Multi-stage pulse targeted staged fracturing method

Abstract

The invention discloses a multi-stage pulse targeted staged fracturing method. The method comprises the following steps: preparing work; constructing a fishbone well; tripping in a bridge plug; a required amount of combustion improver is filled into the throwing bin body on the ground, the fire blast bin body is vacuumized, and then a fire blast fracturing tool is put into the throwing bin body; enabling the combustion improver to quickly enter the combustion and explosion bin body by using high-pressure nitrogen to be mixed with methane to form combustion improver-methane mixed gas, and further completing the in-situ manufacturing process of the combustion and explosion fracturing bomb; the electric control connecting buckle is controlled to act, so that the blasting bin body is separated from the throwing bin body; after the separation and arrangement of the explosion bins of the multi-stage tool are completed, the packer is expanded and set in the target branch well section, and a closed explosion fracturing well section is formed between the set packer and the drillable bridge plug; and the ignition electrode is controlled to conduct ignition operation so as to detonate combustion improver-methane mixed gas in the fire blast fracturing bomb, and the explosion propagation process from outside to inside along the shaft is completed in a sympathetic detonation mode. By means of the method, multi-stage sectional type fire blast fracturing operation of the fractured well section can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of unconventional natural gas energy-saving exploitation, and in particular relates to a multi-stage pulse targeted segmented fracturing method. Background Art

[0002] my country has huge reserves of unconventional natural gas. As a clean energy, natural gas is expected to become an important energy source to replace coal in the future. However, due to the insufficient permeability of its reservoir, its mining efficiency is very low. At the same time, mining is very difficult, and fracturing and permeability enhancement operations are often required to improve mining efficiency. At present, hydraulic fracturing is the main fracturing method, but hydraulic fracturing technology has a series of problems such as difficulty in drainage, waste of water resources, and severe environmental pollution.

[0003] In order to effectively improve the fracturing effect of unconventional natural gas reservoirs and avoid the various drawbacks of hydraulic fracturing, some scholars have proposed an in-situ explosive fracturing technology using reservoir methane. This technology uses reservoir methane as fuel, and forms a methane-combustion-aid mixed gas at the bottom of the well or in the reservoir by artificially placing an oxidant. The methane-combustion-aid mixed gas is then detonated to produce instantaneous explosive high pressure, causing the reservoir to fracture to form impact cracks, thereby forming a complex three-dimensional fracture network, and ultimately achieving the increase in production and permeability of unconventional natural gas reservoirs. The explosive fracturing bomb fracturing method proposed on this basis pre-mixes methane-combustion-aid in the explosive device, arranges the fracturing bombs and ignites the explosive fracturing according to demand, making the explosive fracturing process more modular and convenient.

[0004] However, the pre-mixing method of traditional fracturing bombs poses great risks to the production, transportation, and operation of fracturing bombs. Therefore, it is urgent to provide a new multi-stage pulse targeted segmented fracturing method to effectively improve the safety factor. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a multi-stage pulse targeted segmented fracturing method. The entire fracturing process of this method is carried out underground, which can effectively reduce the risks in the process of making fracturing bombs and solve the safety hazards in the transportation and operation of traditional premixed fracturing bombs. At the same time, this method can realize multi-stage segmented explosive fracturing operations on the fracturing well section, which can significantly enhance the fracture effect of the reservoir. Compared with traditional hydraulic fracturing technology, this method does not require the consumption of a large amount of water resources and fracturing fluid, nor does it require large-scale fracturing equipment and a large amount of water resources. It can not only reduce water resource pollution and damage to the ground ecology, but also significantly reduce fracturing costs.

[0006] In order to achieve the above object, the present invention provides a multi-stage pulse targeted staged fracturing method, comprising the following steps:

[0007] Step 1: Preparation;

[0008] Arrange the well pattern according to the determined well positions and fracturing well sections, so that the main wellbore is arranged vertically and its end extends to a position close to the bottom of the target fracturing reservoir, and at the same time, the horizontal well connected to the end of the main wellbore passes through the target fracturing reservoir;

[0009] Step 2: Construct a fishbone well;

[0010] S21: Perform secondary transformation on the horizontal well, drill multiple horizontal branch wells connected to the horizontal well at different positions along the length direction of the horizontal well, and make the multiple horizontal branch wells and the axis of the horizontal well located in the same plane, so that the horizontal well and the multiple horizontal branch wells are distributed in a fishbone shape as a whole, thereby forming a fishbone well;

[0011] S22: After drilling all the construction well groups, determine the fracturing well sections in the fishbone wells, and then divide the fracturing well sections into multiple levels to obtain multiple target branch well sections;

[0012] Step 3: Lower the bridge plug;

[0013] A drillable bridge plug is run into the primary target branch well section and set;

[0014] Step 4: Run the explosive fracturing tool;

[0015] S41: Prepare the tool body, coiled tubing, surface injection equipment and surface control equipment;

[0016] Wherein, the tool body includes a delivery bin, a combustion and explosion bin and an electric control connecting buckle, the delivery bin includes a delivery bin body and a piston, the delivery bin body is cylindrical, an upper gas storage chamber is formed inside it, an upper air inlet is opened in the central area of ​​its top plate, and an air inlet pipeline is connected to the outer side of the upper air inlet, an upper air outlet is opened in the center of its bottom plate, and an air outlet connecting joint is connected to the outer side of the upper air outlet, and a constant pressure valve is installed in the upper air outlet; the piston is slidably and sealingly assembled in the interior of the delivery bin body; the combustion and explosion bin includes a combustion and explosion bin body and an ignition electrode; the combustion and explosion bin body is cylindrical, a lower gas storage chamber is formed inside it, a lower air inlet is opened in the central area of ​​its top plate, and an air inlet connecting joint is connected to the outer side of the lower air inlet, and at the same time, A one-way valve is installed in the lower air inlet, and a lower air outlet is opened at the bottom center thereof, and a solenoid valve is installed in the lower air outlet; a plurality of pressure relief holes are evenly opened on the circumference of the body of the explosion warehouse, and a plugging plate is installed in each pressure relief hole; the ignition electrode is installed on the bottom plate of the explosion warehouse; the explosion warehouse is connected to the delivery warehouse through an air inlet connection joint and an air outlet connection joint that are mutually sleeved; the electric control connection buckle is installed at the connection between the air inlet connection joint and the air outlet connection joint, which is used to lock the connection state between the air inlet connection joint and the air outlet connection joint, and at the same time, is used to unlock the connection state between the air inlet connection joint and the air outlet connection joint under the control of the ground control device; the electric control connection buckle is connected to the ground control device through a cable;

[0017] S42: Connect the end of the coiled tubing to the air inlet pipeline on the tool body, and connect the head end of the coiled tubing to the surface injection equipment; at the same time, connect the surface control equipment to the surface injection equipment;

[0018] S43: using a filling device on the ground to charge the required amount of combustion aid into the delivery bin, and at the same time, using a vacuum device to vacuum the explosion bin;

[0019] S44: lowering the tool body to the target well section using the coiled tubing;

[0020] Step 5: Fill the explosion chamber with methane;

[0021] The ground control equipment controls the solenoid valve to open the lower air outlet at the bottom of the explosion chamber, and the negative pressure is used to allow the methane in the annulus of the fracturing well section to enter the lower gas storage cavity through the lower air outlet. After the pressure inside and outside the explosion chamber is balanced, the solenoid valve is controlled to close.

[0022] Step 6: Placement of combustion aid and in-situ production of explosive fracturing bombs;

[0023] High-pressure nitrogen is pumped into the coiled tubing through the surface injection equipment. The continuously injected high-pressure nitrogen is used to continuously increase the pressure of the gas in the coiled tubing. The piston moves downward under the action of the gas pressure and squeezes the combustion aid in the upper storage chamber, causing the pressure of the gas in the upper storage chamber to continuously increase. When the pressure of the gas in the upper storage chamber reaches the opening threshold of the constant pressure valve, the constant pressure valve opens the upper air outlet at the bottom of the delivery bin, and the combustion aid is ejected through the upper air outlet in the open state, and quickly enters the combustion bin to mix with methane to form a combustion aid-methane mixed gas, thereby completing the in-situ production process of the combustion and fracturing bomb;

[0024] Step 7: Separation of combustion and explosion chambers;

[0025] The ground control equipment is used to control the action of the electric control connection buckle, so that the connection state between the air inlet connection joint and the air outlet connection joint is unlocked, thereby realizing the separation of the combustion chamber and the delivery chamber;

[0026] Step 8: Multi-stage arrangement of the explosion warehouse;

[0027] For the remaining target well sections, steps 4 to 7 are repeated in sequence to complete the segmented arrangement of the explosive fracturing bomb along the fracturing well section. For the tool arrangement of the last target well section, when executing step 4, a packer is installed on the outer side of the end of the coiled tubing, and the solenoid valve and the ignition electrode are respectively connected to the ground control equipment through cables. After completing step 6, skip steps 7 and 8 and directly execute step 9;

[0028] Step nine: setting the packer and igniting the fracturing well section;

[0029] S91: The packer is expanded and set in the primary target branch well section by means of coiled tubing pressure, and a closed explosive fracturing well section is formed between the set packer and the drillable bridge plug;

[0030] S92: Use ground control equipment to control the ignition electrode through cables to perform ignition operations to detonate the combustion-supporting agent-methane mixed gas in the explosive fracturing bomb, and complete the explosion transmission process from the outside to the inside along the wellbore by means of sympathetic explosion. During this process, the gas generated by the explosion of each level of explosive fracturing bomb breaks through the plugging plate in the pressure relief hole and rapidly expands into the wellbore. The generated flame and shock wave act on the reservoir to form a radial volume crack group; part of the shock wave is reflected multiple times in the explosive chamber, and after random strengthening and weakening, a multi-pulse effect is produced. Combined with the pulsating shock wave along the well section generated by the orderly sympathetic explosion of the multi-stage explosive fracturing bomb, the fracture-making effect on the reservoir is enhanced, thereby realizing the fracturing operation of the fracturing well section.

[0031] As a preferred embodiment, in step one, the well location and the fracturing well section are determined according to the well logging data, and the fracturing well section is divided into multiple levels to obtain a plurality of corresponding target well sections.

[0032] The outer diameter of the delivery bin is 100 mm and its height is 1100 mm; the outer diameter of the explosion bin is 100 mm and its height is 1000 mm.

[0033] Furthermore, in order to improve the sealing effect of the lower air storage chamber, the pressure relief hole is a step-shaped through hole, and the plugging piece is sealed in the pressure relief hole by an O-ring.

[0034] Preferably, the ground injection equipment is a ground fracturing truck.

[0035] In order to ensure the pressure-bearing strength of the piston, the thickness of the piston is 20 cm.

[0036] The multi-stage pulse targeted segmented fracturing method proposed in the present invention significantly increases the effective contact area between the wellbore and the reservoir by drilling multiple horizontal branch wells along the length direction of the horizontal well to construct a fishbone well, which is beneficial to improving the subsequent fracturing effect; by dividing the determined fracturing well section into multiple target branch well sections, it is convenient to enhance the fracture effect of the reservoir through multi-stage segmented explosion fracturing operations. The drillable bridge plug is lowered and sealed in the primary target branch well section, which can be convenient to work together with the subsequent packer sealed in the final target branch well section to form an effective seal for the fracturing well section, which is beneficial to improving the subsequent explosion effect. The explosion chamber is vacuumed in advance, and an electromagnetic valve is installed in the lower air outlet at the bottom of the explosion chamber, which can conveniently control the opening of the electromagnetic valve, so that the methane gas in the wellbore annulus can be gathered into the explosion chamber through the negative pressure. The delivery bin is pre-filled with a combustion aid, and a constant pressure valve is installed in the upper air outlet at the bottom, so that high-pressure nitrogen can be used to act on the piston, and the combustion aid can be quickly sprayed into the delivery bin through the constant pressure valve, which can promote the combustion aid to be quickly mixed with methane gas in the combustion and explosion bin, thereby realizing the in-situ production process of the combustion and explosion fracturing bomb in the fracturing well section; this method not only effectively ensures the full mixing of the combustion aid and methane gas, ensures the mixing efficiency of the combustion aid and methane gas, which is beneficial to improving the subsequent combustion and explosion effect, but also avoids the safety risks during the mixing and transportation process on the ground, and greatly improves the safety factor of the operation. An electrically controlled connecting buckle is arranged at the connection between the air inlet connecting joint of the explosive chamber and the air outlet connecting joint of the delivery chamber, which can conveniently realize the separation and multi-stage arrangement operation of the explosive fracturing bomb chamber, and then the explosive fracturing bomb can be flexibly arranged at different positions in the wellbore according to the reservoir characteristics and fracturing requirements. The ignition and sympathetic detonation process is completed by the multi-stage arrangement of the explosive fracturing bomb in conjunction with the last-stage tool, so that multiple stages can be detonated simultaneously or sequentially, which is conducive to the formation of a complex fracture network, and can significantly improve the permeability and recovery rate of the reservoir, which can help increase oil and gas production and improve economic benefits.

[0037] The method aims to realize the in-situ production of explosive fracturing bombs and multi-stage segmented targeted fracturing of methane-rich reservoirs. It uses a negative pressure magazine to gather methane gas, and uses pre-charging of the combustion aid to complete the mixing of the combustion aid and methane gas in the explosive fracturing bomb, thereby realizing the in-situ production of the explosive fracturing bomb, which can effectively reduce the risk of the fracturing bomb production process and solve the safety hazards in the transportation and operation of traditional premixed fracturing bombs. At the same time, the method realizes the multi-stage segmented explosive fracturing operation of the fracturing well section by separating the explosive fracturing bombs along the well section, and enhances the fracture effect of the reservoir. The entire fracturing process of this method is carried out underground, avoiding the safety risks brought by ground operations. At the same time, it can effectively reduce the damage to the wellbore and reservoir by accurately controlling the amount of the combustion aid and the explosion time. Compared with traditional hydraulic fracturing technology, this method does not require a large amount of water resources and fracturing fluid, nor does it require large-scale fracturing equipment and a large amount of water resources, which not only reduces water resource pollution and damage to the ground ecology, but also reduces the cost of fracturing. At the same time, this method uses methane gas desorbed in situ from the reservoir as fuel, reducing carbon emissions and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the layout of the fishbone wells in the present invention;

[0039] Figure 2 It is a schematic diagram of the state of lowering the tool body using the coiled tubing of the present invention;

[0040] Figure 3 is a cross-sectional view of the delivery bin in the present invention;

[0041] Figure 4 It is a cross-sectional view of the combustion chamber in the present invention;

[0042] Figure 5 It is a schematic diagram of the assembly of the delivery bin and the explosion bin through the electric control connection buckle in the present invention;

[0043] Figure 6 It is a schematic diagram of the state in which negative pressure acts on the explosion chamber in the present invention;

[0044] Figure 7 This is a schematic diagram of the mixing state of the combustion aid in the present invention;

[0045] Figure 8 It is a schematic diagram of the separation and arrangement of the combustion and explosion chambers in the present invention;

[0046] Fig. 9 It is a schematic diagram of the sealing and ignition of the end tool in the present invention.

[0047] In the figure: 1. main wellbore, 2. horizontal well, 3. fishbone well, 4. target fracturing reservoir, 5. drillable bridge plug, 6. tool body, 7. continuous oil pipe, 8. delivery chamber, 9. combustion chamber, 10. piston, 11. upper gas storage chamber, 12. constant pressure valve, 13. one-way valve, 14. plugging piece, 15. ignition electrode, 16. solenoid valve, 17. electric control connector, 18. cable, 19. fracturing well section, 20. methane, 21. high-pressure nitrogen, 22. combustion aid, 23. combustion aid-methane mixed gas, 24. packer, 25. air inlet pipeline, 26. delivery chamber, 27. combustion chamber, 28. horizontal branch well, 29. air outlet connection joint, 30. lower gas storage chamber, 31. air inlet connection joint. DETAILED DESCRIPTION

[0048] In order to achieve multi-stage segmented fracturing and enhance the reservoir fracture-making effect of methane-enriched reservoirs, the present invention provides a multi-stage pulse targeted segmented fracturing method, which adopts the method of pre-charging of combustion aid and in-situ production of explosive fracturing bombs to complete the mixing of the combustion aid-methane gas in the fracturing well section, and realizes multi-stage segmented explosive fracturing operation of the fracturing well section by arranging the explosive fracturing bombs separately along the well section. The radial targeted impact flames generated by the explosive fracturing bombs and the pulsating shock waves generated by the sympathetic explosion along the well section act on the reservoir to form a radial volume fracture group, which greatly enhances the reservoir fracture-making effect.

[0049] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0050] like Figures 1 to 9 As shown, the present invention provides a multi-stage pulse targeted staged fracturing method, comprising the following steps:

[0051] Step 1: Preparation;

[0052] like Figure 1 As shown, the well pattern is arranged according to the determined well layout position and the fracturing well section 19, so that the main wellbore 1 is arranged vertically, and its end is extended to a position close to the bottom of the target fracturing reservoir 4, and at the same time, the horizontal well 2 connected to the end of the main wellbore 1 passes through the target fracturing reservoir 4;

[0053] Step 2: Construct fishbone well 3;

[0054] S21: Perform secondary transformation on the horizontal well 2, drill multiple horizontal branch wells 28 connected to the horizontal well 2 at different positions along the length direction of the horizontal well 2, and make the multiple horizontal branch wells 28 and the axis of the horizontal well 2 located in the same plane, so that the horizontal well 2 and the multiple horizontal branch wells 28 are distributed in a fishbone shape as a whole, thereby forming a fishbone well 3, such as Figure 1 As shown;

[0055] S22: After drilling all the construction well groups, determine the fracturing well section in the fishbone well 3, and then divide the fracturing well section into multiple levels to obtain multiple target branch well sections;

[0056] Step 3: Lower the bridge plug;

[0057] A drillable bridge plug 5 is run into the primary target branch well section and is set;

[0058] Step 4: Run the explosive fracturing tool;

[0059] S41: Prepare the tool body 6, the coiled tubing 7, the surface injection equipment and the surface control equipment;

[0060] For the tool body 6, as Figure 3 As shown, the tool body 6 includes a delivery bin 8, a combustion bin 9 and an electric control connection buckle 17. The delivery bin 8 includes a delivery bin body 26 and a piston 10. The delivery bin body 26 is cylindrical, and an upper gas storage chamber 11 is formed inside it. An upper gas inlet hole is opened in the central area of ​​the top plate, and an air inlet pipeline 25 is connected to the outer side of the upper gas inlet hole. An upper gas outlet hole is opened in the center of the bottom plate, and an air outlet connection joint 29 is connected to the outer side of the upper gas outlet hole. At the same time, a constant pressure valve 12 is installed in the upper gas outlet hole. The constant pressure valve 12 controls the pressure in the upper gas storage chamber 11. After the force reaches the starting pressure, the upper air outlet is opened to allow the combustion aid 22 to be discharged smoothly; the piston 10 is slidably and sealingly assembled inside the delivery bin body 26, and can slide axially in the upper gas storage chamber 11, and seal with the inner wall of the delivery bin 8. After the continuous oil pipe 7 is connected to the air inlet pipeline 25, the gas entering the continuous oil pipe 7 can directly act on the upper surface of the piston 10, and then the gas in the continuous oil pipe 7 can be used to drive the piston 10 to move on the axis; the upper gas storage chamber 11 is used to store the combustion aid;

[0061] like Figure 4As shown, the explosion chamber 9 includes an explosion chamber body 27 and an ignition electrode 15; the explosion chamber body 27 is cylindrical, and a lower gas storage cavity 30 is formed inside it. A lower air inlet hole is opened in the central area of ​​the top plate, and an air inlet connection joint 31 is connected to the outer side of the lower air inlet hole. At the same time, a one-way valve 13 is installed in the lower air inlet hole, and a lower air outlet hole is opened in the center of the bottom, and an electromagnetic valve 16 is installed in the lower air outlet hole; the setting of the one-way valve 13 can ensure that the external gas can only flow into the lower gas storage through the one-way valve 13 cavity 30, and the gas in the lower gas storage cavity 30 will not flow out through the one-way valve 13; the solenoid valve 16 is used to connect the lower gas storage cavity 30 and the wellbore annulus after opening, and is used to maintain the sealing state of the lower gas storage cavity 30 after closing; a plurality of pressure relief holes are evenly opened on the circumference of the storage body of the explosion storage body 27, and a plug 14 is installed in each pressure relief hole; the ignition electrode 15 is installed on the bottom plate of the explosion storage body 27; and the plurality of pressure relief holes serve as the main output channels for the shock wave flame during the explosion process.

[0062] The explosion chamber 27 is connected to the delivery chamber 26 through the mutually sleeved air inlet connection joint 31 and the air outlet connection joint 29; the electric control connection buckle 17 is installed at the connection between the air inlet connection joint 31 and the air outlet connection joint 29, which is used to lock the connection state between the air inlet connection joint 31 and the air outlet connection joint 29, and at the same time, is used to unlock the connection state between the air inlet connection joint 31 and the air outlet connection joint 29 under the control of the ground control device; the electric control connection buckle 17 is connected to the ground control device through the cable 18;

[0063] S42: Connect the end of the coiled tubing 7 to the air inlet pipe 25 on the tool body 6, and connect the head end of the coiled tubing 7 to the surface injection equipment; at the same time, connect the surface control equipment to the surface injection equipment;

[0064] S43: using a filling device on the ground to charge the required amount of combustion aid 22 into the delivery bin 26, and at the same time, using a vacuum device to vacuum the explosion bin 27;

[0065] S44: Use the coiled tubing 7 to lower the tool body 6 to the target well section. Figure 2 As shown;

[0066] Step 5: Fill the explosion chamber 27 with methane 20;

[0067] The electromagnetic valve 16 is controlled by the ground control equipment to open the lower gas outlet at the bottom of the explosion chamber 27, and the methane 20 in the annulus of the fracturing well section 19 enters the lower gas storage chamber 30 through the lower gas outlet. Figure 6 As shown, after the pressure inside and outside the explosion chamber 9 is balanced, the solenoid valve 16 is controlled to close;

[0068] Step 6: placing the combustion aid 22 and in-situ production of the explosive fracturing bomb;

[0069] High-pressure nitrogen 21 is pumped into the coiled tubing 7 through the surface injection equipment. The continuously injected high-pressure nitrogen 21 is used to increase the pressure of the gas in the coiled tubing 7. The piston 10 moves downward under the action of the gas pressure and squeezes the combustion aid 22 in the upper storage chamber 11, so that the pressure of the gas in the upper storage chamber 11 is continuously increased. When the pressure of the gas in the upper storage chamber 11 reaches the opening threshold of the constant pressure valve 12, the constant pressure valve 12 opens the upper air outlet at the bottom of the delivery bin 26, and the combustion aid 22 is ejected through the upper air outlet in the opened state, and quickly enters the combustion bin 27 to mix with the methane 20 to form a combustion aid-methane mixed gas 23, thereby completing the in-situ production process of the combustion and fracturing bomb. Figure 7 As shown;

[0070] Step 7: Separation of combustion and explosion chambers;

[0071] The ground control device controls the electric control connection buckle 17 to unlock the connection between the air inlet connection joint 31 and the air outlet connection joint 29, so as to separate the explosion chamber 9 from the delivery chamber 8. Figure 8 As shown;

[0072] Step 8: Multi-stage arrangement of the explosion warehouse;

[0073] For the remaining target well sections, steps 4 to 7 are repeated in sequence to complete the segmented arrangement of the explosive fracturing bomb along the fracturing well section 19. For the tool arrangement of the last target well section, when executing step 4, a packer 24 is installed on the outer side of the end of the coiled tubing 7, and the solenoid valve 16 and the ignition electrode 15 are respectively connected to the ground control equipment through the cable 18. After completing step 6, skip steps 7 and 8 and directly execute step 9;

[0074] Step nine: setting the packer 24 and igniting the fracturing well section 19;

[0075] S91: The packer 24 is expanded and set in the primary target branch well section by means of pressurizing the coiled tubing 7, and a closed explosive fracturing well section is formed between the set packer 24 and the drillable bridge plug 15, such as Fig. 9 As shown;

[0076] S92: Use ground control equipment to control the ignition electrode 15 through the cable 8 to perform ignition operation, so as to detonate the combustion-aiding agent-methane mixed gas 23 in the explosive fracturing bomb, and complete the explosion transmission process from the outside to the inside along the wellbore by means of sympathetic explosion. In this process, the gas generated by the explosion of each stage of the explosive fracturing bomb magazine breaks through the plug 14 in the pressure relief hole and rapidly expands into the wellbore. The generated flame and shock wave act on the reservoir to form a radial volume crack group; part of the shock wave is reflected multiple times in the explosive magazine body 27, and a multi-pulse effect is produced after random strengthening and weakening. Combined with the pulsating shock wave along the well section generated by the orderly sympathetic explosion of the multi-stage explosive fracturing bomb, the fracture-making effect on the reservoir is greatly enhanced, thereby realizing the fracturing operation of the fracturing well section 19.

[0077] As a preferred embodiment, in step one, the well layout position and the fracturing well section 19 are determined according to the well logging data, and the fracturing well section 19 is divided into multiple levels to obtain a plurality of corresponding target well sections.

[0078] As a preferred embodiment, the outer diameter of the delivery bin body 26 is 100 mm and the height thereof is 1100 mm; the outer diameter of the explosion bin body 27 is 100 mm and the height thereof is 1000 mm.

[0079] In order to improve the sealing effect of the lower gas storage chamber, the pressure relief hole is a step-shaped through hole, and the plugging piece 14 is sealed in the pressure relief hole by an O-ring. Preferably, the pressure relief hole is composed of a small-diameter hole and a large-diameter hole, wherein the small-diameter hole is close to the outer surface of the explosion chamber body 27, and the large-diameter hole is far away from the outer surface of the explosion chamber body 27, and the size of the plugging piece 14 is adapted to the size of the large-diameter hole, and is assembled at the outer end of the large-diameter hole, and the O-ring is mounted on the outer edge of the plugging piece 14 to achieve a sealed connection between the plugging piece 14 and the large-diameter hole.

[0080] Preferably, the ground injection equipment is a ground fracturing truck.

[0081] In order to ensure the pressure-bearing strength of the piston, the thickness of the piston 10 is 20 cm.

[0082] The multi-stage pulse targeted segmented fracturing method proposed in the present invention significantly increases the effective contact area between the wellbore and the reservoir by drilling multiple horizontal branch wells along the length direction of the horizontal well to construct a fishbone well, which is beneficial to improving the subsequent fracturing effect; by dividing the determined fracturing well section into multiple target branch well sections, it is convenient to enhance the fracture effect of the reservoir through multi-stage segmented explosion fracturing operations. The drillable bridge plug is lowered and sealed in the primary target branch well section, which can be convenient to work together with the subsequent packer sealed in the final target branch well section to form an effective seal for the fracturing well section, which is beneficial to improving the subsequent explosion effect. The explosion chamber is vacuumed in advance, and an electromagnetic valve is installed in the lower air outlet at the bottom of the explosion chamber, which can conveniently control the opening of the electromagnetic valve, so that the methane gas in the wellbore annulus can be gathered into the explosion chamber through the negative pressure. The delivery bin is pre-filled with a combustion aid, and a constant pressure valve is installed in the upper air outlet at the bottom, so that high-pressure nitrogen can be used to act on the piston, and the combustion aid can be quickly sprayed into the delivery bin through the constant pressure valve, which can promote the combustion aid to be quickly mixed with methane gas in the combustion and explosion bin, thereby realizing the in-situ production process of the combustion and explosion fracturing bomb in the fracturing well section; this method not only effectively ensures the full mixing of the combustion aid and methane gas, ensures the mixing efficiency of the combustion aid and methane gas, which is beneficial to improving the subsequent combustion and explosion effect, but also avoids the safety risks during the mixing and transportation process on the ground, and greatly improves the safety factor of the operation. An electrically controlled connecting buckle is arranged at the connection between the air inlet connecting joint of the explosive chamber and the air outlet connecting joint of the delivery chamber, which can conveniently realize the separation and multi-stage arrangement operation of the explosive fracturing bomb chamber, and then the explosive fracturing bomb can be flexibly arranged at different positions in the wellbore according to the reservoir characteristics and fracturing requirements. The ignition and detonation process is completed by the multi-stage arrangement of the explosive fracturing bomb in conjunction with the last-stage tool, and multiple stages can be detonated simultaneously or sequentially, which is conducive to forming a complex fracture network, and can significantly improve the permeability and recovery rate of the reservoir, which can help increase oil and gas production and improve economic benefits.

[0083] The method aims to realize the in-situ production of explosive fracturing bombs and multi-stage segmented targeted fracturing of methane-rich reservoirs. It uses a negative pressure magazine to gather methane gas, and uses pre-charging of the combustion aid to complete the mixing of the combustion aid and methane gas in the explosive fracturing bomb, thereby realizing the in-situ production of the explosive fracturing bomb, which can effectively reduce the risk of the fracturing bomb production process and solve the safety hazards in the transportation and operation of traditional premixed fracturing bombs. At the same time, the method realizes the multi-stage segmented explosive fracturing operation of the fracturing well section by separating the explosive fracturing bombs along the well section, and enhances the fracture effect of the reservoir. The entire fracturing process of this method is carried out underground, avoiding the safety risks brought by ground operations. At the same time, it can effectively reduce the damage to the wellbore and reservoir by accurately controlling the amount of the combustion aid and the explosion time. Compared with traditional hydraulic fracturing technology, this method does not require a large amount of water resources and fracturing fluid, nor does it require large-scale fracturing equipment and a large amount of water resources, which not only reduces water resource pollution and damage to the ground ecology, but also reduces the cost of fracturing. At the same time, this method uses methane gas desorbed in situ from the reservoir as fuel, reducing carbon emissions and environmental pollution.

Claims

1. A multi-stage pulse targeted staged fracturing method, characterized in that: The steps include: Step 1: Preparation; The well pattern is arranged according to the determined well positions and the fracturing well sections (19), so that the main wellbore (1) is arranged vertically and its end is extended to a position close to the bottom of the target fracturing reservoir (4), and at the same time, the horizontal well (2) connected to the end of the main wellbore (1) passes through the target fracturing reservoir (4); Step 2: construct a fishbone well (3); S21: performing secondary transformation on the horizontal well (2), drilling a plurality of horizontal branch wells (28) connected to the horizontal well (2) at different positions along the length direction of the horizontal well (2), and making the axes of the plurality of horizontal branch wells (28) and the horizontal well (2) located in the same plane, so that the horizontal well (2) and the plurality of horizontal branch wells (28) are distributed in a fishbone shape as a whole, thereby forming a fishbone well (3); S22: After all the construction well groups are drilled, the fracturing well section (19) in the fishbone well (3) is determined, and then the fracturing well section (19) is divided into multiple levels to obtain multiple target branch well sections; Step 3: Lower the bridge plug; A drillable bridge plug (5) is run into the primary target branch well section and is set; Step 4: Run the explosive fracturing tool; S41: Prepare the tool body (6), coiled tubing (7), surface injection equipment and surface control equipment; The tool body (6) comprises a delivery chamber (8), an explosion chamber (9) and an electric control connection buckle (17); the delivery chamber (8) comprises a delivery chamber body (26) and a piston (10); the delivery chamber body (26) is cylindrical, and an upper air storage chamber (11) is formed inside the delivery chamber body; an upper air inlet is provided in the central area of ​​the top plate, and an air inlet pipeline (25) is connected to the outer side of the upper air inlet; an upper air outlet is provided in the center of the bottom plate, and an air outlet connection (25) is connected to the outer side of the upper air outlet. The piston (10) is slidably and sealingly mounted inside the delivery bin (26); the combustion bin (9) comprises a combustion bin body (27) and an ignition electrode (15); the combustion bin body (27) is cylindrical, and a lower gas storage cavity (30) is formed inside the combustion bin body; a lower gas inlet hole is opened in the center area of ​​the top plate, and an inlet connection joint (31) is connected to the outer side of the lower gas inlet hole; at the same time, A one-way valve (13) is installed in the air inlet, and a lower air outlet is opened at the center of the bottom thereof, and a solenoid valve (16) is installed in the lower air outlet; a plurality of pressure relief holes are evenly opened on the circumference of the body of the explosion chamber (27), and a plug (14) is installed in each pressure relief hole; the ignition electrode (15) is installed on the bottom plate of the explosion chamber (27); the explosion chamber (27) is connected to the delivery chamber (26) through an air inlet connection joint (31) and an air outlet connection joint (29) which are mutually sleeved; the electric control connection buckle (17) is installed at the connection between the air inlet connection joint (31) and the air outlet connection joint (29), and is used to lock the connection state between the air inlet connection joint (31) and the air outlet connection joint (29), and at the same time, is used to unlock the connection state between the air inlet connection joint (31) and the air outlet connection joint (29) under the control of the ground control device; the electric control connection buckle (17) is connected to the ground control device through a cable (18); S42: Connect the end of the coiled tubing (7) to the air inlet pipeline (25) on the tool body (6), and connect the head end of the coiled tubing (7) to the surface injection equipment; at the same time, connect the surface control equipment to the surface injection equipment; S43: Using a filling device on the ground to charge the required amount of combustion-supporting agent (22) into the delivery bin (26), and at the same time, using a vacuum device to evacuate the explosion bin (27); S44: lowering the tool body (6) to the target well section using the coiled tubing (7); Step 5: Filling the explosion chamber (27) with methane (20); The electromagnetic valve (16) is controlled by the ground control equipment to open the lower air outlet at the bottom of the explosion chamber (27), and the methane (20) in the annulus of the fracturing well section (19) is allowed to enter the lower gas storage cavity (30) through the lower air outlet by using the negative pressure. After the pressure inside and outside the explosion chamber (9) is balanced, the electromagnetic valve (16) is controlled to close; Step 6: placing the combustion aid (22) and in-situ production of the explosive fracturing bomb; High-pressure nitrogen (21) is pumped into the continuous oil pipe (7) through the surface injection equipment. The continuously injected high-pressure nitrogen (21) is used to continuously increase the pressure of the gas in the continuous oil pipe (7). The piston (10) moves downward under the action of the gas pressure and squeezes the combustion aid (22) in the upper storage chamber (11), so that the pressure of the gas in the upper storage chamber (11) is continuously increased. When the pressure of the gas in the upper storage chamber (11) reaches the opening threshold of the constant pressure valve (12), the constant pressure valve (12) opens the upper air outlet at the bottom of the delivery bin (26), and the combustion aid (22) is ejected through the upper air outlet in the opened state and quickly enters the combustion bin (27) to mix with the methane (20) to form a combustion aid-methane mixed gas (23), thereby completing the in-situ production process of the combustion and fracturing bomb; Step 7: Separation of combustion and explosion chambers; The electric control connection buckle (17) is controlled by the ground control equipment to unlock the connection between the air inlet connection joint (31) and the air outlet connection joint (29), thereby realizing the separation of the combustion chamber (9) and the delivery chamber (8); Step 8: Multi-stage arrangement of the explosion warehouse; For each of the remaining target well sections, steps 4 to 7 are repeated in sequence to complete the segmented arrangement of the explosive fracturing bomb along the fracturing well section (19). For the tool arrangement of the last target well section, when executing step 4, a packer (24) is installed on the outer side of the end of the coiled tubing (7), and the solenoid valve (16) and the ignition electrode (15) are respectively connected to the ground control equipment through the cable (18). After completing step 6, steps 7 and 8 are skipped and step 9 is directly executed; Step nine: setting the packer (24) and igniting the fracturing well section (19); S91: by means of pressurizing the coiled tubing (7), the packer (24) is expanded and set in the primary target branch well section, and a closed explosive fracturing well section is formed between the set packer (24) and the drillable bridge plug (15); S92: Use ground control equipment to control the ignition electrode (15) through the cable (8) to perform ignition operation, so as to detonate the combustion-supporting agent-methane mixed gas (23) in the explosive fracturing bomb, and complete the explosion transmission process from the outside to the inside along the wellbore by means of sympathetic explosion. During this process, the gas generated by the explosion of each stage of the explosive fracturing bomb chamber breaks through the plug (14) in the pressure relief hole and expands rapidly into the wellbore. The generated flame and shock wave act on the reservoir to form a radial volume fracture group; part of the shock wave is reflected multiple times in the explosive chamber body (27), and a multi-pulse effect is generated after random strengthening and weakening. Combined with the pulsating shock wave along the well section generated by the orderly sympathetic explosion of the multi-stage explosive fracturing bomb, the fracture-making effect on the reservoir is strengthened, thereby realizing the fracturing operation of the fracturing well section.

2. A multi-stage pulse targeted staged fracturing method according to claim 1, characterized in that: In step one, the well location and the fracturing well section (19) are determined according to the well logging data, and the fracturing well section (19) is divided into multiple levels to obtain a plurality of corresponding target well sections.

3. A multi-stage pulse targeted staged fracturing method according to claim 1 or 2, characterized in that: The outer diameter of the delivery bin (26) is 100 mm and its height is 1100 mm; the outer diameter of the explosion bin (27) is 100 mm and its height is 1000 mm.

4. A multi-stage pulse targeted staged fracturing method according to claim 3, characterized in that: The pressure relief hole is a step-shaped through hole, and the plug (14) is sealed in the pressure relief hole via an O-shaped sealing ring.

5. A multi-stage pulse targeted staged fracturing method according to claim 1, characterized in that: The ground injection equipment is a ground fracturing vehicle.

6. A multi-stage pulse targeted staged fracturing method according to claim 1, characterized in that: The thickness of the piston (10) is 20 cm.

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