Submarine pipeline can be regarded as a system of complex technique, high safety requirement and severe environment, which makes it full of hazards from the initial design phase to the final operation. Considering the characteristics of the submarine pipeline, the risk assessment method should be a comprehensive approach that combines the theoretical analyses and the engineering experiences. In this paper, based on the failure analysis of the submarine pipeline, together with the risk assessment procedures and risk level classification, the risk of an existed gas transmission pipeline is evaluated.
Since the first submarine pipeline was laid by Brown & Root Company in Mexico of Gulf in 1954, the total length of all kinds of submarine pipelines has been increased to the order of 105km during the past several decades. Currently, submarine pipeline has played a very important role in the oil and gas transmission during the development of offshore oil and gas field. As for China, especially from 1980's to present, 47 oil and gas fields have been developed and 138 submarine pipelines have been laid in Bohai Bay, East China Sea and South China Sea. The total amount of pipelay has exceeded 4000km, which covers wide range of sea area and various kinds of scales. The submarine pipeline is full of hazards and encounters the high probability of failure from the initial design phase to the final operation, which is closely related to its rough environment. The operating pipeline in the sea is subjected to the loads of the combination of waves, currents, tides and corrosion, as well as the hazards of dropped objects and trawling. According to the MMS (Mineral Management Service) statistical data of failure events happened in Gulf of Mexico in 1967–1987, 690 accidents of submarine pipelines have occurred, averaged up to 35 annually.
