A method for evaluating fatigue cumulative damage of a center pass cable drill pipe

Abstract

This invention provides a method for assessing fatigue cumulative damage of a central cable-through drill pipe, relating to the field of engineering safety assessment technology. The method includes the following steps: acquiring wear morphology information of the inner wall of the cable-through hole of the central cable-through drill pipe; performing spatial correlation and evolution analysis on the wear morphology information at different stages; establishing a wear evolution history model characterizing the changing law of wear defects on the cable-through hole wall during service; acquiring rotational state information and alternating load information of the central cable-through drill pipe during operation; determining the trajectory of load direction changes during drill pipe rotation based on the rotational state information and alternating load information; and realizing spatiotemporal coupling analysis of structural geometric defects and dynamic alternating loads based on the distribution location of wear defects and the trajectory of load direction changes, revealing the intrinsic mechanical mechanism of the dynamic transfer of fatigue crack initiation points with the drill pipe's rotation and revolution, and accurately identifying the most dangerous dynamic load-bearing surface to avoid assessment blind spots.

Description

Technical Field

[0001] This invention relates to the field of engineering safety assessment technology, and more specifically, to a method for assessing fatigue cumulative damage of a center-through-cable drill pipe. Background Technology

[0002] With the increasing depth of coal mining and the growing complexity of underground geological conditions, drilling projects such as gas drainage, geological water exploration, and structural exploration play a core role in coal mine safety production. The center-connected drill pipe, as a key drilling equipment that integrates mechanical drilling, signal transmission, and bottom hole parameter measurement, can effectively solve the problem of underground information silos and realize the real-time transmission of drilling measurement data due to its integrated communication cable. It has been widely used in major mining areas across China.

[0003] However, the following prominent problems exist in the fatigue cumulative damage assessment technology for center-through-the-wire drill pipes:

[0004] (1) Most of the existing fatigue assessment methods are based on the nominal stress method or the local stress-strain method. They often simplify the drill pipe as an ideal elastic body or only consider a single mechanical load spectrum, ignoring the geometric evolution of wear defects on the inner wall of the cable hole during actual rotary drilling.

[0005] (2) Existing technologies are unable to accurately characterize the spatiotemporal coupling relationship between wear defects and dynamic alternating load direction during drill pipe rotation, and cannot capture the dynamic migration phenomenon of fatigue danger area with drill pipe rotation and revolution, thus severing the intrinsic connection between wear morphology evolution and dynamic load response. This results in the inability to accurately locate the maximum damage accumulation area that changes continuously with the rotation process, thus causing a large deviation between the prediction results and the actual remaining life.

[0006] Therefore, there is an urgent need for a method to assess the cumulative fatigue damage of center-through-cable drill pipes. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention is proposed. A first aspect of this invention provides a method for assessing cumulative fatigue damage in a center-through-the-cable drill pipe, comprising the following specific steps: acquiring wear morphology information of the inner wall of the cable-through hole in the center-through-the-cable drill pipe; performing spatial correlation and evolution analysis on wear morphology information at different stages; and establishing a wear evolution history model characterizing the changing law of wear defects on the cable-through hole wall during service.

[0008] The rotational state information and alternating load information of the central cable drill pipe during operation are obtained, and the trajectory of the change in load direction during the rotation of the drill pipe is determined based on the rotational state information and alternating load information.

[0009] Based on the distribution location of the wear defects and the trajectory of the load direction, the changes in the load area corresponding to the wear defects under different rotation states are determined, and the migration trajectory of the fatigue danger area of ​​the cable hole wall as the drill pipe rotates is obtained.

[0010] Based on the migration trajectory of the fatigue danger area, the cumulative damage of each danger area during different rotational load cycles is determined, and the fatigue damage state of the central cable drill rod distributed along the cable hole wall is obtained.

[0011] The current maximum damage area of ​​the central cable drill pipe is determined based on the fatigue damage state, and the remaining safe tripping and tripping counts of the central cable drill pipe are predicted by combining historical service cycle information.

[0012] Preferably, the acquisition of the wear morphology information of the inner wall of the cable passage hole of the central cable-passing drill rod includes:

[0013] Using non-destructive testing equipment suitable for internal borehole inspection, the inner wall of the cable hole of the central cable drill rod is scanned axially and circumferentially to obtain three-dimensional inspection data that can characterize the changes in borehole wall thickness, local wear areas, and surface defect distribution.

[0014] Spatial fusion is performed on data obtained from different detection methods that have differences in spatial resolution and incomplete detection areas to obtain wear morphology information.

[0015] Preferably, the establishment of the wear evolution history model includes:

[0016] Non-destructive testing was performed on the inner wall of the cable hole of the central cable drill rod at different service cycle stages to obtain the three-dimensional morphological data of the hole wall corresponding to each testing stage. There are circumferential angle offsets, axial position deviations and missing local testing areas among the wear morphological data obtained at different times.

[0017] Local geometric features with stable evolution characteristics are extracted from the wear regions at each stage. These local geometric features include the maximum wear region, non-uniform wear boundary, continuous wear strip, and original structure features of the hole wall. Spatial correspondence between wear regions at different detection stages is established.

[0018] Based on the established spatial correspondence, circumferential phase correction and axial position matching are performed on the wear morphology data of different service stages, so that the wear area at different time points is in a unified spatial description system.

[0019] Based on the changes in location, depth, and extent of wear areas during each service stage, a time-series correlation was established for wear defects in the cable hole wall to obtain the spatial variation patterns of wear defects from initial formation, expansion, to stable evolution. A historical model of wear evolution was then established to characterize the migration direction and expansion trend of the wear area.

[0020] Preferably, the acquisition of rotational state information and alternating load information during the operation of the central cable drill pipe includes:

[0021] The drilling measurement and control system installed in the drill string operation system acquires the rotational speed, attitude, and motion parameters of the drill pipe during rotation, and the ground load monitoring device acquires information on the changes in axial load and torsional load during drilling.

[0022] By unifying the time reference for downhole condition information and surface load information that have time response differences, the rotational load change process can be synchronously correlated with the wear evolution state at different service stages.

[0023] Preferably, the load change states include:

[0024] During the operation of the central cable-guided drill pipe, rotational parameters such as drill pipe speed, torque, well inclination angle, and azimuth angle are collected. At the same time, information on the changes in axial load and torsional load during the surface drilling process is acquired. The operating parameters from different sources are synchronized in time to form dynamic load state data that reflects the actual service process of the drill pipe.

[0025] The variation of load direction with rotation is analyzed, and the correspondence between the change of rotational load direction and the wear evolution history model is established to associate the wear state formed at different service stages with the actual load process experienced.

[0026] Preferably, the migration trajectory includes:

[0027] The wear evolution history model of the cable hole wall is correlated with the rotational load cycle process during the operation of the central cable drill pipe, so that the wear state corresponding to different service stages matches the actual load state.

[0028] Based on the geometric evolution of the wear area of ​​the cable hole wall at different service stages, the local bearing structure of the drill pipe is dynamically updated. The influence of wear depth change, defect propagation direction and local section weakening degree on the stress distribution of the hole wall is analyzed, and the local stress concentration change law corresponding to the wear area under different wear evolution stages is obtained.

[0029] By combining the periodic variation characteristics of the load direction during drill pipe rotation, the load differences of the same wear defect under different rotation states and different service stages are analyzed to determine the spatial variation process of the transfer of local stress concentration areas.

[0030] Based on the positional changes of fatigue danger zones at different time stages, a correspondence between wear evolution state and danger zone migration is established, and the law of continuous migration of danger zones under the combined effects of wear expansion, load direction change and local damage accumulation is obtained.

[0031] Based on the spatial change process of the dangerous area, a fatigue dangerous area migration trajectory is formed with the number of service cycles and the wear evolution stage as common characterization parameters.

[0032] Preferably, the cumulative damage includes:

[0033] Based on the migration trajectory of the fatigue danger zone, the positional change of the danger zone with the rotational load cycle and wear evolution process is used as the damage calculation area;

[0034] By combining the stress change characteristics of the corresponding area during the migration of the dangerous area, fatigue damage accumulation calculation is performed on the alternating loads at different locations and different service stages. The fatigue damage distribution of the cable hole wall is obtained by spatial correlation according to the actual migration process of the dangerous area.

[0035] Preferably, the remaining safe tripping times for the cable-stayed drill pipe in the prediction center include:

[0036] Based on the fatigue damage distribution in the cable hole wall space, the area with the highest damage level at the current stage and its corresponding spatial location are determined. Combined with the wear evolution history information, it is determined whether the current danger zone is in a state of continuous expansion or migration.

[0037] By combining the historical number of tripping and running cycles of the drill pipe, the cumulative service time, and the fatigue damage development trend, the damage growth pattern during future service is predicted, and the remaining safe tripping and running cycles of the center cable drill pipe are obtained.

[0038] Preferably, a multi-source state data association model is established, consisting of wear morphology information, rotational load information, and historical operating cycle information;

[0039] Based on the multi-source state data association model, wear defect evolution characteristics and fatigue damage change characteristics are extracted, and the correspondence between wear state and fatigue damage accumulation is established.

[0040] The remaining safe tripping and tripping counts for the cable-stayed drill pipe in the prediction center include predictions of fatigue damage development trends based on the current detection status and the corresponding relationship.

[0041] Preferably, a damage prediction model is established based on wear evolution data and fatigue damage data at different service stages to analyze the expansion of wear area, changes in dangerous area, and fatigue damage accumulation process.

[0042] The damage prediction model is updated by combining the real-time drill pipe operating status information, and the remaining safe tripping and tripping counts of the center cable drill pipe are determined based on the updated model.

[0043] A second aspect of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that: when the processor executes the computer program, it implements the steps of the above-described method for assessing fatigue cumulative damage of a center-through-cable drill pipe.

[0044] Compared with existing technologies, the fatigue cumulative damage assessment method for center-connected drill pipes provided by this invention acquires the rotational state information and alternating load information during drill pipe operation, and determines the trajectory of load direction changes during drill pipe rotation. This achieves a dynamic mapping of macroscopic motion parameters to microscopic stress states, overcoming the shortcomings of traditional static equivalent loads that cannot reflect complex alternating stress states downhole. It provides a high temporal resolution and high spatial accuracy real dynamic load spectrum for fatigue damage calculation. By spatially superimposing the distribution location of wear defects with the trajectory of load direction changes, it determines the changes in the loaded area corresponding to wear defects under different rotational states and obtains the migration trajectory of fatigue danger areas. This enables spatiotemporal coupling analysis of structural geometric defects and dynamic alternating loads, revealing the intrinsic mechanical mechanism of the dynamic transfer of fatigue crack initiation points with drill pipe rotation and revolution, and accurately locking the most dangerous dynamic load surface to avoid assessment blind spots. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings:

[0046] Figure 1 This is a flowchart of a method for assessing cumulative fatigue damage to a center-through-cable drill pipe according to an embodiment of the present invention. Detailed Implementation

[0047] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0048] As mentioned in the background section, most existing fatigue assessment methods are based on the nominal stress method or the local stress-strain method. These methods often simplify the drill pipe as an ideal elastic body or only consider a single mechanical load spectrum, ignoring the geometric evolution of wear defects on the inner wall of the cable hole during actual rotary drilling. Furthermore, existing technologies cannot accurately characterize the spatiotemporal coupling relationship between wear defects and the direction of dynamic alternating loads during drill pipe rotation. They cannot capture the dynamic migration of fatigue-prone areas as the drill pipe rotates and revolves, thus severing the intrinsic connection between wear morphology evolution and dynamic load response. This results in the inability to accurately locate the maximum damage accumulation area that changes continuously during rotation, leading to a significant deviation between the predicted results and the actual remaining service life.

[0049] Therefore, there is an urgent need for a method for assessing the cumulative fatigue damage of center-connected drill pipes.

[0050] Figure 1 A flowchart of a fatigue cumulative damage assessment method for a center-through-cable drill pipe according to an embodiment of the present invention is shown, including the following specific steps:

[0051] S1: Obtain the wear morphology information of the inner wall of the cable passage hole of the central cable passage drill rod, perform spatial correlation and evolution analysis on the wear morphology information of different stages, and establish a wear evolution history model that characterizes the change law of wear defects on the cable passage hole wall with the service process.

[0052] In step S1, a non-destructive testing device suitable for internal hole inspection is used to perform axial and circumferential scanning on the inner wall of the cable hole of the central cable drill rod to obtain three-dimensional inspection data that can characterize the hole wall thickness variation, local wear area and surface defect distribution.

[0053] Spatial fusion is performed on data obtained from different detection methods that have differences in spatial resolution and incomplete detection areas to obtain wear morphology information.

[0054] Non-destructive testing was performed on the inner wall of the cable-through hole of the center cable-through drill rod at different service cycles to obtain the three-dimensional morphological data of the hole wall corresponding to each testing stage. There were circumferential angle offsets, axial position deviations and missing local testing areas among the wear morphological data obtained at different times.

[0055] Local geometric features with stable evolution characteristics are extracted from the wear regions at each stage. These local geometric features include the maximum wear region, non-uniform wear boundary, continuous wear strip, and original structure features of the hole wall. Spatial correspondence between wear regions at different detection stages is established.

[0056] Based on the established spatial correspondence, circumferential phase correction and axial position matching are performed on the wear morphology data of different service stages, so that the wear area at different time points is in a unified spatial description system.

[0057] Based on the changes in location, depth, and extent of wear areas during each service stage, a time-series correlation was established for wear defects in the cable hole wall to obtain the spatial variation patterns of wear defects from initial formation, expansion, to stable evolution. A historical model of wear evolution was then established to characterize the migration direction and expansion trend of the wear area.

[0058] Furthermore, in order to establish a wear evolution history model that can truly reflect the changing law of wear defects on the inner wall of the cable passage hole of the central cable-through drill pipe during service, it is considered that the central cable-through drill pipe is subjected to multiple factors such as drilling environment, downhole vibration, rotational load and mud erosion during actual service. The wear on the inner wall of the cable passage hole does not show a uniform growth law, but usually manifests as a non-uniform change process of preferential wear in local areas, gradual expansion of the wear area and continuous evolution of local defects.

[0059] If only the hole wall wear detection results obtained at a single moment are used as the basis for fatigue analysis, it can only reflect the current state and cannot describe the causes, development paths and future expansion trends of wear defects. This leads to the inability to accurately consider the structural degradation process in the subsequent fatigue damage calculation. By constructing a wear morphology correlation analysis method under multiple service stages and multiple spatial scales, discrete wear detection data obtained at different time points are transformed into a wear evolution history model with temporal continuity, providing a real and reliable data foundation for the subsequent dynamic migration analysis of fatigue danger areas.

[0060] Based on the actual service cycle of the central cable-through drill pipe, the inner wall of the cable-through hole is periodically inspected at different drilling times or cumulative working time nodes. During the inspection, an endoscopic three-dimensional scanning device, a laser contour detection device, or an ultrasonic array detection device is moved along the drill pipe axis and simultaneously scanned circumferentially around the central axis of the cable-through hole to obtain three-dimensional inspection data including the spatial coordinates of the hole wall, the amount of wall thickness change, the wear depth, and the distribution of surface defects.

[0061] Due to the narrow internal space of the drill pipe, the limited detection path, and the differences in spatial resolution of different detection equipment, the data obtained at different detection stages may have problems such as missing detection areas, local data noise, and inconsistent spatial coordinates. Before constructing the wear evolution history model, it is necessary to preprocess and spatially fuse the detection data from different sources.

[0062] The three-dimensional point cloud data obtained at different detection stages are subjected to coordinate normalization processing, and the detection data at each stage are transformed into a unified borehole wall cylindrical coordinate system. The axial coordinate is used to represent the position of the drill rod in the direction of length, the circumferential angular coordinate is used to represent the position of the wear area around the borehole wall in the circumferential direction, and the radial coordinate is used to represent the degree of material loss of the borehole wall.

[0063] In the spatial fusion process, the original structural features of the area of ​​the borehole wall without significant wear are first used as a stable reference area. By extracting local texture features, geometric edge features, and structural continuity features of the borehole wall, a spatial correspondence between different detection stages is established. Since the wear area changes continuously during the service of the drill pipe, while the original structural area changes relatively little, using a stable area as a spatial matching benchmark can reduce the matching error caused by wear development. The extraction of local geometric features is achieved in the following way: the spiral texture formed during the original processing of the borehole wall and far away from the wear area is used as a stable reference feature. The consistency of the local normal vectors of the point cloud is analyzed to determine whether the area belongs to the original unworn structure. At the same time, areas where the gradient amplitude of the wear depth field exceeds a set threshold are identified as non-uniform wear boundaries, and these boundary points are connected to form a contour to reflect the direction of defect expansion.

[0064] When establishing spatial correspondence, in addition to using stable regions for matching, the shape characteristics of the wear boundaries corresponding to adjacent stages are also used as constraints to improve the accuracy of registration. The constraint that the determinant of the transformation gradient is greater than zero is achieved by setting the condition that the local volume cannot be reversed in the deformation field. That is, it is required that in any tiny region, the transformation cannot cause the space to be flipped or folded, thereby ensuring that the spatial order of the wear regions remains consistent before and after registration, and avoiding the continuous evolution of mistakenly associating isolated wear pits as the same defect.

[0065] The first The wear morphology of the cable hole wall in each detection stage is represented as follows:

[0066] ;

[0067] in, The circumferential angle of the cable hole wall. This refers to the axial position. For the first Wear depth at the corresponding location in each detection stage.

[0068] ;

[0069] in, and These represent the spatial offsets in the circumferential and axial directions between different detection stages, respectively. For the first The first testing phase to the... Spatial coordinate transformation function for each detection stage; This represents the offset of the transformation in the circumferential angle, used to correct for circumferential angle deviations caused by rotational positioning errors of the detection equipment or the torsion of the drill rod itself. This indicates the offset in axial position, used to correct axial position deviations caused by axial advance errors of the detection equipment.

[0070] ;

[0071] and satisfy ,in, This serves as a stable reference area where no significant wear has occurred during adjacent testing phases. For the first Local geometric features of the stable reference region in each detection stage For the first Each detection stage is in coordinates The extracted local geometric feature vector is composed of the consistency of the point cloud normal vector at the location, the surface curvature, and the texture descriptor. The stable reference area determined to have no significant wear in adjacent testing phases The projected area on the plane has a wear depth variation that is less than a preset threshold, satisfying the spatial transformation requirement. It is locally invertible everywhere within the stable reference region, that is, the Jacobian determinant is always positive, ensuring that the corresponding geometric region does not flip or degenerate.

[0072] By ensuring that the determinant of the transformation gradient of the constraint space correspondence is greater than zero, the local spatial order of the hole wall is kept from being reversed during circumferential correction and axial matching of wear morphology at different stages. This avoids incorrect association of different wear areas due to wear area expansion, local data loss, or changes in the detection path.

[0073] Furthermore, after completing the spatial registration between different detection stages, feature extraction and evolution analysis are performed on the wear area. Considering that cable hole wall wear usually manifests as local groove wear, circumferential uneven wear, and continuous strip wear, parameters such as the location of maximum wear depth, wear boundary contour, length of continuous wear area, and wear area change are selected as the main evolution features. The maximum wear area is used to describe the location where the local structure is most severely weakened, the wear boundary is used to reflect the defect propagation direction, and the continuous wear strip is used to characterize the long-term wear path formed by the combined action of rotational load and contact friction. By performing correlation analysis on the feature parameters between different service stages, the spatial migration direction and expansion speed variation law of the wear area can be obtained.

[0074] Furthermore, to ensure that the wear evolution process corresponds to the actual service cycle, the service cycle number corresponding to the detection stage is used as the time dimension. The changes in the location, depth growth, and area expansion of the wear region at different stages are correlated over time. In the initial service stage, the location of the first appearance of the wear defect is determined, and the corresponding spatial coordinates are recorded. In subsequent detection stages, the wear depth changes within the same spatial region are compared to determine whether the region is in a state of continuous development. Simultaneously, the development direction of the wear defect is determined by analyzing the expansion of the wear boundary into the surrounding area. Through the above methods, multiple discrete detection results are converted into a continuous evolution process, thereby forming a historical evolution trajectory that can describe the generation, expansion, and stable development of wear defects.

[0075] After completing the spatial correlation of wear morphology in adjacent detection stages, the first... The wear depth of the first detection stage is mapped to the second. A unified spatial description system for each detection stage was obtained.

[0076] ;

[0077] The evolution increment of wear defects between adjacent service stages is defined as:

[0078] ;

[0079] in To make the first Stage wear depth data after spatial transformation After correction, it is mapped to the first The results of the stage coordinate system, that is, the wear depth values ​​of two stages that can be directly compared under a unified spatial description system, The wear depth increment is the spatial location between two adjacent detection stages. A positive value indicates continued wear development, while a zero or negative value indicates no wear expansion or data fluctuation. The wear boundary is represented as:

[0080] ;

[0081] in, For the first The wear boundary contour line of each detection stage is formed by all conditions where the wear depth is exactly equal to the judgment value. Composed of points, For a pre-set wear depth judgment threshold, when the wear depth at a certain location... Greater than The location is determined to be within the wear area, and is smaller than... This refers to the external area that is either unworn or has negligible wear.

[0082] The normal evolution rate of the wear boundary between adjacent service phases satisfies:

[0083] ;

[0084] in, and These represent the cumulative number of service cycles corresponding to two adjacent testing phases. The wear depth represents the spatial gradient of the surface along the wall of the cable passage. For the wear boundary in coordinate The evolution rate along the boundary normal direction; a positive value indicates that the wear boundary expands outward, and a negative value indicates that it contracts inward. and The first The and the first The cumulative number of drill pipe service cycles corresponding to each testing phase, i.e., the total number of trips and trips completed by the drill pipe in each phase. Wear depth field exist The gradient vector at each point on the plane points in the direction of the fastest increase in wear depth.

[0085] The continuous evolution of the wear boundary during service is described by the following equation:

[0086] ;

[0087] in, To the number of service cycles The level set function is a time parameter. The function value at any position on the plane represents the sign distance of that point relative to the wear boundary. For level set functions in Spatial gradient on a plane Indicates the number of service cycles. Wear boundary at time, Indicates the interior of the wear area. Indicates the area outside the wear zone.

[0088] Therefore, the discrete wear boundaries obtained at different detection stages are transformed into wear evolution boundaries that change continuously with the number of service cycles, and then... The sign and magnitude of the value represent the direction and speed of the wear defect's expansion at the corresponding location, respectively.

[0089] Furthermore, after establishing the wear evolution history model, it serves as the dynamic geometric input in the subsequent fatigue analysis process, enabling the fatigue calculation model to continuously update the local structural state of the drill pipe according to the actual service stage. Compared with the traditional method of using a fixed defect model for fatigue analysis, this fully considers the effects of the gradual deepening of wear, the continuous expansion of the defect range, and the continuous decline of local bearing capacity during the long-term service of the drill pipe. This makes the subsequent identification of fatigue danger areas more consistent with actual working conditions. By establishing the wear evolution history model, it is also possible to achieve data comparison and analysis between different service states of the drill pipe, providing a basis for judging abnormal wear of the drill pipe, predicting the development trend of defects, and formulating maintenance cycles.

[0090] This enables a shift from single-time-node wear detection to multi-stage continuous evolution analysis, transforming the wear state of cable hole walls from static detection results into a dynamic evolution model. This not only improves the completeness of wear defect characterization but also provides an accurate data foundation for subsequent load direction matching, hazardous area migration analysis, and fatigue cumulative damage calculation.

[0091] The wear evolution history model refers to establishing a dynamic model that reflects the changing patterns of wear defects during service by spatially matching and temporally correlating wear morphology data of the inner wall of the cable-through borehole of the central cable-through drill pipe at different service stages. This model not only describes the current wear state but also characterizes the changes in the location, depth, and extent of the wear area. By spatially correcting the three-dimensional inspection data of the borehole wall obtained at different service cycles, the wear areas at each stage are placed in a unified coordinate system. Corresponding relationships are established based on the location, morphology, and size changes of the wear area. Combined with the changing patterns of wear depth and extent at different stages, the model analyzes the evolution of wear defects from their generation and development to stable expansion, thus obtaining the historical trajectory of the wear area's changes over service time. By establishing the wear evolution history model, a continuous description of the wear state of the cable-through borehole wall can be achieved, providing dynamic wear state data for subsequent load analysis, fatigue hazard area migration, and fatigue damage accumulation calculation, thereby improving the accuracy of fatigue damage assessment for the central cable-through drill pipe.

[0092] S2: Obtain the rotational state information and alternating load information of the central cable drill pipe during operation, and determine the trajectory of the load direction change during the rotation of the drill pipe based on the rotational state information and alternating load information.

[0093] In step S2, the rotational speed, attitude, and motion parameters of the drill pipe during rotation are obtained by the measurement while drilling device installed in the drill string operating system, and the axial load and torsional load change information during drilling is obtained by the ground load monitoring device.

[0094] By unifying the time reference for downhole condition information and surface load information that have time response differences, the rotational load change process can be synchronously correlated with the wear evolution state at different service stages.

[0095] Furthermore, in order to accurately obtain the dynamic change law of the direction of rotational load during the operation of the central cable drill pipe, it is considered that the central cable drill pipe is not always subjected to a fixed direction load during the actual drilling process, but rather to an alternating load state with continuously changing spatial direction under the combined influence of factors such as rotational motion, wellbore trajectory changes, and drilling parameter fluctuations.

[0096] If only fixed-direction axial loads or torsional loads in traditional fatigue analysis methods are used as input conditions, it is impossible to truly reflect the changes in the circumferential regions of the cable hole wall under periodic loads during the rotation of the drill pipe. This leads to a deviation between the wear area and the actual load state, reducing the accuracy of fatigue hazard identification. By acquiring the rotational state information and alternating load information of the drill pipe during operation, and establishing a dynamic trajectory model of the load direction changing over time, the spatial motion state of the drill pipe during actual service corresponds to the load process, providing accurate load boundary conditions for subsequent wear area load analysis and fatigue hazard migration calculation.

[0097] The central cable-operated drill pipe system acquires rotational state information reflecting the spatial motion of the drill pipe. This rotational state information includes drill pipe rotation speed, rotational angular velocity, well inclination angle, azimuth angle, drill pipe attitude angle, and drill string motion parameters. These parameters describe the drill pipe's attitude changes in the downhole space and the spatial positional relationships at different time points during rotation. Drill pipe rotation speed determines the rotational load cycle frequency, rotational angular velocity determines the circumferential speed of the drill pipe, well inclination angle and azimuth angle describe the directional changes of the drill pipe axis relative to the wellbore spatial coordinate system, and drill pipe attitude parameters establish the transformation relationship between the drill pipe's local coordinate system and the external spatial coordinate system.

[0098] Meanwhile, the load monitoring equipment installed in the ground drilling system acquires information on alternating loads during the operation of the drill pipe. The ground drilling rig load monitoring system collects information on axial drilling pressure changes, torque changes, and load fluctuations during the lifting and lowering process. By setting the sampling time interval, the acquired load data can reflect the periodic changes in the actual operation of the drill pipe. Axial load mainly affects the axial compression and tension of the drill pipe, while torsional load mainly affects the circumferential shear stress distribution of the drill pipe. The combined effect of the two can lead to a complex alternating stress state in the local area of ​​the cable-passing hole wall.

[0099] Because downhole measurement-while-drilling data and surface load monitoring data come from different sources, they often have problems such as different sampling frequencies, time delays, and data synchronization errors. To unify the time reference for data from different sources, key events in the drill pipe operation process are used as time synchronization reference points, such as the start of drill pipe rotation, the moment of drilling speed change, or the moment of load change. The downhole state data and surface load data are corrected by time series matching methods so that each rotation state parameter can correspond to the actual load application state, and each rotation load cycle of the drill pipe has corresponding spatial motion information.

[0100] Furthermore, after obtaining the synchronized rotational state data and load data, a model of the change in the rotational load direction of the drill pipe is established. A local reference coordinate system is established based on the drill pipe's own coordinate system, where the axial direction is taken as the length direction of the drill pipe, the radial direction is taken as the normal direction of the cable passage hole wall, and the circumferential direction is taken as the rotation direction of the drill pipe. Based on the relationship between the well inclination angle, azimuth angle, and the rotation angle of the drill pipe, the axial load and torsional load obtained from the ground are converted into the local coordinate system of the drill pipe to obtain the equivalent load direction acting on the cable passage hole wall at different time points.

[0101] During the load direction conversion process, considering that the same spatial position will experience loads in different directions as the rotation angle changes during the drill pipe rotation, a functional relationship between the load direction and the rotation angle is established. The current rotation angle position of the drill pipe is calculated based on the drill pipe rotation angular velocity and the cumulative rotation time. The projection position of the load direction on the circumferential direction of the cable passage hole wall at any given time is determined by combining the drill pipe attitude parameters. By continuously calculating the load direction corresponding to different time nodes, the motion trajectory of the load direction changing along the circumferential direction of the cable passage hole wall can be obtained.

[0102] Furthermore, to ensure that the trajectory of load direction changes can be correlated with the wear evolution history model, the wear state corresponding to different service stages is matched with the load application process during the same period. Specifically, after establishing the wear evolution history model, based on the number of service cycles corresponding to the detection stage, the rotation state and load change data during the operation of the drill pipe in that stage are extracted, and the spatial location of the wear area is mapped to the load application area at the corresponding rotation angle. This allows us to determine the main load direction, number of load cycles, and load change range experienced by a certain wear defect during its formation process, thereby establishing the correlation between the wear defect formation process and the actual load application process.

[0103] Furthermore, when considering complex drilling conditions, the direction of the rotational load is not a regular, periodic change as ideally possible due to factors such as drill pipe vibration, wear, and wellbore constraints. Instead, it may exhibit local disturbances and random variations. During the load direction trajectory establishment process, continuously acquired operational data is filtered and outlier corrected to remove unreasonable data points caused by sensor fluctuations or instantaneous impacts, while retaining the load fluctuation characteristics that accurately reflect the changes in the drill pipe's operating state. Specifically, a sliding window smoothing method can be used to process high-frequency disturbance signals, and statistical analysis can be used to obtain the range of load direction changes, ensuring that the final load trajectory model can account for both long-term trends and local variations.

[0104] This approach shifts the focus from traditional fixed load analysis to dynamic rotating load direction analysis, enabling a unified description of the rotational motion, spatial attitude changes, and alternating load processes of the center-cable drill pipe during actual service. The established load direction change trajectory not only reflects the load variation patterns of the drill pipe under different rotational states but also provides accurate input conditions for subsequent wear zone load state analysis, identification of local stress concentration areas, and establishment of fatigue hazard migration trajectories. This improves the consistency between the fatigue cumulative damage assessment results and the actual service condition of the center-cable drill pipe.

[0105] S3: Based on the distribution location of wear defects and the trajectory of load direction, determine the changes in the load area corresponding to wear defects under different rotational states, and obtain the migration trajectory of the fatigue danger area of ​​the cable hole wall as the drill pipe rotates.

[0106] In step S3, rotational state parameters such as drill pipe speed, torque, well inclination angle, and azimuth angle are collected during the operation of the central cable drill pipe. At the same time, information on the changes in axial load and torsional load during the surface drilling process is obtained. The operating parameters from different sources are synchronized in time to form dynamic load state data that reflects the actual service process of the drill pipe.

[0107] The variation of load direction with rotation is analyzed, and the correspondence between the change of rotational load direction and the wear evolution history model is established to associate the wear state formed at different service stages with the actual load process experienced.

[0108] The wear evolution history model of the cable borehole wall is correlated with the rotational load cycle process during the operation of the central cable drill pipe, so that the wear state corresponding to different service stages matches the actual load state.

[0109] Based on the geometric evolution of the wear zone of the cable borehole wall at different service stages, the local bearing structure of the drill pipe is dynamically updated. The influence of wear depth changes, defect propagation direction and local cross-sectional weakening degree on borehole wall stress distribution is analyzed, and the local stress concentration variation law corresponding to the wear zone under different wear evolution stages is obtained.

[0110] By combining the periodic variation characteristics of the load direction during drill pipe rotation, the load differences of the same wear defect under different rotation states and different service stages are analyzed to determine the spatial variation process of the transfer of local stress concentration areas.

[0111] Based on the positional changes of fatigue danger zones at different time stages, a correspondence between wear evolution state and danger zone migration is established, revealing the law of continuous migration of danger zones under the combined effects of wear expansion, load direction change, and local damage accumulation.

[0112] Based on the spatial change process of the danger zone, a fatigue danger zone migration trajectory is formed with the number of service cycles and the wear evolution stage as common characterization parameters.

[0113] Furthermore, to accurately determine the dynamic migration pattern of the fatigue danger zone in the center through-hole drill pipe during actual service, considering the obvious temporal coupling characteristics between the development process of wear defects in the through-hole wall and the rotational load process, existing fatigue analyses typically use the defect morphology obtained at a single moment as a fixed boundary condition and assume that the danger zone is always located at the maximum wear position. However, they do not consider the continuous expansion of wear defects during long-term service and the influence of drill pipe rotation causing the same wear area to experience different load states. Even if the current wear depth of the through-hole wall remains unchanged, the corresponding local bearing capacity and danger zone may migrate with the wear evolution process and the change of load direction. As a result, using a fixed danger zone for fatigue analysis cannot truly reflect the actual damage development process of the center through-hole drill pipe. By correlating the wear evolution history model with the rotational load direction change trajectory, the identification of the danger zone is transformed from static position judgment to dynamic migration process analysis, thereby establishing a migration trajectory that can reflect the continuous evolution pattern of the fatigue danger zone.

[0114] The effectiveness of coupling is determined by calculating the square of the inner product of the unit vector of the wear boundary normal and the load direction, and comparing it with a set direction alignment threshold. When the value is greater than the threshold, i.e., the load direction and the wear propagation direction tend to be consistent, it is considered a high coupling state, in which case the load will accelerate the propagation of the wear boundary.

[0115] Under high coupling conditions, a local stress concentration factor growth model proportional to the wear propagation rate is employed: the fatigue danger zone is no longer statically determined based on the stress distribution at the current wear boundary, but rather the stress assessment location is shifted forward along the wear boundary normal by a distance related to the wear propagation rate and the degree of coupling, and the equivalent stress is recalculated at the shifted location. By repeatedly executing this dynamic advancement process, the phenomenon of the danger zone migrating to the unworn area in advance when the load continues to act along the wear path can be described, thus obtaining the fatigue danger zone migration trajectory that continuously changes with the number of service cycles and wear evolution.

[0116] Based on the wear evolution history model, the evolution characteristics of wear areas, such as location, wear depth, and expansion boundary, at different service stages are extracted. The load direction change trajectory is also used to extract the load direction change information of each rotational load cycle within the corresponding service stage. Using the number of service cycles as a unified correlation parameter, the wear state of each stage is matched with the load action process of the same period, so that the wear defects formed in different stages correspond to the actual load action history. After completing the time-series correlation, the local bearing area of ​​the cable hole is updated according to the geometric changes of the wear area, and the changes in the load position of the wear area under different rotational states are analyzed in combination with the load direction change.

[0117] Let any spatial position of the cable passage wall be:

[0118] ;

[0119] The number of service cycles obtained by the position Wear boundary evolution rate and wear propagation normal:

[0120] ;

[0121] in, The circumferential angle on the unfolded plane of the cable hole wall and axial position The spatial coordinate vector formed This represents the current cumulative number of service cycles. The number of service cycles is The normal evolution rate of the wear boundary at position x. For the wear boundary at location The unit normal vector at that location points from the inside of the worn area to the unworn area. This is the directional coupling factor, equal to the product of the wear propagation rate and the directional consistency factor. It characterizes the degree to which the current load drives the wear propagation path. The dot product of two unit vectors is obtained from the time step. The corresponding unit vector of the load direction Define the directional coupling between the wear propagation direction and the load application direction as:

[0122] ;

[0123] Among them, when And when the wear propagation direction tends to be consistent with the load direction, An increase indicates that the current load is continuing to act along the expansion direction of the existing wear boundary; when the two directions are nearly orthogonal, The decrease indicates that the current load has a weaker effect on the continuation of the existing wear propagation path.

[0124] Based on the directional coupling, the local stress field under the current rotational state is evolved and corrected:

[0125] ;

[0126] in, This represents the local stress state of the cable-passing hole wall during the current service phase. This represents the local stress state obtained after spatial propulsion along the direction of wear boundary expansion. This indicates that the number of service cycles is , time is At that time, the position of the cable hole wall The local stress tensor or equivalent stress value at a given point is obtained through finite element analysis or analytical calculation. For small increment steps of the number of service cycles, The term represents the spatial propagation distance of the stress evaluation point along the normal direction of the wear boundary under coupling effect.

[0127] The stress evaluation location is updated along the actual evolution direction of the wear boundary, so that the determination of the subsequent fatigue hazard area is no longer limited to the current maximum wear point, but can reflect the process of the load driving the hazard location to move in advance along the existing wear propagation path.

[0128] When the wear zone expands and causes a decrease in local load-bearing capacity, the location of the dangerous zone is adjusted synchronously; when the load direction changes and causes a decrease in stress in the original dangerous zone while the load on adjacent areas increases, the location of the dangerous zone is redefined.

[0129] Furthermore, the locations of hazardous areas obtained at each service stage are continuously correlated in chronological order, and the migration paths of hazardous areas in the circumferential, axial, and service cycles are recorded. Finally, a fatigue hazardous area migration trajectory is formed, which is jointly described by the number of service cycles, spatial location, and wear evolution stage. This realizes the transformation of area identification from fixed identification to continuous migration identification, so that subsequent fatigue damage calculations can be dynamically updated according to the actual evolution process of the hazardous area, and improve the consistency between fatigue hazardous area identification results and actual service conditions.

[0130] S4: Based on the migration trajectory of the fatigue danger area, determine the cumulative damage corresponding to each danger area during different rotational load cycles, and obtain the fatigue damage state of the central cable drill rod spatially distributed along the cable hole wall.

[0131] In step S4, based on the migration trajectory of the fatigue danger area, the positional change of the danger area with the rotational load cycle and wear evolution process is used as the damage calculation area.

[0132] By combining the stress change characteristics of the corresponding area during the migration of the dangerous area, fatigue damage accumulation calculation is performed on the alternating loads at different locations and different service stages. The fatigue damage distribution of the cable hole wall is obtained by spatial correlation according to the actual migration process of the dangerous area.

[0133] Furthermore, in order to accurately assess the cumulative state of fatigue damage during the long-term service of the central cable drill pipe, considering that the fatigue danger area is not fixedly distributed but constantly migrates with the combined action of wear evolution and rotational load, traditional fatigue accumulation analysis usually takes the maximum danger point as the fixed damage calculation object and applies all cyclic loads to the same location for cumulative calculation, without considering the local damage redistribution phenomenon caused by the continuous shift of the danger area during service.

[0134] Fatigue damage calculation employs a nonlinear cumulative model based on continuum damage mechanics. Under each stress cycle, the equivalent stress amplitude is first calculated based on the local stress tensor of the hazardous area, taking into account the influence of the mean stress. The equivalent stress amplitude, along with the cumulative damage value at the current point, is substituted into the damage evolution equation to obtain the damage increment caused by this cycle, which is then superimposed on the historical damage at that location. When the hazardous area migrates, the damage value at the original location is retained, while the damage value at the new location continues to accumulate on top of the existing value, forming a fatigue damage distribution field that continuously evolves with spatial location and service time across the entire cable hole wall. This realistically depicts the process of damage transfer and redistribution as the hazardous area migrates.

[0135] When the danger zone has moved to a new location, traditional methods still accumulate damage based on the original danger point, which can easily lead to an overestimation of local damage and an underestimation of damage in the newly formed danger zone, reducing the accuracy of fatigue assessment results. Using the migration trajectory of the danger zone as the spatial basis for fatigue damage accumulation allows fatigue damage to be updated synchronously with the migration process of the danger zone, achieving continuous spatial accumulation of fatigue damage.

[0136] Based on the migration trajectory of the danger zone, the entire service process is divided into multiple continuous migration phases, and the spatial location range of the danger zone in each phase is determined. Subsequently,

[0137] Based on the load state corresponding to the rotational load cycle process in different migration stages, fatigue damage calculation is performed on each local area within the danger zone, and the local damage value formed in each stage is recorded. When the danger zone migrates, the cumulative damage of the original danger zone is retained as historical damage, and damage calculation continues in the new danger zone. The damage transmission relationship between adjacent stages is established according to the actual migration path of the danger zone, so that fatigue damage can accumulate continuously along the migration direction of the danger zone, rather than being limited to a fixed spatial location.

[0138] Furthermore, based on the damage accumulation results during the migration of dangerous areas, a spatial correlation analysis is performed on the entire cable hole wall to obtain the fatigue damage degree of each area under different service stages, and to form a spatial fatigue damage distribution state covering the entire cable hole wall.

[0139] This method avoids the local damage bias caused by the traditional method of accumulating fixed danger points, and enables the fatigue damage distribution to truly reflect the damage evolution pattern during the migration of dangerous areas, thus providing a more accurate damage basis for subsequent life prediction.

[0140] S5: Determine the current maximum damage area of ​​the center cable drill pipe based on the fatigue damage status, and predict the remaining safe tripping and tripping times of the center cable drill pipe by combining historical service cycle information.

[0141] In step S5, based on the fatigue damage distribution of the cable hole wall space, the area with the highest damage level at the current stage and its corresponding spatial location are determined, and combined with the wear evolution history information, it is determined whether the current dangerous area is in a state of continuous expansion or migration.

[0142] By combining the historical number of tripping and running cycles of the drill pipe, the cumulative service time, and the fatigue damage development trend, the damage growth pattern during future service is predicted, and the remaining safe tripping and running cycles of the center cable drill pipe are obtained.

[0143] Furthermore, in order to improve the consistency between the predicted number of remaining safe trips and trips of the center cable drill pipe and the actual service status, considering that the fatigue hazard area has the characteristics of continuous migration and expansion during long-term service, the existing life prediction usually calculates the remaining life based on the current maximum damage location and assumes that subsequent damage will continue to accumulate at the location, without considering the situation where the hazard area has already migrated or is about to migrate to the adjacent area.

[0144] When predicting future damage growth, the spatial fatigue damage distribution field obtained at the current time step is taken as the starting point. It is assumed that subsequent service will continue to act according to the current wear evolution trend and load spectrum. The damage evolution equation is recursively calculated forward until the maximum damage value in the dangerous area reaches the material's critical damage threshold.

[0145] Meanwhile, in each recursive step, based on the established wear evolution history model and the migration law of the dangerous area, the spatial location and local stress concentration state of the dangerous area are updated synchronously, so that the life prediction is not fixed at the current maximum damage point, but tracks the damage development of the most dangerous position along the predicted migration path, and gives the remaining safe tripping and pulling times based on the moving dangerous point.

[0146] When the danger zone shifts, traditional life prediction still relies on the original danger zone for life estimation, which can easily cause the remaining life prediction results to deviate from the actual service state. By comprehensively analyzing the wear evolution history, the migration pattern of the danger zone, and the current fatigue damage state, the remaining life prediction can not only consider the current damage level, but also the future development trend of the danger zone, thereby improving the reliability of life prediction.

[0147] Based on the spatial fatigue damage distribution, the most severely damaged danger zone is identified. The migration trajectory of this danger zone is analyzed to determine if it is still in a continuous expansion phase. If the danger zone continues to develop along its predetermined migration direction, the future location and expansion trend of the danger zone are determined based on the wear evolution history model. Furthermore, considering historical service cycles, cumulative working time, and fatigue damage growth at each stage, the damage growth trend during subsequent service is continuously predicted. When the danger zone stabilizes, the remaining service capacity is predicted based on the current damage state. If the danger zone continues to migrate, service life is updated according to the migrated danger zone, and the remaining safe tripping / running count is dynamically adjusted.

[0148] Furthermore, based on the prediction results, the remaining safe tripping count for the central cable-stayed drill pipe and corresponding maintenance warning information are output, providing a basis for drill pipe repair, replacement, and service management. Through the above design, the transformation from static life prediction to dynamic life prediction is realized, enabling the life prediction results to be continuously updated as the dangerous area migrates and wear evolves, thereby improving the consistency between the fatigue life prediction results of the central cable-stayed drill pipe and the actual service condition.

[0149] Example 2

[0150] Figure 1 A flowchart of a fatigue cumulative damage assessment method for a center-through-cable drill pipe according to an embodiment of the present invention includes: establishing a multi-source state data association model composed of wear morphology information, rotational load information and historical operating cycle information;

[0151] Based on a multi-source state data association model, wear defect evolution characteristics and fatigue damage change characteristics are extracted, and a correspondence between wear state and fatigue damage accumulation is established.

[0152] The remaining safe tripping and tripping counts for the cable-stayed drill pipe in the prediction center include predictions of fatigue damage development trends based on the current monitoring status and corresponding relationships.

[0153] Damage prediction models are established based on wear evolution data and fatigue damage data at different service stages to analyze wear zone expansion, changes in dangerous areas, and the fatigue damage accumulation process.

[0154] By combining the real-time drill pipe operating status information, the damage prediction model is updated, and the remaining safe tripping and tripping counts of the center cable drill pipe are determined based on the updated model.

[0155] Furthermore, to improve the accuracy of the prediction results for the remaining safe tripping and tripping times of the center cable drill pipe, it is considered that the fatigue damage development of the center cable drill pipe during actual service is not determined by a single factor, but is jointly affected by the wear evolution of the cable hole wall, the change of rotational load, and the cumulative effect of historical service cycles.

[0156] Existing life prediction methods typically estimate life based solely on the defect state or a single fatigue damage parameter obtained from current detection, without considering the impact of wear defects gradually expanding during service and the continuous migration of dangerous areas on subsequent damage development. Therefore, they are prone to the problem of accurate current state assessment but large deviations in long-term life prediction. By establishing a multi-source state data association model composed of wear evolution state, rotational load state, and historical operating cycle information, state information from different sources and time scales can be uniformly associated, enabling the current damage state of the central cable drill pipe to correspond to the historical degradation process.

[0157] Based on the wear morphology information of the cable hole wall obtained at different service stages, the range of wear area expansion, wear depth change, migration of dangerous area and local structural degradation characteristics are extracted. Combined with the operating status information such as rotational speed, torque, axial load and number of tripping and running cycles obtained during the actual operation of the drill pipe, the correlation between wear state and fatigue damage state is established.

[0158] Among them, the correlation is not only used to describe the degree of damage to the drill pipe under the current service stage, but also to reflect the fatigue damage growth law corresponding to different wear evolution stages, so that fatigue damage evaluation can take into account the long-term degradation process of the structure.

[0159] Furthermore, based on wear evolution data and fatigue damage data corresponding to different service stages, the damage development process of the center cable drill pipe is analyzed. The focus is on the impact of changes in local bearing capacity after the wear area expands and the migration of dangerous areas on the fatigue damage accumulation rate. By comparing the correspondence between wear state changes and fatigue damage growth under different service stages, the stage-specific change law of damage development of the center cable drill pipe is determined. When an increase in the wear expansion rate of a certain area, continuous migration of dangerous areas, or a change in the fatigue damage growth rate is detected, the subsequent damage development trend is adjusted according to historical operating data, thereby avoiding the distortion of life prediction results caused by using a fixed damage growth law.

[0160] Furthermore, after obtaining the damage development pattern, the real-time collected drill pipe operating status information is used as a dynamic update parameter to revise the established damage prediction model. Based on the newly added rotational load cycles, wear state changes, and fatigue damage accumulation during the actual operation of the drill pipe, the damage development trend in the model is updated, so that the prediction results can be dynamically adjusted with the changes in the service status of the drill pipe. When there is a significant difference between the actual operating status and the historical damage development pattern, the subsequent damage growth trend is reassessed through real-time status information to improve the consistency between the prediction results of the remaining safe tripping times and the actual service situation.

[0161] This enables a shift from static life prediction based on the current state to dynamic life prediction based on the multi-source state evolution process. This allows the remaining safe tripping and tripping counts of the center cable drill pipe to depend not only on the current fatigue damage level, but also on the development trend of wear defects, the migration pattern of dangerous areas, and the impact of historical service cycles, thereby improving the accuracy and reliability of drill pipe service safety assessment.

[0162] The multi-source state data association model refers to the unified association of different types of state information acquired during the service of the central cable-stayed drill pipe, establishing a data model that comprehensively reflects the actual service state of the drill pipe. Considering that drill pipe fatigue damage is not caused by a single factor but is influenced by multiple factors such as wear state, rotational load, number of operating cycles, and service time, it is necessary to fuse and analyze data from different sources. This involves temporal and spatial matching of data on the wear morphology of the cable-stayed borehole inner wall, drill pipe rotation state, alternating load, and historical operating cycle data, ensuring that different types of data correspond to the same service stage and spatial location. By extracting key characteristic parameters from various data types, the correlation between wear defect changes, load application states, and fatigue damage evolution is established. By establishing the multi-source state data association model, a comprehensive description of the service state of the central cable-stayed drill pipe can be achieved, providing a complete data foundation for subsequent damage development analysis and remaining life prediction, and improving the reliability of fatigue damage assessment under complex service conditions.

[0163] The damage prediction model is an analytical model established based on historical service data and current inspection status of the center-cable drill pipe to predict future fatigue damage trends. By analyzing wear states, load processes, and fatigue damage variation patterns at different service stages, it establishes a correspondence between input states and damage development. Prediction samples are constructed based on wear morphology parameters, load variation parameters, and fatigue damage state data obtained at different service cycle stages. By analyzing wear area expansion, changes in dangerous areas, and damage accumulation patterns, the main characteristic parameters affecting drill pipe fatigue life are determined. Furthermore, the drill pipe status information obtained from current inspections is input into the damage prediction model to predict damage growth trends during future service. By establishing this model, it is possible to predict future damage development from the current damage state, allowing the remaining safe tripping and tripping counts for the center-cable drill pipe to be dynamically determined based on actual service status. This avoids errors caused by traditional methods that only evaluate based on fixed service cycles, improving the accuracy of drill pipe safety service capability assessment.

Claims

1. A method for assessing cumulative fatigue damage in a center-through-cable drill pipe, characterized in that, The specific steps include the following: The wear morphology information of the inner wall of the cable passage hole of the central cable passage drill rod is obtained, and the wear morphology information at different stages is spatially correlated and analyzed to establish a wear evolution history model that characterizes the change law of wear defects on the cable passage hole wall with the service process. The rotational state information and alternating load information of the central cable drill pipe during operation are obtained, and the trajectory of the change in load direction during the rotation of the drill pipe is determined based on the rotational state information and alternating load information. Based on the distribution location of the wear defects and the trajectory of the load direction, the changes in the load area corresponding to the wear defects under different rotation states are determined, and the migration trajectory of the fatigue danger area of ​​the cable hole wall as the drill pipe rotates is obtained. Based on the migration trajectory of the fatigue danger area, the cumulative damage of each danger area during different rotational load cycles is determined, and the fatigue damage state of the central cable drill rod distributed along the cable hole wall is obtained. The current maximum damage area of ​​the central cable drill pipe is determined based on the fatigue damage state, and the remaining safe tripping and tripping counts of the central cable drill pipe are predicted by combining historical service cycle information.

2. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 1, characterized in that, The acquisition of wear morphology information of the inner wall of the cable passage hole of the central cable-through drill rod includes: Using non-destructive testing equipment suitable for internal borehole inspection, the inner wall of the cable hole of the central cable drill rod is scanned axially and circumferentially to obtain three-dimensional inspection data that can characterize the changes in borehole wall thickness, local wear areas, and surface defect distribution. Spatial fusion is performed on data obtained from different detection methods that have differences in spatial resolution and incomplete detection areas to obtain wear morphology information.

3. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 2, characterized in that, The establishment of the wear evolution history model includes: Non-destructive testing was performed on the inner wall of the cable hole of the central cable drill rod at different service cycle stages to obtain the three-dimensional morphological data of the hole wall corresponding to each testing stage. There are circumferential angle offsets, axial position deviations and missing local testing areas among the wear morphological data obtained at different times. Local geometric features with stable evolution characteristics are extracted from the wear regions at each stage. These local geometric features include the maximum wear region, non-uniform wear boundary, continuous wear strip, and original structure features of the hole wall. Spatial correspondence between wear regions at different detection stages is established. Based on the established spatial correspondence, circumferential phase correction and axial position matching are performed on the wear morphology data of different service stages, so that the wear area at different time points is in a unified spatial description system. Based on the changes in location, depth, and extent of wear areas during each service stage, a time-series correlation was established for wear defects in the cable hole wall to obtain the spatial variation patterns of wear defects from initial formation, expansion, to stable evolution. A historical model of wear evolution was then established to characterize the migration direction and expansion trend of the wear area.

4. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 1, characterized in that, The acquisition of rotational state information and alternating load information during the operation of the central cable drill pipe includes: The drilling measurement and control system installed in the drill string operation system acquires the rotational speed, attitude, and motion parameters of the drill pipe during rotation, and the ground load monitoring device acquires information on the changes in axial load and torsional load during drilling. By unifying the time reference for downhole condition information and surface load information that have time response differences, the rotational load change process can be synchronously correlated with the wear evolution state at different service stages.

5. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 4, characterized in that, The load change states include: During the operation of the central cable-guided drill pipe, rotational parameters such as drill pipe speed, torque, well inclination angle, and azimuth angle are collected. At the same time, information on the changes in axial load and torsional load during the surface drilling process is acquired. The operating parameters from different sources are synchronized in time to form dynamic load state data that reflects the actual service process of the drill pipe. The variation of load direction with rotation is analyzed, and the correspondence between the change of rotational load direction and the wear evolution history model is established to associate the wear state formed at different service stages with the actual load process experienced.

6. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 1, characterized in that, The migration trajectory includes: The wear evolution history model of the cable hole wall is correlated with the rotational load cycle process during the operation of the central cable drill pipe, so that the wear state corresponding to different service stages matches the actual load state. Based on the geometric evolution of the wear area of ​​the cable hole wall at different service stages, the local bearing structure of the drill pipe is dynamically updated. The influence of wear depth change, defect propagation direction and local section weakening degree on the stress distribution of the hole wall is analyzed, and the local stress concentration change law corresponding to the wear area under different wear evolution stages is obtained. By combining the periodic variation characteristics of the load direction during drill pipe rotation, the load differences of the same wear defect under different rotation states and different service stages are analyzed to determine the spatial variation process of the transfer of local stress concentration areas. Based on the positional changes of fatigue danger zones at different time stages, a correspondence between wear evolution state and danger zone migration is established, and the law of continuous migration of danger zones under the combined effects of wear expansion, load direction change and local damage accumulation is obtained. Based on the spatial change process of the dangerous area, a fatigue dangerous area migration trajectory is formed with the number of service cycles and the wear evolution stage as common characterization parameters.

7. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 1, characterized in that, The cumulative damage includes: Based on the migration trajectory of the fatigue danger zone, the positional change of the danger zone with the rotational load cycle and wear evolution process is used as the damage calculation area; By combining the stress change characteristics of the corresponding area during the migration of the dangerous area, fatigue damage accumulation calculation is performed on the alternating loads at different locations and different service stages. The fatigue damage distribution of the cable hole wall is obtained by spatial correlation according to the actual migration process of the dangerous area.

8. The method for assessing cumulative fatigue damage of a center-through-cable drill pipe according to claim 1, characterized in that, The remaining safe tripping / pulling times for the cable-operated drill pipe in the prediction center include: Based on the fatigue damage distribution in the cable hole wall space, the area with the highest damage level at the current stage and its corresponding spatial location are determined. Combined with the wear evolution history information, it is determined whether the current danger zone is in a state of continuous expansion or migration. By combining the historical number of tripping and running cycles of the drill pipe, the cumulative service time, and the fatigue damage development trend, the damage growth pattern during future service is predicted, and the remaining safe tripping and running cycles of the center cable drill pipe are obtained.

9. The fatigue cumulative damage assessment method for center-through-cable drill pipe according to claim 1, characterized in that, Establish a multi-source state data association model consisting of wear morphology information, rotational load information, and historical operating cycle information; Based on the multi-source state data association model, wear defect evolution characteristics and fatigue damage change characteristics are extracted, and the correspondence between wear state and fatigue damage accumulation is established. The remaining safe tripping and tripping counts for the cable-stayed drill pipe in the prediction center include predictions of fatigue damage development trends based on the current detection status and the corresponding relationship.

10. The method for assessing cumulative fatigue damage of a center-through-cable drill pipe according to claim 1, characterized in that, Damage prediction models are established based on wear evolution data and fatigue damage data at different service stages to analyze wear zone expansion, changes in dangerous areas, and fatigue damage accumulation processes. The damage prediction model is updated by combining the real-time drill pipe operating status information, and the remaining safe tripping and tripping counts of the center cable drill pipe are determined based on the updated model.

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