A partial double sleeve assembly and method of connecting the same

Abstract

This invention discloses a partially double-layer casing assembly, comprising: a casing assembly, an upper valve assembly, and a lower valve assembly; the upper and lower valve assemblies are fixedly fitted onto the casing assembly; one end of the casing assembly is connected to the upper valve assembly, and the other end is connected to the lower valve assembly; the casing assembly includes at least one casing group; the casing group includes an outer casing and an inner casing; the inner casing is fitted inside the outer casing and the inner casing and the outer casing are concentrically arranged; after the inner casing and the outer casing are combined, the upper valve assembly is connected to one end of the inner casing to form a first cylinder, and the lower valve assembly is connected to the other end of the inner casing to form a second cylinder, the first cylinder and the second cylinder are connected; an annular space is formed between the outer casing and the inner casing; the annular space is filled with hydraulic oil. This invention also discloses a connection method for the partially double-layer casing assembly. The partially double-layer casing assembly of this invention has strong operability and a simple process flow, which can simplify the wellbore structure and save casing.

Description

Technical Field

[0001] This invention relates to the field of cementing casing, and more specifically, to a partially double-layer casing assembly and its connection method. Background Technology

[0002] Casing serves as a barrier separating the formation from the wellbore during drilling. Oil reservoir casing is the most fundamental element of an oil and gas well. Damage to the oil reservoir casing that cannot be repaired signifies the abandonment of the oil and gas well and the loss of fixed assets. Oil reservoir casing is constantly subjected to the high pressure of the oil reservoir and the corrosive effects of gases and liquids, as well as repeated exposure to external forces from various well workover operations and production enhancement measures. The main causes of its damage are as follows:

[0003] (1) Poor quality and low strength of the casing itself; (2) Poor cementing quality and weak sealing; (3) Corrosion by water, chemicals and microorganisms; (4) Geological tectonic movement and lithological effects around the casing; (5) Damage to the casing caused by high-pressure water injection; (6) The impact of sand production in oil, gas and water wells; (7) Damage to the casing caused by improper well workover operations.

[0004] During drilling and oil production, many casing failure points occur in gypsum-salt layers and nearby formations. In gypsum-salt layers, the pressure from the overlying strata and the expansion of the salt layer upon contact with water cause creep, resulting in plastic flow and compression towards the wellbore center. This creates an abnormal external extrusion force that standard casing cannot withstand, leading to deformation or collapse. This severely impacts the lifespan of oil and gas wells, crude oil production, and oilfield development, causing significant economic losses.

[0005] The common approach to solving casing failure problems is 1) to use refined thick-walled casing; or 2) to run a double casing system, i.e., the technical casing is run to the bottom of the salt layer, and then the entire well is run with the oil layer casing or a tailpipe is attached above the salt layer. However, the first method cannot significantly improve the ability to resist uneven external loads or combined loads of uniform and uneven external loads; the second method has huge drilling costs.

[0006] Based on this, a local double-layer combined casing for oil-injectable paste-salt layers is studied. This double-layer combined casing process is highly operable and has a simple process flow. It can simplify the wellbore structure, save casing, reduce casing costs, and reduce cementing costs, which has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a partial double-layer sleeve assembly and its connection method.

[0008] A partial double-layer sleeve assembly disclosed in this embodiment of the invention includes: a sleeve assembly, an upper valve assembly, and a lower valve assembly;

[0009] The upper valve assembly and the lower valve assembly are fixedly fitted onto the sleeve assembly, and the upper valve assembly and the lower valve assembly are spaced apart along the axial direction of the sleeve assembly;

[0010] One end of the sleeve assembly is connected to the upper valve assembly, and the other end is connected to the lower valve assembly;

[0011] The sleeve assembly includes at least one sleeve group; the sleeve group includes an outer sleeve and an inner sleeve; the inner sleeve is sleeved inside the outer sleeve and the inner sleeve and the outer sleeve are concentrically arranged.

[0012] After the inner sleeve and the outer sleeve are combined, the upper valve assembly is connected to one end of the inner sleeve to form a first cylinder, and the lower valve assembly is connected to the other end of the inner sleeve to form a second cylinder. The first cylinder and the second cylinder are connected.

[0013] An annular space is formed between the outer sleeve and the inner sleeve; the annular space is filled with hydraulic oil.

[0014] Furthermore, the upper valve assembly includes an upper valve sealing joint and an upper valve sealing sleeve;

[0015] The upper valve sealing sleeve is fixedly fitted onto the outside of one end of the outer sleeve, and the upper valve sealing joint is fixedly fitted into the upper valve sealing sleeve.

[0016] Furthermore, the upper valve sealing joint and the upper valve sealing sleeve are sealed together.

[0017] Furthermore, the upper valve sealing joint is fixedly connected to one end of the inner sleeve by a coupling to form the first cylinder.

[0018] Furthermore, the partial double-layer sleeve assembly also includes an inner sleeve coupling; the inner sleeve coupling connects to the upper valve sealing joint of the upper valve assembly.

[0019] Furthermore, the sleeve assembly includes at least two sleeve groups and a coupling for fixed connection between adjacent sleeve groups.

[0020] Furthermore, the lower valve assembly includes an inner lower valve body and an outer lower valve body;

[0021] The lower valve outer body is fixedly fitted onto the outside of the other end of the outer sleeve, and the lower valve inner body is fixedly fitted into the lower valve outer body; a lower valve inner limiting sleeve is provided between the lower valve inner body and the lower valve outer body, and the lower valve inner limiting sleeve is tightly connected to the lower valve inner body.

[0022] Furthermore, the lower valve inner body is fixedly connected to the other end of the inner sleeve by a coupling to form a second cylinder.

[0023] Furthermore, the partial double-layer sleeve assembly also includes a three-strapped connector; the three-strapped connector is sealed to the lower valve assembly.

[0024] The connection method of the partial double-layer sleeve assembly disclosed in the embodiments of the present invention includes the following steps:

[0025] The inner body of the lower valve is fitted onto the outer body of the lower valve, and the inner and outer bodies of the lower valve are fixed with the inner limiting sleeve of the lower valve to form the lower valve assembly; the three-thread connector is assembled into the lower valve assembly and then lowered into the well, so that the lower end of the three-thread connector is connected to the first oil layer casing in the well.

[0026] The casing assembly is lowered into the well and connected to the lower valve assembly. The annulus space between the inner and outer casing of the casing assembly is filled with hydraulic oil.

[0027] The upper valve sealing joint is lowered into the well and connected to the inner casing of the casing assembly. The upper valve sealing sleeve is lowered into the well and fitted onto the upper valve sealing joint, and the upper valve sealing sleeve is sealed to the outer casing of the casing assembly.

[0028] The inner casing coupling is lowered into the well and connected to the upper valve sealing joint. The second oil layer casing is then lowered and connected to the inner casing coupling.

[0029] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0030] The partial double-layer casing assembly process of the present invention is highly operable and has a simple process flow. It can simplify the well structure, save casing, reduce casing costs, reduce cementing costs, reduce the cost of drilling new wells and working over wells, enable effective oilfield development, avoid casing deformation, extend the life of oil and gas wells, ensure oil and gas production, extend the service life of oil and gas wells, and improve the overall benefits of oil and gas development.

[0031] The partial double-layer sleeve assembly of the present invention is designed with a lower valve inner limiting sleeve, which is fastened to the outer surface of the lower valve inner body by a pin, which can limit the turning displacement of the three-thread connector after reaching the rated torque.

[0032] The partial double-layer sleeve assembly of the present invention is designed with a rigid stabilizer, which is installed between the outer sleeve and the inner sleeve. One rigid stabilizer is installed for every two inner sleeves to keep the inner sleeve in a centered position.

[0033] The partial double-layer sleeve assembly of the present invention uses 15W-40 (not limited to a single grade) hydraulic oil between the inner sleeve and the outer sleeve to better ensure that the load transmitted from the outer sleeve to the inner sleeve through the liquid medium is uniform, while simplifying the construction process.

[0034] The partial double-layer sleeve assembly of the present invention is designed with a three-thread connector. Its upper end is connected to the outer body of the lower valve and the inner body of the lower valve through internal and external threads, and the lower valve is sealed by a sealing ring to fill the hydraulic oil. The lower end of the three-thread connector is threaded to the oil layer sleeve to realize the connection between the double-layer combined sleeve and the oil layer sleeve.

[0035] The partial double-layer casing assembly of the present invention is designed with an upper valve sealing sleeve, which forms a seal with the upper valve sealing joint through a sealing ring, which can effectively block the filling hydraulic oil and prevent the cementing slurry outside the outer casing from crossing layers. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the upper structure of a partial double-layer sleeve assembly according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a partial double-layer sleeve assembly according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the auxiliary structure for calculating the sleeve length according to an embodiment of the present invention.

[0040] [List of Labels in the Attached Image]

[0041] 1-Inner sleeve coupling, 2-Upper valve sealing joint, 3-Upper valve sealing sleeve, 4-Outer sleeve, 5-Coupling, 6-Inner sleeve, 7-Rigid centralizer, 8-Lower valve inner body, 9-Lower valve outer body, 10-Lower valve inner limit sleeve, 11-Three-lock connector, 12-Sealing ring, 13-Pin, 14-Hydraulic oil, 201-Upper valve assembly, 801-Lower valve assembly, 15-First cylinder, 16-Second cylinder, 17-Annular space, 18-Second annular space, T-Upper end, B-Lower end. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0043] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0044] See Figures 1-2 As shown, this embodiment provides a partial double-layer sleeve assembly, including: a sleeve assembly, an upper valve assembly 201 and a lower valve assembly 801 of the inner sleeve. The upper valve assembly 201 and the lower valve assembly 801 are fixedly fitted onto the sleeve assembly, and the upper valve assembly 201 and the lower valve assembly 801 are spaced apart along the axial direction of the sleeve assembly; one end of the sleeve assembly is connected to the upper valve assembly 201, and the other end is connected to the lower valve assembly 801; the sleeve assembly includes at least one sleeve group; the sleeve group includes an outer sleeve 4 and an inner sleeve 6; the inner sleeve 6 is sleeved inside the outer sleeve 4 and the inner sleeve 6 and the outer sleeve 4 are concentrically arranged.

[0045] Please continue to refer to Figure 2 After the inner sleeve 6 and the outer sleeve 4 are combined, the upper valve assembly 201 on the outer sleeve 4 is connected to one end of the inner sleeve 6 to form a first cylinder 15, and the lower valve assembly 801 on the outer sleeve 4 is connected to the other end of the inner sleeve 6 to form a second cylinder 16. The first cylinder 15 and the second cylinder 16 are connected. An annular space 17 is formed between the outer sleeve 4 and the inner sleeve 6. The annular space 17 is filled with hydraulic oil 14.

[0046] Specifically, a casing assembly can consist of only one casing group, namely, an outer casing and an inner casing. A casing assembly can also contain multiple casing groups, with the required length calculated based on the formation characteristics within the wellbore, thereby adjusting the number of casing groups; for example, the number of casing groups can be two, three, four, or more. For instance, a casing assembly can contain two casing groups: casing group I (consisting of an outer casing and an inner casing) and casing group II (consisting of an outer casing and an inner casing), connected by couplings. Because this design allows for convenient and quick adjustment of the casing assembly length, it also increases the versatility of the local double-layer casing assembly, enabling it to adapt to oil wells with varying formation thicknesses.

[0047] It should be noted that the inner sleeve 6 and the outer sleeve 4 need to be designed to be of equal length.

[0048] Specifically, according to Figure 3 The specific example shown illustrates how to calculate the lengths of the inner sleeve 6 and the outer sleeve 4:

[0049] (a) String structure:

[0050] Local double casing used in gypsum rock formation sections:

[0051] The outer sleeve has a diameter of 193.7 mm; the inner sleeve has a diameter of 139.7 mm.

[0052] (II) Calculation of Inner and Outer Layers:

[0053] For double-sleeve construction, one principle is that the outer sleeve and inner sleeve should be designed to be of equal length (equal length means that the lengths of the outer and inner sleeves after removing the external threads; when measuring the sleeves, only the length of the sleeve after removing the external threads needs to be measured). An example is given below.

[0054] For example, if the 139.7mm inner sleeve is shorter than the 193.7mm outer sleeve, the 139.7mm sleeve can be used to adjust the length.

[0055] Calculation principle: The calculation is based on the upper end face of the lower valve at 193.7.

[0056] Outer tube L 外 = 193.7mm sleeve length + C

[0057] Inner sleeve L 内 =A + B + 139.7mm sleeve length

[0058] 139.7mm sleeve length adjustment short sleeve L=L 外 -L 内 (Based on the construction experience of multiple wells, an additional 10cm was added to the theoretical calculations.)

[0059] A - Length of the lower valve inner tube extending out; B - Optimal sealing length of the sealing stub; C - Effective length of the upper valve.

[0060] Note: Considering that the bending of the inner sleeve during on-site construction may cause the actual length of the inner sleeve to be less than the theoretically calculated length, in order to ensure that the outer cap end face of the upper valve is within the sealing surface range of the sealing short section, an additional 10cm should be added to the theoretically adjusted short sleeve length.

[0061] (III) Calculation of the capacity of hydraulic oil filling the annular space:

[0062] V = (inner diameter cross-sectional area of ​​outer sleeve - outer diameter cross-sectional area of ​​inner sleeve) × length of outer sleeve.

[0063] Based on the example sleeve above, the calculation is as follows:

[0064]

[0065] In an embodiment of a casing assembly comprising multiple casing groups, a rigid centralizer 7 is installed on every two inner casings to ensure the centering of the multiple inner casings during installation and use.

[0066] Specifically, see Figure 2As shown, both the outer sleeve 4 and the inner sleeve 6 are tubular structures. The inner diameter of the outer sleeve 4 is larger than the inner diameter of the inner sleeve 6. Therefore, after the outer sleeve 4 and the inner sleeve 6 are combined, an annular space 17 is formed between the outer sleeve 4 and the inner sleeve 6. This annular space 17 is a space that surrounds the outer wall of the inner sleeve 6 circumferentially; the annular space 17 is filled with hydraulic oil 14. When the outer sleeve 4 is subjected to compressive forces, it can better ensure that the load transmitted from the outer sleeve 4 to the inner sleeve through the liquid medium is uniform, while simplifying the construction process. Preferably, the annular space 17 between the inner sleeve 6 and the outer sleeve 4 is filled with hydraulic oil 14 of grade 15W-40 (not limited to a single grade).

[0067] In an embodiment of a casing assembly comprising multiple casing assemblies, each casing assembly has its own annular space, and these annular spaces are interconnected.

[0068] It should be noted that the upper valve assembly 201 of the partial double-layer sleeve assembly is the upper part, and the lower valve assembly 801 is the lower part.

[0069] Specifically, see Figure 2 As shown, the upper valve assembly 201 and the lower valve assembly 801 are spaced apart along the axial direction of the outer sleeve 4. The upper valve assembly 201 is located at the upper end of the outer sleeve 4, and the lower valve assembly 801 is located at the lower end of the outer sleeve 4. The upper end of the outer sleeve 4 refers to the end of the outer sleeve 4 that is close to the wellhead after it is lowered into the oil well, and the lower end of the outer sleeve 4 refers to the end of the outer sleeve 4 that is close to the bottom of the well after it is lowered into the oil well. The upper end of the outer sleeve 4 is connected to the upper valve assembly 201, and the lower end of the outer sleeve 4 is connected to the lower valve assembly 801.

[0070] Specifically, the first cylinder 15, the second cylinder 16, and the inner sleeve that is not connected to the upper valve assembly 201 and the lower valve assembly 801 are connected to form an integral cylinder.

[0071] In an optional embodiment, the upper valve assembly 201 includes an upper valve sealing joint 2 and an upper valve sealing sleeve 3;

[0072] The upper valve sealing sleeve 3 is fixedly fitted onto the outside of one end of the outer sleeve 4, and the upper valve sealing joint 2 is fixedly fitted into the upper valve sealing sleeve 3.

[0073] In an optional embodiment, the upper valve sealing joint 2 and the upper valve sealing sleeve 3 are sealed together.

[0074] Specifically, such as Figure 1As shown, the upper valve sealing joint 2 is a tubular structure, and its inner diameter is the same as that of the inner sleeve 6. The upper valve sealing sleeve 3 is also a tubular structure. An annular groove is circumferentially provided on the inner side of the upper end of the upper valve sealing sleeve 3 at the position where it contacts the upper valve sealing joint 2. In this embodiment, there are two annular grooves arranged in parallel. A sealing ring 12 is installed inside the annular groove, forming a seal with the upper valve sealing joint 2. This effectively prevents the hydraulic oil 14 filling the annular space 17 from leaking upwards, further preventing the cementing slurry outside the outer sleeve 4 from spreading. The sealing ring 12 is preferably a conventional sealing ring 12 used in the art, such as an NBR nitrile rubber sealing ring 12.

[0075] Specifically, a threaded portion is provided at the position where the lower inner side of the upper valve sealing sleeve 3 contacts the upper outer wall of the outer sleeve 4. Correspondingly, a threaded portion is also provided on the upper outer wall of the outer sleeve 4 to achieve a threaded connection between the upper valve sealing sleeve 3 and the upper outer side of the outer sleeve 4.

[0076] Therefore, the inner diameter of the upper end of the upper valve sealing sleeve 3 is smaller than the inner diameter of the lower end of the upper valve sealing sleeve 3, and due to the change in inner diameter, a stepped surface A is formed on the inner wall of the upper valve sealing sleeve 3.

[0077] In an optional embodiment, the upper valve sealing joint 2 and one end of the inner sleeve 6 are fixedly connected by a coupling 5 to form the first cylinder 15.

[0078] Specifically, such as Figure 2 As shown, the upper end of the inner sleeve 6 is fixedly connected to the lower end of the upper valve sealing joint 2 by a coupling 5, forming the first cylinder 15.

[0079] In an optional embodiment, the partial double-layer sleeve assembly further includes an inner sleeve coupling 1; the inner sleeve coupling 1 is connected to the upper valve sealing joint 2 of the upper valve assembly 201.

[0080] Specifically, such as Figure 1 As shown, the inner sleeve coupling 1 is a tubular structure that connects to the upper end of the upper valve sealing joint 2. The inner wall of the inner sleeve coupling 1 is fixed to the outer wall of the upper end of the upper valve sealing joint 2 by a threaded connection. The inner sleeve coupling 1 itself is connected to the first cylinder 15.

[0081] In an optional embodiment, the lower valve assembly 801 includes an inner lower valve body 8 and an outer lower valve body 9.

[0082] The lower valve outer body 9 is fixedly fitted on the outside of the other end of the outer sleeve 4, and the lower valve inner body 8 is fixedly fitted inside the lower valve outer body 9; the lower valve inner body 8 and the lower valve outer body 9 are provided with a lower valve inner limiting sleeve 10, and the lower valve inner limiting sleeve 10 is tightly connected to the lower valve inner body 8.

[0083] In an optional embodiment, the lower valve inner body 8 and the other end of the inner sleeve 6 are fixedly connected by a coupling 5 to form a second cylinder 16.

[0084] Specifically, the inner diameter of the lower valve body 8 is the same as the inner diameter of the inner sleeve in the inner sleeve 6. For example... Figure 2 As shown, the lower end of the inner sleeve 6 is fixedly connected to the upper end of the inner body 8 of the lower valve by a coupling 5, forming the second cylinder 16.

[0085] Specifically, the lower valve outer body 9 is also a tubular structure, divided into an upper end, a lower end, and a middle end connecting the upper and lower ends. A threaded portion is provided at the position where the inner side of the upper end of the lower valve outer body 9 contacts the outer wall of the lower end of the outer sleeve 4. Correspondingly, a threaded portion is also provided on the outer wall of the lower end of the outer sleeve 4 to achieve a threaded connection between the lower valve outer body 9 and the outer side of the lower end of the outer sleeve 4.

[0086] Specifically, a lower valve inner body 8 and a lower valve outer body 9 are provided at their midpoints. The lower valve inner body 10 is fastened to the outer surface of the lower valve inner body 8 by a pin 13.

[0087] In an optional embodiment, the partial double-layer sleeve assembly further includes a three-strapped connector 11; the three-strapped connector 11 is sealed to the lower valve assembly 801.

[0088] Specifically, the inner diameter of the lower end of the outer body 9 of the lower valve is larger than the outer diameter of the lower end of the inner body 8 of the lower valve, forming a second annular space 18. A three-pronged connector 11, also a tubular structure, is inserted into the second annular space 18 at its upper end. Both the inner and outer walls of the upper end of the three-pronged connector 11 have threads, and these threads connect to the lower ends of the outer body 9 and the inner body 8 of the lower valve.

[0089] The lower valve inner limit sleeve 10 can limit the rotation displacement of the three-lock connector 11 after it reaches the rated torque.

[0090] Specifically, the upper end of the three-prong connector 11, on the side that contacts the lower valve outer body 9, is also provided with a circumferential annular groove. In this embodiment, there are two annular grooves, which are arranged in parallel. A sealing ring 12 is installed in the annular groove, and the sealing ring 12 forms a seal with the lower valve outer body 9, which can effectively prevent the hydraulic oil 14 filled in the annular space 17 from flowing downward and block the filling hydraulic oil 14. The sealing ring 12 is preferably a sealing ring 12 conventionally used in the art, such as an NBR nitrile rubber sealing ring 12.

[0091] Therefore, the inner diameter of the middle end of the lower valve outer body 9 is smaller than the inner diameter of the upper and lower ends of the lower valve outer body 9, and due to the change in inner diameter, two stepped surfaces are formed on the inner wall of the lower valve outer body 9.

[0092] The three-loop connector 11 has its own cylinder body connected to the second cylinder body 16.

[0093] The upper end of the three-thread connector 11 is connected to the lower valve outer body 9 and the lower valve inner body 8 through internal and external threads, and the lower valve assembly 801 is sealed by the sealing ring 12, which fills the hydraulic oil 14. The lower end of the three-thread connector 11 is connected to the second oil layer sleeve through threads, realizing the connection between the partial double-layer sleeve assembly and the second oil layer sleeve.

[0094] Preferably, such as Figure 2 As shown, the partial double-layer sleeve assembly also includes several rigid centralizers 7, which are installed on the outer wall of the lower valve inner body 8.

[0095] This embodiment provides a connection method for a partial double-layer sleeve assembly, including the following steps:

[0096] The inner body 8 of the lower valve is fitted onto the outer body 9 of the lower valve, and the inner limiting sleeve 10 of the lower valve is used to fix the inner body 8 and the outer body 9 of the lower valve to form the lower valve assembly 801; the three-strand connector 11 is assembled into the lower valve assembly 801 and then lowered into the well, so that the lower end of the three-strand connector 11 is connected to the first oil layer casing in the well.

[0097] The casing assembly is lowered into the well and connected to the lower valve assembly. The annular space 17 between the inner casing 6 and the outer casing 4 of the casing assembly is filled with hydraulic oil.

[0098] Lower the upper valve sealing joint 2 into the well and connect the upper valve sealing joint 2 to the inner casing 6 of the casing assembly. Lower the upper valve sealing sleeve 3 into the well, fit the upper valve sealing joint 2 into the upper valve sealing sleeve 3 and seal the upper valve sealing sleeve 3 to the outer casing 4 of the casing assembly.

[0099] Run the inner casing coupling 1 into the well and connect the inner casing coupling 1 to the upper valve sealing joint 2. Continue to run the second oil layer casing and connect it to the inner casing coupling 1.

[0100] Specifically, a partial double-casing cementing construction process is as follows: 1. Run the oil layer casing according to the designed pipe string connection, down to the designed length; 2. Connect the lower valve assembly 801 of the partial double-casing device; 3. Run the outer casing 4 and inner casing 6 sequentially according to the design (if there are multiple casing groups, run multiple outer casing 4 and inner casing 6); the inner casing and outer casing 4 are designed to be of equal length, and the threaded connection is made to the standard torque; add a rigid centralizer 7 for every two inner casings; 4. Fill the annulus space of the double-casing combination with 15W-40 (not limited to a single grade) hydraulic oil 14; 5. After running the double casing to the designed length, connect the upper valve assembly 201 and inner casing coupling 1 of the partial double-casing device; 6. Continue to run the oil layer casing to the designated position, and then carry out cementing according to the conventional cementing method.

[0101] In the above description of this embodiment, the upper end T and the lower end B refer to the end closer to the wellhead and the lower end closer to the bottom of the well after the component is lowered into the well.

[0102] It should be noted that the components or steps in the above embodiments can be interchanged, substituted, added, or deleted. Therefore, the combinations formed by these reasonable permutations and transformations should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the above embodiments.

[0103] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0104] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A partial double-layer sleeve assembly, characterized in that, include: Sleeve assembly, upper valve assembly, lower valve assembly, and three-thread connector; The upper valve assembly and the lower valve assembly are fixedly fitted onto the sleeve assembly, and the upper valve assembly and the lower valve assembly are spaced apart along the axial direction of the sleeve assembly; One end of the sleeve assembly is connected to the upper valve assembly, and the other end is connected to the lower valve assembly; The sleeve assembly includes at least one sleeve group; the sleeve group includes an outer sleeve and an inner sleeve; the inner sleeve is sleeved inside the outer sleeve and the inner sleeve and the outer sleeve are concentrically arranged. After the inner sleeve and the outer sleeve are combined, the upper valve assembly is connected to one end of the inner sleeve to form a first cylinder, and the lower valve assembly is connected to the other end of the inner sleeve to form a second cylinder. The first cylinder and the second cylinder are connected. An annular space is formed between the outer sleeve and the inner sleeve; the annular space is a closed space and is filled with hydraulic oil to ensure that the formation external extrusion force borne by the outer sleeve is evenly transmitted to the inner sleeve through the hydraulic oil. The three-pronged connector is sealed to the lower valve assembly to seal the hydraulic oil filling the annular space; The upper valve assembly includes an upper valve sealing joint and an upper valve sealing sleeve. The upper valve sealing sleeve is fixedly fitted onto the outer side of one end of the outer sleeve, and the upper valve sealing joint is fixedly fitted into the upper valve sealing sleeve. The upper valve sealing joint is connected to the inner sleeve of the sleeve assembly. The upper valve sealing joint and the upper valve sealing sleeve are sealed together to seal the hydraulic oil filling the annular space.

2. The partial double-layer sleeve assembly according to claim 1, characterized in that, The upper valve sealing joint is fixedly connected to one end of the inner sleeve by a coupling to form the first cylinder.

3. The partial double-layer sleeve assembly according to claim 2, characterized in that, The partial double-layer sleeve assembly also includes an inner sleeve coupling; the inner sleeve coupling connects to the upper valve sealing joint of the upper valve assembly.

4. The partial double-layer sleeve assembly according to claim 1, characterized in that, The sleeve assembly includes at least two sleeve groups and a coupling for fixing the connection between adjacent sleeve groups.

5. The partial double-layer sleeve assembly according to claim 1, characterized in that, The lower valve assembly includes an inner lower valve body and an outer lower valve body; The lower valve outer body is fixedly fitted onto the outside of the other end of the outer sleeve, and the lower valve inner body is fixedly fitted into the lower valve outer body; a lower valve inner limiting sleeve is provided between the lower valve inner body and the lower valve outer body, and the lower valve inner limiting sleeve is tightly connected to the lower valve inner body.

6. The partial double-layer sleeve assembly according to claim 5, characterized in that, The lower valve inner body is fixedly connected to the other end of the inner sleeve by a coupling to form a second cylinder.

7. A method for connecting a partial double-layer sleeve assembly as described in any one of claims 1-6, characterized in that, Includes the following steps: The inner body of the lower valve is fitted onto the outer body of the lower valve, and the inner and outer bodies of the lower valve are fixed with the inner limiting sleeve of the lower valve to form the lower valve assembly; the three-thread connector is assembled into the lower valve assembly and then lowered into the well, so that the lower end of the three-thread connector is connected to the first oil layer casing in the well. The casing assembly is lowered into the well and connected to the lower valve assembly. The annulus space between the inner and outer casing of the casing assembly is filled with hydraulic oil. The upper valve sealing joint is lowered into the well and connected to the inner casing of the casing assembly. The upper valve sealing sleeve is lowered into the well and fitted onto the upper valve sealing joint, and the upper valve sealing sleeve is sealed to the outer casing of the casing assembly. The inner casing coupling is lowered into the well and connected to the upper valve sealing joint. The second oil layer casing is then lowered and connected to the inner casing coupling.

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