Combustion improver continuous feeding method for methane in-situ burning explosion fracturing

Abstract

A combustion improver continuous feeding method for methane in-situ burning explosion fracturing comprises the steps that a fracturing well section is determined, a well is drilled, and a drillable bridge plug is put in; assembling and installing a putting tool; the putting tool is put down, and the oil pipe through pipe and the shaft through pipe are connected in a sealed mode; high-pressure nitrogen is injected through nitrogen injection equipment, and the packer is set; a combustion improver is injected into the gas storage space of the throwing tool main body through the high-pressure hose by using oxygen injection equipment, and oxygen is injected into the sealed target section at a certain initial pressure; nitrogen with increased pressure is used for pushing a piston in the feeding tool main body downwards, so that the residual combustion improver in the gas storage space is discharged; the packing of the combustion improver is completed; finally, plugging the tool and performing compression ignition; according to the method, the continuous throwing of the methane in-situ burning explosion fracturing combustion improver and the packing technology of the combustion improver are combined, the packing problem of the combustion improver during the continuous throwing process of the combustion improver can be effectively solved, and the safety of the continuous conveying of the combustion improver along the way can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal and unconventional natural gas development, and in particular relates to a method for continuously placing a combustion aid for methane in-situ explosion fracturing. Background Art

[0002] my country has abundant coalbed methane resources. However, due to the complexity of the occurrence conditions, the high difficulty of exploration and development technology, and the lack of versatility of coalbed methane development technology under different geological conditions, the single well production is generally low, which makes my country's dependence on foreign natural gas still high. As an important means to increase my country's coalbed methane production, hydraulic fracturing technology has achieved initial results in increasing the production of coalbed methane dominated by high-rank coal, but overall, its effect has not yet met expectations. This dilemma is mainly attributed to two aspects: first, the diversity and complexity of my country's coalbed methane resources make it difficult for a single technology to achieve unified and efficient transformation of different coal seams; second, the problems of reservoir damage, environmental pollution and water resource consumption caused by water-based fracturing fluids are becoming increasingly severe. Therefore, it is urgent to upgrade and optimize the existing process technology according to the geological characteristics of coal seams, the existing process technology status and the demand for production increase and transformation, and accelerate the development and application of waterless or low-water fracturing fluid systems, so as to be committed to the innovative development of low-cost, high-efficiency, green and low-carbon special technologies that are "adapted to local conditions".

[0003] In recent years, some scholars have proposed an innovative "local material" reservoir fracturing method, which uses methane in the reservoir as fuel, artificially releases combustion aids, and forms a methane-combustion aid mixed gas at the bottom of the well or in the reservoir, and then detonates the mixed gas to generate instantaneous explosion high pressure, thereby fracturing the reservoir and forming impact cracks, and finally constructing a complex three-dimensional fracture network to achieve increased production and permeability of unconventional natural gas reservoirs. Methane in-situ explosion fracturing technology relies on the high pressure conditions generated by methane explosion to perform fracturing. Compared with hydraulic fracturing, it can generate greater fracturing pressure and effectively avoid common groundwater pollution and fresh water loss in hydraulic fracturing. In this technology, the precise delivery of combustion aids is the key. Conventional methods of delivering combustion aids include continuous delivery and sealed pre-charging delivery. Sealed pre-charging delivery can achieve quantitative and uniform delivery of combustion aids in a small space deep underground, and has significant advantages in precise delivery. However, this closed delivery method also has some defects, that is, it can only achieve a single delivery operation and cannot meet the operational requirements of continuous fracturing. In actual working conditions, the annulus volume is about twice the volume of the tool, and the optimal volume ratio of methane to combustion aid is 1:2, which makes it difficult to match the tool volume with the annulus volume. When the fracturing section is long or the bottom hole pressure is high, the combustion aid pre-stored in the container may not meet the requirements of bottom hole explosion. Therefore, on the one hand, it is necessary to continue to develop a closed pre-charged delivery method; on the other hand, when faced with complex situations, it is also necessary to consider the along-the-way transportation method. By reducing the size of the delivery pipe, the volume of the combustion aid along the way can be effectively reduced, thereby improving the effective delivery operation, and at the same time, it can also ensure the safety during the delivery operation. Summary of the invention

[0004] In view of some problems existing in the prior art, the present invention provides a method for continuous delivery of combustion aid for methane in-situ explosion fracturing. The method can combine the continuous delivery of combustion aid for methane in-situ explosion fracturing with the combustion aid isolation technology, and can effectively solve the isolation problem of the combustion aid transported along the process during the continuous delivery of the combustion aid, and can significantly improve the safety of the continuous transportation of the combustion aid along the process.

[0005] In order to achieve the above object, the present invention provides a method for continuously adding a combustion aid for methane in-situ explosion fracturing, comprising the following steps:

[0006] Step 1: Determine the well section for fracturing, drill the well and run a drillable bridge plug;

[0007] S11: Conduct ground geological surveys to detect the distribution of underground coal seams and determine the thickness and distribution range of coal seams;

[0008] S12: Comprehensively evaluate the coal seams by integrating geological exploration results, well logging data, gas content and pressure test data;

[0009] S13: Based on the selected drilling layer, the geological model is used to plan the drilling path to ensure that the drilling trajectory can pass through the target coal seam;

[0010] S14: Use coalbed methane drilling equipment and process technology to drill a wellbore vertically from the ground downwards, and determine the fracturing well section based on the geological exploration data of the reservoir and the comprehensive analysis of the characteristics of the coal seam; complete the drilling operation of all construction well groups in this way;

[0011] S15: running a drillable bridge plug below the target position in each wellbore and setting the bridge plug;

[0012] Step 2: Assemble and install the delivery tool;

[0013] S21: Install a wellbore through pipe at the upper end of the wellbore, and connect a ball valve 1 in series to the gas outlet pipe of the wellbore through pipe;

[0014] S22: Prepare safety joints, straighteners, tubing anchors, packers, a launching tool body and three sections of tubing, and assemble the downhole tool; wherein the launching tool body includes a bearing cylinder, a piston, an ignition electrode and an ignition device; a gas storage cavity is formed inside the bearing cylinder, a guide through hole is provided in the central area of ​​the top plate of the bearing cylinder, a plurality of air outlets are provided on the bottom plate of the bearing cylinder, and a constant pressure valve is installed in the air outlet; the constant pressure valve can only be opened in a directional direction toward the bottom of the well; the piston is assembled inside the bearing cylinder in a sliding and sealing manner, and an air injection hole is provided in the central area thereof; the ignition electrode is installed on the outer side of the bottom plate of the bearing cylinder; the ignition device is installed in the central area of ​​the upper end surface of the bottom plate of the bearing cylinder; the upper end of the straightener is connected to the lower end of the upper section of tubing through a safety joint, the upper end of the tubing anchor is connected to the lower end of the straightener through a pipeline, the upper end of the packer is connected to the lower end of the tubing anchor through a middle section of tubing, and the upper end of the bearing cylinder in the launching tool body is connected to the lower end of the packer through a lower section of tubing;

[0015] S23: prepare the oil pipe through-tube and the high-pressure hose; install the oil pipe through-tube on the upper end of the upper oil pipe, and connect the second ball valve in series on the air inlet line of the oil pipe through-tube; make the air outlet end of the high-pressure hose pass through the oil pipe through-tube and penetrate into the inside of the oil pipe, and after extending into the main body of the delivery tool through the guide through-hole, fix it in the air injection hole on the piston, and at the same time, ensure that the air inlet end of the high-pressure hose is located outside the upper end of the oil pipe through-tube, and complete the assembly operation of the delivery tool;

[0016] Step 3: lowering the delivery tool;

[0017] The part of the delivery tool below the oil pipe through the wellbore through the wellbore through the wellbore, and after the delivery tool body is lowered to the predetermined target position, the lower end of the oil pipe through the wellbore ...

[0018] Step 4: Inject high-pressure nitrogen to set the packer;

[0019] Connect the air inlet of the tubing through-pipe with the output pipeline of the nitrogen injection equipment on the ground, open the second ball valve, slowly inject high-pressure nitrogen into the tubing using the nitrogen injection equipment, and adjust the nitrogen injection flow rate so that the high-pressure nitrogen enters the packer through the safety joint, the centralizer and the tubing anchor to set the packer, and use the set packer and the set bridge plug to form a closed space in the target section;

[0020] Step 5: Adding combustion aid;

[0021] S51: Slow down the nitrogen injection flow rate so that the nitrogen in the annulus between the tubing and the high-pressure hose can meet the setting requirements of the packer;

[0022] S52: connecting the air inlet end of the high-pressure hose to the output pipeline of the oxygen injection device on the ground, injecting oxygen into the high-pressure hose by using the oxygen injection device, so that the oxygen enters the gas storage cavity through the high-pressure hose and the piston, and after the pressure in the gas storage cavity increases and reaches the opening pressure of the constant pressure valve, multiple constant pressure valves are opened at the same time, and oxygen is injected into the closed target section at an initial pressure not less than the opening pressure of the constant pressure valve;

[0023] Step 6: Emission of residual combustion aid;

[0024] S61: After the set amount of combustion-supporting agent is added, the oxygen injection device is stopped, and the oxygen injection operation is stopped. When the oxygen pressure in the gas storage space is less than the opening pressure of the constant pressure valve, the multiple constant pressure valves are restored to the closed state;

[0025] S62: increasing the opening of the second ball valve and the rate of nitrogen injection, so that the high-pressure nitrogen pushes the piston in the delivery tool body downward, and the downward piston is used to pressurize the residual oxygen in the gas storage space, and the multiple constant pressure valves are prompted to reopen. At the same time, the residual oxygen in the gas storage space is injected into the target section through the multiple constant pressure valves, so as to realize the discharge operation of the residual combustion-supporting agent, and the multiple constant pressure valves are restored to the closed state;

[0026] Step 7: Seal and compress to ignite;

[0027] The nitrogen filled in the annular space between the oil pipe and the high-pressure hose is used to keep the piston pressed against the bottom plate of the bearing cylinder, and the self-reset ability of the constant pressure valve is assisted to jointly ensure the blocking state of the main body of the delivery tool, so as to prevent the oxygen in the wellbore from flowing back into the main body of the delivery tool;

[0028] At the same time, the piston pressed on the bottom plate of the bearing cylinder is used to press and trigger the ignition device. After the ignition device is triggered, the ignition electrode is controlled to perform an ignition action to realize the ignition operation of the combustion aid.

[0029] Furthermore, in order to more effectively reduce the amount of oxygen stored along the process and further improve the safety of the combustion aid transportation process, in step six S61, after the oxygen injection equipment stops working, the air inlet end of the high-pressure hose can be connected to the nitrogen injection equipment, and the nitrogen injection equipment can be used to inject a set amount of nitrogen into the high-pressure hose, and the injected nitrogen can be used to reduce the volume of oxygen in the high-pressure hose.

[0030] Furthermore, in order to more accurately and efficiently detect the distribution of coal seams, in step one S11, ground geological surveys are conducted using geological radar or seismic exploration techniques; in order to accurately determine the location of the fracturing well section, in step one S14, the characteristics of the coal seam include the thickness, inclination and permeability of the coal seam.

[0031] Furthermore, in order to facilitate installation and disassembly operations, in step 2 S22, the lower section of the oil pipe is connected to the main body of the delivery tool by means of threaded engagement.

[0032] Furthermore, in order to ensure the sealing effect, in step 2 S23, after the lowering and installation operation of the delivery tool is completed, the sealing between the oil pipe through pipe and the wellbore through pipe is checked again.

[0033] As a preferred embodiment, in step 2 S22, the air injection holes on the piston and the air outlet holes on the bottom plate of the bearing cylinder are in a staggered distribution state.

[0034] As a preference, in step 2 S22, the ignition device has a built-in power supply.

[0035] In the present invention, a straightener is provided in the delivery tool, which can facilitate the adjustment of the direction and posture of the oil pipe during the lowering process of the oil pipe, thereby ensuring the smooth lowering of the delivery tool. A tubing anchor is provided in the delivery tool, which can facilitate the anchoring of the delivery tool at a set position. A packer connected to the oil pipe is provided in the delivery tool, which can achieve rapid sealing by means of high-pressure gas injection, and then can cooperate with the bridge plug that is first lowered to form a sealed space in the target section, thereby ensuring the subsequent fracturing efficiency and effect. A piston is installed in the bearing cylinder, which can facilitate the formation of a gas storage space between the piston and the bearing cylinder. By providing an injection hole on the piston, it is convenient to connect a high-pressure hose using the injection hole, and then the high-pressure hose can be used to inject a combustion-supporting agent into the gas storage space. A plurality of constant pressure valves are installed on the bottom plate of the bearing cylinder of the delivery tool body. Since the constant pressure valve has a certain opening pressure, it can ensure that the combustion-supporting agent sprayed out of the gas storage space has a certain initial pressure, which is conducive to improving the fracturing effect and efficiency. By installing an ignition device on the bottom plate of the bearing cylinder, the ignition device can be pressed and triggered by the close contact between the piston and the bottom plate, and then the ignition electrode can be ignited after the ignition device is triggered, which is conducive to the subsequent convenient ignition operation. A wellbore through pipe is installed at the upper end of the wellbore, and then the assembled delivery tool is lowered into the wellbore in the oil pipe through pipe, which can facilitate the formation of an annular cavity space between the delivery tool and the wellbore, which is conducive to the subsequent natural gas extraction operation. By connecting a ball valve in series on the gas outlet pipeline of the wellbore through pipe, the closed state and open state of the annular cavity space can be switched. An oil pipe passage and a delivery tool body are respectively arranged at the upper and lower ends of the delivery tool, and then a high-pressure hose with an outer diameter smaller than the inner diameter of the oil pipe is passed through the oil pipe passage, and the lower end of the high-pressure hose is connected to the air injection hole on the piston in the delivery tool body, so that an annular space can be formed between the high-pressure hose and the oil pipe, which is conducive to using the annular space to fill the annular space with nitrogen; by installing a ball valve 2 on the air inlet pipeline of the oil pipe passage, it is convenient to change the connection or shutoff state of the annular space with the outside world. Since the inner diameter of the high-pressure hose as the combustion aid delivery channel is smaller than the inner diameter of the oil pipe, and at the same time, when the packer is maintained in the sealing state, the annular space between the oil pipe and the high-pressure hose is filled with nitrogen, therefore, during the delivery of the combustion aid, it is convenient to reduce the volume of the combustion aid delivered along the way by reducing the size of the delivery pipe, and to seal the combustion aid by injecting nitrogen into the annular space, thereby effectively improving the safety of the continuous delivery of the combustion aid along the way. In addition, since the directional valve will only open when the pressure in the gas storage space reaches the opening pressure, the combustion-aiding agent sprayed out through the main body of the delivery tool must have a certain initial pressure, thereby effectively improving the fracturing effect and efficiency.After the oxygen injection equipment stops working, the pressure in the gas storage space will decrease, and the constant pressure valve will automatically close after the pressure in the gas storage space drops to the set pressure. In this way, a part of the combustion aid will inevitably remain in the gas storage space. In order to improve the utilization rate of the combustion aid, the residual combustion aid needs to be discharged. By increasing the nitrogen injection pressure to push the piston downward, the pressure in the gas storage space can be effectively increased, and then the secondary opening of the constant pressure valve can be achieved. In this way, the combustion aid remaining in the gas storage space can be completely discharged into the target section during the downward movement of the piston, effectively ensuring the utilization rate of the combustion aid. At the same time, this is conducive to further reducing the storage amount of the combustion aid along the process, thereby further improving the safety of the continuous delivery of the combustion aid in the methane in-situ explosion fracturing, and realizing the isolation and continuous safe delivery of the combustion aid in the methane in-situ explosion fracturing.

[0036] The present invention proposes an innovative method for the continuous and safe delivery of a sealable combustion aid, which combines the continuous delivery of a methane in-situ explosion and fracturing combustion aid with the combustion aid sealing technology, effectively solving the problem of sealing the combustion aid along the transportation process during the continuous delivery of the combustion aid, and improving the safety of the continuous transportation of the combustion aid along the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the state of assembling the bridge plug and the wellbore through pipe in the wellbore of the present invention;

[0038] Figure 2 It is a partial structural schematic diagram of the delivery tool in the present invention;

[0039] Figure 3 It is a schematic diagram of the assembly of the delivery tool in the wellbore of the present invention;

[0040] Figure 4 This is a schematic diagram of the state of continuous delivery of the combustion aid according to the present invention;

[0041] Figure 5 It is a structural schematic diagram of the main body of the delivery tool in the present invention.

[0042] In the figure: 1. ball valve 1, 2. wellbore through pipe, 3. wellbore, 4. bridge plug, 5. reservoir, 6. oil pipe, 7. safety joint, 8. centralizer, 9. oil pipe anchor, 10. packer, 11. launching tool body, 12. high-pressure hose, 13. oil pipe through pipe, 14. piston, 15. nitrogen, 16. oxygen, 17. constant pressure valve, 18. ball valve 2, 19. ignition device, 20. ignition electrode, 21. bearing cylinder. DETAILED DESCRIPTION

[0043] The present invention will be further described below.

[0044] like Figures 1 to 5As shown, the present invention provides a method for continuously placing a combustion aid for methane in-situ explosion fracturing, comprising the following steps:

[0045] Step 1: Determine the well section for fracturing, drill the well and run a drillable bridge plug;

[0046] S11: Conduct ground geological surveys to detect the distribution of underground coal seams and determine the thickness and distribution range of coal seams;

[0047] S12: Comprehensively evaluate the coal seams by integrating geological exploration results, well logging data, gas content and pressure test data;

[0048] S13: Based on the selected drilling layer, the geological model is used to plan the drilling path to ensure that the drilling trajectory can pass through the target coal seam;

[0049] S14: using coalbed methane drilling equipment and process technology, vertically drilling a wellbore 3 from the ground downward, and comprehensively analyzing the characteristics of the coal seam according to the geological exploration data of the reservoir 5 to determine the fracturing well section; in this way, completing the drilling operation of all the construction well groups;

[0050] S15: Figure 1 As shown, a drillable bridge plug 4 is lowered into each wellbore 3 below the target position, and the bridge plug 4 is set in a sealed state;

[0051] Step 2: Assemble and install the delivery tool;

[0052] S21: Install the wellbore through pipe 2 at the upper end of the wellbore 3, and connect the ball valve 1 in series to the gas outlet pipeline of the wellbore through pipe 2;

[0053] S22: Figure 2 As shown, a safety joint 7, a centralizer 8, an oil pipe anchor 9, a packer 10, a delivery tool body 11 and three sections of oil pipe 6 are prepared, and the downhole tool is assembled; wherein, the delivery tool body 11 includes a bearing cylinder 21, a piston 14, an ignition electrode 20 and an ignition device 19; a gas storage cavity is formed inside the bearing cylinder 21, a guide through hole is opened in the central area of ​​the top plate of the bearing cylinder 21, a plurality of air outlet holes are opened on the bottom plate of the bearing cylinder 21, and a constant pressure valve 17 is installed in the air outlet hole; the constant pressure valve 17 can only be opened in a directional direction toward the bottom of the well; the piston 14 slides The dynamic seal is assembled in the interior of the bearing cylinder 21, and a gas injection hole is opened in the central area thereof; the ignition electrode 20 is installed on the outer side of the bottom plate of the bearing cylinder 21; the ignition device 19 is installed in the central area of ​​the upper end surface of the bottom plate of the bearing cylinder 21; the upper end of the centralizer 8 is connected to the lower end of the upper section oil pipe 6 through the safety joint 7, the upper end of the oil pipe anchor 9 is connected to the lower end of the centralizer 8 through the pipeline, the upper end of the packer 10 is connected to the lower end of the oil pipe anchor 9 through the middle section oil pipe 6, and the upper end of the bearing cylinder in the delivery tool body 11 is connected to the lower end of the packer 10 through the lower section oil pipe 6;

[0054] S23: prepare the oil pipe through-tube 13 and the high-pressure hose 12; install the oil pipe through-tube 13 on the upper end of the upper oil pipe 6, and connect the ball valve 18 in series on the air inlet line of the oil pipe through-tube 13; make the air outlet end of the high-pressure hose 12 pass through the oil pipe through-tube 13 and penetrate into the inside of the oil pipe 6, and after extending into the main body 11 of the delivery tool through the guide through hole, fix it in the air injection hole on the piston 14, and at the same time, ensure that the air inlet end of the high-pressure hose 12 is located outside the upper end of the oil pipe through-tube 13, and complete the assembly operation of the delivery tool;

[0055] The guide through hole at the upper end of the delivery tool body 11 is sealedly connected to the high-pressure hose 12;

[0056] The air inlet end of the high-pressure hose 12 is located outside the upper end of the oil pipe 13, which can be easily connected to the oxygen injection equipment on the ground, and of course, it can also be easily connected to the pressure detection equipment or other detection sensing equipment;

[0057] Step 3: lowering the delivery tool;

[0058] The portion of the delivery tool below the oil pipe through-tube 13 is passed through the wellbore through-tube 2 and lowered into the wellbore 3. After the delivery tool body 11 is lowered to the predetermined target position, the lower end of the oil pipe through-tube 13 is sealed and connected with the upper end of the wellbore through-tube 2.

[0059] Step 4: injecting high-pressure nitrogen to set the packer 10;

[0060] like Figure 3 As shown, the air inlet pipeline of the oil pipe 13 is connected to the output pipeline of the nitrogen injection equipment on the ground, the ball valve 18 is opened, and the high-pressure nitrogen 15 is slowly injected into the oil pipe 6 by the nitrogen injection equipment, and the injection flow rate of the nitrogen 15 is adjusted, so that the high-pressure nitrogen 15 enters the packer 10 through the safety joint 7, the centralizer 8 and the oil pipe anchor 9, so that the packer 10 is set, and the set packer 10 and the set bridge plug 4 are used to form a closed space in the target section;

[0061] Step 5: Adding combustion aid;

[0062] S51: slowing down the injection flow of the nitrogen 15 so that the nitrogen 15 in the annulus between the oil pipe 6 and the high-pressure hose 12 can meet the setting requirement of the packer 10;

[0063] S52: Figure 4As shown, the air inlet end of the high-pressure hose 12 is connected to the output pipeline of the oxygen injection device on the ground, and the oxygen injection device is used to inject oxygen 16 into the high-pressure hose 12, so that the oxygen 16 enters the gas storage cavity through the high-pressure hose 12 and the piston 14. After the pressure in the gas storage cavity increases and reaches the opening pressure of the constant pressure valve 17, multiple constant pressure valves 17 are opened at the same time, and the oxygen 16 is injected into the closed target section at an initial pressure not less than the opening pressure of the constant pressure valve 17;

[0064] Step 6: Emission of residual combustion aid;

[0065] S61: After the set amount of combustion-supporting agent is added, the oxygen injection device is stopped, and the injection operation of oxygen 16 is stopped. When the pressure of oxygen 16 in the gas storage space is less than the opening pressure of the constant pressure valve 17, the multiple constant pressure valves 17 are restored to the closed state;

[0066] S62: increasing the opening of the second ball valve 18, increasing the injection rate of the nitrogen 15, so that the high-pressure nitrogen 15 pushes the piston 14 in the delivery tool body 11 to move downward, and the downward piston 14 is used to pressurize the residual oxygen 16 in the gas storage space, and the multiple constant pressure valves 17 are reopened. At the same time, the residual oxygen 16 in the gas storage space is injected into the target section through the multiple constant pressure valves 17, so as to realize the discharge operation of the residual combustion agent, and the multiple constant pressure valves 17 are restored to the closed state;

[0067] Step 7: Seal and compress to ignite;

[0068] like Figure 5 As shown, the nitrogen 15 filled in the annular space between the oil pipe 6 and the high-pressure hose 12 is used to keep the piston 14 pressed against the bottom plate of the bearing cylinder 21, and the self-reset ability of the constant pressure valve 17 is assisted to jointly ensure the blocking state of the delivery tool body 11, so as to prevent the oxygen 16 in the wellbore 3 from flowing back into the delivery tool body 11;

[0069] At the same time, the piston 14 pressed against the bottom plate of the bearing cylinder 21 is used to press and trigger the ignition device 19. After the ignition device 19 is triggered, the ignition electrode 20 is controlled to perform an ignition action to achieve the ignition operation of the combustion aid.

[0070] In order to more accurately and efficiently detect the distribution of coal seams, in step 1 S11, ground geological surveys are conducted using geological radar or seismic exploration techniques; in order to accurately determine the location of the fracturing well section, in step 1 S14, the characteristics of the coal seam include the thickness, inclination and permeability of the coal seam.

[0071] In order to facilitate the installation and disassembly operations, in step 2 S22 , the lower section of the oil pipe 6 is connected to the delivery tool body 11 by means of threaded engagement.

[0072] In order to ensure the sealing effect, in step 2 S23, after the lowering and installation operation of the delivery tool is completed, the sealing between the oil pipe 13 and the wellbore pipe 2 is checked again.

[0073] As a preferred embodiment, in step 2 S22, the air injection holes on the piston 14 and the air outlet holes on the bottom plate of the supporting cylinder 21 are in a staggered distribution state.

[0074] As a preference, in step 2 S22, the ignition device 9 has a built-in power supply.

[0075] In order to more effectively reduce the amount of oxygen stored along the process and further improve the safety of the combustion aid transportation process, in step six S61, after the oxygen injection equipment stops working, the air inlet end of the high-pressure hose 12 can be connected to the nitrogen injection equipment, and the nitrogen injection equipment can be used to inject a set amount of nitrogen 15 into the high-pressure hose 12, and the injected nitrogen 15 can be used to reduce the volume of oxygen 16 in the high-pressure hose 12.

[0076] In the present invention, a straightener is provided in the delivery tool, which can facilitate the adjustment of the direction and posture of the oil pipe during the lowering process of the oil pipe, thereby ensuring the smooth lowering of the delivery tool. A tubing anchor is provided in the delivery tool, which can facilitate the anchoring of the delivery tool at a set position. A packer connected to the oil pipe is provided in the delivery tool, which can achieve rapid sealing by means of high-pressure gas injection, and then can cooperate with the bridge plug that is first lowered to form a sealed space in the target section, thereby ensuring the subsequent fracturing efficiency and effect. A piston is installed in the bearing cylinder, which can facilitate the formation of a gas storage space between the piston and the bearing cylinder. By providing an injection hole on the piston, it is convenient to connect a high-pressure hose using the injection hole, and then the high-pressure hose can be used to inject a combustion-supporting agent into the gas storage space. A plurality of constant pressure valves are installed on the bottom plate of the bearing cylinder of the delivery tool body. Since the constant pressure valve has a certain opening pressure, it can ensure that the combustion-supporting agent sprayed out of the gas storage space has a certain initial pressure, which is conducive to improving the fracturing effect and efficiency. By installing an ignition device on the bottom plate of the bearing cylinder, the ignition device can be pressed and triggered by the close contact between the piston and the bottom plate, and then the ignition electrode can be ignited after the ignition device is triggered, which is conducive to the subsequent convenient ignition operation. A wellbore through pipe is installed at the upper end of the wellbore, and then the assembled delivery tool is lowered into the wellbore in the oil pipe through pipe, which can facilitate the formation of an annular cavity space between the delivery tool and the wellbore, which is conducive to the subsequent natural gas extraction operation. By connecting a ball valve in series on the gas outlet pipeline of the wellbore through pipe, the closed state and open state of the annular cavity space can be switched. An oil pipe passage and a delivery tool body are respectively arranged at the upper and lower ends of the delivery tool, and then a high-pressure hose with an outer diameter smaller than the inner diameter of the oil pipe is passed through the oil pipe passage, and the lower end of the high-pressure hose is connected to the air injection hole on the piston in the delivery tool body, so that an annular space can be formed between the high-pressure hose and the oil pipe, which is conducive to using the annular space to fill the annular space with nitrogen; by installing a ball valve 2 on the air inlet pipeline of the oil pipe passage, it is convenient to change the connection or shutoff state of the annular space with the outside world. Since the inner diameter of the high-pressure hose as the combustion aid delivery channel is smaller than the inner diameter of the oil pipe, and at the same time, when the packer is maintained in the sealing state, the annular space between the oil pipe and the high-pressure hose is filled with nitrogen, therefore, during the delivery of the combustion aid, it is convenient to reduce the volume of the combustion aid delivered along the way by reducing the size of the delivery pipe, and to seal the combustion aid by injecting nitrogen into the annular space, thereby effectively improving the safety of the continuous delivery of the combustion aid along the way. In addition, since the directional valve will only open when the pressure in the gas storage space reaches the opening pressure, the combustion-aiding agent sprayed out through the main body of the delivery tool must have a certain initial pressure, thereby effectively improving the fracturing effect and efficiency.After the oxygen injection equipment stops working, the pressure in the gas storage space will decrease, and the constant pressure valve will automatically close after the pressure in the gas storage space drops to the set pressure. In this way, a part of the combustion aid will inevitably remain in the gas storage space. In order to improve the utilization rate of the combustion aid, the residual combustion aid needs to be discharged. By increasing the nitrogen injection pressure to push the piston downward, the pressure in the gas storage space can be effectively increased, and then the secondary opening of the constant pressure valve can be achieved. In this way, the combustion aid remaining in the gas storage space can be completely discharged into the target section during the downward movement of the piston, effectively ensuring the utilization rate of the combustion aid. At the same time, this is conducive to further reducing the storage amount of the combustion aid along the process, thereby further improving the safety of the continuous delivery of the combustion aid in the methane in-situ explosion fracturing, and realizing the isolation and continuous safe delivery of the combustion aid in the methane in-situ explosion fracturing.

[0077] The present invention proposes an innovative method for the continuous and safe delivery of a sealable combustion aid, which combines the continuous delivery of a methane in-situ explosion and fracturing combustion aid with the combustion aid sealing technology, effectively solving the problem of sealing the combustion aid along the transportation process during the continuous delivery of the combustion aid, and improving the safety of the continuous transportation of the combustion aid along the process.

Claims

1. A method for continuous delivery of combustion aid for methane in-situ explosion fracturing, characterized in that: The following steps are involved: Step 1: Determine the well section for fracturing, drill the well and run a drillable bridge plug; S11: Conduct ground geological surveys to detect the distribution of underground coal seams and determine the thickness and distribution range of coal seams; S12: Comprehensively evaluate the coal seams by integrating geological exploration results, well logging data, gas content and pressure test data; S13: Based on the selected drilling layer, the geological model is used to plan the drilling path to ensure that the drilling trajectory can pass through the target coal seam; S14: using coalbed methane drilling equipment and process technology, vertically drilling a wellbore (3) from the ground downward, and comprehensively analyzing the characteristics of the coal seam based on the geological exploration data of the reservoir (5) to determine the fracturing well section; in this way, completing the drilling operation of all the construction well groups; S15: inserting a drillable bridge plug (4) below the target position in each wellbore (3), and setting the bridge plug (4) to a sealing state; Step 2: Assemble and install the delivery tool; S21: Installing a wellbore through pipe (2) at the upper end of the wellbore (3), and connecting a ball valve (1) in series to the gas outlet pipeline of the wellbore through pipe (2); S22: Prepare the safety joint (7), the stabilizer (8), the tubing anchor (9), the packer (10), the delivery tool body (11) and the three sections of tubing (6), and assemble the downhole tool; wherein the delivery tool body (11) includes a bearing cylinder (21), a piston (14), an ignition electrode (20) and an ignition device (19); a gas storage cavity is formed inside the bearing cylinder (21); a guide through hole is opened in the central area of ​​the top plate of the bearing cylinder (21); a plurality of air outlet holes are opened on the bottom plate of the bearing cylinder (21), and a constant pressure valve (17) is installed in the air outlet hole; the constant pressure valve (17) can only be opened in a directional direction toward the bottom of the well; the piston (14 ) is assembled inside the bearing cylinder (21) in a sliding and sealing manner, and a gas injection hole is opened in the central area thereof; the ignition electrode (20) is installed on the outer side of the bottom plate of the bearing cylinder (21); the ignition device (19) is installed in the central area of ​​the upper end surface of the bottom plate of the bearing cylinder (21); the upper end of the centralizer (8) is connected to the lower end of the upper section oil pipe (6) through a safety joint (7), the upper end of the oil pipe anchor (9) is connected to the lower end of the centralizer (8) through a pipeline, the upper end of the packer (10) is connected to the lower end of the oil pipe anchor (9) through the middle section oil pipe (6), and the upper end of the bearing cylinder in the launching tool body (11) is connected to the lower end of the packer (10) through the lower section oil pipe (6); S23: prepare an oil pipe passage (13) and a high-pressure hose (12); install the oil pipe passage (13) on the upper end of the upper oil pipe (6), and connect a second ball valve (18) in series to the air inlet line of the oil pipe passage (13); allow the air outlet end of the high-pressure hose (12) to pass through the oil pipe passage (13) and penetrate into the interior of the oil pipe (6), and after extending into the main body (11) of the delivery tool through the guide hole, fix it in the air injection hole on the piston (14), and at the same time, ensure that the air inlet end of the high-pressure hose (12) is located outside the upper end of the oil pipe passage (13), thereby completing the assembly operation of the delivery tool; Step 3: lowering the delivery tool; The portion of the delivery tool below the oil pipe through-tube (13) is passed through the wellbore through-tube (2) and lowered into the wellbore (3); after the delivery tool body (11) is lowered to a predetermined target position, the lower end of the oil pipe through-tube (13) is sealed and connected to the upper end of the wellbore through-tube (2); Step 4: injecting high pressure nitrogen (15) to set the packer (10); Connecting the air inlet of the oil pipe passage (13) to the output pipeline of the nitrogen injection device on the ground, opening the second ball valve (18), slowly injecting high-pressure nitrogen (15) into the oil pipe (6) by using the nitrogen injection device, and adjusting the injection flow rate of the nitrogen (15) so that the high-pressure nitrogen (15) enters the packer (10) through the safety joint (7), the centralizer (8) and the oil pipe anchor (9), so that the packer (10) is set, and forming a closed space in the target section by using the set packer (10) and the set bridge plug (4); Step 5: Adding combustion aid; S51: slowing down the injection flow rate of the nitrogen (15) so that the nitrogen (15) in the annulus between the oil pipe (6) and the high-pressure hose (12) can meet the setting requirement of the packer (10); S52: connecting the air inlet end of the high-pressure hose (12) to the output pipeline of the oxygen injection device on the ground, injecting oxygen (16) into the high-pressure hose (12) by using the oxygen injection device, so that the oxygen (16) enters the gas storage chamber through the high-pressure hose (12) and the piston (14), and after the pressure in the gas storage chamber increases and reaches the opening pressure of the constant pressure valve (17), the multiple constant pressure valves (17) are opened at the same time, and the oxygen (16) is injected into the closed target section at an initial pressure not less than the opening pressure of the constant pressure valve (17); Step 6: Emission of residual combustion aid; S61: After the set amount of combustion-supporting agent is added, the oxygen injection device stops working and the oxygen (16) injection operation is stopped. When the pressure of the oxygen (16) in the gas storage space is less than the opening pressure of the constant pressure valve (17), the multiple constant pressure valves (17) return to the closed state; S62: increasing the opening of the second ball valve (18), increasing the injection rate of the nitrogen (15), so that the high-pressure nitrogen (15) pushes the piston (14) in the delivery tool body (11) to move downward, and using the downwardly moved piston (14) to pressurize the residual oxygen (16) in the gas storage space, and prompting the multiple constant pressure valves (17) to reopen, and at the same time, the residual oxygen (16) in the gas storage space is injected into the target section through the multiple constant pressure valves (17), so as to realize the discharge operation of the residual combustion-supporting agent, and the multiple constant pressure valves (17) are restored to the closed state; Step 7: Seal and compress to ignite; The nitrogen (15) filled in the annular space between the oil pipe (6) and the high-pressure hose (12) is used to maintain the piston (14) pressing the bottom plate of the bearing cylinder (21), and the self-resetting ability of the constant pressure valve (17) is assisted to jointly ensure the blocking state of the delivery tool body (11), so as to prevent the oxygen (16) in the wellbore (3) from flowing back into the delivery tool body (11); At the same time, the piston (14) pressed against the bottom plate of the bearing cylinder (21) is used to press and trigger the ignition device (19). After the ignition device (19) is triggered, the ignition electrode (20) is controlled to perform an ignition action, thereby realizing the ignition operation of the combustion aid.

2. The method for continuous delivery of combustion aid for methane in-situ explosion fracturing according to claim 1, characterized in that: In step 1 S11, ground geological survey is conducted using geological radar or seismic exploration techniques; in step 1 S14, the characteristics of the coal seam include the thickness, inclination and permeability of the coal seam.

3. A method for continuously adding combustion aid for methane in-situ explosion fracturing according to claim 1 or 2, characterized in that: In step 2 S22, the lower section of the oil pipe (6) is connected to the main body of the launching tool (11) by means of threaded engagement.

4. The method for continuous delivery of combustion aid for methane in-situ explosion fracturing according to claim 3, characterized in that: In step 2 S23, after the lowering and installation operation of the delivery tool is completed, the sealing between the oil pipe through pipe (13) and the wellbore through pipe (2) is checked again.

5. The method for continuous delivery of combustion aid for methane in-situ explosion fracturing according to claim 4, characterized in that: In step 2 S22, the air injection holes on the piston (14) and the air outlet holes on the bottom plate of the supporting cylinder (21) are in a staggered distribution state.

6. The method for continuous delivery of combustion aid for methane in-situ explosion fracturing according to claim 5, characterized in that: In step 2 S22, the ignition device (9) is provided with a built-in power supply.

7. The method for continuously placing a combustion aid for in-situ methane explosion fracturing according to claim 1, characterized in that: In step six S61, after the oxygen injection device stops working, the air inlet end of the high-pressure hose (12) can be connected to the nitrogen injection device, and a set amount of nitrogen (15) can be injected into the high-pressure hose (12) by using the nitrogen injection device, and the volume of oxygen (16) in the high-pressure hose (12) can be reduced by using the injected nitrogen (15).

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