A downhole high-strength smooth falling object fishing device and fishing method

Abstract

The application provides a downhole high-strength smooth falling object fishing device and fishing method, wherein the fishing device comprises an extrusion clamping section and a thread forming section; the extrusion clamping section is provided with a clamping cavity, and the clamped section of the falling object can enter the extrusion clamping section along the clamping cavity; the extrusion clamping section can deform along the radial direction after being subjected to axial pressure to clamp the clamped section in the clamping cavity; the thread forming section is arranged at the upper end of the extrusion clamping section, the thread forming section is provided with a central hole, the central hole is communicated with the clamping cavity, and the inner wall of the thread forming section is provided with a thread forming part near one end of the clamping cavity; the thread forming part can form a thread on the clamped section entering the clamping cavity. The application adopts thread forming and uses the downward pressure generated by the drilling pressure to superimpose and transmit to the extrusion clamping section of the fishing device, so that the extrusion clamping section expands and deforms along the radial direction to clamp the falling object. The fishing lifting force provided by the combination of the two is increased from about 30 tons to 100-260 tons, and the fishing problem of the falling object below the rotary guide downhole main shaft is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of downhole object retrieval technology in oil drilling engineering, specifically to a high-strength, smooth downhole object retrieval device and method. Background Technology

[0002] As oil and gas drilling and development continue to advance into low-permeability, deep, and unconventional areas, the technical difficulty of horizontal wells is constantly increasing, and rotary steerable drilling, with its significant advantages such as speed and efficiency, has been increasingly widely used.

[0003] Rotary steering systems integrate mechanical, hydraulic, and electrical control systems, and are characterized by numerous components and complex structures. To ensure tool strength, a large amount of high-strength alloy materials are used. However, rotary steering systems operate in harsh environments such as strong downhole vibration and high loads for extended periods. Especially when encountering complex situations such as stuck drill bits downhole, their mechanical structural strength remains relatively weak in several areas under the influence of heavy tension, compression, torsion, and shock.

[0004] According to statistics in recent years, dozens of accidents involving the fracture and fall into wells have occurred in the Sichuan-Chongqing region alone. Due to the special structure and high hardness of the rotary steering components, the commonly used oilfield wellbore salvage tools at home and abroad are difficult to use effectively. The salvage time is as long as more than a month and the success rate is extremely low. At the same time, salvage failure often results in well filling and side-drilling, causing huge economic losses.

[0005] Specifically, for rotary guide spindle components, existing salvage tools mainly take the following forms:

[0006] (1) Mother cone type retrieval tool: The principle of this tool is that after the mother cone is fitted around one end of the tubular object, appropriate drilling pressure is applied and the drill string is rotated, forcing the retrieval thread to squeeze into the outer wall of the object to create a snap. When the snap can withstand a certain amount of tension and torque, the object can be retrieved in whole or in part by lifting or reverse snapping. However, the main shaft component of the rotary guide is made of high-strength alloy material, and its upper end has only about 5mm of slightly lower strength material, which can only create 2 to 3 snaps and can provide a pulling force of about 30T, which is not enough to provide sufficient pulling force to retrieve the stuck object from the well.

[0007] (2) Retrieval claw tools: Also known as one-grab retrieval tools, these tools consist of a fixed cylindrical structure and a retrieval claw structure containing multiple hooks. Their working principle is to grab the fallen object and then lock it in place through pressure or rotation, thereby retrieving the object from the well. They are mainly suitable for objects that are relatively small or have a stepped structure, and can provide relatively low pulling force. In contrast, rotary guide shaft structures lack effective gripping positions for the retrieval claws, are heavy, and are often accompanied by rock debris and foreign objects causing obstruction, making the success rate of retrieval claw tools almost zero.

[0008] (3) Slip-type fishing tools: This type of tool mainly uses the slip structure inside the cylinder to bite the outer wall of the fallen fish to achieve fishing. Since the part of the main shaft that can be used for fishing under the rotation guide is made of high-strength alloy material with only a slight concave and convex structure, the slip tool teeth cannot be effectively clamped. When clamping large tonnage fish and rotating, the slip is easy to slip and damage the slip teeth of the fishing tube, and thus cannot achieve effective fishing.

[0009] In summary, the existing fishing tools and their principles and structures are ineffective at retrieving fish that are made of high-strength alloy material with a rotary guide shaft, lack suitable stepped structures on the outer wall, and require strong retrieval force. Summary of the Invention

[0010] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to provide a high-strength, smooth-slippery object retrieval device and method for downhole operations, to effectively retrieve fallen fish made of high-strength alloy materials, such as rotary guide shafts, which require strong retrieval force.

[0011] To achieve the above objectives, the present invention provides a high-strength, smooth-felling object retrieval device for downhole applications. The retrieval device includes a squeezing and clamping section and a snap-fitting section. The squeezing and clamping section has a clamping cavity, through which the segment of the fallen fish can enter the squeezing and clamping section. The squeezing and clamping section can deform radially after being subjected to axial pressure to clamp the segment in the clamping cavity. The snap-fitting section is located at the upper end of the squeezing and clamping section and has a central hole that communicates with the clamping cavity. A snap-fitting part is provided on the inner wall of the snap-fitting section near the clamping cavity, which can snap the segment into place upon entering the clamping cavity.

[0012] Alternatively, the body of the salvage device may be made of alloy structural steel, and the buckle may be a salvage tooth, which is heat-treated and tempered to make its surface hardness greater than HRC60.

[0013] Alternatively, the inner diameter of the clamping cavity can be [missing information]. The maximum outer diameter of the clamped segment can be:

[0014] Optionally, a groove may be formed on the outer wall near the upper end of the clamped section, and a step may be formed at the lower end. The axial length of the clamping cavity may be L1, and the distance between the groove and the step on the clamped section may be L2, where L2-L1 = 1~3mm.

[0015] Optionally, an angled bevel can be formed between the inner and outer walls and the lower end face of the extrusion clamping section. The angle of the angled bevel can be 70° to 80° to facilitate the initial deformation of the extrusion clamping section under pressure.

[0016] Another aspect of the present invention provides a method for retrieving high-strength smooth objects falling into a well. The method employs the high-strength smooth object retrieval device described above. The method includes a preparatory step before retrieval, which includes measuring the size of the upper tool and determining the fracture location and the structure of the falling object, and calculating and determining the size of the retrieval device based on the size of the falling object.

[0017] Alternatively, the retrieval method may further include a lowering step of the retrieval device, which may include lowering the retrieval device to the upper part of the fallen fish, inserting the clamped section of the fallen fish into the clamping cavity, and bringing the top of the clamped section to the buckling part.

[0018] Alternatively, the retrieval method may further include a buckling and clamping step. The buckling and clamping step may include applying buckling torque to the retrieval device, completing buckling at the upper end of the clamped section through the buckling part, and then applying drilling pressure to bring the lower end of the squeezing clamping section abutting against the upper end of the step where the fish fell and continuing to apply pressure. After being compressed, the squeezing clamping section deforms and expands radially, so that its inner wall fits tightly against the outer wall of the clamped section to complete the clamping.

[0019] Optionally, the buckle length formed after the buckle-making part completes the buckle-making process can be 3-5mm, and the number of buckles can be 2-3.

[0020] Alternatively, the salvage method may further include a release and retrieval phase, which may include:

[0021] If the retrieval device and the fish become stuck in the well, a disengagement operation must be performed first before the retrieval operation can be carried out; if the retrieval device and the fish do not become stuck, the retrieval operation can be carried out directly.

[0022] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0023] This invention employs a rotary buckle system and utilizes the downward pressure generated by drilling to superimpose and transfer it to the clamping section of the retrieval device. Under the constraint of the fish-dropping step structure, the clamping section of the retrieval device expands and deforms radially, its inner wall tightly fitting the outer wall of the fish, thus achieving a secure clamping effect. Through the combined effect of these two mechanisms, the available retrieval lifting force is increased from approximately 30 tons to 100 to 260 tons, effectively solving the problem of retrieving fish from the main shaft and below under rotary guidance. Attached Figure Description

[0024] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0025] Figure 1A schematic diagram of a downhole high-strength smooth falling object retrieval device according to an exemplary embodiment 1 of the present invention is shown.

[0026] Figure 2 The diagram shows a fish retrieved by the downhole high-strength smooth falling object retrieval device according to exemplary embodiment 1 of the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-Squeezing and clamping section, 11-Clamping cavity, 12-Angled bevel, 2-Cut-out section, 21-Center hole, 22-Cut-out part, 3-Clamped section, 31-Groove, 4-Step, 5-Drill bit, 6-Rock cuttings, a-Wellbore. Detailed Implementation

[0029] In the following description, the downhole high-strength smooth falling object retrieval device and retrieval method of the present invention will be described in detail with reference to exemplary embodiments.

[0030] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Due to their unique structure and high material hardness, rotary guide components are difficult to retrieve effectively using commonly used oilfield wellbore retrieval tools both domestically and internationally. This results in problems such as retrieval time exceeding one month and extremely low success rates. Furthermore, failed retrieval attempts often lead to well filling and sidetracking, causing significant economic losses.

[0034] Based on this, the present invention provides a high-strength smooth object retrieval device and method for downhole applications. The high-strength smooth object retrieval device includes a squeezing and clamping section and a buckling section. The squeezing and clamping section has a clamping cavity, and the clamped segment of the fallen fish can enter the squeezing and clamping section along the clamping cavity. The squeezing and clamping section can deform radially after being subjected to axial pressure to clamp the clamped segment in the clamping cavity. The buckling section is located at the upper end of the squeezing and clamping section and has a central hole that communicates with the clamping cavity. A buckling part is provided on the inner wall of the buckling section near the clamping cavity, and the buckling part can buckle the clamped segment that enters the clamping cavity.

[0035] This invention employs a rotary buckle system and utilizes the downward pressure generated by drilling to superimpose and transfer it to the clamping section of the retrieval device. Under the constraint of the fish-dropping step structure, the clamping section of the retrieval device expands and deforms radially, its inner wall tightly fitting the outer wall of the fish, thus achieving a secure clamping effect. Through the combined effect of these two mechanisms, the available retrieval lifting force is increased from approximately 30 tons to 100 to 260 tons, effectively solving the problem of retrieving fish from the main shaft and below under rotary guidance.

[0036] Exemplary Example 1

[0037] This exemplary embodiment provides a downhole high-strength smooth falling object retrieval device.

[0038] Figure 1 A schematic diagram of a downhole high-strength smooth falling object retrieval device according to an exemplary embodiment 1 of the present invention is shown; Figure 2 The diagram shows a fish retrieved by the downhole high-strength smooth falling object retrieval device according to exemplary embodiment 1 of the present invention.

[0039] like Figure 1 and Figure 2 As shown in the exemplary embodiment, the downhole high-strength smooth falling object retrieval device may include a squeezing clamping section 1 and a snap-fitting section 2. The squeezing clamping section 1 and the snap-fitting section 2 can be fixedly connected by integral molding. The squeezing clamping section 1 may be located at the lower end of the snap-fitting section 2. The squeezing clamping section 1 may be a cylindrical structure with a clamping cavity 11 in the center. The snap-fitting section 2 may have a central hole 21 in the center, which can communicate with the clamping cavity 11. A snap-fitting part 22 may be provided on the inner wall surface of the snap-fitting section 2 near the clamping cavity 11. However, the present invention is not limited to this. The squeezing clamping section 1 and the snap-fitting section 2 may also be fixedly connected by welding or other methods.

[0040] Alternatively, the snap-fit ​​part 22 can be a retrieval tooth, which can snap a retrieval tooth onto the top of the fish that has fallen into the well, thereby axially fixing the retrieval device to the fish to facilitate the retrieval of the fish from the well. However, the present invention is not limited to this, and the snap-fit ​​part 22 can also be other structures that can be used for snap-fitting.

[0041] Alternatively, the surface of the buckle part 22 may be heat-treated and tempered to achieve a surface hardness greater than HRC60, in order to meet the strength required for buckle making and retrieval.

[0042] In this embodiment, the fish that has fallen into the well may include a clamping section 3. The surface of the clamping section 3 is made of a high-strength alloy material. The clamping section 3 can enter the squeezing clamping section 1 through the clamping cavity 11. The material of the squeezing clamping section 1 (i.e., the material of the retrieval device body) may be alloy structural steel. Under the action of an axial force from top to bottom, the squeezing clamping section 1 may deform radially. That is, the inner and outer walls of the squeezing clamping section 1 may expand inward and outward respectively. When the clamping section 3 of the fallen fish enters the squeezing clamping section 1, the inner wall of the squeezing clamping section 1, which is subjected to axial pressure, may fit tightly with the outer wall of the clamping section 3, thereby clamping the fallen fish in the retrieval device. However, the present invention is not limited to this. The surface material of the clamping section 3 may also be other high-strength or smooth materials, and the material of the retrieval device body may also be other materials with sufficient strength and easy to deform under force.

[0043] Optionally, the inner diameter of the clamping cavity 11 is The outer diameter of the clamped segment 3 is Should be greater than This allows the clamped segment 3 to enter the clamping cavity 11 from the lower end of the compression clamping segment 1. Preferably, and The difference between them is approximately 2 mm, which allows the clamped segment 3 to enter the clamping cavity 11 while ensuring that the inner wall of the clamping segment 1 can fit more tightly against the outer wall of the clamped segment 3 after being deformed under pressure. However, the present invention is not limited to this. and The difference between them can also be other values, as long as they can satisfy the requirement that the clamped segment 3 is allowed to enter the clamping cavity 11 while ensuring that the squeezing clamping segment 1 can clamp the clamped segment 3.

[0044] Optionally, a groove 31 may be formed on the outer wall near the upper end of the clamped segment 3, and a step 4 may be formed at the lower end. The axial length of the clamping cavity 11 (i.e., the axial length of the clamping segment 1) may be L1, and the distance between the groove 31 and the step 4 on the clamped segment 3 may be L2. L2 should be greater than L1. Preferably, the difference between L2 and L1 is 1 to 3 mm. In this way, when the clamped segment 3 enters the clamping cavity 11, the buckle-forming section at the top of the clamped segment 3 can reach the buckle-forming part 22, so that the buckle-forming operation can be carried out normally. However, the present invention is not limited to this, and the difference between L2 and L1 may also be other values, as long as it does not affect the buckle-forming.

[0045] Optionally, a beveled notch 12 can be formed at the junction of the lower end face of the compression clamping section 1 and its inner and outer walls. Preferably, the opening angle of the beveled notch 12 can be 70° to 80°. Within this angle range, the clamped section 3 can more easily enter the compression clamping section 1 along the clamping cavity 11, and the compression clamping section 1 is more likely to undergo initial deformation when subjected to axial pressure, so that the inner wall of the compression clamping section 1 fits better and more tightly with the outer wall of the clamped section 3. However, the present invention is not limited to this, and the opening angle of the beveled notch 12 can also be other values, as long as it does not affect the entry and clamping of the clamped section 3.

[0046] The working principle of the downhole high-strength smooth falling object retrieval device described in this exemplary embodiment is as follows:

[0047] When a fish falls into the well and needs to be retrieved at the bottom of wellbore a, first connect a retrieval device of appropriate size to the drill pipe above it and lower it from the wellhead along wellbore a to above the fish. Continue lowering the retrieval device so that the squeezing clamping section 1 is fitted onto the clamped section 3 of the fish, ensuring that the top of the clamped section 3 is located at the snap-fit ​​section 22. At this time, apply torque and drilling pressure to the drill pipe to drive the retrieval device to rotate on the fish. The snap-fit ​​section 22 then performs snap-fitting operations on the snap-fitting section of the clamped section 3. After snap-fitting is completed, continue applying drilling pressure. The squeezing clamping section 1 deforms radially under pressure, and its inner and outer walls expand inward and outward respectively until its inner wall is tightly fitted with the outer wall of the clamped section 3. Then stop applying pressure. At this time, the fish and the retrieval device are fixed together. Then, drill upward to bring the retrieval device and the fish out of the wellhead together, completing the retrieval operation.

[0048] Exemplary Example 2

[0049] This exemplary embodiment provides a method for retrieving high-strength smooth falling objects in downhole, the method being based on the downhole high-strength smooth falling object retrieval device described in Exemplary Embodiment 1.

[0050] Combination Figure 1 and Figure 2 The salvage method includes a preparatory stage before salvage, and the specific steps are as follows:

[0051] S1: Measure the drill string and rotary steering tool that have been pulled out from the top, compare them with the drawings, determine whether the fracture location is the weak part of the main shaft under the rotary steering, and clarify the structure of the fish falling;

[0052] S2: Calculate the distance L2 between the groove at the upper end of the clamping section 3 where the fish is caught and the step at the lower end;

[0053] S3: Based on L2, determine the distance L1 from the inner female cone buckle end face (i.e. the lower end of the buckle part 22) of the retrieval tool to the bottom end of the retrieval tool, L2 = L1 + (1~3mm);

[0054] S4: Based on the maximum outer diameter of the clamped segment 3 of the fallen fish. Determine the inner diameter of the clamping cavity 11 Right now

[0055] The salvage method also includes the lowering of the salvage device, the specific steps of which are as follows:

[0056] S5: After installing the retrieval device and drill pipe, lower it into wellbore a;

[0057] S6: When the drill reaches a distance of 5-8m from the fish landing position, reduce the descent speed to 10-15 min / m and circulate and flush with a large volume of water.

[0058] S7: When the retrieval device is about 2m away from the top of the fallen fish, further reduce the lowering speed to 20min / m~30min / m and continue to circulate and rinse.

[0059] S8: When the retrieval device begins to fit into the clamping section 3 where the fish has fallen, the pump pressure rises rapidly. At this time, repeatedly lift and lower the retrieval device in small ranges more than 3 times. If the pump pressure rises and falls sharply, it means that the retrieval device has reached the position of the clamping section 3 where the fish has fallen.

[0060] S9: Move the retrieval device away from the section where the fish was held by the wellbore by about 0.3m and circulate and flush for 60min to 200min to clean the fish and create a good wellbore environment for retrieval.

[0061] S10: Lower the retrieval device again until it fits into the clamped section 3 of the fallen fish. Reduce the drilling fluid discharge rate to stop circulation according to the pump pressure. Slowly lower the retrieval device into the clamped section 3 of the fallen fish until the suspended weight on the ground drops by more than 5 tons. Repeat the up-and-down movement test 3 times to confirm that the retrieval thread of the snap-fit ​​part 22 of the retrieval device is in contact with the snap-fit ​​part at the top of the clamped section 3 of the fallen fish.

[0062] The salvage method also includes the fastening and clamping process of the salvage device, with the specific steps as follows:

[0063] S11: Increase the drilling pressure to over 10 tons and apply torque at a low speed, such as 5 RPM, not exceeding 40000 N.m. Use the high-strength retrieval thread of the retrieval part 22 to create a retrieval in the non-magnetic stainless steel position at the top of the fish-falling groove 31. The axial length of the retrieval thread after retrieval is about 3-5 mm. Preferably, the retrieval length can be 5 mm. The number of retrieval threads can be about 2-3. Preferably, the number of retrieval threads can be 3. When the retrieval thread of the retrieval part 22 enters the fish-falling groove 31, the torque will decrease.

[0064] S12: Continue to apply torque to the limit and gradually increase drilling pressure to 20-40 tons, repeating 5-8 times. Under the combined action of pressure generated by torque turning and drilling pressure, the lower end face of the retrieval device is subjected to strong extrusion force. The extrusion clamping section 1 gradually deforms and expands, achieving a tight fit between its inner wall and the outer wall of the clamped section 3 and the groove 31 of the main shaft under the rotary guide, thus meeting the above-mentioned positive and negative torque conditions.

[0065] The salvage method also includes the steps of unblocking and retrieving the object, as follows:

[0066] S13: After the retrieval device is combined with the fish, if the pump can be turned on, continue to circulate for 1 to 2 hours. If the pump cannot be turned on, the drill bit 5 at the lower end of the fish on the surface will be stuck by rock cuttings 6 and cannot be pulled out directly. Pulling, pressing, and shaking operations are required to release the stuck fish until it is released.

[0067] S14: After the card is released, repeat step S11 to prevent the fish from falling during the drilling process;

[0068] S15: Pull the fixed retrieval device and the fallen fish together to the wellhead to complete the retrieval operation.

[0069] In salvage operations, the main shaft and lower drill bit of the rotary guide are not heavy, usually around 0.2 tons. However, due to being stuck by rock cuttings, it usually requires a pulling force of more than 70 tons to pull them out. When making the hook, the fish will not rotate under the action of the hooking torque of the mother cone fishing teeth (i.e., the hooking part) under the downward pressure and the holding of rock cuttings. After the fish was actually salvaged and brought out of the well using the salvage device described in this invention, it could not be pulled out of the salvage device under a pulling force of 260 tons in the pull test of the ground test equipment, thus further verifying the technical effect achieved by this invention.

[0070] In summary, this invention employs a rotary buckle system and utilizes the downward pressure generated by drilling to superimpose and transfer it to the clamping section of the retrieval device. Under the constraint of the fish-dropping step structure, the clamping section of the retrieval device expands and deforms radially, its inner wall tightly fitting the outer wall of the fish, thus achieving secure clamping of the fish. Through the combined effect of these two mechanisms, the available retrieval lifting force is increased from approximately 30 tons to 100 to 260 tons, effectively solving the problem of retrieving fish from the main shaft and below under rotary guidance.

[0071] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A downhole high strength slick-balling fish device, characterized in that, The fishing device comprises an extrusion clamping section and a thread forming section, wherein, The extrusion clamping section is provided with a clamping cavity, and the clamped section of the fish can enter the extrusion clamping section along the clamping cavity, and the extrusion clamping section can be deformed in the radial direction after being subjected to pressure in the axial direction to clamp the clamped section in the clamping cavity; The thread forming section is arranged at the upper end of the extrusion clamping section, and the thread forming section is provided with a central hole, which is in communication with the clamping cavity, and the inner wall of the thread forming section is provided with a thread forming part near one end of the clamping cavity, and the thread forming part can form threads on the clamped section entering the clamping cavity; The extrusion clamping section is made of alloy structural steel, and the thread forming part is a fishing tooth, which is subjected to heat treatment and quenching and tempering so that the surface hardness is greater than HRC60; The outer wall of the clamped section near the upper end is provided with a groove, and the lower end is formed with a step, the axial length of the clamping cavity is L1, the distance between the groove and the step on the clamped section is L2, and the difference between L2 and L1 is 1-3mm; The inner and outer walls and the lower end face of the extrusion clamping section are provided with an inclined angle bevel, and the angle of the inclined angle bevel is 70-80°, so as to facilitate the initial deformation of the extrusion clamping section under pressure.

2. The high-strength slick-balling device for downhole fishing of objects according to claim 1, characterized in that, The inner diameter of the clamping cavity is φ 1 , the maximum outer diameter of the clamped section is φ 2 , and φ 1 > φ 2 .

3. A method of fishing a high strength slick catch downhole, the method comprising: The fishing method adopts the downhole high-strength smooth fish falling object fishing device of claim 1 or 2, and comprises a preparation link before fishing, which comprises measuring the size of the upper tool and determining the fracture position and the fish structure, and calculating and determining the size of the fishing device according to the size of the fish.

4. The method of claim 3, wherein, The fishing method further comprises a running link of the fishing device, which comprises running the fishing device to the upper part of the fish, entering the clamped section of the fish into the clamping cavity, and making the top end of the clamped section reach the thread forming part.

5. The method of claim 4, wherein, The fishing method further comprises a thread forming and clamping link, which comprises applying a thread forming torque on the fishing device, completing thread forming on the upper end of the clamped section through the thread forming part, and continuing to apply pressure until the lower end of the extrusion clamping section abuts against the upper end of the step of the fish, and the extrusion clamping section is deformed and expanded in the radial direction after being subjected to pressure, so that the inner wall thereof is tightly fitted with the outer wall of the clamped section to complete clamping.

6. The method of claim 5, wherein, The thread forming part forms a thread length of 3-5mm after completing thread forming, and the number of threads is 2-3.

7. The method of claim 5, wherein, The fishing method further comprises a releasing and pulling out link, which comprises: If the fishing device and the fish are stuck downhole, releasing operation is required before pulling out operation, and if the fishing device and the fish are not stuck, pulling out operation is directly performed.

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