A retractable casing mill tool and method

Abstract

The present application relates to a kind of retractable casing mill tool and method, belong to oil and gas well completion and workover operation field.The present application discloses a kind of retractable casing mill tool and method, including tool body, screw rod mechanism, three-petal blade wing, rotating shaft;The screw rod mechanism is installed on the rotating shaft, the rotating shaft is axially installed in the tool body;Three support leg control elements are evenly arranged on the screw rod mechanism, and support leg control element is driven by the screw rod movement of screw rod mechanism and is retracted in the radial direction of tool body;The support leg control element is hinged with the inner wall of blade wing.The present application can be in the process of oil and gas well production, completion or workover operation, for local deformation, corrosion, fracture or cement ring solidification bad well section carries out efficient repair, avoids the huge expense and the extension operation cycle brought by replacement whole pipe column.

Description

Technical Field

[0001] This invention relates to a retractable casing milling tool and method, belonging to the field of oil and gas well completion and workover operations. Background Technology

[0002] During the drilling, completion, and subsequent production processes of oil and gas wells, the casing system and cement sheath play crucial roles in wellbore stability, interlayer isolation, and protection. However, with increasing well depth, more complex formation conditions, and deteriorating long-term service environments, the following types of problems often arise:

[0003] Casing damage or deformation; 1. Formation movement or abnormal pressure can cause the casing to bend, bulge or crack; 2. Corrosion and stress corrosion can also cause local perforation or thinning of the casing, increasing the risk of downhole accidents; 3. Local deformation, dent or rupture caused by mechanical impact or other downhole operation accidents.

[0004] Poor cement curing; 1. Due to insufficient control of cementing process, substandard cement return height or cement slurry quality problems, cement sheath voids, delamination or micro-annular gaps may form; 2. In this case, wellbore seal failure may occur, which may easily lead to interlayer leakage or other safety hazards.

[0005] Overall quality is substandard; 1. When there are quality problems with both the casing and the cement sheath, the overall integrity of the wellbore is greatly reduced, and in severe cases, emergency well repair is required; 2. Replacing the entire well section with tubing will inevitably lead to high operating costs and a long construction period.

[0006] For locally damaged well sections, the industry often adopts milling to remove the damaged sections before running patch tubing or thinner casing to ensure subsequent production safety. Most existing milling tools have limitations in terms of outer diameter, cutting efficiency, and operational flexibility: on the one hand, the outer diameter cannot be freely adjusted downhole, limiting throughput; on the other hand, insufficient contact between the cutter blades and the wellbore reduces cutting efficiency and increases operational risks. Summary of the Invention

[0007] In order to overcome the defects in the prior art, the present invention aims to provide a retractable sleeve milling tool and method.

[0008] The technical solution provided by this invention to solve the above-mentioned technical problems is: a retractable sleeve milling tool, comprising a tool body, a lead screw mechanism, a three-lobed cutter wing, and a rotating shaft; the lead screw mechanism is mounted on the rotating shaft, and the rotating shaft is axially mounted inside the tool body; three support leg control elements are evenly distributed on the lead screw mechanism, and the support leg control elements are extended and retracted radially in the tool body by the movement of the lead screw of the lead screw mechanism; the support leg control elements are hinged to the inner wall of the cutter wing.

[0009] A further technical solution is that the blade is a spiral blade, and the three-lobed spiral blade forms a cylinder when it contracts.

[0010] A further technical solution is that the outer wall of the blade is provided with a helical carbide blade.

[0011] A further technical solution is that the outer wall of the spiral cemented carbide insert is provided with a number of cutting teeth.

[0012] A further technical solution is that the lead screw mechanism includes a cylindrical frame and three lead screw assemblies axially distributed on the outer wall of the cylindrical frame. Each lead screw assembly includes two linkage mechanisms, a lead screw, and a lead screw drive mechanism. The lead screw drive mechanism drives the lead screw to rotate. Each end of the lead screw is provided with a slider. The linkage mechanisms are respectively hinged to the sliders, the support leg control element, and the outer wall of the cylindrical frame. The sliders move axially on the lead screw, causing the support leg control element to extend and retract radially.

[0013] A further technical solution is to have two sliders move simultaneously outward or inward on the lead screw.

[0014] A further technical solution is to provide a force sensing device between the lead screw mechanism and the support leg control element, which is used to monitor the contact pressure between the cutter wing and the inner wall of the sleeve in real time, and to feed the pressure data back to the ground control system.

[0015] A further technical solution is to have a helical gap between two adjacent helical carbide cutting tools, which is used for chip removal.

[0016] A further technical solution is that a number of fixed rods are evenly distributed axially on the inner wall of the tool body, and the rotating shaft is disposed in a receiving cavity formed axially by the number of fixed rods.

[0017] A retractable sleeve milling method specifically includes the following steps:

[0018] Step 1: Preparation and Running into the Well: Assemble the retractable milling tool on the surface and connect it to the lower end of the running tubing string. Connect the retractable casing milling tool to the power drive unit. Turn on the circulating mud pump and ensure that the hollow passage of the tool is unobstructed. Then slowly lower the tool into the well and use conventional depth sounding methods to move the tool to the target well section.

[0019] Step 2, Positioning and Alignment: When the tool is lowered close to the section of the target casing that needs to be milled, the lowering speed is slowed down and the tool position is accurately determined using downhole positioning methods; logging data is used to determine whether the tool has reached the designated depth; after the surface control system confirms that the tool's depth and attitude are correct based on sensor feedback, it commands the lowering to stop.

[0020] Step 3, Blade Deployment: After positioning, start the milling tool deployment program; the ground operator issues the deployment command, and the power source drives the lead screw mechanism to move; as the lead screw advances, the support leg control element gradually pushes the three blades outward.

[0021] Step 4, Milling Execution: After confirming that the cutter blades are fully deployed and making stable contact, start the rotational power to perform casing milling operations; depending on the tool configuration, a surface turntable can be used to rotate the entire casing string, or a downhole hydraulic motor / electric motor can be used to drive the cutter blades to rotate and cut; during this process, the control system enters automatic adjustment closed-loop mode:

[0022] Step 5, Vibration and Stability Control: The attitude sensor monitors the vibration level and tool eccentricity during high-speed rotation; if abnormal vibration occurs, the control system will adjust the rotation speed or blade pressure to reduce the vibration.

[0023] Step 6, Blade Retraction: Once the expected milling depth is reached or the sleeve has been completely removed and the work objective is achieved, stop the rotational power and end the milling process; then issue a blade retraction command to drive the lead screw mechanism to move in the opposite direction, retracting the three blades from the deployed state to a position close to the tool body;

[0024] Step 7: Remove the wellbore: Start the mud circulation to thoroughly clean the wellbore and wash away any remaining cuttings; then slowly lift the tubing string to remove the tool from the well; when passing through previously deformed or narrow well sections, the tool can pass safely without getting stuck because it has shrunk to a small diameter; finally, lift the tool to the surface, and the entire milling operation is complete.

[0025] This invention offers the following advantages: It enables efficient repair of well sections with localized deformation, corrosion, fracture, or poorly cured cement sheaths during oil and gas well production, completion, or workover operations, avoiding the significant costs and extended operating time associated with replacing the entire tubing string. The tool utilizes a lead screw drive and support structure to achieve radial extension and retraction of the cutter blades, and improves cutting efficiency and durability through a rational cutter blade shape and cutting component design. Based on a modular approach, users can select different cutting teeth or carbide inserts according to well conditions, and replace or repair worn parts after use, reducing overall operating costs. Attached Figure Description

[0026] Figure 1 This is a three-dimensional perspective view of the present invention;

[0027] Figure 2 This is the left view of the present invention;

[0028] Figure 3 A three-dimensional view of the tool's main body;

[0029] Figure 4 This is a three-dimensional view of the lead screw mechanism;

[0030] Figure 5 This is a partial enlarged view of the lead screw mechanism. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1-5 As shown, a retractable sleeve milling tool of the present invention includes a tool body 1, a lead screw mechanism 2, a three-lobed cutter wing 3, and a rotating shaft 4. The lead screw mechanism 2 is mounted on the rotating shaft 1, and the rotating shaft 1 drives the lead screw mechanism 2 to rotate as a whole. The rotating shaft 4 is axially mounted inside the tool body 1. Three support leg control elements 5 are evenly distributed on the lead screw mechanism 2. The movement of the lead screw of the lead screw mechanism 2 drives the support leg control elements 5 to extend and retract in the radial direction of the tool body 1. The support leg control elements 5 are hinged to the inner wall of the cutter wing 3 and retract or extend with the axial movement of the lead screw mechanism 2. When the three-lobed cutter wing 3 retracts, the overall outer diameter of the sleeve milling tool decreases. When the three-lobed cutter wing 3 extends, its outer edge is close to the inner wall of the sleeve for milling cutting.

[0033] The tool body 1 has a hollow channel inside for the flow of mud or cleaning fluid; the hollow channel inside the tool body 1 can be connected to the downhole pumping system, thereby realizing circulating cooling, chip removal and flushing of the cutting area during the milling operation.

[0034] The lead screw mechanism 2 is arranged along the axial direction of the tool body 1 and generates axial displacement under rotation or hydraulic drive;

[0035] In this embodiment, the blade 3 is a spiral blade, and the three-lobed spiral blade forms a cylinder when it contracts.

[0036] like Figure 1 As shown, in this embodiment, a spiral carbide blade 6 is provided on the outer wall of the blade 3, and a plurality of cutting teeth 7 are provided on the outer wall of the spiral carbide blade 6. This is used to improve the efficiency and wear resistance in the sleeve milling and cutting process.

[0037] like Figure 4 and 5As shown, in this embodiment, the lead screw mechanism 2 includes a cylindrical frame 21 and three lead screw assemblies axially distributed on the outer wall of the cylindrical frame 21. Each lead screw assembly includes two linkage mechanisms 22, a lead screw 23, and a lead screw drive mechanism 24. The lead screw drive mechanism 24 drives the lead screw 23 to rotate. Slider blocks 25 are respectively provided at both ends of the lead screw. The linkage mechanisms are hinged to the sliders, the support leg control element, and the outer wall of the cylindrical frame, respectively. The sliders move axially on the lead screw, causing the support leg control element to extend and retract radially. The two sliders 25 move simultaneously outward or inward on the lead screw 23. In this embodiment, to better monitor the tool's working condition, a preferred implementation is that a force sensing device is provided between the lead screw mechanism 2 and the support leg control element 5 to monitor the contact pressure between the blade 3 and the inner wall of the sleeve in real time and feed the pressure data back to the ground control system.

[0038] like Figure 1 As shown, in this embodiment, there is a helical gap between two adjacent helical carbide inserts for conveying flushing fluid and discharging cutting chips during the milling operation.

[0039] like Figure 1 As shown, in this embodiment, three fixed rods 8 are axially evenly distributed on the inner wall of the tool body 1, and the rotating shaft 4 is located in the middle of the three fixed rods 8.

[0040] like Figure 3 As shown, in this embodiment, the tool body 1 includes two oppositely arranged upper and lower connectors, which are connected by three fixed rods 8. The lead screw mechanism 2 is located between the upper and lower connectors, and the inner ends of the upper and lower connectors are both conical ends. When the three-lobed blade 3 retracts, it wraps around the two conical ends.

[0041] To achieve complex control processes and functions, this embodiment of the invention is based on an integrated intelligent system. This system consists of two main parts: downhole and surface, each containing several functional modules.

[0042] Downhole execution module:

[0043] It comprises two parts: a mechanical unit and a power unit. The mechanical unit, namely the aforementioned retractable milling tool body, consists of a lead screw drive mechanism, support linkage, and three-lobed cutter blades, and is responsible for directly physical cutting the casing. The power unit includes a downhole motor (such as a hydraulic motor or electric motor) that provides torque for the cutter blade rotation, and a propulsion device that drives the lead screw mechanism to extend and retract (which can be driven by the same motor through a clutch switch, or by a separate hydraulic piston device). This execution module completes the actions of cutting blade deployment / retraction and rotary cutting under control commands, and is the field operation unit of the entire system.

[0044] Downhole sensing and measurement module:

[0045] Various sensors integrated into the tool body and power unit. These mainly include:

[0046] 1. Force sensor: Installed between the lead screw and connecting rod, it is used to measure the opening force of the cutter blades or the contact pressure with the well wall. This is the key to force control, enabling the system to sense changes in the force on the cutter blades.

[0047] 2. Torque sensor: This can be obtained by measuring the motor's current / torque or by installing a strain gauge on the rotating shaft, and is used to monitor the magnitude of cutting resistance.

[0048] 3. Accelerometer and gyroscope: detect the vibration acceleration and attitude changes of the tool, identify whether strong vibrations or tilting / eccentricity occur, and assist in stability control.

[0049] 4. Pressure sensor: Used to monitor the pressure of the hydraulic system (such as the pressure supplied by the hydraulic motor and the pressure of the propulsion cylinder) and the pressure of the circulating fluid in the wellbore, in order to determine whether the hydraulic system is normal and whether the annulus is blocked.

[0050] 5. Temperature sensor: measures the temperature of downhole motors, electrical control units, or hydraulic oil for over-temperature protection.

[0051] 6. Position / displacement sensors: such as encoders, used to track the number of revolutions of the leadscrew or the advance length, thereby accurately calculating the current opening diameter of the cutter blade. Magnetic positioning devices may also be included for calibrating the depth position with the ground.

[0052] Downhole control and communication module:

[0053] A compact downhole control unit (an electronic device capable of withstanding high temperatures and pressures), equipped with a microprocessor and basic algorithms, processes sensor data locally and executes control commands. It is responsible for packaging critical monitoring data in real time and transmitting it to the surface via a communication module; simultaneously, it receives and executes control commands transmitted from the surface. The communication module can transmit data bidirectionally via wired transmission (e.g., high-speed data transmission through cables or fiber optic channels of measurement-while-drilling (MWD / LWD) tools) or wireless transmission (e.g., mud pulses, acoustic waves, or newer electromagnetic telemetry). Under normal communication conditions, the downhole control unit operates according to surface commands; when communication is unreliable, it also has a local autopilot function, automatically adjusting itself according to preset logic for a period of time. It is worth noting that with the development of digital well technology, modern downhole tools can achieve high-bandwidth bidirectional communication and edge computing, making real-time monitoring and control possible.

[0054] Surface Monitoring and Decision-Making Module: The surface component includes a console / host and corresponding software system. The console receives real-time data streams from downhole and presents them to operators through a visual interface, including curves, instruments, and alarms. The software embeds intelligent decision-making algorithms to analyze the data: for example, identifying cutting patterns through big data models and comparing normal and abnormal states; using machine learning algorithms to predict potential risks (such as impending stuck drill bits) and provide advance warnings. Once abnormal signs are detected, the system can automatically adjust parameters or suggest manual intervention. This module also records all data throughout the entire operation process for post-operation analysis and continuous algorithm optimization. Operators can send control commands (such as adjusting rotation speed, changing cutter blade target pressure, starting and stopping operations, etc.) through the console to achieve remote control. This human-machine interaction design allows field engineers to easily monitor downhole dynamics and supervise and correct the intelligent system's decisions, forming a closed-loop human-machine collaborative operation mode.

[0055] Auxiliary support modules: To ensure reliable system operation, several auxiliary modules are also included. For example, the power module provides power to the downhole control unit and sensors (which can be supplied from the surface via cable or using downhole batteries / generators); the voltage stabilization and filtering module protects electronic components from downhole high-frequency vibrations and electromagnetic interference; the cooling system uses circulating fluid to remove heat and prevent overheating of electronics and motors; and the safety detachment module allows the cutter wings and body to separate when the tool is severely obstructed and cannot be retrieved (in extreme cases) to ensure the safe removal of the tubing from the wellbore.

[0056] In summary, the intelligent system module architecture of this invention is complete and tightly integrated, with each module performing its specific function while working collaboratively. The sensing module provides massive amounts of accurate data, the control and communication module ensures timely information transmission and precise command execution, the decision-making module endows the system with intelligent analysis and judgment capabilities, and the execution module ultimately implements the physical repair of the sleeve. This systematic design enables the milling method to possess…

[0057] The closed-loop function of "perception-analysis-action" means perceiving changes in the downhole environment, analyzing and deciding on the best operation, and then taking action.

[0058] Adjustable tools enable truly intelligent downhole operations.

[0059] Features of adaptability to complex well conditions

[0060] The retractable casing milling method of the present invention exhibits excellent adaptability and reliability in the face of various complex well conditions:

[0061] Operating on deformed well sections: For casing local deformations (bending, ellipticing, etc.) caused by formation movement, traditional rigid tools struggle to pass through or completely cut through the casing. In this method, the tool's outer diameter is significantly reduced after contraction, allowing it to smoothly pass through narrow deformed sections. Upon reaching the target location and deploying the cutting wings, intelligent force control gradually trims the deformed area, first contacting and grinding away the high points of the protruding areas, then gradually expanding until the circular diameter is restored. In this way, even if the casing experiences local bulging or collapse, it can be gradually cut in sections until the required diameter is achieved.

[0062] Uneven wear and eccentricity: Uneven wear in the wellbore means that the inner diameter of the casing is uneven along the circumference. The three-lobed blade structure of this invention ensures that it covers a nearly 360° range after unfolding, and the intelligent system adjusts the blades to balance the force on each side. If the force on a certain side is less (indicating that the gap is larger at that point), the system can appropriately increase the total feed to allow the blades to continue to expand until they contact the well wall on that side; conversely, if the force on a certain side is too great (indicating that there is a protrusion or hard spot at that point), the feed is slowed down and the focus is on grinding that side. By continuously monitoring and adjusting the force differences of each blade, the unevenly worn section can eventually be milled into a regular circular cross-section. This automatic adaptive capability ensures that a uniform cutting effect can still be obtained under eccentric well conditions.

[0063] Restricted duct diameter and debris blockage: For wells in long-term production, scale, deposits, or debris accumulation on the inner wall may reduce the duct diameter. This invention allows for passage through restricted areas with a small diameter before running into the well. Upon reaching the target, the cutter wings are deployed to mill away scale and obstacles. During milling, mud circulation is used to promptly remove debris and prevent further blockage. Even if an unusually large obstacle is encountered (such as debris stuck in the casing), the system's torque monitoring and obstruction detection functions will promptly detect it and attempt to clear the obstacle using small reciprocating motions or increased torque. If the obstacle cannot be cleared, the system will alert the operator to take special measures (such as supplementary retrieval operations) to avoid blindly pushing and causing a larger accident.

[0064] Safety assurance for high-risk well conditions:

[0065] The advantages of this method are even more pronounced in harsh well conditions such as high pressure, high temperature, or sulfur content. Real-time monitoring can detect abnormal pressure and temperature early, preventing well kicks or overheating failure of downhole tools; automatic control reduces safety hazards caused by human error. Especially in deep wells or high-sulfur gas wells, remote control can minimize personnel risks—operators do not need to manually operate on-site for extended periods; most work can be completed through the surface system, greatly improving safety.

[0066] Repeatability and Consistency: Due to the heavy reliance on automated program control, parameters and steps can be kept consistent each time this milling method is executed, ensuring consistent operational results across different well runs and sections. Compared to traditional operations that rely primarily on manual experience, this method is less affected by human factors, and performance parameters are predictable and results are repeatable during repeated operations. Furthermore, the modular and reusable design of the tools makes it possible to repeatedly run the tools to multiple locations within a single well, making it far more economical than disposable tools.

[0067] A retractable sleeve milling method specifically includes the following steps:

[0068] Step 1: Preparation and Running into the Well: Assemble the retractable milling tool on the surface and connect it to the lower end of the running-in tubing (such as drill collars or coiled tubing). Connect it to the power drive unit (drilling power rotary table or hydraulic motor) via the top connector. Check the status of all sensors and control modules, and pre-set the operating parameters in the surface control system (such as the target milling section depth, the length of casing to be milled, the maximum deployed diameter of the cutter wings, the maximum permissible contact pressure, and torque). Turn on the circulating mud pump to ensure the hollow passage of the tool is unobstructed. Then, slowly lower the tool into the well, using conventional depth sounding methods (such as sounding ropes, tubing length counting, or measurement while drilling data) to guide the tool to the target section. During this process, because the tool cutter wings are in the retracted state, the entire lowering process can smoothly pass through deformed or diameter-restricted casing sections without any jamming.

[0069] Step Two, Positioning and Centering: As the tool approaches the target casing section requiring milling, slow the descent speed and accurately determine the tool's position using downhole positioning methods. Well logging data (such as well inclination gauges or tubing tension changes) can be used to determine if the tool has reached the designated depth. If necessary, a directional joint or centralizer (if the tool is equipped) can be used to ensure the milling tool is properly centered within the casing. Once the surface control system confirms the tool's depth and attitude are correct based on sensor feedback, it commands the descent to stop.

[0070] Step 3, Blade Deployment: After positioning, initiate the milling tool deployment program. The ground operator issues the deployment command (or the tool automatically deploys at a pre-set trigger depth), and the power source drives the lead screw mechanism to move axially. As the lead screw advances, it gradually pushes the three blades outward.

[0071] Step 4, Intelligent Sensing and Control: During deployment, downhole force sensors monitor the contact force between the cutter blades and the casing inner wall in real time. When any cutter blade initially contacts the casing, the control system detects a sharp pressure increase inflection point. At this point, it automatically slows down or pauses deployment to avoid instantaneous overload impact on the well wall. Then, it slowly increases the deployment force to the predetermined wall-adhering pressure threshold, ensuring that the cutting teeth on the outer edge of the cutter blades press precisely against the casing inner wall. Through this adaptive adjustment, it ensures that all cutter blades smoothly adhere to the well wall, achieving uniform force distribution. If the casing exhibits eccentric wear or elliptical deformation, the system will detect uneven force distribution on each cutter blade. In this case, the control algorithm can find the optimal contact posture by slightly adjusting the lead screw position (or repeatedly deploying / retracting in small increments), thereby compensating for wellbore non-roundness and ensuring that all circumferential areas are covered and ground by the cutter blades. Once the cutter blades are successfully deployed to the working diameter and reach the required contact pressure, the system enters the milling operation preparation state.

[0072] Step 5, Milling Execution: After confirming that the cutter blades are fully deployed and making stable contact, start the rotary power to perform casing milling operations. Depending on the tool configuration, a surface turntable can be used to rotate the entire casing string, or a downhole hydraulic motor / electric motor can be used to drive the cutter blades to rotate and cut. During this process, the control system enters automatic adjustment closed-loop mode:

[0073] Step Six: Real-time Monitoring of Torque and Axial Load: The system continuously collects torque and propulsion data during cutter blade cutting. When torque and contact pressure are within safe ranges, the system mills normally according to preset speed and feed rate. If the downhole casing material changes or the cutting load increases, causing torque to rise, the system will automatically slow down the rotation speed or slightly retract the cutter blades to reduce cutting resistance; it will then return to the original settings after the resistance returns to normal.

[0074] When the system detects that the torque is approaching its upper limit or the tool is about to stall, it can autonomously reduce the pressure applied to the cutter wings or temporarily stop the advance to avoid jamming. In addition, the intelligent algorithm built into this method can autonomously identify tool jamming: if it detects that the milling head speed suddenly drops to zero (stops) or the torque rises sharply to a threshold, the system will immediately implement anti-jamming protection—automatically stop the rotation and reverse it slightly to loosen the cutter wings, and then resume forward rotation to continue milling, thus resolving the risk of jamming without timely manual intervention.

[0075] Step 7, Vibration and Stability Control: Attitude sensors are used to monitor vibration levels and tool eccentricity during high-speed rotation. If abnormal vibration occurs (potentially due to excessive force on one side or uneven cutting), the control system will adjust the rotation speed or blade pressure to reduce vibration. Simultaneously, active stabilization modules (such as the tool's built-in hydraulic dampers) can be activated to absorb excess vibration, protecting the tool and wellbore. If necessary, rotation can be paused to allow the system and wellbore environment to stabilize briefly before resuming operation.

[0076] Step 8: Temperature and Hydraulic Monitoring: If the tool has a built-in drive motor or hydraulic system, a temperature sensor monitors its operating temperature in real time. Once the temperature exceeds the safety threshold, the system will automatically pause the milling operation, allowing the mud to circulate and remove heat until the temperature returns to normal before resuming. Similarly, exceeding the hydraulic pressure limit will trigger a shutdown or depressurization operation to prevent system damage.

[0077] Step Nine, Communication and Remote Control: Throughout the milling process, downhole data is continuously transmitted to the surface via a communication link. Operators can view key parameters (torque, axial pressure, vibration, temperature, etc.) in real time on the control panel interface, as if observing downhole dynamics through a "digital dashboard." When the system's automatic adjustment cannot adequately handle special situations, operators can intervene via remote control commands, such as modifying the target torque threshold, adjusting the rotation speed, or lowering or raising the tool, thereby ensuring operational flexibility and safety margins.

[0078] With the support of intelligent control strategies, this step enables efficient and safe casing milling operations. The cutting diameter after the cutter wings are deployed can cover the entire inner diameter of the casing, achieving full circumferential removal. As the casing is gradually milled into chips, the drilling mud continuously circulates through the hollow channels inside the tool and the lateral chip removal holes, carrying the chips out of the wellbore. The milling length can be controlled by moving the tubing string up and down as needed—the system will slowly move the tool position within the target well section while milling, according to predetermined requirements, to remove a certain length of casing (e.g., several meters), creating sufficient space for subsequent installation of auxiliary casing.

[0079] Step 10, Blade Retraction: Once the expected milling depth is reached or the casing has been completely removed to achieve the operational objective, the rotational power is stopped and milling is completed. A blade retraction command is then issued, driving the lead screw mechanism to move in the opposite direction, retracting the three blades from their deployed state to a position flush against the tool body. Force sensors continue to monitor the retraction process to prevent sudden loosening or scraping: if a blade is stuck due to residual burrs, the system will detect an abnormal pressure change, pause retraction, and loosen the obstruction through micro-vibration or repeated small forward and backward movements, then continue retraction until fully closed. Retrieval can only proceed after confirming that the blades have retracted and the tool's outer diameter has returned to its initial downhole value.

[0080] Step 11: Wellbore Removal: Activate the mud circulation system to thoroughly clean the wellbore, removing any remaining cuttings. Then, slowly raise the tubing string to retrieve the tool from the well. When passing through previously deformed or narrow sections, the tool, now retracted to a smaller diameter, can pass safely without jamming. Finally, raise the tool to the surface, completing the milling operation. After returning to the surface, the tool can be inspected and maintained: due to its modular design, worn cutting teeth or blade components can be easily replaced or repaired. If necessary, the same tool or a backup tool can be lowered back in to repeat the milling process on other target sections of the well, thus achieving repeatable downhole casing repair operations.

[0081] Through the above-described control steps, the method of this invention can smoothly complete the entire process from downhole to milling and retrieval without direct human intervention. The steps are organically connected through pre-set programs and real-time monitoring, which improves operational efficiency and reduces the uncertainties of manual operation.

[0082] This method features a highly automated and intelligent control process, employing a closed-loop control strategy to dynamically adjust key aspects of the milling process, ensuring safety and efficiency under various operating conditions. Its control logic can be summarized as follows:

[0083] Initial setup and self-test:

[0084] Before the tool is lowered into the well, the system enters self-test mode to check all sensor readings and actuator status. If a fault is detected, the operation is halted and the operator is alerted. Once the tool has reached the target position, the system automatically switches to ready mode.

[0085] Deployment Control: Upon receiving the command to deploy the cutter wings, the control system drives the lead screw mechanism according to the preset deployment curve, while simultaneously monitoring the load on the cutter wings. The control flow includes a force feedback loop: continuously comparing the actual contact pressure with the target pressure. If the actual value is lower than the target and the increase is gradual, deployment continues; when the contact force approaches the preset threshold, the speed is slowed down until the target value is reached. This ensures that the cutter wings adhere to the well wall without generating excessive transient impact force. For complex well sections with varying well diameters, the control logic may adopt a step-by-step deployment—that is, deploying a small step and then pausing to allow the cutter wings to cut away local obstacles before continuing to the next step, gradually overcoming the deformation area.

[0086] Milling Process Control: Upon entering the formal milling stage, the system runs a multi-parameter coordinated control algorithm. Key control variables include rotational torque, blade propulsion force (equivalent to drill pressure), and vibration level. The system compares torque and propulsion force with predetermined safety limits and combines this with the drill speed change rate to determine the cutting state. When torque and drill pressure are detected to be stable within a reasonable range, the cutting is considered normal, and the current feed rate is maintained. If the torque gradually increases and approaches the upper limit, the algorithm triggers torque-drill pressure coordinated control, appropriately reducing the feed rate or slightly retracting the blades to reduce the depth of cut until the torque drops. Simultaneously, the drill speed is monitored; if the speed drops significantly (meaning potential resistance), the blade pressure is immediately reduced, and feed is paused if necessary to prevent further pressure application and potential jamming.

[0087] Anomaly detection and adaptation: Embedding various abnormal condition judgments into the control flow. For example:

[0088] Stuck drill detection:

[0089] The system detects tool jamming by detecting torque spikes and near-zero rotation speeds. Once jamming is detected, the system immediately executes its pre-planned procedure: it stops rotating and rotates in the opposite direction several times while retracting the cutter wings slightly to loosen the jamming point. Then, it resumes forward rotation and feed, automatically recovering from the jamming. The entire process requires no manual intervention, significantly reducing the risk of work interruptions due to tool jamming.

[0090] Vibration monitoring:

[0091] Real-time spectrum analysis of the accelerometer signal detects high-amplitude vibrations or flutter. The control system automatically adjusts the rotational speed (avoiding the resonant speed range) or temporarily slows the feed. Simultaneously, ground personnel are notified of the situation. If the vibration persists beyond acceptable limits and cannot be mitigated, the system enters safety mode and ceases operation.

[0092] Temperature protection:

[0093] The system continuously monitors the motor and hydraulic oil temperatures. If the temperature exceeds the limit, milling is paused and the cutter blade position is locked, allowing the slurry to circulate and cool. Operation automatically resumes once the temperature drops, thus preventing equipment damage due to overheating.

[0094] Communication interruption handling:

[0095] If communication between the well and the surface is unexpectedly interrupted, the tool will activate pre-set fail-safe logic. Typically, after a communication loss, the system will maintain its current state for a period of time. If communication is still not restored during this period, rotation will gradually stop and the cutter wings will retract, then the tool will wait for hoisting and recovery to prevent loss of control downhole.

[0096] Remote intervention and adjustment:

[0097] Despite the system's high degree of autonomy, ground engineers can still remotely intervene and adjust key parameters through the control interface. For example, when sensor data indicates abnormal casing material (leading to low cutting efficiency), engineers can remotely increase the upper limit of the blade contact pressure or adjust cutting parameters. Upon receiving the new parameters, the system will adjust the control target value accordingly and continue closed-loop control. This human-machine collaborative control method ensures the system's flexibility: under most normal circumstances, the automatic system performs optimized control, while in special or unforeseen situations, human intelligence can participate in decision-making, thus providing a "double insurance" to ensure operational success.

[0098] In summary, this invention achieves a new breakthrough in downhole casing repair through the ingenious combination of mechanical design and advanced intelligent control. The method details the entire process from downhole deployment to positioning, from cutter wing deployment to milling execution, and from automatic monitoring and adjustment to cutter wing retraction and withdrawal; each step demonstrates a high degree of automation and intelligence.

[0099] The core innovation lies in: using a screw-driven, three-lobed deployable cutter blade to solve the problems of limited diameter and insufficient cutting range in traditional tools; integrating automated adjustment and intelligent sensing technologies to monitor downhole conditions in real time and optimize control strategies; and enabling human-machine collaborative operation through remote control. This systematic solution is particularly suitable for complex well conditions such as casing deformation, uneven wear, and narrowed diameter, enabling efficient and safe milling of the casing portion and creating conditions for subsequent repair operations such as casing patching.

[0100] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall fall within the scope of the present invention.

Claims

1. A retractable sleeve milling tool, characterized in that, The tool includes a main body, a lead screw mechanism, a three-lobed blade, and a rotating shaft. The lead screw mechanism is mounted on the rotating shaft, which is axially installed inside the main body. Three support leg control elements are evenly distributed on the lead screw mechanism, and the movement of the lead screw mechanism drives the support leg control elements to extend and retract radially in the main body. The support leg control elements are hinged to the inner wall of the blade. The lead screw mechanism includes a cylindrical frame and three lead screw assemblies axially distributed on the outer wall of the cylindrical frame. Each lead screw assembly includes two linkage mechanisms, a lead screw, and a lead screw drive mechanism. The lead screw drive mechanism drives the lead screw to rotate. Each end of the lead screw is provided with a slider. The linkage mechanisms are respectively hinged to the sliders, the support leg control element, and the outer wall of the cylindrical frame. The sliders move axially on the lead screw, causing the support leg control element to extend and retract radially. It also includes an intelligent system, comprising a downhole execution module, a downhole sensing and measurement module, a downhole control and communication module, a surface monitoring and decision-making module, and an auxiliary support module. The downhole sensing and measurement module includes force sensors, torque sensors, accelerometers and gyroscopes, pressure sensors, temperature sensors, and position / displacement sensors. The downhole control and communication module includes a compact downhole control unit for on-site processing of sensor data and execution of control commands. The surface monitoring and decision-making module includes a console / host and corresponding software system. The console receives real-time data streams from downhole and presents them to the operator through a visual interface. The software embeds intelligent decision-making algorithms to analyze the data. This module also records all data throughout the entire operation process for post-operation analysis and continuous algorithm optimization. The downhole execution module ultimately performs the physical repair of the casing. The blade is a spiral blade, and the three-lobed spiral blade forms a cylinder when it contracts. The force sensing device is used to monitor the contact pressure between the blade and the inner wall of the casing in real time and to feed the pressure data back to the ground control system.

2. The retractable sleeve milling tool according to claim 1, characterized in that, There is a helical gap between two adjacent helical carbide cutting tools, which is used for chip removal.

3. The retractable sleeve milling tool according to claim 1, characterized in that, The outer wall of the blade is provided with a spiral cemented carbide blade.

4. A retractable sleeve milling tool according to claim 3, characterized in that, The outer wall of the spiral cemented carbide insert is provided with several cutting teeth.

5. A retractable sleeve milling tool according to claim 1, characterized in that, The two sliders move outward or inward simultaneously on the lead screw.

6. A retractable sleeve milling tool according to claim 1, characterized in that, The tool body has several fixed rods evenly distributed axially on its inner wall, and the rotating shaft is located in the receiving cavity formed by the axial direction of the fixed rods.

7. A method for milling and grinding retractable sleeves, characterized in that, This method uses a retractable sleeve milling tool as described in any one of claims 1-6 for milling, and specifically includes the following steps: Step 1: Preparation and Running into the Well: Assemble the retractable milling tool on the surface and connect it to the lower end of the running tubing string. Connect the retractable casing milling tool to the power drive unit. Turn on the circulating mud pump and ensure that the hollow passage of the tool is unobstructed. Then slowly lower the tool into the well and use conventional depth sounding methods to move the tool to the target well section. Step 2, Positioning and Alignment: When the tool is lowered close to the section of the target casing that needs to be milled, the lowering speed is slowed down and the tool position is accurately determined using downhole positioning methods; logging data is used to determine whether the tool has reached the designated depth; after the surface control system confirms that the tool's depth and attitude are correct based on sensor feedback, it commands the lowering to stop. Step 3, Blade Deployment: After positioning, start the milling tool deployment program; the ground operator issues the deployment command, and the power source drives the lead screw mechanism to move; as the lead screw advances, the support leg control element gradually pushes the three blades outward. Step 4, Milling Execution: After confirming that the cutter blades are fully deployed and making stable contact, start the rotary power to perform casing milling operations; depending on the tool configuration, use a surface turntable to drive the entire casing string to rotate, or use a downhole hydraulic motor / electric motor to drive the cutter blades to rotate and cut; during this process, the control system enters automatic adjustment closed-loop mode: Step 5, Vibration and Stability Control: The attitude sensor monitors the vibration level and tool eccentricity during high-speed rotation; if abnormal vibration occurs, the control system will adjust the rotation speed or blade pressure to reduce the vibration. Step 6, Blade Retraction: Once the expected milling depth is reached or the sleeve has been completely removed and the work objective is achieved, stop the rotational power and end the milling process; then issue a blade retraction command to drive the lead screw mechanism to move in the opposite direction, retracting the three blades from the deployed state to a position close to the tool body; Step 7: Remove the wellbore: Start the mud circulation to thoroughly clean the wellbore and wash away any remaining cuttings; then slowly lift the tubing string to remove the tool from the well; when passing through previously deformed or narrow well sections, the tool can pass safely without getting stuck because it has shrunk to a small diameter; finally, lift the tool to the surface, and the entire milling operation is complete.

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