During the 13th Five-year Plan, the domestic oil and gas storage and transportation business developed rapidly, which promoted the progress of oil and gas storage and transportation technologies. In terms of engineering design and construction, a series of research results concerning high-grade steel pipeline design and mechanized construction have been achieved, and the design and construction technologies of LNG receiving terminals and storages become mature gradually. In terms of material and equipment, the key technical problems of the third generation large-capacity natural gas pipeline project were solved, the X70/X80 steel pipes were successfully developed with the key equipment such as the compressors, oil pumps and key valves localized basically. In addition, the localized SCADA software was also developed. In terms of the transportation technologies, the optimization technology of pipeline network operation with the centralized control as the core has been formed, and the transportation technology system of the high pour-point and high viscosity crude oils and product oils has been established. As for the operation and maintenance, the supporting technologies of pipeline integrity management, inspection and evaluation, geological hazard protection, monitoring and early warning, corrosion protection and emergency repairing have been developed, and many international and national standards have been prepared and published. During the 14th Five-year Plan, the oil and gas storage and transportation industry will face new opportunities and challenges in technology development, and the oil and gas storage and transportation technology will develop towards safe operation, efficient transportation and intelligent pipeline network, which will provide scientific support and guarantee for the rapid development of oil and gas storage and transportation businessess. (2 Tables, 57 References)

With the rapid development of the construction of high-pressure, large-diameter and long-distance X80 pipelines in China, Stress Corrosion Cracking (SCC) has become an important factor threatening the safe operation of pipelines. Herein, the key influencing factors of SCC of X80 pipeline steel in soil environment were summarized and analyzed. The influence of Alternating Current (AC) stray current on the SCC behavior of X80 pipeline steel and its influencing mechanism were analyzed, and it was pointed out that the alternating current and the elastic stress can cooperate with each other to jointly promote the anodic dissolution of X80 pipeline steel and destroy the state of dense corrosion product film on the steel surface, further accelerating the corrosion. In addition, the research status of the SCC mechanism of pipeline steel caused by Sulfate Reducing Bacteria (SRB) in soil environment was reviewed. It was concluded that the microbiologically-assisted cracking mechanism of X80 pipeline steel was mainly associated with the physiological activity of bacteria, its metabolites and the formation of biological film. Finally, suggestions on the selection of cathodic protection potential of X80 pipeline steel under SRB were proposed. Further, it is also recommended to include the microbial factors into the SCC evaluation system of pipeline steel. Therefore，the research results can provide theoretical guidance for the design and safety service of high-strength steel pipeline in China. (2 Figures, 46 References)

Large oil and gas pipeline networks are characterized by multiple source and sink nodes, large spatial span and high degree of coupling between the thermal and hydraulic processes, which lead to great difficulty in modeling. It is pointed out in the Medium and long-term oil and gas pipeline network planning that the intellectualization of pipeline networks is the development direction in the future, and building a hybrid model with clear physical meaning and strong generalization capabilities by combining the mechanism knowledge and the data-driven modeling method is critical to realize the intelligent pipeline networks. Herein, the characteristics of mechanism modeling and data-driven modeling were analyzed, the physical properties of the study object were described collaboratively by integrating the mechanism model and the datadriven model, the internal connection among the site data was fully mined, the evolution laws of the process variations were explored, and finally a high-fidelity hybrid model was established. In addition, various structures of hybrid models and the feasibility of their application in oil and gas pipeline industry was summarized, the strategies of hybrid modeling in various application scenarios were clarified and the direction of research on the mechanism and data based collaborative modeling technology in future was discussed. Further, the research results can provide reference to the construction of intelligent pipeline networks. (2 Figures, 60 References)

As the “decision-making brain” of a pipeline network system, the control centre is a comprehensive decisionmaking control centre that integrates large amounts of data, rules and expert experience. It is very similar to the development idea and evolution direction of a new generation of artificial intelligence characterized by data driving. Herein, the intelligent and digital transformation plans for the control business of the pipeline companies and the power grid companies at home and abroad were analyzed, and the latest research results were summarized. Then, combined with the latest development of artificial intelligence technology, the basic concepts and functional characteristics of intelligent control were preliminarily put forward based on the demand of natural gas pipeline networks for the control business, namely, to achieve the intelligent perception, prediction and early warning, optimal decision-making, and intelligent control, and ultimately to realize the intelligent control mode based on black screen. Subsequently, the architecture of intelligent control was designed, and the key technologies of the intelligent control layer and the intelligent decision layer, as well as their potential application scenarios, were analyzed. Finally, the research results are expected to provide reference for the development and application of artificial intelligence in the control of pipeline networks in the future. (3 Figures, 20 References)

In order to verify the applicability of epoxy-filled steel sleeves for reinforcement of the girth weld defects in X80 steel pipelines, X80 pipe fittings with 1 016 mm diameter were selected as the specimens and on the specimens two girth welds with same defects were set by manual welding. Definitely, one of the welds was reinforced with an epoxy-filled steel sleeve, while the other was not. Then, the full-scale mechanical tests were performed under the internal pressure, fluctuation pressure and the coupling effect of internal pressure and bending moment for the above two defective girth welds with/without reinforcement. In addition, the failure mode, bearing capacity and deformation performance of the two specimens were compared and analyzed. The results show that the hoop and axial stresses of the girth weld defects reinforced by the epoxy-filled steel sleeve under the operating pressure is reduced, and the sleeve shares 47% of the internal pressure. The stress of the girth weld defects reinforced by the epoxy-filled steel sleeves under the cyclic fluctuating pressure is kept unchanged, which indicates that the stress level of the sleeve reinforced girth weld defects is stable, without changing with the fluctuation of the pressures. In addition, under the coupling effect of the internal pressure and the bending moments, the failure mode of the unreinforced pipeline is overall fracture of the weld section, while the failure mode of the reinforced pipeline is local buckling failure in the pressure region after the yield of the steel in the tensile region, which indicates that the epoxy-filled steel sleeves increase the bending capacity of the pipelines and reduce the bending deflection. In brief, the research results can provide a reference to the engineering application of reinforcing the defective girth welds of X80 pipelines with epoxy-filled steel sleeves. (16 Figures, 24 References)

The actual strength under-matching of pipeline girth welds is a principal cause for the fracture failure of welds. The current Failure Assessment Diagram (FAD) method for the applicability assessment of pipeline welds cannot accurately consider the influence of weld strength matching. Thus, accurate inclusion of strength matching becomes critical to broaden the FAD method to apply to the crack defect assessment for the girth welds of high-grade steel pipelines. Based on the nonlinear finite element method, a numerical simulation model of the crack driving forces for the girth welds of high-grade steel pipelines was established, and the general failure assessment curve of girth weld cracks was plotted with the equivalent stress-strain relationship method. Then, a series of finite element assessment points under different load levels were determined with the finite element calculation results of the crack driving forces in combination with the recommended methods in Guide to methods for assessing the acceptability of flaws in metallic structures (BS 7910-2019). Further, the assessment accuracy of BS 7910-2019 to the crack defects of girth welds was determined, and the critical causes affecting the accuracy of the assessment results were investigated. On this basis, the optimized ultimate load calculation model of the pipeline girth welds and the improved FAD method were put forward with the crack depth, the crack length and the weld strength matching coefficient considered, and the weld strength matching was accurately included into the FAD method. Thereby, the assessment accuracy of the girth weld crack defects of the high-grade steel pipelines was further enhanced. Generally, the method could provide reference for the applicability assessment of the girth weld cracks of in-service high-grade steel pipelines. (11 Figures, 24 References)

Formation collapse is one of the common geological hazards for the buried long-distance pipelines. In order to study the mechanical response law of the buried steel pipelines under continuous collapse, experiments and numerical simulations of buried steel pipelines under continuous collapse were carried out, the deformation and stress changes of the buried steel pipelines during continuous collapse were analyzed, and the theoretical calculation results of pipeline mechanics under the collapse geological hazards were checked. The research results show that, in the case of collapse in a small area, the deformation and stress of pipelines increase continuously with the collapse area enlarged, and the displacement and stress in the middle of the pipelines are maximized. When the collapse area is expanded to a certain extent, the soil collapses completely, the pipelines are suspended, the displacement of the pipeline is reduced, the stress of the pipe is released greatly, and the maximum stress position of the pipelines changes from the middle to the point near the collapse boundary of the pipelines. The calculation results of the pipeline stress under the collapse geological hazards are greater than the experimental and simulation values if the friction or cohesion are considered based on the gravity, which are of more guiding significance. Further, the reasearch results could provide effective guidance to pipeline protection. (19 Figures, 4 Tables, 25 References)

Once a supercritical CO2 pipeline fractures, decompression wave will appear at both end of the crack. Hence, the calculation of the decompression wave velocity during the pipeline fracturing is critical for the prediction and control of pipeline fracture. Based on the GERG-2008 equation of state, a decompression wave velocity prediction model for the supercritical CO2 pipelines containing impurities was established with reference to the homogeneous flow model and the sound velocity calculation model for gas-liquid two-phase flow, and a calculation procedure thereof was developed. In addition, the effects of single-component non-polar impurities, single-component polar impurities and multi-component mixed impurities on the decompression wave curve of the supercritical CO2 pipelines were studied. The results show that the addition of non-polar impurities increases the plateau pressure of the decompression wave curve, and thus the decompression wave is more likely to intersect with the pipeline fracture curve, increasing the risk of pipeline fracture. However, the presence of polar impurities can slightly reduce the plateau pressure of the decompression wave curve of the supercritical CO2 pipelines, further reducing the risk of pipeline fracture. Therefore, this model could provide a theoretical basis for pipeline crack arrest and impurity composition control. (4 Figures, 2 Tables, 25 References)

In the middle and late production stages of natural gas condensate pipelines, the problems of increased liquid accumulation and friction usually occur in the pipelines. Therefore, regular pigging operations are essential to ensure the safety and efficiency of the oil and gas pipelines. However, the traditional pigs often go out of control as a result of their same velocity with the driving gas during the operation, which brings about a series of problems. Thereby, a new type of bypass pig was designed and developed, and a matching experimental system of horizontal-vertical pipelines was built to analyze the movement characteristics of the bypass pigs in different structures. Herein, air and water were used as the flow media, and the data of flow, pressure and terminal liquid level during pigging were collected by the LabView data collection system in real time. By changing the parameters such as the bypass rate, the driving gas velocity, the liquid velocity, etc., the movement characteristics of the bypass pig were explored, and the abnormal movement process of the pig and the internal mechanism of eliminating pig slug were analyzed. As shown in the results, the movement velocity of pigs can be slowed, the pressure fluctuation in the pipelines can be mitigated and the liquid holdup in the slugs before the pigs can be reduced with the bypass pigs for the purpose of effectively controlling the volume of slugs. The research results could provide references for in-depth understanding of mechanism of bypass pigging technology and promoting its engineering application. (14 Figures, 2 Tables, 39 References)

In the high pressure and low temperature conditions during the production and transportation of deep-sea oil and gas, hydrate is formed easily, which could cause pipeline blockage. Herein, for gas-liquid-solid flow system of hydrate slurry, the hydrate particles are classified according to the particle size based on the characteristics of the dispersed phase. In combination with the kinetics model of hydrate formation/decomposition, the number, size and movement laws of the hydrate particles were simulated, the two-fluid model and the temperature equation were coupled, and a multiphase transient flow mechanism model of hydrate slurry applicable to the oil-dominated flowlines was established. The governing equations were discretized by a staggered grid, and the coupled solution of multi-physics fields covering the multi-phase flow, the dynamic change of hydrate particle formation/decomposition and the movement of hydrate particles was realized on the basis of the pressure-based algorithm. By applying the model to a multiphase transportation pipeline, the change of the hydrate volume fraction were obtained, which could provide theoretical basis to the quantitative analysis on the blockage risk of hydrate slurry transportation. (12 Figures, 5 Tables, 37 References)

Efficient air filter element is a key component to prevent erosion, corrosion and solids precipitation in the flow path of gas turbine. However, the performance of the air filter element is significantly reduced in high humidity environment, which seriously affects the safe operation of gas turbine. Herein, the filtration performance of four types of filter element made of F9 filter materials was tested. By comparing the tensile strength of the filter materials under different conditions, the change of pressure drop and efficiency of the filter element was measured in the conditions with different droplet mass concentration. The results show that the moisture resistance of the filter material mainly depends on the fiber composition. The synthetic fiber can effectively reduce the water absorption rate of the filter materials, and the filter element made of materials with low water absorption rate has a stronger capability to maintain its original performance with the influence of water spray. The research results could provide technical reference for the operation and maintenance of gas turbine inlet filtration system and the development of efficient moisture-resistant filter elements. (5 Figures, 3 Tables, 20 References)

For the failure of oil storage and transportation facilities may endanger the surrounding public safety, it is necessary to conduct quantitative assessment for the derived disasters under multiple scenarios so as to effectively control the adverse impact resulted from the accidents of oil storage and transportation facilities. Meanwhile, research should also be performed for the consequence assessment system of derived disasters. Herein, the differences between the common and the serious accidents were analyzed, and the derived disasters of oil and gas storage and transportation facilities were defined to comprehensively identify the probability and consequences of disasters. In addition, an assessment model of derived disasters based on the sensibility of the disaster-inducing environment was put forward from the three aspects of the derived disaster system, the disaster-causing mechanism and the disaster-inducing environment. A case study was carried out to a disaster occurred in the densely-populated and environmental sensitive areas. Specifically, the failure probability of the oil storage and transportation facilities and the sensitivity of the disaster-inducing environment in the areas after the fire caused by the pipeline leakage were calculated with the Bayesian network using the derived disaster assessment model. The results show that the derived disaster assessment system with comprehensive consideration to the disaster frequency and consequences can not only characterize the degree of loss as a result of multi-scenario disasters, but also reflect the disaster characteristics of accidents of the storage and transportation facilities, which further provides reference to the development of safety measures of the pipelines and facilities for oil storage and transportation, as well as the emergency management and the planning of emergent resources. (7 Figures, 6 Tables, 21 References)

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. (7 Figures, 5 Tables, 22 References)