A multi-stage pulse targeted fracturing method

Abstract

A multi-stage pulse target section fracturing method, preparation work; Constructing fishbone well; Lowering bridge plug; Ground to the delivery bin body into the required amount of combustion improver, and vacuum treatment to the explosion bin body, then lowering the explosion fracturing tool; Using high pressure nitrogen to make combustion improver rapidly enter the explosion bin body and mix with methane to form combustion improver-methane mixed gas, and then complete the in-situ production process of explosion fracturing bomb; Control the action of electric control connection buckle to separate the explosion bin body from the delivery bin body; After the separation and arrangement of the multi-stage tool explosion bin are completed, the packer is expanded and set in the target branch well section, forming a closed explosion fracturing well section between the set packer and the drillable bridge plug; Control the ignition electrode to perform ignition operation to detonate the combustion improver-methane mixed gas in the explosion fracturing bomb, and complete the transmission process from outside to inside along the wellbore by the way of sympathetic detonation. The method can realize multi-stage segmented explosion fracturing operation of the fracturing well section.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of unconventional natural gas energy-saving exploitation, and particularly relates to a multi-stage pulse targeted segmented fracturing method. BACKGROUND

[0002] China has huge unconventional natural gas reserves, and natural gas is expected to become an important energy source to replace coal in the future as a clean energy source. However, due to the insufficient permeability of the reservoir, the exploitation efficiency is very low, and at the same time, the exploitation is very difficult, often requiring fracturing reconstruction and permeability improvement operation to improve the exploitation efficiency. At the present stage, the fracturing mode is mainly hydraulic fracturing, but the hydraulic fracturing technology has a series of problems such as difficult liquid discharge, waste of water resources, and serious environmental pollution.

[0003] In order to effectively improve the fracturing effect of unconventional natural gas reservoirs, and to avoid various disadvantages of hydraulic fracturing, some scholars have proposed a reservoir methane in-situ combustion fracturing technology. The technology uses reservoir methane as fuel, forms methane-combustion-supporting agent mixed gas at the well bottom or in the reservoir by artificially putting combustion-supporting agent, and produces instantaneous combustion high pressure by methane-combustion-supporting agent mixed gas explosion to crack the reservoir and form impact cracks, so as to form a complex three-dimensional fracture network, and finally realize the production and permeability improvement operation of unconventional natural gas reservoirs. On this basis, the combustion fracturing bomb fracturing method mixes methane-combustion-supporting agent in the combustion device in advance, arranges and ignites the combustion-supporting agent according to the needs of the reservoir to perform combustion fracturing, so that the combustion fracturing process is more modular and convenient.

[0004] However, the pre-mixed method of the traditional fracturing bomb has great hidden dangers in the production, transportation and operation of the fracturing bomb, and therefore, it is urgent to provide a new multi-stage pulse targeted segmented fracturing method to effectively improve the safety factor. SUMMARY

[0005] In view of the problems existing in the prior art, the application provides a multi-stage pulse targeted segmented fracturing method, which can effectively reduce the risk of the fracturing bomb manufacturing process, solve the safety hidden danger in the transportation and operation process of the traditional pre-mixed fracturing bomb, and at the same time, can realize multi-stage segmented combustion fracturing operation of the fracturing well section, and can significantly strengthen the fracture forming effect of the reservoir. Compared with the traditional hydraulic fracturing technology, the method does not need to consume a large amount of water resources and fracturing fluid, and does not need large fracturing equipment and a large amount of water resources, which can not only reduce water resource pollution and damage to the ground ecology, but also significantly reduce the fracturing cost.

[0006] In order to achieve the above purpose, the application provides a multi-stage pulse targeted segmented fracturing method, which comprises the following steps:

[0007] Step 1: preparation work;

[0008] According to the determined well pattern arrangement of the well pattern and the fracturing well section, the main wellbore is vertically arranged, and the end of the main wellbore extends to a position close to the bottom of the target fracturing reservoir, and the horizontal well communicated with the end of the main wellbore penetrates through the target fracturing reservoir;

[0009] Step two: constructing the fishbone well;

[0010] S21: performing secondary reconstruction on the horizontal well, drilling multiple horizontal branch wells communicated with the horizontal well at different positions along the length direction of the horizontal well, and making 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 constructing the fishbone well;

[0011] S22: after all the well groups are drilled, determining the fracturing well section in the fishbone well, and performing multi-stage division on the fracturing well section to obtain multiple target branch well sections;

[0012] Step three: running the bridge plug;

[0013] Running the drillable bridge plug in the primary target branch well section, and making the drillable bridge plug set and seal;

[0014] Step four: running the combustion fracturing tool;

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

[0016] The tool body comprises a delivery bin, a combustion bin and an electric control connecting buckle. The delivery bin comprises a delivery bin body and a piston. The delivery bin body is cylindrical, and an upper gas storage chamber is formed in the delivery bin body. An upper gas inlet hole is formed in the center area of the top plate of the delivery bin body, and a gas inlet pipeline is connected to the outside of the upper gas inlet hole. A gas outlet connecting joint is connected to the outside of an upper gas outlet hole formed in the center of the bottom plate of the delivery bin body. A pressure regulating valve is installed in the upper gas outlet hole. The piston is slidingly and sealingly assembled in the delivery bin body. The combustion bin comprises a combustion bin body and an ignition electrode. The combustion bin body is cylindrical, and a lower gas storage chamber is formed in the combustion bin body. A lower gas inlet hole is formed in the center area of the top plate of the combustion bin body, and a gas inlet connecting joint is connected to the outside of the lower gas inlet hole. A one-way valve is installed in the lower gas inlet hole. A lower gas outlet hole is formed in the center of the bottom plate of the combustion bin body, and an electromagnetic valve is installed in the lower gas outlet hole. A plurality of pressure relief holes are uniformly formed in the circumference of the bin body of the combustion bin body, and a baffle is installed in each pressure relief hole. The ignition electrode is installed on the bottom plate of the combustion bin body. The combustion bin body is connected to the delivery bin body through the gas inlet connecting joint and the gas outlet connecting joint. The electric control connecting buckle is installed at the connection between the gas inlet connecting joint and the gas outlet connecting joint, and is used to lock the connection state between the gas inlet connecting joint and the gas outlet connecting joint. Meanwhile, the electric control connecting buckle is used to unlock the connection state between the gas inlet connecting joint and the gas outlet connecting joint under the control of the ground control equipment. The electric control connecting buckle is connected to the ground control equipment through a cable.

[0017] S42: The end of the coiled tubing is connected to the gas inlet pipeline of the tool body, and the first end of the coiled tubing is connected to the ground injection equipment. Meanwhile, the ground control equipment is connected to the ground injection equipment.

[0018] S43: The required amount of combustion-supporting agent is filled into the delivery bin body on the ground using the injection equipment, and the combustion bin body is vacuumized using a vacuumizing device.

[0019] S44: The tool body is lowered to the target well section using the coiled tubing.

[0020] Step five: methane is filled into the combustion bin body.

[0021] The electromagnetic valve is controlled to open the lower gas outlet hole at the bottom of the combustion bin body by the ground control equipment. The methane in the annulus of the fractured well section enters the lower gas storage chamber through the lower gas outlet hole under the action of negative pressure. After the pressure inside and outside the combustion bin body is balanced, the electromagnetic valve is controlled to be closed.

[0022] Step six: combustion-supporting agent delivery and in-situ production of the combustion fracturing bomb.

[0023] The high-pressure nitrogen gas is pumped into the coiled tubing through the ground injection equipment, the pressure of the gas in the coiled tubing is continuously increased by the continuously injected high-pressure nitrogen gas, the piston is driven downward by the gas pressure and squeezes the combustion-supporting agent in the upper storage chamber, the pressure of the gas in the upper storage chamber is continuously increased, 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 gas outlet hole at the bottom of the delivery chamber, the combustion-supporting agent is sprayed out through the open upper gas outlet hole and quickly enters the combustion chamber to mix with the methane to form the combustion-supporting agent-methane mixed gas, thereby completing the in-situ production process of the combustion and explosion fracturing bomb.

[0024] Step seven: separation of the combustion chamber;

[0025] The connection state between the gas inlet connection joint and the gas outlet connection joint is unlocked by controlling the action of the electrically-controlled connection buckle through the ground control equipment, so as to realize the separation of the combustion chamber and the delivery chamber;

[0026] Step eight: multi-section arrangement of the combustion chamber;

[0027] For the remaining target well sections, steps four to seven are repeatedly executed in sequence to complete the segmented arrangement of the combustion and explosion fracturing bomb along the fracturing well section, wherein for the tool arrangement of the last target well section, the packer is sleeved outside the end of the coiled tubing when step four is executed, and the electromagnetic valve and the ignition electrode are respectively connected with the ground control equipment through the cable, after step six is completed, step seven and step eight are skipped and step nine is directly executed;

[0028] Step nine: the packer is set and the fracturing well section is ignited;

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

[0030] S92: the ignition electrode is ignited by the ground control equipment through the cable to detonate the combustion-supporting agent-methane mixed gas in the combustion and explosion fracturing bomb, and the transmission process from outside to inside along the wellbore is completed by the way of sympathetic detonation, in this process, the gas produced by the explosion of each level of the combustion and explosion fracturing bomb breaks through the blocking piece 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 volumetric fracture group; part of the shock wave reflects multiple times in the combustion chamber, and after random strengthening and weakening, a multi-pulse effect is produced, combined with the pulsed shock wave along the well section produced by the ordered sympathetic detonation of the multi-section combustion and explosion fracturing bomb, the fracturing effect on the reservoir is strengthened, and then the fracturing operation on the fracturing well section is realized.

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

[0032] The outer diameter of the delivery chamber is 100mm, and the height thereof is 1100mm; the outer diameter of the combustion chamber is 100mm, and the height thereof is 1000mm.

[0033] Further, in order to improve the sealing effect of the lower gas storage chamber, the pressure relief hole is a stepped through hole, and the blocking piece is blocked in the pressure relief hole by an O-shaped sealing ring.

[0034] As a preferred, the ground injection equipment is a ground fracturing vehicle.

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

[0036] The method comprises the following steps: drilling a plurality of horizontal branch wells along the length direction of the horizontal well to construct a fishbone well, which significantly increases the effective contact area between the wellbore and the reservoir, and is beneficial to improve the subsequent fracturing effect; dividing the determined fracturing well section into a plurality of target branch well sections, which can facilitate the use of multi-stage segmented combustion fracturing operation to strengthen the fracture forming effect of the reservoir; drilling a drillable bridge plug into the primary target branch well section and setting the bridge plug, which can facilitate the joint action of the bridge plug and a packer set in the last target branch well section to form an effective seal of the fracturing well section, thereby being beneficial to improve the subsequent combustion effect; pre-vacuumizing the combustion chamber, and installing an electromagnetic valve in the lower gas outlet hole at the bottom of the combustion 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 combustion chamber through the negative pressure effect; pre-filling the delivery chamber with combustion-supporting agent, and installing a pressure regulating valve in the upper gas outlet hole at the bottom of the delivery chamber, which can facilitate the use of high-pressure nitrogen gas to act on the piston, so that the combustion-supporting agent can be rapidly injected into the delivery chamber through the pressure regulating valve, and the combustion-supporting agent can be rapidly mixed with the methane gas in the combustion chamber, thereby realizing the in-situ production process of the combustion fracturing bomb in the fracturing well section; this method not only effectively ensures the sufficient mixing of the combustion-supporting agent and the methane gas, ensures the mixing efficiency of the combustion-supporting agent and the methane gas, and is beneficial to improve the subsequent combustion effect, but also avoids the safety risks in the ground mixing and transportation process, and greatly improves the safety factor of the operation.

[0037] The method aims to realize in-situ production of the combustion fracturing bomb and multi-stage segmented targeted fracturing of the methane-enriched reservoir, utilizes the negative pressure bomb magazine to gather the methane gas, adopts the combustion-supporting agent pre-charging and delivery to complete the mixing of the combustion-supporting agent and the methane gas in the combustion fracturing bomb, and then realizes the in-situ production of the combustion fracturing bomb, so that the risk in the production process of the fracturing bomb can be effectively reduced, and the safety hidden danger in the transportation and operation process of the traditional premixed fracturing bomb can be solved. Meanwhile, the method realizes the multi-stage segmented combustion fracturing operation of the fracturing well section through the separate arrangement of the combustion fracturing bombs along the well section, and strengthens the fracture forming effect of the reservoir. The whole fracturing process of the method is carried out in the well, so that the safety risk caused by the ground operation can be avoided, and meanwhile, the damage to the wellbore and the reservoir can be effectively reduced through the accurate control of the delivery amount of the combustion-supporting agent and the combustion time. Compared with the traditional hydraulic fracturing technology, the method does not need to consume a large amount of water resources and fracturing fluid, and also does not need large-scale fracturing equipment and a large amount of water resources, so that the water resource pollution and the damage to the ground ecology are reduced, and the fracturing cost is also reduced. Meanwhile, the method utilizes the in-situ desorbed methane gas in the reservoir as fuel, so that the carbon emission and the environmental pollution degree are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a well layout schematic diagram of the fishbone well in the application;

[0039] Figure 2 is a state schematic diagram of the main body of the coiled tubing drop tool in the application;

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

[0041] Figure 4 is a cross-sectional view of the combustion bin in the application;

[0042] Figure 5 is an assembly schematic diagram of the delivery bin and the combustion bin through the electric control connecting buckle in the application;

[0043] Figure 6 is a state schematic diagram of the negative pressure acting on the combustion bin in the application;

[0044] Figure 7 is a combustion-supporting agent delivery and mixing state schematic diagram in the application;

[0045] Figure 8 is a combustion bin separation and arrangement schematic diagram in the application;

[0046] Figure 9 is a terminal tool packer and ignition schematic diagram in the application.

[0047] In the diagram: 1. Main wellbore, 2. Horizontal well, 3. Fishbone well, 4. Target fracturing reservoir, 5. Drillable bridge plug, 6. Tool body, 7. Coiled tubing, 8. Drop chamber, 9. Explosion chamber, 10. Piston, 11. Upper gas storage chamber, 12. Pressure regulating valve, 13. Check valve, 14. Plug, 15. Ignition electrode, 16. Solenoid valve, 17. Electrically controlled connector, 18. Cable, 19. Fracturing section, 20. Methane, 21. High-pressure nitrogen, 22. Combustion accelerant, 23. Combustion accelerant-methane mixture, 24. Packer, 25. Inlet pipeline, 26. Drop chamber, 27. Explosion chamber, 28. Horizontal branch well, 29. Gas outlet connector, 30. Lower gas storage chamber, 31. Inlet connector. Detailed Implementation

[0048] To achieve multi-stage, segmented fracturing and enhanced fracturing effect in methane-rich reservoirs, this invention provides a multi-stage pulse-targeted segmented fracturing method. This method employs pre-charging of the oxidizer and in-situ fabrication of the detonating fracturing bomb to mix the oxidizer and methane gas in the fracturing section. By separately arranging the detonating fracturing bombs along the well section, multi-stage, segmented detonating fracturing operations are achieved. The radially targeted impact flames generated by the detonating fracturing bombs and the pulsating shock waves generated by the sympathetic detonation along the well section act on the reservoir, forming a radial volumetric fracture cluster, significantly enhancing the reservoir fracturing effect.

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

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

[0051] Step 1: Preparation;

[0052] like Figure 1 As shown, the well network is arranged according to the determined well locations and the fracturing well section 19, so that the main wellbore 1 is set vertically and its end extends to a position close to the bottom of the target fracturing reservoir 4. At the same time, the horizontal well 2, which is 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: Secondary modification of horizontal well 2 involves drilling multiple horizontal branch wells 28 connected to horizontal well 2 at different locations along its length. The axes of these branch wells 28 and horizontal well 2 are aligned with the plane of horizontal well 2, creating a fishbone-like distribution of horizontal well 2 and the branch wells 28, thus forming fishbone well 3. Figure 1 As shown;

[0055] S22: After all the construction well groups are drilled, the fracturing well section in the fishbone well 3 is determined, and the fracturing well section is divided into multiple target branch well sections by multiple stages;

[0056] Step three: lower the bridge plug;

[0057] Lower the drillable bridge plug 5 in the primary target branch well section and make it set;

[0058] Step four: lower the combustion fracturing tool;

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

[0060] For the tool body 6, as shown in Figure 3 , the tool body 6 includes a delivery bin 8, a combustion bin 9 and an electric control connecting buckle 17, the delivery bin 8 includes a delivery bin body 26 and a piston 10, the delivery bin body 26 is cylindrical, an upper gas storage chamber 11 is formed inside, an upper gas inlet hole is opened in the center area of the top plate, an air inlet pipeline 25 is connected outside the upper gas inlet hole, a gas outlet hole is opened in the center of the bottom plate, a gas outlet connecting joint 29 is connected outside the gas outlet hole, and a constant pressure valve 12 is installed in the gas outlet hole, the constant pressure valve 12 opens the gas outlet hole when the pressure in the upper gas storage chamber 11 reaches the starting pressure, so that the combustion-supporting agent 22 can be smoothly discharged; the piston 10 is slidingly and sealingly assembled in the inside of the delivery bin body 26, can slide axially in the upper gas storage chamber 11, and sealingly cooperates with the inside wall of the delivery bin 8, after the coiled tubing 7 is connected on the air inlet pipeline 25, the gas in the coiled tubing 7 can directly act on the upper surface of the piston 10, and then the piston 10 can be driven by the gas in the coiled tubing 7 to move on the shaft; the upper gas storage chamber 11 is used for storing the combustion-supporting agent;

[0061] As shown in Figure 4As shown, the combustion chamber 9 includes a combustion chamber body 27 and an ignition electrode 15; the combustion chamber body 27 is cylindrical, and a lower gas storage cavity 30 is formed inside the combustion chamber body 27, a lower gas inlet hole is formed in the central area of the top plate of the combustion chamber body 27, and a gas inlet connecting joint 31 is connected outside the lower gas inlet hole, at the same time, a one-way valve 13 is installed in the lower gas inlet hole, a lower gas outlet hole is formed in the center of the bottom of the combustion chamber body 27, and a solenoid valve 16 is installed in the lower gas outlet hole; the one-way valve 13 is arranged to ensure that external gas can only flow into the lower gas storage cavity 30 through the one-way valve 13, and gas in the lower gas storage cavity 30 cannot flow out through the one-way valve 13; the solenoid valve 16 is used to communicate the lower gas storage cavity 30 and the wellbore annulus after being opened, and to maintain the sealing state of the lower gas storage cavity 30 after being closed; a plurality of pressure relief holes are uniformly formed in the circumference of the combustion chamber body 27, and a blocking piece 14 is installed in each pressure relief hole; the ignition electrode 15 is installed on the bottom plate of the combustion chamber body 27; the plurality of pressure relief holes serve as the main output channel for the shock wave flame during combustion.

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

[0063] S42: connecting the tail end of the coiled tubing 7 with the gas inlet pipeline 25 on the tool body 6, and connecting the head end of the coiled tubing 7 with the ground injection device; at the same time, connecting the ground control device with the ground injection device;

[0064] S43: filling the required amount of combustion-supporting agent 22 into the launching chamber body 26 on the ground using the injection device, and at the same time, performing vacuumizing treatment on the combustion chamber body 27 using the vacuumizing device;

[0065] S44: lowering the tool body 6 to the target well section using the coiled tubing 7, as shown in Figure 2

[0066] Step five: filling methane 20 into the combustion chamber body 27;

[0067] Opening the lower gas outlet hole at the bottom of the combustion chamber body 27 by controlling the solenoid valve 16 through the ground control device, and using the action of negative pressure to make the methane 20 in the annulus of the fracturing well section 19 enter the lower gas storage cavity 30 through the lower gas outlet hole, as shown in Figure 6

[0068] ​​Step six: combustion-supporting agent 22 injection and in-situ production of the detonation fracturing bomb;

[0069] The high-pressure nitrogen gas 21 is pumped into the coiled tubing 7 through the ground injection equipment, and the pressure of the gas in the coiled tubing 7 is continuously increased by the continuous injection of the high-pressure nitrogen gas 21, the piston 10 is driven downward by the gas pressure, and the combustion-supporting agent 22 in the upper chamber 11 is squeezed, so that the pressure of the gas in the upper chamber 11 is continuously increased. When the pressure of the gas in the upper chamber 11 reaches the opening threshold of the constant pressure valve 12, the constant pressure valve 12 opens the upper gas outlet hole at the bottom of the injection chamber 26, and the combustion-supporting agent 22 is injected through the open upper gas outlet hole and quickly enters the detonation chamber 27 to mix with the methane 20 to form the combustion-supporting agent-methane mixed gas 23, thereby completing the in-situ production process of the detonation fracturing bomb, as shown in Figure 7 ;

[0070] Step seven: separation of the detonation chamber;

[0071] The action of the electrically controlled connection buckle 17 is controlled by the ground control equipment to unlock the connection state between the gas inlet connection joint 31 and the gas outlet connection joint 29, so as to separate the detonation chamber 9 from the injection chamber 8, as shown in Figure 8 ;

[0072] Step eight: multi-segment arrangement of the detonation chamber;

[0073] For the remaining target well segments, steps four to seven are repeatedly executed in sequence to complete the segmented arrangement of the detonation fracturing bomb along the fracturing well segment 19. For the tool arrangement of the last target well segment, the packer 24 is installed outside the end of the coiled tubing 7 when step four is executed, and the electromagnetic valve 16 and the ignition electrode 15 are respectively connected to the ground control equipment through the cable 18. After step six is completed, steps seven and eight are skipped and step nine is directly executed.

[0074] Step nine: setting of the packer 24 and ignition operation for the fracturing well segment 19;

[0075] S91: The packer 24 is inflated and set in the primary target branch well segment by pressurizing the coiled tubing 7, and a closed detonation fracturing well segment is formed between the set packer 24 and the drillable bridge plug 15, as shown in Figure 9 ;

[0076] S92: Ignition operation is performed by using the ground control device to control the ignition electrode 15 through the cable 8, so as to ignite the combustible-methane mixed gas 23 in the detonation fracturing bomb, and the transmission process from outside to inside along the wellbore is completed by the way of sympathetic detonation. In this process, the gas produced by the detonation of each level of detonation fracturing bomb burst breaks through the blocking piece 14 in the pressure relief hole and rapidly expands to the wellbore, and the generated flame and shock wave act on the reservoir to form a radial volumetric fracture group; part of the shock wave reflects multiple times in the detonation bomb body 27, and the multiple pulse effect is generated after random strengthening and weakening, which, combined with the pulsed shock wave along the well section generated by the ordered sympathetic detonation of the multi-section detonation fracturing bomb, greatly strengthens the fracture effect on the reservoir, and thus the fracturing operation on the fracturing section 19 is realized.

[0077] As a preferred, in step one, the well location and the fracturing section 19 are determined according to the logging data, and the fracturing section 19 is divided into multiple target sections.

[0078] As a preferred, the outer diameter of the delivery bomb body 26 is 100 mm, and the height thereof is 1100 mm; the outer diameter of the detonation bomb 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 stepped through hole, and the blocking piece 14 is sealed in the pressure relief hole by an O-shaped sealing 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 detonation bomb body 27, the large-diameter hole is away from the outer surface of the detonation bomb body 27, the size of the blocking piece 14 is matched with the size of the large-diameter hole, and the blocking piece 14 is assembled at the outer end of the large-diameter hole, and the O-shaped sealing ring is sleeved on the outer edge surface of the blocking piece 14, so as to realize the sealed connection between the blocking piece 14 and the large-diameter hole.

[0080] As a preferred, the ground injection device 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 constructs a fishbone well by drilling multiple horizontal branch wells along the length direction of the horizontal well, significantly increases the effective contact area of the wellbore and the reservoir, and is beneficial to improve the subsequent fracturing effect; by dividing the determined fracturing well section into multiple target branch well sections, the fracture forming effect of the reservoir can be improved through multi-stage segmented combustion and explosion fracturing operation. The drillable bridge plug is lowered into the primary target branch well section and is set, which can facilitate the co-action with the packer set in the last target branch well section to form an effective seal of the fracturing well section, thereby being beneficial to improve the subsequent combustion and explosion effect. The explosion chamber is pre-vacuumized, and the electromagnetic valve is installed in the lower gas outlet hole 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 effect. Combustion-supporting agent is pre-filled in the launching chamber, and a pressure regulating valve is installed in the upper gas outlet hole at the bottom of the launching chamber, which can facilitate the use of high-pressure nitrogen gas on the piston, and then the combustion-supporting agent can be rapidly injected into the launching chamber through the pressure regulating valve, so that the combustion-supporting agent can be rapidly mixed with the methane gas in the explosion chamber, 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 sufficient mixing of the combustion-supporting agent and the methane gas, ensures the mixing efficiency of the combustion-supporting agent and the methane gas, and is beneficial to improve the subsequent combustion and explosion effect, but also avoids the safety risk in the ground mixing and transportation process, greatly improves the safety factor of the operation. The electric control connection buckle is arranged at the connection between the gas inlet connection joint of the explosion chamber and the gas outlet connection joint of the launching chamber, which can conveniently realize the separation and multi-section arrangement operation of the combustion and explosion fracturing bomb chamber, and then the combustion and explosion 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 can be completed by the last stage tool through the multi-stage arranged combustion and explosion fracturing bomb, the multi-section simultaneous or sequential detonation can be realized, which is beneficial to form a complex fracture network, can significantly improve the permeability and recovery of the reservoir, and is beneficial to increase the oil and gas production and improve the economic benefit.

[0083] The method aims to realize in-situ production of combustion fracturing bomb and multi-stage segmented targeted fracturing of methane-enriched reservoir. The method uses negative pressure bomb magazine to gather methane gas, uses combustion-supporting agent to pre-charge and drop to complete the mixing of combustion-supporting agent and methane gas in the combustion fracturing bomb, and then realizes in-situ production of combustion fracturing bomb, which can effectively reduce the risk of fracturing bomb production process and solve the safety hidden danger in the transportation and operation process of traditional premixed fracturing bomb. At the same time, the method realizes multi-stage segmented combustion fracturing operation of the fracturing well section through the separate arrangement of combustion fracturing bombs along the well section, which strengthens the fracture-making effect of the reservoir. The whole fracturing process of the method is carried out in the well, which avoids the safety risk brought by ground operation, and at the same time, can effectively reduce the damage to the wellbore and reservoir by accurately controlling the amount of combustion-supporting agent and the combustion time. Compared with the traditional hydraulic fracturing technology, the method does not need to consume a large amount of water resources and fracturing fluid, nor does it need large fracturing equipment and a large amount of water resources, which not only reduces the pollution of water resources and the damage to the ground ecology, but also reduces the cost of fracturing. At the same time, the method uses the in-situ desorbed methane gas in the reservoir as fuel, which reduces carbon emissions and environmental pollution.

Claims

1. A multi-stage pulse targeted fracturing method, characterized in that, Comprising the following steps: Step one: preparation work; According to the determined well pattern layout and the fracturing well section (19), the main wellbore (1) is vertically arranged and its end is extended to a position close to the bottom of the target fracturing reservoir (4), and the horizontal well (2) communicated with the end of the main wellbore (1) passes through the target fracturing reservoir (4); Step two: build fishbone well (3); S21: secondary reconstruction of horizontal well (2), drill multiple horizontal branch wells (28) communicated with horizontal well (2) at different positions along the length direction of horizontal well (2), and make the axis of multiple horizontal branch wells (28) and horizontal well (2) located in the same plane, so that horizontal well (2) and multiple horizontal branch wells (28) are distributed in fishbone shape as a whole, thereby forming fishbone well (3); S22: after all the well groups are drilled, determine the fracturing well section (19) in fishbone well (3), and then divide the fracturing well section (19) into multiple target branch well sections; Step three: lower bridge plug; Lower the drillable bridge plug (5) in the primary target branch well section and make it set and seal; Step four: lower the combustion fracturing tool; S41: prepare tool body (6), coiled tubing (7), ground injection equipment and ground control equipment; The tool body (6) comprises a delivery chamber (8), an explosion chamber (9) and an electric control connecting 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 gas storage chamber (11) is formed in the delivery chamber body (26). An upper gas inlet hole is formed in the center of the top plate of the delivery chamber body (26), and an air inlet pipeline (25) is connected to the outside of the upper gas inlet hole. An upper gas outlet hole is formed in the center of the bottom plate of the delivery chamber body (26), and a gas outlet connecting joint (29) is connected to the outside of the upper gas outlet hole. A pressure regulating valve (12) is installed in the upper gas outlet hole. The piston (10) is slidably and sealingly arranged in the delivery chamber body (26). The explosion chamber (9) comprises an explosion chamber body (27) and an ignition electrode (15). The explosion chamber body (27) is cylindrical, and a lower gas storage chamber (30) is formed in the explosion chamber body (27). A lower gas inlet hole is formed in the center of the top plate of the explosion chamber body (27), and a gas inlet connecting joint (31) is connected to the outside of the lower gas inlet hole. A one-way valve (13) is installed in the lower gas inlet hole. A lower gas outlet hole is formed in the center of the bottom plate of the explosion chamber body (27), and an electromagnetic valve (16) is installed in the lower gas outlet hole. A plurality of pressure relief holes are uniformly formed in the circumference of the explosion chamber body (27), and a baffle (14) is installed in each pressure relief hole. The ignition electrode (15) is installed on the bottom plate of the explosion chamber body (27). The explosion chamber body (27) is connected to the delivery chamber body (26) through the gas inlet connecting joint (31) and the gas outlet connecting joint (29). The electric control connecting buckle (17) is installed at the connection between the gas inlet connecting joint (31) and the gas outlet connecting joint (29). The electric control connecting buckle (17) is used to lock the connection state between the gas inlet connecting joint (31) and the gas outlet connecting joint (29), and to unlock the connection state between the gas inlet connecting joint (31) and the gas outlet connecting joint (29) under the control of the ground control equipment. The electric control connecting buckle (17) is connected to the ground control equipment through a cable (18). S42: The end of the coiled tubing (7) is connected to the air inlet pipeline (25) of the tool body (6), and the other end of the coiled tubing (7) is connected to the ground injection equipment. At the same time, the ground control equipment is connected to the ground injection equipment. S43: The required amount of combustion-supporting agent (22) is filled into the delivery chamber body (26) on the ground using the injection equipment, and the explosion chamber body (27) is vacuumized using a vacuumizing device. S44: The tool body (6) is lowered to the target well section by the coiled tubing (7). Step five: The methane (20) is filled into the explosion chamber body (27). The electromagnetic valve (16) is controlled by the ground control equipment to open the lower gas outlet hole at the bottom of the explosion chamber body (27). The methane (20) in the annulus of the fractured well section (19) enters the lower gas storage chamber (30) through the lower gas outlet hole under the action of negative pressure. After the pressure in the explosion chamber (9) is balanced, the electromagnetic valve (16) is controlled to be closed. Step six: The combustion-supporting agent (22) is delivered, and the in-situ production of the explosion and fracturing bomb is performed. By pumping high-pressure nitrogen (21) into the coiled tubing (7) through the ground injection device, the pressure of the gas in the coiled tubing (7) is continuously increased by the continuous injection of high-pressure nitrogen (21), the piston (10) is driven downward by the gas pressure and squeezes the combustion-supporting agent (22) in the upper gas storage chamber (11), so that the pressure of the gas in the upper gas storage chamber (11) is continuously increased, when the pressure of the gas in the upper gas storage chamber (11) reaches the opening threshold of the constant pressure valve (12), the constant pressure valve (12) opens the upper gas outlet hole at the bottom of the delivery compartment (26), the combustion-supporting agent (22) is sprayed out through the open upper gas outlet hole and quickly enters the combustion explosion compartment (27) to mix with the methane (20) to form a combustion-supporting agent-methane mixed gas (23), thereby completing the in-situ production process of the combustion and explosion fracturing bomb. Step seven: combustion explosion compartment separation; By controlling the action of the electric control connection buckle (17) through the ground control device, the connection state between the gas inlet connection joint (31) and the gas outlet connection joint (29) is unlocked, and the separation of the combustion explosion compartment (9) and the delivery compartment (8) is realized. Step eight: multi-section arrangement of combustion explosion compartment; For the remaining target well sections, steps four to seven are repeated in sequence to complete the segmented arrangement of the combustion and explosion fracturing bomb along the fracturing well section (19), wherein for the tool arrangement of the last target well section, the packer (24) is installed outside the end of the coiled tubing (7) when step four is performed, and the electromagnetic valve (16) and the ignition electrode (15) are respectively connected to the ground control device through the cable (18), after step six is completed, steps seven and eight are skipped and step nine is directly performed. Step nine: set the packer (24) and perform the ignition operation on the fracturing well section (19); S91: inflate the packer (24) and set it in the primary target branch well section by means of the coiled tubing (7) pressure, and form a sealed combustion and explosion fracturing well section between the set packer (24) and the drillable bridge plug (5); S92: use the ground control device to control the ignition electrode (15) through the cable (18) to perform the ignition operation, to detonate the combustion-supporting agent-methane mixed gas (23) in the combustion and explosion fracturing bomb, and complete the self-outer-to-inner transmission process along the wellbore by means of sympathetic detonation, in this process, the gas produced by the explosion of each level of combustion and explosion fracturing bomb bursts through the blocking piece (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 volumetric fracture group; part of the shock wave reflects multiple times in the combustion explosion compartment (27), and after random strengthening and weakening, it produces a multi-pulse effect, combined with the pulsating shock wave along the well section produced by the ordered sympathetic detonation of the multi-section combustion and explosion fracturing bomb, the fracturing effect on the reservoir is strengthened, and then the fracturing operation on the fracturing well section is realized.

2. A multi-stage pulse targeted segmented fracturing method according to claim 1, characterized in that, In step one, the well arrangement position and the fracturing well section (19) are determined according to the logging data, and the fracturing well section (19) is divided into multiple target well sections.

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

4. The method of claim 3, wherein, The pressure relief hole is a stepped through hole, and the blocking piece (14) is blocked in the pressure relief hole by an O-shaped sealing ring.

5. The method of claim 1, wherein, The ground injection device is a ground fracturing truck.

6. The method of claim 1, wherein, The thickness of the piston (10) is 20 cm.

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