Undersea Oil And Gas Pipeline System Risk Assessment Study

Pipelines risk assessment technology is developed abroad firstly in seventies of last century and has strong practicality and pertinence. It is only more than tens years from the technology has introduced in our country, but it has actually aroused the widespread interest and widely applied in the pipelines of on land and has obtains certain theory achievement and economic efficiency. But it is relatively backwardness in the application of oceanic oil and gas pipelines that has been playing a more and more important role in the national economy, until now it haven't a systemic appraisal technology. So, to develop a set of risk assessment technology which aimed at the actual conditions and the specific environments of oceanic oil and gas piping system in our country is the main content of this article.With the fundamental thought and processing method of pipeline risk assessment technology overseas, unifying the actual situation in design, construction and runing, and following the technical standard and security specifications of the oceanic pipelines in our country, using the possibility analysis of the pipeline accident that caused by the environment which the pipeline passes through, the fault tree of oceanic oil and gas piping system have been established in this article. Then the qualitative and quantitative analysis to the fault tree have been carried on. With the hybrid approach employing fuzzy set evaluation and subjective estimation, the probability, the probability importance and the criticality importance of the basic events of the fault tree are determined, the failure probability of the top events is calculated too, and so the weak section of the system can be easily found out.With the analysis and the risk identification in the fault tree, the factor system of the oceanic oil and gas pipelines has been established. In the course of the establishment, some certain amendment to the general international system model have been carried on, add the natural environment influence factor in level of targets items mainly for the prominent influence of marine environment to the pipelines. Simultaneously considering the influence of the accident to the marine environment, the environment model has been chosen in the accident consequence assessment. Different factor is certainly dissimilar influence to the risk of the pipelines, namely the weights are different, so, some adjustment have been carried on using the analytical hierarchy process to the weight of all levels of influences factor based on the statistical data and actual condition of oceanic pipelines in our country.Because of the particularity of the environment in which the oceanic pipelines locates, it is very difficult and even impossible to observe and survey to the pipelines unless the diver or the life appliance stand by. Therefore, it is inevitable that there are more fuzziness and uncertainty in the course comparing with the land pipelines, in addition, the development of oceanic pipelines is compare late, each kind of statistical data is lacks and cannot form rules, therefore, the multilevel fuzzy comprehensive evaluation that unifies the EST and the fuzzy mathematics has been applied in this paper to evaluate the oceanic oil and gas pipelines in order to make it more scientific and objective.Finally, the risk rank of the appraisal result has been classified, and the acceptable risk criterion and risk control measures have been discussed in this paper. Some alleviating measure to reduced or evade the risk have been proposed. With all the studies above, "the risk assessment software for oceanic oil and gas pipelines system" have been finished to enhance the efficiency and the accuracy of the evaluation.