Staged fracturing method and differential pressure sliding sleeve

Abstract

The invention belongs to the technical field of fracturing processes, and particularly relates to a staged fracturing method and a differential pressure sliding sleeve. The staged fracturing method comprises the following steps that S1, a plurality of differential pressure sliding sleeves provided with different numbers of locking cylinders are put into a well to a preset position, and the number of the locking cylinders corresponds to the number of times of pressurization and pressure relief of opening of the differential pressure sliding sleeves; and S2, pressurization and pressure relief are conducted repeatedly, opening of the differential pressure sliding sleeves and fracturing of the corresponding stratums are completed in sequence, and therefore staged fracturing is completed. According to the staged fracturing method provided by the invention, an underground tool for opening each differential pressure sliding sleeve does not need to be put into a well, so that the construction steps are saved.

Description

Technical Field

[0001] This invention belongs to the field of fracturing technology, specifically relating to a segmented fracturing method and a differential pressure sliding sleeve. Background Technology

[0002] With the development of unconventional oil and gas resources, horizontal well staged fracturing technology has become one of the most effective means of developing unconventional oil and gas reservoirs.

[0003] Currently, in the process of staged fracturing operations, downhole tools such as opening tools, ball droppers, or pump-driven perforation gun bridge plugs need to be deployed sequentially from upstream to downstream to open the differential pressure sleeves of each stage. This is because the differential pressure sleeves in the existing technology will open once they are subjected to pressure. Therefore, it is necessary to use downhole tools to seal the wellbore in stages so that each differential pressure sleeve can be opened and fracturing can be carried out from upstream to downstream. The general process of segmented pressure operations in existing technology is as follows: Multiple differential pressure sleeves are connected in series and inserted into the well to a predetermined position using a tubing string; downhole tools are deployed into the tubing string to seal the connection between the first-stage and second-stage differential pressure sleeves; pressure is applied to the tubing string to open the first-stage differential pressure sleeve and initiate fracturing of the segmented formation; the downhole tools used for sealing between the first and second-stage differential pressure sleeves are cleared, and downhole tools are deployed again to seal the connection between the second and third-stage differential pressure sleeves; temporary plugging material is deployed into the tubing string to seal the first-stage differential pressure sleeve; pressure is applied to the tubing string to open the second-stage differential pressure sleeve and initiate fracturing of the segmented formation…

[0004] This means that after each fracturing stage is completed, the pump needs to be stopped and downhole tools need to be run, resulting in a long fracturing process and low efficiency.

[0005] In addition, due to the deployment of a large number of downhole tools, subsequent well cleaning and plugging operations are required due to dissolved substances and wellbore blockages, which further prolongs the duration of the staged fracturing process and leads to low efficiency.

[0006] Therefore, there is an urgent need to develop a segmented fracturing method that can save time in segmented fracturing operations. Summary of the Invention

[0007] To address the technical problems described above, this invention aims to provide a segmented fracturing method that can save time during segmented fracturing operations.

[0008] The present invention also proposes a differential pressure sliding sleeve, which is applicable to the segmented fracturing method proposed in the present invention and can save the construction time of segmented fracturing.

[0009] According to the present invention, a staged fracturing method is provided, comprising the following steps:

[0010] S1. Insert multiple differential pressure sleeves, each equipped with a different number of locking cylinders, into the well to a predetermined position. The number of locking cylinders corresponds to the number of times the differential pressure sleeve is opened for pressurization and depressurization.

[0011] S2. Repeat the pressurization and depressurization process multiple times to sequentially open each differential pressure sliding sleeve and fracturing the corresponding formation, thereby completing the segmented fracturing.

[0012] In one specific embodiment, in S2, after each formation fracturing is completed, the corresponding differential pressure sleeve is sealed.

[0013] In one specific embodiment, the differential pressure sleeve is sealed by temporarily plugging material being placed inside it.

[0014] According to the present invention, a differential pressure sleeve is also provided, comprising:

[0015] The outer cylinder has flow guide holes.

[0016] A differential pressure cylinder that seals the guide hole by means of a first pin located inside the outer cylinder; and

[0017] At least one locking cylinder is installed inside the outer cylinder by a second pin, the locking cylinders being spaced out downstream of the differential pressure cylinder, and the pressure threshold of the locking cylinder being less than the starting pressure of the first pin.

[0018] In one specific embodiment, the axial distance between the locking cylinder and the differential pressure cylinder is not less than the diameter of the first pin, and the axial distance between two adjacent locking cylinders is not less than the diameter of the second pin.

[0019] In one specific embodiment, the pressure threshold of each of the locking cylinders gradually decreases from upstream to downstream.

[0020] In one specific embodiment, a fifth seal is provided between the second pin and the outer cylinder.

[0021] In one specific embodiment, the outer cylinder includes a first cylinder section and a second cylinder section, wherein the inner diameter of the first cylinder section is larger than the inner diameter of the second cylinder section;

[0022] The differential pressure cylinder includes a third cylinder section and a fourth cylinder section. The outer diameter of the third cylinder section is larger than the outer diameter of the fourth cylinder section. A first sealing element and a second sealing element are provided between the third cylinder section and the outer cylinder. The first sealing element and the second sealing element are respectively located on the upper and lower sides of the flow guide hole.

[0023] The locking cylinder includes a fifth cylinder section and a sixth cylinder section. The outer diameter of the fifth cylinder section is larger than that of the sixth cylinder section. The fifth cylinder section is disposed between the fourth cylinder section and the outer cylinder. A third sealing element is disposed between the fifth cylinder section and the fourth cylinder section. The sixth cylinder section is located inside the second cylinder section. A fourth sealing element is disposed between the sixth cylinder section and the second cylinder section.

[0024] In one specific embodiment, the axial clearance between the third cylinder section and the fifth cylinder section is not less than the diameter of the first pin.

[0025] In one specific embodiment, the axial distance from the first seal to the upper end of the guide hole is d1, the axial interval between the locking cylinder and the differential pressure cylinder is d2, the axial interval between two adjacent locking cylinders is d3, and d1≥d2+d3.

[0026] In one specific embodiment, the axial distance between the downstream locking cylinder and the second cylinder section is d4, d1. <d2+d3+d4。

[0027] Compared with the prior art, the advantages of this application are as follows.

[0028] This invention includes an outer cylinder and a differential pressure cylinder and a locking cylinder disposed within the outer cylinder. The differential pressure cylinder is constructed to have a differential pressure surface, and when subjected to pressure, it can move axially relative to the outer cylinder and axially abut against the locking cylinder. The locking cylinder does not have a differential pressure surface; that is, the force-bearing surfaces at its upper and lower ends are equal in area. When the locking cylinder is subjected to pressure, it deforms and expands radially, increasing the friction between the outer wall of the locking cylinder and the inner wall of the outer cylinder. When this pressure increases to a certain value, the force exerted by the differential pressure on the differential pressure cylinder to move axially downward is insufficient to push the locking cylinder to move axially relative to the outer cylinder. Furthermore, as long as the pressure exceeds this certain value, the locking cylinder cannot move axially relative to the outer cylinder, thus preventing the differential pressure cylinder from moving relative to the outer cylinder to open the guide hole. This is because the increase in frictional resistance after the outer cylinder and the locking cylinder are in contact is much greater than the increase in the axial thrust experienced by the differential pressure cylinder. This application describes this specific pressure value as a critical pressure value.

[0029] The critical pressure value of the locking cylinder is less than the starting pressure value of the first pin. Pressure is applied to the differential pressure sleeve. When the pressure increases to exceed the starting pressure value of the first pin, the differential pressure sleeve moves axially relative to the outer cylinder and abuts against the locking cylinder. At this point, the differential pressure sleeve remains blocked from the guide hole. Because the starting pressure value of the first pin is greater than the critical pressure value of the locking cylinder, the differential pressure sleeve cannot move further after abutting against the locking cylinder. Only when the pressure is released below the critical pressure value of the locking cylinder can it be pushed to move, thus opening the guide hole. Therefore, by setting different numbers of locking cylinders, the differential pressure sleeve can be opened under different pressure increases and decreases. Controlling the opening of the differential pressure sleeve corresponding to different formation segments in this way avoids the need to deploy downhole tools to open the differential pressure sleeve, thereby avoiding pump shutdown, reducing process steps, improving efficiency, and eliminating the need for well cleaning and plugging operations, further reducing process steps and saving time. Attached Figure Description

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

[0031] Figure 1 A schematic diagram showing a differential pressure sleeve with a locking cylinder according to the present invention is shown;

[0032] Figure 2 A schematic diagram showing the differential pressure sleeve with two locking cylinders according to the present invention is provided;

[0033] Figures 3-5 Showing Figure 2 The diagram shown illustrates the working principle of the differential pressure sleeve applying multiple pressures.

[0034] Figure 6 A schematic diagram showing a differential pressure sleeve with multiple locking cylinders according to the present invention is provided;

[0035] Figure 7 The diagram shows a differential pressure sliding sleeve with multiple locking cylinders installed after being inserted into the well in the segmented fracturing method according to the present invention.

[0036] In the picture:

[0037] 1. Outer cylinder; 11. Guide hole; 12. First cylinder section; 13. Second cylinder section; 2. Differential pressure cylinder; 21. Third cylinder section; 22. Fourth cylinder section; 3. Locking cylinder; 31. Fifth cylinder section; 32. Sixth cylinder section; 33. Seventh cylinder section; 41. Upper connector; 42. Lower connector; 81. First sealing element; 82. Second sealing element; 83. Third sealing element; 84. Fourth sealing element; 85. Fifth sealing element; 86. Sixth sealing element; 87. Seventh sealing element; 88. Eighth sealing element; 91. First pin; 92. Second pin; 100. Differential pressure sleeve; 101. Differential pressure sleeve with one locking cylinder; 102. Differential pressure sleeve with two locking cylinders; 103. Differential pressure sleeve with three locking cylinders; 104. Differential pressure sleeve with four locking cylinders; 200. Downhole tubing string.

[0038] 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

[0039] The invention will now be described with reference to the accompanying drawings.

[0040] It should be noted that the direction near the wellhead after the differential pressure sliding sleeve of the present invention is inserted into the well is described as "upstream," "front end," or similar terms, i.e. Figure 1 Above; the direction away from the wellhead after the differential pressure sliding sleeve is inserted into the well is described as "downstream," "rear end," or similar terms, i.e. Figure 1 Below.

[0041] In this application, the differential pressure sliding sleeve provided by the present invention is not limited to use in horizontal wells, but can also be used in vertical wells, inclined wells and other working conditions.

[0042] Example 1:

[0043] Figure 1 The structure of the differential pressure sleeve 100 according to the present invention is shown. Figure 1 As shown, the differential pressure sleeve 100 includes an outer cylinder 1, a differential pressure cylinder 2, and a locking cylinder 3.

[0044] The outer cylinder 1 is generally cylindrical in shape, and at least one flow guide hole 11 is provided on the cylinder wall of the outer cylinder 1, which connects the inner cavity of the outer cylinder 1 to the outside. In this embodiment, multiple flow guide holes 11 are arranged at intervals along the circumferential direction on the cylinder wall of the outer cylinder 1.

[0045] The differential pressure cylinder 2 is generally cylindrical in shape. It is fixed inside the outer cylinder 1 by a first pin 91 and blocks the guide hole 11. The pressure-bearing areas at the upper and lower ends of the differential pressure cylinder 2 are different, which allows the differential pressure cylinder 2 to move axially relative to the outer cylinder 1 under the action of the pressure difference between the upper and lower ends when it is subjected to pressure.

[0046] The locking cylinder 3 is generally cylindrical in shape. It is fixed inside the outer cylinder 1 by the second pin 92 and is spaced downstream of the differential pressure cylinder 2, meaning there is an axial gap between the locking cylinder 3 and the differential pressure cylinder 2. The upper and lower ends of the locking cylinder 3 have the same pressure-bearing area, meaning that the locking cylinder 3 will not move axially on its own after being subjected to pressure.

[0047] The basic operating principle of the differential pressure sleeve 100 provided by this invention is based on the principle that the locking cylinder 3, under a certain pressure, undergoes slight elastic deformation and other stresses, resulting in radial expansion and tight contact with the inner wall of the outer cylinder 1, thus forming a lock and causing the movement to fail. In experiments, it was found that in existing technologies, the inner cylinder with the differential pressure surface of the sleeve cannot be opened due to excessive pressure; it can only be opened smoothly after the pressure is reduced. This is because the inner cavity of the inner cylinder expands radially outward under pressure, undergoing elastic deformation and contacting the outer cylinder, thereby increasing the friction between the inner and outer cylinders. This pressure causing the inner cylinder to expand radially outward has a specific value. When this specific value is exceeded, the inner cylinder cannot move axially relative to the outer cylinder even under greater force, because the increase in frictional resistance after the inner and outer cylinders are in contact is much greater than the increase in the differential pressure force on the inner cylinder. This specific value is defined and described in this invention as a critical pressure value.

[0048] Therefore, in the prior art, it is usually necessary to avoid the pressure from exceeding the pressure critical value in order to ensure that the inner cylinder with the pressure differential surface can move axially relative to the outer cylinder, thereby opening the sliding sleeve.

[0049] This application, however, utilizes this principle in reverse. In this application, the critical pressure value of the locking cylinder 3 is less than the starting pressure value of the first pin 91. The starting pressure value of the first pin 91 refers to the pressure value at which the differential pressure cylinder 2 can be sheared by the pressure difference force after being subjected to pressure.

[0050] This design allows for pressure integrity testing of the entire well casing. When the differential pressure sleeve 100 is inserted into the well along with other well casings and a pressure integrity test is required, pressure can be applied to the well casing without worrying about accidental opening of the differential pressure sleeve 100. When the pressure inside the differential pressure sleeve 100 increases to the starting pressure value of the first pin 91, the differential pressure cylinder 2 moves downward relative to the outer cylinder 1 under the differential pressure force of its upper and lower differential pressure surfaces until the lower end of the differential pressure cylinder 2 axially abuts against the upper end of the locking cylinder 3. At this point, the starting pressure value of the first pin 91 is greater than the critical pressure value of the locking cylinder 3. After the differential pressure cylinder 2 abuts against the locking cylinder 3, it cannot move downward further, and the guide hole 11 remains within the sealing range of the differential pressure cylinder 2. Therefore, even if the pressure is further increased, the guide hole 11 will not open prematurely, thus preventing premature opening of the guide hole 11.

[0051] Example 2:

[0052] According to the present invention, based on Embodiment 1, the number of locking cylinders 3 can be set to multiple. In this embodiment, as... Figure 2 As shown, a differential pressure cylinder 2 is installed inside the outer cylinder 1 via a first pin 91 to block the flow guide hole 11. Two locking cylinders 3 are also installed inside the outer cylinder 1 via two second pins 92, with the two locking cylinders 3 spaced apart downstream of the differential pressure cylinder 2. For ease of explanation, this application names each locking cylinder 3 and its corresponding second pin 92, from upstream to downstream, as first-level locking cylinder 3, second-level locking cylinder 3, first-level second pin 92, and second-level second pin 92, respectively.

[0053] Furthermore, the axial distance between the primary locking cylinder 3 and the differential pressure cylinder 2 is not less than the diameter of the first pin 91. This ensures that during the first pressurization process, when the differential pressure cylinder 2 moves relative to the outer cylinder 1 to abut against the primary locking cylinder 3, it can shear off the first pin 91, preventing the differential pressure sleeve 100 from failing to open. The axial distance between two adjacent locking cylinders 3 is not less than the diameter of the second pin 92. In other words, the axial distance between the primary locking cylinder 3 and the secondary locking cylinder 3 is not less than the diameter of the second pin 92 of the primary locking cylinder 3. This ensures that during the second pressurization process, when the differential pressure cylinder 2 pushes the primary locking cylinder 3 to abut against the secondary locking cylinder 3, it can shear off the second pin 92 of the primary locking cylinder 3, preventing the differential pressure sleeve 100 from failing to open.

[0054] In this embodiment, the pressure critical value of each locking cylinder 3 gradually decreases from upstream to downstream. That is, the pressure critical value of the first-stage locking cylinder 3 is greater than the pressure critical value of the second-stage locking cylinder 3. Furthermore, the pressure critical value of the differential pressure cylinder 2 is greater than the starting pressure value of the first pin 91, thereby preventing the differential pressure cylinder 2 from moving smoothly.

[0055] In one specific embodiment, the pressure values ​​in this application are arranged from largest to smallest as follows: the pressure critical value of the differential pressure cylinder 2, the starting pressure value of the first pin 91, the pressure critical value of the first-stage locking cylinder 3, the starting pressure value of the first-stage second pin 92, the pressure critical value of the second-stage locking cylinder 3, and the starting pressure value of the second-stage second pin 92.

[0056] By setting different numbers of locking cylinders 3, the differential pressure sleeve 100 can be set to open after a specific number of pressurization cycles as needed.

[0057] like Figure 3 As shown, during the first pressurization, when the pressure inside the differential pressure sleeve 100 exceeds the starting pressure value of the first pin 91, the differential pressure cylinder 2 moves downward relative to the outer cylinder 1 until it axially abuts against the first-stage locking cylinder 3, and... Figure 3The first pin 91 shown in section A is sheared. At this time, the guide hole 11 is still within the sealing range of the differential pressure cylinder 2, so the guide hole 11 is still in the closed state. At this time, the pressure inside the differential pressure sleeve 100 is greater than the pressure critical value of the first-stage locking cylinder 3. No matter how the pressure increases, the first-stage locking cylinder 3 can prevent the differential pressure cylinder 2 from moving further downward relative to the outer cylinder 1. Therefore, the pressure can continue to increase, as long as the pressure does not exceed the pressure bearing limit of the materials of each part. After pressurization is completed, the pressure is released.

[0058] After the first pressurization is completed, a second pressurization is performed, such as... Figure 4 As shown, during the second pressurization, when the pressure inside the differential pressure sleeve 100 exceeds the starting pressure value of the first-stage second pin 92, the differential pressure cylinder 2 pushes the first-stage locking cylinder 3 to move axially relative to the outer cylinder 1 until it axially abuts against the second-stage locking cylinder 3, and... Figure 4 The first-stage second pin 92 shown in section B is sheared. At this time, the guide hole 11 is still within the sealing range of the differential pressure cylinder 2, so the guide hole 11 is still in the closed state. At this time, the pressure inside the differential pressure sleeve 100 is greater than the pressure critical value of the second-stage locking cylinder 3. No matter how the pressure increases, the second-stage locking cylinder 3 can prevent the differential pressure cylinder 2 and the first-stage locking cylinder 3 from moving further downward relative to the outer cylinder 1. Therefore, the pressure can continue to be increased for pressurization, as long as the pressure does not exceed the material bearing limit of each part. After pressurization is completed, the pressure is released.

[0059] After the second pressurization is completed, when it is necessary to open the differential pressure sleeve 100, pressurize the differential pressure sleeve 100, such as... Figure 5 As shown, when the pressure inside the differential pressure sleeve 100 is greater than the starting pressure value of the second secondary pin 92, the differential pressure cylinder 2 pushes the first-stage locking cylinder 3 and the second-stage locking cylinder 3 to move downward relative to the outer cylinder 1, and... Figure 5 The second secondary pin 92 shown in section C is cut off. At this time, the guide hole 11 has been removed from the sealing range of the differential pressure cylinder 2, and the guide hole 11 is in the open state, thus completing the opening of the differential pressure sleeve 100.

[0060] According to a preferred embodiment of the present invention, a fifth sealing element 85 is provided between the first pin 91 and the outer cylinder 1, and between the second pin 92 and the outer cylinder 1.

[0061] According to one specific embodiment of the present invention, the outer cylinder 1 includes a first cylinder section 12 and a second cylinder section 13, wherein the first cylinder section 12 is coaxially disposed at the upper end of the second cylinder section 13. The inner diameter of the first cylinder section 12 is larger than the inner diameter of the second cylinder section 13, and the outer diameters of the two are equal.

[0062] The differential pressure cylinder 2 includes a third cylinder section 21 and a fourth cylinder section 22, with the third cylinder section 21 coaxially disposed at the upper end of the fourth cylinder section 22. The outer diameter of the third cylinder section 21 is larger than the outer diameter of the fourth cylinder section 22, while their inner diameters are equal. The differential pressure cylinder 2 is located inside the first cylinder section 12. A first sealing element 81 and a second sealing element 82 are disposed between the outer wall of the third cylinder section 21 and the outer cylinder 1, respectively located on the upper and lower sides of the guide hole 11. A first pin 91 is located below the guide hole 11, also positioned between the first sealing element 81 and the second sealing element 82.

[0063] The locking cylinder 3 includes a fifth cylinder section 31 and a sixth cylinder section 32. Furthermore, the fifth cylinder section 31 and the sixth cylinder section 32 are connected by a seventh cylinder section 33. That is, the locking cylinder 3 includes a fifth cylinder section 31, a seventh cylinder section 33 and a sixth cylinder section 32 arranged coaxially from top to bottom.

[0064] The outer diameters of the fifth cylindrical section 31 and the seventh cylindrical section 33 are equal, and the outer diameter of the fifth cylindrical section 31 is greater than the outer diameter of the sixth cylindrical section 32. The inner diameter of the sixth cylindrical section 32 is equal to the inner diameter of the seventh cylindrical section 33, and the inner diameter of the fifth cylindrical section 31 is greater than the inner diameter of the sixth cylindrical section 32.

[0065] The fifth section 31 of the first-stage locking cylinder 3 is located between the fourth section 22 and the first section 12. That is, the outer wall of the fifth section 31 is in contact with the inner wall of the outer cylinder 1, the inner wall of the fifth section 31 is in contact with the outer wall of the fourth section 22, and a third sealing element 83 is provided between the inner wall of the fifth section 31 and the outer wall of the fourth section 22.

[0066] The fifth section 31 of the secondary locking cylinder 3 is located between the sixth section 32 of the primary locking cylinder 3 and the first section 12, and a fourth sealing element 84 is provided between the fifth section 31 of the secondary locking cylinder 3 and the sixth section 32 of the primary locking cylinder 3.

[0067] The sixth section 32 of the secondary locking cylinder 3 is located inside the second section 13, and a fourth sealing element 84 is provided between the outer wall of the sixth section 32 and the inner wall of the second section 13.

[0068] According to the present invention, the axial clearance between the fourth section 22 of the differential pressure cylinder 2 and the seventh section 33 of the first-stage locking cylinder 3 is equal to the axial clearance between the third section 21 of the differential pressure cylinder 2 and the fifth section 31 of the first-stage locking cylinder 3, and is not less than the diameter of the first pin 91.

[0069] According to the present invention, such as Figure 2As shown, the axial distance from the first seal 81 to the upper end of the diversion hole 11 is d1. The axial interval between the locking cylinder 3 and the differential pressure cylinder 2, that is, the axial interval between the fourth cylinder section 22 of the differential pressure cylinder 2 and the seventh cylinder section 33 of the first-stage locking cylinder 3 is d2. The axial interval between two adjacent locking cylinders 3, that is, the axial interval between the sixth cylinder section 32 of the first-stage locking cylinder 3 and the seventh cylinder section 33 of the second-stage locking cylinder 3 is d3. d1 ≥ d2 + d3, thereby preventing the accidental opening of the diversion hole 11.

[0070] According to the present invention, the axial interval between the most downstream locking cylinder 3 and the second cylinder section 13, that is, the axial interval between the seventh cylinder section 33 of the second-stage locking cylinder 3 and the second cylinder section 13 is d4. d1 < d2 + d3 + d4, thereby enabling the normal opening of the diversion hole 11.

[0071] Embodiment III

[0072] According to the present invention, as Figure 6 shown, the number of locking cylinders 3 can be set to multiple according to needs.

[0073] Embodiment IV

[0074] According to the present invention, a staged fracturing method is provided, including the following steps.

[0075] S1. Lower multiple differential pressure sleeves 100 provided with different numbers of locking cylinders 3 into the well to a predetermined position, and the number of locking cylinders 3 corresponds to the number of pressurization and pressure relief operations for opening the differential pressure sleeve 100.

[0076] Specifically, as Figure 7 shown, in this embodiment, multiple differential pressure sleeves 100 provided with different numbers of locking cylinders 3, such as a differential pressure sleeve 101 provided with one locking cylinder, a differential pressure sleeve 102 provided with two locking cylinders, a differential pressure sleeve 103 provided with three locking cylinders, a differential pressure sleeve 104 provided with four locking cylinders, etc., are connected in series from top to bottom on the downhole string 200.

[0077] It should be noted that the differential pressure sleeves 100 provided with different numbers of locking cylinders 3 are not limited to being arranged in sequence, but their sequence can be arranged arbitrarily according to needs.

[0078] S2. Repeat pressurization and pressure relief multiple times to sequentially complete the opening of each differential pressure sleeve 100 and the fracturing of the corresponding formation, thereby completing staged fracturing.

[0079] It is easy to understand that the end of the downhole string 200 ( Figure 7 the rightmost end of the downhole string 200 in

[0080] During the initial pressurization and depressurization process, when pressurization is applied to the downhole tubing 200, if the pressure exceeds the activation pressure of the first pin 91, all differential pressure sleeves 100 with their differential pressure cylinders 2 will move downwards relative to the outer cylinder 1 until they abut against the first-stage locking cylinder 3. At this point, the pressure is greater than the critical pressure value of the first-stage locking cylinder 3, therefore the differential pressure cylinders 2 cannot move further downwards, and all differential pressure sleeves 100 will be in a closed state. This initial pressurization is equivalent to performing a pressure integrity test on the entire well casing.

[0081] After the pressure integrity test of the entire well casing is completed, there are two operating methods to implement the second pressurization and depressurization process. One is to directly depressurize to zero and then repressurize until the pressure reaches the starting pressure value of the second pin 92 of the first-stage locking cylinder 3; the other is to depressurize to between the starting pressure value of the second pin 92 of the first-stage locking cylinder 3 and the pressure critical value of the first-stage locking cylinder 3. Then, the differential pressure cylinders 2 of all differential pressure sleeves 100 push the first-stage locking cylinder 3 to shear the first-stage second pin 92 and move downward. At this time, the guide hole 11 of the differential pressure sleeve 100 with one locking cylinder 3 will open, while the other differential pressure sleeves 100 with multiple locking cylinders 3 will remain closed due to the presence of the second-stage locking cylinders 3. Therefore, by continuing to pressurize, fracturing can be performed on the formation corresponding to the differential pressure sleeve 100 with one locking cylinder 3, while the formations corresponding to the other differential pressure sleeves 100 will not be affected.

[0082] Then, the pressurization and depressurization process is repeated in sequence according to the above steps, and the differential pressure sliding sleeves 100 with different numbers of locking cylinders 3 are opened in sequence, and the fracturing of the formation corresponding to each differential pressure sliding sleeve 100 is completed.

[0083] In one specific embodiment, after each pressurization and depressurization completes the fracturing of a certain segment of the formation, the guide hole 11 of the differential pressure sleeve 100 corresponding to that segment is sealed, so that the next pressurization and depressurization process can proceed smoothly.

[0084] Preferably, the flow guide hole 11 is sealed by placing a temporary plugging material into the differential pressure sleeve 100. It is easy to understand that the temporary plugging material is a substance that, after being placed from the wellhead, can move to the position of the flow guide hole 11 of the differential pressure sleeve 100 and seal the flow guide hole 11 for a certain period of time. This is well known to those skilled in the art and will not be described in detail here.

[0085] Furthermore, the guide hole 11 of the differential pressure sleeve 100 is constructed as a tapered hole, with the larger side opening facing inward, which makes it easier for the temporary plugging material to seal the guide hole 11.

[0086] With this configuration of the present invention, it is not necessary to run in additional downhole tools to open the differential pressure sleeve 100 during the fracturing process, thereby reducing the steps required for the fracturing process, saving construction time, and eliminating the need for subsequent well cleaning and clogging operations due to dissolved substances, wellbore blockage, etc. of the downhole tools.

[0087] In the description of this invention, it should be understood 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.

[0088] 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.

[0089] 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.

[0090] 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 staged fracturing method, characterized in that, Includes the following steps: S1. Insert multiple differential pressure sleeves (100) with different numbers of locking cylinders (3) into the well to a predetermined position. The number of locking cylinders (3) corresponds to the number of times the differential pressure sleeves (100) are opened for pressurization and depressurization. S2. Repeat the pressurization and depressurization process multiple times to sequentially open each differential pressure sleeve (100) and fracturing the corresponding formation, thereby completing the segmented fracturing.

2. The staged fracturing method according to claim 1, characterized in that, In S2, after each section of formation fracturing is completed, the corresponding differential pressure sleeve (100) is sealed.

3. The staged fracturing method according to claim 2, characterized in that, The differential pressure sleeve (100) is sealed by temporarily plugging material.

4. A differential pressure sleeve suitable for the staged fracturing method according to any one of claims 1 to 3, characterized in that, include: The outer cylinder (1) is provided with a flow guide hole (11); A differential pressure cylinder (2) that blocks the flow guide hole (11) is installed inside the outer cylinder (1) by a first pin (91); And at least one locking cylinder (3) is provided in the outer cylinder (1) by means of a second pin (92), the locking cylinder (3) is provided downstream of the differential pressure cylinder (2) at intervals, and the pressure critical value of the locking cylinder (3) is less than the starting pressure value of the first pin (91).

5. The differential pressure sliding sleeve according to claim 4, characterized in that, The pressure threshold of each locking cylinder (3) gradually decreases from upstream to downstream.

6. The differential pressure sliding sleeve according to claim 4, characterized in that, The axial distance between the locking cylinder (3) and the differential pressure cylinder (2) is not less than the diameter of the first pin (91), and the axial distance between two adjacent locking cylinders (3) is not less than the diameter of the second pin (92).

7. The differential pressure sliding sleeve according to claim 4, characterized in that, The outer cylinder (1) includes a first cylinder section (12) and a second cylinder section (13), wherein the inner diameter of the first cylinder section (12) is larger than the inner diameter of the second cylinder section (13); The differential pressure cylinder (2) includes a third cylinder section (21) and a fourth cylinder section (22). The outer diameter of the third cylinder section (21) is larger than the outer diameter of the fourth cylinder section (22). A first sealing element (81) and a second sealing element (82) are provided between the third cylinder section (21) and the outer cylinder (1). The first sealing element (81) and the second sealing element (82) are located on the upper and lower sides of the guide hole (11), respectively. The locking cylinder (3) includes a fifth cylinder section (31) and a sixth cylinder section (32). The outer diameter of the fifth cylinder section (31) is larger than the outer diameter of the sixth cylinder section (32). The fifth cylinder section (31) is disposed between the fourth cylinder section (22) and the outer cylinder (1). A third sealing element (83) is disposed between the fifth cylinder section (31) and the fourth cylinder section (22). The sixth cylinder section (32) is located inside the second cylinder section (13). A fourth sealing element (84) is disposed between the sixth cylinder section (32) and the second cylinder section (13).

8. The differential pressure sliding sleeve according to claim 7, characterized in that, The axial gap between the third cylindrical section (21) and the fifth cylindrical section (31) is not less than the diameter of the first pin (91).

9. The differential pressure sliding sleeve according to claim 8, characterized in that, The axial distance from the first seal (81) to the upper end of the guide hole (11) is d1, the axial interval between the locking cylinder (3) and the differential pressure cylinder (2) is d2, the axial interval between two adjacent locking cylinders (3) is d3, and d1≥d2+d3.

10. The differential pressure sliding sleeve according to claim 9, characterized in that, The axial distance between the downstream locking cylinder (3) and the second cylinder section (13) is d4, d1 <d2+d3+d4。

Images