Gas storage injection-production well leakage treatment method

Abstract

This invention relates to the field of oil and gas development and discloses a method for controlling leakage in injection and production wells of gas storage facilities. The method includes cement sheath plugging, which comprises: detecting the leakage location of the cement sheath; opening multiple first openings in the well section below the leakage location, the first openings penetrating the oil layer casing, the cement sheath, and the technical casing; injecting a sealing agent through the multiple first openings to form a reinforcing layer below the leakage location; opening multiple second openings in the well section near the leakage location, the second openings penetrating the oil layer casing and partially penetrating the cement sheath; and injecting a sealing agent through the multiple second openings to seal the leakage location. This invention can effectively control cement sheath leakage, avoid annular pressure, and ensure the safe and stable operation of injection and production wells in gas storage facilities.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, specifically to a method for controlling leakage in injection and production wells of gas storage facilities. Background Technology

[0002] The safe control and stable operation of gas storage injection and production wells are crucial for the construction of gas storage facilities, safe and stable production, and even for ensuring the stable and controllable national gas storage. The operation mode of gas storage injection and production wells in a single injection-production cycle is divided into the injection period, the balancing period, and the production period.

[0003] The inventors of this application recognized that the operating environment of gas storage injection-production wells is more complex and the safety requirements are more stringent than those of ordinary oil and gas wells, which places higher demands on leakage control in gas storage injection-production wells. During the injection and production process, due to alternating injection and production conditions, the expansion and deformation of the tubing and cement sheath can easily lead to cement sheath leakage, resulting in pressure in the annulus (B annulus) between the oil layer casing and the technical casing, affecting the daily safe and stable operation of the injection-production well.

[0004] Therefore, it is necessary to propose a solution that can effectively control leakage in cement rings. Summary of the Invention

[0005] The main objective of this invention is to provide a method for treating leakage in gas storage injection and production wells, so as to solve the problem of pressure in the B annulus caused by cement annulus leakage in gas storage injection and production wells.

[0006] According to one aspect of the present invention, a method for treating leakage in gas storage injection and production wells is provided, comprising performing cement sheath sealing, wherein performing cement sheath sealing includes: Inspect the leakage points of the cement ring; Multiple first openings were made in the well section located below the leakage site. The first openings penetrated the oil layer casing, cement sheath, and technical casing. A sealing agent is injected through multiple first openings to form a reinforcing layer on the underside of the leak. Multiple second openings were made in the well section near the leakage site. The second openings penetrated the oil layer casing and partially penetrated the cement sheath. The leak was sealed by injecting a sealant through multiple secondary openings.

[0007] According to one embodiment of the present invention, the diameter of the first opening is smaller than the diameter of the second opening.

[0008] According to one embodiment of the present invention, the diameter of the first opening is 10~15mm, and the diameter of the second opening is 30~35mm.

[0009] According to one embodiment of the present invention, the first opening is obtained by perforation, and the second opening is obtained by drilling.

[0010] According to one embodiment of the present invention, 12 to 15 second openings are made within an axial length range of 5 to 10 m.

[0011] According to one embodiment of the present invention, the plurality of first openings and the plurality of second openings are all spirally distributed.

[0012] According to one embodiment of the present invention, the second opening penetrates the radial central region of the cement ring.

[0013] According to one embodiment of the present invention, the depth of the first opening is 800~900mm, and the depth of the second opening is 450~550mm.

[0014] According to one embodiment of the present invention, the permeability of the sealing agent is less than 0.5 × 10⁻⁶. -6 mD, compressive strength greater than 70MPa, tensile strength at least 60MPa, flexural strength at least 45MPa.

[0015] According to one embodiment of the present invention, the sealing agent is a resin.

[0016] According to one embodiment of the present invention, a fiber optic sensor is used to detect the leakage site.

[0017] According to one embodiment of the present invention, before performing cement sheath plugging, the method further includes performing reservoir temporary plugging, well killing, and tripping the injection and production tubing in sequence.

[0018] According to one embodiment of the present invention, before performing cement sheath plugging, the method further includes wellhead hanger plugging, injection-production tubing plugging, and oil layer casing plugging.

[0019] According to one embodiment of the present invention, sealing a wellhead hanger includes: performing an airtightness test on the wellhead hanger, and sealing the leak when a leak is detected.

[0020] According to one embodiment of the present invention, plugging leakage in the injection-production tubing includes: The pressure recovery test method is used to determine whether there is a leak in the injection and production tubing; When a leak is detected, the location of the leak in the injection and production tubing is detected using fiber optic sensors; Use a sealant to plug the leak.

[0021] According to one embodiment of the present invention, the plugging agent is a differential pressure activated plugging agent.

[0022] According to one embodiment of the present invention, sealing the leak location with a sealing agent includes: The injection / production tubing with packer is lowered into the well to the predetermined position. Inject clean water for reverse circulation well washing; Reverse circulation injection of the sealant ensures that the sealant covers the leak location; The packer is seated to seal the annulus between the injection / production tubing and the reservoir casing, followed by pressure sealing.

[0023] According to one embodiment of the present invention, oil layer casing plugging includes: The oil layer casing is roughly divided into multiple first pipe sections, and each of the multiple first pipe sections is checked for leakage. The first pipe section with a leak is finely divided into multiple second pipe sections, and the leak is detected in each of the multiple second pipe sections to determine the location of the leak. Seal the leak location.

[0024] According to one embodiment of the present invention, the first leak location is detected and sealed in a top-down order, and then the next leak location is detected and sealed, until all leak locations are detected and sealed.

[0025] According to one embodiment of the present invention, oil layer casing leak sealing includes: dividing the area using a packer and determining whether a leak exists based on the pressure drop.

[0026] In the technical solution of this invention, a first opening is first made in the well section located below the leakage point of the cement sheath, penetrating the oil layer casing, cement sheath, and technical casing. A sealing agent is injected through the first opening, forming a transverse reinforcing layer below the leakage point as an isolation barrier, ensuring the sealing effect. Then, a second opening is made in the well section near the leakage point, penetrating the oil layer casing and partially extending into the cement sheath. The sealing agent is injected through the second opening, allowing it to flow to the leakage point of the cement sheath for sealing. Therefore, through the technical solution of this invention, leakage in the cement sheath can be thoroughly and effectively controlled, preventing annular pressure and ensuring the safe and stable operation of the gas storage injection and production wells. Attached Figure Description

[0027] 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.

[0028] Figure 1 A flowchart illustrating a method for controlling leakage in gas storage injection and production wells according to an embodiment of the present invention is shown. Figure 2 A flowchart illustrating a method for controlling leakage in gas storage injection and production wells according to another embodiment of the present invention is shown. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] A gas storage injection-production well typically consists of, from the inside out, the injection-production tubing string, the oil layer casing (also called the production casing), the technical casing, and the surface casing. A cement sheath, which serves to seal and secure the oil layer casing and the technical casing, separates the two. The annulus between the injection-production tubing string and the oil layer casing is called the A annulus, the annulus between the oil layer casing and the technical casing is called the B annulus, and the annulus between the technical casing and the surface casing is called the C annulus.

[0032] refer to Figure 1 This invention proposes a method for treating leakage in gas storage injection and production wells, which includes cement sheath sealing. The cement sheath sealing process includes the following steps: S1, detect the leakage points of the cement ring; S2, multiple first openings are made in the well section located below the leakage site. The first openings penetrate the oil layer casing, cement sheath and technical casing. S3, a sealing agent is injected through multiple first openings to form a reinforcing layer on the underside of the leakage site; S4, multiple second openings are made in the well section near the leakage site. The second openings penetrate the oil layer casing and partially penetrate the cement sheath. The area near the leakage site can be a position directly opposite the leakage site or a position slightly above the leakage site. The second opening is located above the first opening. S5, sealant is injected through multiple second openings to seal the leak.

[0033] In an embodiment of the present invention, a first opening is first made in the well section located below the leakage point of the cement sheath, penetrating the oil layer casing, cement sheath, and technical casing. A sealing agent is injected through this first opening, forming a transverse reinforcing layer (cut-off plane) below the leakage point as an isolation barrier, making the sealing more thorough. Then, a second opening is made in the well section near the leakage point, penetrating the oil layer casing and partially extending into the cement sheath. The sealing agent is injected through this second opening, allowing it to flow to the leakage point of the cement sheath for sealing. Therefore, the technical solution of the present invention can effectively treat cement sheath leakage, avoid annular pressure, and ensure the safe and stable operation of gas storage injection and production wells.

[0034] In some embodiments, fiber optic sensors are used to detect leaks. Leaking substances cause changes in the ambient temperature; the temperature distribution of the cement sheath can be continuously monitored using fiber optic temperature sensors, and leak locations can be determined based on temperature anomalies. However, this invention is not limited to this; in addition to fiber optic leak detection technology, other suitable leak detection technologies, such as acoustic leak detection technology, can also be used to detect leaks in the cement sheath. Combining multiple leak detection technologies can lead to more accurate leak detection.

[0035] In some embodiments, the diameter of the first opening is smaller than the diameter of the second opening. In this invention, the first opening is primarily used for injecting sealing agent to form an auxiliary reinforcing layer, while the second opening is used for injecting sealing agent to fill and seal the leakage site. Therefore, the second opening is required to be able to sufficiently inject sealing agent to completely seal the leakage site of the cement ring, thus the diameter of the second opening is set to be larger than the diameter of the first opening. In some embodiments, the diameter of the first opening is 10-15 mm, and the diameter of the second opening is 30-35 mm.

[0036] In some embodiments, the first opening is obtained by perforation, and the second opening is obtained by drilling. In this invention, the first opening penetrates the oil layer casing, cement sheath, and technical casing, and can be formed by quickly and effectively perforating these layers with a perforating gun. In a specific embodiment, a Φ127 perforating gun is used, with a perforation density of 16 holes / m. The second opening penetrates the oil layer casing and partially into the cement sheath, but does not penetrate the technical casing. If perforation is used, it would be difficult to control the hole depth; therefore, radial drilling technology can be used to precisely drill the second opening.

[0037] In some embodiments, the second opening penetrates the radial center region of the cement ring to ensure that the sealant can flow sufficiently and effectively to the leakage point of the cement ring. In some embodiments, the depth of the first opening is 800-900 mm, and the depth of the second opening is 450-550 mm.

[0038] In some embodiments, 12 to 15 second openings are made within an axial length range of 5 to 10 m.

[0039] In some embodiments, the plurality of first openings and the plurality of second openings are spirally distributed.

[0040] This invention, by designing the depth, diameter, distribution density, and distribution pattern of the first and second openings, ensures that the sealing agent injected through the first and second openings can effectively seal the leakage parts of the cement ring.

[0041] To ensure the plugging agent can flow smoothly within the cement sheath, it must possess excellent penetrability and easily enter micro-fractures. Simultaneously, the operating environment of the gas storage injection and production wells also places high demands on the strength of the plugging site. In some embodiments of this invention, the permeability of the plugging agent used is less than 0.5 × 10⁻⁶. -6 The mD (compressive strength) is greater than 70 MPa, the tensile strength is at least 60 MPa, and the flexural strength is at least 45 MPa. In some embodiments, the sealing agent is a resin. Only some resin-based sealing agents can meet the performance requirements of this invention.

[0042] In some embodiments, prior to cement sheath plugging, the method of the present invention further includes sequentially performing reservoir temporary plugging, well control, and tripping the injection-production tubing. Tripping the injection-production tubing facilitates operations from within the oil reservoir casing to create the first and second openings. Well control ensures the smooth tripping of the injection-production tubing. Reservoir temporary plugging prevents the leakage control process from impacting the reservoir.

[0043] refer to Figure 2 In some embodiments, the method of the present invention further includes pre-plugging before cement sheath sealing, which includes wellhead hanger sealing, injection-production tubing sealing, and oil layer casing sealing. The operating environment of gas storage injection-production wells is complex and has strict safety requirements; pre-plugging ensures the safety and effectiveness of subsequent cement sheath sealing.

[0044] In some embodiments, plugging a wellhead hanger includes: performing an airtightness test on the wellhead hanger and sealing the leak when a leak is detected.

[0045] In some embodiments, plugging the injection-production tubing includes: determining whether there is a leak in the injection-production tubing using a pressure recovery test method; when a leak is determined to exist, detecting the leak location in the injection-production tubing using a fiber optic sensor; and sealing the leak location using a plugging agent.

[0046] In some embodiments, the plugging agent is a differential pressure activated plugging agent.

[0047] In some embodiments, sealing the leak location with a plugging agent includes: running an injection-production string with a packer into a predetermined position in the well; injecting clean water for reverse circulation well flushing; injecting the plugging agent in reverse circulation so that the plugging agent covers the leak location; setting the packer to seal the annulus between the injection-production string and the oil layer casing, and then performing pressure sealing.

[0048] In some embodiments, plugging leaks in the oil layer casing includes: roughly dividing the oil layer casing into multiple first pipe segments and detecting whether there is a leak in each of the multiple first pipe segments; finely dividing the leaking first pipe segment into multiple second pipe segments and detecting whether there is a leak in each of the multiple second pipe segments, thereby determining the location of the leak; and sealing the leak location.

[0049] In some embodiments, the first leak location is detected and sealed in a top-down order, and then the next leak location is detected and sealed, until all leak locations are detected and sealed.

[0050] In some embodiments, plugging the oil layer casing includes: using a packer to divide the area and determining whether a leak exists based on the pressure drop.

[0051] In one specific embodiment, the method for controlling leakage in gas storage injection and production wells of the present invention includes the following steps: 1. Screening of plugging agents Based on site requirements, the rheological properties, compressive strength, and curing time of different epoxy resin and curing agent compositions were evaluated indoors. The resin sealant with the following characteristics was selected: low viscosity-shear properties, absence of solid particles, easy penetration into various gaps (especially micron-sized cracks or porous formations), strong penetration, high compressive strength after solidification, and permanent sealing. Table 1 shows the performance indicators of the selected resin sealant.

[0052] Table 1 Performance Indicators of Resin Sealant

[0053] 2. Treatment process for the B-ring void cement ring (1) For wells under pressure in the annulus, the root cause of leakage in the well under pressure is determined by pressure recovery test. If it is determined to be leakage in the injection and production tubing, differential pressure activation plugging is carried out. (2) By using fiber optic leak detection and other methods, the abnormal points of acoustic waves and temperature in the injection and production tubing are determined. After eliminating the temperature and pressure fluctuations caused by abnormal well conditions, the abnormal pressurized points are identified as the leakage locations of the tubing. (3) Run the tubing with packer to the predetermined position, flush the well with clean water in reverse circulation for 1.5 weeks, inject differential pressure to activate the plugging agent (calculate the amount to be used after the location of the leak is determined), cover the leak with the plugging agent, set the packer, close the A annulus, and verify the setting effect of the packer; wherein, a 50m clean water barrier and a 50m plugging agent block are formed at the top of the packer; (4) The pump truck uses a sealant to slowly pressurize to 20MPa and begin pressurizing and sealing. Depending on the pressure drop, pressurize once every 2-3 hours and maintain the pressure for more than 8 hours. (5) Depressurize to 0, let stand for 2 hours, then pressurize again to 20MPa and wait for more than 2 hours to seal; (6) Depressurize, flush the well with clean water, and the leak plugging work is completed.

[0054] 3. Post-sealing test (1) After the construction is completed, two well pressure tests shall be carried out within 48 hours to ensure the sealing effect.

[0055] (2) Conduct pressure recovery tests or fiber optic noise tests to confirm the effectiveness of sealing the leak location.

[0056] (3) Trial injection operation, continuous monitoring of annular pressure. If there is no pressure in the annulus, it will be put into formal production.

[0057] (4) Temporary reservoir plugging: The 1m of reservoir pumped in is temporarily plugged using an injection-production tubing string. 3 ~2m 3 The temporary plugging system was completely squeezed into the formation, effectively sealing the pores.

[0058] (5) Requirements for temporary plugging agent: The system is a viscous liquid before pumping. According to the construction requirements, it can be cross-linked within 1.5~3h to form a "gel plug" that can isolate the formation fluid from the well fluid. The colloid can be broken down and dissociated in about 30 days (at a temperature of 70℃), and finally become a low-viscosity viscous liquid for backflow.

[0059] 4. Measuring liquid level and controlling wells Before construction, the density of the kill fluid is reasonably designed based on the wellhead pressure and the measured fluid level in the wellbore. The kill fluid is then injected from the injection and production tubing to kill the well. The pump pressure changes are monitored. After successful kill, a temporary plugging agent is added for temporary plugging.

[0060] Technical requirements: The observation time after well control must be at least 1.5 times longer than the time required for operations such as installing the well sealer, and there must be no well control risks such as leakage or gas intrusion during this period. 5. Install and debug the well sealing device Install the blowout preventer and perform a pressure test as required.

[0061] Removing the gas injection string: Apply a pulling force of 1000~2000 lbs (4.5~9.1 kN) to the original weight of the string, rotate the string 10 to 12 times clockwise, and try to lift it. If the reverse connection is successful, remove the oil pipe and anchoring seal device. If the reverse connection is unsuccessful, investigate the cause and discuss and formulate a solution.

[0062] 6. Replace the wellhead sealing kit After the wellhead is pulled out, the wellhead is filled with fluid to meet the requirements for disassembly and assembly. Then, the gas production four-way valve is removed, and the 2FZ18-35+FH18-35 wellhead sealer assembly is installed and tested.

[0063] Note: If the previous casing head sealing was not up to standard, remove the cover flange in this procedure, check the casing mounting condition, replace the seals, and then perform wellhead sealing test until it is up to standard.

[0064] 7. Well cleaning and dredging Lower a Φ152mm gauge to the packer, check the integrity of the upper wellbore, and circulate the well for 1-2 cycles.

[0065] 8. Drilling and grinding packers: (1) Determine the milling method according to the packer type.

[0066] (2) Mill the packer. Based on the advance and return of the material, determine whether the clips on the packer have been worn off.

[0067] (3) Retrieve the packer and the tubing below it.

[0068] 9. Leak detection and treatment in oil layer casing If the full wellbore pressure test fails, use a packer to locate and test for leaks at suspected leak points in the wellbore (including the sealing performance of the ash plug) to determine the exact location of the leak.

[0069] Find the omissions: (1) General leak detection: Set the packer every 500m or so, close the wellhead and test the pressure at 20MPa, record the pressure drop for 10-30 minutes, and analyze whether there is a leak in each section based on the pressure drop of each section and the known data.

[0070] (2) Detailed leak finding: Based on the general leak finding data, use packers from top to bottom to determine the exact location of the first leak point, and test the pressure to determine the absorption capacity.

[0071] (3) Squeezing method: If there are multiple leaks, choose to seal them one by one from top to bottom. After passing the inspection, proceed to the next leak and seal it.

[0072] (4) Technical requirements: Determine the specific location and number of leaks in the oil layer casing.

[0073] 10. Cement ring reinforcement and sealing – technical sleeve cement ring (1) Principles for selecting perforation location: Based on ultrasonic imaging logging, select well sections with poor cementing quality and obvious cement sheath channels; and prioritize sand layers.

[0074] (2) Perforation location: Before construction, the perforation location needs to be re-evaluated based on the re-measurement results.

[0075] (3) Perforation method: Use gunpowder perforation to perforate the double-layer casing of oil sleeve and technical sleeve, squeeze out the plugging agent to seal the C annulus and B annulus outside the technical sleeve.

[0076] 11. Perforation, absorption measurement, and plugging: (1) Cable transmission: In the designed well section, Φ127 perforating gun is used for perforation, with a hole diameter of 12mm, a hole density of 16 holes / m, a 6-phase spiral perforation pattern, and a hole depth of 850mm. (2) Run the tubing string to the bottom boundary of the perforated layer, close the wellhead and measure the absorption and injection pressure; (3) Select the plugging agent according to the absorption amount and plug it.

[0077] The principle for selecting the best location for casing openings is as follows: in the lower part of the caprock, below the permanent packer, to ensure the integrity of the casing above the packer and avoid pressurization in the A annulus, which could lead to pressurization in the B annulus; based on ultrasonic imaging logging, select well sections with poor cementing quality and obvious cement sheath channels.

[0078] 12. Sleeve opening method: (1) Using radial drilling technology, only the oil layer casing is drilled through, but the technical casing is not drilled through, with a hole depth of about 500 mm; (2) Drill 12 to 15 holes (within 5 to 10 m) in the designed well section, with a hole diameter of 30 to 32 mm, and use a spiral hole arrangement; (3) Select the appropriate plugging agent according to the inhalation volume, seal it, and test the pressure.

[0079] 13. Retest integrity and restore injection / production tubing (1) Full wellbore pressure test: Use clean water for pressure test. The pressure test standard is 1.1 times the operating pressure of the gas storage tank (29MPa, stabilize pressure for 30min, pressure drop ≤0.5MPa is acceptable).

[0080] (2) Gas pressure test to check the pressure of the B annulus: Nitrogen gas was used to replace the liquid in the wellbore, and natural gas was used to pressurize the pipeline to 20~23MPa to check the pressure of the B annulus and to preliminarily evaluate the sealing effect.

[0081] (3) Drilling out cement plugs / bridge plugs: When drilling plugs, pay attention to the risks of leakage and gas intrusion into the well.

[0082] 14. Run the completion string Only after verifying no leakage during well control can the injection and production tubing be pulled out and the packer drilled. After inspecting the wellbore and cementing quality, a plug is injected and the entire wellbore is pressure tested. If it fails, casing differential pressure is used for plugging. If it passes, annulus B and C are sealed, mainly to prevent gas from escaping along the outer casing of annulus C and to block annulus B.

[0083] For the sealing of the B annulus near the wellhead, a combination of differential pressure plugging agent and resin plugging agent was used. First, differential pressure plugging agent was used to seal the free section of casing and the cement sheath surface. After removing excess plugging agent, a resin plug was applied to the upper part of the cement sheath to improve the sealing performance and effective life of the cement sheath.

[0084] 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 method for controlling leakage in injection and production wells of a gas storage facility, characterized in that, This includes performing cement ring sealing, wherein performing cement ring sealing includes: Inspect the leakage points of the cement ring; Multiple first openings are made in the well section located below the leakage site, and the first openings penetrate the oil layer casing, cement sheath and technical casing; A sealing agent is injected through multiple first openings to form a reinforcing layer on the underside of the leakage site; Multiple second openings are made in the well section near the leakage site. The second openings penetrate the oil layer casing and partially penetrate the cement sheath. The sealing agent is injected through multiple second openings to seal the leakage site.

2. The method according to claim 1, characterized in that, The diameter of the first opening is smaller than the diameter of the second opening.

3. The method according to claim 2, characterized in that, The diameter of the first opening is 10~15mm, and the diameter of the second opening is 30~35mm.

4. The method according to claim 1, characterized in that, The first opening is obtained by perforation, and the second opening is obtained by drilling.

5. The method according to claim 1, characterized in that, 12 to 15 second openings are made within an axial length range of 5 to 10 m.

6. The method according to claim 1, characterized in that, The plurality of first openings and the plurality of second openings are all spirally distributed.

7. The method according to claim 1, characterized in that, The second opening penetrates the radial center region of the cement ring.

8. The method according to claim 1, characterized in that, The depth of the first opening is 800~900mm, and the depth of the second opening is 450~550mm.

9. The method according to claim 1, characterized in that, The permeability of the plugging agent is less than 0.5 × 10⁻⁶. -6 mD, compressive strength greater than 70MPa, tensile strength at least 60MPa, flexural strength at least 45MPa.

10. The method according to claim 9, characterized in that, The sealing agent is a resin.

11. The method according to claim 1, characterized in that, The leak was detected using a fiber optic sensor.

12. The method according to claim 1, characterized in that, Before performing cement sheath plugging, the method also includes performing reservoir temporary plugging, well killing, and tripping the injection and production tubing in sequence.

13. The method according to claim 1, characterized in that, Prior to cement sheath sealing, the method also includes wellhead hanger sealing, injection / production tubing sealing, and oil layer casing sealing.

14. The method according to claim 13, characterized in that, The process of plugging the wellhead hanger includes: performing an airtightness test on the wellhead hanger, and sealing the leak when a leak is detected.

15. The method according to claim 13, characterized in that, The process of plugging the injection / production tubing includes: The pressure recovery test method is used to determine whether there is a leak in the injection and production tubing; When a leak is detected, the location of the leak in the injection and production tubing is detected by a fiber optic sensor. The leak was sealed using a sealant.

16. The method according to claim 15, characterized in that, The plugging agent is a differential pressure activated plugging agent.

17. The method according to claim 15, characterized in that, The process of sealing the leak location with a sealing agent includes: Lower the injection / production tubing with packer to the predetermined position in the well; Inject clean water for reverse circulation well washing; The sealant is injected in a reverse circulation manner so that it covers the leak location; The packer is seated to seal the annulus between the injection / production tubing and the reservoir casing, followed by pressure sealing.

18. The method according to claim 13, characterized in that, The process of plugging the oil layer casing includes: The oil layer casing is roughly divided into multiple first pipe sections, and each of the multiple first pipe sections is tested for leakage. The first pipe segment with a leak is finely divided into multiple second pipe segments, and the leak location is determined by detecting whether there is a leak in each of the multiple second pipe segments. The leak location was sealed.

19. The method according to claim 18, characterized in that, Following a top-down sequence, after detecting and sealing the first leak location, the next leak location is detected and sealed, and so on, until all leak locations are detected and sealed.

20. The method according to claim 18, characterized in that, The process of plugging the oil layer casing includes: using a packer to divide the area and determining whether a leak exists based on the pressure drop.

Images