Well wall strengthening tool and method for strengthening well wall

Abstract

The invention provides a well wall strengthening tool which comprises a drill column and a well wall strengthening mechanism, the drill column comprises a first connector, a second connector arranged on the downstream portion of the first connector and a sleeve arranged between the first connector and the second connector, and the sleeve is provided with a through hole. The sleeve is sleeved with the reel pipe, the expansion cavity is arranged between the sleeve and the reel pipe and communicated with the through hole, and the expansion cavity can be expanded after receiving drilling fluid from the sleeve through the through hole. Therefore, the reel pipe is promoted to move outwards in the radial direction to be connected with the well wall in a sealed mode. According to the invention, the action of each part is relatively independent, the requirement of integral sealing is obviously reduced compared with the prior art, and complex stratum plugging can be realized for many times under the condition that the diameter of a well hole is not lost.

Description

Technical Field

[0001] The present invention relates to the technical field of complex wellbore processing, and in particular to a wellbore strengthening tool and a wellbore strengthening method. Background Art

[0002] At present, during the drilling process, after the drill bit breaks the formation rock, it destroys the stress state of the formation, and drilling complex situations such as wellbore instability or drilling fluid leakage when encountering fractured formations often occur. To deal with well leakage and wellbore instability, the method of adjusting the drilling fluid performance is usually adopted first. If the wellbore instability or leakage still exists after adjusting the drilling fluid performance and replacing the drilling fluid system, casing is usually installed for isolation. However, most of the wellbore diameter needs to be sacrificed after casing isolation, and the next drilling can only be carried out with a small drill bit.

[0003] In the process of ultra-deep well drilling, the drilling encounters are complex, and casing isolation of complex formations will increase the number of wellbore structures and reduce the size of the completed wellbore, affecting the transformation of oil and gas layers and production efficiency. At present, in view of the stability of the drilling wellbore and the complexity of well leakage, the expansion bellows technology and solid expansion tube technology used to isolate complex formations with temporary rigid wellbore can alleviate the impact of wellbore collapse and leakage on safe drilling.

[0004] Expansion bellows technology: The circular section of the metal round tube is cold pressed into a special-shaped section to reduce the outer diameter of the round tube and make the section corrugated. The bellows is then sent to the complex well section to be plugged with a drill pipe. The bellows is restored to a circular tube by pressure in the drill string and in contact with the formation to plug the complex formation. The difficulty of this technology lies in the need to maintain sufficient sealing performance during the process of restoring the circular shape, and both ends of the metal tube are small-diameter columnar structures. After the bellows is expanded, a separate expansion tool and grinding shoe are required to perform mechanical expansion and milling operations, and the operation cycle takes at least one week for each expansion construction.

[0005] Solid expansion pipe technology: Use metal pipes to temporarily isolate complex formations. The pipe used is circular before entering the well. After entering the well, the expansion cone inside the launch chamber at the bottom of the pipe string is driven upward by pressure in the drill string, and then the diameter of the circular pipe is further expanded underground to fit the well wall to achieve complex formation plugging. Solid expansion pipe technology usually requires cementing operations. In the early development of technology, the expansion pipe usually needs to be suspended in the upper casing shoe before it can expand. At present, the solid expansion pipe technology for open holes has been developed.

[0006] However, both of the above-mentioned temporary rigid wellbore strengthening methods require maintaining a relatively high pressure inside the drill string and pipe string, and also have the disadvantages of high expansion deformation pressure, multiple construction procedures and long operation cycle.

[0007] Therefore, it is desired in the art to provide a well wall strengthening tool to solve the above technical problems. Summary of the invention

[0008] The purpose of the present invention is to provide a well wall strengthening tool, in which each part acts relatively independently, the overall sealing requirement is significantly reduced compared with the prior art, and complex formation plugging can be achieved multiple times without losing the wellbore diameter.

[0009] According to a first aspect of the present invention, a well wall strengthening tool is provided, comprising a drill string, which comprises a first joint, a second joint arranged downstream of the first joint, and a sleeve arranged between the first joint and the second joint, wherein a through hole is provided on the sleeve, and

[0010] The well wall strengthening mechanism comprises a coiled tube sleeved outside the sleeve, and an expansion chamber arranged between the sleeve and the coiled tube and connected to the through hole.

[0011] The expansion chamber is configured to expand after receiving drilling fluid from the sleeve through the through hole, thereby causing the coiled tubing to move radially outward to form a sealed connection with the well wall.

[0012] In one embodiment, a hollow metal ring is further provided at the joint between the first joint and the sleeve, so as to allow the drilling fluid from the through hole to flow only to the expansion chamber.

[0013] In one embodiment, the inner hollow metal ring forms a threaded connection with the first joint.

[0014] In one embodiment, the expansion chamber is made of rubber material, and the top end of the expansion chamber is vulcanized on the inner hollow metal ring.

[0015] In one embodiment, a first step extending radially inward is formed at a junction between the second joint and the sleeve, and the roller tube is axially in contact with the first step in an initial state.

[0016] In one embodiment, the rolling tube is rolled from a metal sheet and includes a first side end and a second side end, wherein a locking portion extending radially inward is provided on the first side end, and a clamping portion for extending through the locking portion is formed on the second side end.

[0017] In one embodiment, a plurality of spaced first wedge-shaped teeth extending radially outward and obliquely downward are provided on the outer wall surface of the engaging portion, and a plurality of spaced second wedge-shaped teeth for forming a snap connection with the first wedge-shaped teeth are provided on the inner wall surface of the locking portion.

[0018] In one embodiment, the well wall strengthening tool further comprises a ball seat fixed in the sleeve by a pin, the through hole is radially arranged on the sleeve, and in an initial state, the through hole is axially within the range of the ball seat.

[0019] The pin is sheared by pressing with a ball, thereby causing the ball seat to move downstream to open the through hole.

[0020] In one embodiment, a second step extending radially outward and used for axially abutting against the ball seat is formed on the inner wall of the second joint.

[0021] According to a second aspect of the present invention, there is provided a method for strengthening a wellbore using the wellbore strengthening tool as described above, comprising the following steps:

[0022] S1, after lowering the well wall strengthening tool to a predetermined position, shearing off the pin by throwing a ball to press it, thereby causing the ball seat to move downstream to open the through hole;

[0023] S2, the expansion chamber expands after receiving the drilling fluid from the sleeve through the through hole, thereby causing the coiled tube to move radially outward, and the coiled tube is locked by the engaging portion and the locking portion so as to form a sealed connection between the coiled tube and the well wall;

[0024] S3, lifting and removing the drill string and the expansion cavity.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] First, the coiled tube in the present invention can expand radially outward under the action of the expansion chamber until the coiled tube is attached to the well wall and forms a sealed connection, and the locking part and the clamping part are locked to limit the deformation of the coiled tube. In this way, the purpose of temporary isolation of the well wall in complex formations is achieved. Compared with the existing technology, this method has the advantages of simple structure, fewer expansion processes and low construction requirements.

[0027] Secondly, since the present invention can lock the deformation of the coiled tube only by gradually withdrawing the engaging portion from the locking portion, compared with the sealing technology in the prior art, the present invention only needs to maintain a lower hydraulic pressure to achieve the effect of expanding the coiled tube, thereby significantly reducing various requirements during the construction process.

[0028] Third, the top of the expansion cavity in the present invention can be vulcanized on the inner hollow metal ring. As a result, the drilling fluid flowing out through the through hole under the action of the inner hollow metal ring can only enter the expansion cavity, thereby strengthening the flow capacity of the through hole, the inner hollow metal ring and the expansion cavity as a flow channel for the drilling fluid to improve the efficiency and speed of the well wall strengthening work. In addition, since the expansion cavity can be hung on the inner hollow metal ring as a whole in a vulcanized manner, it is helpful to carry out the subsequent lifting work after the well wall strengthening work is completed.

[0029] Fourthly, each part of the present invention functions relatively independently, and the demand for overall sealing is significantly reduced compared with the prior art, and complex formation plugging can be achieved multiple times without losing the wellbore diameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described in detail below in conjunction with the accompanying drawings, in which:

[0031] Figure 1 The structure of the well wall strengthening tool according to the present invention is schematically shown;

[0032] Figure 2 for Figure 1 A partial enlarged view of the middle A;

[0033] Figure 3 A schematic diagram schematically shows a well wall strengthening tool according to the present invention in a working state;

[0034] Figure 4 A schematic diagram of a drum in a well wall strengthening tool according to the present invention in a first state;

[0035] Figure 5 FIG. 1 is a schematic diagram showing that the drum in the wellbore strengthening tool according to the present invention is in a second state.

[0036] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0037] In order to make the technical solutions and advantages of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0038] The directional terms "upstream" or "above" or similar terms refer to the direction closer to the wellhead, i.e. Figure 1 The directional terms "downstream" or "below" or similar terms refer to the direction away from the wellhead, i.e. Figure 1 The bottom direction in .

[0039] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0040] In the present invention, unless otherwise clearly stipulated and limited, terms such as "installed", "connected", "connected", "fixed" and the like 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, or it can be the internal connection of two elements.

[0041] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] The present invention will be further described below in conjunction with the accompanying drawings.

[0043] Figure 1 The structure of a well wall strengthening tool 100 according to the present invention is schematically shown;

[0044] Figure 2 for Figure 1 A partial enlarged view of the middle A;

[0045] Figure 3 A schematic diagram schematically shows a well wall strengthening tool 100 according to the present invention in a working state;

[0046] Figure 4 is a schematic diagram of the drum 20 in the well wall strengthening tool 100 according to the present invention in a first state;

[0047] Figure 5 FIG. 2 is a schematic diagram showing that the drum 20 in the wellbore strengthening tool 100 according to the present invention is in a second state.

[0048] like Figure 1 As shown, according to a first aspect of the present invention, a well wall strengthening tool 100 is provided, which includes a drill string. The drill string includes a first joint 11, a second joint 12 and a sleeve 13.

[0049] Preferably, the first joint 11 is arranged at the upper part, and a drill pipe buckle (not shown) is provided at the top end of the first joint 11 for connecting to an upper drill string (not shown).

[0050] Preferably, the second joint 12 is arranged at the lower part, in other words, the second joint 12 is arranged downstream of the first joint 11, and a drill rod buckle (not shown) is provided at the bottom end of the second joint 12 for connecting a guide shoe (not shown) or a drill bit (not shown).

[0051] Preferably, the sleeve 13 is arranged between the first joint 11 and the second joint 12. It is easy to understand that the sleeve 13 in the present invention is composed of a first sleeve part 132 and a second sleeve part 133, wherein the first sleeve part 132 is fixedly connected to the lower end surface of the first joint 11, the second sleeve part 133 is fixedly connected to the upper end surface of the second joint 12, and the first sleeve part 132 and the second sleeve part 133 are connected by a thread.

[0052] In one embodiment, Figure 2 As shown, a through hole 131 is provided on the sleeve 13. Preferably, in the open state, the drilling fluid from the sleeve 13 can flow to the outside through the through hole 131.

[0053] According to the present invention, Figure 2 As shown, the well wall strengthening tool 100 further includes a ball seat 40 fixed in the sleeve 13 by a pin 401. Preferably, the outer peripheral surface of the ball seat 40 is connected to the inner peripheral surface of the sleeve 13 in a sealing manner.

[0054] In a preferred embodiment, the through hole 131 is radially arranged on the sleeve 13, and in the initial state, the through hole 131 is axially within the range of the ball seat 40. It is easy to understand that during the lowering of the well wall strengthening tool 100, the through hole 131 can always be in a closed state under the action of the ball seat 40, thereby ensuring that the through hole 131 can be opened only after the well wall strengthening tool 100 is lowered to a predetermined position, so as to improve the success rate of well wall strengthening.

[0055] It is easy to understand that when the well wall strengthening tool 100 is lowered to a predetermined position, the pin 401 can be sheared by pressing with a ball, thereby causing the ball seat 40 to move downstream to open the through hole 131, thereby facilitating subsequent well wall strengthening work.

[0056] According to the present invention, the well wall strengthening tool 100 also includes a well wall strengthening mechanism. Figure 1 As shown, the well wall strengthening mechanism includes a coiled tube 20 and an expansion chamber 30 .

[0057] Preferably, the coiled tube 20 is sleeved outside the casing 13 ; and the expansion chamber 30 is provided between the casing 13 and the coiled tube 20 , and the expansion chamber 30 can be communicated with the sleeve 13 through the through hole 131 to receive the drilling fluid.

[0058] In one embodiment, Figure 1 and 3As shown, a second step 122 extending radially outward is formed on the inner wall of the second joint 12. Preferably, when the pin 401 is cut off and the ball seat 40 moves downward, the second step 122 can receive and form an axial abutment with the ball seat 40, thereby limiting the axial position of the ball seat 40.

[0059] It is easy to understand that when the ball seat 40 is axially abutted against the second step 122, the outer circumferential surface of the ball seat 40 forms a sealed connection with the inner circumferential surface of the second joint 12, thereby forming a closed environment inside the drill string to ensure that the drilling fluid in the sleeve 13 can smoothly pass through the through hole 131 and flow to the external expansion chamber 30.

[0060] After opening the through hole 131, the drilling fluid in the sleeve 13 can flow into the expansion chamber 30 through the through hole 131. As the total volume of the flowing drilling fluid increases, the expansion chamber 30 will gradually expand and push the coiled tube 20 to move radially outward until a sealed connection is formed between the coiled tube 20 and the well wall, thereby completing the well wall reinforcement work.

[0061] In one embodiment, Figure 2 As shown, an inner hollow metal ring 111 is further provided at the joint of the first joint 11 and the sleeve 13. It is easy to understand that the inner hollow metal ring 111 can be used as a transmission medium for drilling fluid, so that the through hole 131 can be connected with the expansion chamber 30 to ensure that the drilling fluid flowing out through the through hole 131 can only flow to the expansion chamber 30, thereby ensuring that the expansion chamber 30 can be smoothly expanded, further improving the success rate of the well wall strengthening work.

[0062] In a preferred embodiment, the inner hollow metal ring 111 is threadedly connected to the first joint 11. In other words, the inner hollow metal ring 111 is connected to the first joint 11 via fine threads, thereby improving the stability of the inner hollow metal ring 111 during well wall strengthening operations.

[0063] After opening the through hole 131, the drilling fluid in the sleeve 13 can flow into the expansion chamber 30 through the through hole 131 and the inner hollow metal ring 111 in turn, thereby ensuring that the drilling fluid flowing out through the through hole 131 can only flow to the expansion chamber 30, so as to achieve the purpose of completing the well wall strengthening work and improving the success rate of well wall strengthening.

[0064] In one embodiment, the expansion chamber 30 is made of rubber material, and the top of the expansion chamber 30 is vulcanized on the inner hollow metal ring 111. Thus, the expansion chamber 30 is only connected to the inner hollow metal ring 111, and can smoothly receive the drilling fluid from the inner hollow metal ring 111, so as to improve the success rate of strengthening the well wall.

[0065] In this way, on the one hand, the flow capacity of the through hole 131, the inner hollow metal ring 111 and the expansion chamber 30, which is the flow channel for the drilling fluid, is enhanced, thereby improving the efficiency and speed of the well wall strengthening work; on the other hand, the vulcanization method is used to enable the expansion chamber 30 to be suspended as a whole on the inner hollow metal ring 111, which is helpful for the subsequent lifting work after the well wall strengthening work is completed.

[0066] In one embodiment, Figure 1 and 3 As shown, a first step 121 extending radially inward is formed at the joint of the second joint 12 and the sleeve 13. Preferably, the roller tube 20 can axially abut against the first step 121 in the initial state.

[0067] In addition, since the inner diameter of the coiled tube 20 in the initial state is smaller than or equal to the outer diameters of the first joint 11 and the second joint 12, the coiled tube 20 can be restrained at a fixed position outside the sleeve 13 under the joint action of the first joint 11 and the second joint 12 during the lowering process, thereby ensuring that the well wall strengthening tool 100 can be smoothly lowered to the predetermined position in the well.

[0068] In a specific embodiment, the coiled tube 20 is rolled from a metal sheet, which effectively improves the stability of the overall structure of the coiled tube 20, so that the coiled tube 20 can smoothly expand radially outward under the action of the expansion chamber 30, thereby forming a sealed connection with the well wall, so as to achieve the purpose of strengthening the well wall.

[0069] In one embodiment, Figure 4 and 5 As shown, the roller tube 20 includes a first side end 21 (end face) and a second side end 22 (end face). Preferably, a locking portion 211 extending radially inward is provided on the first side end 21, and a clamping portion 221 for extending through the locking portion 211 is formed on the second side end 22. It is easy to understand that the locking portion 211 and the clamping portion 221 can achieve the effect of locking and preventing retreat after cooperation.

[0070] It is easy to understand that after the expansion chamber 30 receives the drilling fluid and expands, the coiled tube 20 expands radially outward under the action of the expansion chamber 30, and the engaging portion 221 gradually withdraws from the locking portion 211. When the coiled tube 20 is attached to the well wall and forms a sealed connection, the locking portion 211 and the engaging portion 221 are locked to limit the deformation of the coiled tube 20.

[0071] In a specific embodiment, Figure 4 and 5As shown, a plurality of first wedge-shaped teeth 222 extending radially outward and obliquely downward are provided on the outer wall surface of the engaging portion 221, and a plurality of second wedge-shaped teeth 212 extending radially outward and obliquely upward are provided on the inner wall surface of the locking portion 211. It is easy to understand that the first wedge-shaped teeth 222 and the second wedge-shaped teeth 212 are always in a state of engagement, so that the rolling tube 20 can be locked and prevented from retreating.

[0072] Compared with the prior art, the present invention expands the drilling fluid received by the expansion chamber 30, thereby causing the coiled tube 20 to expand radially outward. In addition, during the expansion of the coiled tube 20, the first wedge-shaped teeth 222 on the engaging portion 221 and the second wedge-shaped teeth 212 on the locking portion 211 play a role of locking and preventing retreat, so as to ensure that the coiled tube 20 can accurately fit the well wall, thereby improving the ability of strengthening the well wall.

[0073] In other words, the present invention essentially achieves the purpose of accurately fitting the coiled tube 20 to the well wall by changing the position of the engaging portion 221 on the locking portion 211. Therefore, compared with the prior art, the present invention has the advantages of simple structure, fewer expansion processes and lower construction requirements.

[0074] Part of the assembly work of the wellbore strengthening tool 100: First, the top of the expansion chamber 30 needs to be vulcanized on the inner hollow metal ring 111 to ensure that the inner hollow metal ring 111 and the expansion chamber 30 have the ability to allow drilling fluid to flow; then, the inner hollow metal ring 111 is installed on the first sleeve portion 132 of the first joint 11 through fine threads to ensure the stability of the inner hollow metal ring 111 when working underground; finally, the coiled tube 20 is installed into the sleeve 13 from bottom to top, and then the second joint 12 is connected to ensure that the axial position of the coiled tube 20 is relatively fixed and cannot move under the action of the first joint 11 and the second joint 12.

[0075] Preferably, the outer diameter of the coiled tubing 20 before and after deformation needs to be determined according to the drill string size and the wellbore size.

[0076] According to a second aspect of the present invention, there is provided a method for strengthening a wellbore using the wellbore strengthening tool as described above, comprising the following steps:

[0077] First, the assembled well wall strengthening tool 100 is lowered to a predetermined position;

[0078] Then, the pin 401 is sheared by the ball pitching, thereby forcing the ball seat 40 to move downstream to open the through hole 131. Thereafter, the ball seat 40 will move downward until it forms an axial abutment with the second step 122.

[0079] Afterwards, the drilling fluid from the sleeve 13 flows into the expansion chamber 30 through the through hole 131 and the inner hollow metal ring 111 in sequence under the action of pressure.

[0080] Afterwards, as the drilling fluid gradually increases, the expansion chamber 30 expands under the action of the drilling fluid and pushes the coiled tube 20 to expand radially outward until the coiled tube 20 adheres to the well wall and forms a sealed connection, thereby locking the coiled tube 20 through the engaging portion 221 and the locking portion 211 to shape it.

[0081] Specifically, during the expansion of the coiled tube 20, the engaging portion 221 will gradually withdraw from the locking portion 211 until the coiled tube 20 is in contact with the well wall and forms a sealed connection. The first wedge-shaped teeth 222 on the engaging portion 221 are locked with the second wedge-shaped teeth 212 on the locking portion 211 to ensure that the coiled tube 20 can be accurately fitted with the well wall, thereby improving the ability to strengthen the well wall.

[0082] It is easy to understand that, since the first wedge-shaped teeth 222 and the second wedge-shaped teeth 212 can always mesh with each other, the locking portion 211 can effectively prevent the engaging portion 221 from retreating during the expansion of the rolling tube 20 .

[0083] Finally, the drill string and the expansion chamber 30 are lifted up and removed.

[0084] In a preferred embodiment, the above steps can be repeated to achieve multiple wellbore reinforcement work on complex formations to ensure safe drilling of complex formations.

[0085] Compared with the prior art, the present invention has the following advantages:

[0086] First, the coiled tube 20 of the present invention can expand radially outward under the action of the expansion chamber 30 until the coiled tube 20 is attached to the well wall and forms a sealed connection, and the locking portion 211 and the engaging portion 221 are locked to limit the deformation of the coiled tube 20. In this way, the purpose of temporary isolation of the well wall in complex formations is achieved. Compared with the prior art, this method has the advantages of simple structure, fewer expansion processes and low construction requirements.

[0087] Secondly, since the present invention can lock the deformation of the coiled tube 20 only by gradually withdrawing the engaging portion 221 from the locking portion 211, compared with the sealing technology in the prior art, the present invention only needs to maintain a lower hydraulic pressure to achieve the effect of expanding the coiled tube 20, thereby significantly reducing various requirements during the construction process.

[0088] Third, the top of the expansion chamber 30 in the present invention can be vulcanized on the inner hollow metal ring 111. As a result, the drilling fluid flowing out through the through hole 131 under the action of the inner hollow metal ring 111 can only enter the expansion chamber 30, thereby strengthening the flow capacity of the through hole 131, the inner hollow metal ring 111 and the expansion chamber 30, which is the flow channel for the drilling fluid, to improve the efficiency and speed of the well wall strengthening work. In addition, since the expansion chamber 300 can be hung on the inner hollow metal ring 111 as a whole in a vulcanized manner, it is helpful to carry out the subsequent lifting work after the well wall strengthening work is completed.

[0089] Fourthly, each part of the present invention functions relatively independently, and the demand for overall sealing is significantly reduced compared with the prior art, and complex formation plugging can be achieved multiple times without losing the wellbore diameter.

[0090] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art can easily make changes or modifications within the disclosure scope of the present invention, and such changes or modifications should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A well wall strengthening tool, comprising: A drill string, comprising a first joint (11), a second joint (12) arranged downstream of the first joint (11), and a sleeve (13) arranged between the first joint (11) and the second joint (12), wherein a through hole (131) is provided on the sleeve (13), and A well wall strengthening mechanism comprises a coiled tube (20) sleeved outside the sleeve (13), and an expansion chamber (30) arranged between the sleeve (13) and the coiled tube (20) and communicating with the through hole (131). The expansion chamber (30) is configured to expand after receiving drilling fluid from the sleeve (13) through the through hole (131), thereby causing the coiled tubing (20) to move radially outward to form a sealed connection with the well wall.

2. The well wall strengthening tool according to claim 1, characterized in that: An inner hollow metal ring (111) is also provided at the joint between the first joint (11) and the sleeve (13), thereby allowing the drilling fluid from the through hole (131) to flow only toward the expansion chamber (30).

3. The well wall strengthening tool according to claim 2, characterized in that: The inner hollow metal ring (111) is threadedly connected to the first joint (11).

4. The well wall strengthening tool according to claim 3, characterized in that: The expansion chamber (30) is made of rubber material, and the top end of the expansion chamber (30) is vulcanized on the inner hollow metal ring (111).

5. The well wall strengthening tool according to claim 4, characterized in that: A first step (121) extending radially inward is formed at the joint between the second joint (12) and the sleeve (13), and the rolling tube (20) is axially in contact with the first step (121) in an initial state.

6. The well wall strengthening tool according to claim 5, characterized in that: The rolling tube (20) is rolled from a metal sheet and comprises a first side end (21) and a second side end (22), wherein a locking portion (211) extending radially inward is provided on the first side end (21), and a snap-fit ​​portion (221) for extending through the locking portion (211) is formed on the second side end (22).

7. The well wall strengthening tool according to claim 6, characterized in that: A plurality of first wedge-shaped teeth (222) are provided on the outer wall surface of the engaging portion (221) and are spaced apart and extend radially outward and obliquely downward, and a plurality of second wedge-shaped teeth (212) are provided on the inner wall surface of the locking portion (211) and are used to form a snap connection with the first wedge-shaped teeth (222).

8. The well wall strengthening tool according to any one of claims 1 to 7, characterized in that: The well wall strengthening tool further comprises a ball seat (40) fixed in the sleeve (13) by a pin (401), the through hole (131) is radially arranged on the sleeve (13), and in an initial state, the through hole (131) is axially within the range of the ball seat (40), The pin (401) is sheared by hitting it with a ball, thereby causing the ball seat (40) to move downstream to open the through hole (131).

9. The well wall strengthening tool according to claim 8, characterized in that: A second step (122) is formed on the inner wall of the second joint (12) and extends radially outward and is used for axially abutting against the ball seat (40).

10. A method for strengthening a wellbore using the wellbore strengthening tool according to any one of claims 1 to 9, comprising the following steps: S1, after lowering the well wall strengthening tool to a predetermined position, the pin (401) is sheared off by throwing a ball to press it, thereby causing the ball seat (40) to move downstream to open the through hole (131); S2, the expansion chamber (30) expands after receiving the drilling fluid from the sleeve (13) through the through hole (131), thereby causing the coiled tube (20) to move radially outward, and the coiled tube (20) is locked with the locking portion (211) through the engaging portion (221) so as to form a sealed connection with the well wall; S3, lifting and removing the drill string and the expansion chamber (30).

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