A downhole variable diameter layered structure sealing device and method

Abstract

The invention discloses an underground variable-diameter layered structure sealing device and method, which are used to realize the sealing separation of different layers in a variable-diameter wellbore, wherein the wellbore comprises different layers distinguished by well sections with different diameters, and the diameter of each well section decreases with increasing depth; the device comprises a plurality of sealing components with different diameters, and each sealing component is installed in a well section in the wellbore; the sealing components comprise a sampling section, a variable-diameter isolation assembly, a grouting pipe and a water stop strip; the lower end of the sampling section is installed with the variable-diameter isolation assembly wrapped with the water stop strip, and the variable-diameter isolation assembly is installed at the well section where the diameter is changed, one end of the grouting pipe is arranged on the ground, and the other end passes through the sampling section and is connected to the variable-diameter isolation assembly; the sampling section is used to collect groundwater in the well section in the wellbore; the variable-diameter isolation assembly is used to chemically isolate the layered well section through the slurry injected by the grouting pipe; the water stop strip is used to physically isolate the layered well section at the wellbore diameter change point, and to provide buffering during the process of the device going down into the well.

Description

Technical Field

[0001] The invention relates to the field of stratum separation, and in particular to an underground variable-diameter layered structure sealing device and method. Background Art

[0002] In order to accurately monitor the groundwater pollution in strata of different depths, strata of different depths need to be separated during groundwater sampling and monitoring to ensure that the sampled water is representative of the strata and sampling depth. In the field of oil and gas extraction, packers are widely used for downhole stratum separation. According to different working principles, they can be divided into mechanical, hydraulic and self-expanding types. Mechanical and hydraulic types have complex structures and are expensive. They are generally suitable for deep strata, highly corrosive media, and extreme environments such as high temperature and high pressure. The self-expanding type achieves the purpose of sealing by absorbing liquid media such as water or oil in the wellbore to produce volume expansion. It is easy to decompose during use, has poor stability, and is difficult to unseal. In addition, the low strength and poor pressure resistance of the expansion material will affect the sealing performance.

[0003] For shallow formation plugging, reference [1] (invention patent with authorization announcement number "CN 105178908 B" "Chemical grouting isolation device and method for underground formation plugging") proposes a chemical grouting isolation device and method for underground formation plugging. The method is based on a set position of the shotcrete plug, which is connected to the grouting section of the grouting pipe located underground through a self-operated segmented pressure control valve, so that grouting operations at different depths can be achieved through different injection pressure values ​​of a grouting pipe at the wellhead. During the implementation of the device and method, the grouting pipe and the shotcrete plugs, self-operated segmented pressure control valves, and tees of each layer need to be placed in the wellbore for completion and fixation. However, due to structural design problems, the actual downhole fixation process often encounters jamming, and the branch cannot reach the designed depth and cannot be effectively fixed. In order to solve this problem, it is necessary to appropriately adjust and improve the downhole isolation device to achieve the separation and sealing of the upper and lower layers of the shallow formation. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose an underground variable diameter layered structure sealing device and method. The present invention is used to separate the upper and lower layers of shallow strata, thereby achieving the purpose of groundwater sampling at different layers in one wellbore.

[0005] In order to achieve the above-mentioned purpose, the present invention proposes an underground variable-diameter layered structure sealing device, which is used to realize the sealing separation of different layers in a variable-diameter wellbore, and the wellbore includes different layers distinguished by well sections with different diameters, and the diameter of each well section decreases with the increase of depth; it is characterized in that the device includes a plurality of sealing components with different diameters, each sealing component is installed in a well section in the wellbore; the sealing components include a sampling section, a variable-diameter isolation assembly, a grouting pipe and a water stop strip; the lower end of the sampling section is installed with a variable-diameter isolation assembly wrapped with a water stop strip, and the variable-diameter isolation assembly is installed at the place where the well section changes diameter, one end of the grouting pipe is set on the ground, and the other end passes through the sampling section and is connected to the variable-diameter isolation assembly; wherein,

[0006] The sampling section is used to collect groundwater in the well section in the wellbore;

[0007] The variable diameter isolation assembly is used to chemically isolate the layered well sections through the slurry injected through the grouting pipe;

[0008] The water stop strip is used to physically isolate the layered well sections at the location where the wellbore diameter changes, and is also used for buffering during the process of lowering the device into the well.

[0009] As an improvement of the above-mentioned device, the sampling section is a cylindrical shell with a closed bottom layer, and the shell diameter is smaller than the wellbore diameter, so that there is an annulus part between the wellbore and the sampling section shell; a plurality of open grooves are arranged in the middle of the sampling section, so that the inside of the sampling section shell is connected with the annulus part outside the shell, and groundwater enters the inside of the sampling section shell through the open grooves; a small hole is arranged at the bottom of the sampling section, so that the grouting pipe passes through the sampling section and is connected to the variable diameter isolation assembly.

[0010] As an improvement of the above-mentioned device, the variable diameter isolation assembly is a trumpet-shaped shell with openings at the upper and lower ends, which is arranged at the diameter change point of the well section. The upper end face of the variable diameter isolation assembly is connected to the sampling section in the first well section above it, and the lower end face of the variable diameter isolation assembly is connected to the sampling section in the second well section below it; the diameter of the upper end face is the same as the diameter of the sampling section in the first well section, and the diameter of the lower end face is the same as the diameter of the sampling section in the second well section; there is an annulus part between the wellbore and the shell of the variable diameter isolation assembly; two layers of pipelines parallel to each other are arranged in the cavity above the diameter change point of the shell of the variable diameter isolation assembly, and the two layers of pipelines have the same diameter, which is smaller than the diameter of the upper end face of the variable diameter isolation assembly; each layer of pipelines is a "M"-shaped structure that is interconnected, and the "M"-shaped structure pipeline is provided with small holes on the outer edge of the shell, so that the "M"-shaped structure pipeline is connected to the annulus part outside the shell.

[0011] As an improvement of the above-mentioned device, one end of the grouting pipe is a slurry inlet, which is arranged on the ground, and the other end passes through the sampling section and is connected to the two layers of pipelines of the variable diameter isolation assembly; when the slurry is injected from the slurry inlet, it enters the two layers of pipelines in the shell of the variable diameter isolation assembly along the grouting pipe, and flows into the annular space outside the variable diameter isolation assembly through the small holes on the outer edge of the shell of the "M"-shaped structure pipeline.

[0012] The present invention also proposes an underground variable diameter layered structure sealing method, the method comprising:

[0013] Step 1) lowering the sampling section for the deepest section of the wellbore into a designated position in the wellbore;

[0014] Step 2) Assemble the sealing components of each layer in order from the second deepest layer to the uppermost layer, and lower the sealing components of each layer into the designated position in the wellbore in a bottom-to-top order;

[0015] Step 3) Test the connectivity of the grouting pipes of the entire device, and complete the well after completion;

[0016] Step 4) Inject slurry into the grouting pipe of each well section on the ground. The slurry passes through the sampling section of each well section in turn, reaches the "M"-shaped structure pipeline inside the variable diameter isolation assembly of each well section, and flows into the annular space outside the variable diameter isolation assembly through the small holes on the outer edge of the shell of the "M"-shaped structure pipeline, thereby realizing chemical isolation of each layer; the water stop strip expands when encountering water in the wellbore, and cooperates with the variable diameter wellbore structure to isolate each well section at the diameter change point, thereby realizing physical sealing of the variable diameter layered structure underground.

[0017] As an improvement of the above method, the step 2) specifically includes:

[0018] Installing the sampling section for the sub-deep layer on the variable diameter isolation assembly;

[0019] Wrap the water stop strip around the outside of the variable diameter packing assembly where the diameter changes;

[0020] The grouting pipe is passed through the small hole on the bottom surface of the sampling section and connected to the two layers of pipelines of the variable diameter sealing assembly to complete the assembly of the sealing component;

[0021] The assembled sealing components are lowered into a designated position in the wellbore, so that the variable diameter packing assembly wrapped with the water stop strip is located at the diameter change position of the sub-deep layer of the wellbore;

[0022] Repeat the above steps in order from bottom to top until the assembly and deployment of the topmost sealing component is completed.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] 1. The device and method of the present invention adopt chemical slurry isolation and water stop strip isolation at the same time, and utilize the variable diameter wellbore structure characteristics to avoid slurry leakage, while compensating for the characteristics of easy decomposition and poor stability of water stop strip isolation; downhole isolation combines the advantages of chemical slurry and water stop strip expansion isolation, and the isolation effect is better.

[0025] 2. The device of the present invention has a simple structure and the cost can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a downhole variable diameter layered structure sealing device according to embodiment 1 of the present invention;

[0027] Figure 2 2 is a schematic structural diagram of a second variable diameter packing assembly according to Embodiment 1 of the present invention;

[0028] Figure 3 is a structural cross-sectional view of a second variable diameter packing assembly according to Example 1 of the present invention;

[0029] Figure 4 It is a top view of the second variable diameter sealing assembly of Example 1 of the present invention.

[0030] Reference numerals

[0031] 1. First slurry inlet 2. Second slurry inlet 3. Ground

[0032] 4. First sampling section 5. First grouting pipe 6. Second grouting pipe

[0033] 7. First well section 8. First layer of groundwater 9. First variable diameter isolation assembly

[0034] 10. First slurry 11. Second sampling section 12. First water stop strip

[0035] 13. Second layer of groundwater 14. Second variable diameter isolation assembly 15. Second well section

[0036] 16. Second slurry 17. Second water stop strip 18. Third sampling section

[0037] 19. The third layer of groundwater 20. The third well section 21. The "M" shaped pipeline DETAILED DESCRIPTION

[0038] The present invention provides an underground variable-diameter layered structure sealing device and method, which are used to separate upper and lower layers of a shallow stratum, thereby achieving the purpose of groundwater sampling at different layers in a wellbore.

[0039] The following technical solutions are specifically adopted:

[0040] A variable diameter layered structure sealing device includes slurry, grouting pipes of each layer, sampling sections of each layer, variable diameter sealing components, water stop strips and a wellbore. The grouting pipe passes through the sampling section and is connected to the variable diameter sealing component; each sampling section is connected to each other through the variable diameter sealing component in its corresponding well section.

[0041] The wellbore includes well section structures with different diameters, and the diameter of each well section structure decreases as the depth increases.

[0042] One end of the grouting pipe is arranged on the ground, and the other end passes through the sampling section and is connected with each variable diameter sealing assembly.

[0043] An open groove is provided in the middle of the sampling section, connecting the interior of the sampling section with the wellbore and the annulus of the sampling section, and groundwater enters into the interior of the sampling section through the open groove.

[0044] The upper and lower parts of the variable diameter packer assembly are connected to sampling sections of different sizes, with a small hole in the middle. One end of the small hole is connected to the grouting pipe, and the other end is connected to the upper and lower sets of "M"-shaped structural pipelines inside the variable diameter packer assembly. The "M"-shaped structural pipeline is connected to the external annulus of the variable diameter packer assembly.

[0045] The water stop strip is located outside the variable diameter isolation assembly.

[0046] The sampling section, the variable diameter packing assembly and the water stop strip are all located in the wellbore. Each sampling section is located in each layer of the well section, the variable diameter packing assembly is located at the diameter change of the well section, and the water stop strip is wrapped outside the variable diameter packing assembly.

[0047] The slurry is injected into the variable-diameter isolation assembly after passing through the sampling section through the grouting pipe, and then flows into the annular space outside the variable-diameter isolation assembly through the "M"-shaped structure pipeline inside the variable-diameter isolation assembly to seal it. At the same time, the water stop strip and the variable-diameter well section structure are used to isolate the upper and lower layers of the shallow strata.

[0048] A method for underground variable diameter layered structure sealing, specifically comprising the following steps:

[0049] Step 1: Design the wellbore structure and drill the well according to the groundwater level of the selected site to form a wellbore structure containing well sections of different diameters;

[0050] Step 2: Prepare sampling sections, variable diameter isolation components, water stop strips, and grouting pipes of corresponding lengths and diameters according to the wellbore structure;

[0051] Step 3: Assemble the grouting pipe, sampling section, variable diameter packing assembly and water stop strip in sequence and lower them into the wellbore, so that the variable diameter packing assembly wrapped with the water stop strip is located at the diameter change position of each layer of the wellbore. The water stop strip expands when it encounters water in the well and cooperates with the variable diameter wellbore structure to isolate each well section at the diameter change position. In addition, the water stop strip can also play a buffering role during the process of lowering the device into the well;

[0052] Step 4: Test the connectivity of the grouting pipes of the entire device, and complete the well after completion;

[0053] Step 5: Inject the slurry into each layer of grouting pipes on the ground. The slurry passes through the sampling section in turn, reaches the "M"-shaped structure pipeline inside the variable-diameter isolation assembly, and finally reaches the annular space outside the variable-diameter isolation assembly, thereby realizing the multi-stage isolation function of each layer.

[0054] The working principle is as follows: the isolation function can be achieved in two ways. On the one hand, expansion isolation is performed through the water stop strip wrapped on the outside of the variable diameter isolation assembly. The water stop strip is wrapped on the outside of the variable diameter isolation assembly, and expands when it encounters water during the downhole process. It is located at the diameter change of the wellbore and plays a certain degree of isolation role in combination with the wellbore structure. On the other hand, the slurry is injected into the variable diameter isolation assembly after passing through the sampling section through the grouting pipe, and flows into the annular space outside the variable diameter isolation assembly through the "M"-shaped structure pipeline inside the variable diameter isolation assembly for chemical plugging. The variable diameter structure of the wellbore can prevent the slurry from being lost.

[0055] The present invention makes full use of the structural characteristics of the variable diameter wellbore and designs a variable diameter isolation assembly with corresponding dimensions. The variable diameter isolation assembly is located at the diameter change portion of the wellbore. On the one hand, the water stop strip wrapped around the outside of the variable diameter isolation assembly swells when it encounters water during the process of going down the well, thus achieving a certain degree of isolation function, and at the same time, it can play a buffering role during the process of going down the well. On the other hand, after the slurry passes through the sampling section through the grouting pipe, it passes through the "M"-shaped structure pipeline inside the variable diameter isolation assembly and reaches the external annulus for chemical separation. The diameter change structure of the wellbore can prevent the loss of slurry and isolate each layer to the greatest extent.

[0056] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0057] Example 1

[0058] This embodiment provides a downhole variable diameter layered structure sealing device, taking a three-layer well section as an example, but the present invention is not limited to three layers. Figure 1 As shown, it includes a first slurry inlet 1; a second slurry inlet 2; a ground surface 3; a first sampling section 4; a first grouting pipe 5; a second grouting pipe 6; a first well section 7; a first layer of groundwater 8; a first variable-diameter packing assembly 9; a first slurry 10; a second sampling section 11; a first water stop strip 12; a second layer of groundwater 13; a second variable-diameter packing assembly 14; a second well section 15; a second slurry 16; a second water stop strip 17; a third sampling section 18; a third layer of groundwater 19; and a third well section 20.

[0059] The first sampling section 4 is connected to the first variable diameter packer assembly 9, the second sampling section 11, the second variable diameter packer assembly 14 and the third sampling section 18 in sequence. The first grouting pipe 5 passes through the first sampling section 4 and is connected to the first variable diameter packer assembly 9. The second grouting pipe 6 passes through the first sampling section 4, the first variable diameter packer assembly 9 and the second sampling section 14 and is connected to the second variable diameter packer assembly 14. The water stop strip 12 is wrapped around the outer diameter change of the first variable diameter packer 9. The water stop strip 17 is wrapped around the outer diameter change of the second variable diameter packer 14.

[0060] The wellbore includes three well section structures with different diameters, including a first well section 7, a second well section 15 and a third well section 20. The diameter of each well section structure decreases with increasing depth.

[0061] The stratum contains groundwater from three different layers, including a first layer of groundwater 8 , a second layer of groundwater 13 and a third layer of groundwater 19 .

[0062] The stratum where the first well section 7 is located contains a first layer of groundwater 8 , the stratum where the second well section 15 is located contains a second layer of groundwater 13 , and the stratum where the third well section 20 is located contains a third layer of groundwater 19 .

[0063] The first sampling section 4 is located in the first well section 7, the second sampling section 11 is located in the second well section 15, and the third sampling section 18 is located in the third well section 20. The first sampling section 4, the second sampling section 11 and the third sampling section 18 all have open grooves in the middle, connecting the interior of each sampling section with the wellbore and the annulus of the sampling section, and the formation water of each layer enters the interior of the sampling section through the open grooves.

[0064] The first variable diameter packer assembly 9 is located at the wellbore diameter change position between the first well section 7 and the second well section 15, and the upper end is connected to the first sampling section 4, and the lower end is connected to the second sampling section 11. The second variable diameter packer assembly 14 is located at the wellbore diameter change position between the second well section 15 and the third well section 20, and the upper end is connected to the second sampling section 11, and the lower end is connected to the third sampling section 18.

[0065] The first water stop strip 12 is located at the diameter change position of the first variable diameter packing assembly 9 , and the second water stop strip 17 is located at the diameter change position of the second variable diameter packing assembly 14 .

[0066] One end of the first grouting pipe 5 and the second grouting pipe 6 are both arranged on the ground 3 .

[0067] Figure 2 , Figure 3 , Figure 4They are respectively a structural schematic diagram, a cross-sectional view and a top view of the second variable-diameter packing assembly 14. It should be noted that the second variable-diameter packing assembly is taken as an example here, and the structure of each variable-diameter packing assembly is the same. The variable-diameter packing assembly is connected to sampling sections of different sizes at the top and bottom, and a small hole is left in the middle. One end of the small hole is connected to the second grouting pipe 6, and the other end is connected to the upper and lower two sets of "M"-shaped structural pipelines 21 inside the second variable-diameter packing assembly 14. The "M"-shaped structural pipeline 21 is connected to the external annulus of the second variable-diameter packing assembly 14.

[0068] The first slurry 10 is injected into the first grouting pipe 5 through the first slurry inlet 1 located on the ground 3, and is injected into the first variable diameter isolation assembly 9 after passing through the first sampling section 4. It flows into the annular space outside the first variable diameter isolation assembly 9 through the "M"-shaped structure pipeline inside the first variable diameter isolation assembly 9 to be sealed, and at the same time, cooperates with the first water stop strip 12 and the variable diameter well section structure to realize the isolation of the first well section 7 and the second well section 15.

[0069] The second slurry 16 is injected into the second grouting pipe 6 through the second slurry inlet 2 located on the ground 3, passes through the first sampling section 4, the first variable diameter isolation assembly 9 and the second sampling section 11 in sequence, and is injected into the second variable diameter isolation assembly 14, and flows into the annular space outside the second variable diameter isolation assembly 14 through the "M"-shaped structure pipeline inside the second variable diameter isolation assembly 14 for sealing, and at the same time cooperates with the second water stop strip 17 and the variable diameter well section structure to realize the isolation of the second well section 15 and the third well section 20.

[0070] Example 2

[0071] This embodiment provides a method for sealing a variable diameter layered structure in a well, taking a three-layer well section as an example, but the present invention is not limited to three layers, and specifically includes the following steps:

[0072] Step 1: According to the groundwater level of the selected site, the wellbore structure is designed, including the length and diameter of the first well section 7, the second well section 15 and the third well section 20. Drilling is performed according to the design requirements to form a wellbore structure including well sections with different diameters;

[0073] Step 2: Prepare the first sampling section 4, the second sampling section 11 and the third sampling section 18 of corresponding lengths and diameters according to the wellbore structure, as well as the first variable diameter packing assembly 9 and the first water stop strip 12 for isolating the first well section 7 and the second well section 15, and the second variable diameter packing assembly 14 and the second water stop strip 17 for isolating the second well section 15 and the third well section 20, as well as the first grouting pipe 5 and the second grouting pipe 6;

[0074] Step 3: Lower the third sampling section 18 for the deepest section of the wellbore to the designated position in the wellbore. From the secondary deep layer to the uppermost section, assemble the sealing components of each layer in sequence, and lower the sealing components of each layer into the designated position in the wellbore in a bottom-up order. Specifically: install the second sampling section 11 on the second variable diameter isolation assembly 14, wrap the second water stop strip 17 around the outside of the diameter change of the second variable diameter isolation assembly 14, pass the second grouting pipe 6 through the small hole on the bottom surface of the second sampling section 11 and connect it to the two layers of pipelines of the second variable diameter isolation assembly 14 to complete the assembly of the second section of the sealing component; lower the assembled second section of the sealing component into the designated position in the wellbore, so that the second variable diameter isolation assembly 14 wrapped with the second water stop strip 17 is located at the diameter change of the secondary deep layer of the wellbore.

[0075] Install the first sampling section 4 on the first variable diameter packing assembly 9, wrap the first water stop strip 12 around the outside of the first variable diameter packing assembly 9 where the diameter changes, pass the first grouting pipe 5 through the small hole on the bottom of the first sampling section 4 and connect it to the two layers of pipelines of the first variable diameter packing assembly 9, and complete the assembly of the first section of the sealing component. Lower the assembled first sealing component into the specified position in the wellbore, so that the first variable diameter packing assembly 9 wrapped with the first water stop strip 12 is located at the diameter change of the uppermost layer of the wellbore.

[0076] Step 4: Test the connectivity of the grouting pipes of the entire device, and complete the well after completion;

[0077] Step 5: Inject the first slurry 10 into the first variable-diameter packing assembly 9 through the first grouting pipe 5 on the ground 3, and the first slurry 10 reaches the annular space outside the first variable-diameter packing assembly 9 through the "M"-shaped structure pipeline inside the first variable-diameter packing assembly 9, so as to isolate the first well section 7 and the second well section 15. The second slurry 16 is injected into the second variable-diameter packing assembly 14 through the second grouting pipe 6, and reaches the annular space outside the second variable-diameter packing assembly 14 through the "M"-shaped structure pipeline inside the second variable-diameter packing assembly 14, so as to isolate the second well section 15 and the third well section 20.

[0078] The underground variable-diameter layered structure sealing device and method of the present invention is one of the supporting technologies of the underground layered sampling system independently developed by the Wuhan Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, and has good economy and flexible site applicability.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A downhole variable diameter layered structure sealing device, used to achieve sealing separation of different layers in a variable diameter wellbore, the wellbore includes different layers divided by well sections with different diameters, and the diameter of each well section decreases with increasing depth; It is characterized in that The device comprises a plurality of sealing components with different diameters, each of which is installed in a well section in the wellbore; the sealing components comprise a sampling section, a variable diameter packing assembly, a grouting pipe and a water stop strip; a variable diameter packing assembly wrapped with a water stop strip is installed at the lower end of the sampling section, and the variable diameter packing assembly is installed at the diameter change position of the well section, one end of the grouting pipe is arranged on the ground, and the other end passes through the sampling section and is connected to the variable diameter packing assembly; wherein, The sampling section is used to collect groundwater in the well section in the wellbore; The variable diameter isolation assembly is used to chemically isolate the layered well sections through the slurry injected through the grouting pipe; The water stop strip is used to physically isolate the layered well section at the place where the wellbore diameter changes, and is also used for buffering during the process of lowering the device into the well; The sampling section is a cylindrical shell with a closed bottom layer, and the shell diameter is smaller than the wellbore diameter, so that there is an annulus between the wellbore and the sampling section shell; a plurality of open grooves are arranged in the middle of the sampling section, so that the inside of the sampling section shell is connected with the annulus outside the shell, and groundwater enters the inside of the sampling section shell through the open grooves; a small hole is arranged at the bottom of the sampling section, so that the grouting pipe passes through the sampling section and is connected to the variable diameter isolation assembly; The variable-diameter isolation assembly is a trumpet-shaped shell with openings at the top and bottom, which is arranged at the diameter change point of the well section. The upper end face of the variable-diameter isolation assembly is connected to the sampling section in the first well section above it, and the lower end face of the variable-diameter isolation assembly is connected to the sampling section in the second well section below it; the diameter of the upper end face is the same as the diameter of the sampling section in the first well section, and the diameter of the lower end face is the same as the diameter of the sampling section in the second well section; there is an annulus part between the wellbore and the shell of the variable-diameter isolation assembly; two layers of pipelines parallel to each other are arranged in the cavity above the diameter change point of the shell of the variable-diameter isolation assembly, and the two layers of pipelines have the same diameter, which is smaller than the diameter of the upper end face of the variable-diameter isolation assembly; each layer of pipelines is a "M"-shaped structure that is interconnected, and small holes are arranged on the outer edge of the shell of the "M"-shaped structure pipeline, so that the "M"-shaped structure pipeline is connected to the annulus part outside the shell.

2. The downhole variable diameter layered structure sealing device according to claim 1, It is characterized in that One end of the grouting pipe is a slurry inlet, which is arranged on the ground, and the other end passes through the sampling section and is connected to the two layers of pipelines of the variable diameter isolation assembly; when the slurry is injected from the slurry inlet, it enters the two layers of pipelines in the shell of the variable diameter isolation assembly along the grouting pipe, and flows into the annular space outside the variable diameter isolation assembly through the small holes on the outer edge of the shell of the "M"-shaped structure pipeline.

3. A downhole variable diameter layered structure sealing method, based on the device of claim 1 or 2, the method include: Step 1) lowering a sampling section for the deepest section of the wellbore into a designated position in the wellbore; Step 2) assembling the sealing components of each layer in sequence from the second deep layer to the uppermost layer of the well section, and lowering the sealing components of each layer into the designated position in the wellbore in a bottom-to-top order; Step 3) Testing the connectivity of the grouting pipe of the entire device, and completing the well after completion; Step 4) Inject slurry into the grouting pipe of each well section on the ground, the slurry passes through the sampling section of each well section in turn, reaches the "M"-shaped structure pipeline inside the variable diameter isolation assembly of each well section, and flows into the annular space outside the variable diameter isolation assembly through the small holes on the outer edge of the shell of the "M"-shaped structure pipeline, so as to realize the chemical isolation of each layer; the water stop strip expands when encountering water in the wellbore, cooperates with the variable diameter wellbore structure to isolate each well section at the diameter change point, thereby realizing the physical sealing of the variable diameter layered structure underground.

4. The underground variable diameter layered structure sealing method according to claim 3, It is characterized in that The step 2) specifically includes: Installing the sampling section for the sub-deep layer on the variable diameter isolation assembly; Wrap the water stop strip around the outside of the variable diameter packing assembly where the diameter changes; The grouting pipe is passed through the small hole on the bottom surface of the sampling section and connected to the two layers of pipelines of the variable diameter isolation assembly to complete the assembly of the sealing component; The assembled sealing components are lowered into a designated position in the wellbore, so that the variable diameter packing assembly wrapped with the water stop strip is located at the diameter change position of the sub-deep layer of the wellbore; Repeat the above steps in order from bottom to top until the assembly and deployment of the topmost sealing component is completed.

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