Toe end sliding sleeve

Abstract

The toe end sliding sleeve comprises an outer cylinder and an inner cylinder capable of axially sliding relative to the outer cylinder, and a fracturing cavity and a pressure transmitting cavity which are isolated from each other are formed between the outer cylinder and the inner cylinder; a rupture disk is mounted on the inner cylinder, and the position of the rupture disk is opposite to that of the fracturing cavity; a fracturing hole is formed in the outer cylinder, the fracturing hole comprises a reducing hole which is gradually reduced inwards from inside to outside in the radial direction of the outer cylinder, and a fracturing plug is installed in the reducing hole in a matched mode. By means of the toe end sliding sleeve, the machining requirement of the rupture disc on the toe end sliding sleeve is lowered, and the rupture error of the toe end sliding sleeve can be allowed to range from 30% to 50%. Meanwhile, even if the rupture disc is fractured in the pressure testing process, normal pressure testing can be conducted on the shaft, the pressure testing pressure value can be set at will within the range of being higher than the maximum pressure bearing of the rupture disc and lower than the normal pressure bearing of a casing pipe, and shaft pressure testing operation under the ideal target pressure can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas well fracturing, and in particular to a toe sliding sleeve. Background Art

[0002] At present, the fracturing sleeves used in oil and gas well fracturing operations are mostly designed for the multi-stage fracturing environment of horizontal oil wells. Each production layer is used as a fracturing and production channel by a sleeve, and packers are used above and below the sleeve to block the layer. The bottom sleeve in the fracturing completion production string is generally composed of a differential pressure sleeve. Under the action of the differential pressure, the differential pressure sleeve opens to establish the first layer of fracturing channel.

[0003] Conventional differential pressure sleeves are mainly used in open hole staged fracturing operations, and full wellbore pressure testing is not required. If in a cementing environment, cement slurry can easily intrude into the hydraulic cavity through the pressure transmission hole, thus affecting the opening of the differential pressure sleeve.

[0004] If there is a requirement to conduct a full wellbore pressure test before opening, it is often difficult for a conventional differential pressure sleeve to reach the required test pressure due to the limitation of the shear force of the shear pins.

[0005] In addition, in the application of rupture disk toe sleeve, due to the large differences in the processing of rupture disks, it is possible that the rupture disk has already ruptured during the cementing process, making it impossible to perform pressure testing operations in the wellbore. Utility Model Content

[0006] The purpose of the present application is to provide a toe end sliding sleeve that can be used for wellbore pressure testing operations, has low processing requirements for rupture disks, and can achieve automatic opening of the toe end sliding sleeve after the pressure testing operation is completed.

[0007] In order to achieve the above-mentioned purpose, the utility model provides a toe end sliding sleeve, comprising an outer cylinder and an inner cylinder that can slide axially relative to the outer cylinder, wherein a mutually isolated fracturing chamber and a pressure transmission chamber are provided between the outer cylinder and the inner cylinder;

[0008] A rupture disk is installed on the inner cylinder, and the rupture disk is opposite to the fracturing chamber;

[0009] The outer cylinder is provided with a fracturing hole, and the fracturing hole comprises a gradually shrinking hole which gradually shrinks inwards from the inside to the outside along the radial direction of the outer cylinder, and a fracturing plug is matched and installed in the gradually shrinking hole.

[0010] In an optional embodiment, the inner cylinder is concentrically arranged with the outer cylinder, a groove for mounting the inner cylinder is arranged on the inner wall of the outer cylinder, and the inner wall of the inner cylinder is flush with the inner wall of the outer cylinder.

[0011] In an optional embodiment, the inner cylinder includes a boss block located in the middle for sealing and spacing the fracturing chamber and the pressure transmission chamber, and the boss block is opposite to the position of the fracturing hole and completely blocks the fracturing hole.

[0012] In an optional embodiment, based on the fact that the boss block completely blocks the fracturing hole and at least a portion of it fits against the inner wall of the outer cylinder, the fitting area of ​​the boss block in the fracturing cavity is smaller than the fitting area of ​​the boss block in the pressure transmission cavity.

[0013] In an optional embodiment, the fracturing hole comprises a through hole opened on the side wall of the outer cylinder and integrally penetrates the outer cylinder in the radial direction;

[0014] The hole wall of the fracturing hole is a smooth hole surface, and the outer side wall of the fracturing plug is lined with a flexible sealing layer.

[0015] In an optional embodiment, the fracturing hole comprises a tapered hole structure that expands inwardly and contracts outwardly, the fracturing plug comprises a frustum structure, and the axial thickness of the fracturing plug is less than the side wall thickness of the outer cylinder.

[0016] In an optional embodiment, the fracturing hole comprises a concentric cone hole, and the fracturing plug comprises a concentric cone.

[0017] In an optional embodiment, the fracturing hole comprises an eccentric cone hole, and the fracturing plug comprises an eccentric cone.

[0018] In an optional embodiment, a pressure transmission hole is opened through the side wall of the outer cylinder, and the pressure transmission hole is communicated with the cavity body of the pressure transmission chamber.

[0019] In an optional embodiment, the fracturing holes include a plurality of holes, the plurality of fracturing holes are evenly spaced in the axial direction of the outer cylinder, and the fracturing plugs correspond to the fracturing holes one by one.

[0020] The toe end sliding sleeve in the present application, by providing a tapered hole and matching the installation of a fracturing plug in the tapered hole, can, during the pressure test, when the pressure inside the toe end sliding sleeve is greater than the formation pressure, tightly fit the fracturing plug and insert it into the fracturing hole with the outer top; at the same time, after the wellbore pressure test is completed, combined with the state that the wellbore pressure is less than the formation pressure after the wellhead pressure relief, the pressure plug is pushed back under the action of the formation pressure to break away from the tight fit on the fracturing hole, so that the toe end sliding sleeve automatically opens without delay.

[0021] Through the toe end sliding sleeve of the utility model, the processing requirements of the rupture disk on the toe end sliding sleeve are reduced, and the rupture error thereof can be allowed to be above 30% to 50%.

[0022] At the same time, even if the rupture disk ruptures during the pressure test, the wellbore can also be pressure tested normally. The pressure test pressure value can be set arbitrarily within the range of higher than the maximum pressure of the rupture disk and lower than the normal pressure of the casing, so that the wellbore pressure test operation can be achieved at the ideal target pressure.

[0023] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a schematic diagram of the structure of the toe sleeve in this application.

[0026] icon:

[0027] 1-outer cylinder; 11-fracturing hole; 12-fracturing plug; 13-groove; 14-pressure transmission hole;

[0028] 2-inner cylinder; 21-boss block;

[0029] 3-Fracturing chamber;

[0030] 4-pressure transmission chamber;

[0031] 5- Rupture disk. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0034] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] The toe sleeve in the present application is mainly used in the fracturing operation of oil and gas wells. Specifically, by changing the structure of the toe sleeve of the existing fracturing disc type, the pressure test requirement of the wellbore before the fracturing operation is met. Furthermore, it is not affected by whether the rupture disc 5 is ruptured. Regardless of whether the rupture disc 5 is ruptured or not, an effective pressure test operation can be performed before the fracturing operation.

[0036] It is often difficult for the existing pressure difference type sliding sleeve to reach the required pressure test pressure due to the limitation of the shear force of the shear pin. At the same time, based on the fact that the rupture disk 5 of the existing rupture disk 5 type toe end sliding sleeve has large processing differences and is easy to rupture before the pressure test operation, by arranging special-shaped holes and special-shaped plugs on the toe end sliding sleeve, the pressure test operation can be carried out first, and then, under the premise of the pressure test, the pressure test pressure can be increased to ensure the effectiveness of the wellbore pressure test operation.

[0037] During the pressure test, the rupture disk 5 is first ruptured under the action of the internal pressure of the casing. Then, as the test pressure value increases, the test pressure value is greater than the formation pressure value, so that the special-shaped plug is pressed in the fracturing hole 11 under the action of the internal pressure of the casing, and as the test pressure value increases, the pressure becomes tighter and tighter, thereby blocking the fracturing channel formed by the fracturing hole 11. Finally, after the pressure test is completed, the wellbore is depressurized, and under the action of the formation pressure being greater than the internal pressure of the casing, the special-shaped plug is pushed back and separated from the special-shaped hole, the fracturing channel is opened, and the fracturing operation is completed.

[0038] The toe end sliding sleeve in the utility model does not limit the processing accuracy of the rupture disk 5. Since the internal pressure of the casing is required to break through the constraints of the fracturing disk during the pressure test, the rupture disk 5 can be allowed to have a certain rupture error, and even its rupture error can be allowed to be above 30%-50%, so as to improve the pressure test conditions before fracturing.

[0039] Furthermore, by considering the test pressure to be within a range higher than the maximum bearing pressure of the rupture disk 5 and lower than the maximum bearing pressure of the casing, the test pressure value can be arbitrarily set to a certain extent, that is, within a certain range lower than the maximum bearing pressure of the casing, which can increase the pressure value of the wellbore pressure test, ensure the effectiveness of the wellbore pressure test, and also enhance the flexibility of the wellbore pressure test operation.

[0040] See also Figure 1The toe end sliding sleeve in the utility model has a main structure including an outer tube 1 and an inner tube 2. The inner tube 2 can slide relative to the outer tube 1 and along the axial direction of the outer tube 1. A fracturing chamber 3 and a pressure transmission chamber 4 isolated from each other are arranged between the outer tube 1 and the inner tube 2.

[0041] A rupture disk 5 is installed on the inner cylinder 2, and the rupture disk 5 is located opposite to the fracturing chamber 3; a fracturing hole 11 is arranged on the outer cylinder 1, and the fracturing hole 11 includes a gradually shrinking hole that gradually shrinks from the inside to the outside along the radial direction of the outer cylinder 1, and a fracturing plug 12 is matched and installed in the gradually shrinking hole.

[0042] Through the toe end sleeve in the present application, during the pressure test, the pressure filled in the casing can act on the rupture disk 5 and destroy the rupture disk 5, so that the lumen of the toe end sleeve is connected with the cavity of the fracturing chamber 3, and at the same time, combined with the conduction between the pressure transmission chamber 4 and the external formation pressure, and the state that the pressure test pressure is greater than the formation pressure, the inner tube 2 slides axially downward relative to the outer tube 1, and the boss block 21 on the inner tube 2 is separated from the blockage of the fracturing hole 11, so that the lumen of the casing, the fracturing chamber 3 and the space near the side of the inner tube 2 of the fracturing plug 12 are connected, and the fracturing plug 12 is pressed in the gradually shrinking hole that gradually retracts from the inside to the outside along the radial direction of the outer tube 1. As the pressure of the pressure test gradually increases, the fracturing plug 12 is pressed tighter and tighter in the shrinking hole, and no fracturing action is constituted.

[0043] After the pressure test operation is completed, the pressure in the casing is reduced by depressurizing the wellbore. The external formation pressure is greater than the internal pressure of the casing after the pressure relief. Based on the destruction of the rupture disk 5, the external formation pressure acts on the fracturing plug 12, so that the fracturing plug 12 is pushed back and released from the compressed state in the fracturing hole 11, and the external formation and the inside of the casing are connected through the drilled fracturing hole 11, that is, the fracturing channel, to complete the overall fracturing operation.

[0044] By means of the gradually shrinking hole radially contracting from the inside to the outside of the outer tube 1 and the fracturing plug 12 matched and installed in the shrinking hole, the fracturing channel can be blocked during the pressure test operation, and the formation pressure can push the fracturing plug 12 back to open the fracturing channel after pressure relief. The normal pressure test operation can be achieved, the processing requirements of the rupture disk 5 can be reduced, and the pressure test pressure can be increased and adjusted within a certain range, which greatly improves the fracturing conditions of existing oil and gas wells.

[0045] In one specific embodiment, the inner cylinder 2 is concentrically arranged with the outer cylinder 1 , and a groove 13 for mounting the inner cylinder 2 is arranged on the inner wall of the outer cylinder 1 , and the inner wall of the inner cylinder 2 is flush with the inner wall of the outer cylinder 1 .

[0046] Through this arrangement, the inner cylinder 2 can reliably slide axially relative to the outer cylinder 1, and the groove 13 provided on the inner wall of the outer cylinder 1 for mounting the inner cylinder 2 can regulate the sliding direction of the inner cylinder 2. At the same time, it can play the role of sliding limit to prevent the inner cylinder 2 from excessively moving under the action of the internal pressure test.

[0047] In this embodiment, the inner tube 2 includes a boss block 21 located in the middle for sealing the fracturing chamber 3 and the pressure transmission chamber 4. The main purpose of the boss block 21 is to seal and isolate the fracturing chamber 3 and the pressure transmission chamber 4, and to block the fracturing plug 12 at the same time.

[0048] In the initial state, that is, before the pressure test, the position of the boss block 21 is opposite to the position of the fracturing hole 11, and the fracturing hole 11 is completely blocked. In the blocked state, the edge of the boss block 21 fits with the inner wall of the outer tube 1, which can meet the requirement of isolating the fracturing chamber 3 and the pressure transmission chamber 4 under the premise of blocking the fracturing channel.

[0049] Based on this, on the basis that the boss block 21 completely blocks the fracturing hole 11 and the edge of the boss block 21 fits against the inner wall of the outer tube 1, the area of ​​the boss block 21 fitting against the inner wall of the outer tube 1 in the fracturing chamber 3 is smaller than the area of ​​the boss block 21 fitting against the inner wall of the outer tube 1 in the pressure transmission chamber 4.

[0050] With this arrangement, after the rupture disk 5 is destroyed at the beginning of the pressure test, the boss block 21 can move down a short distance synchronously with the inner tube 2, so that the fracturing chamber 3 is connected with the fracturing hole 11, and the internal pressure test medium is pressurized to contact the fracturing plug 12, thereby improving the effectiveness and reliability of the operation.

[0051] In another specific embodiment, the fracturing hole 11 includes a through hole opened on the side wall of the outer tube 1 and integrally penetrates the outer tube 1 in the radial direction, which can facilitate the transmission of internal and external pressures and facilitate the sealing of the fracturing plug 12 in the fracturing hole 11 .

[0052] The hole wall of the fracturing hole 11 is a smooth hole surface, which can facilitate smooth movement during the compression and push-back process. At the same time, the outer wall of the fracturing plug 12 is lined with a flexible sealing layer, which can ensure the sealing and compression effect of the fracturing plug 12 on the fracturing hole 11 during the pressure test.

[0053] The fracturing hole 11 in the present embodiment includes a tapered hole structure that expands inward and contracts outward in the radial direction of the toe end sliding sleeve, and the fracturing plug 12 includes a frustum structure. The tapered hole in the above-mentioned form and the fracturing plug 12 with a frustum structure installed in the fracturing hole 11 can ensure the external pressure sealing and compression state of the fracturing plug 12 in the fracturing hole 11 during the pressure test. Furthermore, after the wellbore is depressurized, the fracturing plug 12 with a frustum structure can be pushed back from the small end to the large end under the action of the formation pressure to form a relatively stable and reliable push-back action.

[0054] Furthermore, the axial thickness of the fracturing plug 12 is smaller than the side wall thickness of the outer tube 1, that is, the axial thickness of the cone is smaller than the through-hole depth of the fracturing hole 11, which can facilitate the creation of a gap between the fracturing plug 12 and the fracturing hole 11 during the push-back of the fracturing plug 12 after pressure relief, thereby greatly shortening the conduction between the external formation pressure and the internal pressure of the casing.

[0055] In one specific implementation form, the fracturing hole 11 includes a concentric cone hole, and the fracturing plug 12 includes a concentric cone, which can effectively seal and compress the concentric cone in the fracturing hole 11.

[0056] In another specific implementation, the fracturing hole 11 includes an eccentric cone hole, and the fracturing plug 12 includes an eccentric cone, which can facilitate the formation of a gap between the fracturing plug 12 and the fracturing hole 11 during the push-back process, making the fracturing action more direct.

[0057] A pressure transmission hole 14 is opened through the side wall of the outer tube 1, and the pressure transmission hole 14 is connected to the cavity of the pressure transmission chamber 4, which can constitute the conduction between the external formation pressure and the pressure of the pressure transmission chamber 4, and can ensure that the inner tube 2 can slide downward effectively and reliably during the pressure test.

[0058] The utility model includes a plurality of fracturing holes 11, and the plurality of fracturing holes 11 are evenly spaced in the axial direction of the outer tube 1. The fracturing plugs 12 correspond to the fracturing holes 11 one by one, which can enhance the uniformity of pressure conduction, and the fracturing action can be achieved when any fracturing plug 12 is out of the compression state of the fracturing hole 11, making the fracturing operation more stable and reliable.

[0059] The working principle of the toe sleeve is:

[0060] Pi represents formation pressure; Pt represents wellbore pressure; Pp represents the rupture pressure of the rupture disk; Ps represents the test pressure; Pmax represents the maximum bearing pressure of the casing;

[0061] The test pressure Ps is 80% to 90% of the maximum bearing pressure Pmax of the casing; the rupture pressure Pp of the rupture disk is 80% of the test pressure Ps.

[0062] 1. When Ps>Pp, the rupture disk opens; when Ps<Pi, the pressure in the fracturing chamber is less than the pressure in the pressure transmission chamber, and the inner cylinder does not move;

[0063] 2. When Ps continues to increase in pressure, Ps>Pi, the pressure in the fracturing chamber is greater than the pressure in the pressure transmission chamber, the inner tube moves downward, and the position of the boss block exceeds the fracturing hole and the fracturing plug; at this time, as long as Ps is greater than Pi, due to the difference in the inner and outer areas of the fracturing plug, the inside and outside of the casing are not connected, the fracturing channel cannot be opened, and the test pressure can be increased to any value of Pp-Pmax.

[0064] 3. When Ps < Pi after pressure relief, due to the difference in inner and outer cross-sectional areas of the fracturing plug on the fracturing hole, the fracturing channel is immediately opened and fracturing operations can be carried out.

[0065] The following is an example of the specific implementation process:

[0066] Pi=60MPa, Pmax=80MPa, Ps=64MPa, Pp=50MPa

[0067] 1. Pressurize the wellbore, Pt→20MPa→30MPa→40MPa<Pp, the rupture disk is intact

[0068] 2. Continue to pressurize the wellbore, Pt = Pp = 50MPa, and the rupture disk opens

[0069] 3. The wellbore continues to be pressurized, Pt = 55MPa < 60MPa, the fracturing chamber pressure is less than the pressure transmission chamber pressure, and the fracturing channel does not open;

[0070] 4. The wellbore continues to be pressurized, Pt = 60MPa ≤ 60MPa, and the fracturing channel does not open;

[0071] 5. The wellbore continues to be pressurized, Pt = 61MPa>Pi, the fracturing chamber pressure> the pressure transmission chamber pressure, and the inner tube moves downward;

[0072] 6. The wellbore continues to be pressurized, Pt→62MPa→64MPa→70MPa→80MPa, the fracturing chamber pressure is greater than the pressure transmission chamber pressure, the inner tube moves downward, due to the presence of the fracturing plug, the fracturing plug is pressed tighter and tighter, and the fracturing channel still cannot be opened;

[0073] 7. When the pressure in the wellbore is relieved and Pt is less than Pi, the fracturing plug opens and the fracturing channel opens due to the cross-sectional area difference of the fracturing plug.

[0074] It should be noted that, in the absence of conflict, the features in the embodiments of this application may be combined with each other.

[0075] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A toe end sliding sleeve, characterized in that: It comprises an outer cylinder and an inner cylinder which can slide axially relative to the outer cylinder, and a fracturing chamber and a pressure transmission chamber which are isolated from each other are arranged between the outer cylinder and the inner cylinder; A rupture disk is installed on the inner cylinder, and the rupture disk is opposite to the fracturing chamber; The outer cylinder is provided with a fracturing hole, and the fracturing hole comprises a gradually shrinking hole which gradually shrinks inwards from the inside to the outside along the radial direction of the outer cylinder, and a fracturing plug is matched and installed in the gradually shrinking hole.

2. The toe end sliding sleeve according to claim 1, characterized in that: The inner cylinder is arranged concentrically with the outer cylinder, a groove for installing the inner cylinder is arranged on the inner wall of the outer cylinder, and the inner wall of the inner cylinder is flush with the inner wall of the outer cylinder.

3. The toe end sliding sleeve according to claim 1, characterized in that: The inner cylinder comprises a boss block located in the middle for sealing and spacing the fracturing chamber and the pressure transmission chamber. The boss block is opposite to the position of the fracturing hole and completely blocks the fracturing hole.

4. The toe end sliding sleeve according to claim 3, characterized in that: Based on the fact that the boss block completely blocks the fracturing hole and at least a portion of it fits with the inner wall of the outer cylinder, the fitting area of ​​the boss block in the fracturing cavity is smaller than the fitting area of ​​the boss block in the pressure transmission cavity.

5. The toe end sliding sleeve according to claim 1, characterized in that: The fracturing hole comprises a through hole opened on the side wall of the outer cylinder and integrally penetrates the outer cylinder in the radial direction; The hole wall of the fracturing hole is a smooth hole surface, and the outer side wall of the fracturing plug is lined with a flexible sealing layer.

6. The toe end sliding sleeve according to claim 5, characterized in that: The fracturing hole comprises a tapered hole structure that expands inward and contracts outward, the fracturing plug comprises a frustum structure, and the axial thickness of the fracturing plug is smaller than the side wall thickness of the outer cylinder.

7. The toe end sliding sleeve according to claim 6, characterized in that: The fracturing hole comprises a concentric cone hole, and the fracturing plug comprises a concentric cone.

8. The toe end sliding sleeve according to claim 6, characterized in that: The fracturing hole comprises an eccentric cone hole, and the fracturing plug comprises an eccentric cone.

9. The toe end sliding sleeve according to any one of claims 1 to 8, characterized in that: A pressure transmission hole is opened through the side wall of the outer cylinder, and the pressure transmission hole is communicated with the cavity body of the pressure transmission cavity.

10. The toe end sliding sleeve according to any one of claims 1 to 8, characterized in that: The fracturing holes include a plurality of holes, and the plurality of fracturing holes are evenly spaced in the axial direction of the outer cylinder, and the fracturing plugs correspond to the fracturing holes one by one.

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