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Pipeline plays an important role in oil and gas transportation. With the increase of service life of pipeline, it is easy to produce various forms of defects. Combined with the field conditions, ANSYS simulation software was used to built a non-destructive natural gas pipeline and a pipeline with internal corrosion defects. By compared the pressure check and stress check conditions, the accuracy of the simulation model was verified. The linear regression model was established to analyze the maximum stress value of the defective pipe under different internal pressure. Subsequently, a smart sleeve repair technology was proposed for the defective pipeline, and a sleeve repair model was established for the defective pipeline. The influence of different epoxy layer thickness on the reinforcing effect of the defective pipeline was studied, the optimal epoxy layer thickness was determined, and experiments and field verification were carried out. The smart sleeve monitoring system was used for real-time strain monitoring of pipeline defects. Based on the collected real-time strain data, the effectiveness of pipeline defect reinforcement was confirmed, which provided a practical application method for the repair of pipeline defects and the evaluation of the effect after repair. [ABSTRACT FROM AUTHOR]

Failure analysis is a vital technique that is intended to strengthen the integrity management of oil and gas pipelines. The significance is to reduce economic losses and avoid or minimize major failure incidents. The aim of this study is to use bibliometric methods to research 2,533 papers retrieved from the Web of Science database spanning from 2004 to 2023. The analysis conducted using VOSviewer, focused on temporal trends, geographic distribution, major organizations, leading authors, journal co-citations, and literature co-citations. The objective is to uncover research hotspots and frontiers, providing insights to advance failure analysis and prevention techniques. The findings revealed a substantial surge in the number of papers related to failure analysis, escalating from 16 in 2004 to 190 in 2023, indicating an overall exponential growth trend. This growth has been most pronounced over the past 8 years. Noteworthy contributors to this field include China, the USA, Canada, England, and Iran, with Iran, Australia, and Italy exerting significant impact. In addition, the top three research producers are all from institutions or universities located in China. The journals Engineering Failure Analysis, International Journal of Pressure Vessels and Piping, and Journal of Loss Prevention in the Process Industries exhibit the highest publication numbers. Significantly, Journal of Loss Prevention in the Process Industries and Gas Science and Engineering emerge as influential and highly regarded publications within this field. The study revealed that while the foundational theory and research framework in oil and gas pipeline failure have crystallized, a plethora of research directions and cutting-edge branches continue to emerge. Notably, the study of failure possibilities and behavior through Bayesian networks, failure characterization analysis, and finite element methods have emerged as the primary development directions and research hotspots. In terms of innovation, the application of bibliometric methods has enhanced the capacity to handle extensive literature databases and conduct network analyses. This study furnishes a theoretical foundation and guidance for the advancement of failure analysis and prevention techniques in the field of oil and gas pipelines. [ABSTRACT FROM AUTHOR]

Oil and gas pipeline safety analyses aim to enhance the integrity management and operational safety of pipelines to prevent major incidents. This study seeks to provide a comprehensive overview of the evolution of research hotspots and knowledge frontiers in global oil and gas pipeline safety. A bibliometric data mining method was adopted to systematically sort out 2,582 studies in the field of oil and gas pipeline safety retrieved from the core database of Web of Science from 2000 to 2023. A bibliometric network analysis was conducted to investigate the distribution of papers in terms of time, geographic region, organization, main author, journal cocitation, and literature cocitation, and to identify the research hotspots and frontiers. The findings revealed that the number of papers on oil and gas pipeline safety has surged from 10 in 2000 to 327 in 2023, reflecting an overall exponential growth trend. Key research contributions in this field predominantly originate from institutions such as the China University of Petroleum (Beijing), Southwest Petroleum University, and China University of Petroleum (East China). These institutions, located primarily in China, have had a significant impact on the field. Notable researchers, including Li Yuxing, Faisal Khan, and Zhang Hong, have made substantial contributions. Leading journals, such as Journal of Loss Prevention in the Process Industries, Process Safety and Environmental Protection, and Energies, have published the highest number of influential papers in this area. The research indicates that although a foundational theory and research framework for oil and gas pipeline safety have been established, numerous research directions and cutting-edge branches continue to emerge. Prominent among these are studies focusing on pipeline reliability analysis, risk assessment, failure prediction, leakage, and multiphase flow assurance, using numerical simulations and machine learning techniques. This study provides a theoretical basis and practical guidance for advancing oil and gas pipeline safety analysis and accident prevention. [ABSTRACT FROM AUTHOR]

The traditional magnetic flux leakage (MFL) detection technology is difficult to meet the requirements of steel oil and gas pipeline crack detection, a new residual magnetic flux leakage (RMFL) detection technology was proposed, which directly used the residual magnetic state of the pipe wall after MFL detection to realize the effective detection of small opening cracks. Compared with magnetic leakage signal, remanent signal had lower signal-to-noise ratio and higher requirement on sampling frequency of sensor. Therefore, a spatial resolution method was proposed to optimize sampling frequency of remanent signal. Firstly, the dynamic magnetization model of pipeline was established by finite element simulation, the crack characteristic data was extracted, and the distribution law was analyzed. Secondly, the frequency domain analysis method was used to optimize the sampling frequency of residual magnetic signal. Finally, the effectiveness of the crack remanence detection method based on spatial resolution was verified by experiments. The results show that the remanent signal based on spatial resolution is highly consistent with the original signal, and there are undistorted sampling points at the poles of the signal waveform, which preserves the key features of the original signal and provides an important data basis for quantifying the crack size. This technology can realize the effective detection of cracks in small openings of pipelines, and has strong engineering practicality and operability, which is conducive to the further development of crack detection technology in oil and gas pipelines. [ABSTRACT FROM AUTHOR]

Oil and gas pipelines are subject to soil corrosion and medium pressure factors, resulting in stress concentration and pipe rupture and explosion. Non-destructive testing technology can identify the stress concentration and defect corrosion area of the pipeline to ensure the safety of pipeline transportation. In view of the problem that the traditional pipeline inspection cannot identify the stress signal at the defect, this paper proposes a detection method using strong and weak magnetic coupling technology. Based on the traditional J-A (Jiles–Atherton) model, the pinning coefficient is optimized and the stress demagnetization factor is added to establish the defect of the ferromagnetic material. The force-magnetic relationship optimization model is used to calculate the best detection magnetic field strength. The force-magnetic coupling simulation of Q235 steel material is carried out by ANSYS 2019 R1 software based on the improved J-A force-magnetic model. The results show that the effect of the stress on the pipe on the magnetic induction increases first and then decreases with the increase in the excitation magnetic field strength, and the magnetic signal has the maximum proportion of the stress signal during the excitation process; the magnetic induction at the pipe defect increases linearly with the increase in the stress trend. Through the strong and weak magnetic scanning detection of cracked pipeline materials, the correctness of the theoretical analysis and the validity of the engineering application of the strong and weak magnetic detection method are verified. [ABSTRACT FROM AUTHOR]

With the high-quality development and construction of national economic and livelihood projects, oil and gas have become an important strategic reserve resource for China's economic, political and military security, and the foundation and driving force for comprehensive development and modernization. Among them, the oil and gas pipelines used to transport oil and natural gas are known as the main arteries of national energy development. Due to the high flammability and explosiveness of oil and gas products, the high risk in the operation of oil and gas pipelines, the large number of key components of infrastructure and the complexity of the system, and the frequent occurrence of oil and gas pipeline failure accidents at home and abroad, the research on the prevention and control of oil and gas pipelines in China is still lacking in systematization. This paper systematically reviews the development trend of accident causation theory, leakage monitoring technology and numerical simulation research at home and abroad, and on this basis, summarizes the challenges faced in constructing a systematic accident causation analysis model and the whole life cycle detection simulation, so as to provide a reference for improving the operation safety of oil and gas pipelines in China. [ABSTRACT FROM AUTHOR]

As the lifeblood of national energy, oil and gas pipelines are vulnerable to corrosion, third-party damage, and natural disasters. Among these, third-party damage accidents have a high probability and serious consequences. However, China lacks a mature and unified pipeline accident database, making it difficult to assess and manage the risk of such incidents. To address this issue, this paper identifies 20 key risk factors for third-party damage to oil and gas pipelines through literature and case studies. The paper then proposes a multistate probabilistic assessment model using the Decision-Making Trial and Evaluation Laboratory (DEMATEL), interpretative structural modeling method (ISM), Røed method, and Bayesian network (BN). Real case studies demonstrate that the model not only predicts the probability of third-party damage risks but also clearly identifies key influencing factors and causal chains in the risk system. This provides a new approach for assessing third-party damage risks to oil and gas pipelines and offers a scientific basis for decision-making in managing actual pipelines. Practical Applications: The high probability and serious consequences of third-party damage accidents of oil and gas pipelines have caused certain hidden dangers to social security, environment, and economy, and put forward higher requirements for pipeline operation and management. In order to scientifically manage and effectively control the occurrence of third-party damage accidents of oil and gas pipelines, this paper, in the absence of an applicable pipeline failure database. Based on expert knowledge, a model that can be used for the assessment and prediction of third-party damage probability of oil and gas pipelines is constructed. Through the application of real cases, it is shown that the model can be used not only to predict the probability of third-party damage of oil and gas pipelines, but also to identify the key influencing factors and key causal chains leading to third-party damage. The results of the study not only provide theoretical support for pipeline management in reality, but also provide new ideas for risk assessment of oil and gas pipelines that lack actual data. [ABSTRACT FROM AUTHOR]

The problem of corrosion in oil and gas pipelines is one of the major factors affecting the process safety and efficient sustainability development of the oil and gas industry. To gain a better understanding of global research trends and dynamics in the field of oil and gas pipeline corrosion and to advance the development of corrosion control technology, we conducted a literature review using a sample of 1,745 papers from the Web of Science (WOS) database published from 2002 to 2022. We employed a bibliometric analysis approach employed to investigate the distribution of publications over time, geographic regions, major organizations, major authors, journal cocitation, and literature cocitation, and to identify research hotspots and frontiers. The results revealed an exponential growth in the overall number of papers, with the most rapid increase occurring in the last 4 years. China, the US, Canada, the United Kingdom, and Brazil emerged as the most active countries in oil and natural gas pipeline corrosion research, and Mexico, Canada, and Australia also exhibited significant influence in the field. The journals Engineering Failure Analysis, Corrosion, and Corrosion Science had the highest number of publications and impact in this domain. Notably, Corrosion Science stood out as the most influential and highly regarded journal in the corrosion field. The fundamental theories and research framework in the realm of oil and natural gas pipeline corrosion have been primarily established, and a large number of research directions and frontier branches are emerging. The impact of flow parameters on corrosion, pipeline reliability assessment, and analysis of corrosion defects and failures are identified as the three main development paths in this field. In terms of research methodologies, machine learning techniques are becoming increasingly prevalent, with a growing number of studies adopting various machine learning methods. Among these methods, explainable deep learning is at the forefront of development in the field of oil and natural gas pipeline corrosion. [ABSTRACT FROM AUTHOR]

ASTM A106 B grade is used to manufacture seamless steel pipe, which can be used at high temperature, pressure, and hard environmental conditions for oil and gas supplies but suffers from corrosion. Polyurea is an organic coating that is resistant to moisture, UV light, and chemicals and has a high range of service temperatures. In this study, the effect of polyurea coating with the addition of copper nanoparticles was investigated for improvement of anti-corrosion and mechanical behavior in 3.5 % NaCl solution for A106 steel. Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) tests were performed to examine anticorrosion properties, Scanning Electron Microscopy (SEM) was used to examine quality coating, thickness, and distribution of copper nanoparticles. Wear, hardness, and tensile tests were performed to check mechanical properties. The corrosion rate decreases from 0.16264 mpy to 0.01376 mpy while coating resistance increases from 2.95 × 104 Ω cm2 to 2.474 × 105 Ω cm2. An increasing trend was observed during the tensile test for pure polyurea and pure polyurea with 2 % copper nanoparticles. i.e., 501 MPa and 536 MPa, respectively. Results showed pure polyurea and polyurea with copper nanoparticles on steel improve its anti-corrosion and mechanical properties significantly.

[Objective] In light of a growing number of oil and gas pipelines crossing or running near power lines,the issue of lightning overvoltage at these locations has garnered increasing attention within these two industries. [Methods] In this study,a calculation model was developed using COMSOL Multiphysics software to depict the generation mechanism of potential difference between pipelines and their anticorrosive coatings at locations where these pipelines cross or run near power lines.Simulation calculations were performed to analyze the impact of soil resistivity and soil layering on pipeline overvoltage amplitude.As a result,a pipeline overvoltage protection method was proposed,considering the dispersion of current over the grounding grids at nearby towers/poles. [Results] The simulation results confirmed the effectiveness of the proposed optimization solution in limiting the voltage,establishing its practical application value.Although the potential on the pipelines and the withstand voltage of their anticorrosive coatings were generally balanced,the difference between them was notably influenced by the direction of current dispersion from the grounding electrodes.Under typical soil resistivity conditions,the withstand voltage difference between the pipelines and their anticorrosive coatings remained within limits.Additionally,it was observed that individual lightning discharges alone were insufficient to cause breakdown in the three-layer polyethylene (3PE) anticorrosive coatings.However,the withstand potential difference did contribute to the enlargement of local damage points that already existed within the coatings.To mitigate the withstand potential difference,an effective approach is proposed involving adjustments to the included angle and relative distance between the pipelines and grounding electrodes at nearby towers/poles. [Conclusion] It is proposed to effectively reduce the potential difference between pipelines and their anticorrosive coatings by modifying the configuration and current dispersion dimensions of the grounding grids at nearby towers/poles.With proven technical feasibility and economical efficiency,the findings of this study serve as a valuable reference for the design,construction,safe operation,and maintenance of oil and gas pipelines.

Magnetic field and microorganisms are important factors influencing the stress corrosion cracking (SCC) of buried oil and gas pipelines. Once SCC occurs in buried pipelines, it will cause serious hazards to the soil environment. The SCC behavior of X80 pipeline steel under the magnetic field and sulfate-reducing bacteria (SRB) environment was investigated by immersion tests, electrochemical tests, and slow strain rate tensile (SSRT) tests. The results showed that the corrosion and SCC sensitivity of X80 steel decreased with increasing the magnetic field strength in the sterile environment. The SCC sensitivity was higher in the biotic environment inoculated with SRB, but it also decreased with increasing magnetic field strength, which was due to the magnetic field reduces microbial activity and promotes the formation of dense film layer. This work provided theoretical guidance on the prevention of SCC in pipeline steel under magnetic field and SRB coexistence. [ABSTRACT FROM AUTHOR]

The inner wall corrosion of pipelines is concealed and hard to monitor in time. In order to visualize the shape of the internally corroded pipeline, as well as the defect volume and its spatial distribution, a three-dimensional (3D) model reconstruction method based on the ultrasonic phased array technology was proposed for the internally corroded pipeline. A self-built acquisition platform was used to control the one-dimensional linear array probes for the phased array, and the reflected echo signal was used to obtain the space coordinates between the inner and outer diameters of the corroded pipeline. Then, the point cloud data set between the inner and outer diameters was constructed by the interpolation method, and the point cloud data of each fracture zone were obtained by the hierarchical scanning method. Besides, data processing, reverse model reconstruction and forward modeling were performed for the 3D model reconstruction of the collected point cloud data. Finally, the reconstructed 3D model was compared with the point cloud data obtained by the Creaform 3D laser scanner. The results show that it is feasible to obtain the point cloud data using one-dimensional linear array probes based on the ultrasonic phased array technology, and the established 3D model and defects have small errors and high precision, which has important reference value for the safety evaluation of oil and gas pipelines.

Ferromagnetic pipelines are prone to stress distortion during service, which will likely cause destructive defects, such as fatigue damage and cracks, and even major safety accidents in severe cases. This makes it particularly important to measure the stress distortion of ferromagnetic pipelines. Herein, a simulation model of pipeline stress measurement was established by the finite element software COMSOL based on the alternating current field stress measurement (ACSM) technology. Then, the characteristic signals were selected to represent the stress, which allowed us to explore the influence of probe excitation direction on stress measurement, find the optimal excitation mode, and analyze the signal variation law of the pipeline subjected to stress in different magnitudes and directions. Based on the simulation results and the characteristics of pipeline stress distribution, a set of ACSM based pipeline stress measurement system integrating the portable case and probe was designed and developed to test the tensile specimen of 45# steel and X70 steel pipeline within 0?105 MPa. The simulation and test results demonstrate that the selected characteristic signal could reflect the stress distortion because the stress distortion of pipeline causes the disturbance in electromagnetic field. The optimal excitation direction of the probe is perpendicular to the stress, and the designed portable ACSM based pipeline stress measurement system has been verified to be capable of detecting the stress distortion area of the pipeline. The research results are expected to provide references for the rapid measurement of stress distortion in ferromagnetic pipelines.

Abnormal formation of girth weld is a major threat to the safe operation of pipelines, which may lead to serious accidents. Therefore, regular inspection and maintenance of girth weld are essential for accident prevention and energy security. This paper presents a novel method for inspecting abnormal girth weld formation in oil and gas pipelines using alternating excitation detection technology. The method is based on the analysis of the microscopic magnetic variations in the welded area under alternating magnetic fields. An internal inspection probe and electronic system for detecting abnormal girth weld formation were designed and developed. The system's capability to identify misalignment, undercutting, root concavity, and abnormal formation height of girth weld was tested by numerical simulation and experimental study. The results show that the detection system can effectively identify a minimum misalignment of 0.5 mm at a lift-off height of 15 mm. The proposed method offers several advantages, such as rapid response, low cost, non-contact operation, and high sensitivity to surface flaws in ferromagnetic pipelines. [ABSTRACT FROM AUTHOR]

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The pipeline plays an important role in the transportation of energy, and its safe, reasonable and stable operation is of great significance. This study takes DN250-350 mm oil and gas pipelines as the main application scenario, and plans to design a crawler-type pipeline inspection and repair robots that use a screw nut reducing mechanism to achieve diameter reduction to achieve self-adaptive purposes. The crawler-type pipeline inspection and repair robot can be divided into a drive unit, a detection unit, a connection unit and an isolation repair unit. When the length of the constituent unit of the robot is less than 452.88 mm, it can pass through the elbow from the analysis of geometric constraints. The speed equation of the robot can be obtained by analyzing the motion state of the robot during the running process by the coordinate transformation method. The crawler robot moves more smoothly when passing through the bend with the 3-track differential characteristic. By means of simulation analysis and experimental verification, the passing ability of the elbow is verified. The research on the passing ability of the crawler-type pipeline inspection and repair robot can provide some references for the stable inspection, emergency security and treatment of oil and gas pipelines.

A new quantitative risk assessment method for hot work is proposed based on the analytic hierarchy process (AHP) and fuzzy comprehensive evaluation (FCE). It can help pipeline companies realize the risk management of hot work and further ensure the safe operation of oil and gas pipelines. Taking one natural gas pipeline in China as an example, this paper evaluates the risk of a single hot work in the spring of one natural gas pipeline in a high consequence region. First of all, the risk factors are determined with reference to the job safety analysis (JSA), and then experts were invited to fill out a questionnaire to collect their opinions. According to the results of the questionnaire, AHP is used to calculate the weight coefficients of the evaluation indicators, and FCE is used to evaluate the risk level of hot work. After calculation, the comprehensive risk score of hot work is 40.888. It belongs to a ''general risk''. This method can not only quantitatively evaluate the risk levels of hot work, but also reasonably sort the importance of various risk factors. It is helpful for the effective management of hot work and provides suggestions for implementing control measures.

Abstract Oil and gas pipelines that go through an active normal fault often deform largely and cause serious disasters. On the basis of the beam theory of the elastic foundation and assuming a shape function for the deformed pipeline, a new analytical method is proposed to calculate the pipeline strain under a normal fault. The length of the deformed pipeline is calculated by using a simplified structural mechanical model. Moreover, a three‐dimensional solid finite element model (3D FEM) is developed to calculate the pipeline strain under different working conditions. The developed analytical solution and the numerical results of 3D FEM are compared with the results of the two traditional methods (the dissipated energy method and the Karamitros method). The strain development law predicted by the proposed method and the 3D FEM is in good agreement with that of the dissipated energy method and the Karamitros method. Compared with the existing models, the new analytical method is simpler and more efficient.

Corrosion is one of the most common types of damage inburied oil and gas pipelines. Corrosion leaks can cause serious accidents and can be harmful to pipelinesduring service. The maximum corrosion depth of an oil and gas pipeline is an important indicator for assessing the remaining strength of the pipeline. An accurate prediction of the maximum corrosion depth is important for the safe operation of pipelines. Machine learning has been shown to perform well in predictive assessment efforts. However, previous studies have rarely considered the effects of corrosion characterization and parameter optimization simultaneously. In this study, a multi-parameter maximum corrosion depth prediction model for pipelines based on GSCV-XGBoost is proposed, which can be applied to real projects. The model performs feature extraction on the pipeline dataset through Pearson correlation analysis, identifies the parameters that contribute more to the maximum corrosion depth, and predicts the maximum corrosion depth of the pipeline using an optimized machine learning model. The machine learning model used in this study was obtained by optimizing the XGBoost model usingthe GirdSearchCV method. That is, the optimal hyperparameter combination of the model was obtained by 10-fold cross-validation and grid searching. The prediction results werecompared with those of five common machine learning models. The conclusions show that the GSCV-XGBoost model performs the best in predicting the maximum corrosion depth of the pipeline with the smallest error. The R2 and Root Mean Square Error(RMSE)scores forthe test set were 0.9886 and 0.2057, respectively. The prediction accuracy was improved by 34.59% over that of the conventional XGBoost model.

In order to meet the requirements of long-distance oil and gas pipelines with variable diameters of 610-762 mm for inline detection, a Magnetic Flux Leakage(MFL) inline detector applicable to such oil and gas pipelines was developed.In the new design, a folded cup was used for the sealing section, the floating structure was applied for the magnetic circuit and probes, and probes were arranged in two rows in a staggered way. Thus, the deformability of the detector was improved and the overall mechanical structure was optimized. In addition, the performance of the detector was tested through the magnetization capability test, straight pipe traction test and air tightness test. According to the test results, the magnetic circuit can meet the magnetization requirements of pipeline detection in a wall thickness of 10-20 mm, and the folded cup,with good sealing performance, can provide the detector with the required driving force. Besides, the floating effect of the magnetic circuit and probes is good for pipelines with different diameters, so that the detector could fit well with the pipeline wall to meet the detection requirements. In general, this structure of detector realizes the function of diameter variation during MFL inline detection, and plays a positive role in promoting the localization of intelligent inline detectors for oil and gas pipelines with variable diameters.

Stress Corrosion Cracking (SCC) is a failure mechanism that occurs when certain materials are subjected to both external or residual stresses and corrosion. This combined effect leads to the development of cracks in the susceptible materials. Submerged steel pipelines in the petroleum sector are built of low-alloy steels having a ferrite-cementite composition, including API 5L X70. Such materials are sensitive to SCC damage in aqueous systems. The film rupture dissolution repassivation (FRDR) process is used in this study to evaluate the cracks and pits growth in oil and gas pipelines in the Gulf area under diverse SCC environmental conditions. The SCC crack propagation and pit growth under near-neutral environmental conditions were analyzed using phase field modelling. X70 steel under NS4 the solution was used for the analysis to represent the anodic dissolution film rupture mechanism. A parametric study was done to study the impact of different electrochemistry and phase field parameters on crack growth behaviour. The study assess the susceptibility to SCC caused by an pit by employing diverse settings to evaluate the impact of corrosion parameters and the interaction among the FRDR mechanism. The corrosion rates are influenced by the interface kinetics coefficient (L), which exhibits an accelerated effect as L increases. This transition from fracture-controlled to dissolution-controlled SCC growth occurs until the system reaches the diffusion limit, beyond which further increases in L do not significantly impact corrosion rates. Moreover, higher values of the kinetic coefficient (k) advance the creation of SCC cracks at the crack front, resulting from corrosion originating from pitting at the crack mouth. This process leads to the refinement of the pit and its transformation into a crack. A comparison analysis was utilized to validate our simulation under a near-neutral NS4 solution for X70 steel by correlating the findings with other numerical methods for crack growth utilizing the same material and environmental parameters. The results show decent agreement with the comparative study.

The patrol inspection of oil and gas pipelines has the characteristics of randomness and fuzziness. In order to effectively assess the risk level of patrol inspection of buried long-distance oil and gas pipelines in tunnels, a safety risk assessment model for patrol inspection of pipelines was constructed by introducing the cloud theory and combination weighting method. Herein, study was performed on Ili‒Guozigou Pipeline of PipeChina in a tunnel group. Specifically, 29 risk factors in 6 aspects, i.e., tunnel, road network, environment, human behavior, state of object and management level, were used as the assessment indicators based on the hazard theory. Meanwhile, the weight coefficients of each indicator were determined using the improved G2 method and CRITIC (Criteria Importance Though Intercrieria Correlation) method based on the combination of Euclidean distance. The characteristic parameters of the cloud model were calculated and the cloud image was generated with Matlab software according to the classification standards of each indicator. Besides, the indicator membership degree and the comprehensive membership degree under different risk levels were determined by the forward cloud generator. The results show that the combination weighting technique based on Euclidean distance can not only reduce the subjective uncertainty of decision-makers, but also eliminate the objective errors between data. In addition, the assessment results are in good agreement with the field engineering evaluation results. The assessment model constructed has good scientificity and applicability, and is capable of providing new ideas for the risk assessment of patrol inspection of the buried long-distance oil and gas pipelines in tunnels.

Oil and gas pipelines are often exposed to the natural hazards, and the action of these natural hazards on the oil and gas pipelines may result in a series of technological hazards such as fire and explosion, which are referred to as the Natural Hazards Triggering Technological Accidents (Natech events), so that the pipelines system shows a higher vulnerability level. Herein, the relationship among risk, resilience and vulnerability was clarified by summarizing and analyzing the definition of vulnerability in different research fields. Besides, the advantages, disadvantages and applicability of various vulnerability assessment methods were reviewed, and the connotation of vulnerability in Natech events was expounded by analyzing the law of successive evolution of vulnerability. In addition, the vulnerability assessment process and crucial elements of oil and gas pipelines in Natech events were discussed from six aspects, including hazard identification, region division, etc. Finally, prospect was made in combination with the current research status for vulnerability assessment under Natech events. The research results can provide theoretical reference for quantitative vulnerability assessment of oil and gas pipelines in Natech events.

In recent years, the safety of oil and gas pipelines has become a primary concern for the pipeline industry. This paper presents a comprehensive study of the vulnerability concepts that may be used to measure the safety status of pipeline systems. The origins of the vulnerability concepts are identified, the development and evolution of the vulnerability concepts are described, and the main connotations of the four levels of vulnerability concepts applied in different fields at this stage are summarized. Qualitative and quantitative methods of vulnerability assessment are comprehensively investigated, and the advantages and disadvantages, scope of application and key issues faced are compared and summarized. The research and analysis show that the vulnerability assessment of oil and gas pipelines is at a preliminary stage, and there is an urgent demand to establish a unified vulnerability concept and assessment system for oil and gas pipeline systems. The current qualitative or semi-quantitative assessment of pipeline vulnerability research lacks reasonable and scientific standards and bases for the classification of indicators and the determination of indicator scores, and it needs to focus on the establishment and improvement of quantitative assessment models. [ABSTRACT FROM AUTHOR]

With the increase of service time, oil and gas pipelines have serious corrosion failure problems. Herein, the corrosion status of buried oil and gas pipelines in China was clarified, the common corrosion failure types of the buried pipelines were summarized, the mechanism of acid corrosion, microbial corrosion, stress corrosion cracking and hydrogen damage of oil and gas pipelines was discussed, and the effects of environmental factors such as temperature, corrosive anions, cathodic protection potential, magnetic field, and alternating current on pipeline corrosion were analyzed. In addition, discussion was performed for the present status of inadequate study on corrosion failure of buried oil and gas pipelines and the mechanism and laws that are not cleared completely, so as to provide reference for the selection of research direction of corrosion failure of buried oil and gas pipelines in the future. In terms of pitting corrosion perforation, a corrosion prediction model under the action of weak acid should be established based on the multi-phase flow model and weak acid corrosion mechanism to accurately evaluate the corrosion of oil and gas pipelines in the future, and the scanning vibration electrode technology and other means should be used to carry out in-depth research on the corrosion mechanism at the micro level: In terms of SCC, the simulation calculation method can be combined with higher resolution microscopic observation technology to analyze the nature of stress corrosion in pipelines in the future. The results of the study.

Corrosion is one of the major threats to the safety and reliability of oil and gas pipelines, making accurate prediction of corrosion rate crucial for pipeline maintenance and repairment. Traditional prediction methods often ignore more critical factors and lack interpretability, which hinders the practical application. Here, an interpretable ensemble machine learning framework is proposed, not only improving prediction performance, but also enhancing interpretability for predicting the internal corrosion rate of oil and gas pipelines. In this work, ExtraTreeRegression model has demonstrated superior prediction accuracy relative to the other five machine learning models, and the determination coefficient of the ExtraTreeRegression model achieves 0.93 after feature engineering. Then, Shapley Additive exPlanations (SHAP) values is utilized to visually interpret the model locally and globally to help account for the contributions of the input features. Furthermore, the accumulated local effect (ALE) successfully explains how the features affect the internal corrosion rate of oil and gas pipelines. By collecting corrosion data of oil and gas pipeline and performing feature engineering and data preprocessing, we construct a comprehensive and reliable prediction model with interpretability. Experimental results demonstrate that the proposed interpretable ensemble machine learning approach outperforms other models in both accuracy and interpretability, providing valuable insights for pipeline management decisions. • An interpretable ensemble machine learning framework is proposed to predict the internal corrosion rate of oil and gas pipelines. • Compared with RF, AdaBoost, GBRT, XGBoost, CatBoost, ExtraTreeRegression model can predict the internal corrosion rate of the oil and gas pipeline more accurately, and the performance index R2 value achieves 0.93 after optimization. • T (temperature), PT (pressure) and PCO2 (partial pressure of CO2) are the three most important factors affecting the internal corrosion rate of oil and gas pipeline in several evaluation methods. • The interpretations and transparency framework helps to understand and discover how environment features affect the internal corrosion rate of oil and gas pipelines. • By combining multiple single models in an ensemble framework, we can provide more accurate and reliable predictions while offering explanations for the decision-making process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Digital image correlation method is appropriate for evaluating final stress distribution. • Artificial notches at the centerline of inwardly bent sections showed failure. • Stage II is governed by a medium stress intensity factor and hydrogen-enhanced fatigue. • High stress intensity factor governs Stage III crack growth. • Stress gradient in the depth direction is a significant feature of circumferential NNpH-CF. Circumferential near-neutral pH corrosion fatigue (C-NNpH-CF) occurs when the external surface of a buried pipeline is simultaneously subjected to both axial residual stresses and applied cyclic loads while exposed to a near-neutral pH corrosive environment. The crack advance during C-NNpH-CF occurs through several stages: incubation, Stage I (crack initiation and early-stage crack growth), Stage II (sustainable crack growth), and Stage III (rapid crack propagation leading to rupture). This study aims to investigate the combined impact of bending residual stress (an appropriate source of axial residual stress) and cyclic loading (simulated pipeline pressure fluctuations) on C-NNpH-CF failure. Stress distribution was analyzed using the digital image correlation (DIC) method. At the same time, crack growth stages were examined by fractographic images under the influence of the variation of different test parameters, including cyclic loading, initial notch depth and position, and bending angle. In addition to striation analysis, Crack Mouth Opening Displacement (CMOD) and Electron Backscatter Diffraction (EBSD) analysis were employed to gain a deeper understanding of the C-NNpH-CF failure mechanism. Under the influence of maximum bending angle and axial cyclic loading, failure could occur at the bent centerline in the inward direction of the bent pipeline, where the maximum tensile stress occurs on the external surface. A high stress intensity factor governs Stage III crack growth compared to Stage II crack growth, which is governed by a medium stress intensity factor and hydrogen-enhanced fatigue. The stress gradient in the depth direction of a bent pipeline, a significant feature of C-NNpH-CF, affects crack growth rate at different stages. [ABSTRACT FROM AUTHOR]

With the development of long-distance power transmission system, the electrochemical corrosion of buried oil and gas pipelines caused by stray current is becoming more serious. In particular, the grounding current interference of High Voltage Direct Current (HVDC) transmission system will cause serious electrochemical corrosion at the defects of pipeline anti-corrosion coating, which threatens the operation safety of pipelines. In this case, the stray current density distribution along the buried pipelines close to the grounding electrode was simulated and analyzed with the COMSOL software. Meanwhile, study was performed for the influence laws of various interference parameters (including the angle between pipeline and cable of HVDC system, the grounding current, the soil conductivity, the distance between pipeline and grounding electrode, and the pipeline radius) on stray current density distribution and interference corrosion along the pipelines. The results indicate that the interference corrosion is enhanced greatly when the distance between the pipeline and any grounding electrode was less than 5 km, and it is the most serious when the angle between the pipeline and the cable is 0°. In addition, other parameters also have great influence on the interference corrosion of pipeline. Therefore, the study results could provide theoretical basis and reference for the interference protection, maintenance and inspection of pipelines.

A large number of prevention and treatment measures for geohazard have been developed by the pipeline construction and operation enterprises.However, how to apply successful disaster treatment experience to other similar pipeline geohazard prevention projects is still lack of in-depth research.The hazard points to be treated and the similar hazard points having been treated share some commonalities in terms of the development mechanism, damage mode, damage to pipelines, and the treatment method.Accordingly, a fuzzy analogy preferred retrieval model was established through case-based reasoning, so that a reasonable relationship could be built between the case to be solved(the target case)and the solved case(the base case): (1) A case base was established, comprising the identification area, attribute feature area and project construction information area.(2) The attribute features were weighted with the variable weight method.(3)The fuzzy analogy preferred relationship was established between the target and base cases of each attribute, and the fuzzy analogy preferred ratio matrix was formed.(4) The similar series between the target and base cases of different attributes were obtained by pairwise comparison.(5) The base case that is most similar to the target case was found out according to the comprehensive similar series considering the attribute weight.Although this method cannot replace the experience judgment of professional technicians on engineering prevention and treatment schemes, it is an intuitive and reasonable computer aided decision-making method.

Kazakhstan, rich in oil and gas resources, is an important hub for oil and gas transportation in Central Asia. The oil & gas storage and transportation system of Kazakhstan is an important channel to promote the energy cooperation between China and Kazakhstan, which is of great significance to realize the connectivity under the Belt and Road Initiative and ensure the energy security of China. In this study, by investigating the current situation of Kazakhstan's oil and gas channel system, the pattern of the channel system, the transit country status and the evolution process, the characteristics of Kazakhstan as an important oil and gas transportation corridor in the geopolitics of energy were analyzed. Meanwhile, the internal relationship of China with Kazakhstan in terms of energy security was especially clarified from the power of energy corridor, and on this basis, suggestions on cooperation were proposed. It is found in this study that the total transportation capacities of Kazakhstan's oil and gas pipelines are up to 1×108 t/a and 2 700×108 m3/a, with the transit capacities reaching 2 000×104 t/a and 1 900×108 m3/a, respectively. In recent years, China has participated in the construction of most new trunk pipelines in Kazakhstan, and played an important role in the diversification of Kazakhstan's energy export. Due to the limitation of geographical and market factors, Kazakhstan's dependence on Russia in crude oil export has increased from 73% to 95%, while the natural gas cooperation between Kazakhstan and China has reduced its dependence on Russia in gas export from 97% to 60%. Generally, the arrangement of northwest energy corridor in future should be based on the strategic stronghold of Kazakhstan, so as to strengthen the diversification of channel sources and routes, innovate natural gas cooperation mode, and promote the interconnection of energy channels in Central Asia.

Oil and gas pipelines that go through an active normal fault often deform largely and cause serious disasters. On the basis of the beam theory of the elastic foundation and assuming a shape function for the deformed pipeline, a new analytical method is proposed to calculate the pipeline strain under a normal fault. The length of the deformed pipeline is calculated by using a simplified structural mechanical model. Moreover, a three‐dimensional solid finite element model (3D FEM) is developed to calculate the pipeline strain under different working conditions. The developed analytical solution and the numerical results of 3D FEM are compared with the results of the two traditional methods (the dissipated energy method and the Karamitros method). The strain development law predicted by the proposed method and the 3D FEM is in good agreement with that of the dissipated energy method and the Karamitros method. Compared with the existing models, the new analytical method is simpler and more efficient. [ABSTRACT FROM AUTHOR]

In view of the low detectability and identification rate of the girth weld, crack-like and pinhole defects that generally exist in the oil and gas pipelines, a new generation of ultra-high-definition pipeline magnetic flux leakage (MFL) inline detector was independently developed through theoretical analysis, modeling and simulation, equipment research and development, field application and other links. As for the detector, the probe channel spacing is up to 0.6 mm and the axial sampling spacing is 1 mm, which meet the requirements for storage and collection of massive data. In addition, the acquisition capacity of signal data is increased by 15 times. The MFL detection, deformation detection and positioning detection are integrated into the same detector, so that all kinds of defects can be detected at one time. Meanwhile, the corrosion, deformation and girth weld defects can be aligned. Moreover, the intelligent identification and analysis software based on deep learning was developed and a BP neural network based deep learning model was established, realizing the integrated identification of defects and improving the detectability of pinhole corrosion. Hence, the defects with an area less than 1 t×1 t (where t is the wall thickness of the pipeline) can be identified effectively. In this way, the prominent problem that the pinhole corrosion and girth weld defects cannot be accurately described and quantified with the current three-axis high-definition magnetic flux leakage internal detector is solved preliminarily, which is of great significance for breaking the foreign monopolies and improving the technical level of pipeline integrity in China.

Oil and gas pipelines are one of the main means for oil and gas transportation over the world, and the development trend of their planning and construction is mainly affected by the development of oil and gas resources, as well as the national and regional energy policies. By quantitative and qualitative information mining, the global energy consumption structure and pipeline construction development in 2020 were sorted out, the current operation status of global oil and gas pipelines was analyzed, and the construction and development trend of global oil and gas pipelines in major regions of the world under the new situation was predicted. In the future, the construction of global oil and gas pipelines will be mainly affected by three factors: economy, politics and environment. It is predicted that the overall construction of global oil and gas pipelines will tend to be stable in recent years. Affected by the international environment, the construction progress of transnational pipelines is uncertain to a large extent, and fewer transnational pipelines can be completed and put into service on schedule. Besides, the pipeline construction in each country mainly depends on the economic development situation thereof. However, due to the dual impact of the economic downturn under the global COVID-19 pandemic and the energy transition under the guidance of "carbon peaking and carbon neutrality", it is expected that the local pipeline construction in the world will be concentrated in Asia-Pacific Region in the future. Meanwhile, the European and American countries and regions will explore to construct new hydrogen-mixed natural gas transportation pipelines or reconstruct existing gas pipelines for hydrogen-mixed natural gas transportation.(5 Figures, 3 Tables, 31 References)

The crack-like defects of oil and gas pipelines, especially the crack-like defects on the inner surface, are the main factors leading to pipeline failure. However, due to the limitation of the existing inline inspection technology, the cracklike defects are difficult to detect through inline inspection. Herein, various eddy current inline inspection tests of crack-like defects were performed by setting up an eddy current high-speed automatic testing device to detect the crack-like defects in the pipe body and girth weld at different defect depths based on the electromagnetic eddy current technology. In addition, the eddy current signal characteristics of crack-like defects were analyzed, and the feasibility of applying electromagnetic eddy current technology to the inline inspection of crack-like defects was verified. The test results show that the crack-like defects of oil and gas pipelines at different locations can be distinguished by the impedance signal of defects at a higher inspection speed. Meanwhile, the signal characteristics become more obvious with the increase of defect depth, but attenuate with the increasing of the liftoff value of defects. In addition, the greater signal-to-noise ratio of defect signal can satisfy the requirements for accurately identifying the crack-like defects.

In order to solve the problem of girth weld failure of high-grade pipelines and improve the safety of oil and gas pipelines in China, the influencing factors of girth weld failure of pipelines were systematically analyzed. It was found that the girth weld failure of pipelines was resulted from the combined action of the additional loads, defects, performance degradation and strain concentration. Meanwhile, the strain concentration in girth welds was mainly led to by the unequal wall thickness, including the misalignment caused by the geometric dimension of steel pipelines, and the low strength matching due to the welds or softening of the heat affected zones. In order to improve the bearing capacity of girth welds and reduce their strain concentration, a new type of pipe design idea was put forward, with the high dimension accuracy, out-of-roundness and circumference difference at the end of the pipes, as well as the misalignment of girth welds and the joint clearance during butting, close to zero, solving the current problems of misalignment and unequal thickness caused by the geometric dimensions at the end. In addition, by increasing the end thickness of pipes and using the principle of structural reinforcement, the stress bearing capacity of girth welding joints can be greatly improved, and thus the problem of low strength matching caused by the girth welds or softening of the heat affected zone could be solved, so that no or little plastic deformation occurs at the girth welding joints and the safety of the girth welds of pipes is improved significantly.

As more long-distance oil and gas pipelines with high pressure, large diameter, high steel grade and large wall thickness are constructed, the wall of the fittings such as the hot tapping tees and the repair sleeves that are involved in the in-service welding is thickened increasingly. Thereby, the pipeline maintenance and repair by manual arc welding is at low efficiency, and the welding quality is difficult to be guaranteed. Hence, it is urgent to realize the mechanical construction of in-service welding of oil and gas pipelines. In terms of the selection of welding process, welding test process, the selection of welding materials, the influence of protective gas, as well as the welding procedure qualification test, research was conducted for the automatic welding of oil and gas pipelines. Through the field engineering application of in-service automatic welding of type-B sleeves for the high-grade large-diameter gas pipelines in China, the feasibility of in-service automatic welding process was demonstrated. Finally, some suggestions were put forward for the promotion of in-service automatic welding technology.

The number of samples for detecting corrosion characteristic value is difficult to reach a large enough size in practical engineering, which leads to the pipeline corrosion evaluation results tend to be aggressive. For this reason, the influence of sample size on the inference results was analyzed, and based on the Bayesian theory and the uncertainty of measurement, the Bayesian inference method for the pipeline corrosion depth under the condition of small sample size was proposed. Then, the correlation between the corrosion depth and the length was considered, and the prediction method of corrosion depth based on the correlation and Bayesian inference was developed. Thereby, the corrosion depths under different defect lengths was inferred with the pipeline corrosion detection data, and further the effectiveness of the method was verified. The results indicate that: the new method could better reflect the influence of sample size on the inference results, the prediction results are more conservative and consistent with the engineering experience, and so it is safer and more favorable to the engineering application. The research results could provide more accurate information to the prediction of pipeline corrosion depth, as well as theoretical reference to the prediction of the characteristic value of other corroded pipelines with consideration given to the correlation of random variables.

The existing detection methods for third-party damage of the oil and gas pipelines are low efficient and easy to be disturbed by the external conditions such as the environmental magnetic field, which brings about a high false alarm rate. In order to improve the detection rate, a damage signal detection method for oil and gas pipelines based on the distributed optical fiber sensing technology was proposed. For the method, the short-time energy and the corrected zero crossing rate of each frame of signal in the detection period should be calculated at first, then the short-time average energy and the standard deviation of the corrected crossing rate of all frames of signal should be computed, and finally, the two should be combined together to determine if there is any damage signal, which could detect the pipeline damage signal effectively, further significantly reducing the false alarm rate of the pipeline detection system. By simulating various artificial and mechanical damage signals respectively, the feasibility and effectiveness of the new combined detection method were verified. The results show that the method of detecting the pipeline damage signals in combination with the short-time average energy and the corrected zero crossing rate can eliminate the interference, of which the detection accuracy for simulated artificial and mechanical intrusion events is more than 90%, capable of providing technical guarantee to the safe operation of pipelines.

By summarizing and analyzing the types and characteristics of the landslide hazards to the oil and gas pipelines, the emergency treatment methods were developed, the key points and difficulties of the emergency landslide treatment of oil and gas pipelines were summarized, and it was also pointed out that constructing anti-slide piles was the most commonly method used in the emergency landslide treatment of pipelines in southwest mountainous areas. In order to cope with the difficulty of constructing hand digging piles as the anti-slide piles for emergency landslide treatment of the oil and gas pipelines, such as the excavation of boulders, blocks and bedrocks in the soil-rock mixed landslides, the miniaturized machinery based construction technology of circumferential rock cutting with water mill drill and centered rock drill-splitting was proposed, then the principle of water mill drill based excavation technology and the construction plan were clarified, and finally the engineering application for landslide treatment of Xishui Section of Zhongwei-Guiyang Gas Pipeline was introduced. As indicated in the engineering practice, the new technology has improved the construction efficiency greatly and shows higher social and economic benefits compared with the conventional excavation method with air pick. In addition, it was pointed out that a more efficient rock splitting method without affecting the stability of landslide mass should be developed urgently.

In order to enhance the safety management of high consequence areas (HCAs) of oil and gas pipelines and effectively control the safety risk of personnel intensive HCAs, an investigation was performed for the causes of HCAs, the typical accident cases and the influence scope of consequence in personnel intensive HCAs were analyzed, and comparison was made to the identification criteria of HCAs at home and abroad. According to the statistics of the current situation of the personnel intensive HCAs of the existing and new pipelines in China, there are 1 523 and 517 personnel intensive HCAs for every 1×104 km existing oil and gas pipelines, respectively, and the pipeline section in the personnel intensive HCAs accounts for about 18% of the total length of the new oil and gas pipelines. In this study, the two main reasons for the continuous formation of the HCAS were analyzed, including lack of optimization for new pipeline routing and effective control of land using around the existing pipeline, and the whole process management system of the HCAs was put forward, including prevention before planning, assessment during planning and control after formation. Further, suggestions were proposed from the aspects of formulating the land division method and control requirements around the oil and gas pipelines, defining the safe distance of oil and gas pipelines and promoting the construction of urban pipeline corridor.

Oil and gas (O&G) pipelines are critical energy infrastructure, and their safety receives many concerns. The rapid development of structural health monitoring (SHM) technologies provides a new entry point for loss prevention of O&G pipelines. The present study conducted a systematic review of the research on SHM of O&G pipelines to capture the state-of-the-art technologies, applications, and future directions. The results indicate that research on SHM for O&G pipelines is booming, and the field has diversified. Existing publications have examined SHM from the perspectives of tool research and development (R&D), data processing, analysis algorithms, and failure diagnosis. Over time, SHM of O&G pipelines has evolved into a transdisciplinary research field, covering many emerging areas beyond engineering and instruments instrumentation, optics, computer sciences, physics, materials science, and energy fuels. In terms of application, scores of models and methods have been developed using advanced technology to model and predict pipeline risk and failure using SHM data. Relevant SHM of O&G pipeline topics can be divided into four research clusters: (i) damage identification, (ii) leak detection, (iii) machine learning, and (iv) data preprocessing. This study determines the knowledge gaps in SHM of O&G pipeline research. Future needs were provided, such as data coupling, coordination of different monitoring categories, and sensor location optimization. Advanced SHM equipment should be developed for O&G pipelines under potential extreme disasters. It is possible to increase the evaluation of the value of SHM information to optimize decision-making. Improving the efficiency of real-time condition monitoring extends the application of SHM data. • Research related to structural health monitoring of oil and gas pipelines was reviewed. • Main topics and research methods in the research domain were captured. • Future opportunities in this area were given. [ABSTRACT FROM AUTHOR]

• Investigate burst capacity of pipelines containing pinhole-in-corrosion defects using parametric FEA. • Burst capacity of PIC defect is insensitive to the pinhole diameter but largely affected by the pinhole depth and location. • Bulging effect identified as the underlying mechanism for the pinhole location effect on the burst capacity. This study carries out extensive parametric three-dimensional elasto-plastic finite element analysis to evaluate the burst capacity of oil and gas pipelines containing pinhole-in-corrosion (PIC) defects. The analysis results reveal that the burst capacity of the PIC defect is insensitive to the pinhole diameter but largely affected by the depth of the pinhole and length of the general corrosion. A pinhole located at the centre of the general corrosion is found to have a larger impact on the burst capacity than the same pinhole located near the edge of the general corrosion. The observed size and location effects on the burst capacity are attributed to the bulging deformation of a corroded pipeline under internal pressure. The findings of this study provide the basis for developing a practical, accurate engineering burst capacity model for PIC defects. [ABSTRACT FROM AUTHOR]