An in-situ testing device for cement sheath strength in wellbore plugging

Abstract

The application discloses a cement plug cementing strength in-situ testing device for wellbore plugging, belongs to the technical field of old well plugging testing of gas storage, and aims at measuring the shearing cementing strength and tensile cementing strength of the cement plug for wellbore plugging. The cement plug cementing strength in-situ testing device comprises a sample cylinder (20), a main ejector rod (2) and a sample plate (8), the main ejector rod (2) is provided with a secondary ejector rod (3), a ring-shaped cement plug cavity can be formed in the sample cylinder (20), a ring-shaped cement plug (10) can be formed after cement paste is injected into the cement plug cavity, the main ejector rod (2) can move the sample plate (8) downward relative to the cement plug (10), and the secondary ejector rod (3) can move the cement plug (10) downward relative to the sample cylinder (20). The cement plug cementing strength in-situ testing device can not only test the shearing cementing strength of the cement plug, but also test the tensile cementing strength of the cement plug.

Description

Technical Field

[0001] This invention relates to the field of gas storage well plugging testing technology, specifically an in-situ testing device for the bonding strength of cement plugs used for well plugging. Background Technology

[0002] In the process of constructing a gas storage facility using an old well, it is necessary to seal the old well. During the sealing process, cement slurry is an important material for forming a sealing cement plug inside the wellbore. Under the conditions of high temperature and high pressure downhole and the gas storage facility's injection and production operation, the cement plug poses a significant challenge to the sealing quality of the old well. The determination of the forging and milling length and the thickness of the cement plug during the sealing process directly affects the sealing effect of the old well in the gas storage facility.

[0003] Current cement plug bonding testing equipment operates under relatively limited conditions, simulating simple working conditions and failing to consider the impact of pressure fluctuations at the reservoir bottom on bonding strength testing. Furthermore, according to research in related fields, cement plug bonding strength can be divided into shear bonding strength and tensile bonding strength. Under complex wellbore conditions, the cemented surface formed by the cement plug may not necessarily exhibit shear failure. Currently, the mainstream method used in publicly available indoor cement stone bonding strength testing equipment is the "ejection method," primarily focusing on shear strength testing of cement plugs, which lacks broad applicability. Summary of the Invention

[0004] To measure the shear bond strength and tensile bond strength of cement plugs used for wellbore plugging, this invention provides an in-situ testing device for the bond strength of cement plugs used for wellbore plugging. This in-situ testing device can test not only the shear bond strength of cement plugs but also the tensile bond strength of cement plugs.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An in-situ testing device for the bonding strength of cement plugs used for well plugging includes a sample cylinder and a main push rod and a sample plate arranged vertically. A cylindrical auxiliary push rod is fitted around the main push rod. An annular cement plug cavity can be formed inside the sample cylinder. After cement slurry is injected into the cement plug cavity, an annular cement plug can be formed. The lower end face of the cement plug can bond with the upper surface of the sample plate, the outer circumferential surface of the cement plug can bond with the inner circumferential surface of the sample cylinder, and the upper end face of the cement plug can abut against the auxiliary push rod. The main push rod can move the sample plate downward relative to the cement plug, and the auxiliary push rod can move the cement plug downward relative to the sample cylinder.

[0007] The beneficial effects of this invention are:

[0008] 1. It can test not only the shear bond strength of cement plugs, but also the tensile bond strength of cement plugs, so as to comprehensively compare the bond strength of cement plugs.

[0009] 2. When conducting in-situ bonding strength tests on the cement plug bonding layer, in addition to simulating the temperature and pressure bonding environment that usually exists in cement plugs, the influence of pressure fluctuations at the bottom of the cement on the bonding strength test can also be simulated. Attached Figure Description

[0010] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0011] Figure 1 This is a schematic diagram of the in-situ testing device for the bonding strength of cement plugs used for wellbore sealing according to the present invention.

[0012] Figure 2 This is a schematic diagram of the main components of the in-situ testing device for the bonding strength of cement plugs for wellbore sealing described in this invention.

[0013] Figure 3 This is a schematic diagram of the working state of the in-situ testing device for the bonding strength of cement plugs for well casing sealing according to the present invention.

[0014] The annotations in the attached figures are explained as follows:

[0015] 1. Upper drive mechanism; 2. Main push rod; 3. Secondary push rod; 4. Inner support column; 5. Outer protective cover; 6. Lower support cover; 7. Lower push rod; 8. Sample plate; 9. Sealed vessel body; 10. Cement plug; 11. Sealed vessel cover; 12. Positioning bolt hole; 13. Cement slurry injection hole; 14. First pressure sensor; 15. Confining pressure injection hole; 16. Confining pressure injection pump; 17. Data logger; 18. Sealing ring; 19. Sealing gasket; 20. Sample cylinder; 21. Third pressure sensor; 22. Fourth pressure sensor; 23. Temperature sensor; 24. Confining pressure chamber; 25. Lower drive mechanism; 26. Second pressure sensor. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] An in-situ testing device for the bonding strength of cement plugs used in wellbore sealing includes a sample cylinder 20 and a main push rod 2 and a sample plate 8 arranged vertically. A cylindrical auxiliary push rod 3 is sleeved on the main push rod 2. An annular cement plug cavity can be formed inside the sample cylinder 20. Injecting cement slurry into the cement plug cavity forms an annular cement plug 10. The lower end face of the cement plug 10 can bond with the upper surface of the sample plate 8, the outer circumferential surface of the cement plug 10 can bond with the inner circumferential surface of the sample cylinder 20, and the upper end face of the cement plug 10 can abut against the lower end of the auxiliary push rod 3. The main push rod 2 allows the sample plate 8 to move downwards relative to the cement plug 10, and the auxiliary push rod 3 allows the cement plug 10 to move downwards relative to the sample cylinder 20. Figures 1 to 3 As shown.

[0018] In this invention, "in-situ" refers to the working position of the cement plug used for wellbore sealing downhole. The in-situ cement plug bonding strength testing device can simulate the working conditions of the cement plug at its downhole working position. The sample plate 8 and sample cylinder 20 can be made of rock or metal. For example, the sample plate 8 can be a circular plate made from formation rock collected at the cement plug's downhole working position, and the sample cylinder 20 can be a cylinder made from formation rock collected at the cement plug's downhole working position, thus realistically simulating the working conditions of the cement plug at its downhole working position. Alternatively, the sample plate 8 and sample cylinder 20 can also be made of steel.

[0019] In this embodiment, an inner support column 4 connects the main push rod 2 and the sample plate 8. The main push rod 2, the inner support column 4, the auxiliary push rod 3, and the sample cylinder 20 are all in an upright state. The main push rod 2, the inner support column 4, and the sample plate 8 are connected sequentially from top to bottom. The cement plug cavity is located between the inner circumferential surface of the sample cylinder 20 and the outer circumferential surface of the inner support column 4. A first pressure sensor 14 is provided between the main push rod 2 and the inner support column 4, and a second pressure sensor 26 is provided on the lower surface of the auxiliary push rod 3.

[0020] In this embodiment, the axes of the main push rod 2, the inner support column 4, the secondary push rod 3, the sample cylinder 20, and the sample plate 8 coincide. A third pressure sensor 21 is installed on the inner surface of the sample cylinder 20 along the axis of the main push rod 2. The length of the inner support column 4 is less than the length of the sample cylinder 20. The diameter of the main push rod 2 is equal to the diameter of the inner support column 4, the diameter of the main push rod 2 is equal to the inner diameter of the secondary push rod 3, the diameter of the main push rod 2 is less than the diameter of the sample plate 8, and the diameter of the sample plate 8 is equal to the outer diameter of the lower end of the secondary push rod 3.

[0021] In this embodiment, the outer diameter of the sample plate 8 is equal to the inner diameter of the sample cylinder 20, the upper surface of the sample plate 8 is flush with the lower end face of the sample cylinder 20, the outer diameter of the lower end of the auxiliary push rod 3 is equal to the inner diameter of the sample cylinder 20, and the lower end face of the auxiliary push rod 3 is flush with the upper end face of the sample cylinder 20. The sample cylinder 20 is provided with positioning bolt holes 12 for fixing. The sample cylinder 20 can be connected and fixed to the sealing vessel cover 11 described below through the positioning bolt holes 12 and bolts. Figure 2 As shown.

[0022] The upper end face of the cement plug cavity coincides with the lower end face of the auxiliary push rod 3, the lower end face of the cement plug cavity coincides with the upper surface of the sample plate 8, a part of the inner circumferential surface of the cement plug cavity coincides with the outer circumferential surface of the inner support column 4, another part of the inner circumferential surface of the cement plug cavity coincides with the outer circumferential surface of the main push rod 2, and the outer circumferential surface of the cement plug cavity coincides with the inner circumferential surface of the sample cylinder 20.

[0023] In this embodiment, an upper drive mechanism 1 is connected to the upper ends of the main push rod 2 and the auxiliary push rod 3. The upper drive mechanism 1 can independently drive the main push rod 2 and the auxiliary push rod 3 to move downwards. The upper drive mechanism 1 can be two independent hydraulic cylinders arranged in parallel. The two hydraulic cylinders are connected one-to-one with the main push rod 2 and the auxiliary push rod 3. For example, the two hydraulic cylinders are a first hydraulic cylinder and a second hydraulic cylinder. The first hydraulic cylinder is connected to the main push rod 2, and the second hydraulic cylinder is connected to the auxiliary push rod 3. The first hydraulic cylinder can drive the main push rod 2 to move upwards or downwards, and the second hydraulic cylinder can drive the auxiliary push rod 3 to move upwards or downwards. Figures 1 to 3 As shown.

[0024] In this embodiment, the lower end of the auxiliary push rod 3 is provided with an outward protruding ring, and the lower end of the auxiliary push rod 3 is provided with a cement slurry injection hole 13 and an exhaust hole. The cement slurry injection hole 13 is connected to the cement plug cavity. The cement plug can be injected into the cement plug cavity through the cement slurry injection hole 13, and the gas in the cement plug cavity can be discharged through the exhaust hole to ensure that the cement plug 10 is dense. A removable plug can be provided in the exhaust hole.

[0025] In this embodiment, the in-situ testing device for the bonding strength of cement plugs used for well plugging further includes a sealing vessel. The sealing vessel contains a sealing vessel cover 11 and a sealing vessel body 9 connected vertically. The sealing vessel cover 11 and the sealing vessel body 9 can be connected by bolts. The sealing vessel body 9 contains a cavity and includes side walls and a bottom plate. The sealing vessel cover 11 has an upper mounting through hole, and the sealing vessel body 9 has a lower mounting through hole. The axis of the main push rod 2, the axis of the upper mounting through hole, and the axis of the lower mounting through hole coincide. The diameter of the upper mounting through hole is equal to the diameter of the lower mounting through hole.

[0026] In this embodiment, the sample cylinder 20 is located within the accommodating cavity. The axis of the sample cylinder 20, the axis of the sealed vessel cover 11, the axis of the sealed vessel body 9, and the axis of the sealed vessel coincide. The upper end of the sample cylinder 20 is sealed to the sealed vessel cover 11, and the lower end of the sample cylinder 20 is sealed to the bottom plate of the sealed vessel body 9. The outer diameter of the sample cylinder 20 is smaller than the inner diameter of the side wall of the sealed vessel body 9. A confining pressure cavity 24 is formed between the sample cylinder 20 and the sealed vessel. A confining pressure injection hole 15 is provided on the side wall of the sealed vessel body 9, and a confining pressure injection pump 16 is connected to the outside of the confining pressure injection hole 15. A fourth pressure sensor 22 and a temperature sensor 23 are provided on the inner surface of the side wall of the sealed vessel body 9. A sealing gasket 19 can be provided between the upper end of the sample cylinder 20 and the sealed vessel cover 11 to achieve a sealed connection, and a sealing gasket 19 can be provided between the lower end of the sample cylinder 20 and the bottom plate of the sealed vessel body 9 to achieve a sealed connection.

[0027] In this embodiment, the lower end of the auxiliary push rod 3 can be matched and located within the upper mounting through hole of the sealed vessel cover 11. The lower end of the auxiliary push rod 3 can be sealed and connected to the upper mounting through hole of the sealed vessel cover 11 through the sealing ring 18. The sample plate 8 can be matched and located within the lower mounting through hole of the sealed vessel body 9. The sample plate 8 can be clearance-fitted with the lower mounting through hole of the sealed vessel body 9. Figures 1 to 3 As shown.

[0028] In this embodiment, the in-situ testing device for the bonding strength of cement plugs for wellbore sealing also includes a lower push rod 7 and a lower drive mechanism 25 connected vertically. The sample plate 8 is connected vertically to the lower push rod 7. The axis of the lower push rod 7 coincides with the axis of the main push rod 2. The outer diameter of the upper end of the lower push rod 7 is equal to the outer diameter of the sample plate 8. The upper end of the lower push rod 7 can be matched and located in the lower mounting through hole of the sealing vessel 9. The upper end of the lower push rod 7 can be sealed and connected to the lower mounting through hole of the sealing vessel 9 through the sealing rubber ring 18. The lower drive mechanism 25 can drive the lower push rod 7 to move up and down. The lower drive mechanism 25 can be a hydraulic cylinder. The lower drive mechanism 25 can apply an upward stable or fluctuating load to the cement plug 10 through the lower push rod 7 and the sample plate 8 in sequence, thereby simulating and testing the in-situ gas storage under stable pressure conditions and gas storage pressure fluctuations.

[0029] In this embodiment, the in-situ testing device for the bonding strength of cement plugs used for wellbore sealing further includes an outer protective cover 5, a lower support cover 6, and a control unit connected vertically. The sealing vessel is located inside the outer protective cover 5. The main push rod 2 and the auxiliary push rod 3 both pass through the upper part of the outer protective cover 5. The upper drive mechanism 1 is located above the outer protective cover 5. The lower push rod 7 passes through the upper part of the lower support cover 6, and the lower drive mechanism 25 is located inside the lower support cover 6. Additionally, the control unit can control the operation of the in-situ testing device for the bonding strength of cement plugs used for wellbore sealing. The control unit includes a data logger 17, such as... Figure 1 As shown.

[0030] The following describes the testing method for the in-situ testing device for the bonding strength of cement plugs used in wellbore sealing:

[0031] 1. Prepare sample plate 8 and sample cylinder 20. Sample plate 8 and sample cylinder 20 can be prepared from formation rocks collected at the target working location downhole. Place the prepared sample plate 8 and sample cylinder 20 into a sealed container. Assemble the in-situ testing device for the cement plug bonding strength of the wellbore sealing. The in-situ testing device for the cement plug bonding strength of the wellbore sealing is in its initial state, such as... Figure 1 As shown.

[0032] In the initial state, the upper surface of the sample plate 8 is flush with the lower end face of the sample cylinder 20, the lower end face of the auxiliary push rod 3 is flush with the upper end face of the sample cylinder 20, and the main push rod 2, the inner support column 4, the sample plate 8 and the lower push rod 7 are connected in sequence from top to bottom. The lower part of the main push rod 2 and the inner support column 4 form the cement plug cavity between the sample cylinder 20 and the sample cylinder 20.

[0033] To prevent the lower part of the main push rod 2 and the inner support column 4 from bonding with the cement plug 10 formed below, a plastic film can be wrapped around or covered with a plastic film on the outer circumferential surface of the lower part of the main push rod 2 and the outer circumferential surface of the inner support column 4, or lubricating oil can be applied to the outer circumferential surface of the lower part of the main push rod 2 and the outer circumferential surface of the inner support column 4 before wrapping or covering with a plastic film. If the length of the inner support column 4 is equal to the length of the sample tube 20 along the axial direction of the main push rod 2, then only the outer circumferential surface of the inner support column 4 needs to be wrapped or covered with a plastic film, or only lubricating oil needs to be applied to the outer circumferential surface of the inner support column 4 before wrapping or covering with a plastic film; no treatment is required for the lower part of the main push rod 2.

[0034] 2. The prepared cement slurry is injected into the cavity of the cement plug through the cement slurry injection hole 13 on the auxiliary push rod 3. After curing, the cement slurry forms an annular cement plug 10. The lower end face of the cement plug 10 is bonded to the upper surface of the sample plate 8, the outer circumferential surface of the cement plug 10 is bonded to the inner circumferential surface of the sample cylinder 20, the upper end face of the cement plug 10 is connected to the lower end face of the auxiliary push rod 3, and the inner circumferential surface of the cement plug 10 is connected to the inner support column 4. The second pressure sensor 26 is located between the upper end face of the cement plug 10 and the lower end face of the auxiliary push rod 3. When filling and injecting cement slurry, the amount of cement needs to be adjusted according to the specific testing fixture. The amount of cement slurry injected is adjusted according to the third pressure sensor 21 in the cavity to avoid excessive pressure in the cavity. Figure 3 As shown.

[0035] 3. The confining pressure injection pump 16 is started, injecting pressurized oil at a predetermined temperature into the confining pressure chamber 24 through the confining pressure injection hole 15 on the side of the sealed vessel. According to the fourth pressure sensor 22 in the chamber, a predetermined confining pressure is formed. By controlling the temperature and pressure of the hydraulic oil, the temperature and pressure conditions simulating the in-situ bonding conditions of the cement plug 10 are achieved.

[0036] 4. The in-situ testing device for the bonding strength of cement plugs used for wellbore sealing can simulate the pressure and pressure fluctuations of gas storage tanks. After the cement plug 10 is cured, when it is necessary to simulate the pressure of the gas storage tank, the control unit applies a stable upward pressure to the cement plug 10 through the lower drive mechanism 25, the lower push rod 7, and the sample plate 8 in sequence. When it is necessary to simulate the pressure fluctuations of the gas storage tank, the control unit applies an upward fluctuating pressure to the cement plug 10 through the lower drive mechanism 25, the lower push rod 7, and the sample plate 8 in sequence, thereby simulating pressure fluctuations of different amplitudes and frequencies when the cement plug 10 is working downhole.

[0037] 5. Perform tensile bonding test: The lower drive mechanism 25 releases the load, meaning it no longer applies a load to the cement plug 10. The main push rod 2 moves downward under the action of the upper drive mechanism 1, while the auxiliary push rod 3 remains stationary. The main push rod 2 applies pressure to the sample plate 8 through the inner support column 4, and the data is recorded by the data recorder 17 from the first pressure sensor 14. The maximum tensile bonding test pressure is obtained when the sample plate 8 is removed from the cement plug 10. The maximum force recorded by the data recorder 17 during the process of the sample plate 8 removing from the cement plug 10 is the maximum tensile bonding test pressure.

[0038] 6. Perform the shear bonding test: Under the action of the upper drive mechanism 1, the auxiliary push rod 3 moves downward, while the main push rod 2 remains stationary. The auxiliary push rod 3 applies pressure to the upper end of the cement plug 10, pushing the cement plug 10 out of the sample cylinder 20. The data from the second pressure sensor 26 is recorded by the data recorder 17. The maximum shear bonding test pressure is obtained when the cement plug 10 is removed from the sample cylinder 20. The maximum force recorded by the data recorder 17 during the process of the cement plug 10 removing from the sample cylinder 20 is the maximum shear bonding test pressure.

[0039] 7. Calculate the shear bond strength and tensile bond strength of the cement plug 10 bonded to the rock strata.

[0040] 7.1 The formula for calculating shear bond strength is: Fs=Fmax1 / A1

[0041] Where Fs is the shear bond strength of cement plug 10, in N / m. 2 Fmax1 is the maximum shear bonding test pressure mentioned above, in N; A1 is the overlapping area between the cement plug 10 and the sample cylinder 20 (i.e., the area of ​​the outer circumferential surface of the cement plug 10), in m². 2 .

[0042] 7.2 The formula for calculating tensile bond strength is: Fb=Fmax2 / A2

[0043] Where Fb is the tensile bond strength of cement plug 10, in N / m. 2Fmax2 is the maximum tensile bonding test pressure mentioned above, in N; A2 is the overlapping area between the cement plug 10 and the sample plate 8 (i.e., the area of ​​the lower end face of the cement plug 10), in m². 2 .

[0044] For ease of understanding and description, this invention uses absolute positional relationships for description. Unless otherwise specified, the directional term "above" indicates... Figure 1 The direction above, the directional word "down" indicates Figure 1 The direction is below the center. This invention is described from the perspective of a reader or user, but the above directional terms should not be understood or interpreted as limiting the scope of protection of this invention.

[0045] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical solutions, and embodiments of the present invention can be freely combined and used together.

Claims

1. An in-situ testing device for the bonding strength of cement plugs used in wellbore sealing, characterized in that, The in-situ testing device for the bonding strength of cement plugs for well plugging includes a sample cylinder (20) and a main top rod (2) and a sample plate (8) set at the top and bottom. A cylindrical auxiliary top rod (3) is provided on the outer sleeve of the main top rod (2). An annular cement plug cavity can be formed inside the sample cylinder (20). After cement slurry is injected into the cement plug cavity, an annular cement plug (10) can be formed. The lower end face of the cement plug (10) can be bonded to the upper surface of the sample plate (8). The outer circumferential surface of the cement plug (10) can be bonded to the inner circumferential surface of the sample cylinder (20). The upper end face of the cement plug (10) can abut against the auxiliary top rod (3). The main top rod (2) can make the sample plate (8) move downward relative to the cement plug (10). The auxiliary top rod (3) can make the cement plug (10) move downward relative to the sample cylinder (20). The in-situ testing device for the bonding strength of cement plugs for well casing sealing also includes a sealing vessel, which contains a sealing vessel cover (11) and a sealing vessel body (9) connected at the top and bottom. The sealing vessel body (9) contains a cavity, and the sealing vessel cover (11) is provided with an upper mounting through hole, and the sealing vessel body (9) is provided with a lower mounting through hole. The sample tube (20) is located in the cavity. The upper end of the sample tube (20) is sealed to the lid (11) of the sealed vessel, and the lower end of the sample tube (20) is sealed to the vessel body (9). A confining pressure cavity (24) is formed between the sample tube (20) and the sealed vessel. A confining pressure injection hole (15) is provided on the side wall of the vessel body (9). A confining pressure injection pump (16) is connected to the outside of the confining pressure injection hole (15). A fourth pressure sensor (22) and a temperature sensor (23) are provided on the inner surface of the side wall of the vessel body (9). The lower end of the auxiliary push rod (3) can be located in the upper mounting through hole of the sealing vessel cover (11), and the lower end of the auxiliary push rod (3) can be sealed and connected with the upper mounting through hole of the sealing vessel cover (11). The sample plate (8) can be located in the lower mounting through hole of the sealing vessel body (9), and the sample plate (8) can be clearance-fitted with the lower mounting through hole of the sealing vessel body (9). The in-situ testing device for the bonding strength of cement plugs for well plugging also includes a lower push rod (7) and a lower drive mechanism (25) connected vertically. The sample plate (8) is connected vertically to the lower push rod (7). The axis of the lower push rod (7) coincides with the axis of the main push rod (2). The outer diameter of the upper end of the lower push rod (7) is equal to the outer diameter of the sample plate (8). The upper end of the lower push rod (7) can be located in the lower mounting through hole of the sealing vessel (9). The upper end of the lower push rod (7) can be sealed and connected to the lower mounting through hole of the sealing vessel (9). The lower drive mechanism (25) can apply a load to the cement plug (10) in sequence through the lower push rod (7) and the sample plate (8).

2. The in-situ testing device for the bonding strength of cement plugs for wellbore sealing according to claim 1, characterized in that, An inner support column (4) is connected between the main push rod (2) and the sample plate (8). The main push rod (2), the inner support column (4), the auxiliary push rod (3) and the sample tube (20) are all in an upright state. The cement plug cavity is located between the sample tube (20) and the inner support column (4). A first pressure sensor (14) is set between the main push rod (2) and the inner support column (4). A second pressure sensor (26) is set on the lower surface of the auxiliary push rod (3).

3. The in-situ testing device for the bonding strength of cement plugs for wellbore sealing according to claim 2, characterized in that, The axes of the main push rod (2), the inner support column (4), the auxiliary push rod (3), the sample tube (20), and the sample plate (8) are coincident. A third pressure sensor (21) is provided on the inner surface of the sample tube (20). The diameter of the main push rod (2) is equal to the diameter of the inner support column (4), and the diameter of the main push rod (2) is smaller than the diameter of the sample plate (8).

4. The in-situ testing device for the bonding strength of cement plugs for wellbore sealing according to claim 3, characterized in that, The outer diameter of the sample plate (8) is equal to the inner diameter of the sample tube (20). The upper surface of the sample plate (8) is flush with the lower end of the sample tube (20). The outer diameter of the lower end of the auxiliary push rod (3) is equal to the inner diameter of the sample tube (20). The lower end of the auxiliary push rod (3) is flush with the upper end of the sample tube (20).

5. The in-situ testing device for the bonding strength of cement plugs for wellbore sealing according to claim 1, characterized in that, The upper ends of the main push rod (2) and the auxiliary push rod (3) are connected to an upper drive mechanism (1). The upper drive mechanism (1) can independently drive the main push rod (2) and the auxiliary push rod (3) to move downward. The lower end of the auxiliary push rod (3) is provided with a cement slurry injection hole (13), which is connected to the cement plug cavity.

6. The in-situ testing device for the bonding strength of cement plugs for wellbore sealing according to claim 1, characterized in that, The in-situ testing device for the bonding strength of cement plugs for well casing sealing also includes an outer protective cover (5) and a lower support cover (6) connected at the top and bottom. The sealing vessel is located inside the outer protective cover (5). The main push rod (2) and the auxiliary push rod (3) both pass through the upper part of the outer protective cover (5). The lower push rod (7) passes through the upper part of the lower support cover (6). The lower drive mechanism (25) is located inside the lower support cover (6).

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