[Objective]Oil and gas storage and transportation equipment operates under harsh conditions with multi-factor coupling,making it susceptible to structural failure from mechanical impact and chemical corrosion.Traditional protective coatings struggle to balance strength and toughness,lack sufficient corrosion resistance,and fail to provide flame retardancy,falling short of the industry's composite protection requirements.Developing an integrated protective coating with high impact toughness,superior corrosion resistance,and advanced flame retardancy is therefore of significant engineering value.Such advancements are critical to ensuring the long-term integrity of storage and transportation equipment,reducing safety incidents,and extending equipment service life.[Methods]A novel multifunctional coating with high impact toughness,excellent corrosion resistance,and Bl-grade inherent flame retardancy was developed using a multi-scale design strategy.This coating can be applied to pipelines,ground storage tanks,mobile equipment fuel tanks,and other components to provide structural reinforcement and corrosion protection.By synergistically designing rigid and flexible molecular segments and optimizing the formulation,a favorable balance was achieved between high tensile strength(＞31.0 MPa)and high elongation at break(＞390％).[Results]A solid-liquid composite flame-retardant system was developed,providing B1-grade flame retardancy without significantly compromising mechanical properties,while the retention rate of core mechanical properties remained above 85％.The addition of 0.5wt％graphene oxide(GO)created a dense physical barrier.After 30 days of immersion in 10wt％H2SO4,10wt％HCl,20wt％NaOH,and 10wt％NaCl solutions,the coating's strength retention rates exceeded 85％,surpassing the 80％standard set by the Determination of Water Absorption of Paint Film(HG/T 3344-2012).Dynamic mechanical analysis using the Split Hopkinson Pressure Bar(SHPB)and full-scale fuel tank impact test demonstrated excellent energy absorption and structural integrity retention under high strain-rate loading.[Conclusion]Molecular structure optimization,solid-liquid composite flame-retardant system construction,and GO nano-reinforcement were integrated to develop a multifunctional coating combining high impact resistance,excellent corrosion protection,and Bl-grade flame retardancy.All performance metrics meet the stringent requirements for oil storage and transportation equipment,providing an effective solution for protecting such assets under harsh conditions.(5 Figures,3 Tables,24 References)
[Objective]Extreme events such as natural disasters,geopolitical conflicts,and cyberattacks pose significant threats to the safe operation of China's oil and gas pipelines.To systematically identify core risks,understand their mechanisms,and develop effective prevention strategies,targeted research is urgently needed to enhance the resilience and reliability of national pipelines under extreme conditions.[Methods]Typical cases of extreme events involving oil and gas pipelines,both at home and abroad,were systematically compiled through literature review and case analysis.The inducement mechanisms,failure modes,emergency responses,and post-disaster support mechanisms of these events were thoroughly analyzed,and the action characteristics and evolution patterns of various extreme events were revealed.[Results]Five core extreme risk factors threatening the safety of oil and gas pipeline systems were identified and refined:extreme natural disasters,terrorist attacks,local wars,electrical fire sources,and cyberattacks.Their typical manifestations and damage mechanisms were systematically analyzed.Based on this,five practical prevention strategies were proposed:enhancing monitoring and early warning,strengthening physical emergency response,ensuring strategic backups,rigorously enforcing technical controls,and establishing a comprehensive defense system.[Conclusion]The research has identified the primary risk factors associated with extreme oil and gas events and proposed specific implementation paths for prevention and control measures.These findings provide theoretical support and technical guidance for the safety design and operational management of China's oil and gas pipelines under complex and evolving extreme risks.They also serve as a foundation for improving the national energy infrastructure safety system,formulating targeted pipeline protection policies,and developing emergency preparedness strategies.This research offers both theoretical reference and practical guidance for enhancing the risk resilience and reliable operation of China's oil and gas pipeline systems under extreme scenarios.(2 Figures,7 Tables,56 References)
[Objective]Elbows,as geometrically discontinuous structures in buried oil and gas pipelines,are susceptible to failures such as fatigue damage,local buckling,and stress-corrosion cracking due to stress concentration.Accurate identification of their location and geometric features is crucial for pipeline integrity assessment and safe operation.However,current in-line inspection technologies face significant challenges in reliably identifying elbows,determining their types,and characterizing their spatial geometry.Therefore,developing a high-precision elbow identification method based on multi-source data fusion is imperative.[Methods]A method for elbow identification and spatial feature analysis was developed based on data from the Inertial Measurement Unit(IMU)and odometer.Continuous pipeline attitude information was obtained from IMU and odometer data collected by the in-line inspection tool,then filtered and resampled using mileage constraints.Changes in attitude angles between consecutive sampling points were combined with pipeline segment geometric parameters to eliminate interference from girth welds,enabling identification of hot-bent and cold-bent elbows.Finally,the local three-dimensional spatial trajectory of the elbow region was reconstructed from attitude angle and mileage data to characterize its geometric features.[Results]The proposed method was applied to a 4,400 m small-diameter gathering pipeline.Comparison with traditional magnetic flux leakage(MFL)inspection revealed that the new method identified 151 elbows(117 hot-bent and 34 cold-bent),whereas the traditional MFL inspection identified 137 elbows.Of these,128 elbows were matched between the two methods,achieving a 93.43％coincidence rate based on MFL inspection results.While maintaining high consistency,the new method also provided elbow type identification,which the traditional MFL inspection could not achieve.Additionally,the three-dimensional spatial trajectories of 23 newly identified elbows were reconstructed,showing continuous bending characteristics consistent with typical elbow geometry.In contrast,all elbows identified solely by traditional MFL inspection were located in girth weld areas and lacked continuous bending characteristics,demonstrating that three-dimensional trajectory analysis effectively eliminated girth weld interference and accurately determined elbow types.[Conclusion]The IMU-based elbow identification method offers clear advantages in detection accuracy and geometric characterization.It supports defect localization,quantitative evaluation of long-distance pipelines,trenchless inspections,and the development of operation,maintenance,and repair plans.(8 Figures,2 Tables,27 References)
[Objective]Amid the global energy transition and the accelerating pursuit of"dual carbon"goals,large-scale storage and transportation of hydrogen-a clean and efficient energy carrier-have become key bottlenecks for industrial development.Repurposing existing natural gas pipelines for hydrogen transport is an effective way to reduce infrastructure costs and shorten construction timelines.[Methods]The program"Flow-Making Hydrogen Happen"("Flow Program")of Gascade in Germany was selected as the research subject.The overview,key technological breakthroughs,and standard application practices of the Flow Program were systematically reviewed.Critical technical aspects were analyzed in detail,including material adaptability evaluation,compressor and drive system retrofitting,welded joint performance verification,valve sealing optimization,and metering system upgrading.Differences between Chinese and German X70 pipeline systems in materials,equipment,welding,sealing,and metering were compared,and core divergences in standard systems,retrofitting criteria,material compatibility assessment logic,and pressure classification management were identified.[Results]The study found that Germany achieved safe and efficient repurposing of large-diameter,high-pressure natural gas pipelines for hydrogen transport through systematic material verification,scientific retrofitting strategies,and comprehensive mature standards.Its technical experience and standard application model proved highly instructive.Despite a substantial pipeline network and resource base for repurposing natural gas pipelines for hydrogen transport,China remains in the early stages of developing long-distance hydrogen pipeline standards,compatibility assessments for high-grade steel pipes,and technical specifications for key equipment retrofitting.[Conclusion]Considering China's national conditions and the strategic plan of"West-East Hydrogen Pipeline",this study proposes targeted strategies for material R&D,retrofit planning,equipment upgrades,standard development,and international cooperation.The findings aim to provide technical guidance for repurposing natural gas pipelines for hydrogen transport,support the development of national hydrogen storage and transportation infrastructure,and promote the high-quality growth of China's hydrogen energy industry.(7 Tables,27 References)
[Objective]In the context of China's"dual carbon"strategic goals,natural gas plays a crucial bridging role.Due to its high degree of marketization and flexible operation,LNG effectively balances natural gas supply and demand.LNG terminals serve as key hubs in the global LNG supply chain.With steady industry growth,China has established 33 LNG terminals,boasting an annual receiving capacity of 1.604× 108 t/a.As the LNG terminal sector continues to expand,innovative development is essential to meet evolving demands under the new strategic landscape.[Methods]Through a literature review,the development trends of China's LNG industry,industry data on LNG terminals,and relevant national regulations and policies issued in recent years were systematically sorted out.The risks and challenges facing the LNG terminal industry were analyzed,and an"industry background-development status-risks and challenges-response strategies"analytical framework was constructed to propose future development pathways for LNG terminals.[Results]Operators of LNG terminals in China include central and local state-owned enterprises as well as private companies,reflecting a diversified development trend.Fair access for third parties has been largely achieved,service products centered on LNG terminal window periods have been established,and initial marketization has been realized.Currently,China's LNG terminals face three major challenges:increasing external environmental uncertainty,industry overcapacity due to concentrated commissioning,and limited diversity of service offerings.[Conclusion]To promote a more efficient,fair,and open industry,the following strategies are recommended for LNG terminals:(1)actively expand emerging high-growth businesses such as gas storage,LNG fueling for vehicles and ships,and bonded transfer;(2)develop a multi-energy coupling system integrating hydrogen,carbon dioxide,green electricity,and cold energy,incorporating LNG terminals into a new mass-energy network;(3)establish unified market products and trading rules to create a national LNG terminal market;(4)decompose the terminal's window period service into a combination of three product pricing options-berthing rights,storage capacity,and export capacity-and refine service product categorization;(5)build digital platforms,including websites and mobile apps,to enable dynamic sharing of LNG terminal service information.(1 Figure,2 Tables,17 References)
[Objective]Using pipelines to transport gaseous CO2 offers an economical solution for short-distance CO2 transport in Carbon Capture,Utilization and Storage(CCUS)projects.However,CO2 pipelines are susceptible to stress corrosion cracking(SCC)under severe internal corrosion and external stress,raising concerns about their service reliability.[Methods]The research status of SCC in CO2 pipelines across different phases was comprehensively reviewed.Corrosion behavior,crack initiation,and propagation mechanisms were explored with a focus on the gaseous CO2 transportation environment.The synergistic process of anodic dissolution-film rupture and hydrogen-induced cracking in this environment was elaborated.Subsequently,the multi-factor coupling effects of material properties,environmental conditions,and stress states on the SCC susceptibility of pipeline steel were systematically analyzed,and existing research deficiencies were summarized.[Results]The relatively low pressure of gaseous CO2 causes localized condensation of the aqueous phase on the pipe wall as micro-droplets,forming a discontinuous,porous FeCO3 corrosion product film that offers limited protection.In the microstructure,fine acicular ferrite promotes passive film nucleation due to its high dislocation density.Non-metallic inclusions facilitate crack nucleation by inducing interfacial stress concentration,acting as hydrogen traps,and initiating micro-galvanic corrosion.Impurity gases in gaseous CO2 increase SCC susceptibility by altering aqueous phase precipitation,participating in cathodic reactions,and destabilizing the corrosion product film.Moisture,with its condensation behavior regulated by temperature and pressure,is a key factor in inducing local and top-of-the-line corrosion.[Conclusion]Research on the SCC mechanism of gaseous CO2 pipelines remains limited.To ensure the safe and stable operation of CO2 transportation pipelines,future studies should focus on:clarifying the effects of flow velocity,shear force,and phase changes on the formation and growth of local corrosion pits in gaseous CO2 environments;monitoring and analyzing in-situ electrochemical corrosion data in gaseous CO2 with trace water under external stress;and expediting the development of an SCC evaluation system for in-service oil and gas pipelines repurposed for gaseous CO2 transport.(2 Figures,96 References)
[Objective]Amid the global energy transition and intensifying major-power competition,securing liquefied natural gas(LNG)imports has become vital to China's strategy for building an"Energy Powerhouse".Traditional research often treats geopolitical risk as a broad context,lacking quantitative tools to analyze its structural impacts and country-specific variations within the global energy supply chain.To accurately characterize the full spectrum of geopolitical risks facing China's LNG imports,there is an urgent need to develop a spatially disaggregated analysis framework.[Methods]From the integrated perspectives of energy geography and geopolitics,a multi-level evaluation system was established,covering four risk dimensions:source country,transportation corridor,key chokepoints,and infrastructure.Using multi-source heterogeneous data-including United Nations(UN)trade statistics,automatic identification system(AIS)shipping trajectories,and geopolitical risk indices—quantitative measurements of China's LNG import geopolitical risks were conducted annually from 2020 to 2024.[Results]Significant variations in comprehensive risks were identified.Nigeria and Qatar were classified as high-risk countries;six others,including Russia and the United States,as medium-risk;and Australia and Brunei as low-risk.Risk profiles demonstrated clear country-level heterogeneity.The United States showed pronounced source country risk,Nigeria had the highest transportation corridor risk,while both Qatar and Nigeria faced elevated key chokepoint risks.Infrastructure vulnerabilities were widespread in many countries.Dominant risk drivers varied by country,including policy uncertainty in the United States,route fragility in Nigeria,and single-corridor dependence in Qatar.[Conclusion]The multi-dimensional characteristics and country-level heterogeneity of geopolitical risks in China's LNG imports highlight the need to shift energy security governance from broad narratives to targeted,spatially disaggregated strategies.Implementing tailored approaches based on the dominant risk type of each source country is crucial for enhancing supply resilience.This study offers an analytical tool for quantifying energy geopolitical risks,while future research should integrate dynamic early-warning models to strengthen real-time risk monitoring.(4 Figures,2 Tables,42 References)
[Objective]The transition to a decarbonized energy structure and the integration of high proportions of renewable energy have amplified the peak-valley differences in power systems,increasing the demand for flexible regulation.Meanwhile,significant pressure energy is lost through throttling during pressure regulation at urban natural gas gate stations.In addition,the power and natural gas systems have traditionally operated independently,lacking effective technologies to integrate their flexible resources for coordinated peak shaving.[Methods]To address the aforementioned issues,a novel liquefied natural gas(LNG)energy storage system was proposed,integrating compression driven by off-peak electricity with direct expansion refrigeration of high-pressure pipeline gas.The system was innovatively designed to achieve the spatio-temporal coupling and conversion of surplus electricity from the power grid and excess pressure energy from the gas pipeline network.In the energy storage stage,off-peak electricity was used to drive compressors to pressurize and precool natural gas from the pipeline network.The high-pressure natural gas was then adiabatically expanded in a turbine expander to generate cryogenic cooling,enabling the cooperative conversion of electrical energy and pressure energy into LNG for storage.In the energy release stage,the stored LNG was rapidly gasified to supply the gas pipeline network or expanded through turbines coupled with generators to produce electricity.Thermodynamic and exergy analysis models of the system were established.Based on a typical daily peak-shaving scenario of"8-hour energy storage-8-hour energy release",multi-objective optimization was conducted for key operating parameters,with system round-trip efficiency and liquefaction rate as the optimization objectives.Thermodynamic performance analysis and techno-economic evaluation were subsequently carried out for the optimized system.[Results]Under optimal conditions,the system achieved a liquefaction rate of 78.49％,a round-trip efficiency of 322.8％,and an energy storage density of 10.08 kWh/m3-significantly surpassing conventional compressed air and battery energy storage systems.Economic analysis indicated that for a plant with a daily peak-shaving gas capacity of 17.9× 104 m3,the equivalent charging and discharging powers were 412 kW and 1,329 kW,respectively,with a levelized cost of storage(LCOS)as low as USD 0.0244/(kW·h).[Conclusion]The system enables coordinated power-gas peak shaving through multi-energy flow coupling,significantly enhancing the integrated energy system's flexibility and facilitating renewable energy consumption.However,its operation depends on synchronized peak-shaving cycles between the power and gas grids.Future improvements in adaptability and robustness could be achieved by incorporating buffer energy storage or external regulation mechanisms.(4 Figures,11 Tables,33 References)
[Objective]Buried pipelines are subjected to complex soil conditions,with corrosion processes characterized by pronounced nonlinearity and dynamic temporal variation.This study introduces a high-precision hybrid prediction model,leveraging a segmentation mechanism for dynamic and accurate corrosion rate prediction.[Methods]A segmented dynamic prediction model,RF-IGOA-ITransformer,was developed by integrating Random Forest(RF),an Improved Goat Optimization Algorithm(IGOA),and an improved Transformer(ITransformer).Initially,the original multi-dimensional environmental features were ranked and screened using the RF algorithm to eliminate redundant variables and construct a high-quality input feature set.Then,considering the non-stationarity of corrosion rate fluctuations,an adaptive segmentation mechanism based on a global standard deviation threshold was introduced to automatically divide the corrosion process into slowly-varying and abrupt-change segments.The core prediction module employed the ITransformer,which separately modeled the evolutionary characteristics of different stages through adaptive segmentation coding and a multi-scale attention mechanism.To address the challenge of determining the segmentation threshold,the IGOA was applied to globally optimize the model's key parameters via its dual-population cooperative search mechanism,ensuring adaptive capacity across various corrosion scenarios.[Results]The RF-IGOA-ITransformer model was evaluated using 100 datasets representing typical corrosion environments,demonstrating excellent overall performance.For the test sets,the model achieved a Mean Absolute Error(MAE)of 0.012,a Mean Squared Error(MSE)of 0.0003,a Root Mean Squared Error(RMSE)of 0.0169,a Mean Absolute Percentage Error(MAPE)of 17.13％,and a coefficient of determination(R2)of 0.8211.Compared to the baseline Transformer model,the proposed model's R2 increased by 90.16％,while the MAE and MSE decreased by 41.18％and 66.67％,respectively.When compared to the unoptimized ITransformer model,the R2 improved by 62.52％,with reductions in MAE and MSE of 38.14％and 62.50％,respectively.The model effectively captured low-speed fluctuations in slowly-varying segments and significantly enhanced the detection of rate jumps and key inflection points in abrupt-change segments.[Conclusion]The RF-IGOA-ITransformer model significantly enhances prediction accuracy and robustness for buried pipeline corrosion rates,supporting effective safety management.(3 Figures,5 Tables,31 References)
[Objective]Natural gas pipeline failures pose significant risks to energy transportation,public safety,and the environment.However,there remains a lack of comprehensive understanding of the failure mechanisms and patterns affecting these pipelines.By analyzing cross-national data differences,elucidating cause-effect relationships,and examining the spatio-temporal evolution of pipeline failures,as well as assessing the impact of multi-factor interactions on pipeline integrity,this research aims to provide theoretical and technical support for optimizing pipeline safety management systems.[Methods]Using pipeline accident data from the US Pipeline and Hazardous Materials Safety Administration(PHMSA),the European Gas Pipeline Incident Data Group(EGIG),the Canada Energy Regulator(CER),and China,a standardized classification system with six categories-including corrosion,material defects,and third-party damage—was applied for multidimensional analysis.The classification methods and influencing factors of natural gas pipeline failures were systematically reviewed.Statistical analysis,case studies,and other approaches were employed to thoroughly investigate the interactions among various factors and their impact mechanisms on pipeline failures.[Results]The causes of natural gas pipeline failures vary across countries and regions,primarily involving materials and equipment,corrosion,and third-party damage.The United States and Canada share similar accident profiles,dominated by material,welding,and equipment failures.Europe experiences more third-party damage,while gas theft by puncturing pipelines is notably prevalent in China.Corrosion remains a common risk worldwide.Although technological advances and strengthened management have significantly reduced accident rates,pipeline aging remains a persistent challenge.Natural gas pipeline failures result from the combined effects of technology,management,and environmental factors.Their development follows distinct spatio-temporal patterns,generally conforming to a"bathtub curve"over time and being significantly influenced spatially by geography,pipeline design parameters,and social activities.[Conclusion]Effective prevention and control of natural gas pipeline failures require a comprehensive approach that considers multiple factors and their coupling.Implementing targeted,integrated,and multi-level safety management strategies is essential to enhance pipeline safety and support the sustainable development of the natural gas industry.(5 Figures,4 Tables,59 References)
[Objective]Supercritical/dense-phase CO2 exhibits relatively high density.During pipeline transport,planned or accidental valve closures can induce transient water hammer.Current research on CO2 pipeline water hammer primarily relies on simulations,with limited experimental investigation into its governing dynamics.[Methods]A 238 m-long experimental setup for transient water hammer in a supercritical/dense-phase CO2 pipeline(56 mm diameter,20 MPa design pressure)was designed and constructed.Fifteen groups of experiments were conducted at varying initial temperature,pressure,CO2 flow velocity,and valve closing time.Multiple pressure sensors positioned along the pipeline loop captured pressure fluctuations,enabling detailed analysis of water hammer behavior in supercritical/dense-phase CO2 pipelines.[Results]At a constant initial temperature,increasing the initial pressure raised CO2 density and fluid kinetic energy per unit volume.When converted to pressure energy,this intensified the water hammer effect,increasing pressure and shortening the cycle.At a constant initial pressure,higher initial temperature reduced CO2 density,viscosity,sound velocity,and compressibility,thereby weakening water hammer pressure and extending the cycle.Shorter valve closing time increased water hammer pressure,while prolonging closure significantly reduced peak pressure-under 9 MPa and 20℃,a 1-second delay lowered pressure by about 30％.Increasing CO2 flow velocity raised system kinetic energy,and under supercritical/dense-phase CO2 conditions,rapid valve closure released this energy more intensely,amplifying water hammer intensity.However,flow velocity and valve closing time did not affect the water hammer cycle which was mainly governed by initial temperature and pressure.[Conclusion]When designing and operating pipeline systems,the risk of water hammer overpressure must be addressed.Reducing operating pressure and increasing temperature can mitigate transient pressure shocks caused by water hammer.Additionally,rapid valve operations under high flow velocity should be avoided.This study experimentally characterizes valve-closing water hammer behavior in supercritical/dense-phase CO2 pipelines,providing a critical foundation for developing water hammer models for supercritical CO2 pipelines and guiding CO2 pipeline design and protection.(5 Figures,6 Tables,22 References)
[Objective]Existing intelligent diagnosis methods predominantly rely on purely data-driven models,which are inherently"black-box"and often lack generalization due to the absence of physical information when handling the variable-length,non-stationary vibration signals of natural gas compressors.Therefore,developing a hybrid fault diagnosis model that offers high accuracy,robustness,and interpretability is essential for the safe and intelligent operation and maintenance of compressors.[Methods]A Dual-Path Hybrid Diagnostic(DPHD)model for compressor faults was proposed.In the data-driven path,the Multi-Scale Temporal Residual Block(MTRB)served as the core,capturing dynamic signal characteristics across multiple time scales using parallel convolution kernels of varying sizes.A length-adaptive pooling layer then unified variable-length feature sequences into fixed-length vectors,effectively addressing variable-length signal processing.Concurrently,the physical prior path employed a Multilayer Perceptron(MLP)to perform deep nonlinear extraction of nine-dimensional physical statistical features,such as kurtosis and spectral entropy,thereby incorporating domain knowledge.Finally,the heterogeneous feature vectors from both paths were concatenated and fused before being input to a fully connected classifier for collaborative fault diagnosis.[Results]The proposed DPHD model was validated on an industrial compressor dataset encompassing 10 operating conditions.Results demonstrated an overall diagnostic accuracy of 99.60％,significantly outperforming baseline models such as 1D Convolutional Neural Network(1D CNN)and Support Vector Machine(SVM).The t-Distributed Stochastic Neighbor Embedding(t-SNE)algorithm was employed to reduce dimensionality and visualize the high-dimensional features,confirming that the fused features learned by the DPHD model exhibited superior intra-class compactness and inter-class separability.Additionally,ablation studies confirmed the necessity and effectiveness of the dual-path architecture,multi-scale design,and integration of physical prior knowledge.[Conclusion]The proposed DPHD model addresses challenges in variable-length signal processing and interpretability by integrating multi-scale deep features driven by data and physical prior knowledge.It delivers high-precision compressor fault diagnosis and offers a hybrid paradigm combining strong performance with physical insight for intelligent operation and maintenance of complex industrial equipment.(5 Figures,3 Tables,35 References)
[Objective]Against the strategic backdrop of China's efforts to build a modern,high-quality comprehensive three-dimensional transportation network and a new energy system,the pipeline transportation system-core to efficient cross-regional transport of energy and strategic materials-is undergoing a critical transformation from a traditional single-medium facility to a hub infrastructure featuring intelligent multi-network integration of"pipeline-transportation-energy".[Methods]A combination of policy document analysis,literature review,and case investigations was employed.The core concepts and driving factors of intelligent multi-network integration were thoroughly analyzed,and the pipeline transportation system's central role in three strategic goals-constructing a comprehensive three-dimensional transportation network,advancing the energy Internet,and enhancing national energy security and resilience-was systematically explained.[Results]Although national top-level plans for multi-network integration have been issued and initial progress achieved in some hub and intermodal scenarios,current efforts largely remain limited to physical connections or superficial coordination between networks.Deep intelligent integration-characterized by data interconnection,functional complementarity,and mutual benefits-has yet to be realized.Therefore,it is further emphasized that the primary task now is to translate the strategic vision into actionable,operational,and binding plans.The development requirements and core challenges for the comprehensive pipeline transportation system are identified across three dimensions:fundamental integrated element design,infrastructure digitalization support,and advanced intelligent transportation services.[Conclusion]To develop an intelligent,green,and resilient comprehensive pipeline transportation system and support the national comprehensive three-dimensional transportation network and new energy system,the following recommendations are proposed:(1)Strengthen collaborative planning by establishing a"multi-energy supply-demand and multi-transport capacity"mechanism to address mismatches between energy sources and loads,while balancing normal efficiency and emergency supply security.(2)Enhance transportation and dispatching efficiency by advancing multi-energy coupling simulation and optimization algorithms,enabling precise resource allocation through market mechanisms.(3)Improve system resilience by implementing a full life-cycle evaluation framework,developing an emergency response system combining"immediate response and proactive prevention",mitigating cross-system risk transmission,and ensuring a stable energy supply for both military and civilian needs.(1 Table,55 References)
[Objective]Centrifugal compressor units are critical power components of long-distance natural gas pipeline systems.Their faults not only disrupt the stability of gas transportation but also lead to high maintenance costs and pose safety risks.Therefore,timely and accurate detection of abnormal vibrations in these units is essential to prevent fault escalation and ensure safe,reliable operation.[Methods]A comprehensive alarm method for centrifugal compressor units based on interval,rapid change and overlimit alarm strategies was proposed.The vibration characteristics of electric-and gas-driven units were thoroughly analyzed,and two key parameters-full-frequency vibration value and speed-were selected.The confidence interval for real-time full-frequency vibration value was predicted using the mean and standard deviation of historical full-frequency vibration values and the speed's standard deviation.An alarm was triggered when the vibration values at two measurement points on the same unit simultaneously exceeded the confidence interval.To address sudden changes in the full-frequency vibration value at a single point caused by signal interference,loose wiring,or sensor failure,a rapid-change alarm strategy was introduced.To cover shutdown,start-stop,and normal operation states,an overlimit alarm strategy was developed to detect extreme full-frequency vibration values and signal interruptions.Alarm execution strategies for interval,rapid-change,and overlimit conditions were formulated according to the compressor's operating state,leveraging the strengths of each strategy to ensure low false-alarm and missed-alarm rates.[Results]By integrating the actual vibration patterns of centrifugal compressor units with the requirements of the interval,rapid change and overlimit alarm strategies,specific data for key parameters were established.The effectiveness of the proposed comprehensive alarm method was then validated using both normal and fault vibration cases.Results demonstrated that the method effectively eliminated the influence of electrical and mechanical jitter as well as speed adjustments.With straightforward,targeted parameter adjustments,it accurately identified abnormal phenomena-including sudden,abrupt,and gradual changes in full-frequency vibration-while maintaining a low false alarm rate.[Conclusion]The proposed method enables on-site and remote technicians to promptly detect abnormal vibrations in centrifugal compressor units,preventing fault escalation and damage.It supports the development of unmanned or minimally manned stations,black-screen management,and the intelligent operation of long-distance natural gas stations.(8 Figures,22 References)
[Objective]The rapid expansion of oil and gas pipeline construction in China,coupled with accelerating urbanization,has heightened safety concerns from stratum settlement,posing significant risks to buried pipeline operations.Stratum settlement is a time-dependent process;although similar settlement outcomes may arise from varying development patterns,current safety evaluations overlook how these differing settlement processes affect the mechanical response of buried pipelines.[Methods]Finite element numerical simulation was employed.By varying settlement counts and sequences across different areas,simulations of buried pipeline settlement under various modes were conducted and validated experimentally.The simulation results enabled a quantitative comparison and analysis of the mechanical responses of buried pipelines under different settlement modes.[Results]Under reverse-order,step-by-step settlement,the maximum surface settlement above the pipeline exceeded that of the one-time overall settlement mode.Although soil separation beneath the pipeline center was severe,the pipeline's mechanical response remained lower than in the one-time overall settlement.When settlement counts were equal,differences in pipeline mechanical response due to settlement sequence exceeded 50％,highlighting the significant impact of settlement processes.For the same settlement amount,the one-time overall mode caused more than twice the maximum displacement and longitudinal tensile strain compared to multi-step settlement.Consequently,one-time overall settlement induced a more intense mechanical response,increasing the risk of damage to buried steel pipelines.[Conclusion]Large-scale local stratum settlement has limited impact on the overall mechanical response of buried pipelines.A comprehensive analysis of the settlement development across the entire area is necessary.To minimize pipeline mechanical response for a given settlement range and amount,it is recommended to first analyze large-scale settlement in the center of the area,followed by multiple smaller settlements toward the boundaries.These findings are crucial for accurately assessing the safety of buried pipelines under stratum settlement.(25 Figures,7 Tables,23 References)
[Objective]To address the growing gap between China's rapidly increasing demand for natural gas peak-shaving and the limited effective working gas volume of underground gas storage facilities,this study reviews the development of depleted-reservoir-type gas storage in China,and systematically analyzes the key factors that constrain their service efficiency.The study aims to reveal the coupling mechanisms between complex geological conditions and high-frequency injection-production operations,providing a theoretical foundation for developing a generalizable technical system to expand capacity and achieve production ramp-up in depleted-reservoir-type gas storage facilities.[Methods]Based on construction and operation data from typical gas storage facilities in China,combined with laboratory experiments and engineering practices,a capacity expansion and production ramp-up system centered on"well pattern optimization,injection-production regulation,edge water displacement,and liquid drainage"was proposed.The coupling relationships among these four technical units were analyzed,establishing a technical pathway from geological understanding and well pattern design to injection-production operations and reservoir capacity reutilization.[Results]Depleted-reservoir-type gas storage facilities in China are generally constrained by complex geological conditions-such as tectonic fragmentation,deep burial and high pressure,strong reservoir heterogeneity,and extensive edge and bottom water—as well as by multi-cycle injection-production dynamics,including alternating stress damage,salt deposition near the wellbore,secondary water locking,and expansion of the gas-water transition zone.Consequently,the effective utilization rate of reservoir capacity is significantly below design levels,and single engineering measures are insufficient for sustained capacity expansion.By optimizing the injection-production well pattern and implementing differentiated injection-production strategies,reservoir control can be expanded and damage from stress and salt deposition mitigated.Combined with edge and bottom water displacement and liquid drainage measures,these approaches release pore space occupied by water and liquid hydrocarbons,control water invasion risk,improve gas-phase seepage conditions,and enhance both reservoir utilization efficiency and peak-shaving capability.[Conclusion]Establishing a coupling control system integrating well pattern,injection-production,water flooding,and liquid drainage is an effective solution for capacity expansion and production ramp-up in depleted-reservoir-type gas storage facilities under complex geological conditions.However,quantitative constraints on gas and water migration in micro-nano pores and the critical conditions for liquid drainage and capacity expansion remain insufficient.In the future,dynamic control technologies leveraging intelligent optimization algorithms and multi-field coupling models can be developed to shift capacity expansion and production ramp-up from experience-driven to model-guided approaches,providing theoretical support and technical guidance for the safe and efficient operation of gas storage facilities in China.(3 Figures,2 Tables,58 References)
[Objective]Amid the global energy transition and the"dual-carbon"goals,hydrogen energy,as a clean energy carrier,holds significant application potential.However,hydrogen leakage in pure hydrogen and hydrogen-blended natural gas pipeline transportation systems poses a high explosion risk.Therefore,it is imperative to advance comprehensive hydrogen elimination,explosion prevention,and explosion suppression technologies to ensure safe transportation.[Methods]Through literature research and review analysis,the scientific principles of hydrogen elimination,passive and active protection,and explosion suppression technologies were systematically summarized.The effectiveness,applicable scenarios,and limitations of these technologies were evaluated.The innovative model of multi-medium collaborative hydrogen elimination and explosion suppression was analyzed in detail,alongside a compilation of the latest domestic and international research findings and engineering cases.[Results]In terms of hydrogen elimination technologies,ventilation in open spaces was found to have limited effectiveness.While inerting provided effective explosion suppression,it involved high costs and safety risks.Catalytic hydrogen elimination demonstrated high efficiency but faced challenges with catalyst poisoning.A multi-stage collaborative hydrogen elimination system(such as ventilation combined with inerting and catalysis)significantly improved both safety and efficiency.For explosion-proof and pressure-relief technologies,active explosion-proof systems offered rapid response but required high equipment reliability,while passive systems needed structural optimization for hydrogen characteristics.Pressure-relief effectiveness was significantly influenced by relief outlet size and gas concentration,and secondary explosions needed to be prevented.Each single explosion suppression technology had limitations:inert gas suppression required high concentrations,liquid-phase suppression risked equipment corrosion,powder suppression was less effective in pure hydrogen,and porous material suppression faced issues with material selection and adaptability.Collaborative explosion suppression technologies significantly enhanced effectiveness through the synergistic action of multiple suppressants.[Conclusion]Current hydrogen elimination,explosion prevention,and explosion suppression technologies face challenges including high costs,limited material adaptability,and poor stability under complex conditions.Future efforts should focus on developing a collaborative model of efficient hydrogen elimination combined with multi-medium explosion suppression.This includes developing low-cost,anti-poisoning catalysts,intelligent control systems,and targeted hydrogen-absorbing materials,optimizing explosion suppression formulations,and establishing scenario-based safety standards to guide the safe operation of hydrogen pipeline transportation systems.(4 Tables,79 References)
[Objective]In the context of the"dual carbon"goals,energy conservation and carbon reduction are essential for national energy security and green transformation.As major energy consumers in oil and gas gathering,transportation,and processing,oilfield joint stations using the traditional"power grid+gas-fired boiler"supply model face significant challenges,including high costs,large emissions,and limited resilience.Therefore,it is urgent to develop a multi-energy complementary system capable of integrating a high share of renewables and providing robust seasonal regulation.[Methods]To address the issues of high energy consumption,emission,and resilience risks in oilfield joint stations,a collaborative"wind-solar-hydrogen-storage-load"multi-energy system architecture was proposed.Wind and solar generation replaced purchased electricity,while an"electricity-hydrogen-electricity"closed loop was established through electrolytic hydrogen production,hydrogen storage,and fuel cells.Multi-source heat supply was achieved via combined heat and power units,heat pumps,and heat storage.The system innovatively incorporated stepped carbon trading and dual demand response(price/incentive)into a unified optimization model,which was evaluated across economic,low-carbon,and resilience objectives.[Results]Based on mixed-integer linear programming(MILP),four scenarios were analyzed using a joint station in Daqing Oilfield as a case study.The findings were as follows:(1)Compared to the traditional supply mode,the multi-energy complementary system with hydrogen cycling increased energy utilization efficiency by over 30％,reduced annual operating costs by 41.20％,lowered carbon emission intensity by 2.10％,and renewable energy consumption exceeded 90％.(2)Leveraging stepped carbon trading,the system's carbon trading costs increased by 24.98％,carbon emissions dropped by 6.74％.(3)With superimposed demand response,carbon emissions decreased by an additional 1.30％,and carbon trading costs fell by 1.51％,achieving both emission and cost reductions.(4)The hydrogen subsystem acted as a spatio-temporal regulator,storing surplus green electricity during wind and solar generation and supplying power and heat during peak loads or extreme weather.The annual wind and solar curtailment rate was kept below 1％,significantly improving energy supply resilience.Economic analysis indicated that,at current carbon prices and electrolyzer investment levels,the payback period for incremental investment was 5-8 years;if the carbon price dropped below RMB 80/t and electrolyzer costs fell below RMB 2,500/kW,the payback period could be shortened to 4 years.[Conclusion]The research establishes a replicable low-carbon transformation pathway for energy supply in oilfield joint stations,supporting quality and efficiency improvements in existing stations with abundant associated gas and stable electric and thermal loads.It also provides an"electricity-heat-hydrogen"collaborative model for microgrid planning in new blocks with high renewable energy penetration.(6 Figures,3 Tables,32 References)
[Objective]Natural gas demand is influenced by intertwined factors such as economic fluctuations,policy regulations,and seasonal variations.Inadequate integration of dynamic policy effects with the long-and short-term dependencies in time-series data significantly hinders forecasting accuracy.Therefore,it is essential to develop a coupled forecasting model that incorporates policy time-series characteristics to enhance model adaptability to complex scenarios and improve prediction accuracy.[Methods]First,a combined approach of linear interpolation and historical monthly mean interpolation was used to address missing data in the feature sequence of influencing factors.Second,the BorutaShap algorithm was applied for feature importance screening and dimensionality reduction,eliminating redundant features and retaining core information to reduce model input dimensions.Third,a policy-related feature sequence was constructed,incorporating policy hierarchy,seasonal adjustments,time-decay effects,and synergistic or conflicting influences to quantitatively represent policy factors.Meanwhile,a policy gating mechanism was introduced to dynamically adjust feature weights,leveraging the Temporal Convolutional Network(TCN)for capturing long-range trends,Temporal 2D-Variation Modeling Network(TimesNet)for multi-scale periodic analysis,and Bidirectional Long Short-Term Memory(BiLSTM)for local time-series dependencies,thus achieving deep coupling of policy and time-series data.Finally,the Improved Black-winged Kite Algorithm(IBKA)was employed to optimize model hyperparameters,resulting in the integrated IBKA-TCN-TimesNet-BiLSTM natural gas demand forecasting model.[Results]To accurately screen input features and optimize dimensionality,the eXtreme Gradient Boosting(XGBoost)model with default parameters evaluated prediction errors across the original dataset,interpolated data,feature sets filtered by Deep Lasso and BorutaShap,their combinations,and the combined feature set.BorutaShap demonstrated the best screening performance.The proposed IBKA-TCN-TimesNet-BiLSTM model,driven by policy quantification,outperformed comparative models,achieving an average absolute percentage error of 2.64％,an average absolute error of 9.42,and a root-mean-square error of 11.44.[Conclusion]This method effectively adapts to natural gas demand forecasting under the influence of policies and multiple factors,providing valuable guidance for planning production,supply,storage,sales,and industry decision-making.(9 Figures,3 Tables,33 References)
[Objective]Injection and production pipes in salt cavern hydrogen storage face severe risks of hydrogen embrittlement and corrosion.There is an urgent need to develop highly effective hydrogen barrier coatings.This study aims to systematically evaluate and compare representative coatings to guide the selection and design of protection technologies suited to the salt cavern hydrogen storage environment.[Methods]TiN,AlCrN,and(TiAlCrSiY)N coatings were prepared on N80 steel via multi-arc ion plating.Their hydrogen permeation resistance was systematically assessed using a Devanathan-Stachurski double-electrolytic cell under two hydrogen charging modes(electrochemical monitoring in liquid and gas phases).Corrosion resistance was evaluated through electrochemical polarization curve tests.The microstructures and properties of the coatings were characterized by scanning electron microscope(SEM)and digital microscopy.By comparing the comprehensive protective performance of TiN,AlCrN,and(TiAlCrSiY)N coatings,differences in underlying mechanisms were analyzed to provide a scientific basis for selecting and designing hydrogen barrier coatings for salt cavern hydrogen storage environments.[Results]The AlCrN coating demonstrated the best overall performance,featuring the densest,flattest surface,fewest defects,highest hardness,and strongest bonding.Although the(TiAlCrSiY)N coating exhibited superior corrosion resistance due to the synergistic effect of multiple elements,it had numerous surface agglomerates,micro-defects,and the weakest bonding among the three coatings.Hydrogen permeation tests showed that AlCrN provided the most effective barrier,reducing the effective diffusion coefficient by 83.68％compared to the N80 substrate,with hydrogen barrier efficiencies of 99.23％in the gas phase and 84.76％in the liquid phase.All three coatings-TiN,AlCrN,and(TiAlCrSiY)N-offered good hydrogen barrier properties and enhanced substrate strength and corrosion resistance.The test and analysis results indicated that coating microstructure compactness primarily determined hydrogen barrier and mechanical properties,while corrosion resistance depended mainly on chemical composition.[Conclusion]In developing hydrogen barrier coatings for salt cavern hydrogen storage,priority should be given to achieving a dense,low-defect structure through process optimization,followed by composition optimization to enhance chemical stability.Simultaneously improving corrosion resistance and mechanical properties is crucial for ensuring the safe operation of salt cavern hydrogen storage facilities.(6 Figures,4 Tables,24 References)
