A Study On Risk Assessment Techniques Of The Submarine Pipeline System

As an important part of offshore oil and gas development system, submarine pipeline tends to be the most safe, fast and reliable mode of transportation for large and continuous transmission of oil and gas products. Compared with onshore pipeline, the submarine pipeline system affected by the complicated ocean environment, exists more complex and changeable potential safety hazard in the process of design, construction, operation and maintenance phase. Once accidents happened, it will cause a great structural damage, economic loss, environmental pollution and bad social influence. To predict the system potential hazard before the accident happened, it is so necessary to take the risk assessment for the submarine pipeline that effective measures can be applied to avoid the risky events, which is of great significance for ensuring the submarine pipeline operating safely and steadily.This thesis introduced the current risk assessment theories and methods which are composed of basic concepts, operating steps and characteristics. The features and application scopes were respectively contrasted and analyzed for the qualitative assessment, semi-quantitative assessment and quantitative assessment. Combined with the risk characteristics of submarine pipeline system, several methods suitable for pipeline risk assessment were discussed and emphasized in detail.The tremendous accident reports collected from the worldwide offshore oil and gas development projects, and the investigation results obtained from the related organizations in Euro, USA and UK about the submarine pipeline accidents, can preliminary definite the main risk factors of submarine pipeline system, and thereupon determine the proportion of each factor.Based on the aforementioned methods, it is necessary to get a scientific, comprehensive and detailed risk identification result for the submarine pipeline system. Taking example for the current pipe risk assessment models and combining with the particularities of various system structures and operating environments, this thesis established a submarine pipeline risk assessment index system given priority to damage from the third party, corrosion, natural factors and incorrect operation. And also, each index factor can be analyzed step by step.Coupled with the established submarine pipeline risk assessment index system, analytic hierarchy process (AHP) can be applied to determine the weight of each assessment factor and differentiate the classification standard. According to the above content, this study provides an integrated grey fuzzy comprehensive assessment model for the submarine pipeline system. For the case of Nanhai submarine pipeline, the above model can determine the risk standard and the failure consequence assessment for the pipeline system.