A DECISION MAKING METHOD OF PIPELINE RISK ASSESSMENT

The pipeline risk assessment has been more and more widely used in the industry because of economic factors and regulatory requirements. The three most popular risk assessment methods are qualitative method (simple decision making matrix method), semi-quantitative method (score index method) and quantitative method. The decision-making matrix method greatly depends on expert's opinion, and does not provide much information to optimize the mitigation program. The quantitative method provides details of mitigation options, mitigation criteria, and prioritizations, but requires a lot of input data that the pipeline operators usually do not have. The score index risk assessment is widely used in the pipeline industry. The input data is relatively easy to acquire. The method provides details of mitigation options and relative risk values. The score index risk assessment is a relative method. Upstream pipeline operators often have questions, such as "Which is the most effective mitigation option to use with my limited resources?" and how the index scores relate with the actual failure frequencies and failure consequence. In order to effectively answer these questions, this paper outlines a method to correlate the probability of failure score with actual failure probability, and leak impact factor score with actual failure consequence in monetary units. Rather than using the final risk score, this method applies the monetarily calibrated consequence factor to the probability of failure so that a normalized and calibrated risk in monetary unit is obtained. By comparing the cost of an estimated mitigation program, the decision can be made based on relative risk. This process is straightforward and practical for industrial application, especially for upstream companies where operators have limited resources to run an in-depth risk assessment. A case study is presented using this method based on upstream pipelines.