Drilling string impact sliding wear experimental device and experimental method

Abstract

The invention relates to the technical field of well drilling string wear analysis, and particularly discloses a drilling string impact sliding wear experimental device and experimental method. The drilling string impact sliding wear experiment device comprises a supporting system, a lifting system, a vortex motion system and an environment system. According to the application, the active dynamic behavior of flexible self-excited vortex motion of the drill string is reproduced, and the contradiction that high-precision observation and extreme environment simulation cannot be compatible on the same device is solved through a visual / high-temperature closed switchable modular environment system. On the basis of the device, a non-uniform impact wear coupling high-temperature corrosion environment can be truly reproduced in a flexible vortex nonlinear contact form of the drill string to carry out a wear test. The experimental result of the device is similar to the material performance under the actual underground complex dynamic working condition.

Description

Technical Field

[0001] This application relates to the field of drilling string wear analysis technology, and in particular to a test apparatus and method for testing the impact sliding wear of drilling strings. Background Technology

[0002] As oil and gas exploration and development continues to advance into deep and ultra-deep wells, the friction and wear problems faced by downhole drill string systems are becoming increasingly prominent. The bottom-hole temperatures in deep and ultra-deep wells are extremely high, typically exceeding 150°C and even reaching over 300°C. This significantly exacerbates friction and wear between the drill pipe joint and the casing, a key factor leading to decreased casing strength and even major engineering accidents such as wellbore failure. Therefore, developing friction and wear experimental methods that can highly simulate complex downhole conditions and deeply reveal the friction and wear mechanism of the drill string-casing system under these conditions is crucial for ensuring drilling safety, optimizing drill string design, and extending casing life.

[0003] A comprehensive analysis of technological developments over the past decade reveals that drill pipe / casing friction and wear testing technology has evolved from single-condition simulation to complex-condition composite simulation. Key technological breakthroughs are primarily reflected in three aspects: motion patterns, environmental simulation, and sample size. Early devices focused on single linear motion modes, such as simple rotation or reciprocating motion. To more realistically simulate the complex motion states of the downhole drill string, the technology has gradually developed towards composite motion simulation. For example, the 2022 Chinese patent application "A Test Device and Evaluation Method for Rotary Reciprocating Wear of Casing under Complex Working Conditions" (CN202210697355.5) uses a clever mechanical structure (the sleeve annular guide groove and the slide rod cooperate) to realize the simulation of linear contact between the drill string and casing under the combined motion form of rotation, reciprocating and combined rotation and reciprocating motion on a single device. This significantly improves the simulation capability of the actual relative motion form of the drill string and casing. At the same time, it adopts a high temperature and high pressure autoclave system, which integrates heating jacket, insulation layer and gas-liquid medium injection and control functions. It can simulate high temperature, high pressure and gas-liquid-solid multiphase flow corrosive medium environment above 150℃, realize the effective simulation of high temperature and high pressure corrosion conditions above 150℃, and provide a platform for studying the wear-corrosion synergistic effect under extreme working conditions.

[0004] For example, the 2025 Chinese patent application "A Simulated Full-Size Casing and Drill Pipe Joint Wear Test Device" (CN202210697355.5) clearly proposes to use full-size casing and drill pipe joints for testing, and realizes the axial and radial composite vibration of drill pipe joints and full-size casing in drilling fluid environment and wear test of casing and drill pipe joints in well sections with different dogleg degrees through a six-degree-of-freedom platform, which greatly improves the consistency between experimental results and actual downhole conditions.

[0005] While the aforementioned technologies have made significant progress in motion modeling, environmental simulation, and sample size, the main approach relies on rigid transmission and external active drive to simulate motion (e.g., driving rotation via a rigid spindle and applying static lateral contact force to the outside of the casing, or actively applying radial displacement via a six-degree-of-freedom platform). These methods can effectively simulate the "passive" motion caused by wellbore geometric constraints, but they struggle to accurately simulate the "active" flexible vortex motion generated by the drill string's inherent flexibility, which stems from the system's dynamics. This "active" motion originating from the system's own dynamics and this nonlinear natural vibration differ fundamentally from the externally applied "passive" vibration in terms of motion model and the mechanism of friction and wear, making it difficult for related technologies to reveal their intrinsic mechanisms. Furthermore, there are still shortcomings in coupling high-temperature environment simulation (especially for ultra-deep well conditions at 200°C and above) with the aforementioned flexible dynamic behavior simulation.

[0006] Furthermore, the impact wear mechanism differs from traditional steady-state sliding wear. Under vortex conditions, significant impact loads exist between the drill string and casing. High-frequency impacts not only generate abrasive and adhesive wear but also trigger the initiation and propagation of surface fatigue cracks, leading to material spalling and accelerated failure. Related sliding wear testing methods struggle to reproduce this impact-dominated wear mechanism. Influenced by wellbore trajectory, drill string vortex modes, and the time-varying nature of contact conditions, casing wear exhibits significant circumferential and axial non-uniformity. In some localized areas, the wear depth can reach 3-5 times the average value, becoming a weak point for structural failure. Traditional uniform loading tests cannot reveal the formation mechanism and distribution patterns of this non-uniform wear. Related friction and wear tests often employ standardized loading conditions (such as constant load, constant speed, point contact, or line contact), and the test results differ significantly from the material performance under actual complex downhole dynamic conditions. There is a lack of testing methods that can compare and evaluate the performance of different wear-resistant materials and protective structures under real dynamic conditions.

[0007] Therefore, there is an urgent need for an experimental method that can realistically reproduce the coupling effect of drill string flexible eddy current and high-temperature corrosive environment, so as to provide key technical support for in-depth research on the friction and wear mechanism of drill string-casing system under various complex downhole conditions and to optimize drill bit protection technology. Summary of the Invention

[0008] This application provides a test apparatus and method for testing the impact sliding wear of drilling strings, aiming to solve the technical problem that existing technologies cannot truly reproduce the non-uniform impact wear under the flexible vortex nonlinear contact form of the drill string, making it difficult to conduct dynamic-wear coupling tests in high-temperature corrosive environments.

[0009] In the first aspect, this application proposes a test device for impact sliding wear of drilling string, and adopts the following technical solution.

[0010] An experimental device for impact sliding wear of drilling string includes a support system, a lifting system, a vortex system, and an environmental system.

[0011] The vortex system includes a rotator, a flexible shaft, and a mandrel. The rotator has a rotating shaft hinged to the top end of the flexible shaft, the flexible shaft is fixedly connected to the mandrel, and the bottom end of the mandrel is connected to the support system. A wear-resistant band is provided around the outer wall of the mandrel. The rotating shaft can drive the flexible shaft and the mandrel to rotate synchronously, while the mandrel can rotate freely in place relative to the support system. A lifting system is installed within the support system and can drive the rotator to descend, causing the flexible shaft to bend.

[0012] The environmental system includes a sleeve, a visualization cavity module, a camera, a calibration light source, a calibration ruler, a heating module, and a high-temperature resistant sealed cavity module. Marking points are set near the wear-resistant zone of the mandrel. In the first state of the environmental system, the sleeve is fitted over the mandrel, the visualization cavity module is fitted over the sleeve, the camera and the calibration light source are mounted outside the visualization cavity module and facing the marking points, and the calibration ruler is installed within the field of view of the camera. In the second state of the environmental system, the visualization cavity module, camera, calibration light source, and calibration ruler are removed, the sleeve is fitted over the mandrel, the heating module is mounted outside the sleeve, and the high-temperature resistant sealed cavity module is fitted over the sleeve.

[0013] By employing the above technical solutions, the "active" dynamic behavior of the drill string's flexible self-excited vortex was realistically reproduced. A modular environment system that allows for switching between visualization and high-temperature sealed environments resolved the contradiction between high-precision observation and extreme environment simulation on the same device. The replaceable wear-resistant strip and casing design enabled low-cost, high-efficiency comparative testing of the core friction pair. Because the frictional thickness loss of the wear-resistant strip is minimal, and by replacing the casing with one of equal thickness and inner diameter, the gap between the wear-resistant strip and casing can be kept consistent in each test. This device can realistically reproduce the wear test under the nonlinear contact form of the drill string's flexible vortex, coupled with a non-uniform impact wear environment and high-temperature corrosion. The experimental results using this device are similar to the material performance under actual complex downhole dynamic conditions.

[0014] Secondly, this application proposes a test method for impact sliding wear of drilling strings, and adopts the following technical solution.

[0015] A method for testing the impact sliding wear of drilling strings, using a drilling string impact sliding wear testing device, includes the following steps: S1. Based on the drill string parameters and working conditions on site, design the flexible shaft parameters based on the buckling morphology similarity criterion, and set the initial gap between the wear-resistant band and the casing based on the gap ratio similarity criterion.

[0016] S2, in the first state of the environmental system, a transparent medium is injected into the visualization cavity module, and motion videos of the marked points under different combinations of rotational speed and axial load are acquired. The pixel coordinates in the video are converted into physical coordinates based on the calibration ruler to calculate the eddy current characteristic parameters under each working condition. An eddy current working condition map is constructed with rotational speed and axial load as coordinates and the eddy current characteristic parameters as representations. The contact initiation boundary and high contact coverage area are marked in the map.

[0017] S3, switch the environmental system to the second state, inject corrosive medium into the high-temperature resistant sealed cavity module, and start the heating module to establish a high-temperature corrosive environment.

[0018] S4. Based on the eddy current condition map constructed in step S2, select at least one typical eddy current condition point, reproduce the speed and axial load corresponding to the condition point under the high temperature corrosion environment in step S3, and conduct a wear test for a set duration.

[0019] S5. After the test, the wear morphology and wear amount of the wear-resistant belt and the sleeve are taken out and analyzed.

[0020] S6. The wear amount obtained in step S5 is correlated with the eddy characteristic parameters of the corresponding working condition in step S2 to establish an eddy wear correlation model.

[0021] By adopting the above technical solution, this application proposes a systematic experimental method of calibration followed by verification, which ensures that the experimental conditions have clear and traceable kinetic significance in the invisible high-temperature corrosion environment. It realizes the scientific mapping from complex field conditions to controllable parameters in the laboratory, as well as the quantitative extrapolation from laboratory wear data to field wear risk, so that the experimental results have direct engineering guidance value.

[0022] A preferred embodiment of the drilling string impact sliding wear test method includes step S1, which comprises: Obtain the operating parameters of the target well section, including well depth, wellbore trajectory, drill string assembly, axial pressure, rotational speed, effective length of the drill string under pressure, contact gap, and drilling fluid properties.

[0023] Construct dimensionless parameters, including dimensionless buckling load coefficients. Where F is the axial pressure, L is the effective length of the compressed section, k is the boundary condition coefficient, EI is the bending stiffness, and the clearance ratio is... , The initial gap set for the laboratory This is a break in the work.

[0024] According to the similarity criterion, the test system is required to maintain similarity with the field drill string in terms of buckling morphology and clearance. Specifically, axial pressure, effective length of the compressed section, and bending stiffness are used as design variables to ensure that λ is consistent with the field drill string, with δ=0.95~1.05.

[0025] By adopting the above technical solutions, it is clear that dynamic similarity is the fundamental basis for experimental validity. Through dimensionless parameters λ and δ, a theoretical basis and quantitative design criteria are provided for small-scale laboratory models to truly reflect the large-scale drill string behavior downhole.

[0026] A preferred embodiment of the drilling string impact sliding wear test method includes step S2, which comprises: The system performs a working condition scan within a preset plane of rotational speed and axial load parameters, and acquires high-speed video of the marked points for each working condition.

[0027] Image processing is performed on high-speed video to extract the temporal trajectory (x(t), y(t)) of the marker points, and the pixel coordinates are converted into physical coordinates using a calibration ruler.

[0028] Based on time-series trajectory data, the eddy current characteristic parameters for each operating point are calculated, including: radial displacement. Root mean square eddy amplitude Maximum eddy amplitude Dimensionless eddy amplitude eddy characteristic frequency and contact coverage .in, This is the effective length of the flexible shaft.

[0029] Constructing based on rotational speed n and axial load F exp The eddy current condition diagram is a coordinate axis diagram, specifically dividing the condition region into: eddy current-free region. Slight eddy region Stable vortex region Strong vortex region According to A max =0.95Δ exp ~1.05Δ exp The conditions for marking the contact start boundary are based on η. contact Areas with a coverage rate of >60% are marked as high-contact areas.

[0030] By adopting the above technical solution, this application achieves a quantitative characterization of all elements of flexible eddy current amplitude, frequency, trajectory, and contact state, overcoming the shortcomings of traditional methods that only measure local characteristics. The eddy current condition map constructed in this application visualizes and regionalizes complex dynamic behavior, providing a scientific basis for subsequent targeted selection of typical wear conditions.

[0031] A preferred embodiment of the drilling string impact sliding wear test method includes step S3, which comprises: A pre-formulated corrosive simulated drilling fluid is injected into the high-temperature resistant sealed cavity module and connected to the circulation system. The heating module is then activated to raise the temperature of the medium inside the cavity to 200°C to 300°C and maintain this temperature at a constant and stable temperature for a preset time.

[0032] By adopting the above technical solution, this method can simulate the extreme downhole environment of 200℃ to 300℃ coupled with corrosive media.

[0033] A preferred embodiment of the drilling string impact sliding wear test method includes step S4, which comprises: Based on the eddy condition map obtained in step S2, several typical eddy condition points are selected for wear tests. The typical eddy condition points include one condition point from each of the slight eddy region, the stable eddy region, and the strong eddy region.

[0034] For each selected operating point, set the axial load so that the rotational speed and axial load of the flexible shaft reach the same state as the selected operating point.

[0035] By adopting the above technical solution, it is ensured that the wear test is based on the calibration spectrum, and covers typical areas of different wear mechanisms in a purposeful and representative manner, thereby improving the experimental efficiency and the comprehensiveness of the conclusions.

[0036] A preferred embodiment of the drilling string impact sliding wear test method includes step S5, which comprises: After the test, the temperature was lowered, and the mandrel containing the wear-resistant belt and the sleeve were removed, cleaned, and dried until the quality was stable.

[0037] The mass loss of the wear-resistant belt and the sleeve is measured, the depth distribution, width and area of ​​the wear tracks are measured, the micro-morphology of the wear surface is observed, and typical wear mechanism characteristics are identified.

[0038] By adopting the above technical solutions, a complete wear characterization method is covered from macroscopic (mass loss) to microscopic (morphological observation), providing a data foundation for multi-scale analysis of wear mechanisms.

[0039] A preferred embodiment of the drilling string impact sliding wear test method includes step S6, which comprises: From the eddy characteristic parameters obtained in step S2, extract the dimensionless eddy amplitude for the corresponding working condition. eddy characteristic frequency Contact coverage .

[0040] The wear characteristics are extracted from the data obtained in step S5, including the average wear rate, wear morphology type, and wear track location distribution.

[0041] Calculation of dimensionless wear index: Mass wear rate: Dimensionless wear rate Δm is the wear mass, t is the test time, ρ is the material density, v is the linear velocity, and F is the material density. ref For reference only.

[0042] Establish a correlation model for eddy wear: Under the same sleeve material conditions, compare the wear rates under different eddy conditions and analyze their relationship with eddy intensity parameters. Assume that there is a relationship between the dimensionless wear rate W* and the dimensionless eddy intensity A*, rotational speed Ω*, and temperature T: The fitting parameters C, α, β, and γ are obtained through multivariate nonlinear regression.

[0043] Field working condition prediction and application: Substitute the λ and rotational speed parameters of the drill string into the formula of this step, and combine the estimated contact load and running time in the field to predict the wear rate under this working condition, and assess the wear risk based on the prediction results. Predict the wear risk under different working conditions, construct an eddy wear risk map, superimpose the wear rate contour lines onto the eddy working condition map, and delineate low-risk, medium-risk, and high-risk zones.

[0044] By adopting the above technical solution, this application refines the complex wear phenomenon into a concise mathematical model, quantitatively revealing the coupled influence of factors such as vortex intensity, rotational speed, and temperature on the wear rate, so that the laboratory research results can be directly used to guide the optimization of drilling parameters and risk warning in the field.

[0045] In summary, the drilling string impact sliding wear test apparatus and method of this application have the following beneficial effects: 1. This test scheme ensures the consistency of the test system with the field drill string in terms of buckling morphology and vortex type by establishing a similarity criterion based on the buckling load coefficient λ.

[0046] 2. This test scheme utilizes the flexible self-excited vortex generated by the flexible shaft under axial compression and torsional loads to realistically reproduce the "active" dynamic behavior of the drill string. It differs from the traditional external forced vibration method and is more in line with the actual working conditions downhole.

[0047] 3. This test scheme uses high-speed cameras and image processing technology as the main means of observing eddy behavior, realizing the quantitative characterization of eddy amplitude, trajectory, frequency and contact state, and constructing eddy working condition map through working condition scanning, providing a scientific basis for subsequent test working condition selection and wear risk assessment.

[0048] 4. This test scheme adopts a replaceable module design and realizes "room temperature visualization calibration + high temperature corrosion and wear verification" in stages, which not only ensures the accuracy of eddy behavior identification, but also takes into account the safety and reliability of the device under high temperature and corrosion environment.

[0049] 5. This experimental scheme, by establishing a dimensionless parameter method and an eddy-wear correlation model, has achieved reliable extrapolation of laboratory results to field conditions, providing a theoretical basis for engineering parameter optimization and protective structure design.

[0050] 6. This experimental scheme, through parametric research methods, reveals the intrinsic law between eddy current intensity and wear behavior, ensures mechanistic equivalence, reveals the impact wear mechanism, establishes a quantitative correlation between impact frequency and fatigue wear rate, can quantitatively measure uneven wear distribution, and evaluates wear-resistant materials under real dynamic excitation, overcoming the limitations of standard tests and better meeting actual engineering needs. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the overall structure of the drilling string impact sliding wear test device in Example 1. It is also a diagram showing the state in which the vortex system does not apply axial pressure and radial rotational power to the mandrel and the flexible shaft is vertical.

[0052] Figure 2 This is a flowchart of the test method for impact sliding wear of drilling string in Example 2.

[0053] Figure 3 This is a schematic diagram of the bending of the flexible shaft caused by the simultaneous application of axial pressure and radial rotational power to the mandrel by the vortex system in Example 2.

[0054] Figure 4 for Figure 3 The local structure diagram.

[0055] Figure 5 for Figure 4 A partial structural diagram.

[0056] Reference numerals: 1. Ball joint; 2. Wear-resistant belt; 3. Mandrel; 4. Flange; 5. Flexible shaft; 6. Universal joint; 7. Motor mounting bracket; 8. Horizontal motor; 9. Reducer; 10. Base; 11. Sleeve; 12. Audio power head; 13. Lead screw; 14. Large pulley; 15. Small pulley; 16. Upper mounting cover; 17. Heating module; 18. High-temperature resistant sealed cavity module; 19. Camera; 20. Mud; 21. Welded joint; 22. Vertical motor. Detailed Implementation

[0057] The technical solutions in the embodiments are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Example 1

[0058] A test apparatus for impact sliding wear of drilling string, reference Figure 1 It includes a support system, a lifting system, a vortex system, and an environmental system.

[0059] The support system includes an upper mounting cover 16, a housing, and a base 10 connected from top to bottom.

[0060] The lifting system includes a horizontal motor 8, a reducer 9, a small pulley 15, a large pulley 14, and a lead screw 13. The horizontal motor 8 is mounted on a motor mounting bracket 7, which is fixed within an upper mounting cover 16. The lead screw 13 is mounted between the upper mounting cover 16 and the base 10 via bearing seats at both ends. The horizontal motor 8 is connected to the reducer 9, which is connected to the small pulley 15. The small pulley 15 is connected to the large pulley 14 via a transmission belt, and the large pulley 14 is connected to the lead screw 13. Starting the horizontal motor 8 drives the small pulley 15 to rotate via the reducer 9, which in turn drives the large pulley 14 to rotate, thus causing the lead screw 13 to rotate.

[0061] The vortex system includes an acoustic power head 12, a rotator, a flexible shaft 5, and a mandrel 3. The rotator is a vertical motor 22. The acoustic power head 12 is mounted on a lead screw 13 via a matching thread; the rotating lead screw 13 drives the acoustic power head 12 to move up and down. The rotator is mounted on the acoustic power head 12, and its axial rotation is connected downwards to the upper end of the flexible shaft 5 via a universal joint 6. The lower end of the flexible shaft 5 is fixedly connected to the upper end of the mandrel 3 via a flange 4, and the lower end of the mandrel 3 is connected to the base 10 via a ball joint. The mandrel 3 simulates the drill pipe used in oil and gas exploration. The axial vibration applied by the acoustic power head 12 (especially in the low-frequency range) couples with the inherent dynamic characteristics of the flexible shaft 5, significantly exacerbating the radial vibration induced by the flexible vortex. This aggravating effect of axial excitation on radial dynamics is key to this device's ability to simulate complex downhole vibration environments and reveal the vibration-coupled wear mechanism. (Reference) Figure 5 The outer wall of the mandrel 3 is provided with a wear-resistant belt 2, which is welded to the mandrel 3. This wear-resistant belt 2 is replaceable. Figure 5 The weld point 21 where the wear-resistant belt 2 is welded to the mandrel 3 is shown. Marking points are set on the mandrel 3 near the wear-resistant belt 2 to calibrate the motion characteristics of the mandrel 3.

[0062] The environmental system includes a sleeve 11, a visualization cavity module, a camera 19, a calibration light source, a calibration ruler, a heating module 17, an insulation layer, and a high-temperature resistant sealed cavity module 18. The visualization cavity module can be made of transparent material or have an observation window. The high-temperature resistant sealed cavity module 18 is an all-metal sealed cavity structure without an observation window. The camera 19 is a high-speed camera. Both the horizontal motor 8 and the vertical motor 22 can be servo motors.

[0063] The first state of the environmental system is as follows: the sleeve 11 is fitted over the mandrel 3, the visualization cavity module is fitted over the sleeve 11, the camera 19 and calibration light source are mounted outside the visualization cavity module and facing the marked point, and the calibration ruler is mounted within the field of view of the camera 19. This first state allows for room-temperature weak corrosion eddy current testing. The second state of the environmental system is as follows: the visualization cavity module, camera 19, calibration light source, and calibration ruler are removed; the sleeve 11 is fitted over the mandrel 3; the heating module 17 is mounted outside the sleeve 11; the insulation layer covers the outside of the heating module 17; and the high-temperature resistant sealed cavity module 18 is fitted over the sleeve 11. This second state allows for high-temperature strong corrosion testing. In both states, the sleeve 11 and the wear-resistant belt 2 form a friction pair. It should be noted that, for ease of display of the various components, the attached... Figure 1 The diagram illustrates the installation structure for the two-state switching process, showing the heating module 17, the high-temperature resistant sealed cavity module 18, and the camera 19. The installation position of the camera 19 is illustrative; in practice, multiple cameras 19 can be set up at multiple angles to capture the trajectory of the marked points. (Attached) Figure 3 yes Figure 1The diagram shows the operating status of the device during the experiment, and also shows the heating module 17, the high-temperature resistant sealed cavity module 18, the camera 19, and the mud 20.

[0064] The experimental setup also includes various sensors, such as vibration acceleration sensors, torque sensors, speed sensors, axial load sensors, contact force sensors, temperature sensors, and pressure sensors. The vibration acceleration sensor can be mounted on the base 10 near the ball joint 1 to directly measure the high-frequency impacts and vibrations of the system, used to identify eddy frequency and impact events. The torque sensor can be mounted on the rotating shaft of the vertical motor 22 to measure the input torque of the drive system; its fluctuation characteristics are a key dynamic signal for indirectly determining the eddy contact state (such as whether a collision has occurred, the degree of friction intensity). The speed sensor can be mounted on the output shaft of the vertical motor 22 to measure and provide feedback control of the rotational speed of the flexible shaft 5. The axial load sensor can be mounted between the output shaft of the vertical motor 22 and the universal joint 6 to measure and provide feedback control of the axial pressure applied to the flexible shaft 5 system. The contact force sensor is mounted on the inner wall of the sleeve 11 to measure the radial contact force / impact force between the mandrel 3 and the sleeve 11. The temperature sensor is inserted into the medium to measure the medium temperature. Pressure sensors are installed on the top or side wall interface of the all-metal high-temperature cavity module to monitor the pressure of the medium inside the sealed cavity within a safe range and to take into account the effect of pressure on corrosion / cavitation. Example 2

[0065] A test method for impact sliding wear of drilling strings is provided, using the drilling string impact sliding wear test apparatus of Example 1, with reference to... Figure 2 The experimental method includes the following steps.

[0066] Step 1: Parameter design of the test system based on buckling morphology similarity This step aims to establish a dynamic similarity between the small-scale laboratory model and the full-scale downhole drill string system, ensuring that the experimental phenomena are comparable to actual downhole conditions.

[0067] Step 1.1: Obtain the target well section operating parameters, including well depth (provided for step 6.6 to estimate axial pressure, and also for estimating bottom hole temperature for designing the target temperature in step 3; for example, at a well depth of 5000 meters, the geothermal gradient is approximately 3℃ / 100 meters, and the bottom hole temperature can reach over 150℃), and wellbore trajectory (determining L and Δ). field ), drill string assembly (determining EI), axial pressure, rotational speed, effective length L of the drill string under pressure (the length of the section of the drill string that may buckle and become unstable downhole, which is the length of the drill string section between two adjacent constraint points that mainly bears axial pressure), and initial contact gap Δ between the drill string and casing 11. field And the properties of the drilling fluid (as a reference for preparing simulated corrosion fluid); Step 1.2: Construct dimensionless parameters, including: Dimensionless buckling load factor: λ = F·L 2 / (k·EI), where F is the axial pressure (from the weight of the upper part of the drill pipe), L is the effective length, EI is the bending stiffness, and k is the boundary condition coefficient (determined by the constraint method at both ends of the drill pipe). Gap ratio: δ=Δ exp / Δ field (On-site gap); Δ exp The initial clearance that should be set for the laboratory; Δ field For on-site clearance; Δ field =(Casing 11 inner diameter - Drill string outer diameter) / 2; Δ exp = (Inner diameter of casing - Outer diameter of wear-resistant belt) / 2; Step 1.3: According to the similarity criterion, in order to make the dynamic behavior of the laboratory model (experimental system) similar to that of the field drill string, the experimental system and the field drill string must maintain similarity in buckling morphology and clearance ratio, that is, the following must be satisfied: λ exp =λ field And δ≈1, for example δ=0.95~1.05; it should be noted that in this application, the subscript exp represents the test system and field represents the field. Step 1.4: Using the diameter of the flexible shaft 5, effective length, material bending stiffness, and clearance as design variables, ensure that λ and δ are consistent with the drill string on site; Step 1.5: Map the field operating parameters to the test control parameters, and verify the similarity through pre-tests. If there is a deviation, fine-tune the soft shaft 5 parameter in Step 1.4 until the similarity requirements are met.

[0068] Step 2: Visual Calibration of Eddy Running Conditions and Boundary Recognition Methods at Room Temperature This step comprehensively maps and quantifies the eddy current behavior of the test system under different operating conditions in a transparent and mild environment, providing a "map" for high-temperature testing.

[0069] Step 2.1: Assemble the visualization test system, i.e., switch the environmental system to the first state, including installing the flexible shaft 5, mandrel 3, and sleeve 11. The sleeve 11 is placed outside the mandrel 3, and the visualization cavity module is placed outside the sleeve 11. Install a high-speed camera 19 (frame rate 500-2000fps, resolution ensures single pixel physical size ≤0.1mm) and a calibration light source (such as an LED ring light source or a laser light source) on the outside of the visualization cavity module; coat the area of ​​the mandrel 3 near the wear-resistant band 2 with high-contrast markings (such as a white or fluorescent coating with a diameter of 3-5mm), with the camera 19 and calibration light source facing the markings, and arrange a graduated calibration ruler (graduation accuracy 1mm) within the field of view of the camera 19; inject a transparent or weakly corrosive medium into the cavity, such as deionized water, saline, glycerin solution, etc. Step 2.2: Calibrate the sensor, conduct a no-load test run to confirm that the system has no abnormal vibration or noise, and verify the imaging quality of the high-speed camera 19; Step 2.3: Perform a working condition scan along a preset path within the speed-axial load parameter plane. For each working condition point, after the speed and axial load stabilize (stabilization time not less than 10s), start the high-speed camera 19 to continuously acquire video for 5-10s to ensure complete recording of multiple vortex cycles; simultaneously acquire high-speed images, vibration, torque, load, and temperature signals. Step 2.4: Perform image processing on the high-speed video, use image recognition technology to extract the pixel coordinates of the marker points in each frame of the image, and convert them into real physical coordinates according to the calibration ruler, so as to obtain the time trajectory (x(t), y(t)) of the marker points; Step 2.5: Calculate eddy characteristic parameters based on trajectory data, including: radial displacement. Root mean square eddy amplitude: Maximum eddy amplitude: Dimensionless eddy amplitude: , trajectory ellipse eccentricity, eddy characteristic frequency f whirl and frequency ratio, contact / disconnection status and contact coverage η contact : Percentage of contact time to total time; Contact angle distribution: Statistical analysis of vortex characteristics such as the angle range at which contact occurs. Where, L exp This is the effective length of the flexible shaft 5.

[0070] Step 2.6: Construction of eddy current condition diagram: under load F expOn the speed-n parameter plane (or λ-speed plane), the dimensionless amplitude A* of each operating point is represented by color coding or contour lines. Based on the eddy amplitude and contact characteristics, the operating areas are divided into: no eddy zone (no significant oscillation): A* < 0.001, slight eddy zone (intermittent or no contact oscillation): 0.001 ≤ A* < 0.02, stable eddy zone (stable eddy with continuous contact): 0.02 ≤ A* < 0.05, and strong eddy zone (intense eddy with high-frequency impact): A* ≥ 0.05. On the eddy operating condition map, the contact initiation boundary (A*) is marked. max ≈Δ exp Specifically, it can be set as A. max =0.95Δ exp ~1.05Δ exp ) and areas with high contact coverage (contact coverage η) contact (>60%), this spectrum serves as the basis for selecting representative eddy current conditions in subsequent high-temperature corrosion and wear tests.

[0071] Step 3: Establishment of a high-temperature corrosive environment This step switches the test environment to a closed, high-temperature, and corrosive environment that simulates extreme downhole conditions.

[0072] Step 3.1: Remove the visualization cavity module and replace it with an all-metal high-temperature sealed cavity module; remove camera 19, calibration light source, and calibration ruler; Step 3.2: Reference Figure 1 The sleeve 11 is placed outside the mandrel 3, the heating module 17 is installed outside the sleeve 11, and the high-temperature resistant sealed cavity module 18 is placed outside the sleeve 11, so that the environmental system can be switched to the second state. Step 3.3: Inject a pre-formulated corrosive simulated drilling fluid, such as mud 20, into the cavity, connect it to the circulation system, and set the flow rate; Step 3.4: Start heating module 17, raise the temperature to the target temperature of 200~300℃ according to the set heating rate, and keep the temperature stable for 10~30 minutes; Step 3.5: Monitor the chamber temperature, pressure, and medium status in real time to confirm that the environmental parameters are stable.

[0073] Step 4: Selection and Loading of Typical Whirlpool Conditions Wear tests were conducted under known kinetic conditions based on the calibration chart.

[0074] Step 4.1: Based on the eddy condition diagram obtained in Step 2.6, select several typical working points for wear tests, such as at least one working point in each of the slight eddy region, stable eddy region, and strong eddy region. Step 4.2: Reference Figure 3 and Figure 4For each selected working point, the rotational speed and axial (vertical) load of the flexible shaft 5 are set so that the flexible shaft 5 reaches the whirl state corresponding to the calibration stage under high temperature and corrosion environment. Step 4.3: By comparing the characteristics of torque fluctuation and load signal acquired in real time, the consistency between the eddy state and the room temperature calibration stage is indirectly verified. Step 4.4: Maintain the target eddy current condition and run the test for the set time of 30–180 minutes; Step 4.5: Real-time acquisition of torque, speed, axial load, contact force, cavity temperature and pressure signals.

[0075] Step 5: Post-test sample processing and wear characterization The worn samples were subjected to standardized treatment and multi-scale analysis.

[0076] Step 5.1: After the test, cool down to the safe temperature at the set cooling rate, drain the corrosive medium, and disassemble the high-temperature resistant sealed cavity module 18; Step 5.2: Remove the key friction pair components, such as the mandrel 3 and sleeve 11 containing the wear-resistant belt 2, and perform ultrasonic cleaning (frequency 40kHz, time 5~10min) with an appropriate cleaning solution (such as anhydrous ethanol, acetone or deionized water) to remove residual media and corrosion products. Dry them at low temperature (such as 60℃) in a constant temperature oven until the quality is stable (the difference between two consecutive weighings is <0.5mg). Step 5.3: Wear Measurement: Mass loss is measured using an electronic balance. The depth distribution, width, and area of ​​the wear track are measured using a three-dimensional profilometer (vertical resolution <1μm). The wear morphology is observed using a scanning electron microscope or an optical microscope. The microscopic features of the wear surface are observed, and typical wear mechanism features are identified. If necessary, energy dispersive spectroscopy (EDS) is used to detect the elemental distribution of the wear surface, determine the composition of corrosion products, and identify the synergistic mechanism of wear (abrasive particles, adhesion, fatigue) and corrosion.

[0077] Step 6: Dynamic-Wear Correlation Analysis and Dimensionless Consolidation By correlating motion data with wear results, a predictable mathematical model can be established.

[0078] Step 6.1: From the eddy characteristic parameters obtained during the room temperature visualization calibration stage, extract the dimensionless eddy amplitude A* and eddy characteristic frequency f corresponding to the working condition. whirl Contact coverage η contact ; Step 6.2: Extract wear characteristics from the data obtained in Step 5.3, including average wear rate, wear morphology type, and wear track location distribution; Step 6.3: Calculation of dimensionless wear index: mass wear rate W m =Δm / t, unit [kg / J]; volumetric wear rate Wv =(h avg ×w×L wear ) / t, unit [m³ / J], h avg The average wear depth is w, the wear width is L. wear The wear mark length is given by ρ, and the test time is given by t; the dimensionless wear rate W∗=Δm / (ρ×v×F) ref ×t), Δm is the wear mass, t is the test time, ρ is the material density, v is the linear velocity, and F ref The reference force is the contact force. Step 6.4: Establish the eddy-wear correlation model: Under the same sleeve 11 material conditions, compare the wear rates under different eddy conditions and analyze their relationship with the eddy intensity parameters; assume that there is a power law or exponential relationship between the dimensionless wear rate W* and the dimensionless eddy intensity A*, rotational speed Ω*, and temperature T: W* = C × (A*). α ×(Ω∗) β The fitting parameters C, α, β, and γ are obtained through multivariate nonlinear regression, using ×exp(γT), and the goodness of fit R is calculated. 2 and residuals; Step 6.5: Wear Mechanism Analysis: Combining the morphological observation results in Step 5.3 with the quantitative correlation in Step 6.4, the wear mechanisms of the slight whirl zone, stable whirl zone, and strong whirl zone are analyzed. Step 6.6: On-site working condition prediction and application: Substitute the parameters such as λ and rotation speed of the drill string into the correlation model established in Step 6.4, and combine the estimated contact load and running time on site to predict the relative wear risk under different working conditions; construct the eddy-wear risk map, superimpose the wear rate contour lines onto the eddy working condition map, and delineate: low-risk area, medium-risk area, and high-risk area.

[0079] The drilling string impact sliding wear test apparatus and test method of this application have produced the following effects.

[0080] 1. The dynamic simulation has high realism and reveals a new mechanism of "active" eddy wear.

[0081] Current drilling string impact-sliding wear experimental setups mostly rely on external rigid drives to simulate "passive" vibrations, making it difficult to reproduce the "active" self-excited vortexing generated by the drill string's own flexibility. This application employs a dynamic subsystem centered on a "flexible shaft 5-ball joint 1," which spontaneously buckles under axial pressure and naturally develops into three-dimensional vortexing under rotational drive. This method realistically reproduces the nonlinear, self-excited dynamic nature of the downhole drill string, providing a key experimental means for studying the impact fatigue wear mechanism and circumferential non-uniform wear distribution dominated by periodic high-frequency impacts, which cannot be revealed by traditional methods.

[0082] 2. A phased experimental method of "calibration first, verification later" was established to overcome the contradiction between observation and simulation.

[0083] Current technologies struggle to simultaneously simulate extreme environments and conduct high-precision behavior observations on a single device. This application designs interchangeable "visualization modules" and "all-metal high-temperature sealed modules," along with "transparent / weakly corrosive media" and "high-temperature corrosive media." Through two independent yet interconnected stages—"room-temperature visualization precision calibration" and "high-temperature corrosive environment verification"—it ensures the accuracy of quantitative characterization of eddy amplitude, trajectory, frequency, and contact state using high-speed photography and image processing, while also achieving safe and reliable simulation of ultra-high temperature, high pressure, and corrosive drilling fluid environments of 200-300℃.

[0084] 3. A scientific quantitative extrapolation bridge has been established from the laboratory to the field.

[0085] Current experiments largely focus on observational phenomena, with results that are difficult to directly guide engineering. This application introduces a dynamic similarity criterion based on the dimensionless buckling load coefficient (λ) and clearance ratio (δ), scientifically scaling down the massive field drill string system to a laboratory model. By constructing an "eddy current condition map" and an "eddy current-wear correlation mathematical model," wear data obtained from small-scale laboratory tests can be quantitatively and reliably extrapolated to predict the wear risk of full-size downhole drill strings under different operating conditions. This provides direct theoretical and data support for drilling parameter optimization, drill string selection, and casing life prediction.

[0086] 4. The experimental design is efficient and economical.

[0087] This application transforms costly full-scale testing into low-cost, repeatable sample-level testing through a modular, replaceable wear-resistant belt 2 and sleeve 11 design. This design not only significantly reduces experimental costs but also enables systematic comparison and evaluation of the performance of different wear-resistant materials, coatings, or protective structures on the same benchmark. The apparatus and method simultaneously meet the scientific need for in-depth exploration of wear mechanisms (through visualization and multi-sensor fusion analysis) and the practical need for rapid selection of engineering materials.

[0088] 5. The measurement and diagnostic system is comprehensive and multi-dimensional, with strong data correlation.

[0089] This application integrates a complete data chain encompassing high-speed visual measurement, simultaneous monitoring by multiple sensor types (vibration, torque, load, temperature, pressure), and post-experiment multi-scale morphology analysis (3D profile, SEM / EDS). This multi-dimensional data fusion capability enables precise correlation and cross-validation of "kinematic input (eddy current parameters)," "dynamic response (torque, vibration)," "environmental conditions (temperature and pressure)," and the final "material damage output (wear amount and morphology)," thus constructing a more accurate wear mechanism.

[0090] 6. The experimental procedure is standardized, highly operable, and the results are highly reproducible.

[0091] This application provides a complete, clear, and step-by-step experimental method, forming a standardized operating procedure from parameter design, system calibration, environment setup, operating condition selection to post-processing analysis. This method minimizes the interference of human factors, ensures the controllability of the experimental process and the reliability and high repeatability of the experimental results, and is conducive to comparative studies and data accumulation in different laboratories.

[0092] In summary, this application not only provides a highly accurate experimental setup but also constructs a complete methodological system encompassing basic research and engineering applications. It effectively solves core problems in current drill string-casing friction and wear research, such as distorted dynamic behavior and incomplete environmental simulation. This has significant theoretical and engineering value for ensuring drilling safety in deep and ultra-deep wells, extending the lifespan of drill strings and casing, and reducing exploration and development costs.

[0093] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A test apparatus for impact sliding wear of drilling tubing, characterized in that, This includes the support system, lifting system, vortex system, and environmental system; The vortex system includes a rotator, a flexible shaft (5), and a mandrel (3); the rotator has a rotating shaft hinged to the top end of the flexible shaft (5), the flexible shaft (5) is fixedly connected to the mandrel (3), and the bottom end of the mandrel (3) is connected to the support system; the outer wall of the mandrel (3) is provided with a wear-resistant belt (2); the rotating shaft can drive the flexible shaft (5) and the mandrel (3) to rotate synchronously, while the mandrel (3) can rotate freely in place relative to the support system; the lifting system is installed in the support system and can drive the rotator to descend, causing the flexible shaft (5) to bend; The environmental system includes a sleeve (11), a visualization cavity module, a camera (19), a calibration light source, a calibration ruler, a heating module (17), and a high-temperature resistant sealed cavity module (18); a marking point is set near the wear-resistant belt (2) area of ​​the mandrel (3); the first state of the environmental system is that the sleeve (11) is sleeved outside the mandrel (3), the visualization cavity module is sleeved outside the sleeve (11), the camera (19) and the calibration light source are installed outside the visualization cavity module and facing the marking point, and the calibration ruler is installed within the field of view of the camera (19); the second state of the environmental system is that the visualization cavity module, the camera (19), the calibration light source, and the calibration ruler are removed, the sleeve (11) is sleeved outside the mandrel (3), the heating module (17) is installed outside the sleeve (11), and the high-temperature resistant sealed cavity module (18) is sleeved outside the sleeve (11).

2. A test method for impact sliding wear of drilling strings, characterized in that, The drilling string impact sliding wear test apparatus as described in claim 1 is used for the experiment, and the experimental method includes the following steps: S1. Based on the drill string parameters and working conditions on site, design the parameters of the flexible shaft (5) based on the buckling morphology similarity criterion, and set the initial gap between the wear-resistant belt (2) and the casing (11) based on the gap ratio similarity criterion. S2, in the first state of the environmental system, a transparent medium is injected into the visualization cavity module, and motion videos of the marked points under different combinations of rotational speed and axial load are collected. Based on the calibration ruler, the pixel coordinates in the video are converted into physical coordinates to calculate the eddy covariance characteristic parameters under each working condition. An eddy covariance working condition map is constructed with rotational speed and axial load as coordinates and the eddy covariance characteristic parameters as the characterization. The contact initiation boundary and high contact coverage area are marked in the map. S3, switch the environmental system to the second state, inject corrosive medium into the high-temperature resistant sealed cavity module (18), and start the heating module (17) to establish a high-temperature corrosive environment; S4. Based on the eddy current condition map constructed in step S2, select at least one typical eddy current condition point, reproduce the speed and axial load corresponding to the condition point under the high temperature corrosion environment in step S3, and conduct a wear test for a set duration. S5. After the test, the wear morphology and wear amount of the wear-resistant belt (2) and the sleeve (11) are taken out and analyzed. S6. The wear amount obtained in step S5 is correlated with the eddy characteristic parameters of the corresponding working condition in step S2 to establish an eddy wear correlation model.

3. The drilling string impact sliding wear test method according to claim 2, characterized in that, Step S1 includes: Obtain the target well section's operating parameters, including well depth, wellbore trajectory, drill string assembly, axial pressure, rotational speed, effective length of the drill string under pressure, contact gap, and drilling fluid properties; Construct dimensionless parameters, including dimensionless buckling load coefficients. Where F is the axial pressure, L is the effective length of the compressed section, k is the boundary condition coefficient, EI is the bending stiffness, and the clearance ratio is... , The initial gap set for the laboratory For on-site gaps; According to the similarity criterion, the test system is required to maintain similarity with the field drill string in terms of buckling morphology and clearance. Specifically, axial pressure, effective length of the compressed section, and bending stiffness are used as design variables to ensure that λ is consistent with the field drill string, with δ=0.95~1.

05.

4. The drilling string impact sliding wear test method according to claim 2, characterized in that, Step S2 includes: The working condition is scanned within the preset speed and axial load parameter plane, and high-speed video of the marked point is acquired for each working condition point; Image processing is performed on high-speed video to extract the temporal trajectory (x(t), y(t)) of the marker points, and the pixel coordinates are converted into physical coordinates using a calibration ruler; Based on time-series trajectory data, the eddy current characteristic parameters for each operating point are calculated, including: radial displacement. Root mean square eddy amplitude Maximum eddy amplitude Dimensionless eddy amplitude eddy characteristic frequency and contact coverage ;in, The effective length of the flexible shaft (5); Constructing based on rotational speed n and axial load F exp The eddy current condition diagram is a coordinate axis diagram, specifically dividing the condition region into: eddy current-free region. Slight eddy region Stable vortex region Strong vortex region According to A max =0.95Δ exp ~1.05Δ exp The conditions for marking the contact start boundary are based on η. contact Areas with a coverage rate of >60% are marked as high-contact areas.

5. The test method for impact sliding wear of drilling strings according to claim 2, characterized in that, Step S3 includes: Inject a set formula of corrosive simulated drilling fluid into the high-temperature resistant sealed cavity module (18) and connect it to the circulation system. Start the heating module (17) to raise the temperature of the medium in the cavity to 200°C to 300°C and keep it at a constant temperature for a preset time.

6. The drilling string impact sliding wear test method according to claim 2, characterized in that, Step S4 includes: Based on the eddy condition map obtained in step S2, several typical eddy condition points are selected for wear tests. The typical eddy condition points include one condition point from each of the slight eddy region, stable eddy region and strong eddy region. For each selected working point, set the axial load so that the rotational speed and axial load of the flexible shaft (5) are the same as those of the selected working point.

7. The drilling string impact sliding wear test method according to claim 4, characterized in that, Step S5 includes: After the test, the temperature was lowered, and the mandrel (3) containing the wear-resistant belt (2) and the sleeve (11) were removed, cleaned and dried until the quality was stable. Measure the mass loss of the wear-resistant belt (2) and the sleeve (11), measure the depth distribution, width and area of ​​the wear marks, observe the micro morphology of the wear surface, and identify typical wear mechanism characteristics.

8. The drilling string impact sliding wear test method according to claim 7, characterized in that, Step S6 includes: From the eddy characteristic parameters obtained in step S2, extract the dimensionless eddy amplitude for the corresponding working condition. eddy characteristic frequency Contact coverage ; The wear characteristics are extracted from the data obtained in step S5, including the average wear rate, wear morphology type, and wear track location distribution. Calculation of dimensionless wear index: Mass wear rate: Dimensionless wear rate Δm is the wear mass, t is the test time, ρ is the material density, v is the linear velocity, and F is the material density. ref For reference only; Establish a correlation model for eddy wear: Under the same sleeve (11) material conditions, compare the wear rates under different eddy conditions and analyze their relationship with eddy strength parameters; assume that there is a relationship between the dimensionless wear rate W* and the dimensionless eddy strength A*, rotational speed Ω*, and temperature T: The fitting parameters C, α, β, and γ are obtained through multivariate nonlinear regression. On-site working condition prediction and application: Substitute the λ and rotation speed parameters of the drill string on-site into the relationship in this step, and combine the estimated contact load and running time on-site to predict the wear rate under this working condition, and assess the wear risk based on the prediction results; predict the wear risk under different working conditions, construct the eddy wear risk map, superimpose the wear rate contour lines on the eddy working condition map, and delineate low-risk, medium-risk, and high-risk areas.

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