A fracturing and plugging removal system and method for coalbed methane horizontal wells

Abstract

The present invention discloses a fracturing and plugging removal system and method for coalbed methane horizontal wells. The system includes a fracturing pump truck, a tubing string, a pressure relief and flushing valve, a controllable shock wave fracturing device, and a guide cone connected in sequence. The pressure relief and flushing valve is provided with a pressure transmitter connected to the controllable shock wave fracturing device, a flushing valve for ejecting high-pressure water to remove the plugging in the wellbore, and a drain valve for discharging the residual water in the tubing string. The method includes the following steps: First, pushing the controllable shock wave fracturing device; Second, controlling the operation of the controllable shock wave fracturing device; Third, fracturing the next coal seam section to be fractured; Fourth, removing the plugging in the wellbore; Fifth, repeating steps three to four until the shock wave operation of all coal seam sections to be fractured is completed; Sixth, draining the water in the tubing string. The fracturing and plugging removal system and method for coalbed methane horizontal wells provided by the present invention solve the problem that the moving channel of the controllable shock wave fracturing device is blocked by coal powder, and can drain the water in the tubing string when the tubing string is removed.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy extraction, and particularly relates to a fracturing and plugging removal system and method for coalbed methane horizontal wells. Background Art

[0002] Coalbed methane is a new type of energy with high heat, cleanness and convenience. The "Dynamic Evaluation of Coalbed Methane Resources" organized by the Ministry of Land and Resources in 2015 showed that the total coalbed methane resources were approximately 30 trillion cubic meters, and the recoverable resources were approximately 1.25 trillion cubic meters, ranking third in the world's coalbed methane resources, accounting for about 11.2% - 13.7% of the global resource reserves. Although the coalbed methane industry has been working hard, due to the influence of various factors, its actual development is far lower than expected. However, the resource extraction potential of coalbed methane is still huge.

[0003] The patent "Coalbed Methane Horizontal Well Plugging Removal and Permeability Enhancement Completion Method" with the application number 201910811069.5 and the patent "Coalbed Methane Regional Production Enhancement Method" with the application number 201910894890.8 respectively proposed methods for plugging removal and permeability enhancement of coalbed methane horizontal wells using controllable shock wave technology, and methods for regional permeability enhancement and production increase using horizontal wells. However, there are various problems when implementing shock wave operations in horizontal wells with controllable shock wave technology. For example, coal powder in the coal seam is likely to block the moving channel of the controllable shock wave fracturing device, thereby affecting the pushing of the controllable shock wave fracturing device and the efficiency of permeability enhancement of the horizontal well. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a fracturing and plugging removal system for coalbed methane horizontal wells in view of the above-mentioned deficiencies in the prior art. This system solves the problem that the moving channel of the controllable shock wave fracturing device is blocked by coal powder, can discharge the water in the oil pipe when pulling out the oil pipe, and is convenient for pushing the controllable shock wave fracturing device into the horizontal well. Therefore, it has strong practicability and is convenient for popularization and use.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: A fracturing and plugging removal system for coalbed methane horizontal wells, comprising a fracturing pump truck, an oil pipe, a pressure relief flushing valve, a controllable shock wave fracturing device and a guide cone connected in sequence;

[0006] The pressure relief and flushing valve includes a valve body, a pressure transmitter, a flushing valve for spraying high-pressure water to unblock the coalbed methane horizontal wellbore, and a drain valve for discharging residual water in the oil pipe, all of which are arranged in the valve body. The two ends of the valve body are respectively provided with an oil pipe docking cavity and a controllable shock wave fracturing device docking cavity. A water guiding hole communicating with both the oil pipe docking cavity and the controllable shock wave fracturing device docking cavity is opened in the valve body. The pressure sensing end of the pressure transmitter is inserted into the water guiding hole, and the data transmission end of the pressure transmitter is connected to the data receiving end of the controllable shock wave fracturing device. Drain holes and flushing holes communicating with the water guiding hole are opened on the side wall of the valve body. The drain valve is located in the drain hole, and the flushing valve is located in the flushing hole.

[0007] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, the drain hole includes a first threaded hole section and a first through hole section. The drain valve is installed in the first threaded hole section, and the aperture of the first threaded hole section is larger than that of the first through hole section. The drain valve includes a stud and a bursting disc abutted against the stud. The bursting disc is located at one end of the first threaded hole section close to the first through hole section, and a drain through hole for draining water is provided along the axis of the stud.

[0008] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, the flushing hole includes a second threaded hole section and a second through hole section. The aperture of the second threaded hole section is larger than that of the second through hole section. The flushing valve includes a plunger, a spring, and a flushing column connected in sequence. One end of the plunger is located in the second through hole section, and the other end of the plunger, the spring, and the flushing column are all located in the second threaded hole section. A water guiding groove is provided along the axial direction on the outer wall of one end of the plunger located in the second through hole section. A flushing sealing ring is provided at one end of the plunger located in the second through hole section and close to the spring. There is a gap between the other end of the plunger and the inner wall of the second threaded hole section. A flushing through hole for discharging high-pressure water is provided along the axis of the flushing column.

[0009] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, the oil pipe extends into the oil pipe docking cavity and is threadedly connected to the valve body, and the controllable shock wave fracturing device extends into the controllable shock wave fracturing device docking cavity and is threadedly connected to the valve body.

[0010] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, both the drain hole and the flushing hole are inclined towards the direction of the controllable shock wave fracturing device docking cavity.

[0011] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, a counterweight pipe is sleeved on the part of the oil pipe located in the vertical section of the horizontal well.

[0012] In the above-mentioned fracturing and unblocking system for coalbed methane horizontal wells, the fracturing pump truck is placed on the ground. The guiding cone includes a cylindrical connecting pipe and a guiding head connected to the connecting pipe. The end of the guiding head is conical, and the connecting pipe is detachably connected to the controllable shock wave fracturing device.

[0013] For the above-mentioned fracturing and plugging removal system for coalbed methane horizontal wells, the cone angle at the end of the guide head is 30 degrees.

[0014] Meanwhile, the present invention also discloses a fracturing and plugging removal method for coalbed methane horizontal wells, which has simple method steps, reasonable design, and is convenient for pushing the controllable shock wave fracturing device into the horizontal well. The method includes the following steps:

[0015] Step 1, pushing the controllable shock wave fracturing device: Push the controllable shock wave fracturing device to the coal seam section to be fractured at the deepest part of the horizontal well.

[0016] Step 2, controlling the operation of the controllable shock wave fracturing device: Use a fracturing pump truck to pump water pressure into the oil pipe, collect the water pressure value of the water in the water guiding hole through a pressure transmitter. When the water pressure value collected by the pressure transmitter reaches the first water pressure threshold, the controllable shock wave fracturing device starts, and the controllable shock wave fracturing device performs N times of shock wave operations on the coal seam section to be fractured at the deepest part of the coal seam, and then the controllable shock wave fracturing device automatically closes. Here, N is a positive integer and the value range of N is 2 to 10.

[0017] Step 3, fracturing the next coal seam section to be fractured: Move the controllable shock wave fracturing device outward from the coal seam in a layer-by-layer upward return manner, and perform shock wave operations on the next coal seam section to be fractured through the controllable shock wave fracturing device. The way the controllable shock wave fracturing device performs shock wave operations on the next coal seam section to be fractured is the same as the way the controllable shock wave fracturing device performs shock wave operations on the coal seam section to be fractured at the deepest part of the coal seam in Step 2.

[0018] Step 4, plugging removal of the wellbore: When the channel through which the controllable shock wave fracturing device moves in the coalbed methane horizontal wellbore is blocked by coal powder, use a fracturing pump truck to pump water pressure into the oil pipe. When the water pressure value in the oil pipe reaches the second water pressure threshold, the controllable shock wave fracturing device starts. At the same time, the water in the oil pipe sprays out through the flushing valve. The shock wave generated by the controllable shock wave fracturing device scatters the coal powder, and the high-pressure water sprayed out by the flushing valve flushes away the coal powder, thereby dredging the channel. After the channel is dredged, reduce the water pressure so that the water pressure value is lower than the first water pressure threshold, and the water stops spraying out from the flushing valve, and the controllable shock wave fracturing device automatically closes. Here, the second water pressure threshold is greater than the first water pressure threshold.

[0019] Step 5, repeat Step 3 to Step 4 until all shock wave operations on the coal seam sections to be fractured are completed.

[0020] Step 6. Drainage of the tubing: Use a fracturing pump truck to pump water pressure into the tubing. When the water pressure value in the tubing reaches the third water pressure threshold, the bursting disc bursts, and the water in the tubing passes through the bursting disc and is discharged through the drainage holes. At the same time, the water in the tubing is ejected through the flushing valve. Then, turn off the fracturing pump truck. When the water pressure value in the tubing is less than the second water pressure threshold, the flushing valve 13 automatically closes. After the water in the tubing is emptied, lift out the tubing, and then retract the pressure relief flushing valve, the controllable shock wave fracturing device, and the guide cone, thus completing the fracturing of the coal seam in the horizontal well. Among them, the third water pressure threshold is greater than the second water pressure threshold.

[0021] In the above method, it is characterized in that: the first water pressure threshold is 12 - 17 Mpa, the second water pressure threshold is 18 - 22 Mpa, and the third water pressure threshold is 23 - 27 Mpa.

[0022] The present invention has the following advantages compared with the prior art:

[0023] 1. The system of the present invention starts the controllable shock wave fracturing device through a pressure transmitter, which can eliminate the cable used to control the controllable shock wave fracturing device inside the tubing. Therefore, the structure of the pushing assembly of the controllable shock wave fracturing device is simplified, and the cost is saved, which is convenient for popularization and use.

[0024] 2. The flushing valve of the system of the present invention can discharge high-pressure water by opening the flushing valve. The high-pressure water can disperse and unclog the coal powder around the controllable shock wave fracturing device. Therefore, the use effect is good. When the flushing valve discharges high-pressure water, the controllable shock wave fracturing device starts simultaneously. The shock wave generated by the controllable shock wave fracturing device disperses the coal powder. The two ways of unclogging are carried out simultaneously, making the unclogging efficiency higher and the effect better.

[0025] 3. The drainage valve of the system of the present invention can drain the water in the tubing into the wellbore after the coal seam fracturing is completed. Therefore, when the tubing is lifted out, the tubing will no longer discharge sewage into the well site, and thus will not pollute the environment.

[0026] 4. The present invention eliminates the cable used to control the controllable shock wave fracturing device inside the tubing. Therefore, the tubing of the present invention has a smaller diameter compared with the tubing in the prior art. During pushing, the self-weight of the tubing and the weight of the counterweight pipe can be used to push the controllable shock wave fracturing device in the horizontal well. Therefore, the pushing process of the present invention is smoother, with less frictional resistance, avoiding the problem that a drilling rig needs to be used to apply thrust to smoothly push the controllable shock wave fracturing device.

[0027] 5. When the present invention pushes the controllable shock wave fracturing device, it can smoothly pass through the steps of the coalbed methane horizontal wellbore with different pipe diameters under the guidance of the guide cone.

[0028] 6. The method of the present invention can dredge the channel for the movement of the controllable shock wave fracturing device in the wellbore of the coalbed methane horizontal well and avoid the problem of sewage discharge from the tubing when the tubing is removed from the well, thus ensuring the smooth progress of the fracturing of the coalbed methane horizontal well, improving the efficiency of permeability enhancement of the horizontal well, and having good use effect.

[0029] In summary, the present invention solves the problem that the movement channel of the controllable shock wave fracturing device is blocked by coal powder, can discharge the water in the tubing when the tubing is removed, and is convenient to push the controllable shock wave fracturing device into the horizontal well. Therefore, it has strong practicability and is convenient for popularization and use.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of a fracturing and plugging removal system for a coalbed methane horizontal well provided by an embodiment of the present invention.

[0032] Figure 2 It is a schematic structural diagram of a pressure relief flushing valve provided by an embodiment of the present invention.

[0033] Figure 3 It is a schematic structural diagram of a valve body provided by an embodiment of the present invention.

[0034] Figure 4 It is a schematic structural diagram of a drain valve provided by an embodiment of the present invention.

[0035] Figure 5 It is a schematic structural diagram of a flushing valve provided by an embodiment of the present invention.

[0036] Figure 6 It is a schematic structural diagram of a guiding cone provided by an embodiment of the present invention.

[0037] Figure 7 It is a flow chart of a fracturing and plugging removal method for a coalbed methane horizontal well provided by an embodiment of the present invention.

[0038] Description of the Reference Numerals:

[0039] 1 - pressure relief flushing valve; 2 - docking cavity of the controllable shock wave fracturing device; 3 - valve body; 4 - tubing docking cavity; 5 - pressure transmitter; 6 - controllable shock wave fracturing device; 7 - tubing; 8 - drain hole; 8-1 - first threaded hole section; 8-2 - first through hole section; 9 - flushing hole; 9-1 - second threaded hole section; 9-2 - second through hole section; 10 - drain valve; 11 - stud; 12 - bursting disc; 13 - flushing valve; 14 - plunger; 15 - spring; 16 - flushing column; 17 - flushing sealing ring; 18 - water guide groove; 19 - guiding cone; 20 - coal seam; 21 - water guide hole; 22 - fracturing pump truck; 23 - connecting pipe; 24 - guiding head. Detailed implementation mode

[0040] As Figures 1 to 6 shown, the system of the present invention includes a fracturing pump truck 22, a tubing 7, a pressure relief flushing valve 1, a controllable shock wave fracturing device 6 and a guide cone 19 that are connected in sequence;

[0041] The pressure relief flushing valve 1 includes a valve body 3, a pressure transmitter 5, a flushing valve 13 for spraying high-pressure water to unblock the coalbed methane horizontal wellbore, and a drain valve 10 for discharging the residual water in the tubing 7, all of which are arranged in the valve body 3. Tubing docking cavities 4 and a controllable shock wave fracturing device docking cavity 2 are respectively provided at both ends of the valve body 3. A water guiding hole 21 that communicates with both the tubing docking cavity 4 and the controllable shock wave fracturing device docking cavity 2 is opened in the valve body 3. The pressure sensing end of the pressure transmitter 5 is inserted into the water guiding hole 21, and the data transmission end of the pressure transmitter 5 is connected to the data receiving end of the controllable shock wave fracturing device 6. Drain holes 8 and flushing holes 9 that communicate with the water guiding hole 21 are opened on the side wall of the valve body 3. The drain valve 10 is located in the drain hole 8, and the flushing valve 13 is located in the flushing hole 9.

[0042] It should be noted that the tubing 7 is connected to the pressure relief flushing valve 1 through the tubing docking cavity 4, and the controllable shock wave fracturing device 6 is connected to the pressure relief flushing valve 1 through the controllable shock wave fracturing device docking cavity 2.

[0043] The pressure sensing end of the pressure transmitter 5 can convert the real-time detected water pressure value into an electrical signal and send it to the controllable shock wave fracturing device 6, thereby controlling the start of the controllable shock wave fracturing device 6. Furthermore, when the fracturing pump truck 22 pumps water pressure into the tubing 7, the controllable shock wave fracturing device 6 can be started. Starting the controllable shock wave fracturing device 6 through the pressure transmitter 5 can eliminate the cable used to control the controllable shock wave fracturing device 6 in the tubing 7, thereby simplifying the structure of the pushing component of the controllable shock wave fracturing device 6 and saving costs.

[0044] The fracturing pump truck 22 pumps water pressure into the oil pipe 7, and the water flow in the oil pipe 7 guides to the water conduction holes 21, the drainage holes 8 and the scouring holes 9. When the water pressure value in the oil pipe 7 reaches the first water pressure threshold, the controllable shock wave fracturing device 6 is activated, and then the controllable shock wave fracturing device 6 performs shock wave operations on the coal seam 20 section; when the water pressure value in the oil pipe 7 reaches the second water pressure threshold, the controllable shock wave fracturing device 6 is activated, and at the same time, the water in the oil pipe 7 sprays out through the scouring valve 13. The shock wave generated by the controllable shock wave fracturing device 6 disperses the coal powder, and the high-pressure water sprayed out by the scouring valve 13 flushes the coal powder, thereby dredging the channel through which the controllable shock wave fracturing device 6 moves in the coalbed methane horizontal wellbore; when the water pressure value in the oil pipe 7 reaches the third water pressure threshold, the controllable shock wave fracturing device 6 is activated, and at the same time, the water in the oil pipe 7 sprays out through the scouring valve 13, and the water in the oil pipe 7 is discharged through the drainage valve 10. At this time, since the controllable shock wave fracturing device 6 has completed the fracturing of the coalbed methane horizontal well, the consumables inside it have been consumed, so no shock wave will be generated. During the process of discharging the water in the oil pipe 7, when the water pressure value in the oil pipe 7 is less than the second water pressure threshold, the scouring valve 13 automatically closes, and then the water in the oil pipe 7 stops spraying out from the scouring valve 13. The drainage valve 10 is in an always-open state after being opened, so the water in the oil pipe 7 can be drained out completely.

[0045] In this embodiment, as Figure 4 shown, the drainage hole 8 includes a first threaded hole section 8-1 and a first through hole section 8-2. The drainage valve 10 is installed in the first threaded hole section 8-1, and the aperture of the first threaded hole section 8-1 is larger than that of the first through hole section 8-2; the drainage valve 10 includes a stud 11 and a bursting disc 12 abutted against the stud 11. The bursting disc 12 is located at one end of the first threaded hole section 8-1 close to the first through hole section 8-2, and the stud 11 is provided with a drainage through hole for draining water along its axis.

[0046] It should be noted that the first threaded hole section 8-1 extends to the outer wall of the pressure relief scouring valve 1, so it is convenient to debug and maintain the drainage valve 10.

[0047] After the water pressure in the drainage hole 8 reaches the threshold value at which the bursting disc 12 bursts, that is, the third water pressure threshold, the bursting disc 12 bursts, so that the water in the oil pipe 7 can pass through the bursting disc 12 and be discharged through the drainage through hole of the stud 11.

[0048] In this embodiment, as Figure 5As shown, the flushing hole 9 includes a second threaded hole section 9-1 and a second through hole section 9-2, and the aperture of the second threaded hole section 9-1 is larger than that of the second through hole section 9-2; the flushing valve 13 includes a plunger 14, a spring 15 and a flushing column 16 connected in sequence. One end of the plunger 14 is located in the second through hole section 9-2, and the other end of the plunger 14, the spring 15 and the flushing column 16 are all located in the second threaded hole section 9-1. A water guide groove 18 is provided on the outer wall of the end of the plunger 14 located in the second through hole section 9-2 along its axial direction. A flushing sealing ring 17 is provided at the end of the plunger 14 located in the second through hole section 9-2 and close to the spring 15. There is a gap between the other end of the plunger 14 and the inner wall of the second threaded hole section 9-1. The flushing column 16 is provided with a flushing through hole for discharging high-pressure water along its axis.

[0049] It should be noted that the second threaded hole section 9-1 extends to the outer wall of the pressure relief flushing valve 1, so it is convenient to debug and maintain the flushing valve 13.

[0050] After the water pressure in the flushing hole 9 reaches the threshold value for the flushing valve 13 to drain water, that is, the second water pressure threshold value, the spring 15 compresses, and at the same time the whole plunger 14 moves towards the second threaded hole section, so that the flushing sealing ring 17 moves into the second threaded hole section. At this time, both sides of the water guide groove 18 of the plunger 14 are located in the second threaded hole section and the second through hole section respectively. The water in the oil pipe 7 is discharged from the flushing hole 9 through the water guide groove 18 and the flushing through hole. The sprayed high-pressure water can disperse the pulverized coal in the channel blocking the movement of the controllable shock wave cracker 6, and then dredge the channel of the controllable shock wave cracker 6.

[0051] In this embodiment, the oil pipe 7 extends into the oil pipe docking cavity 4 and is threadedly connected to the valve body 3, and the controllable shock wave cracker 6 extends into the controllable shock wave cracker docking cavity 2 and is threadedly connected to the valve body 3.

[0052] It should be noted that both the oil pipe 7 and the controllable shock wave cracker 6 are hermetically connected to the valve body 3, so that the controllable shock wave cracker 6, the flushing valve 13 and the drain valve 10 can be started at a set water pressure, and at the same time, the water in the oil pipe 7 is prevented from draining into the wellbore.

[0053] When installing the pressure relief flushing valve 1, first install the pressure transmitter 5 into the pressure transmitter through hole, screw the end of the controllable shock wave cracker 6 into the controllable shock wave cracker docking cavity 2, and connect the data transmission end of the pressure transmitter 5 to the data receiving end of the controllable shock wave cracker 6. Then screw the end of the oil pipe 7 into the oil pipe docking cavity 4, and at the same time check the sealing performance of the joints at both ends of the pressure relief flushing valve 1; debug the pressure transmitter 5 to ensure that the pressure transmitter 5 can send a start signal to the controllable shock wave cracker 6 at a set pressure.

[0054] In this embodiment, both the drain hole 8 and the flushing hole 9 are inclined towards the direction of the controllable shock wave cracker docking cavity 2.

[0055] It should be noted that both the drainage hole 8 and the flushing hole 9 are inclined towards the docking cavity 2 of the controllable shock wave fracturing device, which can better dredge the channel for the movement of the controllable shock wave fracturing device 6 and facilitate the drainage of water in the oil pipe 7.

[0056] In this embodiment, a counterweight pipe is sleeved on the part of the oil pipe 7 located in the vertical section of the horizontal well.

[0057] It should be noted that the horizontal well includes a vertical section and a horizontal section. In the present invention, the cable used to control the controllable shock wave fracturing device 6 in the oil pipe 7 is omitted. Therefore, the diameter of the oil pipe 7 of the present invention is smaller than that of the oil pipe 7 in the prior art. During pushing, the self-weight of the oil pipe 7 and the weight of the counterweight pipe can be used to push the controllable shock wave fracturing device 6 in the horizontal well. Therefore, the pushing process of the method of the present invention is smoother, with less frictional resistance, avoiding the problem that a drilling machine needs to apply thrust to smoothly push the controllable shock wave fracturing device 6.

[0058] In this embodiment, the fracturing pump truck 22 is placed on the ground. The guiding cone 19 includes a cylindrical connecting pipe 23 and a guiding head 24 connected to the connecting pipe 23. The end of the guiding head 24 is conical, and the connecting pipe 23 is detachably connected to the controllable shock wave fracturing device 6.

[0059] It should be noted that as Figure 6 shown, the guiding head 24 is preferably made of metal material, and the diameter of the straight rod section of the guiding head 24 is larger than the diameter of the controllable shock wave fracturing device 6. Therefore, the controllable shock wave fracturing device 6 can smoothly pass through the steps of the coalbed methane horizontal wellbore with different pipe diameters under the guidance of the guiding cone 19.

[0060] In this embodiment, the cone angle at the end of the guiding head 24 is 30 degrees.

[0061] It should be noted that the guiding cone 19 with a cone angle of 30 degrees can smoothly push the controllable shock wave fracturing device 6, reducing the resistance at the end of the controllable shock wave fracturing device 6 during pushing.

[0062] As Figures 1 to 7 shown, a method for fracturing and plugging removal in a coalbed methane horizontal well includes the following steps:

[0063] Step 1: Pushing the controllable shock wave fracturing device: Push the controllable shock wave fracturing device 6 to the coal seam section to be fractured at the deepest part of the horizontal well;

[0064] It should be noted that by using the self-weight of the tubing 7 and the weight of the counterweight pipe, the controllable shock wave fracturing device 6 can be smoothly pushed to the deepest coal seam section to be fractured in the horizontal well. Under the guidance of the guiding cone 19, the controllable shock wave fracturing device 6 can smoothly pass through the steps of the coalbed methane horizontal wellbore with different pipe diameters.

[0065] Before pushing, debug the flushing valve: After rotating the flushing column 16, the position of the flushing column 16 in the second threaded hole section of the flushing hole 9 changes, so that the distance between the flushing column 16 and the spring 15 between the plungers 14 changes, thereby changing the pressure generated by the spring 15, and then the drainage threshold of the flushing valve 13 can be adjusted to the second water pressure threshold. When the pressure value during actual operation is greater than the second water pressure threshold, the flushing valve 13 opens.

[0066] Before pushing, set the drain valve: Screw out the stud 11 from the first threaded hole section, place the bursting disc 12 with a bursting pressure value of the third water pressure threshold at the bottom of the first threaded hole section, and then screw the stud 11 into the first threaded hole section. The bursting disc 12 is fixed by the stud 11. The bursting disc 12 is a disposable item. After the bursting disc 12 bursts, a new bursting disc 12 needs to be replaced when the drain valve 10 is used next time.

[0067] Step 2: Control the operation of the controllable shock wave fracturing device: Use the fracturing pump truck 22 to pump water pressure into the tubing 7, and collect the water pressure value in the water conduction hole 21 through the pressure transmitter 5. When the water pressure value collected by the pressure transmitter 5 reaches the first water pressure threshold, the controllable shock wave fracturing device 6 starts, and the controllable shock wave fracturing device 6 performs N times of shock wave operations on the deepest coal seam section to be fractured in the coal seam 20, and then the controllable shock wave fracturing device 6 automatically closes, where N is a positive integer and the value range of N is 2-10;

[0068] It should be noted that the specific value of N is determined by the physical properties of the horizontal well coal seam 20, and N is generally preferably 5 times; when the water pressure in the tubing 7 reaches the first water pressure threshold, the pressure transmitter 5 sends an electrical signal to the controllable shock wave fracturing device 6, and the controllable shock wave fracturing device 6 starts. The controllable shock wave fracturing device 6 generates 5 shock waves at equal intervals to act on the coal seam 20. After the shock wave operation is completed, the controllable shock wave fracturing device 6 automatically closes.

[0069] Step 3: Fracture the next coal seam section to be fractured: Move the controllable shock wave fracturing device 6 outward from the coal seam 20 in a layer-by-layer upward return manner, and perform shock wave operations on the next coal seam section to be fractured through the controllable shock wave fracturing device 6. The method of the controllable shock wave fracturing device 6 performing shock wave operations on the next coal seam section to be fractured is the same as the method of the controllable shock wave fracturing device 6 performing shock wave operations on the deepest coal seam section to be fractured in the coal seam 20 in Step 2;

[0070] It should be noted that after the shock wave operation in the previous section of the coal seam to be fractured is completed, the controllable shock wave fracturing device 6 is moved 20 meters away from the coal seam, so that the controllable shock wave fracturing device 6 is located in the adjacent section of the coal seam to be fractured, and the shock wave operation is carried out; then the shock wave operation is carried out on the remaining sections of the coal seam to be fractured in the same way of gradually returning layer by layer.

[0071] Step 4: Unblocking the wellbore: When the channel through which the controllable shock wave fracturing device 6 moves in the coalbed methane horizontal wellbore is blocked by coal powder, the fracturing pump truck 22 is used to pump water pressure into the tubing 7. When the water pressure value in the tubing 7 reaches the second water pressure threshold, the controllable shock wave fracturing device 6 is activated. At the same time, the water in the tubing 7 is ejected through the flushing valve 13. The shock wave generated by the controllable shock wave fracturing device 6 disperses the coal powder, and the high-pressure water ejected by the flushing valve 13 scatters the coal powder, thereby dredging the channel. After the channel is dredged, the water pressure is reduced so that the water pressure value is lower than the first water pressure threshold, and the water stops ejecting from the flushing valve 13, and the controllable shock wave fracturing device 6 automatically closes, where the second water pressure threshold is greater than the first water pressure threshold;

[0072] It should be noted that when the water pressure value in the tubing 7 reaches the second water pressure threshold, the plunger 14 of the flushing valve 13 moves and compresses the spring 15, and the water sprays out from the flushing hole 9 through the water guide groove 18 and the flushing through hole. The ejected water scatters the coal powder, thereby dredging the channel; after the channel is dredged, the water pressure is reduced, and the spring 15 resets, causing the plunger 14 to move to the initial position. After the plunger 14 moves in place, the water stops spraying out from the flushing hole 9.

[0073] When the consumables in the controllable shock wave fracturing device 6 are consumed and the wellbore is unblocked, the controllable shock wave fracturing device 6 will not generate shock waves. Therefore, only high-pressure water can be ejected through the flushing valve 13 for unblocking.

[0074] The shock wave generated by the controllable shock wave fracturing device 6 disperses the coal powder, and the high-pressure water ejected by the flushing valve 13 scatters the coal powder. The two unblocking methods are carried out simultaneously, resulting in higher unblocking efficiency and better effect.

[0075] Step 5: Repeat Step 3 to Step 4 until the shock wave operation for all sections of the coal seam to be fractured is completed;

[0076] Step 6: Draining the tubing: The fracturing pump truck 22 is used to pump water pressure into the tubing 7. When the water pressure value in the tubing 7 reaches the third water pressure threshold, the bursting disc 12 bursts, and the water in the tubing 7 passes through the bursting disc 12 and is discharged through the drain hole 8. At the same time, the water in the tubing 7 is ejected through the flushing valve 13. Then the fracturing pump truck 22 is closed. When the water pressure value in the tubing 7 is less than the second water pressure threshold, the flushing valve 13 automatically closes. When the water in the tubing 7 is emptied, the tubing 7 is removed, and then the pressure relief flushing valve 1, the controllable shock wave fracturing device 6 and the guide cone 19 are retracted, thereby completing the fracturing of the horizontal well coal seam, where the third water pressure threshold is greater than the second water pressure threshold.

[0077] It should be noted that when the water pressure value in the oil pipe 7 reaches the third water pressure threshold, the bursting disc 12 of the drain valve 10 bursts. At this time, the drain valve 10 is in an open state, and water passes through the bursting disc 12 and is discharged from the drain hole 8 through the drain through-hole.

[0078] When the water pressure value reaches the third water pressure threshold, the controllable shock wave fracturing device 6 is started simultaneously. At the same time, the water in the oil pipe 7 is ejected through the flushing valve 13. At this time, the consumables in the controllable shock wave fracturing device 6 have been consumed, so no shock wave will be generated.

[0079] During the process of discharging the water in the oil pipe 7, when the water pressure value of the water in the oil pipe 7 is less than the second water pressure threshold, the flushing valve 13 automatically closes, and then the water in the oil pipe 7 stops ejecting from the flushing valve 13.

[0080] After the drain valve 10 is opened, it is in an open state, so the water in the oil pipe 7 can be drained completely. When the water in the oil pipe 7 is emptied, the oil pipe 7 is taken out, and then the controllable shock wave fracturing device 6 is retrieved, thereby completing the fracturing of the horizontal well coal seam 20.

[0081] It should be noted that when the controllable shock wave fracturing device 6 completes the fracturing of the horizontal well, the water in the oil pipe 7 is discharged into the coalbed methane horizontal wellbore through the drain valve 10, so that when the oil pipe 7 is taken out, the oil pipe 7 no longer discharges sewage into the well site.

[0082] In this embodiment, the first water pressure threshold is 12 - 17 Mpa, the second water pressure threshold is 18 - 22 Mpa, and the third water pressure threshold is 23 - 27 Mpa.

[0083] It should be noted that the values of the first water pressure threshold, the second water pressure threshold, and the third water pressure threshold are determined by the vertical depth of the horizontal well. For a conventional horizontal well, that is, a horizontal well with a vertical depth of 1000 meters, the first water pressure threshold is preferably 15 Mpa, the second water pressure threshold is preferably 20 Mpa, and the third water pressure threshold is preferably 25 Mpa.

[0084] The above is only a preferred embodiment of the present invention, and does not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A fracturing and plugging removal system for coalbed methane horizontal wells, characterized in that: It includes a fracturing pump truck (22), a tubing (7), a pressure relief flushing valve (1), a controllable shock wave fracturing device (6), and a guide cone (19) connected in sequence; The pressure relief flushing valve (1) includes a valve body (3), a pressure transmitter (5), a flushing valve (13) for ejecting high-pressure water to unblock the coalbed methane horizontal wellbore, and a drain valve (10) for discharging residual water in the tubing (7), all of which are arranged in the valve body (3). The two ends of the valve body (3) are respectively provided with a tubing docking cavity (4) and a controllable shock wave fracturing device docking cavity (2). A water guiding hole (21) communicating with both the tubing docking cavity (4) and the controllable shock wave fracturing device docking cavity (2) is opened in the valve body (3). The pressure sensing end of the pressure transmitter (5) is inserted into the water guiding hole (21), and the data transmission end of the pressure transmitter (5) is connected to the data receiving end of the controllable shock wave fracturing device (6). Drain holes (8) and flushing holes (9) communicating with the water guiding hole (21) are opened on the side wall of the valve body (3). The drain valve (10) is located in the drain hole (8), and the flushing valve (13) is located in the flushing hole (9); The drain hole (8) includes a first threaded hole section (8-1) and a first through hole section (8-2). The drain valve (10) is installed in the first threaded hole section (8-1), and the aperture of the first threaded hole section (8-1) is larger than that of the first through hole section (8-2); The drain valve (10) includes a stud (11) and a bursting disc (12) abutted against the stud (11). The bursting disc (12) is located at one end of the first threaded hole section (8-1) close to the first through hole section (8-2). A drain through hole for draining water is provided along the axis of the stud (11); The flushing hole (9) includes a second threaded hole section (9-1) and a second through hole section (9-2). The aperture of the second threaded hole section (9-1) is larger than that of the second through hole section (9-2); The flushing valve (13) includes a plunger (14), a spring (15), and a flushing column (16) connected in sequence. One end of the plunger (14) is located in the second through hole section (9-2), and the other end of the plunger (14), the spring (15), and the flushing column (16) are all located in the second threaded hole section (9-1). A water guiding groove (18) is provided along the axial direction on the outer wall of the end of the plunger (14) located in the second through hole section (9-2). A flushing sealing ring (17) is provided at the end of the plunger (14) located in the second through hole section (9-2) and close to the spring (15). There is a gap between the other end of the plunger (14) and the inner wall of the second threaded hole section (9-1). A flushing through hole for discharging high-pressure water is provided along the axis of the flushing column (16); Both the drain hole (8) and the flushing hole (9) are inclined towards the direction of the controllable shock wave fracturing device docking cavity (2); The fracturing pump truck (22) is placed on the ground. The guide cone (19) includes a cylindrical connecting pipe (23) and a guide head (24) connected to the connecting pipe (23). The end of the guide head (24) is conical, and the connecting pipe (23) is detachably connected to the controllable shock wave fracturing device (6).

2. The fracturing and plugging removal system for coalbed methane horizontal wells according to claim 1, wherein: The oil pipe (7) extends into the oil pipe docking cavity (4) and is threadedly connected to the valve body (3), and the controllable shock wave fracturing device (6) extends into the controllable shock wave fracturing device docking cavity (2) and is threadedly connected to the valve body (3).

3. The fracturing and plugging removal system for coalbed methane horizontal wells according to claim 1, characterized in that: A counterweight pipe is sleeved on the part of the oil pipe (7) located in the vertical section of the horizontal well.

4. The fracturing and plugging removal system for coalbed methane horizontal wells according to claim 1, wherein: The cone angle at the end of the guide head (24) is 30 degrees.

5. A method for fracturing and plugging removal in horizontal wells for coalbed methane using the system as described in claim 1, characterized in that, This method includes the following steps: Step 1, pushing of the controllable shock wave fracturing device: Push the controllable shock wave fracturing device (6) to the coal seam section to be fractured at the deepest part of the horizontal well. Step 2, controlling the operation of the controllable shock wave fracturing device: Use a fracturing pump truck (22) to pump water pressure into the oil pipe (7), collect the water pressure value of the water in the water guide hole (21) through the pressure transmitter (5). When the water pressure value collected by the pressure transmitter (5) reaches the first water pressure threshold, the controllable shock wave fracturing device (6) starts, and the controllable shock wave fracturing device (6) performs N times of shock wave operations on the coal seam section to be fractured at the deepest part of the coal seam (20), and then the controllable shock wave fracturing device (6) automatically shuts down, where N is a positive integer and the value range of N is 2 to 10. Step 3, fracturing of the next coal seam section to be fractured: Move the controllable shock wave fracturing device (6) outwards from the coal seam (20) in a layer-by-layer upward return manner, and perform shock wave operations on the next coal seam section to be fractured through the controllable shock wave fracturing device (6). The way the controllable shock wave fracturing device (6) performs shock wave operations on the next coal seam section to be fractured is the same as the way the controllable shock wave fracturing device (6) performs shock wave operations on the coal seam section to be fractured at the deepest part of the coal seam (20) in Step 2. Step 4, unblocking of the wellbore: When the channel through which the controllable shock wave fracturing device (6) moves in the coalbed methane horizontal wellbore is blocked by coal powder, use a fracturing pump truck (22) to pump water pressure into the oil pipe (7). When the water pressure value in the oil pipe (7) reaches the second water pressure threshold, the controllable shock wave fracturing device (6) starts, and at the same time, the water in the oil pipe (7) sprays out through the flushing valve (13). The shock wave generated by the controllable shock wave fracturing device (6) disperses the coal powder, and the high-pressure water sprayed out by the flushing valve (13) flushes the coal powder away, thereby dredging the channel. After the channel is dredged, reduce the water pressure so that the water pressure value is lower than the first water pressure threshold, the water stops spraying out from the flushing valve (13), and the controllable shock wave fracturing device (6) automatically shuts down, where the second water pressure threshold is greater than the first water pressure threshold. Step 5, repeat Step 3 to Step 4 until all shock wave operations on the coal seam sections to be fractured are completed. Step Six, Drainage of the tubing: Use a fracturing pump truck (22) to pump water pressure into the tubing (7). When the water pressure value in the tubing (7) reaches the third water pressure threshold, the rupture disc (12) bursts, and the water in the tubing (7) passes through the rupture disc (12) and is discharged through the drain hole (8). At the same time, the water in the tubing (7) is ejected through the flushing valve (13). Then, turn off the fracturing pump truck (22). When the water pressure value in the tubing (7) is less than the second water pressure threshold, the flushing valve (13) automatically closes. After the water in the tubing (7) is emptied, lift out the tubing (7), and then retract the pressure relief flushing valve (1), the controllable shock wave fracturing device (6), and the guide cone (19), thereby completing the fracturing of the coal seam in the horizontal well. Among them, the third water pressure threshold is greater than the second water pressure threshold.

6. The method according to claim 5, characterized in that: The first water pressure threshold is 12 - 17 Mpa, the second water pressure threshold is 18 - 22 Mpa, and the third water pressure threshold is 23 - 27 Mpa.

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