Aging submarine pipeline maintenance scheme decision-making method and related device

Abstract

The invention belongs to the technical field of submarine pipeline safety management, and discloses an aging submarine pipeline maintenance scheme decision method and related device.The aging submarine pipeline maintenance scheme decision method comprises the steps that according to structure attribute data and corrosion pit feature data of a submarine pipeline, crack propagation evolution features of the submarine pipeline to be maintained are obtained through prediction by means of a heterogeneous surface pitting corrosion model of the submarine pipeline; based on the crack propagation evolution characteristics of the to-be-maintained submarine pipeline, the maintenance schemes of the to-be-maintained submarine pipeline are used as optimization variables, a reliability-risk-cost benefit proportion multi-target maintenance optimization model of the to-be-maintained submarine pipeline is constructed, and the remaining life of the to-be-maintained submarine pipeline under different maintenance schemes is obtained through optimization; based on the residual life of the to-be-maintained submarine pipeline under different maintenance schemes, evaluating the different maintenance schemes to obtain an optimal maintenance scheme of the to-be-maintained submarine pipeline; according to the method, the accuracy and scientificity of maintenance scheme decision making are remarkably improved, and pipeline failure accidents caused by decision errors can be effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of subsea pipeline safety management, and particularly relates to a decision-making method for the maintenance plan of aging subsea pipelines and related devices. Background Technique

[0002] As a main component of the offshore oil and gas field development and production system, the number and length of subsea pipelines are increasing continuously; however, with the passage of service time, some subsea pipelines are gradually entering the aging stage and facing many potential safety hazards; the fact that a subsea pipeline exceeds its design life does not directly mean that it cannot be used. According to the "Recommended Practice for Pipeline Life Extension in Pipeline Transportation Systems of the Petroleum and Natural Gas Industry" (GB / T 31468-2015), it is pointed out that "when there are still exploitable oil and gas resources or other operating assets need to be connected to the pipeline system, after pipeline integrity assessment and life extension applicability assessment, the service life of the pipeline can be reasonably extended"; therefore, on the premise of ensuring the safe operation of aging subsea pipelines, adopting a certain maintenance plan to extend the life of aging subsea pipelines can reduce the continuous development and utilization cost of offshore oil and gas fields.

[0003] At present, for the decision-making of the maintenance plan of aging subsea pipelines, it is usually determined by relying on the empirical inference method and the fixed maintenance mode, and there are often many decision-making mistakes, which seriously affect the safe and reliable operation of subsea pipelines; among them, although the empirical inference method can provide preliminary guidance and reference for the maintenance planning of aging subsea pipelines, it lacks systematicness and pertinence, is difficult to control the actual operation conditions of subsea pipelines, cannot effectively capture potential risk hazards, and affects the accuracy of pipeline maintenance decision-making; the fixed maintenance mode is to carry out periodic maintenance based on past experience, and cannot cope with the cumulative effect of corrosion fatigue of aging subsea pipelines, which is extremely easy to lead to too high maintenance frequency, excessive maintenance causing unnecessary resource waste and cost increase, or insufficient maintenance resulting in a decrease in the reliability of pipeline operation and an increase in the probability of accidents; in addition, the existing physical models of pipeline life are highly complex, strongly parameter-dependent, and difficult to fully consider the corrosion fatigue crack propagation behavior and uncertain factors of aging subsea pipelines. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, the present invention provides a decision-making method for the maintenance plan of aging subsea pipelines and related devices to solve the technical problem that there are often many decision-making mistakes in the decision-making of the maintenance plan of aging subsea pipelines, which seriously affect the safe and reliable operation of subsea pipelines.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a decision-making method for the maintenance plan of aging subsea pipelines, including: Obtaining the structural attribute data and pit feature data of the subsea pipeline to be maintained; Based on the structural attribute data and pitting corrosion feature data of the subsea pipeline, using the pre-constructed heterogeneous surface pitting corrosion model of the subsea pipeline, the crack propagation and evolution characteristics of the subsea pipeline to be maintained are predicted; Based on the crack propagation and evolution characteristics of the subsea pipeline to be maintained, taking the maintenance plan of the subsea pipeline to be maintained as the optimization variable, a multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the subsea pipeline to be maintained is constructed; Optimize the multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the subsea pipeline to be maintained to obtain the remaining life of the subsea pipeline to be maintained under different maintenance plans; Based on the remaining life of the subsea pipeline to be maintained under different maintenance plans, evaluate different maintenance plans to obtain the optimal maintenance plan for the subsea pipeline to be maintained.

[0006] Furthermore, the structural attribute data of the subsea pipeline to be maintained includes the pipeline material, inner diameter, length and wall thickness of the subsea pipeline to be maintained; the pitting corrosion feature data of the subsea pipeline to be maintained includes the pitting corrosion size, pitting corrosion agglomeration degree and corrosion pit spacing coefficient on the subsea pipeline to be maintained; among them, the pitting corrosion size includes the pitting corrosion depth and the pitting corrosion width.

[0007] Furthermore, the pre-constructed heterogeneous surface pitting corrosion model of the subsea pipeline includes a single pitting corrosion defect pipeline model, a double corrosion pit defect pipeline model, a triple pitting corrosion defect pipeline model and a heterogeneous group pitting corrosion defect pipeline model.

[0008] Furthermore, the multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the subsea pipeline to be maintained includes a pipeline reliability degradation objective function, a pipeline risk failure probability objective function and a pipeline cost objective function; The pipeline reliability degradation objective function is as follows:

[0009] Among them, is the reliability index at the first service time node; is the pipeline operation year; is the pipeline reliability maintenance times; is the depth of the th pipeline reliability maintenance behavior; is the reliability index at the second service time node; is the reliability index at the third service time node;

[0010] Among them, is the pipeline failure probability; is the pipeline failure maintenance times; is the depth of the th pipeline failure maintenance behavior; The pipeline cost objective function is as follows:

[0011] where is the total cost - benefit; is the total life - cycle risk assessment cost; is the direct inspection and repair cost; is the indirect inspection and repair cost.

[0012] Furthermore, using the improved dung beetle multi - objective optimization algorithm, optimize the reliability - risk - cost - benefit ratio multi - objective maintenance optimization model of the submarine pipeline to be maintained, and obtain the remaining life of the submarine pipeline to be maintained under different maintenance schemes; where the improved dung beetle multi - objective optimization algorithm is a dung beetle multi - objective optimization algorithm introduced with a dynamic parameter adjustment strategy, an adaptive search strategy, and an environmental response mechanism.

[0013] Furthermore, the process of evaluating different maintenance schemes based on the remaining life of the submarine pipeline to be maintained under different maintenance schemes to obtain the optimal maintenance scheme of the submarine pipeline to be maintained is as follows: Based on the remaining life of the submarine pipeline under different pipeline maintenance schemes, use the TOPSIS method to rank different pipeline maintenance schemes; According to the ranking results of different pipeline maintenance schemes, obtain the optimal maintenance scheme of the submarine pipeline to be maintained.

[0014] The present invention also provides an old - age submarine pipeline maintenance scheme decision - making system, including: A data acquisition module, used to acquire the structural attribute data and pit - feature data of the submarine pipeline to be maintained; An evolution prediction module, used to predict the crack - propagation evolution characteristics of the submarine pipeline to be maintained according to the structural attribute data and pit - feature data of the submarine pipeline by using a pre - constructed heterogeneous surface pitting model of the submarine pipeline; An optimization model module, used to construct a reliability - risk - cost - benefit ratio multi - objective maintenance optimization model of the submarine pipeline to be maintained with the maintenance scheme of the submarine pipeline to be maintained as the optimization variable based on the crack - propagation evolution characteristics of the submarine pipeline to be maintained; A multi - objective optimization module, used to optimize the reliability - risk - cost - benefit ratio multi - objective maintenance optimization model of the submarine pipeline to be maintained, and obtain the remaining life of the submarine pipeline to be maintained under different maintenance schemes; An evaluation and decision-making module, which is used to evaluate different maintenance plans based on the remaining life of the submarine pipeline to be maintained under different maintenance plans, and obtain the optimal maintenance plan for the submarine pipeline to be maintained.

[0015] The present invention also provides an electronic device, including: A processor, which is suitable for executing a computer program; A computer-readable storage medium, in which a computer program is stored. When the computer program is executed by the processor, the decision-making method for the maintenance plan of the aging submarine pipeline is executed.

[0016] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the decision-making method for the maintenance plan of the aging submarine pipeline is implemented.

[0017] The present invention also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the decision-making method for the maintenance plan of the aging submarine pipeline is implemented.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The decision-making method for the maintenance plan of the aging submarine pipeline provided by the present invention predicts the crack propagation and evolution characteristics of the submarine pipeline by obtaining the structural attribute data and pitting feature data of the submarine pipeline and using a pre-constructed heterogeneous surface pitting model of the submarine pipeline; based on the predicted crack propagation and evolution characteristics of the submarine pipeline, by comprehensively considering multiple factors such as the reliability, failure risk and cost-benefit of the submarine pipeline, and through multi-objective optimization, the remaining life of the submarine pipeline under different maintenance plans is obtained; taking the remaining life of the submarine pipeline under different maintenance plans as a quantitative index helps decision-makers compare and select the optimal maintenance plan; the present invention determines the optimal maintenance plan by predicting crack propagation and evolution characteristics, comprehensively considering multiple factors and multi-objective optimization, significantly improving the accuracy and scientificity of the maintenance plan decision-making, effectively reducing pipeline failure accidents caused by decision-making mistakes, and ensuring the long-term safe operation of the submarine pipeline; at the same time, it can ensure that the decision-making maintenance plan reaches the best balance among reliability, risk and cost-benefit.

[0019] The decision-making system, electronic device, computer-readable storage medium and computer program product for the maintenance plan of the aging submarine pipeline provided by the present invention have all the advantages of the above decision-making method for the maintenance plan of the aging submarine pipeline. Description of the Drawings

[0020] Figure 1 It is a flowchart of the decision-making method for the maintenance plan of the aging submarine pipeline provided in Embodiment 1; Figure 2Schematic diagram of the physical model of the pipeline with corrosion pits in Embodiment 1; wherein, Figure 2 (a) is the physical model of the pipeline with a single corrosion pit, Figure 2 (b) is the physical model of the double-corrosion pipeline, Figure 2 (c) is the physical model of the pipeline with three corrosion pits, Figure 2 (d) is the physical model of the pipeline with heterogeneous group corrosion pits; Figure 3 Schematic diagram of the principle of the block network division strategy in Embodiment 1; Figure 4 Reliability degradation curve of the pipeline in multiple stages under maintenance in Embodiment 1; Figure 5 Curve of the change in the failure probability of the pipeline under maintenance in Embodiment 1; Figure 6 Schematic diagram of the principle of the improved dung beetle multi-objective optimization algorithm in Embodiment 1; Figure 7 Prediction results of the reliability and cost Pareto solution sets under different maintenance times in Embodiment 1; Figure 8 Prediction results of the risk and cost Pareto solution sets under different maintenance times in Embodiment 1; Figure 9 Prediction results of the updated remaining life of the aged subsea pipeline under different maintenance times and scenarios in Embodiment 1; Figure 10 Structure block diagram of the decision-making system for the maintenance plan of the aged subsea pipeline provided in Embodiment 2; Figure 11 Structure block diagram of the electronic device provided in Embodiment 3. Specific implementation manner

[0021] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the following specific embodiments are used to further elaborate on the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The present invention provides a decision-making method for the maintenance plan of an aged subsea pipeline, including the following steps: Step 100: Obtain the structural attribute data and corrosion pit feature data of the subsea pipeline to be maintained.

[0023] Step 200: According to the structural attribute data and corrosion pit feature data of the subsea pipeline, use the pre-constructed heterogeneous surface pitting model of the subsea pipeline to predict the crack propagation evolution characteristics of the subsea pipeline to be maintained.

[0024] Step 300: Based on the crack propagation and evolution characteristics of the submarine pipeline to be maintained, with the maintenance plan of the submarine pipeline to be maintained as the optimization variable, a multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained is constructed.

[0025] Step 400: Optimize the multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained to obtain the remaining life of the submarine pipeline to be maintained under different maintenance plans.

[0026] Step 500: Based on the remaining life of the submarine pipeline to be maintained under different maintenance plans, evaluate different maintenance plans to obtain the optimal maintenance plan for the submarine pipeline to be maintained.

[0027] The decision-making method for the maintenance plan of the aged submarine pipeline according to the present invention realizes the scientific and precise maintenance decision-making through steps such as obtaining basic data, predicting crack propagation, constructing an optimization model, optimizing to obtain the remaining life, and evaluating and selecting the optimal plan; specifically, using the pre-constructed heterogeneous surface pitting model of the submarine pipeline to predict the crack propagation and evolution characteristics of the submarine pipeline to be maintained; among them, the crack propagation and evolution are directly related to the safety and remaining life of the pipeline; on the basis of obtaining the crack propagation and evolution characteristics, a multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained is constructed to comprehensively consider multiple factors such as the reliability, risk, and maintenance cost of the pipeline, enabling maintenance personnel to find the maintenance plan with the highest cost-benefit under the premise of ensuring the safety of the pipeline, ensuring that the maintenance decision-making is more comprehensive and scientific; secondly, optimize the constructed multi-objective maintenance optimization model to obtain the remaining life of the submarine pipeline to be maintained under different maintenance plans, and based on the remaining life of the submarine pipeline to be maintained under different maintenance plans, evaluate different maintenance plans to obtain the optimal maintenance plan for the submarine pipeline to be maintained. Through evaluation and comparison, clarify the advantages and disadvantages of various maintenance plans, so as to select the optimal maintenance plan to maximize the maintenance benefit; the present invention not only improves the accuracy and reliability of maintenance decision-making, but also reduces the maintenance cost and risk, providing a strong guarantee for the safe and reliable operation of submarine pipelines.

[0028] The following uses some specific embodiments to further explain the decision-making method for the maintenance plan of the aged submarine pipeline provided by the present invention: Embodiment 1 As shown in the appendix Figure 1 This Embodiment 1 provides a decision-making method for the maintenance plan of an aged submarine pipeline, including the following steps: Step 1: Obtain the structural property data and pitting feature data of the submarine pipeline to be maintained. The structural property data of the submarine pipeline to be maintained include the pipeline material, inner diameter, length, and wall thickness of the submarine pipeline to be maintained; the pitting feature data of the submarine pipeline to be maintained include the pitting size, pitting agglomeration degree, and corrosion pit spacing coefficient on the submarine pipeline to be maintained; among them, the pitting size includes the pitting depth and pitting width.

[0029] Step 2: According to the structural property data and pitting feature data of the submarine pipeline, use the pre-constructed heterogeneous surface pitting model of the submarine pipeline to predict the crack propagation and evolution characteristics of the submarine pipeline to be maintained. Among them, the pre-constructed heterogeneous surface pitting model of the submarine pipeline, that is, the heterogeneous surface pitting - crack initiation - propagation model of the aged submarine pipeline under alternating cyclic load.

[0030] The construction process of the pre-constructed heterogeneous surface pitting model of the submarine pipeline is as follows: Based on the structural property data and pitting feature data of the submarine pipeline, construct a physical model of the pipeline with pits, as shown in the appendix Figure 2 It should be noted that during the pitting evolution process on the submarine pipeline, the pitting pits always maintain the shape of a semi-ellipsoid; therefore, the following four physical models of the pipeline with pits established in this Embodiment 1, including the physical model of the pipeline with a single pit, the physical model of the pipeline with double corrosion, the physical model of the pipeline with three pits, and the physical model of the pipeline with heterogeneous group pits, are as shown in the appendix Figure 2 shown.

[0031] Among them, the physical model of the pipeline with a single pit is to preset an ellipsoidal pit at the axial center position of the submarine pipeline, as shown in the appendix Figure 2 (a); the physical model of the pipeline with double corrosion is to preset another ellipsoidal pit with different included central angles, distances, and agglomeration degrees at the axial and circumferential positions of the established ellipsoidal pit at the axial center of the submarine pipeline, as shown in the appendix Figure 2 (b); the physical model of the pipeline with three pits is to preset another two ellipsoidal pits with different included central angles and distances at the circumferential position of the established ellipsoidal pit at the axial center of the pipeline, as shown in the appendix Figure 2 (c); the physical model of the pipeline with heterogeneous group pits is to preset multiple ellipsoidal pits with different depths and widths around the established ellipsoidal pit at the axial center of the pipeline, as shown in the appendix Figure 2 (d).

[0032] Next, based on the physical model of the pipeline with corrosion pits, a finite element model of the pipeline with corrosion pits is constructed to obtain a pitting corrosion model of the heterogeneous surface of the subsea pipeline. Among them, the pitting corrosion model of the heterogeneous surface of the subsea pipeline includes a single corrosion pit defect pipeline model, a double corrosion pit defect pipeline model, a triple corrosion pit defect pipeline model, and a heterogeneous group corrosion pit defect pipeline model. When constructing the finite element model of the pipeline with corrosion pits, a block network division strategy is adopted, that is, the model is divided into an ordinary pipe body, a pipe body with corrosion pits, and the corrosion pit body, and meshing is carried out according to different mesh division sizes, as shown in the appendix Figure 3 shown; among them, in order to obtain the transformation and propagation law of different corrosion pits to fatigue cracks, Cohesive units are added to the pipe body with corrosion pits and the corrosion pit body.

[0033] The process of predicting the crack propagation and evolution characteristics of the subsea pipeline to be maintained by using the pre-constructed pitting corrosion model of the heterogeneous surface of the subsea pipeline includes: importing the pre-constructed pitting corrosion model of the heterogeneous surface of the subsea pipeline into a preset simulation analysis software, and through simulation analysis, to predict different corrosion pit-crack propagation and evolution laws, and then the crack propagation and evolution characteristics of the subsea pipeline to be maintained can be obtained. Specifically, by simulating the pre-constructed pitting corrosion model of the heterogeneous surface of the subsea pipeline, the crack initiation time, crack initiation location, and crack propagation path under different corrosion pit characteristics can be obtained, and then the crack propagation and evolution characteristics of the subsea pipeline to be maintained can be obtained. Among them, different corrosion pit characteristics such as the width and depth of a single corrosion pit, the axial distance, circumferential angle of double corrosion pits, and different relative depths of triple corrosion pits.

[0034] It should be noted that when simulating the pre-constructed pitting corrosion model of the heterogeneous surface of the subsea pipeline, with the cyclic application of external loads, the internal fatigue damage of the pipeline material gradually accumulates, and cracks grow from micro-initiation until macro-propagation. By quantifying the damage variable, the degree of gradual damage of the internal microstructure of the material due to crack propagation can be effectively reflected.

[0035] Specifically, taking a subsea pipeline with a pipeline material of X65 steel grade, a pipeline length of 2000 mm, an inner diameter of 400 mm, and a wall thickness of 11.1 mm as an example, the crack initiation time, crack initiation location, and crack propagation path under different corrosion pit characteristics, that is, the crack propagation and evolution characteristics of the subsea pipeline to be maintained, are described as follows: (1) The corrosion pit depth is one of the key variables affecting the pipeline performance; relatively shallow corrosion pits usually represent the initial or mild corrosion degree, which has little impact on the pipeline structure; while relatively deep corrosion pits reflect more serious corrosion, which may lead to local damage of the pipeline and aggravation of the stress concentration effect. By analyzing the change of pit depth, the influence law of the stress distribution on the pipe wall and the crack initiation location can be analyzed.

[0036] (2) The pitting width is one of the key variables affecting the pipeline performance. The larger the pitting width, the shorter the crack initiation time. Although the change in pitting width also affects the crack initiation time, the influence degree is relatively small. The increase in pitting depth has a more significant effect on the local stress concentration effect, and the stress concentration generated at the tip of the microcrack is higher, thus accelerating the crack initiation process. When the pitting depth is 1 mm and the pitting radius is also 1 mm, after the single-pitting defect pipeline model experiences nearly 1.6 million cyclic loads, its corrosion fatigue damage D reaches 1, thereby triggering the initiation of corrosion fatigue cracks. Under the same loading conditions, when the pitting width remains unchanged and the depth is 2 mm, it is only about 0.7 million times, and the crack initiation life is shortened by 56.2% compared with that when the pitting depth is 1 mm. When the pitting width is 2 mm and the depth is 1 mm, its crack initiation life is equivalent to that when the pitting width is 1 mm and the depth is 1.5 mm, and microcracks are generated after about 1.1 million cyclic loads.

[0037] (3) By selecting three points on the side of the pit, the bottom of the pit and between the two pits as the monitoring points for the damage degree, it is found through monitoring that after the single-pitting defect pipeline model experiences about 1.76 million cyclic loads, the corrosion fatigue damage reaches 1, thereby triggering the initiation of corrosion fatigue cracks. Among them, at the initial cyclic number, the corrosion fatigue damage is 0. When the corrosion fatigue damage reaches 1, cracks initiate in the pipeline. Under the same loading conditions, the crack initiation life of the axial double-pitting pipeline is significantly extended, reaching about 2.42 million times, an increase of 50.7% compared with the crack initiation life of the single-pitting defect pipeline model. The axial double-pitting can effectively slow down the accumulation rate of pipeline damage and significantly improve the corrosion fatigue life of the pipeline. However, when the pitting is circumferentially distributed, the cumulative rate of corrosion fatigue damage increases compared with the single-pitting defect pipeline model, and cracks begin to initiate after about 1.29 million cycles, shortening the crack initiation life of the single-corrosion defect pipeline by 19.3%.

[0038] Taking pit A with an axial diameter of 2 mm and a depth of 1.5 mm and pit B with an axial diameter of 2 mm and a depth of 2 mm as examples; when the corrosion pit spacing coefficient is 10, the damage variation curves of pit A and pit B with the number of cycles tend to be the same; when the number of cycles is small, the damage growth of pit B is relatively slow, but when the number of cycles reaches 500,000, the damage of the deeper pit increases sharply, and the slope of the damage curve increases; when the corrosion pit spacing coefficient is 5, the contribution of the pit depth to the increase in the damage amount is more obvious; especially at pit B, the damage increases fastest, and cracks initiate when the number of cycles reaches 400,000, and under the condition of a smaller spacing, the pit depth has the greatest influence on the damage amount; when the corrosion pit spacing coefficient is 7, the influence of the pit depth on the damage amount is smaller than that when the corrosion pit spacing coefficient is 5, that is, the change rate of the pit damage amount increases and tends to be stable. Although the pit depth still affects the damage amount, its influence begins to weaken, and the damage amount increase rate is relatively gentle; when the corrosion pit spacing coefficient is 10, the interaction between the two pits has little influence on the initiation life of the pipeline corrosion fatigue crack.

[0039] (5) In the initial stage of damage of the single-pit defect pipeline model, the damage is mainly concentrated in the area centered on the pit and gradually spreads to the periphery. The whole diffusion process shows an obvious radial distribution characteristic, that is, a damage zone that fits the shape of the pit is formed with the pit as the center; as the distance from the pit center expands outward, the damage degree gradually weakens, showing an obvious damage gradient with a high center and a low edge; the boundary of the damage area is relatively clear, and the high-damage area and the low-damage area can be clearly distinguished, and the damage zone has strong local concentration characteristics; in the circumferential section of the pit-shaped damage zone, the damage first concentrates on the outer wall of the pipeline, that is, the outer wall position around the upper part of the corrosion pit. As the corrosion phenomenon gradually deepens, the damage degree at the bottom of the pit gradually decreases, forming a damage fault; the upper area of the corrosion pit shows relatively serious damage, especially near the pit mouth, where the damage degree reaches the highest; among them, the damage distribution in this area has an obvious local concentration phenomenon, and the edge of the damage zone shows an irregular expansion shape and gradually expands to the periphery; although the damage in the bottom area of the pit has an outward expansion trend, its expansion speed and range are significantly smaller than those in the upper area of the corrosion pit; as the corrosion pit gradually deepens, the damage degree at the bottom of the pit gradually decreases, and a damage fault appears. The damage expansion trend of the deeper pit bottom decreases. Although the damage at the bottom of the corrosion pit still has an outward expansion trend, its expansion speed and range are much smaller than those of the shallower corrosion pit; as the damage accumulates, the maximum damage position gradually moves towards the pit shoulder area, the damage zone range also continuously expands, and the pit shoulder damage shows a trend of gradually expanding from the surface to the radial direction of the pipeline, gradually expanding from a sheet-like range to local concentration, and finally reaching the critical point of crack initiation, and finally forming microcracks.

[0040] (6) The agglomeration of pits has a great influence on the damage position and crack initiation position. For example, when the agglomeration of double pits is 20%, the junction of the double pits is close to the bottom of the pit, forming an obvious triangular notch. The maximum damage is mainly concentrated in the pit shoulder and bottom area. The damage morphology is close to the triangular notch. The maximum damage depth exceeds the bottom of the pit. The damage range extends along the circumference of the pipeline and the inner wall of the pit, and exceeds the center of the pit. There are multiple crack initiation positions, mainly distributed near the bottom of the pit, the pit shoulder area and the inner wall of the pit. The crack propagation angle is close to vertical and penetrates into the inner wall of the pipeline. The expansion path has obvious directionality. When the agglomeration of double pits decreases to 15%, the junction of the double pits moves above the pit shoulder. The damage is still mainly concentrated in the shoulder and bottom of the pit. The damage morphology presents an arrow-shaped outline close to the triangular notch. The maximum damage depth still exceeds the bottom of the pit. The damage range extends along the circumference of the pipeline and the inner wall of the pit, but does not exceed the center of the pit. Different from the case where the aggregation degree is 20%, the crack initiation position is relatively single at this time, mainly concentrated in the shoulder area at the bottom of the corrosion pit, and the crack propagation angle slows down; when the double pit aggregation degree is reduced to 10%, the junction of the double pits is located in the lower area of ​​the pit shoulder, and the damage is mainly concentrated in the pit shoulder and the bottom. The damage morphology still fits the triangular notch in an arrow shape, which is similar to the case where the aggregation degree is 15%. The maximum damage depth exceeds the bottom of the corrosion pit, and the damage range expands along the circumference of the pipeline and the inner wall of the corrosion pit, but does not exceed the center of the corrosion pit; the crack initiation position is single, mainly concentrated in the shoulder area near the bottom of the corrosion pit. When the double pit agglomeration degree is further reduced to 5%, the junction of the double pits is located at the shoulder of the pit, and the damage morphology is arrow-shaped, but the maximum damage depth does not exceed the bottom of the corrosion pit. The maximum damage position is mainly concentrated in the pit shoulder and the double pit junction area. The damage range expands along the pipeline annular direction and the inner wall of the corrosion pit, but does not reach the center of the corrosion pit; similar to the case when the agglomeration degree is 20%, there are multiple crack initiation locations, including the bottom of the pit, the pit shoulder area and the double pit junction.

[0041] (7) A non-homogeneous group pit pipeline refers to a group of corrosion pits with obvious differences in shape, depth and width on the pipeline surface. Under different pit depth distribution conditions, it has a variety of crack propagation paths and microcrack sources. When the depth of the small pits at both ends is less than that of the large pit in the middle, the crack initiation positions are mainly concentrated at the bottom of the pit and above the pit shoulder. The cracks tend to initiate at the bottom and shoulder of the small pit and propagate along the pit shoulder. When the depth of the pits at both ends is equal to that of the large pit in the middle, the damage rate is significantly accelerated, the crack initiation positions are concentrated at the shoulder of the small pit, and the pit mouth damage area increases, and the number of microcrack sources increases. When the depth of the pits at both ends is greater than that of the large pit in the middle, the damage concentration and crack initiation positions first appear at the mouth of the small pit and spread along the angle between the small pit and the large pit to the bottom of the small pit. At this time, the stress concentration effect of the deeper pits at both ends dominates, and the crack propagation path has obvious directionality.

[0042] (8) According to the distribution of pits, the physical model of the heterogeneous pit cluster pipeline is divided into a dispersed pit cluster model and a clustered pit cluster model; among them, the clustered pit cluster refers to a larger irregular corrosion area formed by the overlap of adjacent pits, and the damage area on the pipeline surface shows obvious concentration; the damage area at the bottom of the agglomerated heterogeneous pit cluster is relatively uniform, similar to the axial projection area of ​​the pit cluster, and presents a rectangular equivalent shape; the dispersed pit cluster refers to adjacent pits without overlap, but the spacing between pits is small, forming multiple independent but interacting group corrosion defect areas; the bottom damage area of ​​the dispersed heterogeneous pit cluster is large, and there is a large area of ​​damage in both radial and circumferential directions, which easily leads to cracks in multiple locations of the pipeline at the same time. In the clustered pit cluster, the overlap between pits leads to the superposition of stress concentration effects, especially in the shoulder and bottom area of ​​the central pit, where the stress level is large, which is the main area for crack initiation and expansion. The stress concentration areas of the dispersed pit cluster are scattered in multiple areas, which are more likely to have multi-source microcracks. In the dispersed group pits, as the distance between two corrosion defects decreases, the high stress area is concentrated in the shoulder of the deeper pit, and then damage and microcracks appear. The agglomerated group pits cause the stress field to be superimposed within the center of the group pits, forming a large high stress area with uneven stress gradient changes, which becomes the main area for crack initiation and expansion; under the same loading conditions, the crack initiation life of the agglomerated group pit pipeline is about 1.32 million times, which is 17.5% shorter than the crack initiation life of the single pit pipeline; the crack initiation life of the dispersed group pit pipeline is about 1.47 million times, which is 8.13% shorter than the crack initiation life of the single pit pipeline; the crack initiation life of the agglomerated group pit pipeline is 10.2% shorter than the crack initiation life of the dispersed group pit pipeline.

[0043] Step 3: Based on the crack propagation evolution characteristics of the submarine pipeline to be maintained, the maintenance plan of the submarine pipeline to be maintained is used as the optimization variable to construct a reliability-risk-cost-benefit ratio multi-objective maintenance optimization model for the submarine pipeline to be maintained. Among them, the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model for the submarine pipeline to be maintained includes the pipeline reliability degradation objective function, the pipeline risk failure probability objective function and the pipeline cost objective function.

[0044] Specifically, the process of constructing the pipeline reliability degradation objective function is as follows: Based on the crack propagation and evolution characteristics of the submarine pipeline to be maintained, a dynamic Bayesian model is constructed to generate the pipeline reliability at different service times, and the pipeline reliability at different service times is fitted to obtain the pipeline reliability degradation objective function. It should be noted that according to the degradation trend, the service time of the pipeline is divided into the first service time node, the second service time node, and the third service time node. Specifically, the first service time node is when the pipeline has been operating for 15 - 20 years. At this time, the pipeline is approaching its design life and has a certain degree of corrosion or wear. The second service time node is when the pipeline has been operating for 20 - 25 years. The pipeline passes the life extension assessment and enters the early stage of extended service. The third service time node is when the pipeline has been operating for 25 - 30 years, and the pipeline enters the later stage of life extension. Specifically, the pipeline reliability degradation objective function is as follows:

[0045] Among them, is the reliability index at the first service time node; is the operating year of the pipeline; is the number of pipeline reliability maintenance times; is the depth of the th pipeline reliability maintenance behavior; is the reliability index at the second service time node;

[0046] is the reliability index at the third service time node.

[0046] Example illustration: Assume starting from the 15th year, the reliability of the pipeline at this time is represented by the reliability index at the first service time node. After determining that the maintenance time variables are the 16th year, the 18th year, and the 20th year, the change in the pipeline reliability curve is as shown in Figure 4 . Among them, when the pipeline has been operating for 15 years, the reliability is calculated using Y r1 , and at this time n the value of 2 is 0; when the pipeline has been operating for 16 years, the reliability is calculated using Y r1 , and at this time n the value of 2 is 1; when the pipeline has been operating for 17 years, the reliability is calculated using Y r1 , and at this time n the value of 2 is 1; when the pipeline has been operating for 18 years, the reliability is calculated using Y r1 , and at this time n the value of 2 is 2; when the pipeline has been operating for 19 years, the reliability is calculated using Y r1 , and at this time n the value of 2 is 2; when the pipeline has been operating for 20 years, the reliability is calculated using Yr2 Calculation is performed at this time n The value of 2 is 3; when the pipeline operates for the 21st year, the reliability is calculated using Y r2 Calculation is performed at this time n The value of 2 is 3; and so on until the pipeline reliability is lower than the set threshold, and record the value at this time x as x XE1 This is the final remaining life of the pipeline after considering reliability and implementing three maintenance operations

[0047] Specifically, the construction process of the pipeline risk failure probability objective function is as follows: Construct a dynamic Bayesian model to generate the pipeline failure probability corresponding to different service times, and fit the pipeline failure probabilities at different service times to obtain the pipeline risk failure probability objective function; among them, the pipeline risk failure probability objective function is as follows:

[0048] Among them, is the pipeline failure probability; is the number of pipeline failure maintenance times; is the depth of the th pipeline failure maintenance behavior

[0049] Example illustration: Assume that starting from the 15th year, use Y pj to represent the pipeline failure probability at this time. After determining the maintenance time variable x ti(n1) as the 15th year and the 17th year, the pipeline failure probability curve changes as shown in Figure 5 ; among them, when the pipeline operates for the 15th year, at this time n the value of 1 is 1; when the pipeline operates for the 16th year, at this time n the value of 1 is 1; when the pipeline operates for the 17th year, at this time n the value of 1 is 2; when the pipeline operates for the 18th year, at this time n the value of 1 is 2; and so on until the pipeline failure probability exceeds the set threshold, and record the value at this time x as x XE2 This is the final remaining life of the pipeline after considering failure probability and implementing two maintenance operations

[0050] It should be noted that in addition to common risk factors such as corrosion and fatigue, the environmental conditions in the laying area of aging subsea pipelines have changed compared with the design period, including the laying topography, fluid properties, climate conditions, and fishing activities, resulting in an increased exposure of aging subsea pipelines. Therefore, the service conditions of aging subsea pipelines are gradually deviating from the original design expectations, leading to changes in the risk failure characteristics of the pipelines. In this Example 1, by constructing a dynamic Bayesian model, the failure probabilities of aging pipelines at different service times are generated to accurately describe the risk failure state of the pipelines.

[0051] Specifically, the pipeline cost objective function is as follows:

[0052] where is the total cost-benefit; is the total life cycle risk assessment cost; is the direct inspection and repair cost; is the indirect inspection and repair cost.

[0053] It should be noted that by analyzing the sum of the total life cycle risk assessment cost, direct inspection and repair cost, and indirect inspection and repair cost of the life extension plan, the financial benefits of the life extension period are measured. If the cost-benefit objective function is small, it means that the cost of the life extension plan is within an acceptable range, and the pipeline has the feasibility of life extension. On the contrary, if the objective function is large, it means that the pipeline considers implementing an abandonment decision. The total life cycle risk assessment cost is the maintenance cost caused by all potential risk values related to the life extension plan, including equipment failures, environmental impacts, and operation interruptions. The direct inspection and repair cost refers to the actual inspection and maintenance costs incurred during the life extension process, including labor costs, material costs, and equipment usage fees. The indirect inspection and repair cost is the associated incidental cost, such as downtime losses, production delays, and other indirect losses.

[0054] Step 4: Optimize the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the subsea pipeline to be maintained to obtain the remaining life of the subsea pipeline to be maintained under different maintenance plans. Specifically, using the improved dung beetle multi-objective optimization algorithm, with the pipeline reliability threshold and failure threshold as constraint conditions, optimize the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the subsea pipeline to be maintained to obtain the remaining life of the subsea pipeline to be maintained under different maintenance plans. Among them, the improved dung beetle multi-objective optimization algorithm is a dung beetle multi-objective optimization algorithm introduced with a dynamic parameter adjustment strategy, an adaptive search strategy, and an environmental response mechanism, as shown in Figure 6 shown.

[0055] In this Embodiment 1, the process of the improved dung beetle multi-objective optimization algorithm is as follows: (a) Ball-rolling behavior: When pushing the dung ball, the dung beetle relies on celestial cues for navigation to ensure that the dung ball rolls in a straight line; in the ball-rolling mode of the traditional dung beetle multi-objective optimization algorithm, its position update depends on constant terms such as the betrayal and deception factor, which may lead to insufficient early convergence speed or getting trapped in local optima in the later stage; in this Embodiment 1, by adding a dynamic inertia weight and a diversity-driven step size control strategy, that is, introducing a non-linearly decreasing inertia weight in the position update function, making this weight larger in the initial stage of iteration to enhance the global exploration ability; gradually decreasing as the iteration progresses to accelerate local exploitation; among them, the position update function is as follows:

[0056]

[0057]

[0058] Among them, is the position information at the iteration number of ; is the iteration number; is the non-linearly decreasing inertia weight; is the position information at the iteration number of ; is the natural ability distribution, taking values of -1 or 1; is the betrayal and deception factor, ; is a constant, and the value range is (0, 1); is the step size; is the basic step size reference value; is the step size adjustment coefficient; is the calculation result of the variance of the Euclidean distance between individuals; is the maximum number of iterations.

[0059] (b) Dancing behavior: When encountering an obstacle that cannot move forward, the dung beetle will change its direction through a special dancing behavior to find a new moving path; in the traditional dung beetle multi-objective optimization algorithm, the tangent function is used to obtain a new rolling direction, only considering the values within the interval. Once a new direction is determined, the dung beetle will continue to roll the dung ball along this direction; however, when the angle is 0, / 2, and When the position of the dung beetle does not update, this kind of direction switching depends on a fixed threshold and it is difficult to adapt to complex terrains. In Embodiment 1 of the present invention, the switching threshold of the direction angle is dynamically set according to the standard deviation of the current population fitness, that is, a Lévy flight random term is superimposed when the direction angle is updated. If the fitness difference is small, the threshold is reduced to trigger the dancing perturbation more frequently. Among them, the update process of the direction angle is as follows:

[0060]

[0061] Among them, is the updated direction angle; is the initial direction angle; is the direction perturbation intensity coefficient; is the added Lévy flight random term; is the shape parameter of the Lévy flight distribution.

[0062] (c) Reproductive behavior: The dung beetle keeps rolling the dung ball until it safely delivers it to the hidden area. For female dung beetles, choosing a suitable spawning site for their offspring is crucial, which is directly related to the survival and reproduction of the offspring. To simulate the female dung beetle choosing a suitable spawning area, a boundary selection strategy is introduced. This strategy uses a dynamic selection factor to dynamically adjust the upper and lower limits of the spawning area. Combining the dynamic selection factor and the maximum number of iterations, the range of the spawning area is determined. However, the linear contraction in the traditional multi-objective optimization algorithm of dung beetles may prematurely limit the search range. Therefore, in Embodiment 1 of the present invention, by designing a dynamic contraction factor R such that its contraction rate fluctuates sinusoidally with the iteration. It contracts rapidly in the initial stage to focus on the potential optimal area, slows down in the middle stage to avoid missing the global solution, and accelerates again in the later stage to improve the convergence accuracy. Among them, the boundary selection strategy introducing the dynamic contraction factor R is as follows:

[0063]

[0064]

[0065] Among them, is the upper limit of the optimized spawning area; is the current best spawning position; is the dynamic contraction factor; is the upper limit of the spawning area before optimization; is the lower limit of the optimized spawning area; is the lower limit of the spawning area before optimization.

[0066] In addition, the optimal spawning area is dynamically adjusted as the number of iterations increases, and the positions of the oospheres will change accordingly. The position change function of the oospheres is as follows:

[0067] where, is the position of the th oosphere at the th iteration; and are both random variables; is the position of the th oosphere at the th iteration.

[0068] (d) Foraging behavior: After the larvae hatch from the eggs, they need to determine the optimal foraging area to guide the dung beetles to forage. The boundaries of the optimal foraging area are as follows:

[0069]

[0070] where, is the upper limit of the foraging area; is the global best position; is the lower limit of the foraging area.

[0071] During the foraging process, in the traditional dung beetle multi-objective optimization algorithm, the larvae only move towards the global optimal position , which easily leads to the loss of diversity. In this Example 1, a random individual guiding term is added to the position update formula. By fusing the global optimum and random perturbations, the foraging paths of the larvae are more diverse, and especially in multi-modal optimization problems, it can effectively locate the scattered extreme points. The position update formula during the foraging process is as follows:

[0072]

[0073] where, and are both random numbers that follow a normal distribution and are (0, 1); is the weight of the random individual guiding term; is the random individual guiding term.

[0074] (e) Theft behavior: In the dung beetle population, stealing behavior is regarded as a common competitive strategy; by stealing, dung beetles can obtain the dung balls of other individuals, thus providing themselves with more food and nutrient sources, and further increasing their survival advantages and reproduction opportunities in the population; the stealing behavior of traditional multi-objective optimization algorithms for dung beetles relies on fixed probabilities and Gaussian perturbations, and it is difficult to dynamically respond to environmental changes; in this Embodiment 1, the Gaussian perturbation is replaced with a Cauchy distribution to generate a random vector ， Its heavy-tailed property allows for a larger range of perturbations, enhancing the exploration ability of unknown regions; among them, the stealing behavior based on generating a random vector with a Cauchy distribution is as follows:

[0075] Among them, is a constant; is the random vector generated by replacing the Gaussian perturbation with a Cauchy distribution.

[0076] It should be noted that each maintenance plan includes a repair plan, repair nodes, repair frequency, and repair degree; preferably, the repair nodes and repair degree in each maintenance plan are used as the maintenance optimization variables in this state, and with the pipeline reliability threshold and failure threshold as constraints, the improved multi-objective optimization algorithm for dung beetles is used to optimize the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the submarine pipeline to be maintained, and the remaining life of the submarine pipeline to be maintained under different maintenance plans can be obtained.

[0077] Step 5: Based on the remaining life of the submarine pipeline to be maintained under different maintenance plans, evaluate different maintenance plans to obtain the optimal maintenance plan for the submarine pipeline to be maintained. Specifically, based on the remaining life of the submarine pipeline under different pipeline maintenance plans, the TOPSIS method is used to sort different pipeline maintenance plans; among them, by extracting the Pareto optimal solution, the best maintenance plan is determined to update the remaining life of the aging submarine pipeline under different maintenance frequencies and plans.

[0078] It should be noted that according to the characteristics of the reliability restoration maintenance types of aging submarine pipelines, four specific maintenance operation plans are divided, including Plan Ar 、Plan Br 、Plan Cr and Plan Dr .

[0079] (1)Plan Ar: Based on the Beaver maintenance equipment, a fiberglass layer of epoxy resin is used. It is expanded by steam pressure to closely adhere to the pipe wall to repair pipe joints and circumferential cracks in the pipe. The specific operation steps are as follows: First, confirm the location of the pipe damage, remove the surrounding dirt and impurities to ensure a clean working environment. Then, fix the support system of the Beaver maintenance equipment and install it firmly around the pipe to be repaired. Wrap the pre-treated epoxy resin fiberglass layer around the damaged area. The fiberglass layer is pre-soaked in epoxy resin to have good adhesiveness and plasticity. Then, start the steam generator, introduce high-pressure steam into the expansion device through the pipe, and the steam pushes the airbag to expand, making the epoxy resin fiberglass layer closely adhere to the inner wall of the pipe. During this process, the pressure value needs to be monitored in real time to ensure uniform expansion. After maintaining the steam pressure for a certain period of time, the epoxy resin is fully cured. The cured epoxy resin fiberglass layer forms a strong protective layer, effectively repairing the pipe joints and circumferential cracks. Finally, after the epoxy resin is completely cured, release the steam pressure, remove the maintenance equipment, and use non-destructive testing techniques such as ultrasonic testing to check the repaired area to ensure there are no residual cracks or defects and the repair effect is good. After confirming the repair is completed, clean the site and restore the normal operation of the pipe; among them, the plan Ar Under this plan, the pipe reliability recovery degree is 0.010 - 0.025.

[0080] (2)Plan Br : After accurately positioning and firmly sealing the simple caisson, install welding equipment to remove dirt and perform pipe welding repair. After ensuring the weld quality, safely remove the caisson and equipment. The specific operation steps are as follows: First, accurately position and lower the pre-designed simple caisson to the position of the pipe to be maintained through a hoisting device, ensure the caisson is firmly placed on the seabed, and use sealing materials to seal the bottom of the caisson to prevent seawater from seeping in. Install various welding equipment inside the caisson, including welding machines, cables, welding torches, etc., to ensure these equipment can operate normally in the underwater environment. Then, the operator starts the cleaning program through the control panel of the caisson and uses professional underwater cleaning equipment to remove oxides and dirt on the pipe surface. Subsequently, underwater welding technicians enter the inside of the caisson and use welding equipment to weld and repair the pipe cracks, ensuring that each weld is uniform, firm, and free of pores or fissures. During the welding process, the quality of the weld needs to be continuously monitored and adjusted in real time to ensure the welding effect meets the expectations. After the weld quality meets the requirements, perform cleaning work on the welding area to remove welding residues and excess materials, ensuring the pipe surface is smooth and flat. Finally, remove the simple caisson, safely remove all welding equipment and materials from the underwater operation area, and recycle the sealing materials of the caisson; among them, the plan Br Under this plan, the pipe reliability recovery degree is 0.025 - 0.045.

[0081] (3)PlanCr : Adopt the opening maintenance plan of the underwater non-stop production mechanical three-way repair method. The specific operation steps are as follows: First, install an underwater mechanical three-way and an opening machine at both ends of the pipeline for precise opening operation to ensure that the position and size of the opening meet the maintenance requirements; Subsequently, the operator installs an underwater plugging machine and a bypass three-way, and connects the bypass pipeline to the system. The connection of the bypass three-way ensures that during the plugging maintenance, natural gas can still flow through the bypass pipeline to maintain the stable transportation function of the pipeline system; Then open the sandwich valve, guide the flow of natural gas through the bypass pipeline, plug the pipe section to be repaired, and adjust the opening and closing degree of the sandwich valve to ensure the effectiveness of the plugging operation, prevent leakage and maintain the normal operation state of other parts of the pipeline; Subsequently, the operator conducts pressure relief treatment to ensure that the pressure in the system returns to normal, and uses professional tools and techniques to conduct a detailed inspection of the plugging effect; After passing the sealing inspection, the operator uses a cold cutting saw to cut off the pipe section to be replaced; After cutting, the operator connects a spherical flange at the cutting end to adjust the pressure balance of the pipeline; Finally, open the plugging head, close the sandwich valve at the same time, conduct the final pressure relief treatment, and remove the bypass pipeline and the plugging machine; Restore the seabed surface and cover it with sandbags in the dredging area of the submarine pipeline to ensure the complete completion of the pipeline maintenance work and environmental protection; Among them, the plan Cr Under this plan, the pipeline reliability recovery degree is 0.045 - 0.065.

[0082] (4)Plan Dr : Connect the remotely operated vehicle (ROV) to the ocean control platform through a cable, and control it to be lowered to the underwater position near the target pipeline through commands and monitoring; The multifunctional robotic arm equipped with the ROV is equipped with a laser cutter and has high-precision mechanical operation capabilities. It performs precise and safe cutting on the abandoned pipe section to ensure the integrity of the surrounding pipeline structure; After cutting, the robotic arm is responsible for accurately placing and fixing the new pipe section in place, ensuring that the connection between the new pipe section and the pipeline interface is tight and sealed, and then using underwater welding technology to weld the pipe sections. After ensuring that there is no leakage at the welding point through real-time monitoring and sensor detection, conduct underwater pressure testing and quality inspection to verify the repair effect; After completion, check and clean the entire maintenance area; Among them, the plan Dr Under this plan, the pipeline reliability recovery degree is 0.065 - 0.1.

[0083] It should be noted that for the characteristics of the maintenance type of reducing the failure probability of the external operation risk of aging submarine pipelines, four specific maintenance operation plans are divided, including plan Af 、plan Bf 、plan Cf and plan Df .

[0084] (1) Solution Af : For the suspension of submarine pipelines, an underwater support pile solution is adopted. According to factors such as the length of the pipeline suspension section, water flow velocity, and pipeline diameter, the spacing of the support piles is reasonably determined and evenly arranged along the pipeline suspension section to form a stable support system, reducing the lateral and longitudinal vibration amplitudes of the vortex-induced vibration generated by the pipeline suspension section under the action of water flow and shortening the pipeline suspension length. First, use sonar scanning and laser ranging technologies to accurately measure and locate the pipeline sections that need to be reinforced, drill holes at key positions and install underwater support piles made of high-strength materials to ensure that the pile foundations penetrate deep into the seabed rock layer; then use cement slurry or resin materials to fix the support piles in place and carry out structural reinforcement to provide stable support force, and use underwater camera equipment and pressure sensors to monitor the stability of the support piles in real time and make adjustments and reinforcements as needed; finally, use asbestos pipes, iron rods and other materials to reinforce the underwater support piles to prevent the waves from deforming and breaking them; among them, the solution Af under, the range of reduction in the pipeline failure probability is 0.01 - 0.025.

[0085] (2) Solution Bf : Use a dredging equipment to transport slurry or bottom mud to the designated area and use the sedimentation characteristics of the slurry itself to reinforce the foundation and eliminate the pipeline overhang; or use a suspended jet trencher to cut the slope at the high point of the overhang, so as to level the landform, that is, by using high-pressure water jet to wash away the soil under the submarine pipeline to form a trench. After the submarine pipeline sinks into the trench, the disturbed soil beside the trench is backfilled by the movement of sea current or waves, and then sand bags are dumped in the backfilled area to ensure that the sand bags are arranged tightly and cover the entire pipeline surface. Bionic waterweeds are installed on the surface of the sand bags, which are made of polymer materials and simulate the shape and function of natural waterweeds; use underwater camera and flow velocity monitoring equipment to monitor the flow reduction effect of the bionic waterweeds and the stability of the sand bags, and carry out maintenance as needed; among them, the solution Bf under, the range of reduction in the pipeline failure probability is 0.025 - 0.055.

[0086] (3) Solution Cf : First, use a multibeam echo sounder and a terrain scanner to conduct a detailed survey of the seabed terrain and pipeline alignment, select the appropriate dumping positions and quantities according to the terrain data, and use a stone dumping ship or an underwater robot for precise dumping. Interlocking rows are set between the dumped stone sand bags, using high-strength interlocking structural materials and fixed by underwater welding or connecting devices, and use underwater vibration sensors and flow velocity monitors to evaluate the stability of the interlocking rows and sand bags. However, with the increase in water depth and the change of environmental conditions, it is difficult to meet the high-precision requirements of the stone dumping method, and the cost of the stone dumping ship is relatively high; among them, the solution Cf under, the range of reduction in the pipeline failure probability is 0.055 - 0.09.

[0087] (4) Solution Df: Prefabricate on land and conduct equipment commissioning, and mobilize the equipment for loading onto the ship. Anchor the ship in place at sea, and retrieve the anchor chain and obstacles. Subsequently, conduct trenching and exposure on both sides of the anchor abandonment point and at the cutting point, clean the coating and add counterweights, cut and replace the submarine pipeline and retrieve the abandoned anchor and waste pipe; install mechanical connectors, prefabricate straight pipe sections, and conduct self-pressure testing; after passing the pressure test, drain the production line and install flange protectors. Finally, resume the production of the ship, equipment, and personnel, and conduct subsequent operations such as transshipment and discharging; among them, the plan Df Under this condition, the range of reduction in pipeline failure probability is 0.09 - 0.14.

[0088] In this Example 1, assume that the submarine pipeline undergoes 3 times, 4 times, 5 times, and 6 times of maintenance plans during the aging period and the extended service life respectively. Set the maximum number of feasible solutions of NSDBO to 600, and the maximum number of iterations to 100, and calculate the number of non-dominated solutions in the archive; when searching and optimizing 100 times, stop the iteration and output the optimal solution set, that is, output the best maintenance time point; NSDBO considers the balance between global exploration and local development during the optimization process, and can widely search for possible solutions within the entire search space, and then conduct fine search near the potential high-quality solutions that have been found to calculate the optimal solution; in addition, various strategies adopted during the search process, such as simulating the foraging, stealing, and breeding behaviors of dung beetles, enhance the global exploration ability and development ability of the algorithm, and avoid premature convergence to the local optimal solution.

[0089] As shown in the Figure 7 appendix Figure 7 gives the predicted results of the reliability and cost Pareto solution sets under different maintenance times in Example 1; as can be seen from the Figure 7 appendix, when the number of maintenance times is 3, the sparse area of the Pareto solution set is relatively large, and the optimal solutions are relatively scattered; this indicates that when only setting three times of maintenance, the trade-off relationship between reliability and cost is relatively complex and unstable, and there are a small number of solutions that can achieve both high reliability and low cost, that is, when the maintenance frequency is low, the effectiveness of single maintenance is not sufficient to significantly improve the overall reliability of the pipeline, and the increased cost cannot fully offset this deficiency; when the number of maintenance times increases to 4 times, the Pareto solution set and the optimal solution set become dense as a whole, and the trade-off relationship between cost and reliability is relatively stable and has high robustness; when the number of maintenance times further increases to 5 times, although the single maintenance cost decreases, the overall cumulative cost is still relatively high, and the reliability improvement speed of the aggregated part of the optimal solutions is relatively slow. Therefore, although the maintenance frequency is increased, the marginal benefit of single maintenance gradually decreases and cannot significantly improve the overall system reliability; when the number of maintenance times reaches 6 times, the optimal solution under the lowest cost increases by 14% compared with setting 4 times of maintenance, but the reliability decreases by 22%, reflecting that over-maintenance not only increases the overall cost, but also interferes with the normal operation of the pipeline system due to frequent maintenance.

[0090] In this embodiment 1, based on the TOPSIS method, the optimal solution set is sorted and analyzed, and it can be found that when the maintenance times are n =3, the maintenance degree is 0.027, which is the Pareto optimal solution, indicating that the maintenance solution is adopted in this case. Ar The performance is superior, that is, based on the Beaver maintenance equipment, the epoxy resin glass fiber layer is used to repair the pipe joints and cracks, and the steam pressure is used to expand it and adhere to the pipe wall to form a protective layer on the surface of the pipe to prevent further corrosion and degradation of the pipe body; although some solutions significantly improve the recovery of the pipeline system after a single maintenance, due to the high cost, these solutions can only be regarded as suboptimal choices in the overall evaluation. With the increase of the set maintenance times, the maintenance degree shows a fluctuating trend. The maintenance degree of the top-ranked better solutions has increased overall, but it is still low in the entire optimal solution set, which indicates that at a higher maintenance frequency, the maintenance investment can be appropriately increased to obtain a relatively high performance improvement; however, when the maintenance times increase to 6 times, the advantage of low maintenance degree gradually weakens. At this time, the optimal solution is more inclined to a maintenance plan with a higher maintenance degree. Therefore, in the case of frequent maintenance, although the cost of a single maintenance may be low, the cumulative benefits of overall maintenance gradually emerge, prompting the pipeline system to rely on a higher degree of maintenance plan to maintain longer pipeline operation stability, such as by accurately positioning and firmly sealing the simple caisson, installing welding equipment for pipeline welding repair, including removing microbial attachment, filling micro-pits, and pipeline welding. This trend shows that when the maintenance frequency is small, a high maintenance level can significantly improve the pipeline reliability recovery, but it will lead to a sharp increase in costs; as the maintenance frequency increases, the system can achieve better performance improvement accumulation through a lower level of single maintenance, but after reaching a certain number of times, the effect of low maintenance level weakens, forcing the pipeline system to rely on a higher maintenance level strategy.

[0091] As attached Figure 8 As shown, attached Figure 8 The prediction results of the risk and cost Pareto solution set under different maintenance times in Example 1 are given in the attached Figure 8 It can be seen from the figure that when the maintenance times are 3 and 6, the sparse area of ​​the Pareto solution is large, the optimal solution is dispersed, the balance between failure risk and cost is complex and unstable, and it is difficult to find a solution that satisfies both low cost and low risk. n =3, the optimal solution dense area failure probability distribution range is unstable, and the cost is higher than other maintenance frequencies. nWhen \(n = 6\), there are relatively few optimal solutions in the solution set, but the range of the failure probability distribution gradually stabilizes. However, due to the increase in the number of maintenance operations, the cost remains relatively high. When the number of maintenance operations increases to 4 times, the Pareto solution set and the optimal solution set become dense, and the relationship between cost and risk tends to stabilize. However, the maintenance strategy of performing four maintenance operations during the pipeline life extension period mainly achieves optimality in terms of cost, that is, the maintenance measures are almost evenly distributed during the pipeline life extension period. However, due to the long interval between maintenance periods, some potential risk hazards cannot be detected in a timely manner. When the number of maintenance operations increases to 5 times, although the cumulative maintenance cost increases, the pipeline failure probability is relatively low under the optimal solution set scheme, and the marginal benefit of the maintenance frequency increases, that is, the risk reduction effect brought by each additional maintenance is relatively prominent compared to the increased cost.

[0092] In this Example 1, by performing a ranking analysis on the optimal solution set based on the TOPSIS method, it can be found that the optimal maintenance and repair levels vary under different risk-based maintenance schemes and different numbers of maintenance operations. When the number of maintenance operations is 3 times, the optimal maintenance level is relatively high, that is, at a relatively low maintenance frequency, a higher-intensity maintenance scheme needs to be selected to effectively control the pipeline operation risk. For example, by adopting Scheme Cf , after using a multibeam echo sounder and a terrain scanner to conduct a detailed survey of the seabed topography, precise filling is carried out by a stone dumping vessel or an underwater robot, and interlocking rows are set up. Through the cooperation of high-strength interlocking structural materials, underwater vibration sensors, and flow velocity monitors, the stability of the interlocking rows and sandbags is ensured. Although this maintenance strategy can significantly reduce risks in the short term, the corresponding cost will also be relatively high. With changes in ocean currents and environmental conditions, it is difficult to meet the high-precision requirements of the stone dumping method, and the cost of the stone dumping vessel is relatively high, making it difficult to maintain in the long term to meet the long-term pipeline life extension requirements. When the number of maintenance operations increases to 4 times, the overall change in the optimal maintenance level is relatively small, and the differences between the solution sets of each maintenance scheme are not significant. At this time, the total maintenance cost is reasonably controlled. For example, by adopting Scheme Af , underwater support piles are used to reinforce the submarine pipeline. However, due to the excessively long maintenance period and limited maintenance time for the underwater support piles, the overall risk level of the pipeline system remains relatively high. As the number of maintenance operations further increases to 5 times, both the optimal maintenance intensity and frequency are at a medium level. For example, the method of combining dredging sedimentation and bionic waterweeds is adopted. The soil under the submarine pipeline is washed away by high-pressure water jets to form a trench, the pipeline is sunk into the trench, and the stability is increased by dumping sandbags and bionic waterweeds. This maintenance strategy can effectively control risks while avoiding excessive cumulative maintenance costs and overly long intervals between maintenance periods. When the number of maintenance operations reaches 6 times, the optimal maintenance level is the same as the sub-optimal maintenance level, indicating that in the case of frequent maintenance, the strength and effect that can be restored by a single maintenance tend to be the same. Although frequent maintenance can continuously control the pipeline operation risk, the overall cost increases significantly.

[0093] As shown in the appendix Figure 9 shown in the appendix Figure 9The updated prediction results of the remaining life of the aged subsea pipeline under different maintenance frequencies and scenarios in Embodiment 1 are given; as shown in the appendix Figure 9 It can be seen from the appendix that when the maintenance frequency of the maintenance plan is 3 times, the optimal maintenance nodes appear in the 16th year, 17th year, and 23rd year respectively, and the predicted service life of the pipeline can be extended to the 25th year. Although the number of maintenance times is small, effective maintenance at the critical nodes of pipeline reliability degradation can still significantly extend the service life of the pipeline; when the maintenance frequency increases to 4 times, the optimal maintenance nodes are the 15th year, 19th year, 22nd year, and 26th year respectively, and the predicted service life of the pipeline can be extended to the 28th year, showing a good balance between pipeline reliability recovery and maintenance cost. When the maintenance frequency increases to 5 times, the optimal maintenance nodes are located in the 16th year, 18th year, 21st year, 23rd year, and 25th year respectively, and the predicted service life of the pipeline is the 27th year. Although this maintenance plan increases the number of maintenance times, the overall life extension is not significant, and there is a large diminishing marginal benefit of maintenance; when the maintenance frequency reaches 6 times, the optimal maintenance nodes are the 15th year, 17th year, 19th year, 22nd year, 25th year, and 28th year respectively, and the predicted service life of the pipeline can be extended to the 30th year. Although the maintenance frequency is the highest and covers more critical pipeline degradation maintenance nodes, the cost also increases accordingly; considering cost, risk control, and life extension effect comprehensively, performing four maintenance frequencies within the aging cycle of this pipeline is an ideal choice.

[0094] The decision-making method for the maintenance plan of the aged subsea pipeline described in Embodiment 1 uses a pre-constructed non-homogeneous surface pitting model of the subsea pipeline to predict the crack propagation and evolution characteristics. By optimizing the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model, the remaining life of the subsea pipeline to be maintained under different maintenance plans can be obtained; based on the remaining life of the subsea pipeline to be maintained under different maintenance plans, different maintenance plans are evaluated to obtain the optimal maintenance plan; among them, when constructing the maintenance optimization model, multiple objectives such as reliability, risk, and cost-benefit ratio are comprehensively considered, and a maintenance plan that can achieve the best balance among reliability, risk, and economy can be sought; the present invention significantly improves the scientificity and accuracy of decision-making by introducing data-driven, model prediction, and multi-objective optimization. It not only solves the problems existing in traditional decision-making methods but also provides new ideas and methods for the maintenance management of subsea pipelines. With the continuous popularization and application of this method, it is believed that it will provide more powerful guarantees for the safe and reliable operation of subsea pipelines.

[0095] Embodiment 2 As shown in the appendix Figure 10 This Embodiment 2 provides a decision-making system for the maintenance plan of an aged subsea pipeline, including: a data acquisition module, an evolution prediction module, an optimization model module, a multi-objective optimization module, and a multi-objective optimization module.

[0096] A data acquisition module for acquiring the structural attribute data and pitting feature data of the submarine pipeline to be maintained; an evolution prediction module for predicting the crack propagation evolution characteristics of the submarine pipeline to be maintained by using a pre-constructed heterogeneous surface pitting model of the submarine pipeline based on the structural attribute data and pitting feature data of the submarine pipeline; an optimization model module for constructing a reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the submarine pipeline to be maintained with the maintenance plan of the submarine pipeline to be maintained as the optimization variable based on the crack propagation evolution characteristics of the submarine pipeline to be maintained; a multi-objective optimization module for optimizing the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the submarine pipeline to be maintained to obtain the remaining life of the submarine pipeline to be maintained under different maintenance plans; a multi-objective optimization module for evaluating different maintenance plans based on the remaining life of the submarine pipeline to be maintained under different maintenance plans to obtain the optimal maintenance plan of the submarine pipeline to be maintained.

[0097] Embodiment 3 As shown in the appendix Figure 11 As shown, Embodiment 3 of the present invention provides an electronic device, including: a memory for storing a computer program; a processor for implementing the steps of the decision-making method for the maintenance plan of the aged submarine pipeline when executing the computer program; or, the processor implements the functions of each module in the above-mentioned decision-making system for the maintenance plan of the aged submarine pipeline when executing the computer program.

[0098] Exemplarily, the computer program can be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of completing preset functions, and the instruction segments are used to describe the execution process of the computer program in the electronic device.

[0099] The electronic device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that the above are examples of the electronic device and do not constitute a limitation on the electronic device. It may include more components than the above, or combine some components, or different components. For example, the electronic device may further include an input / output device, a network access device, a bus, etc.

[0100] The so-called processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor is the control center of the electronic device and connects all parts of the entire electronic device through various interfaces and circuits.

[0101] The memory can be used to store the computer program and / or modules. The processor realizes various functions of the electronic device by running or executing the computer program and / or modules stored in the memory, and by calling the data stored in the memory.

[0102] The memory may mainly include a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the mobile phone (such as audio data, phone book, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one magnetic disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0103] Embodiment 4 Embodiment 4 of the present invention also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the decision-making method for an aging submarine pipeline maintenance plan are realized.

[0104] If the modules / units integrated in the aging submarine pipeline maintenance plan decision-making system are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer-readable storage medium.

[0105] Based on such understanding, all or part of the processes in the above-mentioned decision-making method for the maintenance plan of aged subsea pipelines of the present invention can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned decision-making method for the maintenance plan of aged subsea pipelines can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or preset intermediate form, etc.

[0106] The computer-readable storage medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0107] Embodiment 5 Embodiment 5 of the present invention provides a computer product. The computer program product includes a computer program, and the computer program is stored in a computer-readable storage medium; the processor of the electronic device reads the computer program from the computer-readable storage medium, and the processor executes the computer program, so that the electronic device can execute the decision-making for the maintenance plan of the aged subsea pipeline described in Embodiment 1, which will not be elaborated here.

[0108] It should be noted that those of ordinary skill in the art can understand that all or part of the processes in implementing the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the above embodiments of the respective methods.

[0109] The above embodiments are only one of the implementation manners capable of implementing the technical solutions of the present invention. The scope of protection required by the present invention is not only limited by this embodiment, but also includes any changes, substitutions, and other implementation manners that are easily conceivable by those skilled in the art within the technical scope disclosed by the present invention.

Claims

1. A decision-making method for the maintenance plan of aging submarine pipelines, characterized in that, Including: Obtain the structural attribute data and pit corrosion characteristic data of the submarine pipeline to be maintained; According to the structural attribute data and pit corrosion characteristic data of the submarine pipeline, use the pre-constructed heterogeneous surface pitting model of the submarine pipeline to predict the crack propagation and evolution characteristics of the submarine pipeline to be maintained; Based on the crack propagation and evolution characteristics of the submarine pipeline to be maintained, taking the maintenance plan of the submarine pipeline to be maintained as the optimization variable, construct a multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained; Optimize the multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained to obtain the remaining life of the submarine pipeline to be maintained under different maintenance plans; Based on the remaining life of the submarine pipeline to be maintained under different maintenance plans, evaluate different maintenance plans to obtain the optimal maintenance plan for the submarine pipeline to be maintained.

2. The decision-making method for the maintenance plan of aging submarine pipelines according to claim 1, wherein, The structural attribute data of the submarine pipeline to be maintained includes the pipeline material, inner diameter, length and wall thickness of the submarine pipeline to be maintained; the pit corrosion characteristic data of the submarine pipeline to be maintained includes the pit size, pit agglomeration degree and corrosion pit spacing coefficient on the submarine pipeline to be maintained; among them, the pit size includes the pit depth and the pit width.

3. A decision-making method for the maintenance plan of aging submarine pipelines according to claim 1, characterized in that The pre-constructed heterogeneous surface pitting model of the submarine pipeline includes a single-pit defect pipeline model, a double-corrosion-pit defect pipeline model, a triple-pit defect pipeline model and a heterogeneous group-pit defect pipeline model.

4. The decision-making method for the maintenance plan of aging submarine pipelines according to claim 1, characterized in that The multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained includes a pipeline reliability degradation objective function, a pipeline risk failure probability objective function and a pipeline cost objective function; The pipeline reliability degradation objective function is as follows: Among them, is the reliability index at the first service time node; is the pipeline operation year; is the number of pipeline reliability maintenance times; is the depth of the is the reliability index at the second service time node; is the reliability index at the third service time node; The pipeline risk failure probability objective function is as follows: Among them, is the pipeline failure probability; is the number of pipeline failure maintenance times; is the depth of the -th pipeline failure maintenance behavior; The pipeline cost objective function is as follows: Among them, is the total cost-benefit; is the total life cycle risk assessment cost; is the direct inspection and repair cost; is the indirect inspection and repair cost.

5. The decision-making method for the maintenance plan of aging submarine pipelines according to claim 1, characterized in that, Use the improved dung beetle multi-objective optimization algorithm to optimize the multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained to obtain the remaining life of the submarine pipeline to be maintained under different maintenance plans; Among them, the improved dung beetle multi-objective optimization algorithm is a dung beetle multi-objective optimization algorithm introduced with a dynamic parameter adjustment strategy, an adaptive search strategy and an environmental response mechanism.

6. The decision-making method for the maintenance plan of aged submarine pipelines according to claim 1, characterized in that, The process of evaluating different maintenance plans based on the remaining life of the submarine pipeline to be maintained under different maintenance plans to obtain the optimal maintenance plan for the submarine pipeline to be maintained is as follows: Based on the remaining life of the submarine pipeline under different pipeline maintenance plans, use the TOPSIS method to rank different pipeline maintenance plans; According to the ranking results of different pipeline maintenance plans, obtain the optimal maintenance plan for the submarine pipeline to be maintained.

7. An aging submarine pipeline maintenance plan decision-making system, characterized in that, Including: A data acquisition module for obtaining the structural attribute data and pit corrosion characteristic data of the submarine pipeline to be maintained; An evolution prediction module for predicting the crack propagation and evolution characteristics of the submarine pipeline to be maintained according to the structural attribute data and pit corrosion characteristic data of the submarine pipeline, using the pre-constructed heterogeneous surface pitting model of the submarine pipeline; An optimization model module for constructing a multi-objective maintenance optimization model of reliability-risk-cost-benefit ratio for the submarine pipeline to be maintained based on the crack propagation and evolution characteristics of the submarine pipeline to be maintained, taking the maintenance plan of the submarine pipeline to be maintained as the optimization variable; The multi-objective optimization module is used to optimize the reliability-risk-cost-benefit ratio multi-objective maintenance optimization model of the submarine pipeline to be maintained, and obtain the remaining life of the submarine pipeline to be maintained under different maintenance schemes; The evaluation and decision-making module is used to evaluate different maintenance schemes based on the remaining life of the submarine pipeline to be maintained under different maintenance schemes, and obtain the optimal maintenance scheme for the submarine pipeline to be maintained.

8. An electronic device, characterized in that, It includes: A processor suitable for executing computer programs; A computer-readable storage medium storing a computer program, which when executed by the processor, implements the decision-making method for the maintenance scheme of the aged submarine pipeline according to any one of claims 1-6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the decision-making method for the maintenance scheme of the aged submarine pipeline according to any one of claims 1-6.

10. A computer program product, characterized in that, The computer program product includes a computer program, which when executed by the processor, implements the decision-making method for the maintenance scheme of the aged submarine pipeline according to any one of claims 1-6.

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