the fluid required for drilling. When the pressure difference between the front and rear ends of the low-pass check valve is above 5MPa, the rear valve body moves backward under the action of fluid pressure, the rear valve return spring is compressed, and the rear valve body blocks the rear valve limiting chamber at the rear of the rear valve chamber, thus closing the low-pass check valve.

7. The integrated branch pipe telescopic downhole slotting device according to claim 6, characterized in that: The telescopic branch pipe injection system consists of two centrally symmetrical branches. Each branch includes a limiting ring, a piston ring, a branch pipe, a return spring, a steering rail, a jet nozzle, and a telescopic cavity. The two branches are symmetrically arranged on both sides of the drill bit's water passage. The front end of the telescopic cavity is connected to the rear end of the perforation passage. A ring-shaped limiting ring is installed at the front of the telescopic cavity, and a ring-shaped piston ring is installed behind the limiting ring. The limiting ring is used to limit the piston ring, which can move within the telescopic cavity. The rear end of the piston ring is connected to the front end of the branch pipe, which is a flexible steel pipe with a length of 2m-4m and an outer diameter of 4mm-8mm. The system consists of a branch pipe with a return spring sleeved on the outside. The return spring is limited to the rear half of the telescopic cavity. The preload of the return spring can withstand the extension thrust of the branch pipe when there is a pressure difference of 20MPa inside and outside the jet nozzle. When the branch pipe retracts, the return spring provides a return force to the branch pipe. The rear end of the telescopic cavity is connected to the front end of the steering track. The steering track is arc-shaped and can turn the branch pipe 90 degrees to extend radially from the telescopic cavity. The rear end of the branch pipe is equipped with a jet nozzle. When the pressure difference between the front end of the piston ring and the outside of the jet nozzle reaches more than 20MPa, the fluid can push the piston ring to provide an extension thrust for the branch pipe.

8. The integrated branch pipe telescopic downhole slotting device according to claim 7, characterized in that: The jet nozzle consists of an angular nozzle, a secondary oscillating chamber, and a primary oscillating chamber. The primary oscillating chamber is a funnel-shaped cavity. The front circular tube of the primary oscillating chamber is connected to the output end of the branch pipe. The funnel-shaped output end of the primary oscillating chamber is connected to the front circular tube of the funnel-shaped secondary oscillating chamber. The funnel-shaped output end of the secondary oscillating chamber is connected to the front end of the horn-shaped nozzle. The primary oscillating chamber can generate a strengthened pulsed cavitation cone jet to efficiently break rocks, thereby forming a slit larger than the outer diameter of the branch pipe.

9. The integrated branch pipe telescopic downhole slotting device according to claim 8, characterized in that: The integrated branch pipe telescopic downhole fracturing device enables radial water jet fracturing and fracture treatment of telescopic branch pipes, including: low-pressure drilling, medium-low pressure fracturing, medium-pressure permeability enhancement, and device recovery; the specific steps are as follows: (1) Low-pressure drilling: The integrated branch pipe telescopic downhole slotting device is connected to the surface booster pump through the drill pipe. The fluid pressure at the pump inlet is controlled to be below 5MPa. The high-pass overflow valve is closed. The main channel beside the valve transmits the fluid to the low-pressure fluid chamber downstream of the device. At this time, the pressure difference between the front and rear ends of the low-pass check valve is less than 5MPa and it remains open. The fluid in the low-pressure fluid chamber enters the drill bit water channel through the rear valve inlet and the rear valve chamber in sequence. The drill bit water channel provides the fluid required for drilling to the drill bit. The drill pipe drives the tool and the drill bit to rotate and advance, drilling a wellbore of tens of meters in the coal seam. (2) Medium and low pressure slotting: Increase the fluid pressure at the pump inlet to 20MPa, the high-pass overflow valve is closed, and the main flow channel beside the valve transfers the fluid to the low-pressure fluid chamber downstream of the device. At this time, the pressure difference between the front and rear ends of the low-pass check valve is greater than 5MPa and is closed. The fluid in the low-pressure fluid chamber is transferred to the telescopic branch pipe jet system through the perforation channel. The fluid mainly flows out to the outside of the device through the branch pipe. The control device and drill bit rotate in place. The pressure difference between the front end pressure of the piston ring and the outside pressure of the jet nozzle can provide the extension thrust of the branch pipe. Slowly and gradually increase the fluid pressure at the inlet to 35MPa, so that the branch pipe and jet nozzle slowly extend while rotating the slotting. The jet nozzle strengthens the fluid into a pulse cavitation cone jet for efficient rock breaking slotting. Then, reduce the fluid pressure at the inlet to 15MPa, so that the branch pipe and jet nozzle return to their original positions under the spring force of the return spring. The control device and drill bit retreat 0.5m-2m, and repeat the above slotting process to perform jet rotation slotting. (3) Medium-pressure permeation enhancement: After the wellbore is filled with the predetermined cuts by the jet, the fluid pressure at the inlet is increased to 45MPa. At this time, the high-pass overflow valve is opened, and the fluid enters the front valve seat cavity from the valve inlet. The fluid in the front valve seat cavity enters the fracturing fluid channel. The fluid enters the rubber sleeve from the fracturing fluid channel through the rubber sleeve inlet. The rubber sleeve expands and seals the annular space gap between the device and the wellbore. Then the fluid flows out through the fracturing fluid outlet to perform fracturing and permeation enhancement operations on the cuts. At the same time, since the flow rate of the fracturing fluid outlet is more than 10 times that of the jet nozzle, and the annular pressure gradually increases, the pressure difference between the front pressure of the piston ring and the pressure outside the jet nozzle will be less than 20MPa. The branch pipe and the jet nozzle remain in a contracted state under the elastic force of the return spring. (4) Equipment recovery: After the fracturing and permeation enhancement operations are completed, the pump is stopped and the pressure is released. After the rubber sleeve shrinks back to its original position, the drill rod and equipment are recovered.

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