Study On Risk Assessment Technology Of Collapsible Loess Disaster In Pipeline

Nowadays more and more long-distance oil and gas pipelines cross large tracts of northwest China Loess Plateau region with the main oil and gas pipeline network gradually built. Due to the unique nature characteristics of Loess, Pipeline accidents triggered by loess geological disasters ascend year by year. A set of scientific risk evaluation method is proposed on the basis of mechanism of loess geological disasters, which leads to pipeline accidents. As a result, it is of significance to provide bases for oil and gas pipeline integrity management and protect the safety of operation in loess area.According to mechanism of collapsible loess disaster and results of the risk assessment technology of pipeline, the fault trees of pipeline in collapsible loess disasters failure are set up by the failure mode of long distance pipeline hazards. Through the qualitative analysis of the fault tree and calculation on the structure importance of bottom events, the main risk factors are identified and multi-level risk index system of collapsible loess leading to pipeline accidents is created. To establish semi quantitative model of the evaluation of pipeline collapsible loess disaster risk as well as standard of pipeline hazard risk grade by the risk matrix in API581. The problem, that evaluation index system of weights assigned is influenced by subjective, is solved by the improved analytic hierarchy process and fuzzy comprehensive evaluation technology. It not only complies with the international practice, but also conforms to our country national condition by setting up Pipeline failure consequence assessment model, which is made up of evaluation method of casualties, direct economic loss and the invisible loss. At last, the evaluation method is used in several typical collapsible loess disasters of west-east pipeline and results were consistent with actual condition.Risk assessment method strictly abides by the basic principle of pipeline risk assessment. A new approach is presented on basis of the weight distribution of index score, which reduces the subjective influence compared with the traditional pipeline semi quantitative risk assessment method. The results of this study can be widely used in the pipeline risk assessment caused by geological disasters.