Risk Analysis Of Crack Damage In Submarine Pipeline System

The submarine pipeline system is the main mode of transportation of offshore oil and gas resources.What's more,it is also the backbone of the Marine energy industry.Because of the complex service environment of the submarine pipeline system,the submarine pipeline is vulnerable to corrosion.At the same time,third-party damage and environmental impacts often threaten the submarine pipeline.Obviously,the submarine pipeline is prone to very dangerous crack damage.The mechanism involved in the initiation and propagation of submarine pipeline cracks is quite complex.It may be a single factor or a combination of factors.When the submarine pipeline crack expands to a certain extent,it will cause damage and failure of the pipeline.Therefore,it is of great significance to apply reasonable risk assessment techniques to the risk analysis of submarine pipeline system crack damage.The main purpose of this paper is to analyze the crack damage risk of submarine pipeline system.The research is mainly carried out from the following three aspects.(1)Statistics and analysis of crack damage accidents in submarine pipeline system.The author first analyzes the accident data of submarine pipeline at home and abroad.Meanwhile,the data of submarine pipeline accidents caused by cracks at home and abroad have also been included in the analysis.The two types of accident data are complementary to each other.Eventually four kinds of risk factors,including corrosion factor,misoperation factor,third-party damage factor and natural environment factor,which are closely related to submarine pipeline crack damage,are obtained by combining various crack generation mechanisms after analysis.(2)Fault tree qualitative and quantitative analysis of submarine pipeline system crack damage.Based on the statistical analysis of failure risk factors of submarine pipeline crack damage,this paper applies the classical fault tree analysis to qualitative analysis of submarine pipeline crack damage.Moreover,a fault tree quantitative analysis model of submarine pipeline system crack damage was established by combining expert judgment method and fuzzy set theory.In addition,the quantitative analysis model has carried out detailed crack damage risk identification for the submarine pipeline system,and identified the weak links of the system.Finally,the risk probability level of the basic event and the top event is obtained,further calculating probability significance index and critical importance index of the basic event,which provides a comprehensive and effective basis for the prevention of submarine pipeline crack damage risk.(3)Risk analysis of submarine pipeline system crack damage based on Bayesian network.As is known to all,the Bayesian network can calculate a more accurate posterior probability based on external information changes.Moreover,the Bayesian network structure is flexible,which can effectively use network nodes to express the accident scenario.It can update the calculation result according to the change of engineering condition.Based on the above advantages,this paper used the fault tree mapping method to transform the previous fault tree quantitative model into the Bayesian network model.Therefore,a more accurate and comprehensive risk analysis is carried out for the crack damage of submarine pipeline system under normal circumstances.Eventually,Bayesian network modeling and conditional probability deduction are used to build a case study of intermediate section of submarine pipeline.More importantly,good risk analysis results have been obtained in the risk analysis of specific cases of riser and safety zone sections,which also verified the applicability and effectiveness of the Bayesian network model.