Method and device for repairing deformed casing pipe

Abstract

The invention discloses a method and device for repairing a deformed casing, and the method comprises the steps: carrying out the perforation operation of a casing deformation point of the casing, and carrying out the perforation of the casing to form a cavity between the casing and cement and rock behind the casing, and the cavity is used for releasing the extrusion force of a stratum at the casing deformation point on the casing; and performing casing shaping and patching operation. The repairing device comprises a liquid tank, a sand mixing pry, high-pressure pumping equipment, coiled tubing equipment, a hydraulic spray gun and wellhead equipment, a stop valve is arranged between the liquid tank and the high-pressure pumping equipment, and the hydraulic spray gun and the coiled tubing penetrate through the wellhead equipment and extend into a shaft. According to the method, the hydraulic spray gun is firstly used for perforation operation, and the perforation cavity is formed at the deformation point, so that the extrusion acting force of a stratum on the casing is eliminated, the expansionary force required by casing shaping is greatly reduced, and the problem of repairing the deformed casing under the working conditions of high confining pressure and high ground stress is solved.

Description

Technical Field

[0001] The invention relates to the technical field of repairing deformed casing of oil and gas wells, and in particular to a repairing method and a repairing device for a deformed casing. Background Art

[0002] The Changning-Weiyuan National Shale Gas Demonstration Area has been initially built in the Sichuan Basin. Shale gas development mainly uses horizontal wells. The vertical depth of the wells is usually between 2500-4000 meters depending on the specific geological conditions, and the horizontal section is about 2000 meters. Usually, there are about 20 stages of fracturing, and the length of a single stage is 70 meters. During the multi-stage volume fracturing of horizontal wells, it was found that the casing of the oil layer was seriously damaged. Studies have shown that the large-volume, high-pressure, long-term, and multi-stage repeated continuous volume fracturing operations of shale gas fracturing construction are the cause of casing damage. As a result, during the operation, the non-uniformly distributed load repeatedly squeezes the casing, causing shear sliding in the formation, especially in the cracks. The performance is more prominent, which makes the weak points of the casing unstable first and plastic deformation occurs, causing casing damage. More than 30% of horizontal wells have casing deformation problems during the fracturing process. The deformation or damage of the downhole casing will not only affect the fracturing operation and production system of the gas well, causing a decrease in production or even abnormal production, but also increase the abnormal wear of the tubing, increase production costs, shorten service life, and cause significant production economic losses. The damage problem of downhole casing has always been one of the serious problems plaguing the development of oil and gas fields.

[0003] At present, casing deformation is common in deep shale gas wells in Sichuan, and the repair of deformed casing faces the following difficulties:

[0004] 1. The cause of casing deformation is mostly stratum slippage induced by fracturing construction. The ground stress continues to act on the casing. If the shaping tool is used to reset the casing, it is necessary to overcome the ground stress and the casing deformation force at the same time. The existing casing shaping tools cannot provide the required expansion force.

[0005] 2. Mechanical milling repair technology is not affected by formation stress, but mechanical milling requires the use of large equipment such as workover rigs, with a long construction period and high cost. In addition, most casings are 140 steel grade with extremely high strength, and the milling footage is slow, resulting in extremely low operating efficiency.

[0006] At present, there are three technical methods for shaping and repairing the deformed casing in the well: explosive shaping, mechanical shaping, and hydraulic shaping:

[0007] Explosive shaping is to place explosives at the fault or deformed section of the casing. After the explosives explode, an explosion shock wave is quickly formed on the inner surface of the casing. The high-pressure shock wave generated by the explosion of the explosives causes the casing to expand outward rapidly in a relatively short period of time, thereby repairing the deformed casing and opening the passage. Explosive shaping is restricted by the external constraints of the casing, the amount of explosives is difficult to control, and the non-directional impact of the blasting force will inevitably cause unforeseen secondary damage to the casing.

[0008] Mechanical shaping includes pear-shaped expansion technology, rotary jarring technology, etc., which use the weight of the pipe to perform shaping. There are problems such as limited tonnage and insufficient shaping force. In addition, mechanical shaping requires the use of large equipment such as workover rigs, which has a long construction period and high cost.

[0009] Hydraulic shaping is a process in which high-pressure liquid pushes the shaping tool to expand radially outward under the action of hydraulic pressure to repair the deformed casing. However, it is limited by the wellbore confining pressure and when the local stress is high, there are problems such as ball jamming and drill jamming.

[0010] For deep shale gas wells with high ground stress and high confining pressure, the existing deformation casing repair methods cannot meet the requirements.

[0011] In view of this, this patent application is filed. Summary of the invention

[0012] In order to solve the above problems, the present invention provides a method for repairing deformed casing and also constructs a deformed casing repair device, which is used to solve the problem of difficulty in repairing deformed casing under working conditions such as high ground stress and high confining pressure during the development of oil, gas and water wells. The method has the advantages of high efficiency, low cost and good controllability.

[0013] The first object of the present invention is to provide a method for repairing a deformed casing, comprising:

[0014] Perform perforation operations on the casing change point, perforate the casing to form a cavity between the casing and the cement and rock behind it, so as to release the squeezing force of the formation at the casing change point on the casing;

[0015] Casing shaping and patching operations.

[0016] In the embodiment of the present invention, the inventive concept of "generating a cavity at the deformation point of the casing to eliminate the contact surface stress" is adopted, and the ground stress acting on the outer wall of the casing by the sandblasting and perforating operation is eliminated. This method has high efficiency, low cost, good controllability and high operation safety.

[0017] In an optional embodiment, when perforating the casing change point of the casing, a uniformly mixed abrasive suspension is first used for perforating, and then a friction-reducing liquid without abrasive is used for circulating self-priming perforating;

[0018] The uniformly mixed abrasive suspension is a mixture of a drag reducing liquid and an abrasive.

[0019] In the embodiment of the present invention, the perforation operation is divided into ground sanding perforation operation and self-priming perforation operation. First, the ground sanding perforation operation is performed, and the drag reduction liquid with abrasive is used for perforation. Then, the self-priming perforation operation is performed, and the drag reduction liquid without abrasive is used for perforation. On the one hand, this method greatly reduces the amount of abrasive used, reduces the wear and tear on the coiled tubing, ground equipment and pipelines, has high safety and low operating costs; on the other hand, abrasives will reduce the fluidity of the liquid and increase the extended pressure loss. The self-priming perforation can reduce the pressure loss during the liquid transportation process, achieve a higher jet pressure, and help improve the jet effect.

[0020] In an optional embodiment, the cyclic self-priming perforating operation includes: mixing low-velocity crushed debris formed by water pressure and abrasive with high-velocity drag-reducing fluid, accelerating the mixture and spraying it onto the casing.

[0021] In the embodiment of the present invention, a self-priming perforating operation is adopted, and the abrasive particles injected in the ground perforating operation can be used to cooperate with the high-speed resistance-reducing liquid to be cyclically sucked in / ejected, which not only reduces the use of abrasives, but also achieves the purpose of forming a perforating cavity.

[0022] In an optional embodiment, the cavity is a concave ellipsoidal structure.

[0023] In an optional embodiment, the casing shaping is to perform expansion operation on the deformation point of the casing to restore the casing diameter;

[0024] The patching operation is to close the casing holes and reinforce them.

[0025] The second object of the present invention is to provide a repair device for the deformed casing as described in any one of the above items, comprising a liquid tank, a sand mixing skid, a high-pressure pumping device, a coiled tubing device, a hydraulic spray gun, and a wellhead device, wherein the input pipeline of the sand mixing skid is connected to the liquid tank, a stop valve is provided between the liquid tank and the high-pressure pumping device, the input end of the high-pressure pumping device is connected to the output pipeline of the sand mixing skid, a coiled tubing is wound around the coiled tubing device, a high-pressure inlet of the coiled tubing device is connected to the coiled tubing, the hydraulic spray gun is connected to the end of the coiled tubing, and the hydraulic spray gun and the coiled tubing pass through the wellhead device and extend into the wellbore.

[0026] In an optional embodiment, a self-priming nozzle is fixedly provided on the hydraulic spray gun, and the self-priming nozzle includes a front nozzle and a rear nozzle, the front nozzle is sleeved in the rear nozzle, a flow channel is provided inside the front nozzle, a mixing chamber is provided inside the rear nozzle, an injection hole is provided at the end of the rear nozzle, and a suction hole is also provided in the rear nozzle, the suction hole is located on the side of the mixing chamber, the flow channel is connected with the mixing chamber, and the injection hole and the suction hole are both connected with the mixing chamber.

[0027] In an optional embodiment, the flow channel is a tapered straight flow channel, the end of the flow channel close to the mixing chamber is a straight end, and the end away from the mixing chamber is a tapered end, the suction hole is set at an angle to the mixing chamber, and a return pipeline is connected to the wellhead equipment.

[0028] In an optional embodiment, the aperture of the straight end of the front nozzle is d, and the aperture of the injection hole of the rear nozzle is D, and the value of D is 1.2 to 1.8 times the value of d to ensure a better jet effect.

[0029] In an optional embodiment, the diameter of the suction hole is b, and the gap size between the rear nozzle and the hydraulic spray gun is a, and the value of a is smaller than the value of b, which acts as a filter to prevent the suction hole from being blocked.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] In the embodiment of the present invention, a small-diameter hydraulic spray gun is creatively used to perform perforation operations first, forming a perforation cavity at the deformation point, eliminating the squeezing force of the formation on the casing, greatly reducing the expansion force required for casing shaping, and solving the problem of repairing deformed casing under high confining pressure and high ground stress conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0033] Figure 1 A schematic structural diagram of a repair device for a deformed casing provided by an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a hydraulic spray gun provided by an embodiment of the present invention;

[0035] Figure 3 for Figure 2 A magnified view of the local structure at X in the middle;

[0036] Figure 4 A self-priming jet working principle diagram of a deformed casing repair method provided by one embodiment of the present invention;

[0037] Figure 5 A schematic diagram of a deformed casing repair method provided by an embodiment of the present invention;

[0038] In the figure:

[0039] 1-Liquid tank; 2-Sand mixing skid; 3-Stop valve; 4-High-pressure pumping equipment; 5-Continuous tubing equipment; 6-Continuous tubing; 7-Wellhead equipment; 8-Flowback pipeline; 9-Hydraulic spray gun; 11-Front nozzle; 12-Rear nozzle; 13-Flow channel; 14-Mixing chamber; 15-Suction hole; 16-Injection hole. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0042] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0043] In the description of the embodiments of the present application, the terms "center", "up", "down", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inside", "outside", "front", "back", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the application are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are merely for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0044] In the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "opened", "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] like Figure 1 , 2 As shown in , 3, a repair device for a deformed casing comprises a liquid tank 1, a sand mixing skid 2, a stop valve 3, a high-pressure pumping device 4, a coiled tubing device 5, a coiled tubing 6, a hydraulic spray gun 9, and a wellhead device 7. The liquid tank 1, the sand mixing skid 2, the stop valve 3, the high-pressure pumping device 4, and the coiled tubing device 5 constitute a surface device. The liquid tank 1 stores a drag reducing liquid, and the input pipeline of the sand mixing skid 2 is connected to the liquid tank 1. The input end of the high-pressure pumping device 4 is connected to the output pipeline of the sand mixing skid 2, and a stop valve 3 is provided between the liquid tank 1 and the high-pressure pumping device 4. A coiled tubing 6 is wound around the coiled tubing device 5, and the coiled tubing device 5 and the coiled tubing 6 are connected by a union, and the high-pressure inlet of the coiled tubing device 5 is connected to the output end of the high-pressure pumping device 4 through a pipeline, and the high-pressure inlet is connected to the coiled tubing 6. A small-diameter hydraulic spray gun 9 is connected to the coiled tubing 6, and the coiled tubing 6 passes through the wellhead device 7 and extends into the wellbore.

[0046] In some embodiments, a number of self-priming nozzles are provided on the hydraulic spray gun 9, and the self-priming nozzles are threadedly connected to the hydraulic spray gun 9, and thread glue is used to prevent loosening. The self-priming nozzle consists of a front nozzle 11 and a rear nozzle 12. The front nozzle 11 is sleeved inside the rear nozzle 12, and the interior of the front nozzle 11 is a tapered straight flow channel 13, with one end close to the mixing chamber 14 being a straight end and the end away from the mixing chamber 14 being a tapered end. The tapered straight flow channel 13 has the advantages of being easy to process and having a high flow coefficient. The interior of the rear nozzle 12 is a mixing chamber 14, and an injection hole 16 is provided at the end of the rear nozzle 12. Several suction holes 15 are also distributed in the radial direction of the rear nozzle 12, and each suction hole 15 is located on the side of the mixing chamber 14 and arranged at a certain angle with the mixing chamber 14. The flow channel 13 is connected to the mixing chamber 14, and the injection hole 16 and the suction hole 15 are both connected to the mixing chamber 14. The rear nozzle 12 presses the front nozzle 11 against the hydraulic spray gun 9 to fix it. The contact surface between the front nozzle 11 and the rear nozzle 12 is conical, so that the two nozzles have a high concentricity. The front nozzle 11 and the rear nozzle 12 are both made of high-hardness wear-resistant materials that can withstand abrasive erosion for a long time, such as hard alloy and composite ceramic materials.

[0047] In some embodiments, Figure 3 As shown, the aperture of the straight end of the front nozzle 11 is d, and the aperture of the injection hole 16 of the rear nozzle 12 is D. To ensure a better jet effect, the value of D is 1.2 to 1.8 times of d. The diameter of the suction hole 15 is b, and the gap size between the rear nozzle 12 and the spray gun body is a, and a is smaller than b. This setting can block impurity particles larger than a outside the gun body and fall off with the flushing of the water flow. The gap size a acts as a filter to prevent oversized particles from entering the suction hole 15 and being unable to be discharged, causing the suction hole 15 to be blocked.

[0048] In addition, since the casing-changing well diameter becomes smaller, in order to ensure the permeability of the pipe string, the coiled tubing 6 is generally selected to be 1.75 inches or 2 inches, and the outer diameter of the small-diameter hydraulic spray gun 9 is generally not greater than 45 mm. A return line 8 is also provided on the wellhead equipment 7, and the return line 8 is connected to the liquid recovery tank.

[0049] A repair method for a deformed casing of the present invention is carried out on the above-mentioned repair device, and the repair method is:

[0050] The first step is to arrange the liquid tank 1, the sand mixing skid 2, the stop valve 3, the high-pressure pumping equipment 4, the coiled tubing equipment 5, the coiled tubing 6, the hydraulic spray gun 9, and the wellhead equipment 7 on the ground, and wind the coiled tubing 6 around the coiled tubing equipment 5, and the coiled tubing 6 passes through the wellhead equipment 7 and extends into the wellbore; then, the coiled tubing 6 and the hydraulic spray gun 9 connected to the end thereof are lowered to the position of the casing deformation point; then, the perforating operation can be started.

[0051] The second step is to perform perforation operations on the casing change point, perforating the casing to form a cavity between the casing and the cement and rock behind it, which is used to release the squeezing force of the formation at the casing change point on the casing.

[0052] During the perforation operation, the first stage is the surface sanding perforation operation. The stop valve 3 is closed and a resistance-reducing liquid containing abrasive is used. The sand mixing skid 2 extracts the resistance-reducing liquid from the liquid tank 1 and mixes a certain proportion of abrasives to form a uniformly mixed abrasive suspension; the high-pressure pumping device 4 converts the abrasive suspension into a high-pressure abrasive suspension and sends it to the high-pressure inlet of the continuous tubing device 5. The high-pressure abrasive suspension is transported to the small-diameter hydraulic spray gun 9 through the continuous tubing 6. The small-diameter hydraulic spray gun 9 is lowered to the deformation point of the casing. The high-pressure abrasive suspension forms a high-speed abrasive jet after passing through the small-diameter hydraulic spray gun 9. The high-speed abrasive jet contacts the casing. Due to the small contact area, it can generate extremely high contact shear stress. When it is greater than the contact shear stress of the material, the material is destroyed, causing the contact area to break into particles and fall off from the matrix. The fallen particles and abrasives flow laterally under the water jet. The continuous impact of the abrasive jet reaches a state of shearing and abrasion, thereby achieving perforation and cutting. The cut particles and abrasives are recirculated through the reflow zone (see Figure 4 ) Move with the water flow. The second stage is the self-priming perforating operation. After the surface sanding perforating operation is carried out for ~ minutes, it is switched to the self-priming perforating operation, that is, the sand mixing skid 2 of the surface equipment stops adding new abrasives, and the stop valve 3 is opened at the same time. The high-pressure pumping equipment 4 directly extracts the drag-reducing liquid without abrasives from the liquid tank 1 and transports it to the continuous oil pipe 6. The abrasives in the downhole casing are circulated and sucked / ejected to complete the subsequent perforating operation.

[0053] Among them, during the self-priming perforating operation, the working principle of the self-priming jet is as follows: Figure 4As shown in . When the high-pressure drag-reducing liquid is accelerated and ejected at high speed through the flow channel 13 of the front nozzle 11, the high-speed flowing jet passes through the mixing chamber 14 with an enlarged space, and a negative pressure is formed around the center of the jet, forming a pressure difference with the outside. Under the action of the pressure difference, the abrasive particles in the outside are sucked into the mixing chamber 14 through the suction hole 15 along with the fluid, mixed in the mixing chamber 14, accelerated by the main jet, and further accelerated by the rear nozzle 12 to form an abrasive jet, which is ejected from the injection hole 16 of the rear nozzle 12. The high-speed abrasive jet contacts the casing or rock. Due to the small contact area, it can generate extremely high contact shear stress. When the contact shear stress is greater than the material, the material is destroyed, causing the contact area to break into particles and fall off from the matrix. The fallen particles and abrasive flow laterally under the water jet. The continuous impact of the abrasive jet reaches a state of shearing and abrasion, thereby achieving cutting. The cut particles and abrasives pass through the reflow zone, with a portion being sucked into the mixing chamber 14 through the suction port, and a portion being in the eddy flow zone.

[0054] Finally, under the action of continuous high-speed jet, due to the difference in the properties of casing, cement and rock materials, the high-speed abrasive jet will form a vortex zone behind the casing. With the high-speed scouring of the abrasive in the vortex zone, the cement and rock are gradually broken to form a jet cavity area. The outer wall of the casing no longer bears the squeezing force of the formation, and the ground stress at the deformation point of the casing is eliminated, which meets the conditions for casing shaping operations.

[0055] The third step is to perform casing shaping and patching operations. After stopping perforating, the small-diameter hydraulic spray gun 9 is pulled out of the wellhead, and the inner diameter of the casing is expanded through casing shaping operations to restore the casing diameter. After the casing shaping operation, the casing patching operation is to be carried out, and an expansion pipe or a smaller diameter casing is inserted and fixed at the casing change position, the purpose of which is to close the damage at the casing deformation and the holes left by perforation, and restore the wellbore barrier.

[0056] like Figure 5 The schematic diagram of the operation method is shown in FIG. 1 . Before repair, the deformation point of the casing is squeezed by the ground stress from both sides. During the perforation operation, a small-diameter hydraulic spray gun 9 is lowered to the deformation point to penetrate and form a perforation cavity, eliminating the squeezing effect of the ground stress on both sides. Then the casing shaper is lowered here to restore the inner diameter of the casing. Finally, a small-diameter casing fixing patch is lowered to complete the repair process.

[0057] In the embodiment of the present invention, a continuous tubing 6 is used for operation, and the diameter of the continuous tubing 6 can be adjusted according to the degree of casing deformation. The continuous tubing 6 operation is suitable for oil, gas and water wells, and is particularly suitable for some highly deviated wells and horizontal wells. It has a wide range of applications, strong passability, good controllability, fast movement and low cost.

[0058] In the embodiment of the present invention, a self-priming nozzle is used, which greatly reduces the amount of abrasive. High-pressure abrasive suspension will cause wear to the coiled tubing 6, ground equipment and pipelines, reduce pipeline wall thickness, shorten equipment life, and have high operating risks. The amount of abrasive used in the embodiment of the present invention is extremely low, the operation is highly safe, and the operating cost is low.

[0059] In the embodiment of the present invention, a small-diameter hydraulic spray gun 9 is creatively used to perform perforation operations first, thereby eliminating the squeezing force of the formation on the casing, greatly reducing the expansion force required for casing shaping, and solving the problem of repairing deformed casing under high confining pressure and high ground stress conditions.

[0060] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for repairing a deformed casing, characterized in that: include: Perform perforation operations on the casing change point, perforate the casing to form a cavity between the casing and the cement and rock behind it, so as to release the squeezing force of the formation at the casing change point on the casing; Casing shaping and patching operations.

2. A method for repairing a deformed casing according to claim 1, characterized in that: When perforating the casing change point of the casing, firstly, a uniformly mixed abrasive suspension is used for perforating, and then a friction reducing fluid without abrasive is used for circulating self-priming perforating; The uniformly mixed abrasive suspension is a mixture of a drag reducing liquid and an abrasive.

3. A method for repairing a deformed casing according to claim 2, characterized in that: The circulating self-priming perforating operation includes: mixing low-velocity crushed debris formed under the action of water pressure and abrasive with high-velocity drag-reducing fluid, accelerating the mixture and spraying it onto the casing.

4. A method for repairing a deformed casing according to claim 3, characterized in that: The cavity is a concave ellipsoidal structure.

5. A method for repairing a deformed casing according to claim 4, characterized in that: The casing shaping is to expand the deformation points of the casing to restore the casing diameter; The patching operation is to close the casing holes and reinforce them.

6. A repairing device for implementing the method for repairing a deformed casing according to any one of claims 1 to 5, characterized in that: It includes a liquid tank, a sand mixing skid, a high-pressure pumping device, a coiled tubing device, a hydraulic spray gun, and a wellhead device. The input pipeline of the sand mixing skid is connected to the liquid tank. A stop valve is provided between the liquid tank and the high-pressure pumping device. The input end of the high-pressure pumping device is connected to the output pipeline of the sand mixing skid. A coiled tubing is wound around the coiled tubing device. The high-pressure inlet of the coiled tubing device is connected to the coiled tubing. The hydraulic spray gun is connected to the end of the coiled tubing. The hydraulic spray gun and the coiled tubing pass through the wellhead device and extend into the wellbore.

7. A repair device according to claim 6, characterized in that: A self-priming nozzle is fixedly provided on the hydraulic spray gun, and the self-priming nozzle includes a front nozzle and a rear nozzle, the front nozzle is sleeved in the rear nozzle, a flow channel is provided inside the front nozzle, a mixing chamber is provided inside the rear nozzle, an injection hole is provided at the end of the rear nozzle, and a suction hole is also provided in the rear nozzle, the suction hole is located on the side of the mixing chamber, the flow channel is connected with the mixing chamber, and the injection hole and the suction hole are both connected with the mixing chamber.

8. A repair device according to claim 7, characterized in that: The flow channel is a tapered straight flow channel, the end of the flow channel close to the mixing chamber is a straight end, and the end away from the mixing chamber is a tapered end. The suction hole is arranged at an angle with the mixing chamber, and a return pipeline is connected to the wellhead equipment.

9. A repair device according to claim 8, characterized in that: The aperture of the straight end of the front nozzle is d, and the aperture of the injection hole of the rear nozzle is D, and the value of D is 1.2 to 1.8 times the value of d.

10. A repair device according to claim 8, characterized in that: The diameter of the suction hole is b, and the gap size between the rear nozzle and the hydraulic spray gun is a, and the value of a is smaller than the value of b.

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