Risk-based Assessment Technology For Submarine Pipeline

With the development of the society, marine oil and gas fields, as a huge energy source, has becomethe focus of global attention due to the increase demand of energy all over the world. China NationalOffshore Oil Corporation has built252submarine pipelines with the total length of5000km since1985,including37pipelines beyond their design life. As a result of the distinctiveness of ocean environment,submarine pipeline will suffer all kinds of load, environmental erosion, material aging, mutation effects, etc.unavoidably during its service time, these damage accumulation and resistance attenuation of pipeline maycause enormous financial loss and irreversible damage to the ocean environment. Therefore, the security ofsubmarine pipeline has become a very important issue for development and production of marine oil andgas fields.This paper is based on project “Pipeline baseline management research and application” of CNOOC,taking risk assessment as technical route, carrying on the risk identification of Chinese submarine pipelineaccording to the survey of domestic and overseas submarine pipeline incidents, and then build a integratedfault tree. Through the qualitative and quantitative analys is of the fault tree, the main influence factors ofsubmarine pipeline system can be concluded as follows: corrosion, free span and third-party damage.Then according to the result of fault tree analysis and study on domestic and overseas submarinepipeline safety evaluation standards, taking three main influence factors into consideration, summarize akind of safety assessment method which is suitable for Chinese submarine pipeline system. Next, put themethod into practice. From the assessment results, Xijiang24-3submarine pipeline is slightly corroded,whose residual strength belongs to safety range and residual life is comparatively long. Situation isdifferent for Dongfang1-1submarine pipeline, which has many free spans because of the complex andvolatile ocean environment, the assessment results show that the free spans over17meters need to bemodified immediately.Finally, based on the semi-quantitative risk assessment theory and Chinese submarine pipeline currentsituation, a set of qualitative risk assessment is summarized and put into four submarine pipelines from CNOOC. The result shows that CEP-LP28’’ and DF1-1natural gas pipeline are ranked as high level riskwhich need more attention. Then some suggestions are given according to the risk assessment results.