Forging, grinding and milling treatment method for expansion pipe in vertical well section

Abstract

The invention discloses a vertical well section expansion pipe forging, grinding and milling treatment method, aiming at various complex casing damage well conditions of an expansion pipe casing damage well, a set of efficient and high-quality treatment technology is formed by pointedly adopting the treatment steps of centralizing casing milling of the interior of an expansion pipe, expansion pipe leading grinding and milling, shaping and expanding of an over-expansion pipe, expansion pipe grinding and milling, expansion pipe forging and milling and the like. The purpose of efficiently and thoroughly forging, grinding and milling the straight well section expansion pipe is achieved, the application range and the chipping treatment effect are obviously better than those of a traditional grinding and casing milling technology, development and improvement of the workover treatment technology are promoted, the wide application value is achieved, the forging, grinding and milling treatment requirements of the straight well section expansion pipe can be met, and the economic benefit is high. And the success rate and the construction time efficiency of well repair treatment of the type of wells can be improved, and the problem that the treatment difficulty is large after a vertical well section expansion pipe sleeve is damaged is effectively solved.

Description

Technical Field

[0001] This disclosure relates to the field of oilfield downhole workover technology, specifically to a process method for treating the expansion tube after casing damage in a vertical well section using forging and milling techniques. Background Technology

[0002] Currently, the shape of the damaged expansion tubing in the vertical well section of Daqing Oilfield is complex and tightly fitted to the casing. This significantly increases the difficulty of handling wells with various conditions, such as: objects falling into the expansion tubing simultaneously with the damage point; expansion tubing misalignment or deformation exceeding a certain limit; expansion tubing that cannot be retrieved and requires thorough milling and grinding; and expansion tubing requiring segmented retrieval. Existing conventional milling and grinding techniques are insufficient for effectively removing the expansion tubing under conditions of limited internal diameter. Furthermore, the milling and grinding process is prone to problems such as stuck pipe accidents, incomplete milling of debris, and tool entanglement, severely impacting the effectiveness and efficiency of well workover operations. Therefore, for wells with significantly increased handling difficulties after expansion tubing damage in the vertical well section, there is currently no effective and targeted well workover technology available. Summary of the Invention

[0003] In view of this, this disclosure provides a method for forging, grinding and milling treatment of expansion tubing in vertical well sections, which solves the problem that there is no effective and targeted well workover technology for wells with significantly increased difficulty in handling damaged expansion tubing in vertical well sections.

[0004] To solve the above-mentioned technical problems, the forging, grinding, and milling method for the expansion pipe section of a vertical well as described in this disclosure includes: For well conditions where objects fall into the expansion tube and the casing damage point are synchronized but striking the falling objects is ineffective or the falling objects inside the expansion tube have irregular fish heads that cannot be retrieved, the expansion tube straightening and casing milling treatment method is adopted to open the channel. The milling treatment inside the expansion tube is carried out using a milling tool consisting of a milling sleeve and a milling head. The milling tool is lowered above the damaged area, and after circulating the working fluid, the drill string is lowered to carry out the milling operation. The drilling pressure for the milling operation is 5-20KN, the rotation speed is 50-100r / min, and the displacement is greater than 0.5m³ / min; During the milling process, if the rotation speed decreases, it is determined that the milling tool has come into contact with the object falling inside the expansion tube. When the milling advance speed increases and the rotation speed returns to normal, the milling operation is completed.

[0005] In this disclosure and possible embodiments, during the milling operation, the kill fluid selected when the well is successfully killed is used as the circulating working fluid, and a chip catcher is installed at the return fluid outlet to collect the iron filings generated during the milling operation.

[0006] In this disclosure and possible embodiments, for well conditions where the expansion tubing in the damaged well has a misalignment ≤70mm or a deformation ≥90mm, the misalignment or deformation is treated by guided milling and enlarging. The guided milling and enlarging treatment uses a drill pipe tip milling cone, which is lowered above the misalignment or deformation. The depth of resistance encountered in the tubing is detected by lowering the tool, and the tubing string clamping force is recorded by raising the tool. The working fluid is circulated, and the drill string is lowered to perform step-by-step expansion and / or low-speed milling and enlarging treatment on the misalignment or deformation. The progress of the construction is judged based on the changes in the tubing string clamping force and rotation speed until the enlarging treatment is completed. The drilling pressure for the guiding milling and diameter expansion process is 5-10KN, the rotation speed is 30-70r / min, and the displacement is greater than 0.4m³ / min; The well-killing fluid selected when the well is successfully killed is used as the circulating working fluid.

[0007] In this disclosure and possible embodiments, after the casing damage well undergoes the lead milling and diameter expansion process, the misaligned or deformed area is subjected to expansion tube reshaping and diameter expansion process. The over-expansion tube shaping and diameter expansion process uses the same processing method as the guide milling and diameter expansion process.

[0008] In this disclosure and possible embodiments, for wells where the expansion tubing in a damaged well has no further usability and cannot be retrieved, well workover is carried out by milling the expansion tubing at the damaged area. The milling process uses a drill bit or an eccentric drill bit as the milling tool. The milling tool is lowered above the damaged area, and the depth of obstruction and the clamping force of the tubing string during the lifting process are recorded. The working fluid is circulated, and the drill string is lowered to perform milling operations on the damaged area. The progress of the tool milling is judged based on the changes in rotation speed, the footage, and the clamping force of the tubing string after the rotation stops, until the milling operation is completed. The drilling pressure for the milling operation is 5-20 kN; the rotation speed is 50-100 r / min; and the displacement is greater than 0.5 m³ / min.

[0009] In this disclosure and possible embodiments, the processing method further includes: The expansion tube inside the damaged well is retrieved in sections. The section retrieval process includes cutting the expansion tube, and the cutting tool used for cutting the expansion tube is a hydraulic internal cutting tool for the expansion tube. The drilling pressure used during the cutting process is 5-10 kN; the rotation speed is 60-100 r / min; and the displacement is greater than 0.8 m³ / min.

[0010] In this disclosure and possible embodiments, a special retrieval tool for expansion tubes is used for segmented retrieval. The retrieval tool is lowered to a depth above the expected depth, and a pump is turned on to circulate and flush the expansion tube to capture it. After the tube is released, it is retrieved.

[0011] In this disclosure and possible embodiments, the processing method further includes: The expansion tube forging and milling process is performed on the damaged area. The expansion tube forging and milling process uses a special forward forging and milling cutter for expansion tubes as the forging and milling tool. The drilling pressure during the expansion tube forging and milling process is 5-30kN; the rotation speed is 80-120r / min; and the displacement is greater than 0.4m³ / min.

[0012] In this disclosure and possible embodiments, after the expansion tube is forged and milled, the channel finding process is continued at the damaged area. The channel finding process uses a pen tip tool. The pen tip tool is lowered to pre-probe the obstruction depth inside the tube. After encountering obstruction, the tube string is lifted up. The obstruction depth inside the tube and the clamping force of the tube string during the lifting process are recorded. When the clamping force of the tube string is greater than the obstruction depth, it is determined that the lower fracture point has been reached, and the channel finding process is completed.

[0013] In this disclosure and possible embodiments, the processing method further includes: The well cleaning process involves the following steps: When the well cleaning clamping force exceeds 20kN, a milling cone is used as the well cleaning tool. The lowering speed of the well cleaning tool is controlled to be less than or equal to 20m / min. When the tool is lowered to 100m from the damaged expansion tube, the lowering speed is no more than 10m / min. The milling cone is used to mill the casing above the damaged area to restore the inner diameter. If the well cleaning clamping force is less than 20kN, a well cleaning gauge is used to clean the casing above the broken section.

[0014] This disclosure has the following beneficial effects: This disclosed method for forging, grinding, and milling treatment of expansion tubing in vertical well sections addresses various complex casing damage conditions in wells with damaged expansion tubing. It employs targeted treatment steps including internal milling to straighten the expansion tubing, milling to guide the expansion tubing, reshaping and expanding the diameter of the expansion tubing, milling, and forging milling. This forms a highly efficient and high-quality treatment technology, achieving the goal of efficient and thorough forging, grinding, and milling of expansion tubing in vertical well sections. Its applicability and debris removal effect are significantly superior to traditional milling and casing milling processes, promoting the development and improvement of well workover technology. It has broad application value, can meet the needs of forging, grinding, and milling treatment of expansion tubing in vertical well sections, and can improve the success rate and construction time of well workover treatment for this type of well. It effectively reduces human resource input and minimizes the impact of ineffective treatment of damaged expansion tubing wells on surrounding connected wells, thus achieving block production recovery and having significant implications for the sustainable development of oilfields. Detailed Implementation

[0015] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0016] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0017] In this embodiment of the disclosure, the forging, milling, and processing method for the expansion pipe section of a vertical well includes the following specific steps: S10: Preparations before processing: (1) Data preparation: Obtain data on the structure, dimensions, steel grade, and wall thickness of the casing and expansion tube in the well damaged by the expansion tube, as well as cement return height, well inclination data, previous construction status, current well tubing string, formation lithology, and casing damage status.

[0018] (2) Well preparation: well washing and well control.

[0019] (3) Deal with the stuck tube inside the expansion tube: unblock by moving the tube and / or turning it upside down.

[0020] (4) Investigation of casing damage technical condition: Print a suitable lead mold to confirm the location of the expansion head of the expansion tube in the well and the casing damage condition and depth.

[0021] (5) Hitting the falling object: The falling object should be flashed out of the damaged part inside the expansion tube, so that it can have a subsequent channel for hitting inside the expansion tube and conditions for guiding milling and expanding the diameter inside the expansion tube.

[0022] S20: Internal milling operation for the expansion tube: For well conditions where debris falls into the expansion tube simultaneously with the casing damage point but striking the debris is ineffective, or where the debris's "fish head" is irregular and cannot be retrieved, the expansion tube straightening and milling operation process described in this step is used for well workover to open the access channel, as detailed below: a. Preparation of milling tools: Milling sleeve and milling head. In this embodiment of the present disclosure, the preferred milling tools are an extended positioning milling sleeve for Φ102-4500mm expansion tubes and a high-efficiency Kennametal milling head for Φ102mm expansion tubes.

[0023] b. Assemble the milling sleeve column: In the preferred embodiment of this disclosure, from bottom to top, it consists of a Φ102mm expansion tube-specific high-efficiency Kennametal alloy milling sleeve head + a Φ102mm-4500mm expansion tube-specific extended positioning milling sleeve + a safety joint + a weighted drill rod / drill collar + a drill rod + a square drill rod.

[0024] c. Construction parameters: In the preferred embodiment of this disclosure, during the milling operation, the drilling pressure is controlled at 5-20KN, the rotation speed is 50-100r / min, and the displacement is greater than 0.5m³ / min.

[0025] d. Process flow: Lower the milling tool above the casing damage area, preferably 2m above the casing damage area, circulate the working fluid, record the suspended weight, and slowly lower the drill string for milling. If the rotation speed drops slightly, it is determined that the milling tool has contacted the casing damage area inside the expansion tube. If the milling footage is slightly faster and the rotation speed returns to normal, the milling work is completed. Stop the rotation and pump, and lift the drill string. During the milling process, use the kill fluid selected when the well was successfully killed as the circulating working fluid. During the milling process, place a cuttings catcher at the return fluid outlet to collect iron cuttings.

[0026] S30: Expansion tube guides milling and diameter expansion operations: For wells with casing damage where the expansion tubing is misaligned by ≤70mm or deformed by ≥90mm, this step involves guided milling and enlarging of the expansion tubing for well workover, as detailed below: (1) Locating the punching channel inside the expansion tube: Lower the pen tip to above the damaged area of ​​the expansion tube, preferably 0.5m to 1m above the damaged area. Lower the tool to pre-probe the depth of resistance inside the tube. After encountering resistance, lift the tube to above the damaged area of ​​the expansion tube, preferably 3m to 4m above the damaged area. Record the depth of resistance inside the tube, the clamping force of the tube during the lifting process, and the rotation angle. Lower the tube again and repeat this process several times. Determine whether the tool has entered the lower fracture surface based on the clamping force of the tube and the depth of resistance. Generally, a large clamping force and a deep resistance indicate that the tool has entered the lower fracture surface.

[0027] (2) Expansion tube guides milling and diameter expansion: a. Tool preparation: Φ60~105mm drill rod milling taper, Φ95~105mm drill rod milling taper and matching milling taper short connector.

[0028] b. Construction parameters: In this embodiment of the present disclosure, the preferred drilling pressure during the milling process is 5-10KN, the rotation speed is 30-70r / min, and the displacement is greater than 0.4m³ / min; the milling operation is mainly based on punching expansion, followed by low-speed filing, in order to prevent the expansion tube from opening or shifting.

[0029] c. For milling and expanding the diameter of expansion tubes with a misalignment ≤70mm: Lower a Φ60~105mm drill rod with a milling cone tip to above the misalignment of the expansion tube, preferably 0.5m~1m above the misalignment. Lower the tool to pre-probe the depth of resistance inside the tube. After encountering resistance, lift the tubing to above the misalignment, preferably 3m~4m above the misalignment. Record the depth of resistance inside the tube and the clamping force and rotation angle of the tubing during the lifting process. Lower the tubing again and repeat this process multiple times. Determine whether the tip has entered the lower fracture based on the clamping force and the depth of resistance. If the tip has entered the fracture, then, based on the tip's guidance, use the weight of the tubing to gradually expand and shape the damaged area with the milling cone slope. Alternatively, based on the tip's guidance, use the milling cone slope to gradually mill and expand the damaged area with low-speed grinding. During milling, pay attention to circulating the working fluid to prevent the drill from getting stuck.

[0030] d. Milling and enlarging process for expansion tubing deformation ≥90mm: Run Φ95~105mm drill pipe and milling cone, along with matching milling cone short-circuit, to above the deformation point of the expansion tubing casing, preferably 2m above the deformation point. Lower the tool to pre-probe the depth of obstruction inside the tubing. After encountering obstruction, raise the tubing string to above the deformation point of the expansion tubing casing, preferably 3m~4m above the deformation point. Record the depth of obstruction inside the tubing and the clamping force of the tubing string during the raising process. Circulate the working fluid. Slowly lower the drill string to perform step-by-step expansion or low-speed milling and enlarging of the casing damage point. Judge the tool shaping status and effect based on the changes in tubing string clamping force and rotation speed. After the shaping work is completed, stop the rotation and pump, and raise the drill string. During the shaping process, use the kill fluid selected when the well was successfully killed as the circulating working fluid. During the milling process, place a cuttings catcher at the return fluid outlet to collect iron cuttings.

[0031] (3) Investigation of the technical condition of the casing below the expansion pipe: Print a suitable lead mold to confirm the condition and depth of the casing below the expansion pipe in the well.

[0032] (4) Expanding the diameter of the expansion tube: Following the expansion tube milling and expansion construction steps described in step (2), the expansion tube is shaped and expanded so that it can be used to repair and retrieve fish falling below.

[0033] (5) Repairing fish through the break: lower the polishing shoe / guide the polishing shoe to repair the irregular fish head.

[0034] (6) Retrieval through the break: Lower the retrieval tool to retrieve the object that has fallen through the expansion tube below.

[0035] (7) Well Cleaning: Use a well cleaning gauge to clean the casing above the break point and verify its passability. During well cleaning, follow the requirements of stable operation, controlling the tubing string lowering speed to be less than or equal to 20 m / min, and when lowering to 100 m from the damaged expansion tube, the lowering speed should not exceed 10 m / min. If the well cleaning clamping force exceeds 20 kN, use a milling tap to gradually mill the casing above the damaged expansion tube to restore the inner diameter; if the well cleaning clamping force is less than 20 kN, measure the well diameter in one step.

[0036] (8) First logging: Engineering logging to determine the damage to the downhole expansion tube and casing.

[0037] S40: Expansion tube milling operation: For wells where the expansion tubing inside the casing is beyond repair but cannot be retrieved and requires thorough milling, the well should be repaired according to the expansion tubing milling operation procedure described in this step, as follows: a. Tool preparation: eyelet grinding shoe, eccentric grinding shoe. Before lowering the tools into the well, confirm that the tools are undamaged and meet the construction requirements.

[0038] b. Tool selection: The eye-grinding shoe is suitable for complex well conditions such as milling the expansion head on the front of the flammable expansion tube or milling the hydraulic expansion tube before retrieval; the eccentric grinding shoe is suitable for simple well conditions such as milling the expansion tube and casing with an interference fit or grinding off the remaining part of the expansion tube at the break.

[0039] c. Pipeline structure: from bottom to top: eyelet / eccentric eyelet + safety joint + weighted drill pipe / drill collar + centralizer + drill pipe + square drill pipe.

[0040] d. Construction parameters: In the embodiments of this disclosure, the preferred drilling pressure for milling operations is 5-20 kN; the rotation speed is 50-100 r / min; and the displacement is greater than 0.5 m³ / min.

[0041] e. Process flow: Run the drill string / eccentric drill string to above the design depth, preferably 2m above the design depth. Lower the tool to pre-probe the depth of obstruction in the casing. After encountering obstruction, raise the tubing string to above the design depth, preferably 3m to 4m above the design depth. Record the depth of obstruction in the casing and the clamping force of the tubing string during the raising process. Circulate the working fluid. Slowly lower the drill string to perform milling operations on the damaged casing. Judge the milling situation and effect based on the changes in rotation speed, footage, and the clamping force of the tubing string after stopping the rotation. After the milling work is completed, stop the rotation and pump, and raise the drill string. During the milling process, use the kill fluid selected when the well was successfully killed as the circulating working fluid. During the milling process, place a cuttings catcher at the return fluid outlet to collect iron cuttings.

[0042] This embodiment employs an eccentric milling tool to mill deformed expansion tubes. The bottom area of ​​the tool makes the initial downward cut into the expansion tube, while the lateral off-axis milling area performs a secondary fine cut on the overly fitted expansion tube and the debris already processed at the bottom, reducing them to smaller pieces. This achieves thorough milling of the interference fit of the expansion tube, and the small debris is easily removed from the surface, effectively eliminating the problem of incomplete milling. Furthermore, because its milling area uses an eccentric, non-complete cylindrical structure, the risk of residue clogging the drill bit is reduced. Even if slightly stuck, it can be directly lifted out or the small fragments that no longer adhere to the casing can be removed.

[0043] S50: Cutting and retrieval operations of expansion tubes: For wells with damaged casing where the expansion pipe needs to be retrieved in sections, the retrieval process should be carried out according to the following steps: (1) Cutting the expansion tube: a. Tool preparation: Hydraulic internal cutter for expansion tubing, used to cut expansion tubing sections before retrieval. Before lowering the tool into the well, confirm that it is undamaged and meets the construction requirements.

[0044] b. Pipeline structure: expansion tube hydraulic internal cutter + heavy-duty drill pipe / drill collar + drill pipe + square drill pipe.

[0045] c. Construction parameters: In this embodiment of the present disclosure, the preferred drilling pressure for cutting the expansion tube is 5-10 kN; the rotation speed is 60-100 r / min; and the discharge rate is greater than 0.8 m³ / min.

[0046] d. Process Flow: Connect the tool and drill pipe and lower them to the predetermined position. After the rotary table starts rotating, preferably start the pump pressure and gradually increase it from 3 MPa to 12 MPa. The hydraulic pressure is applied through the nozzle, pushing the piston downward. The piston pushes the cutter body outward, gradually cutting the casing. When the pump pressure gauge shows a significant drop, it indicates that the casing has been cut. (2) Retrieving the expansion tube: a. Tool preparation: Special retrieval tool for expansion tubes, suitable for handling retrievalable expansion tubes.

[0047] b. Tubing structure: Expansion tube special retrieval tool + weighted drill rod / drill collar + drill rod + square drill rod.

[0048] c. Process flow: Use a special retrieval tool for the expansion tube to reach a depth above the expected depth and start pump circulation flushing, preferably 2m above the design depth. Slowly lower the drill string to capture the expansion tube, and then remove the drill string after it is unstuck.

[0049] S60: Expansion tube forging and milling operation: For wells with complex casing damage requiring milling of the expansion tubing, the well workover procedure in this step is as follows: (1) Forging and milling expansion tubes: a. Tool preparation: Forward milling cutter for expansion tubes, used for milling expansion tube casing damage in complex well conditions.

[0050] b. Pipeline structure: from bottom to top: straightening tool (small diameter with guide) + expansion tube special forward forging end mill + straightening tool + heavy-duty drill rod / drill collar + drill rod + square drill rod.

[0051] c. Construction parameters: In this embodiment of the present disclosure, the preferred forging and milling drilling pressure is 5-30kN; the rotation speed is 80-120r / min; and the displacement is greater than 0.4m³ / min.

[0052] d. Process Flow: Lower the tool above the desired milling position, preferably 0.5m above the milling position. Turn on the rotary table and the pump pressure, gradually increasing it to approximately 14MPa. The pressure pushes the piston assembly to lift the cutter body. After the cutter body reaches its maximum extension, the pump pressure drops back to approximately 10-12MPa. Slowly lower the milling expansion tube to the designated position. After the operation is completed, stop the pump and rotary table. The piston assembly moves upward under the spring force, and the cutter automatically retracts, allowing the tool to be removed. After the milling operation is completed, stop the rotary table and pump, and lift the drill string.

[0053] (2) Find the channel: Lower the pen tip to above the break, preferably 0.5m to 1m above the break. Lower the tool to pre-probe the depth of resistance inside the tube. After encountering resistance, lift the tube to above the break, preferably 3m to 4m above the break. Record the depth of resistance inside the tube and the clamping force and rotation angle of the tube during the lifting process. Lower the tube again and repeat the process several times. Determine whether the tool has entered the lower break based on the clamping force and the depth of resistance. Generally, a large clamping force and a deep resistance indicate that the tool has entered the lower break.

[0054] (3) Shaping and expanding diameter: The channel is opened and the diameter is expanded at the same time by using punching expansion or filing and milling channel technology.

[0055] (4) After well cleaning, reinforce or scrap the well.

[0056] In this embodiment of the disclosure, a special forward forging milling cutter for expansion tubes is used to process the expansion tubes. The purpose is to use the milling area on the end face of the forging milling cutter on the side of the tool to perform fine forging milling on the expansion tubes. After forging milling, the expansion tubes have small debris that is easily discharged with the circulating fluid, thereby effectively eliminating the risk of incomplete processing of the expansion tubes and residues covering the drill bit.

[0057] Well B2-6-25: The expansion tube and casing were tightly fitted, but the flat-bottomed milling shoe did not mill it thoroughly, and the milled expansion tube was prone to jamming. The expansion tube section was long. Finally, the patented method was used to mill the expansion tube with an eccentric milling shoe. However, the retrieval failed after milling the expansion head. Then, the expansion tube was cut twice with a hydraulic internal cutter. Two sections of the expansion tube above the fracture (4m and 4.4m) were retrieved one by one. The remaining part of the expansion tube was milled off with an eccentric milling shoe. After milling and expanding the diameter of the fracture, the secondary reinforcement was successful.

[0058] Well Z62-572: The expansion tube broke simultaneously with the falling object. The falling object was not released after being struck, and its irregular shape made retrieval impossible. Ultimately, using the method described in this patented patent, a special extended positioning sleeve milling cylinder was used to mill the broken section of the expansion tube and the falling object, successfully releasing the object and opening the channel. After milling and expanding the diameter of the broken section, the remaining falling object was retrieved.

[0059] Well Z81-P56: The inner casing of the expansion tube has small diameter changes due to damage, and the shaping and expansion are difficult. Using the method of this patent, a small drill pipe with a Φ60~105mm tip is used to guide the expansion to 105mm by milling the staggered fracture surface, thus opening the channel.

[0060] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A method of mill and ream expansion of a straight hole section, characterized in that, The application relates to a straight well section expansion pipe forging and milling treatment method. The expansion pipe inside falling object and casing damage point are synchronous, but the falling object is invalid or the fish head of the expansion pipe inside falling object is irregular, so the forging and milling treatment method of the expansion pipe inside centralizing and milling is used to open the channel. The expansion pipe inside centralizing and milling treatment adopts a milling tool composed of a milling barrel and a milling head, the milling tool is lowered into the upper part of the casing damage position, circulating working liquid is used to lower the drilling tool to carry out the milling construction. The drilling pressure of the milling construction is 5-20KN, the rotating speed is 50-100r / min, and the displacement is greater than 0.5m3 / min. During the milling construction, when the rotating speed appears a downward trend, it is judged that the milling tool has contacted with the expansion pipe inside falling object, when the milling footage is accelerated and the rotating speed is restored to normal, the milling work is completed.

2. The straight well section expansion pipe forging and milling treatment method according to claim 1, wherein during the milling construction, the kill fluid selected when the well killing is successful is used as the circulating working liquid, and a chip catcher is arranged at the outlet of the flowback liquid to collect the iron filings generated in the milling operation.

3. The straight well section expansion pipe forging and milling treatment method according to claim 1 or 2, wherein for the well condition that the expansion pipe in the casing damage well is broken for less than 70mm or is deformed by more than 90mm, the broken part or the deformed part is treated by leading milling and expanding, the leading milling and expanding treatment adopts a drill pipe pen point milling cone, the drill pipe pen point milling cone is lowered to the upper part of the broken part or the deformed part, the tool probe pipe is used to detect the resistance depth in the pipe, the pipe string clamping force in the lifting process is recorded by lifting the tool, the circulating working liquid is circulated, the drilling tool is lowered to carry out the step-by-step inflation construction and / or the low-speed milling and expanding construction on the broken part or the deformed part, the construction progress is judged according to the pipe string clamping force and the rotating speed change, and the expanding treatment is completed. The drilling pressure of the leading milling and expanding treatment is 5-10KN, the rotating speed is 30-70r / min, and the displacement is greater than 0.4m3 / min. The kill fluid selected when the well killing is successful is used as the circulating working liquid.

4. The straight well section expansion pipe forging and milling treatment method according to claim 3, wherein after the casing damage well is subjected to the leading milling and expanding treatment, the over-expansion pipe shaping and expanding treatment is carried out on the broken part or the deformed part. The over-expansion pipe shaping and expanding treatment adopts the same treatment method as the leading milling and expanding treatment.

5. The straight well section expansion pipe forging and milling treatment method according to claim 1, 2 or 4, wherein for the well condition that the expansion pipe in the casing damage well has no further utilization value and cannot be fished out, the expansion pipe milling treatment is used to carry out the well repair, the expansion pipe milling treatment adopts a leading eye milling shoe or an eccentric milling shoe as a milling tool, the milling tool is lowered into the upper part of the casing damage position, the resistance depth and the pipe string clamping force in the lifting process are recorded, the circulating working liquid is circulated, the drilling tool is lowered to carry out the milling construction on the casing damage position, the tool milling progress is judged according to the rotating speed change, the footage and the pipe string clamping force after the rotation is stopped, and the milling construction is completed. The drilling pressure of the milling construction is 5-20kN, the rotating speed is 50-100r / min, and the displacement is greater than 0.5m3 / min. The application further relates to ​ ​ ​ 6. The method of claim 5, wherein: ​ The segmented fishing treatment of the expansion pipe in the casing damage well comprises an expansion pipe cutting treatment using an expansion pipe hydraulic internal cutter; The WOB during the cutting treatment is 5-10 kN; The rotation speed is 60-100 r / min, and the displacement is greater than 0.8 m3 / min.

7. The straight hole section expansion pipe forging and milling treatment method according to claim 6, characterized in that: The segmented fishing is performed using an expansion pipe special fishing tool, the fishing tool is lowered to above the expected depth, and pumping is performed for circulation flushing to capture the expansion pipe, and the captured expansion pipe is pulled out after the trip.

8. The method of claim 6 or 7, wherein, Further comprising: The expansion pipe forging and milling treatment of the casing damage section uses an expansion pipe special positive forging and milling cutter as the forging and milling tool, and the WOB during the expansion pipe forging and milling treatment is 5-30 kN; The rotation speed is 80-120 r / min, and the displacement is greater than 0.4 m3 / min.

9. The straight hole section expansion pipe forging and milling treatment method according to claim 8, characterized in that: After the expansion pipe forging and milling treatment, the channel finding treatment of the casing damage section is continued, the channel finding treatment uses a pen point tool, the pen point tool is lowered to the resistance encountered depth in the pre-probing pipe, the pipe string is lifted after the resistance is encountered, the pipe resistance encountered depth and the pipe string clamping force during the lifting process are recorded, and when the pipe string clamping force is greater than the resistance encountered depth, it is determined that the lower fracture is entered, and the channel finding treatment is completed.

10. The method of claim 9, wherein, Further comprising: The through-hole treatment step, when the through-hole clamping force is greater than 20 kN, a milling cone is used as the through-hole tool, the lowering speed of the through-hole tool is controlled to be less than or equal to 20 m / min, and when the through-hole tool is lowered to 100 m away from the expansion pipe casing damage section, the lowering speed is not greater than 10 m / min; the milling cone is used to gradually mill the casing above the casing damage section to restore the internal drift diameter; if the through-hole clamping force is less than 20 kN, a through-hole gauge is used to perform the through-hole treatment on the casing above the fracture.