Cement sheath crack in-situ repairing method

Abstract

The invention belongs to the technical field of in-situ repair in petroleum well completion, and discloses a cement sheath crack in-situ repair method which comprises the following steps: S1, determining the length and the number of repair sections; s2, drifting and scraping; s3, the cement sheath of the repairing section is shocked to form a seam net; s4, setting is conducted on the lower portion of the repairing section which is located on the lowest portion and not repaired; s5, perforation operation is conducted on the repairing section, and holes are formed; s6, putting down an extrusion pipe and injecting a plugging agent to form a plugging agent layer; s7, the squeezing pipe is lifted upwards to the position above the blocking agent layer, and after setting is conducted on the position above the blocking agent layer, the blocking agent is displaced and squeezed to enter the seam net through the holes; s8, pressure building and cement waiting; s9, if the repairing section does not exist above the blocking agent layer, the pipe is communicated for pressure testing; if the repairing section exists above the blocking agent layer, taking out the squeezing pipe and returning to S4; in-situ repairing of cement sheath crack leakage points under a well is achieved, the repairing success rate and the sealing capacity are improved, and the problem of abnormal annulus pressure is solved.

Description

Technical Field

[0001] The invention relates to the technical field of in-situ repair in petroleum well completion, and in particular to an in-situ repair method for cement sheath cracks. Background Art

[0002] Abnormal annulus pressure occurs in natural gas wells and gas storage wells during operation, which is mostly caused by the failure of downhole barrier seals, including leakage of oil pipe strings and downhole tools, casing strings and cement rings, resulting in gas leakage and affecting the safe operation of gas wells.

[0003] The leaking of the oil tubing and downhole tools can be solved by conventional workover and replacement of the tubing. However, the pressure in the B annulus caused by the leaking of the cement ring is difficult to solve by conventional workover methods, thus reducing the success rate of the repair and the sealing ability. Summary of the invention

[0004] The purpose of the present invention is to provide a cement sheath crack in-situ repair method, so as to realize in-situ repair of cement sheath crack leakage points underground and improve the repair success rate and sealing ability.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] The in-situ repair method of cement sheath cracks comprises the following steps:

[0007] S1. Detect the location and number of leaks and determine the length and number of repair sections;

[0008] S2, well scraping;

[0009] S3, shocking the cement ring of the repair section to generate cracks in the cement ring to form a seam network;

[0010] S4, setting a seal below the repaired section that is located at the bottom and has not been repaired;

[0011] S5, performing perforation operation on the repaired section located at the bottom and not repaired to form holes;

[0012] S6, lowering the squeeze pipe to the repaired section that is located at the bottom and has not been repaired, and injecting the plugging agent to form a plugging agent layer;

[0013] S7, lifting the squeezing pipe to above the plugging agent layer, and setting a seal above the plugging agent layer, and then squeezing the plugging agent through the holes into the seam network;

[0014] S8, holding the pressure and waiting for the plugging agent layer to solidify;

[0015] S9, if the repair section does not exist above the plugging agent layer, then the pipe is opened for pressure testing; if the repair section exists above the plugging agent layer, then the squeeze pipe is taken out and the process returns to S4.

[0016] Preferably, the single repair section extends 5m-10m up and down based on the leak point.

[0017] Preferably, in S3, the cement ring is vibrated by any one of mechanical vibration, blasting vibration or ultrasonic vibration.

[0018] Preferably, in S3, an eccentric percussion drill is repeatedly raised and lowered in the repair section to percuss the cement ring.

[0019] Preferably, the eccentric vibration drill comprises a connecting rod, one end of which can be connected to a drill rod, and the other end of which is eccentrically connected to a rotating disk, and a roller is rotatably connected to the outer circumference of the rotating disk.

[0020] Preferably, in S4, the bridge plug is lowered to below the lowest unrepaired repair section for sealing.

[0021] Preferably, a plurality of holes are evenly distributed along the repair section.

[0022] Preferably, in S6, a packer is provided on the outside of the squeeze tube, and the plugging agent layer is sealed by the packer.

[0023] Preferably, the strength of the plugging agent after solidification and the bonding and sealing strength of the plugging agent are both greater than those of the cement stone ring.

[0024] Preferably, the injection amount of the plugging agent is V,

[0025] V=απhφ(R 2 -r 2 );

[0026] α is the safety factor, α=1.2-1.5; h is the length of a single repair section; φ is the formation porosity; R is the squeeze radius; r is the outer radius of the production casing.

[0027] Beneficial effects of the present invention:

[0028] By shocking the cement ring, cracks are created to form a seam network, providing a flow channel for the plugging agent to enter, thereby increasing the amount of plugging agent entering when plugging the cement ring, improving the repair success rate and sealing ability, achieving in-situ repair of cement ring crack leakage points underground, and solving the problem of abnormal pressure in the B annulus. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1It is a flow chart of the in-situ repair method of cement sheath cracks of the present invention;

[0030] Figure 2 is a schematic diagram of an eccentric jar drill in a production casing in the present invention;

[0031] Figure 3 is a cross-sectional view of the rotating disk and the roller in the present invention;

[0032] Figure 4 It is a schematic diagram of lowering the squeeze pipe to the repair section in the present invention;

[0033] Figure 5 is a schematic diagram of injecting a plugging agent in the present invention;

[0034] Figure 6 It is a schematic diagram of lifting the squeeze pipe and setting it through the packer in the present invention;

[0035] Figure 7 It is a schematic diagram of displacement and squeezing of plugging agent into the seam network in the present invention;

[0036] Figure 8 It is a schematic diagram after the pipe is completed in the present invention.

[0037] In the figure:

[0038] 1. Cement ring; 2. Production casing; 3. Eccentric percussion drill; 31. Connecting rod; 32. Rotating plate; 33. Roller; 4. Drill pipe; 5. Bridge plug; 6. Squeeze pipe; 7. Plugging agent layer; 8. Packer. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0040] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0042] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0043] like Figures 1 to 7 As shown, the present application provides a cement sheath crack in-situ repair method, so that the in-situ repair of the cement sheath 1 crack leakage point can be achieved underground through the method, the problem of abnormal pressure in the B annulus is solved, and the repair success rate and sealing ability are improved. The method includes the following steps:

[0044] S1. The wellbore is inspected by means of distributed optical fiber temperature-noise monitoring, ultrasonic leakage logging, etc., so as to determine the location and number of leaks that need to be repaired, and determine the length and number of repair sections according to the location of the leaks; wherein the length of each repair section can be extended 5m-10m up and down based on the leak point; and it can be understood that if multiple leaks are covered in the process of determining the upward and downward extension of the repair section, the repair section can be determined by extending 5m-10m upward or downward from the leak points at the top and the bottom of the multiple leaks.

[0045] S2. Circulate well pressure, pull out the original well string, scrape the well to ensure that the excess sludge in the wellbore is completely removed, so as to ensure the cleanliness during the repair process and avoid the influence of sludge on the repair.

[0046] S3. Shock the cement sheath 1 that needs to be repaired in all repair sections to generate cracks in the cement sheath 1 to form a seam network, providing a flow channel for the plugging agent to enter later, thereby increasing the amount of plugging agent entering when plugging the cement sheath 1, and improving the repair success rate and sealing ability. Specifically, the cement sheath 1 can be shocked by any of the shock methods of mechanical shock, blasting shock or ultrasonic shock to shock the production casing 2, thereby indirectly shocking the cement sheath 1. Figure 2and Figure 3 As shown, this embodiment adopts a mechanical jarring method, specifically, the eccentric jar drill 3 is repeatedly lifted and lowered in the repair section to jar the cement sheath 1. More specifically, the eccentric jar drill 3 includes a connecting rod 31, one end of which can be connected to the drill rod 4, so that the eccentric jar drill 3 is lifted and lowered through the drill rod 4; the other end of the connecting rod 31 is eccentrically connected to an elliptical rotating disk 32, and a roller 33 is rotatably connected to the outer circumference of the rotating disk 32 to reduce friction with the production casing 2. The center of the drill rod 4 is offset in the static state of the above structure, and the production casing 2 will be jarred during rotary drilling, thereby achieving the purpose of mechanical jarring.

[0047] S4. Repair is carried out from bottom to top in sequence, so as to avoid frequent well-clearing operations; based on this, Figure 4 As shown, the sealing is performed below the repair section that is located at the bottom and has not been repaired. It should be noted that the unrepaired portion here means that the repair section has not been sealed, perforated, or the plugging agent has not been squeezed. Specifically, during the operation, the bridge plug 5 can be lowered to 1m-3m below the repair section that is located at the bottom and has not been repaired for sealing. The bridge plug 5 is a prior art and will not be described in detail.

[0048] S5. After the seal is set below the repair section, the repair section at the bottom and not repaired can be perforated to form holes, so that plugging agent can be injected into the inside through the holes; perforation operation is a mature existing technology and will not be described in detail. It should be noted here that multiple holes can be distributed at intervals along the repair section to increase the efficiency of plugging agent entry.

[0049] S6, such as Figure 4 and Figure 5 As shown, after the perforation operation is completed, the squeeze pipe 6 is lowered to the repair section at the bottom and not repaired, and after being placed above the bridge plug 5, the plugging agent is injected through the squeeze pipe 6 to form a plugging agent layer 7; the type of plugging agent is not specifically limited, and it only needs to meet the requirements that the strength of the plugging agent after solidification and the bonding and sealing strength of the plugging agent are greater than the cement stone ring 1. The injection amount of the plugging agent is V,

[0050] V=απhφ(R 2 -r 2 );

[0051] α is the safety factor, α=1.2~1.5, the safety factor is common knowledge in this field; h is the length of a single repair section; φ is the formation porosity; R is the squeeze radius; r is the outer radius of the production casing 2, which is obtained in the form of calculation.

[0052] S7, such as Figure 6 and Figure 7As shown, the squeezed injection pipe 6 is lifted to above the plugging agent layer 7, and is sealed above the plugging agent layer 7. In this embodiment, a packer 8 is provided on the outside of the squeezed injection pipe 6, and the plugging agent layer 7 is sealed by the above-mentioned packer 8; after the sealing is completed, the squeezed injection plugging agent is replaced and enters the seam network through the holes; it should be noted that the packer 8 is a prior art and will not be described in detail.

[0053] S8, holding the pressure and waiting for the plugging agent layer 7 to solidify.

[0054] S9, if there is no repair section above the plugging agent layer 7, that is, the repair section determined in S1 is one section, then after completing the above S8 operation, drill and grind the solidified plugging agent layer 7 and the bridge plug 5 to pass the pipe. Figure 8 As shown, the completion string is then lowered for pressure testing; in addition, if after completing the above steps, there are still unrepaired repair sections above the plugging agent layer 7, that is, the repair sections determined in S1 are multiple sections, then after completing the above S8 operation, the above squeeze pipe 6 is taken out, and the process returns to S4 to plug the repair section located at the lowest point above and unrepaired and inject the plugging agent, until all the repair sections have been injected with the plugging agent, all the plugging agent layers 7 and bridge plugs 5 that have been drilled and solidified are cleared, and then the completion string is lowered for pressure testing to save process steps.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An in-situ repair method for cement sheath cracks, characterized in that: The steps include: S1. Detect the location and number of leaks and determine the length and number of repair sections; S2, well scraping; S3, shocking the cement ring (1) of the repair section to generate cracks in the cement ring (1) to form a crack network; S4, setting a seal below the repaired section that is located at the bottom and has not been repaired; S5, performing perforation operation on the repaired section which is located at the bottom and has not been repaired, to form holes; S6, lowering the squeeze pipe (6) to the repaired section that is located at the bottom and has not been repaired, and injecting a plugging agent to form a plugging agent layer (7); S7, lifting the squeezing pipe (6) to above the plugging agent layer (7), and setting the plugging agent layer (7) above the plugging agent layer, and then squeezing the plugging agent through the holes into the seam network; S8, holding the pressure and waiting for the plugging agent layer (7) to solidify; S9, if the repair section does not exist above the plugging agent layer (7), the pipe is opened for pressure testing; if the repair section exists above the plugging agent layer (7), the extrusion tube (6) is removed and the process returns to S4.

2. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: The single repair section extends 5m-10m up and down based on the leak point.

3. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: In S3, the cement sheath (1) is vibrated by any one of mechanical vibration, blasting vibration or ultrasonic vibration.

4. The in-situ repair method for cement sheath cracks according to claim 3, characterized in that: In S3, the eccentric percussion drill (3) is repeatedly raised and lowered in the repair section to percuss the cement ring (1).

5. The in-situ repair method for cement sheath cracks according to claim 4, characterized in that: The eccentric percussion drill (3) comprises a connecting rod (31), one end of which can be connected to a drill rod (4), and the other end of which is eccentrically connected to a rotating disk (32), and a roller (33) is rotatably connected to the outer periphery of the rotating disk (32).

6. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: In S4, the bridge plug (5) is lowered to the bottom and below the repaired section that has not been repaired for sealing.

7. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: A plurality of holes are evenly distributed along the repair section.

8. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: In S6, a packer (8) is arranged outside the squeeze tube (6), and the plugging agent layer (7) is sealed by the packer (8).

9. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: The strength of the plugging agent after solidification and the bonding and sealing strength of the plugging agent are both greater than those of the cement stone ring (1).

10. The in-situ repair method for cement sheath cracks according to claim 1, characterized in that: The injection volume of the plugging agent is V, V=απhφ(R 2 -r 2 ); α is a safety factor, α=1.2-1.5; h is the length of a single repair section; φ is the formation porosity; R is the squeezing radius; and r is the outer radius of the production casing (2).

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