A multi-stage fracturing tool and method

Abstract

This invention provides a multi-stage fracturing tool and method. The fracturing tool includes a fracturing tubing string and a ball seat assembly. The ball seat assembly includes at least two ball seats, ball seat shear pins, and limiting components. Each ball seat is limited and engaged with the corresponding fracturing tubing string by the limiting components. Along the wellbore insertion direction of the ball seat assembly, the strength of the ball seat shear pins gradually increases, and the pressure-bearing inner diameter of each ball seat gradually decreases. The fracturing method includes: deploying the fracturing tubing string in the wellbore; inserting a pressure-locking ball that seals with the ball seat with the smallest pressure-bearing inner diameter into the ball seat assembly; pumping the ball seat assembly into the wellbore; after all ball seats are limited and engaged with the corresponding fracturing tubing string, and the pressure-locking ball inserted with the ball seat assembly releases the corresponding fracturing tubing string, completing the first stage of fracturing, sequentially inserting pressure-locking balls that seal with the corresponding fracturing tubing string in the reverse direction of the ball seat assembly insertion direction to complete multi-stage fracturing. This invention has the advantages of simple structure, enabling unlimited-stage fracturing, and convenient operation.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well fracturing, and more particularly to a multi-stage fracturing tool and fracturing method. Background Technology

[0002] In well completion and fracturing technology, it is often necessary to perform staged fracturing operations on different sections of the wellbore in diametrical, directional, or horizontal wells. During staged fracturing, the fracturing tool typically uses a ball-dropping method to initiate fracturing. However, because the diameters of the balls used for each stage of the fracturing string differ and the diameter range of the balls is limited, the number of fracturing stages in the fracturing string is restricted. Another tool for achieving multi-stage fracturing is the bottom-seal drag fracturing tool. This tool uses coiled tubing to set, perforate, and fracture at the location requiring fracturing, then releases the tubing and moves it to the next stage, repeating the operation to achieve multi-stage fracturing. However, this method requires the use of coiled tubing, and the setting sleeve needs frequent replacement after repeated setting, affecting operational efficiency and reliability. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a multi-stage fracturing tool and fracturing method that is simple in structure, can realize unlimited-stage fracturing, and is easy to operate.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0005] A multi-stage fracturing tool includes a fracturing tubing string and a ball seat assembly. The ball seat assembly includes at least two ball seat bodies that are sealed to a pressure-absorbing ball, ball seat shear pins connecting adjacent ball seat bodies, and limiting components disposed outside each ball seat body. The matching parameters of each limiting component are different, and each ball seat body is limited to the corresponding fracturing tubing string through the limiting component. Along the wellhead insertion direction of the ball seat assembly, the strength of the ball seat shear pins gradually increases, and the pressure-bearing inner diameter of each ball seat body sealing to the pressure-absorbing ball gradually decreases.

[0006] As a further improvement to the above technical solution:

[0007] The limiting component is a spiral limiting component, which includes a spiral groove and a spiral boss. The spiral groove and the spiral boss are respectively disposed on the ball seat and the fracturing string. The matching parameters of the spiral groove and the spiral boss include the spiral width, the spiral pitch, the spiral length, the number of spiral segments, and the spiral direction.

[0008] The spiral limiting component also includes meshing teeth disposed between the spiral groove and the spiral boss, and the spiral groove and the spiral boss are engaged and clamped together by the meshing teeth.

[0009] The spiral limiting component is at least two sets, and the two sets of spiral limiting components are arranged at intervals along the axis of the ball seat; when there are more than two sets of spiral limiting components, at least one set of spiral limiting components is provided with meshing teeth.

[0010] The number of spiral turns in the spiral groove is greater than the number of spiral turns in the spiral boss that matches the spiral groove.

[0011] The fracturing string includes an outer sleeve with a fracturing hole, an inner sliding sleeve installed at the fracturing hole position, and a string shear pin disposed between the outer sleeve and the inner sliding sleeve. The inner sliding sleeve is limited to the corresponding ball seat body. The string shear pin cuts when the inner sliding sleeve is limited to the corresponding ball seat body to open the fracturing hole.

[0012] The multi-stage fracturing tool also includes an axial limiting component that restricts the axial position of the inner sliding sleeve after the fracturing hole is opened. The axial limiting component includes a retaining ring, a retaining ring groove, and a limiting shoulder. The retaining ring is disposed on the inner sliding sleeve, and the retaining ring groove and the limiting shoulder are both disposed on the outer sleeve. When the inner sliding sleeve moves down to the limiting shoulder, the retaining ring and the retaining ring groove engage in a limiting fit.

[0013] The inner sliding sleeve includes an opening sleeve, an elastic claw, and a guide sleeve connected in sequence. The opening sleeve is installed at the fracturing hole position of the outer sleeve by the tubing shear pin. The retaining spring is located at the bottom end of the elastic claw. The bottom end of the guide sleeve engages with the limiting shoulder when the inner sliding sleeve moves downward.

[0014] A fracturing method for the multi-stage fracturing tool described above includes the following steps:

[0015] 1) Deploy the fracturing tubing string in the wellbore;

[0016] 2) Insert a pressure-retaining ball into the ball seat assembly, which is sealed to the ball seat body with the smallest pressure-bearing inner diameter, and pump the ball seat assembly into the well.

[0017] 3) When all ball seats are in contact with the corresponding fracturing tubing and the pressure-blocking balls that are inserted into the well along with the ball seat assembly release the corresponding fracturing tubing and complete the first stage of fracturing, pressure-blocking balls that are in contact with the corresponding fracturing tubing are sequentially inserted in the opposite direction of the ball seat assembly's insertion direction to complete multi-stage fracturing.

[0018] As a further improvement to the above technical solution:

[0019] If the number of fracturing stages exceeds the number of ball seats in the ball seat assembly, after step 3), repeat steps 2) and 3) on the upper fracturing string located in the fracturing completion section until the target number of fracturing stages is completed.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] This invention uses two or more ball seat assemblies, connected by ball seat shear studs. Each ball seat is fitted with a corresponding fracturing tubing string via limiting components with different matching parameters. Its structure is simple and compact, usable within the space of existing fracturing tools, and offers high versatility and low cost. Furthermore, along the wellhead insertion direction of the ball seat assembly, the strength of the ball seat shear studs gradually increases, while the pressure-bearing inner diameter of each ball seat gradually decreases in its sealing fit with the pressure-retaining ball. This allows the first pressure-retaining ball to enter the first ball seat, while the last ball seat, sheared by the ball seat shear studs, is the first to be hooked onto the corresponding fracturing tubing string. This allows each ball seat to be installed sequentially on its corresponding fracturing tubing string, ensuring the smooth release of subsequent fracturing tubing strings and achieving multi-stage fracturing.

[0022] The fracturing method of the multi-stage segmented fracturing tool of the present invention also has the above-mentioned advantages, and is convenient to operate and has high fracturing efficiency, effectively solving the problem of cumbersome construction of single-stage pumping ball seats and the need to use large ground equipment. Furthermore, if the number of fracturing stages is greater than the number of ball seats in the ball seat assembly, the ball seat assembly can be repeatedly deployed to the upper fracturing string located in the completed fracturing section for segmented fracturing. In this case, the ball seat assembly installed each time is independent of each other. That is, the present invention adopts a method of mutual circulation between segmented pumping of ball seat assemblies and ball-drop fracturing, so that ball seats with the same inner diameter can be circulated infinitely, effectively solving the problem of limited number of stages of ball-drop fracturing string, and realizing unlimited-stage fracturing. Attached Figure Description

[0023] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the structure of the multi-stage segmented fracturing tool of the present invention (ball seat assembly in the well).

[0025] Figure 2 This is a schematic diagram of the structure of the multi-stage segmented fracturing tool of the present invention (the ball seat at the tail and the fracturing tubing are in a limiting fit).

[0026] Figure 3 This is a schematic diagram of the structure of the multi-stage segmented fracturing tool of the present invention (ball seat set state).

[0027] Figure 4 This is a schematic diagram of the structure of the multi-stage segmented fracturing tool of the present invention (inner sliding sleeve unsealed state).

[0028] Figure 5 This is a schematic diagram of the ball seat assembly of the present invention.

[0029] Figure 6 This is a schematic diagram of the fracturing tubing of the present invention.

[0030] Figure 7This is a flowchart of a multi-stage fracturing tool fracturing method.

[0031] The labels in the diagram represent:

[0032] 1. Fracturing tubing string; 11. Outer sleeve; 111. Fracturing hole; 112. Upper connector; 113. Central tube; 114. Lower connector; 12. Inner sliding sleeve; 121. Opening sleeve; 122. Elastic claw; 123. Guide sleeve; 124. Snap ring; 13. Tubing string shear pin; 2. Ball seat assembly; 21. Pressure-retaining ball; 22. Ball seat body; 221. Pressure-bearing inner diameter; 23. Ball seat shear pin; 3. Limiting component; 31. Helical groove; 32. Helical boss; 33. Engaging teeth; 4. Axial limiting assembly; 41. Snap ring; 42. Snap ring groove; 43. Limiting shoulder. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention.

[0034] like Figures 1 to 6 An embodiment of the multi-stage fracturing tool of the present invention is shown. The multi-stage fracturing tool includes a fracturing string 1 and a ball seat assembly 2. In this embodiment, the ball seat assembly 2 includes at least two ball seat bodies 22, ball seat shear pins 23, and limiting components 3. Each ball seat body 22 can be sealed with a corresponding pressure ball 21 to achieve fracturing of the corresponding fracturing string 1; the ball seat shear pins 23 are connected between adjacent ball seat bodies 22; the limiting components 3 are located outside each ball seat body 22, and the matching parameters of each limiting component 3 are different. Each ball seat body 22 is limited and engaged with the corresponding fracturing string 1 through the limiting components 3. Its structure is simple and compact, can be used within the space of existing fracturing tools, and has high versatility and low cost.

[0035] Simultaneously, along the wellhead insertion direction of the ball seat assembly 2, the strength of the ball seat shear pin 23 gradually increases, while the pressure-bearing inner diameter 221 of each ball seat body 22 sealingly engages with the pressure-retaining ball 21 gradually decreases. This allows the first pressure-retaining ball 21 to enter the first ball seat body 22, and the last ball seat body 22 to be sheared by the ball seat shear pin 23 and first hooked onto the corresponding fracturing string 1. This ensures that each ball seat body 22 can be sequentially installed on the corresponding fracturing string 1, guaranteeing the smooth unsealing of subsequent fracturing strings 1, achieving multi-stage fracturing, and ensuring high fracturing reliability.

[0036] Furthermore, the limiting component 3 is a spiral limiting component, which includes a spiral groove 31 and a spiral boss 32. The spiral groove 31 is located inside the inner sleeve 12 of the fracturing string 1, and the spiral boss 32 is located outside the ball seat 22. In other embodiments, the spiral boss 32 may also be located inside the inner sleeve 12 of the fracturing string 1, and the spiral groove 31 may be located outside the ball seat 22.

[0037] In this embodiment, the matching parameters of the spiral groove 31 and the spiral boss 32 include the spiral width, spiral pitch, spiral length, number of spiral segments, and spiral direction. When fracturing is required, the fracturing string 1 is run into the wellbore along with the casing, and then a ball seat assembly 2 with ball seat bodies 22 having different matching parameters is deployed. Each group of fracturing strings 1 is unsealed when it matches the corresponding ball seat body 22. The ball seat assembly 2 passes through the fracturing string 1 when the spiral limiting component is mismatched until the corresponding fracturing string 1 is matched and unsealed, thus achieving precise multi-cluster fracturing.

[0038] The spiral limiting component of the present invention offers flexible and diverse adjustment of matching parameters, which greatly increases the number of fracturing stages and enables unlimited fracturing stages. At the same time, it eliminates the need to expand the number of fracturing stages through the pressure-bearing inner diameter 221 of the ball seat assembly 2, thus avoiding the problem of the number of fracturing stages being limited by the diameter of the ball during ball throwing.

[0039] Furthermore, the helical limiting component also includes meshing teeth 33. The meshing teeth 33 are located between the helical groove 31 and the helical boss 32. When the helical groove 31 and the helical boss 32 are matched, they mesh and lock together through the meshing teeth 33, thereby releasing the inner sliding sleeve 12 of the fracturing tubing string 1. The meshing teeth 33 prevent the helical groove 31 and the helical boss 32 from separating when the wellhead pressure is too high, thus preventing the fracturing hole 111 from opening properly and ensuring reliable release of the inner sliding sleeve 12.

[0040] like Figure 5 As shown, each ball seat 22 in this embodiment is provided with two sets of helical limiting components, which are arranged at intervals along the axis of the ball seat 22. The helical limiting component at the upper end is provided with meshing teeth 33. In other embodiments, the number of helical limiting components in each ball seat 22 can be adjusted according to the actual situation, such as one set, three sets, etc. At the same time, at least one set of helical limiting components is provided with meshing teeth 33 to ensure effective unsealing of the inner sliding sleeve 12.

[0041] In this embodiment, the number of spiral turns of the spiral groove 31 is greater than the number of spiral turns of the spiral boss 32 that matches the spiral groove 31, so that the spiral boss 32 passing through at any angle can be completely inserted into the matching spiral groove 31, thereby ensuring the smooth progress of subsequent fracturing.

[0042] like Figure 6 As shown, the fracturing string 1 includes an outer sleeve 11, an inner sliding sleeve 12, and a string shear pin 13. The outer sleeve 11 has a fracturing hole 111; the inner sliding sleeve 12 is installed at the position of the fracturing hole 111; and the string shear pin 13 is located between the outer sleeve 11 and the inner sliding sleeve 12. When fracturing is required, the inner sliding sleeve 12 engages with the corresponding ball seat 22 for limiting engagement, and the string shear pin 13 shears off when the inner sliding sleeve 12 is engaged with the corresponding ball seat 22, thereby opening the fracturing hole 111.

[0043] Furthermore, the fracturing string 1 also includes an axial limiting assembly 4, which includes a retaining ring 41, a retaining ring groove 42, and a limiting shoulder 43. The retaining ring 41 is located on the inner sliding sleeve 12, while the retaining ring groove 42 and the limiting shoulder 43 are both located on the outer sleeve 11. When the inner sliding sleeve 12 opens and moves downward, it drives the elastic claw 122 and the guide sleeve 123 to move downward together. When the guide sleeve 123 moves down to engage with the limiting shoulder 43, the retaining ring 41 engages with the retaining ring groove 42 to lock the axial position of the inner sliding sleeve 12 and prevent the inner sliding sleeve 12 from moving during subsequent operations.

[0044] Furthermore, the inner sliding sleeve 12 includes an opening sleeve 121, an elastic claw 122, and a guide sleeve 123 connected in sequence. The opening sleeve 121 is installed at the fracturing hole 111 of the outer sleeve 11 via a tubing shear pin 13. The tubing shear pin 13 shears off when the inner sliding sleeve 12 moves downward, thereby opening the fracturing hole 111. A retaining spring 41 is located at the bottom end of the elastic claw 122. The bottom end of the guide sleeve 123 engages with a limiting shoulder 43 when the inner sliding sleeve 12 moves downward. Furthermore, a retaining ring 124 is provided between the opening sleeve 121 and the elastic claw 122, and a pressure-bearing inner diameter 221 is located on the retaining ring 124. This design is compact and easy to disassemble.

[0045] In this embodiment, the pressure-retaining balls 21 are all soluble components that can be dissolved after the fracturing holes 111 are opened, ensuring that the opening components can be completely dissolved after the fracturing operation is completed. The ball seat body 22 can be made of alloy steel or soluble materials as needed to ensure the large diameter requirement of the entire wellbore. At the same time, the surfaces of the ball seat body 22 and the pressure-retaining balls 21 are coated with a high-strength, erosion-resistant ceramic coating to prevent erosion wear caused by fracturing other sections after the ball seat body 22 is attached.

[0046] In this embodiment, the outer casing 111 includes an upper connector 112, a central tube 113, and a lower connector 114 connected in sequence. The fracturing hole 111 is located at the upper end of the central tube 113. Its structure is simple and compact, and it is convenient for installation and maintenance.

[0047] like Figures 1 to 4 As shown, when the ball seat assembly 2 moves in the wellbore, the last ball seat body 22 will first match the expected corresponding fracturing tubing 1 and be hooked onto the inner sliding sleeve 12 by the limiting component 3. Through pressure build-up, the last ball seat body 22 will separate from the ball seat assembly 2, and the remaining ball seat assemblies 2 will continue to be pumped downwards. The last ball seat body 22 will hook onto the corresponding inner sliding sleeve 12 again and separate from the ball seat assembly 2 until all ball seat bodies 22 are matched and hooked onto the corresponding inner sliding sleeve 12, and the first stage of fracturing begins. After that, only the corresponding pressure build-up ball 21 needs to be put in to open the corresponding inner sliding sleeve 12 of the hooked ball seat body 22 to realize the fracturing of the corresponding stage.

[0048] like Figure 7As shown, the multi-stage fracturing method described in this embodiment includes the following steps:

[0049] 1) Deploy fracturing string 1 in the wellbore;

[0050] 2) Insert the pressure-blocking ball 21, which is sealed to the ball seat body 22 with the smallest pressure-bearing inner diameter 221, into the ball seat assembly 2, and pump the ball seat assembly 2 into the well.

[0051] 3) When all the ball seats 22 are in a limiting fit with the corresponding fracturing tubing 1 and the pressure-blocking ball 21 that is inserted into the well with the ball seat assembly 2 is released from the corresponding fracturing tubing 1, after the first stage of fracturing is completed, the pressure-blocking ball 21 that is in a sealing fit with the corresponding fracturing tubing 1 is sequentially inserted in the opposite direction of the ball seat assembly 2 entering the well to complete the multi-stage fracturing.

[0052] The fracturing method of the multi-stage segmented fracturing tool of the present invention also has the above-mentioned advantages, and is easy to operate and has high fracturing efficiency, effectively solving the problem of cumbersome construction of single-stage pump ball seat and the need to use large ground equipment.

[0053] Furthermore, if the number of fracturing stages exceeds the number of ball seats 22 in the ball seat assembly 2, after step 3), steps 2) and 3) are repeated for the upper fracturing string 1 located in the fracturing completion section until the target number of fracturing stages is completed. At this time, the ball seat assemblies 2 installed each time are pumped independently, meaning that this invention employs a method of sequentially pumping the ball seat assemblies 2 and ball-drop fracturing in a mutually cyclical manner, allowing ball seats 22 with the same inner diameter to circulate infinitely. This effectively solves the problem of limited fracturing stages in the ball-drop fracturing string 1, achieving unlimited fracturing stages.

[0054] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A multi-stage fracturing tool, comprising a fracturing tubing string and a ball seat assembly, characterized in that, The ball seat assembly includes at least two ball seat bodies that seal with the pressure-absorbing ball, a ball seat shear pin connecting adjacent ball seat bodies, and a limiting component disposed outside each ball seat body. The matching parameters of each limiting component are different, and each ball seat body is limited to the corresponding fracturing tubing string through the limiting component. Along the wellhead insertion direction of the ball seat assembly, the strength of the ball seat shear pin gradually increases, and the pressure-bearing inner diameter of each ball seat body that seals with the pressure-absorbing ball gradually decreases. The limiting component is a spiral limiting component, which includes a spiral groove and a spiral boss. The spiral groove and the spiral boss are respectively disposed on the ball seat and the fracturing string. The matching parameters of the spiral groove and the spiral boss include the spiral width, the spiral pitch, the spiral length, the number of spiral segments, and the spiral direction.

2. The multi-stage fracturing tool according to claim 1, characterized in that, The spiral limiting component also includes meshing teeth disposed between the spiral groove and the spiral boss, and the spiral groove and the spiral boss are engaged and clamped together by the meshing teeth.

3. The multi-stage fracturing tool according to claim 1, characterized in that, The spiral limiting component is at least two sets, and the two sets of spiral limiting components are arranged at intervals along the axis of the ball seat; when there are more than two sets of spiral limiting components, at least one set of spiral limiting components is provided with meshing teeth.

4. The multi-stage fracturing tool according to claim 1, characterized in that, The number of spiral turns in the spiral groove is greater than the number of spiral turns in the spiral boss that matches the spiral groove.

5. The multi-stage fracturing tool according to any one of claims 1 to 4, characterized in that, The fracturing string includes an outer sleeve with a fracturing hole, an inner sliding sleeve installed at the fracturing hole position, and a string shear pin disposed between the outer sleeve and the inner sliding sleeve. The inner sliding sleeve is limited to the corresponding ball seat body. The string shear pin cuts when the inner sliding sleeve is limited to the corresponding ball seat body to open the fracturing hole.

6. The multi-stage fracturing tool according to claim 5, characterized in that, It also includes an axial limiting component that restricts the axial position of the inner sliding sleeve after the fracturing hole is opened. The axial limiting component includes a retaining ring, a retaining ring groove, and a limiting shoulder. The retaining ring is disposed on the inner sliding sleeve, and the retaining ring groove and the limiting shoulder are both disposed on the outer sleeve. When the inner sliding sleeve moves down to the limiting shoulder, the retaining ring and the retaining ring groove engage in a limiting fit.

7. The multi-stage fracturing tool according to claim 6, characterized in that, The inner sliding sleeve includes an opening sleeve, an elastic claw, and a guide sleeve connected in sequence. The opening sleeve is installed at the fracturing hole position of the outer sleeve by the tubing shear pin. The retaining spring is located at the bottom end of the elastic claw. The bottom end of the guide sleeve engages with the limiting shoulder when the inner sliding sleeve moves downward.

8. A fracturing method using a multi-stage fracturing tool as described in any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Deploy the fracturing tubing string in the wellbore; 2) Insert a pressure-retaining ball into the ball seat assembly, which is sealed to the ball seat body with the smallest pressure-bearing inner diameter, and pump the ball seat assembly into the well. 3) When all ball seats are in contact with the corresponding fracturing tubing and the pressure-blocking ball that enters the well with the ball seat assembly releases the corresponding fracturing tubing and completes the first stage of fracturing, pressure-blocking balls that are in contact with the corresponding fracturing tubing are sequentially inserted in the opposite direction of the ball seat assembly entering the well to complete multi-stage fracturing.

9. The fracturing method for multi-stage segmented fracturing according to claim 8, characterized in that, If the number of fracturing stages exceeds the number of ball seats in the ball seat assembly, after step 3), repeat steps 2) and 3) on the upper fracturing string located in the fracturing completion section until the target number of fracturing stages is completed.

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