Downhole energy-gathered fracturing sliding sleeve and CO2 impact composite fracturing method

Abstract

The invention relates to the field of petroleum and natural gas underground fracturing construction, and discloses an underground energy-gathered fracturing sliding sleeve and a CO2 impact composite fracturing method. The underground energy-gathering fracturing sliding sleeve comprises a sliding sleeve outer cylinder provided with a first limiting step (21) and a second limiting step (31), a sliding sleeve mandrel (4) installed in the sliding sleeve outer cylinder in a reciprocating sliding mode and a reset spring (5) elastically abutting against the sliding sleeve mandrel (4), and the sliding sleeve mandrel (4) defines an energy-gathering cavity (6) in the sliding sleeve outer cylinder. When the pressure in the energy gathering cavity (6) reaches a preset value, the sliding sleeve mandrel (4) can overcome the elastic force of the reset spring (5) to slide so that the inner through hole (41) of the sliding sleeve mandrel (4) can be communicated with the outer through hole (32) of the sliding sleeve outer cylinder. According to the underground energy-gathered fracturing sliding sleeve, multiple times of energy-gathered fracturing operation can be conducted on a target reservoir stratum without ball throwing, the opening and closing state of a jetting channel can be accurately controlled conveniently, and the underground energy-gathered fracturing sliding sleeve has the advantages of being practical, high in reliability and the like.

Description

Technical Field

[0001] The present invention relates to a downhole fracturing tool for oil and natural gas, and in particular to a downhole energy-concentrated fracturing sleeve. In addition, the present invention also relates to a CO2 impact composite fracturing method. Background Art

[0002] In traditional technology, unconventional oil and gas development usually adopts hydraulic fracturing operations, that is, artificially injecting water-based fracturing fluid carrying proppants to induce the generation, expansion and support of cracks to maintain high conductivity channels, so that oil and gas can flow smoothly through the cracks into the well to achieve the purpose of increasing production and efficiency. However, this operation method is weak in the ability to generate complex fractures in the fracturing formation, and the fractures generated are mostly single main fractures perpendicular to the direction of the minimum horizontal principal stress.

[0003] In recent years, the rapid development of waterless fracturing technology is expected to promote the efficient development of unconventional oil and gas. Among them, CO2 fracturing has many advantages such as low fracturing pressure, easy formation of complex fractures, no reservoir damage, and realization of CO2 geological storage, but there are problems such as poor sand carrying capacity and narrow fracture width. In addition, the bedrock of unconventional oil and gas reservoirs is very dense, mainly micro-nano pores. For some well-developed natural fractures of micron to millimeter scale, the commonly used large-sized fracturing proppants such as 20 / 40 and 40 / 70 mesh natural quartz sand, artificial ceramsite, and resin-coated sand are difficult to enter the micro fractures in deep formations, resulting in the transport distance of the proppant being far lower than the response distance of the fracturing fluid, affecting the fracturing effect.

[0004] In the process of implementing CO2 impact fracturing, CO2 fracturing fluid is injected into the fracturing string to perform physical pressurization in the downhole energy-gathering tool. When the pressure in the fracturing string exceeds the engineering design pressure, the discharge channel of the energy-gathering tool automatically opens to generate a high-pressure CO2 controllable shock wave, and the target reservoir is efficiently fractured and transformed to achieve a better production increase effect than conventional fracturing methods. At present, the CO2 impact fracturing process usually requires a seal to be formed by throwing a ball into the pressure string, and then pumping in CO2 fracturing fluid for fracturing operations. For example, Chinese invention patent application CN109138959A discloses a supercritical CO2 energy-gathering fracturing method, which is provided with multiple fracturing sections in the string body, and each fracturing section is respectively installed with a fracturing unit, and each fracturing unit includes a sleeve, a metal ball and a pin, and the sleeve is fixedly connected to the side wall of the fracturing section by the pin. By dropping a metal ball into the fracturing string, the metal ball is seated on the ball seat of the sleeve so that the CO2 fracturing fluid is injected to continuously pressurize the pipe until the corresponding pin is cut off. The sleeve slides downward to open the injection hole of the fracturing section, thereby allowing the CO2 fracturing fluid to enter and fracture the target reservoir through the injection hole. By using metal balls with different diameters and sleeves with different inner diameters, multiple repeated energy-gathering fracturing operations can be performed on the same layer. Since it is necessary to form a seal by dropping a ball into the pressure string multiple times, the fracturing operation process is cumbersome and the fracturing tools are complicated.

[0005] In this regard, Chinese invention patent application CN111911125A provides a focused energy fracturing tool that can perform multiple focused energy fracturing operations on a target reservoir without the need for throwing a ball, effectively simplifying the fracturing operation process. Figure 1The figure shows the energy-concentrating fracturing tool provided by the patent application, which has a shell 1' formed with a cavity 11', a seal 2' and a first elastic member 3' arranged in the cavity 11', a groove 12' is arranged on the inner wall of the shell 1', and the seal 2' has a pin 5' that cooperates with the groove 12' under the thrust of the second elastic member 4'. When the pressure in the cavity 11' increases to a predetermined value, the pin 5' is cut off, the seal 2' moves downward relative to the shell 1' and compresses the first elastic member 3', the injection channel on the shell 1' is opened, and the pressure medium in the cavity 11' is discharged to the target reservoir; when the pressure in the cavity 11' is released, the first elastic member 3' pushes the seal 2' upward until the pin 5' is pushed out by the second elastic member 4' to cooperate with the groove 12' again. In this way, the energy-concentrating fracturing tool can be used to perform multiple energy-concentrating fracturing operations on the target reservoir. However, since the pin 5' needs to be cut off and reset multiple times to match the groove 12', the tip of the pin 5' is easily left in the groove 12' after being cut off, resulting in the pin 5' being unable to match the groove 12' again. In addition, it is necessary to match the groove 12' under the thrust of the second elastic member 4'. The thrust of the second elastic member 4' needs to be strictly controlled during the above-mentioned energy-concentrating fracturing process to ensure that the pin 5' can be pushed by the second elastic member 4' to match the groove 12' during the upward movement of the seal 2', and to avoid the first elastic member 3' being unable to push the seal 2' upward due to the friction between the pin 5' and the inner wall of the shell 1'. Therefore, the reliability of the energy-concentrating fracturing tool is low and it is difficult to be applied in actual production. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem that the prior art shaped energy fracturing tools have low reliability and are difficult to be applied in actual production, and to provide a downhole shaped energy fracturing sleeve. The downhole shaped energy fracturing sleeve can perform multiple shaped energy fracturing operations on the target reservoir without throwing a ball, effectively simplifying the fracturing operation process, and has the advantages of being suitable for practical use and high reliability.

[0007] In order to achieve the above-mentioned object, the present invention provides a downhole energy-focused fracturing sleeve, comprising:

[0008] The sliding sleeve outer cylinder has a first limiting step and a second limiting step which are arranged on the inner periphery of the cylinder wall and are axially spaced and opposite to each other, and an outer through hole formed in a portion of the cylinder wall between the first limiting step and the second limiting step;

[0009] A sliding sleeve spindle, which is reciprocatingly slidably mounted in the inner cavity of the sliding sleeve outer cylinder and defines an energy-gathering cavity in the inner cavity, and the sliding sleeve spindle is formed with an inner through hole communicating with the energy-gathering cavity; and,

[0010] A return spring elastically abuts against the sleeve spindle so that the sleeve spindle tends to remain in the first sliding position defined by the first limiting step and the inner through hole is isolated from the outer through hole; when the pressure in the energy gathering chamber reaches a predetermined value, the sleeve spindle can overcome the elastic force of the return spring and slide from the first sliding position to the second sliding position defined by the second limiting step and the inner through hole is connected to the outer through hole.

[0011] Preferably, the sliding sleeve outer cylinder includes an outer cylinder body and an upper joint screwed to the outer cylinder body, one end of the upper joint screwed to the outer cylinder body forms the first limiting step, and when the sliding sleeve core shaft is located at the first sliding position, the sliding sleeve core shaft abuts against the upper joint.

[0012] Preferably, along the direction toward the sliding sleeve axis, the inner diameter of a portion of the upper joint close to the sliding sleeve axis gradually decreases.

[0013] Preferably, a sealing ring is provided between the upper joint and the outer cylinder body and / or between the sliding sleeve spindle and the outer cylinder body.

[0014] Preferably, a coupling is threadedly connected to one end of the upper joint away from the outer cylinder body.

[0015] Preferably, when the sleeve spindle is located at the first sliding position, one end of the sleeve spindle close to the energy gathering chamber abuts against the first limit step; a third limit step is formed on the outer peripheral wall of the sleeve spindle, and when the sleeve spindle is located at the second sliding position, the third limit step abuts against the second limit step.

[0016] Preferably, between the second limiting step and the third limiting step, the outer circumferential wall of the sliding sleeve spindle and the inner circumferential wall of the sliding sleeve outer tube are spaced apart to form a spindle cavity.

[0017] Preferably, a drainage hole communicating with the bottom end of the spindle cavity is formed on the wall of the outer sleeve tube.

[0018] Preferably, a first spring seat is formed on the outer peripheral wall of the sliding sleeve shaft, a second spring seat axially spaced opposite to the first spring seat is formed on the inner peripheral wall of the sleeve outer cylinder, and the return spring is a coil spring which is sleeved on the outer peripheral of the sliding sleeve shaft and abuts against the first spring seat and the second spring seat at both ends respectively.

[0019] The second aspect of the present invention provides a CO2 impact composite fracturing method, comprising the following steps:

[0020] S1. Connecting the downhole energy-focused fracturing sleeve to the oil pipe, and anchoring the downhole energy-focused fracturing sleeve after moving it to the reservoir perforation section;

[0021] S2. Pumping liquid CO2 fracturing fluid carrying micro-nano proppants into the oil pipe on the ground, so that the pressure in the energy-gathering chamber increases, thereby causing the sliding sleeve mandrel to overcome the elastic force of the return spring and slide from the first sliding position to the second sliding position, and causing the inner through hole to communicate with the outer through hole, using the liquid CO2 fracturing fluid to impact and fracture the target reservoir, and transporting the micro-nano proppants into the reservoir cracks;

[0022] S3. After the pressure in the energy-gathering chamber is released through the inner through hole and the outer through hole, the sliding sleeve spindle is reset to the first sliding position under the action of the reset spring until the inner through hole is separated from the outer through hole;

[0023] S4. Repeat steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir.

[0024] Preferably, step S4 comprises: releasing the anchoring of the oil pipe, dragging the oil pipe to the reservoir perforation section of the next layer, and repeating steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir of the next layer.

[0025] Preferably, the method further comprises step S5 implemented after step S4: replacing the hydraulic fracturing string and performing hydraulic fracturing operation.

[0026] Through the above technical scheme, when the downhole energy-gathering fracturing sleeve provided by the present invention moves and is anchored to the reservoir perforation section, the fracturing fluid can be pumped into the energy-gathering chamber through the oil pipe connected to the downhole energy-gathering fracturing sleeve on the ground, so that the pressure in the energy-gathering chamber increases until it reaches a predetermined value that can drive the sleeve mandrel to overcome the elastic force of the reset spring and slide from the first sliding position to the second sliding position. As a result, the inner through hole of the sleeve mandrel is connected to the outer through hole of the sleeve outer tube, and the fracturing fluid in the energy-gathering chamber can be discharged to the target reservoir through the injection channel formed by the inner through hole and the outer through hole to impact-fractured the target reservoir. After the pressure in the energy-gathering chamber is released, the sleeve mandrel is reset to the first sliding position under the action of the reset spring, the inner through hole and the outer through hole are separated, and the energy-gathering chamber is closed and can be pressurized again to perform multi-stage impact fracturing on the target reservoir. In the impact fracturing process, multiple energy-gathering fracturing operations can be performed on the target reservoir without throwing a ball into the pressure column, which effectively simplifies the fracturing operation process. At the same time, compared with the matching structure of the pin and the groove and the opening and closing method of the injection channel in the prior art, the downhole energy-gathering fracturing sleeve of the present invention utilizes the first limit step and the second limit step arranged on the inner circumference of the sleeve outer cylinder wall to limit the extreme sliding position of the sleeve core shaft in the process of opening and closing the injection channel, which is convenient for utilizing the reset spring and the pressure in the energy-gathering chamber to accurately control the opening and closing state of the injection channel, effectively simplifies the pipe column structure and the construction process, is suitable for application in actual production, and has high reliability.

[0027] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional view of a concentrated energy fracturing tool in the prior art;

[0029] Figure 2 is a cross-sectional view of a downhole energy-focused fracturing sleeve according to a preferred embodiment of the present invention;

[0030] Figure 3 The figure is a flow chart of a CO2 impact composite fracturing method according to a preferred embodiment of the present invention.

[0031] Description of Reference Numerals

[0032] 1-coupling; 2-upper joint; 21-first limiting step; 22-external thread; 3-outer cylinder body; 31-second limiting step; 32-external through hole; 33-drainage hole; 34-second spring seat; 4-sleeve spindle; 41-inner through hole; 42-third limiting step; 43-first spring seat; 5-reset spring; 6-energy-gathering chamber; 7-sealing ring; 8-spindle chamber. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0034] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to up, down, left, right as shown in the reference drawings; "inside and outside" refer to inside and outside relative to the outline of each component itself.

[0035] In view of the problems that large-sized fracturing proppants are difficult to enter micro-cracks in deep formations, and the existing CO2 impact fracturing method requires throwing balls into the fracturing string to form a seal, and the overall fracturing process is relatively cumbersome, the present invention provides a downhole energy-gathering fracturing sleeve, which can replace the ball-dropping seal to achieve downhole energy gathering by controlling the surface pumping program, improve the impact fracturing technical process to improve energy gathering reliability and operating efficiency, expand the scale of fracturing, and thus achieve the purpose of efficiently developing unconventional oil and gas.

[0036] Reference Figure 2As shown, according to a preferred embodiment of the present invention, a downhole energy-gathering fracturing sleeve comprises a sleeve outer tube, a sleeve mandrel 4 and a reset spring 5. The sleeve outer tube may be a cylindrical structure formed by connecting an upper joint 2 and an outer tube body 3 as described later, wherein the empty passage is formed as an inner cavity for installing the sleeve mandrel 4, and an energy-gathering cavity 6 can be defined by the sleeve mandrel 4. The inner circumference of the sleeve wall of the sleeve outer tube is provided with a first limiting step 21 and a second limiting step 31 which are axially spaced and opposite to each other, and the portion of the sleeve wall located between the first limiting step 21 and the second limiting step 31 is formed with an outer through hole 32 leading to the target reservoir, which is used to spray the fracturing fluid in the inner cavity (energy-gathering cavity 6) of the sleeve outer tube to the target reservoir to fractur the target reservoir.

[0037] The sleeve spindle 4 is installed in the inner cavity of the sleeve outer tube, which separates the inner cavity of the sleeve outer tube to define an energy-gathering chamber 6 in the inner cavity. By pumping fracturing fluid into the energy-gathering chamber 6, the pressure in the energy-gathering chamber 6 can be increased. The sleeve spindle 4 can slide back and forth in the inner cavity of the sleeve outer tube along the axial direction. Among them, the first limiting step 21 and the second limiting step 31 on the inner circumference of the sleeve outer tube wall respectively define the limit sliding position of the sleeve spindle 4: when the sleeve spindle 4 slides upward to abut against the first limiting step 21, the sleeve spindle 4 reaches its upper limit sliding position, which is referred to as the "first sliding position" here; when the sleeve spindle 4 slides downward to abut against the second limiting step 31, the sleeve spindle 4 reaches its lower limit sliding position, which is referred to as the "second sliding position" here.

[0038] An inner through hole 41 connected to the energy-gathering chamber 6 is formed on the side wall of the sleeve mandrel 4. When the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are axially offset from each other (such as the first sliding position), the radial outer end of the inner through hole 41 is closed by the inner wall surface of the sleeve outer tube, and the fracturing fluid pumped into the energy-gathering chamber 6 cannot be discharged, which will cause the pressure in the energy-gathering chamber 6 to increase; when the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are aligned with each other (such as the second sliding position), the inner through hole 41 is connected to the outer through hole 32 and forms an injection channel, and the fracturing fluid pumped into the energy-gathering chamber 6 is discharged to the target reservoir through the injection channel to impact-fracture the target reservoir.

[0039] The return spring 5 elastically abuts against the sleeve spindle 4 so that the sleeve spindle 4 tends to remain in the first sliding position defined by the first limit step 21, and the inner through hole 41 is separated from the outer through hole 32; when the pressure in the energy gathering chamber 6 reaches a predetermined value, the sleeve spindle 4 can overcome the elastic force of the return spring 5 and slide from the first sliding position to the second sliding position defined by the second limit step 31, and the inner through hole 41 is connected to the outer through hole 32.

[0040] Thus, after the downhole energy-focused fracturing sleeve moves and is anchored to the reservoir perforation section, fracturing fluid can be pumped into the energy-focused chamber 6 through the oil pipe connected to the downhole energy-focused fracturing sleeve on the ground, so that the pressure in the energy-focused chamber 6 increases until it reaches a predetermined value that can drive the sleeve mandrel 4 to overcome the elastic force of the return spring 5 and slide from the first sliding position to the second sliding position. Thus, the inner through hole 41 of the sleeve mandrel 4 is connected with the outer through hole 32 of the sleeve outer cylinder, and the fracturing fluid in the energy-focused chamber 6 can be discharged to the target reservoir through the injection channel formed by the inner through hole 41 and the outer through hole 32 to impact fracturing the target reservoir. After the pressure in the energy-focused chamber 6 is released, the sleeve mandrel 4 is reset to the first sliding position under the action of the return spring 5, the inner through hole 41 and the outer through hole 32 are isolated, and the energy-focused chamber 6 is closed and can be pressurized again, and so on and so forth, so as to perform multi-stage impact fracturing on the target reservoir.

[0041] In the impact fracturing process, the target reservoir can be subjected to multiple energy-concentrated fracturing operations without dropping a ball into the pressure string, which effectively simplifies the fracturing operation process. At the same time, compared with the matching structure of the pin and the groove and the opening and closing method of the injection channel in the prior art, the downhole energy-concentrated fracturing sleeve of the present invention uses the first limiting step 21 and the second limiting step 31 provided on the inner circumference of the sleeve outer cylinder wall to limit the limit sliding position of the sleeve mandrel 4 in the process of opening and closing the injection channel, which is convenient for using the reset spring 5 and the pressure in the energy-concentrated cavity 6 to accurately control the opening and closing state of the injection channel, effectively simplifying the pipe string structure and construction process, suitable for application in actual production, and has high reliability.

[0042] On this basis, the present invention also provides a CO2 impact composite fracturing method, combining Figure 3 As shown, the CO2 impact composite fracturing method comprises the following steps:

[0043] S1. Connecting the downhole energy-focused fracturing sleeve provided by the present invention to the oil pipe, and anchoring the downhole energy-focused fracturing sleeve after it moves to the reservoir perforation section;

[0044] S2. Pumping liquid CO2 fracturing fluid carrying micro-nano proppants into the oil pipe on the ground, so that the pressure in the energy-gathering cavity 6 of the downhole energy-gathering fracturing sleeve increases, thereby making the sleeve mandrel 4 overcome the elastic force of the return spring 5 and slide from the first sliding position to the second sliding position, and making the inner through hole 41 of the sleeve mandrel 4 communicate with the outer through hole 32 of the sleeve outer cylinder, using the liquid CO2 fracturing fluid to impact and fracture the target reservoir, and transporting the micro-nano proppants into the reservoir cracks;

[0045] S3. After the pressure in the energy-gathering chamber 6 is released through the inner through hole 41 and the outer through hole 32, the sliding sleeve spindle 4 is reset to the first sliding position under the action of the reset spring 5 until the inner through hole 41 is separated from the outer through hole 32;

[0046] S4. Repeat steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir.

[0047] Compared with the traditional ball-casting sealing method, the CO2 impact composite fracturing method can control the pressure difference imposed on the sleeve mandrel 4 by the energy-gathering chamber 6 and the return spring 5 by controlling the surface pumping program, thereby controlling the opening and closing of the downhole energy-gathering fracturing sleeve, thereby realizing single-layer multi-stage impact fracturing, greatly simplifying the pipe column structure, construction process and process action. By using the first limiting step 21 and the second limiting step 31 arranged on the inner circumference of the sleeve outer cylinder wall to limit the limit sliding position of the sleeve mandrel 4 in the process of opening and closing the injection channel, it is convenient to use the return spring 5 and the pressure in the energy-gathering chamber 6 to accurately control the opening and closing state of the injection channel, and has high reliability, so it is suitable for application in actual production. In addition, the CO2 impact composite fracturing method is implemented by pumping liquid CO2 fracturing fluid carrying micro-nano proppants into the oil pipe. Compared with large-size fracturing proppants such as natural quartz sand, artificial ceramsite, and resin-coated sand, it can effectively enter the micro-cracks of deep formations, thereby effectively expanding the scale of fracturing and realizing the efficient development of unconventional oil and gas.

[0048] Embodiment 1

[0049] Reference Figure 2 As shown, a downhole energy-gathering fracturing sleeve of a preferred embodiment of the present invention comprises a sleeve outer cylinder, a sleeve mandrel 4 and a reset spring 5. The sleeve outer cylinder is a cylindrical structure, wherein the hollow passage is formed as an inner cavity for installing the sleeve mandrel 4, and the energy-gathering cavity 6 can be defined by the sleeve mandrel 4. The inner circumference of the sleeve outer cylinder wall is provided with a first limiting step 21 and a second limiting step 31 axially spaced and opposite to each other, and the portion of the cylinder wall located between the first limiting step 21 and the second limiting step 31 is formed with an outer through hole 32 leading to the target reservoir, which is used to spray the fracturing fluid in the inner cavity (energy-gathering cavity 6) of the sleeve outer cylinder to the target reservoir to fractur the target reservoir.

[0050] The sleeve mandrel 4 is installed in the inner cavity of the sleeve outer cylinder, which separates the inner cavity of the sleeve outer cylinder to define an energy-gathering cavity 6 in the inner cavity. By pumping fracturing fluid into the energy-gathering cavity 6, the pressure in the energy-gathering cavity 6 can be increased. The sleeve mandrel 4 can slide back and forth in the inner cavity of the sleeve outer cylinder along the axial direction. The first limiting step 21 and the second limiting step 31 on the inner circumference of the sleeve outer cylinder wall respectively define the limit sliding positions of the sleeve mandrel 4, namely the first sliding position and the second sliding position.

[0051] An inner through hole 41 connected to the energy-gathering chamber 6 is formed on the side wall of the sleeve mandrel 4. When the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are axially offset from each other (such as the first sliding position), the radial outer end of the inner through hole 41 is closed by the inner wall surface of the sleeve outer tube, and the fracturing fluid pumped into the energy-gathering chamber 6 cannot be discharged, which will cause the pressure in the energy-gathering chamber 6 to increase; when the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are aligned with each other (such as the second sliding position), the inner through hole 41 is connected to the outer through hole 32 and forms an injection channel, and the fracturing fluid pumped into the energy-gathering chamber 6 is discharged to the target reservoir through the injection channel to impact-fracture the target reservoir. The sleeve core shaft 4 and the sleeve outer cylinder may be respectively formed with a plurality of inner through holes 41 and outer through holes 32 arranged in phase with each other, such as three groups of inner through holes 41 and outer through holes 32 uniformly distributed at a central angle of 120° along the circumferential direction.

[0052] The return spring 5 elastically abuts against the sleeve spindle 4 so that the sleeve spindle 4 tends to remain in the first sliding position defined by the first limit step 21, and the inner through hole 41 is separated from the outer through hole 32; when the pressure in the energy gathering chamber 6 reaches a predetermined value, the sleeve spindle 4 can overcome the elastic force of the return spring 5 and slide from the first sliding position to the second sliding position defined by the second limit step 31, and the inner through hole 41 is connected to the outer through hole 32.

[0053] In the downhole energy-concentrating fracturing sleeve, the sleeve outer sleeve includes an outer sleeve body 3 and an upper joint 2 screwed to the outer sleeve body 3, such as an outer thread 22 may be formed on the outer peripheral wall of the upper joint 2, and an inner thread for screwing with the outer thread 22 may be formed on the inner peripheral wall of the outer sleeve body 3. Thus, the upper joint 2 can be screwed to the outer sleeve body 3, and one end of the upper joint 2 extending into the outer sleeve body 3 is formed as a first limiting step 21. When the sleeve mandrel 4 is located at the first sliding position, the sleeve mandrel 4 abuts against the end surface of the upper joint 2. Through this arrangement, during assembly, the sleeve mandrel 4 (and the return spring 5) can be first loaded into the inner cavity of the outer sleeve body 3, and then the upper joint 2 is screwed to the outer sleeve body 3, and the sleeve mandrel 4 is squeezed by the first limiting step 21 formed by one end of the upper joint 2, thereby compressing the return spring 5, thereby conveniently completing the assembly of the downhole energy-concentrating fracturing sleeve.

[0054] In an alternative embodiment, the first limiting step 21 may be formed in other ways, for example, by installing a retaining spring on the inner circumferential wall of the sliding sleeve outer cylinder to limit the upper limit position of the sliding sleeve spindle 4 in the sliding sleeve outer cylinder.

[0055] In another alternative embodiment, the upper joint 2 may be fixedly or detachably connected to the outer cylinder body 3 in other ways. For example, mutually matching buckles and slots may be formed on the inner and outer peripheral walls of the upper joint 2 and the outer cylinder body 3, so as to snap the upper joint 2 to the outer cylinder body 3, and use the end of the upper joint 2 extending into the outer cylinder body 3 as the first limiting step 21 for limiting the upper limit position of the sliding sleeve spindle 4.

[0056] exist Figure 2 In the preferred embodiment shown, the upper joint 2 and the sleeve mandrel 4 have substantially the same inner diameter at the ends opposite to each other, and in the direction toward the sleeve mandrel 4, the inner diameter of the portion of the upper joint 2 close to the sleeve mandrel 4 gradually decreases. Thus, for example, liquid CO2 fracturing fluid carrying micro-nano proppants can be efficiently pumped into the energy-gathering chamber 6, and facilitates rapid energy gathering and pressure raising in the energy-gathering chamber 6, thereby improving the operation efficiency. In addition, at the end facing the sleeve mandrel 4, the upper joint 2 has a relatively large wall thickness, which is conducive to reliably stopping the sleeve mandrel 4 with its end face (first limit step 21), and is convenient for setting the reset spring 5 to have a relatively large elastic coefficient to form sufficient fracturing energy in the energy-gathering chamber 6.

[0057] In addition, a sealing ring 7 may be provided between the upper joint 2 and the outer tube body 3 and / or between the sliding sleeve core shaft 4 and the outer tube body 3, which is beneficial to ensure the sealing performance of the energy-gathering chamber 6, so that the fracturing fluid can effectively accumulate fracturing energy after being pumped into the energy-gathering chamber 6.

[0058] A coupling 1 may be threadedly connected to one end of the upper joint 2 away from the outer cylinder body 3 , so as to be connected to the oil pipe through the coupling 1 .

[0059] Embodiment 2

[0060] Reference Figure 2 As shown, a downhole energy-gathering fracturing sleeve of a preferred embodiment of the present invention comprises a sleeve outer cylinder, a sleeve mandrel 4 and a reset spring 5. The sleeve outer cylinder may be a cylindrical structure formed by connecting an upper joint 2 and an outer cylinder body 3, wherein the hollow passage is formed as an inner cavity for installing the sleeve mandrel 4, and an energy-gathering cavity 6 can be defined by the sleeve mandrel 4. The inner circumference of the sleeve wall of the sleeve outer cylinder is provided with a first limiting step 21 and a second limiting step 31 which are axially spaced and opposite to each other, and the portion of the sleeve wall located between the first limiting step 21 and the second limiting step 31 is formed with an outer through hole 32 leading to the target reservoir, which is used to spray the fracturing fluid in the inner cavity (energy-gathering cavity 6) of the sleeve outer cylinder to the target reservoir to fractur the target reservoir.

[0061] The sleeve mandrel 4 is installed in the inner cavity of the sleeve outer cylinder, which separates the inner cavity of the sleeve outer cylinder to define an energy-gathering cavity 6 in the inner cavity. By pumping fracturing fluid into the energy-gathering cavity 6, the pressure in the energy-gathering cavity 6 can be increased. The sleeve mandrel 4 can slide back and forth in the inner cavity of the sleeve outer cylinder along the axial direction. The first limiting step 21 and the second limiting step 31 on the inner circumference of the sleeve outer cylinder wall respectively define the limit sliding positions of the sleeve mandrel 4, namely the first sliding position and the second sliding position.

[0062] An inner through hole 41 connected to the energy-gathering chamber 6 is formed on the side wall of the sleeve mandrel 4. When the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are axially offset from each other (such as the first sliding position), the radial outer end of the inner through hole 41 is closed by the inner wall surface of the sleeve outer tube, and the fracturing fluid pumped into the energy-gathering chamber 6 cannot be discharged, which will cause the pressure in the energy-gathering chamber 6 to increase; when the sleeve mandrel 4 is located at a sliding position where the inner through hole 41 and the outer through hole 32 of the sleeve outer tube are aligned with each other (such as the second sliding position), the inner through hole 41 is connected to the outer through hole 32 and forms an injection channel, and the fracturing fluid pumped into the energy-gathering chamber 6 is discharged to the target reservoir through the injection channel to impact-fracture the target reservoir.

[0063] The return spring 5 elastically abuts against the sleeve spindle 4 so that the sleeve spindle 4 tends to remain in the first sliding position defined by the first limit step 21, and the inner through hole 41 is separated from the outer through hole 32; when the pressure in the energy gathering chamber 6 reaches a predetermined value, the sleeve spindle 4 can overcome the elastic force of the return spring 5 and slide from the first sliding position to the second sliding position defined by the second limit step 31, and the inner through hole 41 is connected to the outer through hole 32.

[0064] In the downhole energy-focused fracturing sliding sleeve, the sliding sleeve mandrel 4 can abut against the first limiting step 21 and the second limiting step 31 in an appropriate manner. For example, when there is no pressure or the pressure is relatively low in the energy gathering chamber 6, the sleeve spindle 4 is maintained in the first sliding position under the action of the reset spring 5, that is, its end (upper end) close to the energy gathering chamber 6 abuts against the first limit step 21, such as abutting against the lower end surface of the upper joint 2. At this time, the inner through hole 41 of the sleeve spindle 4 is separated from the outer through hole 32 of the outer cylinder body 3; when the pressure in the energy gathering chamber 6 reaches a predetermined value, the sleeve spindle 4 is driven to overcome the elastic force of the reset spring 5 and slide to the second sliding position, wherein a third limit step 42 is formed on the outer peripheral wall of the sleeve spindle 4, and the third limit step 42 is opposite to the second limit step 31 to allow the sleeve spindle 4 to slide until the third limit step 42 abuts against the second limit step 31. At this time, the inner through hole 41 of the sleeve spindle 4 is connected to the outer through hole 32 of the outer cylinder body 3. When the sleeve spindle 4 is located at the first sliding position, that is, when it abuts against the first limit step 21, the axial spacing between the third limit step 42 and the second limit step 31 can be equal to the axial spacing between the center lines of the inner through hole 41 and the outer through hole 32, so that when the sleeve spindle 4 slides to the second sliding position, that is, when it abuts against the second limit step 31, the inner through hole 41 of the sleeve spindle 4 is exactly aligned and connected with the outer through hole 32 of the outer cylinder body 3.

[0065] Furthermore, between the second limiting step 31 and the third limiting step 42, the outer peripheral wall of the sliding sleeve mandrel 4 is spaced from the inner peripheral wall of the sliding sleeve outer cylinder to form a mandrel cavity 8. Thus, the contact surface between the sliding sleeve mandrel 4 and the outer cylinder body 3 is relatively small, which can reduce the friction of the sliding sleeve mandrel 4 during the sliding process, thereby reducing wear and increasing the service life.

[0066] During use, formation water, residual drilling and completion fluid, etc. may enter the mandrel cavity 8 through the gap between the sleeve mandrel 4 and the sleeve outer tube. These incompressible fluids in the mandrel cavity 8 will prevent the sleeve mandrel 4 from sliding to the second sliding position. In addition, the gas in the mandrel cavity 8 will be compressed or expanded as the sleeve mandrel 4 slides, which is also not conducive to the stable sliding of the sleeve mandrel 4. To this end, a drainage hole 33 connected to the bottom end of the mandrel cavity 8 can be formed on the wall of the sleeve outer tube, that is, the drainage hole 33 can be adjacent to the second limiting step 31, so that the fluid in the mandrel cavity 8 can be discharged into the wellbore annulus, so that the downhole energy-concentrating fracturing sleeve of the present invention has good use stability and environmental adaptability.

[0067] In addition, the return spring 5 can be set in a variety of appropriate forms and apply a force toward the first sliding position to the sliding sleeve spindle 4. In the preferred embodiment shown in the figure, a first spring seat 43 is formed on the outer peripheral wall of the sliding sleeve spindle 4, and a second spring seat 34 axially spaced and opposite to the first spring seat 43 is formed on the inner periphery of the cylinder wall of the sliding sleeve outer cylinder (outer cylinder body 3). The return spring 5 is a coil spring that is sleeved on the outer periphery of the sliding sleeve spindle 4 and abuts against the first spring seat 43 and the second spring seat 34 at both ends. As a result, the return spring 5 and the sliding sleeve spindle 4 can be conveniently and accurately installed in the sliding sleeve outer cylinder, and the sliding sleeve spindle 4 can slide stably in the sliding sleeve outer cylinder.

[0068] Embodiment 3

[0069] Reference Figure 3 A CO2 impact composite fracturing method according to a preferred embodiment of the present invention utilizes the above-mentioned downhole energy-gathering fracturing sleeve to implement fracturing operations in oil and gas fields. The CO2 impact composite fracturing method comprises the following steps:

[0070] S0. After drilling a vertical well, run casing and complete the well by perforating the reservoir section;

[0071] S1. Connecting the downhole energy-concentrated fracturing sleeve to the oil pipe, and anchoring the downhole energy-concentrated fracturing sleeve after moving it to the reservoir perforation section;

[0072] S2. It includes sub-steps S21 and S22. In sub-step S21, liquid CO2 fracturing fluid carrying micro-nano proppants is continuously pumped into the oil pipe from the ground to perform oil pipe energy gathering, so that the pressure in the energy gathering chamber 6 increases; in sub-step S22, the sleeve mandrel 4 overcomes the elastic force of the return spring 5 and slides from the first sliding position to the second sliding position, the inner through hole 41 is connected with the outer through hole 32 to form a leakage channel, the energy gathering fracturing sleeve is opened, and the high-pressure CO2 fracturing fluid instantly impacts the reservoir to fracture, and at the same time, the high-speed fluid transports the micro-nano proppants to the microcracks in the deep formation to form effective support;

[0073] S3. After the pressure in the energy-gathering chamber 6 is released to the target reservoir through the inner through hole 41 and the outer through hole 32, the sleeve mandrel 4 is reset to the first sliding position under the action of the reset spring 5 until it abuts against the first limit step 21, so that the inner through hole 41 is separated from the outer through hole 32;

[0074] S4. Repeat steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir.

[0075] The CO2 impact composite fracturing method can control the pressure difference between the energy-gathering chamber 6 and the reset spring 5 applied to the sleeve mandrel 4 by controlling the surface pumping program, and then control the opening and closing of the downhole energy-gathering fracturing sleeve, thereby realizing single-layer multi-stage impact fracturing, greatly simplifying the pipe string structure, construction process and process action, and effectively improving the energy-gathering reliability and operation efficiency. By repeating steps S2 and S3, multi-stage controllable impact fracturing can be performed on the reservoir site to enhance the reservoir transformation effect. The use of high-speed impact fluid to transport micro-nano proppants into the micro-cracks in the deep formation and the cracks generated by impact fracturing increases the transport distance of the proppants and effectively maintains the conductivity of the artificial cracks in the dense bedrock of the unconventional reservoir. After the fracturing is completed, CO2 is easy to return, and the impact fracturing is more operable and safer, and causes less damage to the fracturing pipe string and tools.

[0076] Since completion fluid, formation water, cementing cement, etc. are inevitably left in the well during the drilling and completion process, the residue of these liquids will attenuate the energy of energy dissipation impact. Therefore, after the casing cementing is completed, the completion string can be used to discharge the residual formation water or completion fluid in the main wellbore before the completion string is pulled out, and then the gas injection operation of the above steps S1 to S4 is performed to prevent the residual liquid in the well from weakening the subsequent impact energy.

[0077] In step S1, the oil pipe may be provided with a packer, which is set in the reservoir pocket by pressurizing the oil pipe to reduce the overpressure at the wellhead caused by subsequent downhole impact. In a preferred embodiment, the micro-nano proppant and the liquid CO2 fracturing fluid can be fully mixed on the ground by a closed sand mixing truck, and then the mixed fluid is pressurized by a high-pressure pump and pumped into the oil pipe through the wellhead.

[0078] In step S2, when the oil pipe pressure rises to a predetermined value, the downhole energy-gathering fracturing sleeve is opened. The predetermined value of the pressure can be determined according to the reservoir lithology, and is generally 10% to 30% higher than the formation fracture pressure of the corresponding reservoir. Supercritical CO2 has stronger compressibility and energy storage characteristics than liquid CO2. Therefore, it is preferred to use supercritical CO2 for downhole physical energy gathering, install a heat exchanger at the wellhead, and use the waste heat generated by the construction operation to heat the liquid CO2 fracturing fluid carrying micro-nano proppants at the wellhead to ensure that it can be converted into a supercritical state in the reservoir section.

[0079] In a preferred embodiment of the CO2 impact composite fracturing method, a pressure test step may also be included in step S2. Specifically, liquid CO2 fracturing fluid is continuously pumped into the oil pipe, and after the pressure in the downhole energy-focused fracturing sleeve reaches the test pressure value, the injection of the fracturing medium is suspended and the change in the pressure value in the downhole energy-focused fracturing sleeve is observed. If the pressure value loss does not exceed 5% within 5 minutes, it is considered that the energy-focusing requirement is met.

[0080] In step S4, the tubing is released from anchoring by ground pressure, and after the tubing is dragged to the next layer, steps S1 to S3 are repeated to achieve multi-stage and multi-level controllable impact fracturing, expand the fracturing scale, improve the transformation effect, and save the construction period.

[0081] Continue to refer to Figure 3 As shown, the CO2 impact composite fracturing method of the present invention may also include step S5 implemented after step S4: replacing the hydraulic fracturing string and performing hydraulic fracturing operations. Thus, through the dynamic impact and hydraulic fracturing quasi-static loading composite fracturing method, the rock fracturing pressure can be reduced, the reservoir can produce a better quality complex fracture network, and the fracturing scale can be expanded, thereby achieving the purpose of efficient development of unconventional oil and gas.

[0082] The following combination Figure 2 The downhole energy-concentrated fracturing sleeve and Figure 3 The process of the CO2 impact composite fracturing method shown in the figure exemplifies the specific implementation process of a CO2 impact composite fracturing method:

[0083] First, a vertical well is drilled in the formation, and the casing is cemented to form a main wellbore. After the casing is cemented, the casing, cement ring and near-well reservoir are perforated using the casing perforation technology to form perforations connecting the far end of the reservoir and the main wellbore. The drilling, cementing, perforation completion and other devices and methods are all existing technologies, so they will not be described in detail here.

[0084] After perforation completion, before the completion string is pulled out, the completion string is used to discharge the residual formation water or completion fluid in the main wellbore to prevent the residual liquid in the well from weakening the subsequent impact energy.

[0085] The downhole energy-concentrated fracturing sleeve is connected to the reservoir perforation section through the oil pipe and anchored. The packer is set in the reservoir pocket by pressurizing the oil pipe, reducing the overpressure at the wellhead caused by subsequent downhole impact. The outer through hole 32 on the outer cylinder body 3 is at the same water level depth as the perforation holes in the reservoir section. The high-pressure fracturing fluid after energy release can directly enter the deep formation through the perforation holes, reducing the energy loss of the shock wave and high-pressure fluid acting on the downhole energy-concentrated fracturing sleeve, and protecting the integrity of the wellbore.

[0086] Test the pressure of the downhole energy-gathering fracturing sleeve. Specifically, continue to pump liquid CO2 fracturing fluid into the oil pipe. When the pressure in the downhole energy-gathering fracturing sleeve reaches the test pressure value, stop injecting the fracturing fluid and observe the pressure change in the downhole energy-gathering fracturing sleeve. If the pressure loss does not exceed 5% within 5 minutes, it is determined that the energy-gathering requirements are met.

[0087] On the ground, the micro-nano proppant and liquid CO2 fracturing fluid are fully mixed through a closed sand mixing truck. The mixed liquid is then pressurized by a high-pressure pump and heated through a wellhead heat exchanger before being continuously pumped into the oil pipe. The synergistic formation heating converts the CO2 fracturing fluid into supercritical CO2, which greatly enhances its compressibility and energy storage properties.

[0088] As the pumping progresses, the pressure in the energy-gathering chamber 6 of the downhole energy-gathering fracturing sleeve continues to increase, pushing the sleeve mandrel 4 to slide along the axial second sliding position and compressing the compression spring 5 until it is reset to abut against the second limit step 31. When the pressure in the energy-gathering chamber 6 increases to 10% to 30% higher than the formation fracture pressure, the multiple coplanar inner through holes 41 of the sleeve mandrel 4 are connected to the multiple coplanar outer through holes 32 of the outer cylinder body 3, the downhole energy-gathering fracturing sleeve is opened, and the high-temperature and high-pressure supercritical CO2 fracturing fluid carrying micro-nano proppants releases energy instantaneously along the connected inner and outer through holes, impacting and fracturing the target reservoir.

[0089] After one impact fracturing, the pressure in the energy-gathering chamber 6 decreases, and the sleeve mandrel 4 moves axially toward the wellhead (i.e., toward the first sliding position) under the thrust of the compression spring 5 until it is reset to abut against the first limit step 21, completing a single-layer single impact fracturing. Repeating the impact fracturing steps multiple times can achieve single-layer multi-stage impact fracturing, forming reservoir fractures that can better meet the needs of oil and gas production.

[0090] Release the tubing anchor, drag the tubing string to the next layer and repeat the above operation to achieve multi-stage and multi-level controllable impact fracturing. The scale of impact fracturing can be expanded and the transformation effect can be improved without replacing the fracturing string.

[0091] Afterwards, a conventional hydraulic fracturing string is replaced to perform hydraulic fracturing operations. The hydraulic fracturing device and fracturing method used in the hydraulic fracturing operations are both prior art and will not be described in detail herein.

[0092] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A downhole energy-focused fracturing sleeve, characterized in that: include: A sliding sleeve outer cylinder, the sliding sleeve outer cylinder comprising a first limiting step (21) and a second limiting step (31) which are arranged on the inner periphery of the cylinder wall and are axially spaced and opposite to each other, and an outer through hole (32) formed in a portion of the cylinder wall located between the first limiting step (21) and the second limiting step (31); A sliding sleeve spindle (4), the sliding sleeve spindle (4) being reciprocatingly slidably mounted in the inner cavity of the sliding sleeve outer cylinder and defining an energy-gathering cavity (6) in the inner cavity, the sliding sleeve spindle (4) being formed with an inner through hole (41) communicating with the energy-gathering cavity (6); and, A return spring (5) elastically abuts against the sleeve spindle (4) so ​​that the sleeve spindle (4) tends to remain in a first sliding position defined by the first limiting step (21), and the inner through hole (41) is isolated from the outer through hole (32); when the pressure in the energy gathering chamber (6) reaches a predetermined value, the sleeve spindle (4) can overcome the elastic force of the return spring (5) and slide from the first sliding position to the second sliding position defined by the second limiting step (31), and the inner through hole (41) is connected to the outer through hole (32).

2. The downhole energy-focused fracturing sleeve according to claim 1, characterized in that: The sliding sleeve outer cylinder comprises an outer cylinder body (3) and an upper joint (2) screwed to the outer cylinder body (3); one end of the upper joint (2) screwed to the inner side of the outer cylinder body (3) forms the first limiting step (21); when the sliding sleeve core shaft (4) is located at the first sliding position, the sliding sleeve core shaft (4) abuts against the upper joint (2).

3. The downhole energy-focused fracturing sleeve according to claim 2, characterized in that: Along the direction toward the sliding sleeve spindle (4), the inner diameter of the portion of the upper joint (2) close to the sliding sleeve spindle (4) gradually decreases.

4. The downhole energy-focused fracturing sleeve according to claim 2, characterized in that: A sealing ring (7) is provided between the upper joint (2) and the outer cylinder body (3) and / or between the sliding sleeve spindle (4) and the outer cylinder body (3).

5. The downhole energy-focused fracturing sleeve according to claim 2, characterized in that: A coupling (1) is threadedly connected to one end of the upper joint (2) away from the outer cylinder body (3).

6. The downhole energy-focused fracturing sleeve according to claim 1, characterized in that: When the sleeve spindle (4) is located at the first sliding position, one end of the sleeve spindle (4) close to the energy gathering chamber (6) abuts against the first limiting step (21); a third limiting step (42) is formed on the outer peripheral wall of the sleeve spindle (4), and when the sleeve spindle (4) is located at the second sliding position, the third limiting step (42) abuts against the second limiting step (31).

7. The downhole energy-focused fracturing sleeve according to claim 6, characterized in that: Between the second limiting step (31) and the third limiting step (42), the outer peripheral wall of the sliding sleeve spindle (4) and the inner peripheral wall of the sliding sleeve outer tube are spaced apart to form a spindle cavity (8).

8. The downhole energy-focused fracturing sleeve according to claim 7, characterized in that: A drainage hole (33) communicating with the bottom end of the spindle cavity (8) is formed on the wall of the outer cylinder of the sliding sleeve.

9. The downhole energy-focused fracturing sleeve according to claim 1, characterized in that: A first spring seat (43) is formed on the outer peripheral wall of the sliding sleeve shaft (4), and a second spring seat (34) is formed on the inner peripheral wall of the sleeve outer cylinder and is axially spaced and opposite to the first spring seat (43). The return spring (5) is a coil spring which is sleeved on the outer peripheral wall of the sliding sleeve shaft (4) and abuts against the first spring seat (43) and the second spring seat (34) at both ends.

10. A CO2 impact composite fracturing method, characterized in that: The steps include: S1. Connecting the downhole energy-focused fracturing sleeve according to any one of claims 1 to 9 to the oil pipe, and anchoring the downhole energy-focused fracturing sleeve after it moves to the reservoir perforation section; S2. Pumping liquid CO2 fracturing fluid carrying micro-nano proppants into the oil pipe on the ground, so that the pressure in the energy-gathering chamber (6) increases, thereby causing the sliding sleeve mandrel (4) to overcome the elastic force of the return spring (5) and slide from the first sliding position to the second sliding position, and causing the inner through hole (41) to communicate with the outer through hole (32), using the liquid CO2 fracturing fluid to impact and fracture the target reservoir, and transporting the micro-nano proppants into the reservoir cracks; S3. After the pressure in the energy-gathering chamber (6) is released through the inner through hole (41) and the outer through hole (32), the sliding sleeve spindle (4) is reset to the first sliding position under the action of the reset spring (5) until the inner through hole (41) is isolated from the outer through hole (32); S4. Repeat steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir.

11. The CO2 impact composite fracturing method according to claim 10, characterized in that: Step S4 includes: releasing the anchoring of the oil pipe, dragging the oil pipe to the reservoir perforation section of the next layer, and repeating steps S2 and S3 to perform multi-stage impact fracturing on the target reservoir of the next layer.

12. The CO2 impact composite fracturing method according to claim 10, characterized in that: The method further includes step S5 implemented after step S4: replacing the hydraulic fracturing string and performing hydraulic fracturing operations.

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