A full-gauge fracturing sliding sleeve, pipe string and operation method thereof

Abstract

The application provides a full-bore fracturing sliding sleeve, which comprises an outer cylinder, an upper joint and a lower joint connected to two ends of the outer cylinder respectively, an inner cylinder arranged concentrically in the outer cylinder, the inner cylinder being fixed to the outer cylinder through a first shear pin, and a lower sleeve arranged at a lower end of the inner cylinder, the lower sleeve being fixed to the inner cylinder through a second shear pin, wherein the shear critical value of the second shear pin is greater than that of the first shear pin, the inner cylinder can cooperate with a running tool through the running tool, and the inner cylinder can be driven to shear the first shear pin under the action of pressure difference and then move downward until the lower sleeve is seated on an upper end surface of the lower joint to open the flow passage, the inner cylinder can continue to move downward after shearing the second shear pin under the action of pressure, and the running tool is retracted to pass through the full-bore fracturing sliding sleeve. The application further provides a pipe string and a working method of the full-bore fracturing sliding sleeve.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well completion and fracturing operations, specifically relating to a full-bore fracturing sliding sleeve, tubing string and its operation method. Background Technology

[0002] Multi-stage fracturing, especially horizontal well fracturing, is a key technology for improving oil and gas recovery during the development of unconventional oil and gas reservoirs such as shale gas and tight gas. Increasing the number of fracturing channel clusters during multi-stage fracturing can enhance the complexity of the formation fracture network and facilitate effective communication between fractures.

[0003] Existing technologies for multi-stage, multi-cluster fracturing primarily employ a combination of bridge plug and perforation techniques, which suffer from drawbacks such as numerous operational steps, long construction times, high operating costs, and discontinuous construction. In contrast, conventional multi-stage sliding sleeve packer segmented fracturing technology divides the formation into multiple segments using packers based on the formation conditions, and then opens the sliding sleeves using ball dropping or specialized opening tools. This enables layer-by-layer fracturing operations, ensuring continuous construction and simplifying the operational procedures.

[0004] Chinese invention patent ZL201210587000.7 discloses a ball-throwing method for opening multiple clusters of sliding sleeves, which can open multiple clusters of sliding sleeves with a single ball throw. However, due to the use of conventional ball-throwing methods, there are grade differences, with the size of the ball increasing from bottom to top. Since the inner diameter of the wellbore is fixed, the number of stages in this method is limited, and it cannot achieve unlimited stages. Moreover, since the inner diameter of the sliding sleeves in different levels gradually decreases, it cannot achieve full-bore operation, thus limiting the maximum pumping efficiency of the surface pumping equipment.

[0005] Chinese invention patent ZL201610037797.1 discloses a new type of sliding sleeve, a sliding sleeve opening tool, and a fracturing tubing string. The sliding sleeve has a full-bore stepless function, but it can only open one sliding sleeve with one opening tool, and cannot open multiple sliding sleeves with one opening tool, which cannot meet the needs of on-site construction for multi-segment and multi-cluster technology. Summary of the Invention

[0006] To address the technical problems mentioned above, this invention aims to propose a full-bore fracturing sleeve that is used in conjunction with a conventional stepless sleeve. Multiple full-bore fracturing sleeves and conventional stepless sleeves are installed on the tubing string, and multiple stepless multi-cluster fracturing sleeves can be opened with a single opening tool to meet the needs of unconventional oil and gas reservoir stimulation.

[0007] Therefore, according to a first aspect of the present invention, a full-bore fracturing sleeve is provided, comprising: an outer cylinder having a guide hole penetrating its sidewall; an upper connector and a lower connector respectively connected to both ends of the outer cylinder; an inner cylinder concentrically arranged within the outer cylinder, the inner cylinder being fixed to the outer cylinder by a first shear pin; and a lower sleeve disposed at the lower end of the inner cylinder, the lower sleeve being fixed to the inner cylinder by a second shear pin; wherein the shearing critical value of the second shear pin is greater than that of the first shear pin, and can cooperate with the inner cylinder by lowering an opening tool, and through the pressure difference, drive the inner cylinder to shear the first shear pin and move downward until the lower sleeve sits against the upper end face of the lower connector to open the guide hole, the inner cylinder can continue to move downward after shearing the second shear pin under pressure, and the opening tool retracts to pass through the full-bore fracturing sleeve.

[0008] In one embodiment, the opening tool is configured to include a ball seat portion and an elastic claw fixedly connected to the upper end of the ball seat portion. The outer surface of the elastic claw is provided with a first protrusion, and the inner wall of the inner cylinder is provided with a first annular groove. The first protrusion can cooperate with the first annular groove and transmit axial pressure.

[0009] In one embodiment, the inner wall of the inner cylinder is further provided with a plurality of second annular grooves evenly spaced apart along the axial direction. The sidewall of the second annular groove is constructed as a first inclined surface. The outer surface of the elastic claw is provided with a plurality of second protrusions that can cooperate with the second annular groove. The inner cylinder can apply pressure to the upper end surface of the second protrusion through the sidewall of the second annular groove, thereby causing the elastic claw to contract radially.

[0010] In one embodiment, the inner wall of the ball seat portion is constructed with a conical surface for fitting into the pressure ball.

[0011] In one embodiment, the outer wall of the lower sleeve is provided with an upward-facing step, and the upper part of the lower sleeve is inserted into the inner cylinder to be fixed to the inner cylinder by a second shear pin, and a gap is formed between the lower end face of the inner cylinder and the end face of the step.

[0012] In one embodiment, the upper end face of the lower sleeve is configured as a third inclined surface.

[0013] In one embodiment, two spaced-apart first seals are provided between the inner cylinder and the outer cylinder, and when the guide hole is closed, the guide hole and the first shear pin are located axially between the two first seals.

[0014] In one embodiment, both the upper connector and the lower connector are configured as stepped connecting buckles, and a second sealing element is provided between the connecting surfaces of the upper connector, the lower connector and the outer cylinder.

[0015] According to a second aspect of the present invention, a tubing string is provided, characterized in that it comprises a plurality of full-bore fracturing sleeves as described above, the plurality of full-bore fracturing sleeves being connected in series, and the opening tool being capable of sequentially opening the corresponding full-bore fracturing sleeves and passing through.

[0016] According to a third aspect of the present invention, a method for operating a full-bore fracturing sleeve is provided, characterized by comprising the following steps:

[0017] Step 1: Connect multiple full-bore fracturing sleeves in series to the tubing string and run the tubing string into the predetermined formation;

[0018] Step 2: Deploy the opening tool from the wellhead and pump the opening tool to the corresponding full-bore fracturing sleeve;

[0019] Step 3: The opening tool is adapted to the inner cylinder and, under the action of pressure difference, cuts the first shearing pin and drives the lower sleeve downward, thereby opening the guide hole;

[0020] Step 4: Continue to pressurize until the inner cylinder shears the second shear pin. Under the action of pressure difference, the inner cylinder causes the opening tool to contract, allowing the opening tool to pass through the corresponding full-bore fracturing sleeve and descend to the next level of the full-bore fracturing sleeve.

[0021] Step 5: The opening tool is then used, and steps 3 and 4 above are repeated until all the full-bore fracturing sleeves are opened.

[0022] Compared with the prior art, the advantages of this application are:

[0023] The full-bore fracturing sleeve of the present invention, when used in conjunction with a conventional stepless sleeve, can be used as a stepless multi-cluster fracturing sleeve. Furthermore, multiple stepless multi-cluster fracturing sleeves can be opened with a single opening tool to meet the needs of unconventional oil and gas reservoir stimulation. The operation method of the full-bore fracturing sleeve according to the present invention is simple, greatly improves the sleeve opening efficiency, and effectively ensures the success rate of sleeve opening, which is highly beneficial for improving the efficiency of oil and gas reservoir stimulation operations. Attached Figure Description

[0024] The present invention will now be described with reference to the accompanying drawings.

[0025] Figure 1 The structure of the full-bore fracturing sleeve according to the present invention is schematically shown.

[0026] Figure 2 The structure of the opening tool according to the present invention is shown schematically.

[0027] Figure 3 schematically shown Figure 1 The connection structure between the inner cylinder and the lower sleeve in the full-bore fracturing sleeve.

[0028] Figures 4 to 6 The opening process of the full-bore fracturing sleeve according to the present invention is shown.

[0029] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0030] The invention will now be described with reference to the accompanying drawings.

[0031] In this application, it should be noted that the end of the full-bore fracturing sleeve according to the present invention that is lowered into the wellbore near the wellhead is defined as the upper end or a similar term, and the end that is further away from the wellhead is defined as the lower end or a similar term. It should also be noted that the directional terms or limiting words "upper," "lower," etc., used in this application are all specific to the referenced appendix. Figure 1 In other words, they are not used to define the absolute position of the components involved, but can vary depending on the specific circumstances.

[0032] Figure 1 The structure of the full-bore fracturing sleeve 100 according to the present invention is schematically shown. Figure 1 As shown, the full-bore fracturing sleeve 100 includes an outer cylinder 1, an inner cylinder 4 concentrically arranged inside the outer cylinder 1, a lower sleeve 6, and an upper connector 2 and a lower connector 3 respectively connected to the upper and lower ends of the outer cylinder 1. The outer cylinder 1 is provided with a guide hole 11 penetrating its side wall. In the initial state, the inner cylinder 4 is fixed to the outer cylinder 1 by a first shear pin 5, and the lower sleeve 6 is connected to the lower end of the inner cylinder 4 and fixed to the inner cylinder 4 by a second shear pin 7. The shear critical value of the second shear pin 7 is greater than the shear critical value of the first shear pin 5. In actual operation, by lowering the opening tool 200, the opening tool 200 reaches the position of the full-bore fracturing sleeve 100 and can cooperate with the inner cylinder 4. Through the pressure difference, the inner cylinder 4 is driven to shear the first shear pin 5 and then move downward until the lower sleeve 6 sits on the upper end face of the lower connector 3, thereby opening the guide hole 11. With continued pressure, the inner cylinder 4 can shear the second shear pin 7 when it reaches the critical shear value of the second shear pin 7 and continue to move downward. It can also cause the opening tool 200 to retract radially inward, so that the opening tool 200 passes through the full-bore fracturing sleeve 100.

[0033] In one embodiment, multiple flow guide holes 11 are provided, and the multiple flow guide holes 11 are distributed at intervals in the circumferential direction. The size and number of flow guide holes 11 can be adjusted according to the actual situation. Preferably, the flow guide holes 11 are located near the upper end of the outer cylinder 1.

[0034] like Figure 1 As shown, both the upper connector 2 and the lower connector 3 are constructed as stepped connecting buckles, and the stepped connecting buckles are provided with external threads. The stepped connecting buckle corresponding to the upper connector 2 is inserted into the outer cylinder 1 and extends downward, while forming a fixed connection with the upper end of the outer cylinder 1 through a threaded connection. Similarly, the stepped connecting buckle corresponding to the lower connector 3 is inserted into the outer cylinder 1 and extends upward, while forming a fixed connection with the lower end of the outer cylinder 1 through a threaded connection. Thus, the upper end face of the lower connector 3 is formed inside the outer cylinder 1, thereby forming an inner stepped surface with the end face facing upward.

[0035] To ensure a tight seal between the upper connector 2, the lower connector 3, and the outer cylinder 1, a second sealing element 9 is provided between the connecting surfaces of the upper connector 2, the lower connector 3, and the outer cylinder 1. Preferably, a radially inwardly extending sealing groove is provided on the outer surface of the upper connector 2 and the lower connector 3, and the second sealing element 9 is installed in the sealing groove.

[0036] According to the present invention, two spaced-apart first sealing elements 8 are provided between the inner cylinder 4 and the outer cylinder 1. When the guide hole 11 is in the closed state, the guide hole 11 and the first shear pin 5 are located axially between the two first sealing elements 8. This effectively ensures the sealing performance of the full-bore fracturing sleeve 100, thereby effectively ensuring the internal pressure of the full-bore fracturing sleeve 100. In one embodiment, sealing mounting grooves spaced apart from each other in the circumferential direction are provided on the outer wall of the inner cylinder 4, and two second sealing elements 8 are respectively installed in the corresponding sealing mounting grooves.

[0037] According to the present invention, such as Figure 2 As shown, the opening tool 200 is configured to include a ball seat portion 210 and an elastic claw 220 fixedly connected to the upper end of the ball seat portion 210. The inner wall of the ball seat portion 210 is constructed with a conical surface 211 for fitting with the pressure ball 201. To facilitate the lowering of the opening tool 200 into the wellbore, the lower end face of the ball seat portion 210 is constructed with a conical surface, which facilitates guiding the lowering process of the opening tool 200.

[0038] In this embodiment, multiple elastic claws 220 are provided, and the multiple elastic claws 220 are evenly spaced apart in the circumferential direction.

[0039] According to the present invention, such as Figure 1 and Figure 2As shown, a first protrusion 221 is provided on the outer surface of the elastic claw 220. Simultaneously, a first annular groove 41 is provided on the inner wall of the inner cylinder. The first protrusion 221 can engage with the first annular groove 41 and transmit axial pressure. The cross-section of the first protrusion 221 is rectangular, and the cross-section of the first annular groove 41 is also rectangular. Preferably, the first protrusion 221 is located near the upper end of the elastic claw 220. Furthermore, the axial width of the first annular groove 41 is greater than the axial width of the first protrusion 221. During operation, when the opening tool 100 reaches the corresponding full-bore fracturing sleeve 100 position, the first protrusion 221 can fit into the first annular groove 41 to form a fit, causing the lower end face of the first protrusion 221 to abut against the lower side wall of the first annular groove 41. Thus, the opening tool 200 can transmit pressure through the lower end face of the first protrusion 221 to the lower side wall of the first annular groove 41, and subsequently to the inner cylinder 4.

[0040] like Figure 2 and Figure 3 As shown, the inner wall of the inner cylinder 4 is also provided with a plurality of second annular grooves 42 evenly spaced along the axial direction, and the side wall surface of the second annular grooves 42 is constructed as a first inclined surface 421. At the same time, the outer surface of the elastic claw 220 is also provided with a plurality of second protrusions 222 that can cooperate with the second annular grooves 42. The upper and lower end faces of the second protrusions 222 are also constructed as second inclined surfaces 223 that can be adapted to the first inclined surface 421. The axial width of the second annular groove 42 is greater than the axial width of the second protrusions 222. The inner cylinder 4 can apply pressure to the upper end face (third inclined surface 223) of the second protrusions 222 through the side wall surface (first inclined surface 421) of the second annular groove 42, thereby using the cooperation between the first inclined surface 421 and the second inclined surface 223 to make the elastic claw 220 radially contract inward, thereby releasing the cooperation between the elastic claw 220 and the inner cylinder 4, and thus allowing the opening tool 200 to pass through the full-bore fracturing sleeve 100.

[0041] Preferably, the second protrusion 222 is located at the lower end of the first protrusion 221.

[0042] According to the present invention, a step 61 with its end face facing upward is provided on the outer wall near the lower end of the lower sleeve 6. The upper end portion of the lower sleeve 6 is inserted into the inner cylinder 4 and fixed to the inner cylinder 4 by a second shear pin 7. Furthermore, a gap is formed between the lower end face of the inner cylinder 4 and the end face of the step 61 to allow the inner cylinder 4 to move relative to the lower sleeve 6.

[0043] In one embodiment, the upper end face of the lower sleeve 6 is configured as a third inclined surface 62. Figure 3In the illustrated embodiment, the third inclined surface 62 at the upper end of the lower sleeve 6 and the first inclined surface 421 at the lowermost end of the inner wall of the inner cylinder 4 together form a second annular groove 42, and this second annular groove 42 is located at the lowermost end. In actual operation, the second protrusion 222 at the lowermost end of the opening tool 200 engages with the second annular groove 42 at the lowermost end of the inner cylinder 4.

[0044] According to the present invention, a tubing string is also provided, comprising multiple full-bore fracturing sleeves 100 and multiple conventional stepless sleeves. The multiple full-bore fracturing sleeves 100 are connected in series and used in conjunction with the conventional stepless sleeves to form a working tubing string. An opening tool 200 can sequentially open the corresponding full-bore fracturing sleeves 100 and pass through. This tubing string can meet the needs of unconventional oil and gas reservoir stimulation.

[0045] According to the present invention, a method for operating a full-bore fracturing sleeve 100 is also provided. The following is based on... Figures 4 to 6 This section details the operation method for the full-bore fracturing sleeve 100.

[0046] First, multiple full-bore fracturing sleeves 100 are connected in series in the tubing string, thus forming a working tubing string in conjunction with multiple conventional stepless sleeves. Initially, all full-bore fracturing sleeves 100 are in the closed state.

[0047] After that, the working string is lowered to the designated formation.

[0048] After the working tubing is in place, when the full-bore fracturing sleeve 100 needs to be opened, the opening tool 200 is deployed from the wellhead. The opening tool 200 is pumped through the mismatched sleeve until it enters the matched full-bore fracturing sleeve 100, at which point the opening tool 200 stops moving. At this point, if... Figure 4 As shown, the ball seat portion 210 of the opening tool 200 forms a clearance fit with the lower sleeve 6, causing the liquid to throttle, thereby creating a pressure difference above and below the opening tool 200, and transmitting axial pressure to the inner cylinder 4 through the first protrusion 221. When the pressure reaches the shearing critical value of the first shearing pin 5, the inner cylinder 4 shears the first shearing pin 5 and drives the lower sleeve 6 and the opening tool 200 downward. Until the lower end face of the lower sleeve 6 contacts the upper end face of the lower connector 3, at this time, as... Figure 5 As shown, the lower sleeve 6 sits on the upper end face of the lower connector 3 to form a limit. This opens the guide hole 11 of the full-bore fracturing sleeve 100.

[0049] Subsequently, pressure is continued to be applied, and the inner cylinder 4 and the opening tool 200 jointly apply downward pressure. When the pressure reaches the critical shear value of the second shear pin 7, the inner cylinder 4 shears the second shear pin 7 and moves downward. Under the action of pressure difference, the inner cylinder 4 applies pressure to the third inclined surface 223 of the second protrusion 222 of the opening tool 200 through the first inclined surface 421 of the second annular groove 42. Thus, the elastic claw 220 is radially contracted inward by the cooperation between the first inclined surface 421 and the second inclined surface 223, thereby releasing the cooperation between the elastic claw 220 and the inner cylinder 4. As a result, the opening tool 200 passes through the full-bore fracturing sleeve 100 under the action of pump pressure. Figure 6 The diagram schematically shows the structure of the resilient claw 220 of the opening tool 200 in a retracted state.

[0050] After the opening tool 200 passes through the first-stage full-bore fracturing sleeve 100, it continues to pump to the next-stage full-bore fracturing sleeve 100.

[0051] Then, repeat the above steps until all full-bore fracturing sleeves 100 in the tubing string are opened, and then proceed with subsequent operations. This allows multiple continuously variable, multi-cluster fracturing sleeves to be opened using a single opening tool 200, meeting the needs of unconventional oil and gas reservoir stimulation.

[0052] The full-bore fracturing sleeve 100 of the present invention, when used in conjunction with a conventional stepless sleeve, can be used as a stepless multi-cluster fracturing sleeve. Furthermore, multiple stepless multi-cluster fracturing sleeves can be opened using a single opening tool 200 to meet the needs of unconventional oil and gas reservoir stimulation. The operation method of the full-bore fracturing sleeve according to the present invention is simple, greatly improves the sleeve opening efficiency, and effectively ensures the success rate of sleeve opening, which is highly beneficial for improving the efficiency of oil and gas reservoir stimulation operations.

[0053] In this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A full-bore fracturing sleeve, comprising: Outer cylinder (1), the outer cylinder is provided with a flow guide hole (11) penetrating its side wall. The upper connector (2) and the lower connector (3) are respectively connected to the two ends of the outer cylinder; An inner cylinder (4) is concentrically arranged inside the outer cylinder, and the inner cylinder is fixed to the outer cylinder by a first shear pin (5); A lower sleeve (6) is provided at the lower end of the inner cylinder, and the lower sleeve is fixed to the inner cylinder by a second shear pin (7); Wherein, the shear critical value of the second shear pin is greater than that of the first shear pin. The lower opening tool (200) can cooperate with the inner cylinder and drive the inner cylinder to cut the first shear pin and move downwards through the pressure difference until the lower sleeve sits on the upper end face of the lower connector to open the guide hole. The inner cylinder can cut the second shear pin under pressure and continue to move downwards, and the opening tool will retract to pass through the full-bore fracturing sleeve. The opening tool is configured to include a ball seat portion (210) and an elastic claw (220) fixedly connected to the upper end of the ball seat portion. The outer surface of the elastic claw is provided with a first protrusion (221), and the inner wall of the inner cylinder is provided with a first annular groove (41). The first protrusion can cooperate with the first annular groove and transmit axial pressure. The inner wall of the inner cylinder is also provided with a plurality of second annular grooves (42) evenly spaced along the axial direction. The side wall of the second annular groove is constructed as a first inclined surface (421). The outer surface of the elastic claw is provided with a plurality of second protrusions (222) that can cooperate with the second annular groove. The inner cylinder can apply pressure to the upper surface of the second protrusion through the side wall of the second annular groove, thereby causing the elastic claw to contract radially.

2. The full-bore fracturing sleeve according to claim 1, characterized in that, The inner wall of the ball seat portion has a conical surface (211) for fitting with the pressure ball.

3. The full-bore fracturing sleeve according to claim 1, characterized in that, The outer wall of the lower sleeve is provided with an upward-facing step (61). The upper part of the lower sleeve is inserted into the inner cylinder to be fixed to the inner cylinder by a second shear pin, and a gap is formed between the lower end face of the inner cylinder and the end face of the step.

4. The full-bore fracturing sleeve according to claim 2, characterized in that, The upper end face of the lower sleeve is constructed as a third inclined surface (62).

5. The full-bore fracturing sleeve according to claim 1, characterized in that, Two spaced-apart first seals (8) are provided between the inner cylinder and the outer cylinder. When the guide hole is closed, the guide hole and the first shear pin are located between the two first seals in the axial direction.

6. The full-bore fracturing sleeve according to claim 1, characterized in that, Both the upper connector and the lower connector are constructed as stepped connecting buckles, and a second sealing element (9) is provided between the upper connector, the lower connector and the connecting surface of the outer cylinder.

7. A tubular string, characterized in that, It includes multiple full-bore fracturing sleeves according to any one of claims 1 to 6, the multiple full-bore fracturing sleeves are connected in series, and the opening tool is capable of sequentially opening the corresponding full-bore fracturing sleeves and passing through.

8. A method for operating a full-bore fracturing sleeve according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Connect multiple full-bore fracturing sleeves in series to the tubing string and run the tubing string into the predetermined formation; Step 2: Deploy the opening tool from the wellhead and pump the opening tool to the corresponding full-bore fracturing sleeve; Step 3: The opening tool is adapted to the inner cylinder and, under the action of pressure difference, cuts the first shearing pin and drives the lower sleeve downward, thereby opening the guide hole; Step 4: Continue to pressurize until the inner cylinder shears the second shear pin. Under the action of pressure difference, the inner cylinder causes the opening tool to contract, allowing the opening tool to pass through the corresponding full-bore fracturing sleeve and descend to the next level of the full-bore fracturing sleeve. Step 5: The opening tool is then used, and steps 3 and 4 above are repeated until all the full-bore fracturing sleeves are opened.

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