This paper analyses the impact of oil and gas pipelines on the environment and settlements from the perspective of environmental justice,using a case study of the oil-producing communities in the Niger Delta region of...This paper analyses the impact of oil and gas pipelines on the environment and settlements from the perspective of environmental justice,using a case study of the oil-producing communities in the Niger Delta region of Nigeria.The paper mobilises theories of environmental justice to support an in-depth empirical analysis of the development and management of oil and gas pipelines in the region.The empirical evidence equally suggests that the lack of community involvement and appropriate recognition of some groups of stakeholders in the management of the oil and gas pipeline project is strongly related to the incidence of pipeline impacts on the communities[1].The paper advocates a new approach,based on the core principles of environmental justice that promotes inclusion of the necessary stakeholders,including the physical planners,and would incorporate local knowledge and experience into the environmental management of the region in a way to protect the environment and people from the impacts of the pipeline[2].展开更多
Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crac...Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.展开更多
With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and lea...With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and leading to significant economic losses and fatalities.As oil and gas exploration moves deeper into the ocean,the issue of hydrate blockages has become more severe.It is essential to take adequate measures promptly to mitigate the hazards of hydrate blockages after they form.However,a prerequisite for effective mitigation is accurately detecting the location and amount of hydrate formation.This article summarizes the temperature–pressure,acoustic,electrical,instrumental–response,and flow characteristics of hydrate formation and blocking under various conditions.It also analyzes the principles,limitations,and applicability of various blockage detection methods,including acoustic,transient,and fiber-optic-based methods.Finally,it lists the results of field experiments and commercially used products.Given their advantages of accuracy and a wide detection range,acoustic pulse reflectometry and transient-based methods are considered effective for detecting hydrate blockages in future underwater pipelines.Using strict backpressure warnings combined with accurate detection via acoustic pulse reflectometry or transient-based methods,efficient and timely diagnosis of hydrate blockages can be achieved.The use of a hydrate model combined with fiber optics could prove to be an effective method for detecting blockages in newly laid pipelines in the future.展开更多
A comprehensive and objective risk evaluation model of oil and gas pipelines based on an improved analytic hierarchy process(AHP)and technique for order preference by similarity to an ideal solution(TOPSIS)is establis...A comprehensive and objective risk evaluation model of oil and gas pipelines based on an improved analytic hierarchy process(AHP)and technique for order preference by similarity to an ideal solution(TOPSIS)is established to identify potential hazards in time.First,a barrier model and fault tree analysis are used to establish an index system for oil and gas pipeline risk evaluation on the basis of five important factors:corrosion,external interference,material/construction,natural disasters,and function and operation.Next,the index weight for oil and gas pipeline risk evaluation is computed by applying the improved AHP based on the five-scale method.Then,the TOPSIS of a multi-attribute decision-making theory is studied.The method for determining positive/negative ideal solutions and the normalized equation for benefit/cost indexes is improved to render TOPSIS applicable for the comprehensive risk evaluation of pipelines.The closeness coefficient of oil and gas pipelines is calculated by applying the improved TOPSIS.Finally,the weight and the closeness coefficient are combined to determine the risk level of pipelines.Empirical research using a long-distance pipeline as an example is conducted,and adjustment factors are used to verify the model.Results show that the risk evaluation model of oil and gas pipelines based on the improved AHP–TOPSIS is valuable and feasible.The model comprehensively considers the risk factors of oil and gas pipelines and provides comprehensive,rational,and scientific evaluation results.It represents a new decision-making method for systems engineering in pipeline enterprises and provides a comprehensive understanding of the safety status of oil and gas pipelines.The new system engineering decision-making method is important for preventing oil and gas pipeline accidents.展开更多
Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is...Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.展开更多
In recent years, there are more and more crude oil long-distance pipeline projects in our country. Although these projects meet the demand of crude oil resources, due to the large time and space span of construction, ...In recent years, there are more and more crude oil long-distance pipeline projects in our country. Although these projects meet the demand of crude oil resources, due to the large time and space span of construction, the construction of crude oil long-distance pipeline is technically difficult and there are many construction safety risks. Therefore, the safety of long-distance oil and gas pipelines needs to be further improved. This paper focuses on the in-depth research on the safety of long-distance oil and natural gas pipelines, and puts forward the correct countermeasures, which plays a great role in the safe operation of China's long-distance oil and natural gas pipelines and the level of their safety supervision.展开更多
Many years experience of the operation of high stress(>72%specified minimum yield strength,SMYS)gas pipelines and statistical analysis results of pipeline incidents showed that the operating pipelines at stress lev...Many years experience of the operation of high stress(>72%specified minimum yield strength,SMYS)gas pipelines and statistical analysis results of pipeline incidents showed that the operating pipelines at stress levels over 72%SMYS have not presented problems in USA and Canada,and design factor does not control incidents or the safety of pipelines.Enhancing pipeline safety management level is most important for decreasing incident rate.The application history of higher design factors in the U.S and Canada was reviewed.And the effect of higher factors to the critical flaw size,puncture resistance,change of reliability with time,risk level and the arrest toughness requirements of pipeline were analyzed here.The comparison of pipeline failure rates and risk levels between two design factors(0.72 and 0.8)has shown that a change in design factor from 0.72 to 0.8 would bring little effect on failure rates and risk levels.On the basis of the analysis result,the application feasibility of design factor of 0.8 in China was discussed and the related suggestions were proposed.When an operator wishes to apply design factor 0.8 to gas pipeline,the following process is recommended:stress level of line pipe hydro test should be up to 100%SMYS,reliability and risk assessment at the design feasibility or conceptual stage should be conducted,Charpy impact energy should meet the need of pipeline crack arrest;and establish and execute risk based integrity management plan.The technology of pipeline steel metallurgy,line pipe fabrication and pipeline construction,and line pipe quality control level in China achieved tremendous progresses,and line pipe product standards and property indexes have come up to international advanced level.Furthermore,pipeline safety management has improved greatly in China.Consequently,the research for the feasibility of application of design factor of 0.8 in China has fundamental basis.展开更多
This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning ...This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.展开更多
According to the investigations on the oil and gas pipelines such as the Lan-Cheng-Chong pipeline and the Southwest pipeline, there are two ways of laying pipeline： pipelines paralleling （approximately） to the main...According to the investigations on the oil and gas pipelines such as the Lan-Cheng-Chong pipeline and the Southwest pipeline, there are two ways of laying pipeline： pipelines paralleling （approximately） to the main slide direction and pipelines perpendicular （approximately） to the main slide direction. If earth-retaining walls have been built for pipelines paralleling to the main slide direction, they will prevent the lands from sliding; On the contrary, without earth-retaining walls, the sharp broken rocks in the backfilling soil will scratch the safeguard of the pipeline when the landslides take place. Pipelines perpendicular to the main slide direction can be classified into four types according to the relative positions between pipelines and landslides： Pipelines over the slide planes, pipelines inside the fracture strips of slide planes, pipelines below the slide planes and pipelines behind the backsides of landslides. The different dynamical mechanisms of the process in which landslide acts against pipelines are analyzed based on whether the pipelines are equipped with fixed frusta, because the sliding resistance depends on whether and how many fixed frusta are equipped and the distance between frusta.展开更多
In past decades dynamic programming, genetic algorithms, ant colony optimization algorithms and some gradient algorithms have been applied to power optimization of gas pipelines. In this paper a power optimization mod...In past decades dynamic programming, genetic algorithms, ant colony optimization algorithms and some gradient algorithms have been applied to power optimization of gas pipelines. In this paper a power optimization model for gas pipelines is developed and an improved particle swarm optimization algorithm is applied. Based on the testing of the parameters involved in the algorithm which need to be defined artificially, the values of these parameters have been recommended which can make the algorithm reach efficiently the approximate optimum solution with required accuracy. Some examples have shown that the relative error of the particle swarm optimization over ant colony optimization and dynamic programming is less than 1% and the computation time is much less than that of ant colony optimization and dynamic programming.展开更多
For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic...For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.展开更多
There are a lot of researches on qualitative aseismatic measures for buried gas pipeline crossing movable faults.But a few of them are quantitative,especially in the size and shape of the trench.The paper first establ...There are a lot of researches on qualitative aseismatic measures for buried gas pipeline crossing movable faults.But a few of them are quantitative,especially in the size and shape of the trench.The paper first established the finite element model of the strain of buried pipeline crossing a fault which effected by the size and shape of the trench.And it obtained new soil spring stiffness which considered different buried depth,bottom width of trench,trench slope and elastic modulus of soil.The mechanical analysis model of pipeline is established,and the limit state equation of pipeline is fitted.The reliability and sensitivity of the natural gas pipeline under fault action are analysed by a Monte Carlo method,and the error and accuracy are verified.When the pipeline is under tension,the sensitivity from large to small is buried depth,sand friction angle,pipe diameter,pipeline displacement,trench bottom width,trench depth,clay cohesion,trench slope and clay friction angle;when the pipeline is under pressure,the trench depth and clay cohesion have great influence.The findings of this study provide a reference for pipeline design and safety evaluation under fault action.展开更多
This paper proposes an estimation method of fracture resistance of oil ＆ gas pipes, based on the results of full scale hydraulic pressure pipe testing with the artificial notch, made by the authors at 2002-2006. It s...This paper proposes an estimation method of fracture resistance of oil ＆ gas pipes, based on the results of full scale hydraulic pressure pipe testing with the artificial notch, made by the authors at 2002-2006. It shows that the fracture process at the stage of stripping （initialization） of crack can be characterized by Critical Fracture Diagram （CFD）. Calculating and experimental way to construct CFD is suggested and discussed. The fracture resistance requirements for oil ＆ gas pipes in terms of fracture mechanics （Kc, Lc） are formulated and proved. The results of full scale hydraulic pressure pipe testing, based on metal testing data of the standard Charpy specimens （KCV） and pipe＇s specification requirements are interrelated. The way to estimate the admissible temperature operation conditions of oil ＆ gas pipes by means of based metal ＂KCV-temperature＂ dependence is proposed.展开更多
To prevent the thawing of ice-rich permafrost,it is suggested that gas should be transported in a chilled state(below the freezing temperature)in pipelines buried in permafrost.However,frost heave occurs when water mi...To prevent the thawing of ice-rich permafrost,it is suggested that gas should be transported in a chilled state(below the freezing temperature)in pipelines buried in permafrost.However,frost heave occurs when water migrates towards the chilled pipeline and ice lenses grow underneath the pipe.This might endanger the integrity of the pipeline and the environment as well.Therefore,innovative frost heave mitigation measures are required when designing the pipeline,especially those sections in discontinuous permafrost or near the compressor stations.The ground temperature field in response to the operation of a proposed chilled gas pipeline traversing permafrost regions in Alaska was simulated by a pipe-soil thermal interaction geothermal model.Frost heave mitigation measures,including insulation around the pipe,flat slab insulation under the pipe,and heating cables combined with slab insulation,were evaluated for chilled pipeline operation in seasonally varying ambient temperatures.The numerical results show that the minimum temperature of the observation point at 2.5 m below the pipe bottom increases by 17%,29%,and 48%when the thermal conductivity of the outer insulation layer is 0.1,0.05,and 0.02 W/(m K),respectively.For flat slab insulation,the thermal field is less sensitive to varying slab thicknesses than to varying thermal conductivity,implying the thermal conductivity,not the thickness,is the crucial factor.Additionally,the heat flow could be redirected from vertical to horizontal by flat slab insulation.The electrical heating cables could be regarded as a new heat source to balance the heat removal rate of the soil around the chilled pipe.The minimum temperature of the observation point at 1.1 m below the bottom of the pipe increases from-15.2℃to-3.0,1.5,and 7.5℃,corresponding to the heating cable power of 20,30,and 40 W,respectively,with the power of 30 W deemed appropriate for the study case.It is concluded that heating cables in combination with insulation slabs could be adopted to regulate the temperature field around the chilled pipeline efficiently and economically.The advantages of this combination include redirecting the heat flow and eliminating frost in the soil underlying the pipe.These approaches could be considered for applications in gas pipeline projects in arctic and alpine/high-plateau permafrost regions.展开更多
In the cold regions of northern China, incidents of municipal underground gas pipeline rupture and leakage occur quite fi-equently, aaost often in winter. To prevent harm to citizen safety and property, analysis of th...In the cold regions of northern China, incidents of municipal underground gas pipeline rupture and leakage occur quite fi-equently, aaost often in winter. To prevent harm to citizen safety and property, analysis of the causes of such cracking and leakage is therefore valuable. Two incident analyses are discussed here and the reasons why most of these types of cases occur dttring winter are clarified. Fhe effects of vehicle loadings above buried pipelines are calculated and compared with the effects and calculations of frost heaving forces. We demonstrate thtit when the soil layer above a pipeline freezes rapidly, the soil generates repeated frost heaving, which exerts heaving forces on the pipeline that can result in fatigue crack propagation and ultimate pipeline failure. Therefore, the incident induced 9y frost heaving is one of the primary reasons of gas pipeline failure. Based on these analyses, we present some recommendations pertaining to the proper design, construction, and management of gas pipelines.展开更多
The current national criteria cannot accurately reflect the multi-crack interference effect of defective gas pipelines,and thus result in conservative assessment results.In order to improve the safety assessment accur...The current national criteria cannot accurately reflect the multi-crack interference effect of defective gas pipelines,and thus result in conservative assessment results.In order to improve the safety assessment accuracy of defective gas pipelines,we compared the singular element method with the three-dimensional virtual crack closure technology(3D-VCCT),then,selected the 3D-VCCT to build a multi-crack interference model of gas pipelines,and finally,studied the interference effect of subsidiary cracks on the front points of the main crack by analyzing the variation of the interference factors between cracks.The following research results were obtained:first,as the subsidiary crack size changes,the strongest interference effect of a parallel collinear crack occurs near the surface of the crack,exhibiting an enhances effect;second,under certain conditions,the interference effect of a parallel coaxial crack is more significant at the deepest point and the surface point of the crack,and exhibits an enhanced effect at the deepest point and a weakened effect at the surface point;third,when the horizontal spacing between cracks is 6 times greater than the major semi-axis of the main crack,the interference effect of parallel collinear cracks and parallel bias cracks is very little,and multi-cracks can be simplified as a single crack for analysis.The research results not only can provide technical references for fracture analysis of multi-crack gas pipelines,but also can provide theoretical basis for the safety assessment of multi-cracks of the gas pipelines.展开更多
In this paper,a finite element model with girth weld defects considering crack tip singularity was established in order to facilitate the accurate and rapid safety assessment on girth weld defects of long distance gas...In this paper,a finite element model with girth weld defects considering crack tip singularity was established in order to facilitate the accurate and rapid safety assessment on girth weld defects of long distance gas Transmission pipeline.Then the J-integral of girth weld cracks in pipes with different defect sizes was calculated,and the influence of weld matching coefficient and material hardening index on J-integral is analyzed.Furthermore,the influence factors of limit load of pipeline with girth weld defects based on J-integral theory are studied.Based on this,the engineering calculation formula which can calculate J-integral and limit load rapidly in the situations with specific matching coefficient and material hardening index was proposed.And the following research results were obtained.First,the engineering calculation formula based on the fitting of finite element calculation results has high accuracy,which can calculate the J-integral of defects in a large geometric range and the limit load of pipelines with girth weld cracks.Second,the J-integral of cracks in pipes with girth weld defects is closely related to defect size,material properties and weld matching coefficient,and the limit load of pipes with defects decreases as the crack size increases and increases as the material hardening index increases.Third,for the X80 pipes with surface cracks at the centerline of the girth weld,the load carrying capacity of the pipes with low-strength matched weld are lower than that with high-strength or equivalent-matched weld.In conclusion,the research results can be used as reference for the safety evaluation and integrity management of in-service gas pipelines.展开更多
At present, oil and gas as the basic energy, all kinds of social industry development are closely related to it. Oil and gas transportation is related to the lifeline and economic benefits of the country, as well as t...At present, oil and gas as the basic energy, all kinds of social industry development are closely related to it. Oil and gas transportation is related to the lifeline and economic benefits of the country, as well as the stable development of the society. Oil and gas transportation quality assurance is the key to social and economic development and enterprise economic development. The pipeline storage and transportation work must attract the attention of relevant personnel, and especially the transportation safety will have a decisive impact on the safety of the use of oil and natural gas. At present, the safety assurance technology of oil and gas pipelines and storage and transportation facilities cannot fully meet the needs of social development, which requires further improvement and optimization.展开更多
文摘This paper analyses the impact of oil and gas pipelines on the environment and settlements from the perspective of environmental justice,using a case study of the oil-producing communities in the Niger Delta region of Nigeria.The paper mobilises theories of environmental justice to support an in-depth empirical analysis of the development and management of oil and gas pipelines in the region.The empirical evidence equally suggests that the lack of community involvement and appropriate recognition of some groups of stakeholders in the management of the oil and gas pipeline project is strongly related to the incidence of pipeline impacts on the communities[1].The paper advocates a new approach,based on the core principles of environmental justice that promotes inclusion of the necessary stakeholders,including the physical planners,and would incorporate local knowledge and experience into the environmental management of the region in a way to protect the environment and people from the impacts of the pipeline[2].
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.
基金supported by the National Natural Science Foundation of China(52476058,U21B2065,52006024,and 52306188)the National Key Research and Development(2022YFC2806200).
文摘With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and leading to significant economic losses and fatalities.As oil and gas exploration moves deeper into the ocean,the issue of hydrate blockages has become more severe.It is essential to take adequate measures promptly to mitigate the hazards of hydrate blockages after they form.However,a prerequisite for effective mitigation is accurately detecting the location and amount of hydrate formation.This article summarizes the temperature–pressure,acoustic,electrical,instrumental–response,and flow characteristics of hydrate formation and blocking under various conditions.It also analyzes the principles,limitations,and applicability of various blockage detection methods,including acoustic,transient,and fiber-optic-based methods.Finally,it lists the results of field experiments and commercially used products.Given their advantages of accuracy and a wide detection range,acoustic pulse reflectometry and transient-based methods are considered effective for detecting hydrate blockages in future underwater pipelines.Using strict backpressure warnings combined with accurate detection via acoustic pulse reflectometry or transient-based methods,efficient and timely diagnosis of hydrate blockages can be achieved.The use of a hydrate model combined with fiber optics could prove to be an effective method for detecting blockages in newly laid pipelines in the future.
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFC0805804,2017YFC0805801)
文摘A comprehensive and objective risk evaluation model of oil and gas pipelines based on an improved analytic hierarchy process(AHP)and technique for order preference by similarity to an ideal solution(TOPSIS)is established to identify potential hazards in time.First,a barrier model and fault tree analysis are used to establish an index system for oil and gas pipeline risk evaluation on the basis of five important factors:corrosion,external interference,material/construction,natural disasters,and function and operation.Next,the index weight for oil and gas pipeline risk evaluation is computed by applying the improved AHP based on the five-scale method.Then,the TOPSIS of a multi-attribute decision-making theory is studied.The method for determining positive/negative ideal solutions and the normalized equation for benefit/cost indexes is improved to render TOPSIS applicable for the comprehensive risk evaluation of pipelines.The closeness coefficient of oil and gas pipelines is calculated by applying the improved TOPSIS.Finally,the weight and the closeness coefficient are combined to determine the risk level of pipelines.Empirical research using a long-distance pipeline as an example is conducted,and adjustment factors are used to verify the model.Results show that the risk evaluation model of oil and gas pipelines based on the improved AHP–TOPSIS is valuable and feasible.The model comprehensively considers the risk factors of oil and gas pipelines and provides comprehensive,rational,and scientific evaluation results.It represents a new decision-making method for systems engineering in pipeline enterprises and provides a comprehensive understanding of the safety status of oil and gas pipelines.The new system engineering decision-making method is important for preventing oil and gas pipeline accidents.
基金supported by the National Key R&D Program of China(Grant No.2018YFC0809300)the National Natural Science Foundation of China(Grant No.51806247)+2 种基金the Key Technology Project of Petro China Co Ltd.(Grant No.ZLZX2020-05)the Foundation of Sinopec(Grant No.320034)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462020YXZZ052)
文摘Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.
文摘In recent years, there are more and more crude oil long-distance pipeline projects in our country. Although these projects meet the demand of crude oil resources, due to the large time and space span of construction, the construction of crude oil long-distance pipeline is technically difficult and there are many construction safety risks. Therefore, the safety of long-distance oil and gas pipelines needs to be further improved. This paper focuses on the in-depth research on the safety of long-distance oil and natural gas pipelines, and puts forward the correct countermeasures, which plays a great role in the safe operation of China's long-distance oil and natural gas pipelines and the level of their safety supervision.
基金supported by China National Petroleum Corporation Application Fundamental Research Foundation(Grant No.07A40401)
文摘Many years experience of the operation of high stress(>72%specified minimum yield strength,SMYS)gas pipelines and statistical analysis results of pipeline incidents showed that the operating pipelines at stress levels over 72%SMYS have not presented problems in USA and Canada,and design factor does not control incidents or the safety of pipelines.Enhancing pipeline safety management level is most important for decreasing incident rate.The application history of higher design factors in the U.S and Canada was reviewed.And the effect of higher factors to the critical flaw size,puncture resistance,change of reliability with time,risk level and the arrest toughness requirements of pipeline were analyzed here.The comparison of pipeline failure rates and risk levels between two design factors(0.72 and 0.8)has shown that a change in design factor from 0.72 to 0.8 would bring little effect on failure rates and risk levels.On the basis of the analysis result,the application feasibility of design factor of 0.8 in China was discussed and the related suggestions were proposed.When an operator wishes to apply design factor 0.8 to gas pipeline,the following process is recommended:stress level of line pipe hydro test should be up to 100%SMYS,reliability and risk assessment at the design feasibility or conceptual stage should be conducted,Charpy impact energy should meet the need of pipeline crack arrest;and establish and execute risk based integrity management plan.The technology of pipeline steel metallurgy,line pipe fabrication and pipeline construction,and line pipe quality control level in China achieved tremendous progresses,and line pipe product standards and property indexes have come up to international advanced level.Furthermore,pipeline safety management has improved greatly in China.Consequently,the research for the feasibility of application of design factor of 0.8 in China has fundamental basis.
基金funded by the National Science and Technology Support Program (2015BAK16B02 and 2015BAK16B01)the Fundamental Research Funds of China Academy of Safety Science and Technology
文摘This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.
文摘According to the investigations on the oil and gas pipelines such as the Lan-Cheng-Chong pipeline and the Southwest pipeline, there are two ways of laying pipeline： pipelines paralleling （approximately） to the main slide direction and pipelines perpendicular （approximately） to the main slide direction. If earth-retaining walls have been built for pipelines paralleling to the main slide direction, they will prevent the lands from sliding; On the contrary, without earth-retaining walls, the sharp broken rocks in the backfilling soil will scratch the safeguard of the pipeline when the landslides take place. Pipelines perpendicular to the main slide direction can be classified into four types according to the relative positions between pipelines and landslides： Pipelines over the slide planes, pipelines inside the fracture strips of slide planes, pipelines below the slide planes and pipelines behind the backsides of landslides. The different dynamical mechanisms of the process in which landslide acts against pipelines are analyzed based on whether the pipelines are equipped with fixed frusta, because the sliding resistance depends on whether and how many fixed frusta are equipped and the distance between frusta.
文摘In past decades dynamic programming, genetic algorithms, ant colony optimization algorithms and some gradient algorithms have been applied to power optimization of gas pipelines. In this paper a power optimization model for gas pipelines is developed and an improved particle swarm optimization algorithm is applied. Based on the testing of the parameters involved in the algorithm which need to be defined artificially, the values of these parameters have been recommended which can make the algorithm reach efficiently the approximate optimum solution with required accuracy. Some examples have shown that the relative error of the particle swarm optimization over ant colony optimization and dynamic programming is less than 1% and the computation time is much less than that of ant colony optimization and dynamic programming.
基金Project(51004005) supported by the National Natural Science Foundation of ChinaProject supported by Open Research Fund Program of Beijing Engineering Research Center of Monitoring for Construction Safety (Beijing University of Civil Engineering and Architecture), China
文摘For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.
基金financial support by China Petroleum Science&Technology Innovation Fund(2017D-50070606):Reliability research of large diameter and high steel natural gas pipeline under fault action。
文摘There are a lot of researches on qualitative aseismatic measures for buried gas pipeline crossing movable faults.But a few of them are quantitative,especially in the size and shape of the trench.The paper first established the finite element model of the strain of buried pipeline crossing a fault which effected by the size and shape of the trench.And it obtained new soil spring stiffness which considered different buried depth,bottom width of trench,trench slope and elastic modulus of soil.The mechanical analysis model of pipeline is established,and the limit state equation of pipeline is fitted.The reliability and sensitivity of the natural gas pipeline under fault action are analysed by a Monte Carlo method,and the error and accuracy are verified.When the pipeline is under tension,the sensitivity from large to small is buried depth,sand friction angle,pipe diameter,pipeline displacement,trench bottom width,trench depth,clay cohesion,trench slope and clay friction angle;when the pipeline is under pressure,the trench depth and clay cohesion have great influence.The findings of this study provide a reference for pipeline design and safety evaluation under fault action.
文摘This paper proposes an estimation method of fracture resistance of oil ＆ gas pipes, based on the results of full scale hydraulic pressure pipe testing with the artificial notch, made by the authors at 2002-2006. It shows that the fracture process at the stage of stripping （initialization） of crack can be characterized by Critical Fracture Diagram （CFD）. Calculating and experimental way to construct CFD is suggested and discussed. The fracture resistance requirements for oil ＆ gas pipes in terms of fracture mechanics （Kc, Lc） are formulated and proved. The results of full scale hydraulic pressure pipe testing, based on metal testing data of the standard Charpy specimens （KCV） and pipe＇s specification requirements are interrelated. The way to estimate the admissible temperature operation conditions of oil ＆ gas pipes by means of based metal ＂KCV-temperature＂ dependence is proposed.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20100103).
文摘To prevent the thawing of ice-rich permafrost,it is suggested that gas should be transported in a chilled state(below the freezing temperature)in pipelines buried in permafrost.However,frost heave occurs when water migrates towards the chilled pipeline and ice lenses grow underneath the pipe.This might endanger the integrity of the pipeline and the environment as well.Therefore,innovative frost heave mitigation measures are required when designing the pipeline,especially those sections in discontinuous permafrost or near the compressor stations.The ground temperature field in response to the operation of a proposed chilled gas pipeline traversing permafrost regions in Alaska was simulated by a pipe-soil thermal interaction geothermal model.Frost heave mitigation measures,including insulation around the pipe,flat slab insulation under the pipe,and heating cables combined with slab insulation,were evaluated for chilled pipeline operation in seasonally varying ambient temperatures.The numerical results show that the minimum temperature of the observation point at 2.5 m below the pipe bottom increases by 17%,29%,and 48%when the thermal conductivity of the outer insulation layer is 0.1,0.05,and 0.02 W/(m K),respectively.For flat slab insulation,the thermal field is less sensitive to varying slab thicknesses than to varying thermal conductivity,implying the thermal conductivity,not the thickness,is the crucial factor.Additionally,the heat flow could be redirected from vertical to horizontal by flat slab insulation.The electrical heating cables could be regarded as a new heat source to balance the heat removal rate of the soil around the chilled pipe.The minimum temperature of the observation point at 1.1 m below the bottom of the pipe increases from-15.2℃to-3.0,1.5,and 7.5℃,corresponding to the heating cable power of 20,30,and 40 W,respectively,with the power of 30 W deemed appropriate for the study case.It is concluded that heating cables in combination with insulation slabs could be adopted to regulate the temperature field around the chilled pipeline efficiently and economically.The advantages of this combination include redirecting the heat flow and eliminating frost in the soil underlying the pipe.These approaches could be considered for applications in gas pipeline projects in arctic and alpine/high-plateau permafrost regions.
基金supported by the National Natural Science Foundation of China (NNSF) (No. 10472020)the Special Foundation of Dalian University of Technology (DUT) (DUTTX2009-103)
文摘In the cold regions of northern China, incidents of municipal underground gas pipeline rupture and leakage occur quite fi-equently, aaost often in winter. To prevent harm to citizen safety and property, analysis of the causes of such cracking and leakage is therefore valuable. Two incident analyses are discussed here and the reasons why most of these types of cases occur dttring winter are clarified. Fhe effects of vehicle loadings above buried pipelines are calculated and compared with the effects and calculations of frost heaving forces. We demonstrate thtit when the soil layer above a pipeline freezes rapidly, the soil generates repeated frost heaving, which exerts heaving forces on the pipeline that can result in fatigue crack propagation and ultimate pipeline failure. Therefore, the incident induced 9y frost heaving is one of the primary reasons of gas pipeline failure. Based on these analyses, we present some recommendations pertaining to the proper design, construction, and management of gas pipelines.
基金Project supported by National Science and Technology Infrastructure Program“Risk-based key technologies for preventing pipeline accidents”(No.:2011BAK06B01-11).
文摘The current national criteria cannot accurately reflect the multi-crack interference effect of defective gas pipelines,and thus result in conservative assessment results.In order to improve the safety assessment accuracy of defective gas pipelines,we compared the singular element method with the three-dimensional virtual crack closure technology(3D-VCCT),then,selected the 3D-VCCT to build a multi-crack interference model of gas pipelines,and finally,studied the interference effect of subsidiary cracks on the front points of the main crack by analyzing the variation of the interference factors between cracks.The following research results were obtained:first,as the subsidiary crack size changes,the strongest interference effect of a parallel collinear crack occurs near the surface of the crack,exhibiting an enhances effect;second,under certain conditions,the interference effect of a parallel coaxial crack is more significant at the deepest point and the surface point of the crack,and exhibits an enhanced effect at the deepest point and a weakened effect at the surface point;third,when the horizontal spacing between cracks is 6 times greater than the major semi-axis of the main crack,the interference effect of parallel collinear cracks and parallel bias cracks is very little,and multi-cracks can be simplified as a single crack for analysis.The research results not only can provide technical references for fracture analysis of multi-crack gas pipelines,but also can provide theoretical basis for the safety assessment of multi-cracks of the gas pipelines.
基金Project supported by the National Key R&D Program of China“Integrity Evaluation Technology of Oil/Gas Pipeline and Storage and Transportation Facilities”(No.:2016YFC0802105)National Science and Technology Major Project“Development Demonstration Project of Large Carbonate Gas Field in Sichuan Basin-Key Technology Research and Solutions of HSE Guarantee in Large Sour Gas Field Development”(No.:2016ZX05052).
文摘In this paper,a finite element model with girth weld defects considering crack tip singularity was established in order to facilitate the accurate and rapid safety assessment on girth weld defects of long distance gas Transmission pipeline.Then the J-integral of girth weld cracks in pipes with different defect sizes was calculated,and the influence of weld matching coefficient and material hardening index on J-integral is analyzed.Furthermore,the influence factors of limit load of pipeline with girth weld defects based on J-integral theory are studied.Based on this,the engineering calculation formula which can calculate J-integral and limit load rapidly in the situations with specific matching coefficient and material hardening index was proposed.And the following research results were obtained.First,the engineering calculation formula based on the fitting of finite element calculation results has high accuracy,which can calculate the J-integral of defects in a large geometric range and the limit load of pipelines with girth weld cracks.Second,the J-integral of cracks in pipes with girth weld defects is closely related to defect size,material properties and weld matching coefficient,and the limit load of pipes with defects decreases as the crack size increases and increases as the material hardening index increases.Third,for the X80 pipes with surface cracks at the centerline of the girth weld,the load carrying capacity of the pipes with low-strength matched weld are lower than that with high-strength or equivalent-matched weld.In conclusion,the research results can be used as reference for the safety evaluation and integrity management of in-service gas pipelines.
文摘At present, oil and gas as the basic energy, all kinds of social industry development are closely related to it. Oil and gas transportation is related to the lifeline and economic benefits of the country, as well as the stable development of the society. Oil and gas transportation quality assurance is the key to social and economic development and enterprise economic development. The pipeline storage and transportation work must attract the attention of relevant personnel, and especially the transportation safety will have a decisive impact on the safety of the use of oil and natural gas. At present, the safety assurance technology of oil and gas pipelines and storage and transportation facilities cannot fully meet the needs of social development, which requires further improvement and optimization.
