An eccentric micro-reaming assembly tool for horizontal wells

Abstract

The application discloses an eccentric micro-expanding tool for a horizontal well and relates to the technical field of downhole tools for oil drilling. The tool comprises a roller centralizing section, an eccentric micro-expanding section and a guide section which are sequentially connected. A throttling nozzle is fixed in the center flow channel of the eccentric micro-expanding section. An annular piston and a return spring are arranged between the mandrel and the outer cylinder. The upstream and downstream pressures of the throttling nozzle are respectively introduced to the two end faces of the annular piston through the communication hole and the balance hole on the mandrel. The differential pressure overcomes the pre-tightening force of the spring and pushes the cutting seat on one side of the outer cylinder radially through the driving slope. The outer end arc-shaped cutter plate of the cutting seat scrapes the well wall on one side, and the stroke of the cutting seat is limited by the limiting ring to limit the unilateral micro-expanding amount. Two rows of supporting rollers on the opposite side of the circumference bear the cutting reaction force and press the well wall on the opposite side to form a rolling support reference. When the pressure is lost, the spring forcibly recovers the cutting seat through the bidirectional linkage assembly. The tool is used for modifying the step, keyway and reduced diameter before casing in the horizontal well, which is beneficial to reducing the casing friction and improving the consistency of the well diameter.

Description

Technical Field

[0001] This invention relates to the field of downhole tools technology for oil drilling, specifically an eccentric micro-reamer assembly tool for horizontal wells. Background Technology

[0002] Unconventional oil and gas reservoirs such as shale gas are commonly developed using horizontal wells. After the completion of horizontal wells or highly deviated wells and before casing is run, the open hole section often contains steps at azimuth changes, keyways in directional sections, cuttings beds on the lower edge of horizontal sections, and localized narrowing caused by mud cake accumulation. Taking a sidetracked horizontal well with a 215.9 mm borehole and 139.7 mm casing as an example, the casing string repeatedly encounters obstruction in such sections, often requiring multiple attempts to pull, impact, and even retrieve the entire casing for re-running. Each casing run is time-consuming, and repeated impacts can easily damage the casing threads and wellbore. The direct cause of these obstructions is the presence of steps, edges, and narrowings that extend above the borehole envelope in the open hole section. Effectively addressing these features before casing run is a prerequisite for ensuring successful casing installation.

[0003] Existing downhole tools for wellbore finishing or enlargement mainly fall into the following categories, representing existing technological approaches. The first category is hydraulic telescopic reamers. CN223190373U discloses a hydraulically remotely controlled variable-diameter eccentric reamer, which uses hydraulic control to achieve cutter diameter change and eccentric reaming action. The cutting part is supported by two side support arms and moves outwards as a whole. These concentric hydraulic reamers typically employ symmetrically arranged two- or three-wing cutters, pushed out by a pump. Their design goal is a large reaming volume. When used for wellbore finishing before casing in horizontal wells, the reaming volume is too large, easily disrupting the smoothness of the drilled wellbore trajectory. The symmetrical cutters rely on drill string rigidity to maintain concentricity under shallow cutting depth conditions, resulting in uneven cutting depth between the two wings, easily inducing drill string vibration and wellbore spiralization, leading to high reaming torque and energy consumption. The second category consists of localized finishing tools with fixed outer diameters, such as fixed eccentric reaming joints or keyway expanders. Their outer diameter is fixed, and they cannot be retrieved after insertion into the well, making it difficult to access smaller open-hole sections through the upper casing. Furthermore, their finishing capabilities are mostly limited to localized defects like keyways, lacking a systematic finishing effect on steps, narrowing, and cuttings beds throughout the entire well. The third category comprises passive drag reduction or guiding tools, such as roller centralizers and hydraulic rotary guide shoes. Their main function is to reduce friction or overcome obstacles by rotating the crown. They lack the ability to actively cut and finish already formed steps and keyways, requiring repeated reaming and impacting with the tubing string after encountering obstruction.

[0004] The aforementioned existing technologies, which employ hydraulic deployment of symmetrical blades for concentric reaming, fixed-diameter structures for localized finishing, or passive drag reduction via rolling, still have certain limitations in wellbore finishing scenarios before casing in horizontal wells. Concentric hydraulic reamers exhibit uneven depth cutting, significant torque vibration, and reliance on drill string rigidity for centering during small-depth, equal-volume finishing; fixed-diameter localized finishing tools cannot be retrieved after insertion, resulting in poor maneuverability and limited finishing coverage; passive drag reduction tools lack active cutting capabilities. These limitations make it difficult to simultaneously achieve active micro-finishing, post-reaming diameter consistency, maneuverability, and tripping safety in a single wellbore operation.

[0005] Therefore, how to proactively, minimally, and equally modify the wellbore steps, keyways, cuttings beds, and local diameter reductions in the open hole section of horizontal wells, and how to control their retraction during pump shutdown and pressure loss to ensure passability and tripping safety, thereby reducing the number of times casing is obstructed and the time of repeated pulling and impacting, has become a technical problem that needs to be solved in the pre-casing operation of horizontal wells. Summary of the Invention

[0006] To address the problems of existing wellbore trimming or enlargement tools used in horizontal wells before casing operation, such as uneven depth of cut of concentric hydraulic reamers under shallow cutting depths, reliance on drill string rigidity to maintain concentricity, and significant reaming torque and vibration, fixed-diameter local trimming tools being non-adjustable and non-retrievable after insertion, limited trimming coverage, and passive drag reduction tools lacking active cutting capabilities, making it difficult to simultaneously address the issues of active micro-scale trimming of steps, keyways, cuttings beds, and local diameter reductions, ensuring consistent enlarged diameter, passability, and tripping safety in the same operation, this invention provides an eccentric micro-reamer combination tool for horizontal wells.

[0007] The overall concept of this invention is to place the cutting action and slewing support required for wellbore trimming on both sides of the tool body diameter. This allows the radial reaction force generated by unilateral cutting to be absorbed by the rolling support on the opposite side. The trimmed wellbore itself serves as the slewing reference surface; the greater the cutting resistance, the tighter the clamping at that point. This eliminates the dependence of concentric reaming on drill string rigidity for centering and allows the slewing trajectory of small-depth trimming to be constrained by the wellbore itself. To enable controlled extension and retraction of the unilateral cutting, the tool uses drilling fluid pump pressure as its power source. Two throttling nozzles are connected in series in the central flow channel. The upstream pressure of the upstream nozzle and the pressure in the intermediate cavity between the two nozzles are respectively directed to the two end faces of the annular piston. This ensures that the pressure difference of the driving piston is always equal to the upstream and downstream pressure difference of the upstream nozzle itself. The activation pressure is therefore determined only by the nozzle orifice diameter and displacement, and can be taken within a narrow window lower than the working pressure difference of other hydraulic tools in the same drill string. This facilitates activation by increasing the displacement and suppresses false activation. Under the pressure differential, the piston moves axially and, via a drive ramp with a locking angle, radially pushes the cutting seat out. Its stroke endpoint is rigidly limited by a limiting ring and converted into a constant unilateral micro-expansion. During cutting, the axial component of the wellbore reaction force generated by the ramp is insufficient to push the piston back. The cutting depth is maintained by the pump pressure holding force and the ramp's self-locking mechanism. When the pump stops and pressure is lost, the return spring, via a bidirectional linkage structure on the ramp, forcibly retracts the cutting seat in a positive direction, restoring the tool to its original shape. Therefore, maintaining the cutting depth and forced retraction do not conflict. To facilitate surface monitoring of the tool's status, when the piston reaches its stroke endpoint, a diversion path bypassing the downstream nozzle is opened. The flow rate through the downstream nozzle decreases accordingly, resulting in a discernible step-like drop in riser pressure. The upstream nozzle always carries all drilling fluid, and the pressure differential driving the piston is unaffected by this indication. All components work together using a purely mechanical-hydraulic system. Activation, limiting, support, retraction, and position indication are interconnected without interference, collectively forming an eccentric micro-expansion structure capable of active micro-adjustment and controlled retraction.

[0008] To achieve the above objectives, the present invention adopts the following technical solution. An eccentric micro-reamer assembly tool for horizontal wells includes an upper connector, an eccentric micro-reamer joint, and a lower connector connected in sequence. The eccentric micro-reamer joint consists of a mandrel and an outer cylinder fixedly fitted to it. A throttling nozzle is fixed in the central flow channel inside the mandrel. A ring piston and a return spring that applies a reset preload force are slidably sealed between the mandrel and the outer cylinder. A connecting hole and a balance hole are provided on the mandrel. The connecting hole leads the drilling fluid pressure upstream of the throttling nozzle to one end face of the ring piston, and the balance hole leads the drilling fluid pressure downstream of the throttling nozzle to the other end face of the ring piston, so that the pressure difference between the upstream and downstream of the throttling nozzle acts on both ends of the piston. A radially penetrating guide window is provided on only one side of the outer cylinder. A cutting seat is slidably mounted inside the guide window. An arc-shaped cutter plate is provided at the outer end of the cutting seat. A driving inclined surface is provided on the ring piston, and a bidirectional linkage assembly is provided between the driving inclined surface and the cutting seat. When the pressure difference between the upstream and downstream of the throttling nozzle overcomes the preload of the return spring, the piston moves axially and radially pushes the cutting seat out via the drive ramp. When the pressure difference disappears, the return spring drives the piston back and forcibly pulls the cutting seat radially back via the bidirectional linkage assembly. A limiting ring is installed inside the eccentric micro-expanding nozzle, and a limiting shoulder is provided on the piston. The piston moves until the limiting shoulder abuts against the limiting ring, and its axial stroke is calculated by the drive ramp to rigidly limit the radial extension of the cutting seat on one side. Two rows of support rollers are arranged axially at intervals at a position 180 degrees circumferentially opposite to the cutting seat on the outer cylinder. The axial span of the two rows of support rollers covers the axial length of the cutting seat and rolls in contact with the well wall. The radial reaction force generated by the cutting seat cutting the well wall is transmitted to the support rollers through the outer cylinder, causing the support rollers to press against the well wall on the opposite side of the cutting seat to form a rolling support reference.

[0009] Furthermore, the bidirectional linkage assembly consists of a T-shaped groove on the drive ramp and a T-shaped boss at the bottom of the cutting seat. The T-shaped boss slides into the T-shaped groove, and when the piston returns, the two work together to apply a radial pull force to the cutting seat, so that the retraction of the cutting seat is rigidly constrained by the piston stroke.

[0010] Furthermore, the eccentric micro-expanding joint also includes a return spring bracket threaded onto the mandrel. The return spring is a disc spring assembly supported by this bracket. The preload of the disc spring assembly is adjusted by adjusting the thread position of the return spring bracket on the mandrel, so that the activation pressure difference of the piston is in the range of 1.5 MPa to 2.5 MPa and lower than the working pressure difference of other matching hydraulic tools in the same drill string. The limit ring is threadedly connected to the return spring bracket. The end position of the piston stroke is limited by the thread position of the limit ring on the return spring bracket. The radial extension of the cutting seat on one side, calculated by the drive inclined plane, is 3 mm to 6 mm. Adjusting the limit ring does not change the position of the return spring bracket or the preload of the disc spring assembly.

[0011] Furthermore, the curved blade is a replaceable blade inlaid with cemented carbide. It is embedded in the dovetail groove at the outer end of the cutting seat and positioned by a locating pin and locked by a locking screw. An anti-drop step is provided between the root of the curved blade and the cutting seat to prevent the curved blade from falling out of the cutting seat when the locking screw fails.

[0012] Furthermore, the support roller is a drum-shaped roller and is supported in the roller groove of the outer cylinder by the roller shaft. Its generatrix protrudes from the outer circular surface of the outer cylinder. The inner hole of the support roller is provided with an anti-fall step to stop the support roller from falling out of the roller groove when the roller shaft breaks.

[0013] Furthermore, a second throttling nozzle is fixed downstream of the central flow channel, forming an intermediate cavity between the throttling nozzle and the second throttling nozzle. The balance hole takes pressure from this intermediate cavity. The annular piston sidewall is provided with a flow passage hole, the spindle is provided with a bypass hole connecting to the intermediate cavity, and the root of the cutting seat is provided with an indicator water eye. When the piston reaches the end of its stroke, the flow passage hole and the bypass hole are aligned and connected. A portion of the drilling fluid in the intermediate cavity bypasses the second throttling nozzle and is ejected from the root of the cutter plate through the indicator water eye. The remaining drilling fluid continues to flow downward through the second throttling nozzle. The reduced flow rate through the second throttling nozzle causes its pressure differential to decrease, and the pressure on the surface riser decreases in a step-like manner to indicate that the cutting seat has extended to the correct position. Meanwhile, the throttling nozzle always passes through all the drilling fluid, so that the pressure differential driving the piston is not affected.

[0014] Furthermore, the eccentric micro-reamer assembly tool also includes a guide joint connecting the eccentric micro-reamer section and the lower connector. The outer surface of the guide joint has a spiral groove as an upward return channel for drilling fluid and cuttings, and the lower end of the guide joint is provided with a tapered guide head that connects to the lower connector.

[0015] Furthermore, the eccentric micro-expanding eye assembly tool also includes a roller straightening section connected between the upper connector and the eccentric micro-expanding eye section. The roller straightening section includes a straightening section body and three rows of straightening rollers evenly distributed along the circumference of the straightening section body. The inner hole of the straightening roller is provided with an anti-fall step.

[0016] Furthermore, the eccentric micro-reamer assembly tool is connected to the wellbore string before the horizontal downhole casing. The outer diameter of the outer cylinder, the radial protrusion of the support roller, and the radial protrusion of the arc-shaped cutter plate when the cutting seat is in the maximum extension position together constitute the cutting envelope diameter. This cutting envelope diameter is three to six millimeters larger than the diameter of the wellbore to be repaired.

[0017] Furthermore, the heave angle of the driving ramp is a self-locking angle. Under the radial reaction force of the cutting well wall, the axial component force generated by the driving ramp on the piston is insufficient to push the piston back, so that the cutting seat remains in the extended position limited by the limit ring during the cutting process. When the return spring drives the piston back, the radial pull of the cutting seat through the bidirectional linkage assembly is not affected by this self-locking.

[0018] The beneficial effects of this invention are: The eccentric micro-reamer has its cutting seat located on one side of the outer cylinder's circumference, with two rows of support rollers positioned 180 degrees circumferentially opposite each other. This changes the approach of concentric hydraulic reamers, which rely on symmetrical blades to balance cutting reaction forces and depend on drill string stiffness for concentricity. The radial reaction force generated by unilateral scraping is transmitted through the outer cylinder to the opposite support rollers. The wellbore being trimmed acts as a rotation reference surface. As cutting resistance increases, the clamping force at this point increases synchronously, and the reference stiffness adaptively increases with the load. Therefore, the rotation trajectory throughout the small-depth trimming process is constrained by the wellbore itself. Compared to the situation where symmetrical blades exacerbate vibration due to uneven blade depth at small depths, this force-closed structure helps suppress chatter and improves the stability of the trimming process.

[0019] A connecting hole and a balancing hole are respectively set on the mandrel. The upstream pressure of the throttling nozzle is led to one end face of the annular piston, and the pressure in the intermediate cavity between the two nozzles is led to the other end face, so that the driving pressure difference acting on the piston is always equal to the upstream and downstream pressure difference of the throttling nozzle itself. Since this pressure difference is determined only by the orifice diameter and displacement of the throttling nozzle, the activation pressure difference can be taken within a narrow window that is lower than the working pressure difference of other hydraulic tools in the same drill string. This facilitates controlled activation by increasing the displacement and improves the suppression of false activation under normal circulating displacement. The balancing hole draws pressure from the intermediate cavity rather than the annulus, so that the pressure introduced into both ends of the piston changes synchronously and the difference remains constant when the indicator bypass is opened. This helps that the position indication action does not interfere with the extension and holding of the cutting seat.

[0020] The unilateral radial extension is rigidly limited by the limiting ring and calculated by converting the axial stroke of the annular piston through the driving inclined surface, overcoming the limitations of fixed outer diameter local dressing tools that are not adjustable or retractable after entering the well. The cutting seat extends until the limiting shoulder abuts against the limiting ring, and its extension is determined by the thickness and thread position of the selected limiting ring, independent of pump pressure or displacement fluctuations. Combined with the wellbore self-reference, this mechanically constrains the enlarged diameter of the wellbore after dressing. This rigid limiting relationship helps to stably control the unilateral micro-enlargement within the designed range of three to six millimeters and improves the consistency of the enlarged diameter throughout the well section, thus providing more favorable conditions for casing centering and uniform cementing annulus.

[0021] The driving ramp is based on the locking angle, ensuring that the radial reaction force from the well wall on the arc-shaped cutter plate during cutting, through the axial component generated by the ramp, is insufficient to push the annular piston back. The depth of cut remains constant at the limit position throughout the reaming process, supported by the pump pressure holding force and the ramp's self-locking mechanism. Recovery upon pump shutdown and pressure loss is achieved through a return spring's positive axial traction on the cutting seat via a bidirectional linkage assembly, independent of the ramp's reverse self-locking. This coordination ensures that maintaining the depth of cut during cutting and the forced recovery upon pressure loss do not conflict, helping to maintain a constant depth of cut while preserving reliable recovery capability.

[0022] When encountering jamming or an abnormal increase in torque, the pump stops and pressure is lost. The return spring, via the T-shaped hook of the bidirectional linkage assembly, pulls the T-shaped boss to forcibly pull back the cutting seat, and the tool returns to its cylindrical shape. This improves the handling method where the symmetrical cutter wing expander still requires repeated pulling and impacting with the tubing string after encountering obstruction. The anti-fall step at the root of the arc-shaped cutter plate stops the cutter plate when the locking screw fails, and the anti-fall step in the inner hole of the support roller stops the roller when the roller shaft breaks. Furthermore, the blockage of the indicator water eye by rock cuttings does not affect the return stroke of the annular piston, making the recovery function and the indicator function independent. These degradation recovery capabilities inherent in the structure itself help improve operational safety under abnormal conditions and reduce the risk of the arc-shaped cutter plate and support roller becoming downhole objects.

[0023] When the annular piston reaches the end of its stroke, its sidewall flow hole aligns and connects with the mandrel bypass hole. A portion of the drilling fluid in the intermediate chamber bypasses the second throttling nozzle and exits from the cutterhead root through the indicator water eye. The flow rate through the second throttling nozzle decreases due to the flow diversion, and the pressure difference across its two ends decreases accordingly, resulting in a measurable step-like drop in the surface riser pressure. Compared to operating methods that lack position feedback and rely on experience to determine whether the cutting seat has extended, this flow diversion structure provides an observable pressure signal for the surface to determine whether the tool has entered the cutting state. This position indication helps the surface driller determine the reaming footage and cycle time, thereby improving the controllability of the operation.

[0024] The tool is assembled in three sections: an upper roller centralizing section, a middle eccentric micro-expanding section, and a lower guide section, connected sequentially with API threads. The centralizing section provides full-circumference centering and rolling drag reduction, while the guide section's helical grooves handle the upward flow of cuttings and create a vortex during cementing. The tapered guide head guides the tool gradually over steps and diameter reductions. All activation, limiting, retrieval, and indication actions are completed by a purely mechanical hydraulic structure without electronic components. Its activation differential pressure window and interface are compatible with existing roller centralizers, hydraulic rotary guide shoes, and other tools. This assembly method allows for direct integration of this tool into existing wellbore cleaning and casing running strings, providing more favorable engineering feasibility for combining wellbore trimming, drag reduction, and cuttings removal in a single operation. Attached Figure Description

[0025] Figure 1 This is an exploded view of the entire invention; Figure 2 The local explosion of the present invention Figure 1 ; Figure 3 The local explosion of the present invention Figure 2 ; Figure 4 This is a front view of the present invention; Figure 5 For the present invention Figure 4 Sectional view of AA; Figure 6 For the present invention Figure 5 Enlarged view at point B in the middle; Figure 7 This is a schematic diagram illustrating the use of the present invention; Figure 8 The appearance structure of the present invention Figure 1 ; Figure 9 The appearance structure of the present invention Figure 2 ; Figure 10 This is a flowchart of the process of the present invention.

[0026] Explanation of the labels in the diagram 1. Eccentric micro-expanding eyelet; 2. Mandrel; 3. Outer cylinder; 4. Central flow channel; 5. Throttling nozzle; 6. Annular piston; 7. Return spring; 8. Guide window; 9. Cutting seat; 10. Arc-shaped blade; 11. Drive inclined surface; 12. Bidirectional linkage assembly; 13. Limiting ring; 14. Limiting shoulder; 15. Support roller; 16. T-shaped groove; 17. T-shaped boss; 18. Locking screw; 19. Flow hole; 20. Bypass hole; 21. Indicating water eye; 22. Guide joint; 23. Spiral groove; 24. Conical guide head; 25. Roller straightening joint; 26. Straightening joint body; 27. Straightening roller; 28. Return spring bracket; 29. ​​Second throttling nozzle; 30. Connecting hole; 31. Balance hole. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0028] It should be noted that the directional concepts of "left", "right", "up", "down", "front", "back", "inner", and "outer" in the following scheme are all relative directions, and will not be listed one by one here.

[0029] See Figures 1 to 10 .

[0030] Example 1 This embodiment provides a complete implementation of the eccentric micro-reamer assembly tool for horizontal wells. The tool is slender and cylindrical, and is constructed axially from top to bottom by an upper connector, a roller centralizing section 25, an eccentric micro-reamer section 1, a guide section 22, and a lower connector, all connected by API threads. The API internal thread at the upper end of the upper connector connects to the upper drill string, and the API external thread at the lower end of the lower connector is used to connect a hydraulic rotary guide shoe or other downhole tools downwards. The drilling fluid channels inside each section are aligned and continuously connected. All movements are completed by a purely mechanical hydraulic structure without any electronic components. The eccentric micro-reamer section 1 carries the core function of unilateral micro-dressing, and its structural composition and operation process constitute the focus of this embodiment. The roller centralizing section 25 and the guide section 22 in this embodiment serve as auxiliary functions for centering the drill string, reducing drag, and guiding cuttings removal.

[0031] The eccentric micro-expanding eyelet 1 is a double-layer cylindrical structure with the mandrel 2 and outer cylinder 3 coaxially nested. The outer cylinder 3 is threadedly fixed to the outside of the mandrel 2, ensuring that their circumferential and axial positions remain constant. A central flow channel 4 runs through the interior of the mandrel 2 along its axis. A throttling nozzle 5 and a second throttling nozzle 29 are sequentially fixed along the axial direction within the central flow channel 4. Both the throttling nozzle 5 and the second throttling nozzle 29 are annular throttling components with a constriction throat, fixed by threads or welding. A section of the central flow channel between them forms an intermediate cavity. An annular cavity is formed between the outer surface of the mandrel 2 and the inner hole of the outer cylinder 3. An annular piston 6 is slidably sealed within this cavity. Piston ring seals are provided between the inner circumference of the annular piston 6 and the outer circle of the mandrel 2, and between the outer circumference of the annular piston 6 and the inner hole of the outer cylinder 3, separating the cavity on the upper end face of the annular piston 6 from the spring cavity on its lower end face. The mandrel 2 has a connecting hole 30 and a balancing hole 31 on its wall. The connecting hole 30 connects the central flow channel 4 upstream of the throttling nozzle 5 to the cavity on one side of the upper end face of the annular piston 6, thus drawing the drilling fluid pressure upstream of the throttling nozzle 5 to the upper end face of the annular piston 6. The balancing hole 31 connects the intermediate cavity to the spring cavity on one side of the lower end face of the annular piston 6, thus drawing the pressure of the intermediate cavity between the throttling nozzle 5 and the second throttling nozzle 29, i.e., immediately downstream of the throttling nozzle 5, to the lower end face of the annular piston 6. With this arrangement, the upper and lower end faces of the annular piston 6 bear the upstream and downstream pressures of the throttling nozzle 5, respectively. The net driving pressure difference acting on the two end faces of the annular piston 6 is always equal to the upstream and downstream pressure difference of the throttling nozzle 5 itself, and is independent of the flow state of the second throttling nozzle 29 and its downstream.

[0032] The lower end face of the annular piston 6 abuts against the upper end of the return spring 7. The return spring 7 is a multi-layered or assembled disc spring assembly, and its lower end is supported by the return spring bracket 28. The return spring bracket 28 is threadedly mounted on the outer wall of the mandrel 2. Adjusting the thread position of the return spring bracket 28 on the mandrel 2 changes the compression of the disc spring assembly, thereby adjusting the return preload force applied by the return spring 7 to the annular piston 6. The activation pressure difference corresponding to this preload force is in the range of 1.5 MPa to 2.5 MPa and is lower than the working pressure difference of other matching hydraulic tools in the same drill string. The limiting ring 13 is a replaceable annular part and is threadedly mounted on the return spring bracket 28. It is located at the end position of the stroke of the annular piston 6 in the pushing direction. The lower outer periphery of the annular piston 6 is provided with a limiting shoulder 14 corresponding to the limiting ring 13. The lower section of the annular piston 6 is also provided with a driving inclined surface 11. The outer cylinder 3 has a guide window 8 that extends radially and axially on only one side. A cutting seat 9 is radially slidably mounted inside the guide window 8. The bottom of the cutting seat 9 has an inclined surface that mates with the driving inclined surface 11. A bidirectional linkage assembly 12 is provided between the driving inclined surface 11 and the cutting seat 9. The bidirectional linkage assembly 12 consists of a T-shaped groove 16 on the driving inclined surface 11 and a T-shaped boss 17 at the bottom of the cutting seat 9. The T-shaped boss 17 slides within the T-shaped groove 16, allowing the cutting seat 9 to slide relative to the driving inclined surface 11 while simultaneously engaging with it in a traction direction perpendicular to the inclined surface. The lift angle of the driving inclined surface 11 is a self-locking angle. The outer end face of the cutting seat 9 is convex arc-shaped, and a replaceable inlaid carbide arc-shaped cutter plate 10 is embedded in the arc-shaped surface through a dovetail groove. The arc-shaped cutter plate 10 is positioned axially by a positioning pin and locked by a locking screw 18. A cutter plate anti-drop step is provided between the root of the arc-shaped cutter plate 10 and the cutting seat 9.

[0033] Two rows of roller grooves are axially spaced approximately 180 degrees apart from the guide window 8 on the outer cylinder 3. Each row of roller grooves contains a support roller 15 supported by a roller shaft. The support roller 15 is a drum-shaped roller with its generatrix protruding from the outer surface of the outer cylinder 3 and able to rotate freely around the roller shaft. The axial span of the two rows of support rollers 15 covers the axial length of the cutting seat 9. The inner hole of the support roller 15 is provided with a roller anti-fall step. The root of the cutting seat 9 is provided with an indicator water eye 21, the side wall of the annular piston 6 is provided with a flow hole 19, and the spindle 2 is provided with a bypass hole 20 communicating with the intermediate cavity. The inlet of the indicator water eye 21 leads through the root of the cutting seat 9 to the root area of ​​the arc-shaped blade 10, and the outlet faces the root of the arc-shaped blade 10.

[0034] The working process of this tool is as follows: when the tubing string is not pumped or is circulating at a small displacement, the pressure difference established at both ends of the throttle nozzle 5 is insufficient to overcome the preload force of the return spring 7. The annular piston 6 stops at the return position under the action of the return spring 7, the cutting seat 9 retracts into the outline of the outer cylinder 3, and the tool passes through the upper casing and complex well sections in a cylindrical shape. The support roller 15 and the straightening roller convert sliding friction into rolling friction to reduce the lowering resistance. After the tubing reaches the section of well to be repaired, the flow rate is increased to the design value. The upstream pressure of the throttle nozzle 5 acts on the upper end face of the annular piston 6 through the connecting hole 30, and the intermediate cavity pressure acts on the lower end face of the annular piston 6 through the balance hole 31. The difference between the two exceeds the preload of the return spring 7. The annular piston 6 moves axially in the pushing direction. The driving inclined surface 11 pushes the cutting seat 9 to extend radially outward along the guide window 8 until the limiting shoulder 14 abuts against the limiting ring 13 mounted on the return spring bracket 28 and stops. This axial stroke of the annular piston 6 is converted into a constant single-sided radial extension of the cutting seat 9 by the driving inclined surface 11. This extension is limited by the thickness and thread position of the selected limiting ring 13 and is between 3 mm and 6 mm. The pipe string is then rotated and slowly lowered or raised. The arc-shaped blade 10 scrapes the steps, keyway edges, and reduced diameter sections that are enclosed by the support rollers 15 on one side. The radial reaction force generated by the cutting is transmitted through the cutting seat 9 to the outer cylinder 3, and then to the two rows of support rollers 15 located at approximately 180 degrees to each other in the circumferential direction. The support rollers 15 are pressed against the well wall on the opposite side of the cutting seat 9 to form a rolling support reference. The greater the cutting resistance, the greater the clamping force at that point. The extension position of the cutting seat 9 is rigidly constrained by the limiting ring 13 to keep the cutting depth constant. When the annular piston 6 moves to the end of its stroke, the flow hole 19 on its sidewall aligns and connects with the bypass hole 20 on the spindle 2. A portion of the drilling fluid in the intermediate cavity enters the indicator water eye 21 through the bypass hole 20 and the flow hole 19 and is ejected from the root of the arc-shaped cutter 10, flushing the arc-shaped cutter 10 and the cuttings. The remaining drilling fluid continues to flow down to the lower drill string through the second throttling nozzle 29. The flow rate through the second throttling nozzle 29 decreases due to the diversion, and the pressure difference between its two ends decreases accordingly. The surface riser pressure shows a readable step-like decrease, serving as a feedback signal that the cutting seat 9 has extended to the correct position. During this process, the throttling nozzle 5 always passes through all the drilling fluid, and the driving pressure difference acting on the two ends of the annular piston 6 is not affected by this indicator action. The adjusted equal-diameter micro-reamed borehole allows for the low-resistance running of the subsequent casing string and improves the uniformity of the cementing annulus. The riser pressure step signal allows the surface driller to judge the working status of the tool and determine the reaming footage and circulation time accordingly. After the pump stops or the displacement is reduced, the pressure difference across the throttling nozzle 5 disappears, the return spring 7 drives the annular piston 6 to return, the T-shaped slide 16 hooks the T-shaped boss 17, and forcibly pulls the cutting seat 9 radially back into the guide window 8. The tool returns to its cylindrical shape and can be directly pulled up or lowered further. Any abnormal situations during tool operation are degraded and restored by the structure itself according to the predetermined priority.The primary and highest priority safety action is forced recovery due to pressure loss. Its triggering condition is when the surface detects an abnormal increase in the reaming torque or suspended weight, or when it is necessary to actively release the cutting jamming point, the pump is stopped or the flow rate is reduced. The reference for the detection is the step amount of the riser pressure at the time of activation relative to the normal circulating pressure of the well section. Its threshold is derived from the activation pressure difference calibration value recorded before entering the well based on the flow rate and the orifice diameter of the choke nozzle 5. When the pressure difference at both ends of the choke nozzle 5 drops below the activation pressure difference corresponding to the preload of the return spring 7, that is, below the lower limit of the activation window of 1.5 MPa to 2.5 MPa, the return spring 7 will recover the cutting seat 9 through the bidirectional linkage component 12. Its recovery condition is that the limiting shoulder 14 of the cutting seat 9 disengages from the limiting ring 13 and the arc-shaped cutter plate 10 is completely retracted into the contour of the outer cylinder 3. The value of this activation window is determined by the selected number of disc springs and the thread position of the return spring bracket 28. The remaining three items are passive redundancies with lower priority, independent of each other and not dependent on ground timing. When the locking screw 18 loosens or breaks to the extent that the arc-shaped blade 10 is radially displaced, the blade anti-drop step stops the arc-shaped blade 10 in the radial direction to prevent it from falling out of the cutting seat 9. When the roller shaft breaks, the roller anti-drop step stops the support roller 15 in the radial direction to prevent it from falling out of the roller groove. When the indicator water eye 21 is blocked by rock cuttings, the return action of the annular piston 6 and the recovery function of the cutting seat 9 are not affected. The indicator function and the recovery function are independent of each other, and the failure of the indicator does not affect the safe recovery.

[0035] In this embodiment, the cutting seat 9 is located on one side of the outer cylinder 3, and two rows of support rollers 15 are located approximately 180 degrees apart on the outer cylinder 3. This allows the radial reaction force generated by the single-sided cutting to be converted into the supporting force of the opposite support rollers 15 pressing against the well wall through the outer cylinder 3 body. The well wall being trimmed serves as the rotation reference surface. When the cutting resistance increases, the supporting clamping force increases synchronously, and the reference stiffness increases adaptively with the load. Therefore, the rotation trajectory of the entire small-depth scraping process is constrained by the well wall itself, avoiding the situation where the symmetrical multi-blade blades experience increased vibration due to uneven cutting depth of the two blades at small depths. This closed force relationship is the prerequisite for the stable operation of the single-sided eccentric configuration. The driving pressure difference is taken from the upstream and downstream of the throttling nozzle 5, rather than from the upstream of the nozzle and the annulus. This ensures that the activation pressure difference is determined only by the orifice diameter and displacement of the throttling nozzle 5, falling within a narrow window lower than that of other hydraulic tools in the same series. This facilitates controlled activation by increasing the displacement and avoids false activation under normal circulating displacement. The balance hole 31 takes pressure from the intermediate cavity rather than from the annulus. This is a necessary condition to ensure that the driving pressure difference is always equal to the pressure difference of the throttling nozzle 5 itself, and that the upstream and downstream pressures change synchronously without the difference remaining unchanged when the indicator bypass is opened. This ensures that the position indication action does not interfere with the extension and holding of the cutting seat 9. The driving ramp 11 is taken from the locking angle, so that the radial reaction force of the well wall on the arc-shaped cutter 10 during cutting is insufficient to push the annular piston 6 back through the axial component of the ramp. The cutting depth is kept constant at the limit position throughout the reaming process by the pump pressure holding force and the ramp self-locking. At the same time, the recovery is achieved by the return spring 7 pulling the cutting seat 9 in the positive axial direction through the T-shaped slide 16, without relying on the reverse self-locking of the ramp. Therefore, the two functions of forced recovery under pressure and self-locking during cutting do not conflict with each other. The limiting ring 13 rigidly abuts and limits the single-sided extension amount. In conjunction with the well wall self-reference, the enlarged diameter of the wellbore after dressing is mechanically constrained to have consistency. The level of numerical consistency is determined by the machining and installation accuracy of the limiting ring 13 and the envelope accuracy of the support roller 15. Compared to conventional tools that use symmetrical blades to concentrically enlarge the hole and rely on drill string stiffness for centering, this embodiment only requires work at one cutting point and rolling friction on the opposite side for the same micro-reaming amount. The required reaming torque and drilling pressure are reduced accordingly, and it can be used for long horizontal sections and small side-drilling wells with small margin of friction torque. The aforementioned torque reduction and diameter consistency are qualitative effects and design goals that can be derived from the aforementioned force closure, hard limit and self-reference structure relationship. The specific values ​​depend on the well conditions, formation and optional parameters.

[0036] Example 2 This embodiment, based on the eccentric micro-expanding eye assembly tool described in Embodiment 1, further provides a replaceable structure for the arc-shaped cutter plate 10 and a ground-based adjustment method for the unilateral micro-expanding amount and activation pressure differential. The composition, position, connection, and communication relationships of the spindle 2, outer cylinder 3, central flow channel 4, throttling nozzle 5, second throttling nozzle 29, annular piston 6, return spring 7, return spring bracket 28, driving inclined surface 11, bidirectional linkage assembly 12, limiting ring 13, limiting shoulder 14, cutting seat 9, support roller 15, and the connecting hole 30, balance hole 31, bypass hole 20, flow hole 19, and indicator water eye 21 are all the same as in Embodiment 1. The activation pressure differential window is 1.5 MPa to 2.5 MPa, and the basic diameter is 3 mm to 6 mm for the unilateral radial extension, also the same as in Embodiment 1. This embodiment only elaborates on the structure and adjustment relationship of the replaceable parts on-site and the adjustable quantity before well entry; other unmentioned parts are described in Embodiment 1.

[0037] The arc-shaped cutter plate 10 is a replaceable part independent of the cutting seat 9. A dovetail groove is formed axially on the outer arc-shaped surface of the cutting seat 9. The dovetail groove has a trapezoidal cross-section that is wider on the inside and narrower on the outside. A matching dovetail-shaped protrusion is machined at the root of the arc-shaped cutter plate 10, and this dovetail fit is axially embedded into the cutting seat 9. The dovetail fit radially constrains the arc-shaped cutter plate 10, preventing it from dislodging radially outwards. The axial position of the arc-shaped cutter plate 10 is determined by at least one locating pin. The locating pin passes through the corresponding pin hole on the arc-shaped cutter plate 10 and the cutting seat 9, preventing the arc-shaped cutter plate 10 from moving back and forth axially during scraping. The arc-shaped cutter plate 10 is then locked to the cutting seat 9 by at least one locking screw 18. The locking screw 18 passes radially from the outer arc surface of the arc-shaped cutter plate 10 and screws into the threaded hole of the cutting seat 9 body. The arc-shaped cutter plate 10 has a corresponding anti-drop step at its root and the corresponding position of the cutting seat 9. When the locking screw 18 fails due to vibration, loosening, or breakage, this step stops the arc-shaped cutter plate 10 radially, preventing it from falling off the outer end face of the cutting seat 9 even if it loses its lock. The grade of hard alloy inlaid in the arc-shaped cutter plate 10 is selected before well entry according to the abrasiveness of the formation in the target well section. For formations with strong abrasiveness, a higher wear-resistant grade is selected, and for formations with weak abrasiveness or high toughness requirements, a higher toughness grade is selected. When replacing, simply loosen the locking screw 18, pull out the old cutter plate axially, replace it with a new cutter plate of the same specification, and reset the positioning pin and locking screw 18. There is no need to disassemble the mandrel 2 and outer cylinder 3 of the eccentric micro-expanded eyelet 1.

[0038] The unilateral radial extension is determined by the assembly state of the limiting ring 13 on the return spring bracket 28. The limiting ring 13 is threaded onto the return spring bracket 28. By replacing the limiting ring 13 with one of different thicknesses or adjusting its thread position on the return spring bracket 28, the axial position of the annular piston 6 relative to the return spring bracket 28 at the end of its stroke in the pushing direction is changed. After calculation by the drive inclined surface 11, the unilateral radial extension of the cutting seat 9 is determined to be within the range of 3 mm to 6 mm. When the well section dressing requirement is large, a thinner limiting ring 13 is selected or it is screwed up to increase the extension stroke. When the dressing requirement is small, a thicker limiting ring 13 is selected or it is screwed down. The thickness of the limiting ring 13 is selected according to the target well diameter and the designed micro-expansion amount, which is a pre-entry design selection.

[0039] The activation differential pressure window is determined by the thread position of the return spring bracket 28 on the spindle 2, along with the number of disc springs. The return spring 7 is a disc spring assembly, as in Embodiment 1. Adjusting the thread position of the return spring bracket 28 on the spindle 2 changes the initial compression of the disc spring assembly. Increasing or decreasing the number of disc springs or adjusting the shims changes its equivalent stiffness. Both factors together set the activation differential pressure of the annular piston 6 within the range of 1.5 MPa to 2.5 MPa, making it lower than the working differential pressure of other hydraulic tools in the same drill string. The orifice diameter of the two-stage throttling device is selected according to the design displacement. The orifice diameter of the throttling nozzle 5 is selected according to the target activation differential pressure and displacement, so that the upstream and downstream pressure differential falls into the activation window at the design displacement. The orifice diameter of the second throttling nozzle 29 is selected according to the readable vertical pressure step amplitude, so that the vertical pressure drop caused by the indicating action is sufficient to be readable on the ground without affecting the main circulation. The preload of the disc spring, the number of disc springs, and the orifice diameter of the two-stage nozzles are all selected based on the displacement and the working pressure difference of the same string of tools. These are design selections made before entering the well, rather than conclusions drawn from on-site measurements.

[0040] The above three adjustment parameters are determined in the order of first the support, then the limiting ring. First, the activation pressure differential window is determined by the thread position of the return spring support 28 on the spindle 2, along with the number of disc springs. Then, the unilateral extension amount is determined by the thread position of the limiting ring 13 on the return spring support 28. Since the limiting ring 13 is mounted on the return spring support 28, adjusting the position of the limiting ring 13 relative to the return spring support 28 does not change the position of the return spring support 28 relative to the spindle 2. Therefore, the setting of the unilateral extension amount does not change the predetermined activation pressure differential. Reverse adjustment of the return spring support 28, along with the limiting ring 13, will move axially, changing the predetermined unilateral extension amount while changing the activation pressure differential. Therefore, the adjustment is performed in the above order to ensure that both parameters are determined independently.

[0041] This implementation method, based on the steps of lowering, activating, micro-expanding, indicating, and retrieving in Example 1, adds a ground adjustment and on-site replacement step before well entry. Before well entry, the cutterhead brand is selected according to the target well section, the thickness and thread position of the limiting ring 13 are adjusted, the thread position and number of disc springs of the return spring bracket 28 are adjusted, and the orifice diameter of the two-stage nozzles are selected. After assembly, the activation differential pressure window, single-sided micro-expanding amount, and vertical pressure indication step amplitude of the tool are determined accordingly. After well entry, the actions of each step are the same as in Example 1. If it is necessary to change the dressing amount or adapt to different formations between the same drilling trip or adjacent well sections, the arc-shaped cutterhead 10, the thickness of the limiting ring 13, or its thread position can be replaced near the wellhead after tripping, without having to disassemble the eccentric micro-expanding joint 1. After replacement or adjustment, the abnormal protection takes the forced recovery of pressure loss as described in Example 1 as the highest priority action. Its triggering conditions, activation differential pressure threshold source and recovery conditions are the same as in Example 1. In addition, the lower limit of the activation differential pressure window after adjustment is still higher than the differential pressure generated by the throttle nozzle 5 under normal drilling flow rate, but lower than the working differential pressure of other hydraulic tools in the same series. When the flow rate is in the normal circulation range, the driving differential pressure acting on the annular piston 6 is lower than the activation threshold corresponding to the preload of the return spring 7 and does not trigger the extension of the cutting seat 9. Based on this, the structure prevents false activation. If the expected vertical pressure step is not observed in the ground pressure test after replacing the arc-shaped cutter 10 or the limiting ring 13, it is determined that the cutting seat 9 is not in place. The thread position of the limiting ring 13 and the alignment relationship between the flow hole 19 and the bypass hole 20 should be checked again before entering the well.

[0042] The arc-shaped cutter plate 10 employs a four-fold combination of dovetail fitting, positioning pin positioning, locking screw 18, and anti-fall-step mechanism. This ensures overall replaceability while primarily distributing the cutting load to the dovetail fit and positioning pin, with the locking screw 18 only bearing axial compression. Therefore, failure of the locking screw 18 will not cause the arc-shaped cutter plate 10 to become a falling object in the well, achieving both replaceability and safety redundancy. The limit ring 13 is assembled onto the return spring bracket 28, and the disc spring is pre-tightened and set at the threaded position of the return spring bracket 28 relative to the spindle 2. This ensures that the fixed extension amount and the fixed activation pressure difference fall on two interconnected threaded pairs. The resulting unidirectional independent relationship guarantees that the micro-expansion amount can be adjusted independently without disturbing the activation pressure difference. The sequential constraint of first setting the bracket and then the limit ring is a necessary condition to achieve the separate setting of the two amounts with the fewest adjustable parts. The activation differential pressure window is set within a narrow range lower than the working differential pressure of other hydraulic tools in the same series. This allows this tool to activate before other tools when increasing displacement, and the differential pressure at normal drilling displacement is insufficient to overcome the disc spring preload. Thus, it suppresses false activation through structural means. The suppression margin is determined by the difference between the activation window and the working differential pressure of other tools. The aforementioned replaceable and adjustable configuration allows the same body to cover the operational needs of different well diameters, different micro-divergence volumes, and different abrasive formations through surface selection. The coverage range is defined by the selectable thickness range of the limiting ring 13, the selectable configuration of the disc spring, and the series of cutterhead grades. This adaptability is a qualitative effect that can be derived from the structural selection relationship, and the specific value depends on the well conditions and selected parameters.

[0043] Example 3 This embodiment provides an application implementation of the above-mentioned eccentric micro-reamer assembly tool set before drilling the wellhead string in a horizontal well, and elaborates on the structure of the upper roller centralizing section 25 and the lower guide section 22, as well as the working process of the three sections working together. The tool consists of an upper connector, roller centralizing section 25, eccentric micro-reamer section 1, guide section 22, and lower connector connected sequentially by API threads from top to bottom. The composition, drive, limiting, support, and indicating structure of the eccentric micro-reamer section 1 are described in Embodiment 1, and its replaceable arc-shaped cutterhead 10 and ground adjustment method are described in Embodiment 2. This embodiment focuses on the application of the roller centralizing section 25, guide section 22, and the entire string.

[0044] The roller centering joint 25 connects the upper connector and the eccentric micro-expanding eyelet 1, and includes a centering joint body 26 and three rows of centering rollers 27 evenly distributed circumferentially at approximately 120-degree angular intervals along the outer circumference of the centering joint body 26. The centering joint body 26 is a cylindrical component, with its upper end connected to the upper connector via an API thread and its lower end connected to the mandrel 2 of the eccentric micro-expanding eyelet 1 via an API thread. The interior of the body has a through-hole drilling fluid flow channel along the axis and is aligned with the central flow channel 4 of the mandrel 2. Several centering rollers 27 are arranged axially in each row. The centering rollers 27 are drum-shaped rollers and are supported by roller shafts in the axial roller mounting grooves of the centering joint body 26, and can rotate freely around the roller shafts. Their generatrices protrude from the outer circumference of the centering joint body 26. The inner bore of the centering roller 27 is provided with a centering roller anti-drop step. The centering roller anti-drop step is an inner boss in the inner bore, which forms a radial stop with the corresponding step at the end of the roller shaft. When the roller shaft breaks due to fatigue or impact, this step stops the centering roller 27 radially, preventing it from falling out of the mounting groove. The roller centering section 25 uses three rows of circumferentially distributed centering rollers 27 to center the pipe string at this point and convert the sliding friction between this point and the well wall into rolling friction.

[0045] The guide joint 22 connects the eccentric micro-expanding eyelet 1 and the lower connector. A right-hand spiral groove 23 is machined on the outer surface of the guide joint 22, extending from the upper to the lower end, forming an upward return channel for drilling fluid and cuttings. Cuttings generated by the eccentric micro-expanding eyelet 1 are jetted away from the arc-shaped cutter plate 10 through the indicator water eye 21 and then return upwards along the wellbore annulus with the drilling fluid. When passing through the spiral groove 23, the spiral path increases the effective flow area, reducing the possibility of cuttings accumulating and clogging between the tool's outer wall and the wellbore annulus. During subsequent cementing operations, the cement slurry generates a swirling flow as it passes through the spiral groove 23, improving the uniformity of annular filling. A tapered guide head 24 is provided at the lower end of the guide joint 22. The tapered guide head 24 has an outer contour that is wider at the top and narrower at the bottom, with a smooth transition on the conical surface. Its upper end is connected to the guide joint 22 body via an API thread, and its lower end is connected to the lower connector via an API thread. The API external thread at the lower end of the lower connector is used to continue the hydraulic rotary guide shoe downwards. When the tool encounters a wellbore step, keyway inlet, or reduced diameter section during descent, the conical surface of the conical guide head 24 causes the tool to gradually squeeze into the obstacle section instead of directly impacting it, reducing the impact of encountering resistance during descent.

[0046] This embodiment takes the wellbore cleaning operation before casing running in a 215.9 mm wellbore and 139.7 mm casing horizontal section of the side-drilling as an example. The cutting envelope diameter in the tool cutting state is composed of the outer diameter of the outer cylinder 3, the radial protrusion of the support roller 15, and the radial protrusion of the arc-shaped cutter plate 10 when the cutting seat 9 is in the maximum extended position. This cutting envelope diameter is taken to be 3 mm to 6 mm larger than the diameter of the wellbore to be repaired, and its value is determined by the selection of the limiting ring 13 as described in Embodiment 2. The outer diameter in the tool retracting state is composed of the outer diameter of the outer cylinder 3 and the radial protrusion of the support roller 15, and is taken to be smaller than the inner diameter of the upper casing to ensure that the tool passes through the upper casing and complex well sections when retracting.

[0047] The working process of this tool is as follows: the tool is assembled into the wellbore drilling string with the upper connector at the top, the lower connector at the bottom, and the hydraulic rotary guide shoe connected downwards. During the non-rotational lowering stage, the pump is not turned on or the circulation is at a small displacement. The cutting seat 9 is retracted within the outline of the outer cylinder 3. The three rows of centralizing rollers 27 of the roller centralizing section 25 and the two rows of support rollers 15 of the eccentric micro-expanding section 1 roll against the well wall. In the horizontal section, the tool naturally adheres to the lower edge of the wellbore with one side of the support rollers 15 facing the lower edge of the wellbore, and the cutting seat 9 facing the upper half of the wellbore. The conical guide head 24 guides the tool to gradually cross the step and the reduced diameter. After the tubing string reaches the section to be worked, the flow rate is increased to activate the eccentric micro-expanding section 1. The activation, micro-expanding, positioning indication, and pressure loss recovery processes are the same as in Example 1. The arc-shaped cutter 10 scrapes the steps, keyway edges, and reduced diameter sections on one side of the upper half of the wellbore. The cutting reaction force is pressed by the outer cylinder 3 against the two rows of support rollers 15 on the opposite side to form a rolling support reference. The cuttings are jetted away through the indicator water hole 21 and then returned upward with the drilling fluid, passing through the spiral groove 23 of the guide section 22 and discharged. The tool rotates along the well section and is slowly lowered or raised once to obtain a micro-expanded wellbore with a diameter equal to the diameter of the cutting envelope, which is then used for the low-resistance running of the subsequent casing string. In the abnormal handling of the operation, the highest priority is the forced recovery of pressure loss. Its triggering conditions, activation differential pressure threshold sources and recovery conditions are the same as in Example 1. When encountering obstruction during the lowering, the conical guide head 24 is used to gradually squeeze in to overcome the obstacle. If it is determined that the outer diameter of the tool is close to or reaches the inner diameter of the upper sleeve at that point and is blocked in the retracted state, the passage margin of the sum of the radial protrusion of the support roller 15 and the outer diameter of the outer cylinder 3 relative to the inner diameter of the sleeve at that point should be checked before deciding on the action. When the roller shaft of the straightening roller 27 or the support roller 15 breaks, the corresponding anti-fall step stops the roller in the radial direction to prevent it from falling out of the mounting groove or roller groove.

[0048] The three sections are combined in a functionally separate yet force-coordinated manner. The roller centering section 25 provides full-circumference centering and rolling drag reduction at the top with three rows of circumferentially distributed centering rollers 27. It does not undertake active dressing and therefore does not interfere with the unilateral force relationship of the eccentric micro-expanding section 1. The rotation reference required for unilateral cutting of the eccentric micro-expanding section 1 is provided by the two rows of support rollers 15 on its own circumferential side, rather than relying on the centering section or drill string stiffness for centering. Therefore, the dressing accuracy does not fluctuate with the upper centering condition. The phenomenon that the drill string adheres to the lower edge of the wellbore due to gravity in the horizontal section is reversed in this combination. When the tool is not rotated during running-in, the support roller 15 side naturally adheres to the lower edge, and the cutting seat 9 side faces the upper half of the wellbore where keyways and steps are common. The running-in process has a pre-positioning capability. The guide joint 22 promptly guides the cuttings out and creates a vortex during cementing, preventing the cuttings from re-accumulating into a cuttings bed at the bottom edge of the wellbore, thus avoiding repeated cutting and tool jamming, and maintaining the effectiveness of the initial dressing. The cutting envelope diameter is defined by the outer diameter of the outer cylinder 3, the protrusion of the support roller 15, and the protrusion of the arc-shaped cutter 10, and is rigidly constrained by the limiting ring 13. Combined with the fact that the outer diameter in the folded state is smaller than the inner diameter of the upper casing, the tool has both controlled micro-expansion during operation and passability when not in operation. The relationship between the two is a qualitative conclusion that can be derived from the structural dimensions, and the specific value depends on the target wellbore, the inner diameter of the upper casing, and the selected parameters.

[0049] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be modified within the scope of the concept described herein by means of the above teachings or the technology or knowledge in related fields.

Claims

1. An eccentric micro-reamer assembly tool for horizontal wells, comprising an upper connector and a lower connector, characterized in that, The eccentric micro-expanding tool assembly also includes an eccentric micro-expanding joint (1) connected between the upper and lower connectors. The eccentric micro-expanding joint (1) includes a mandrel (2) and an outer cylinder (3) fixedly fitted outside the mandrel (2). The mandrel (2) has a central flow channel (4) inside, and a throttling nozzle (5) is fixed inside the central flow channel (4). A ring piston (6) and a reset spring (7) that applies a reset preload force to the ring piston (6) are slidably sealed between the mandrel (2) and the outer cylinder (3). The mandrel (2) is provided with a drilling fluid pressure upstream of the throttling nozzle (5) to one end face of the ring piston (6). The connecting hole (30) and the balance hole (31) that leads the drilling fluid pressure downstream of the throttle nozzle (5) to the other end face of the annular piston (6) make the drilling fluid pressure difference upstream and downstream of the throttle nozzle (5) act on both ends of the annular piston (6). The outer cylinder (3) has a radially penetrating guide window (8) on only one side of its circumference. A cutting seat (9) is slidably assembled inside the guide window (8). An arc-shaped blade (10) is provided on the outer end face of the cutting seat (9). A driving inclined surface (11) is provided on the annular piston (6). A two-way linkage assembly (12) is provided between the driving inclined surface (11) and the cutting seat (9). When the throttle nozzle is throttled, the drilling fluid pressure downstream of the throttle nozzle (5) is slidably assembled on the other end face of the annular piston (6). When the hydraulic pressure difference between the upstream and downstream of the flow nozzle (5) overcomes the preload of the return spring (7), the annular piston (6) moves axially and pushes the cutting seat (9) radially outward via the drive ramp (11). When the pressure difference disappears, the return spring (7) drives the annular piston (6) to return and forces the cutting seat (9) radially back via the bidirectional linkage assembly (12). The eccentric micro-expanded eyelet (1) is fitted with a limit ring (13), and the annular piston (6) is provided with a limit shoulder (14). The annular piston (6) moves axially until the limit shoulder (14) abuts against the limit ring (13) and stops. (6) The axial travel of the cutting seat (9) is converted by the driving inclined plane (11) to rigidly limit the radial extension of the cutting seat (9) on one side. The outer cylinder (3) is provided with two rows of support rollers (15) arranged axially at a position 180 degrees relative to the cutting seat (9) in the circumference. The axial span of the two rows of support rollers (15) covers the axial length of the cutting seat (9). The support rollers (15) roll in contact with the well wall. The radial reaction force generated by the cutting seat (9) cutting the well wall is transmitted to the support rollers (15) through the outer cylinder (3), so that the support rollers (15) press against the well wall on the opposite side of the cutting seat (9) to form a rolling support reference.

2. The eccentric micro-reaming assembly tool for horizontal wells according to claim 1, characterized in that, The bidirectional linkage assembly (12) includes a T-shaped groove (16) opened on the drive inclined surface (11) and a T-shaped boss (17) set at the bottom of the cutting seat (9). The T-shaped boss (17) is slidably fitted in the T-shaped groove (16). When the annular piston (6) returns, it applies a radial pull force to the cutting seat (9) through the fitting of the T-shaped groove (16) and the T-shaped boss (17).

3. The eccentric micro-reaming assembly tool for horizontal wells according to claim 1, characterized in that, The eccentric micro-reaming joint (1) also includes a return spring bracket (28) threaded onto the mandrel (2). The return spring (7) is a disc spring assembly, with the lower end of the disc spring assembly supported by the return spring bracket (28). The preload of the disc spring assembly is adjusted by adjusting the thread position of the return spring bracket (28) on the mandrel (2), so that the activation pressure difference of the annular piston (6) is within the range of 1.5 MPa to 2.5 MPa, and this activation pressure difference is lower than the working pressure difference of the hydraulic tools matched in the drill string where the eccentric micro-reaming joint tool is located; limit The ring (13) and the return spring bracket (28) are threaded together to form a detachable assembly. The end position of the axial stroke of the ring piston (6) is limited by the threaded position of the limiting ring (13) on the return spring bracket (28) and converted into the single-sided radial extension of the cutting seat (9) by the driving inclined surface (11). The single-sided radial extension is limited to 3 mm to 6 mm. Adjusting the threaded position of the limiting ring (13) on the return spring bracket (28) does not change the position of the return spring bracket (28) and the preload of the disc spring assembly.

4. The eccentric micro-reamer assembly tool for horizontal wells according to claim 1, characterized in that, The curved blade (10) is a replaceable blade inlaid with cemented carbide. The outer end face of the cutting seat (9) is provided with a dovetail groove. The curved blade (10) is embedded in the cutting seat (9) through the dovetail groove and is positioned by a positioning pin and locked by a locking screw (18). A blade anti-fall step is provided between the root of the curved blade (10) and the cutting seat (9) to prevent the curved blade (10) from falling out radially.

5. The eccentric micro-reaming assembly tool for horizontal wells according to claim 1, characterized in that, The support roller (15) is a waist drum-shaped roller. The outer cylinder (3) has a roller groove. The support roller (15) is supported in the roller groove by the roller shaft. The inner hole of the support roller (15) is provided with a roller anti-drop step. The roller anti-drop step prevents the support roller (15) from falling out of the roller groove when the roller shaft is broken. The generatrix of the support roller (15) protrudes from the outer circle surface of the outer cylinder (3).

6. The eccentric micro-reamer assembly tool for horizontal wells according to claim 1, characterized in that, Downstream of the throttling nozzle (5) inside the central flow channel (4), a second throttling nozzle (29) is fixed. The throttling nozzle (5) and the second throttling nozzle (29) form an intermediate cavity. The side wall of the annular piston (6) is provided with a flow passage hole (19). The spindle (2) is provided with a bypass hole (20) connecting the intermediate cavity. The root of the cutting seat (9) is provided with an indicator water eye (21). When the annular piston (6) moves to the end of its stroke, the flow passage hole (19) and the bypass hole (20) are aligned and connected. A portion of the drilling fluid in the intermediate cavity flows through the flow passage hole. The drilling fluid bypasses the second throttling nozzle (29) and is ejected from the root of the arc-shaped cutter plate (10) through the bypass hole (20), the flow hole (19) and the indicator water eye (21). The remaining drilling fluid continues to flow downward through the second throttling nozzle (29). The flow rate of the drilling fluid through the second throttling nozzle (29) decreases, causing the pressure difference of the second throttling nozzle (29) to decrease. The pressure of the surface riser decreases in a step-like manner to indicate that the cutting seat (9) is extended into place. The throttling nozzle (5) always passes through all the drilling fluid, so that the pressure difference of the driving ring piston (6) is not affected.

7. The eccentric micro-reamer assembly tool for horizontal wells according to claim 1, characterized in that, The eccentric micro-expanding eye assembly tool also includes a guide section (22) connecting the eccentric micro-expanding eye section (1) and the lower connector. The outer surface of the guide section (22) is provided with a spiral groove (23), which forms an upward return channel for drilling fluid and cuttings. The lower end of the guide section (22) is provided with a tapered guide head (24) connected to the lower connector.

8. The eccentric micro-reaming assembly tool for horizontal wells according to claim 1, characterized in that, The eccentric micro-expanding eye assembly tool also includes a roller straightening section (25) connected between the upper connector and the eccentric micro-expanding eye section (1). The roller straightening section (25) includes a straightening section body (26) and three rows of straightening rollers (27) evenly distributed around the circumference of the straightening section body (26). The inner hole of the straightening roller (27) is provided with a straightening roller anti-fall step.

9. The eccentric micro-reamer assembly tool for horizontal wells according to claim 1, characterized in that, The eccentric micro-reaming assembly tool is configured as a well-drilling string connected to the downhole casing in a horizontal well. The outer diameter of the outer cylinder (3), the radial protrusion of the support roller (15), and the radial protrusion of the arc-shaped cutter plate (10) when the cutting seat (9) is in the maximum extended position together constitute the cutting envelope diameter, which is 3 to 6 millimeters larger than the diameter of the wellbore to be repaired.

10. The eccentric micro-reaming assembly tool for horizontal wells according to claim 1, characterized in that, The lifting angle of the driving inclined plane (11) is the self-locking angle. Under the radial reaction force of cutting the well wall, the axial component force generated by the driving inclined plane (11) on the annular piston (6) of the cutting seat (9) is insufficient to push the annular piston (6) back. This keeps the cutting seat (9) in the extended position defined by the limiting ring (13) during the cutting process. When the return spring (7) drives the annular piston (6) to return, the radial pull back of the cutting seat (9) through the bidirectional linkage assembly (12) is not affected by the self-locking.

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