The Application Of Risk Based Inspection (RBI) In The Integrity Management Of Subsea Pipelines

China has rich offshore oil and gas resources. During the development of offshore oil and gas, the operational status of submarine pipeline is directly related to the safety production of offshore oil and gas fields. Now, many old pipelines have the accidents, which severely affect the pipeline transportation. Therefore, establishing a rational detection system to prevent the failure of subsea pipeline and ensure the pipeline integrity management has an important significance for oil and gas development in China.Traditional inspection program for subsea pipelines is in a fixed time, which has passivity, blindness and randomness. The establishment inspection plan of risk-based inspection is based on the pipeline risk analysis results, so it has initiative, definition and orderliness. This paper describes the application of risk-based inspection in subsea pipeline. At present, the software of risk-based inspection has been developed in oversea, for example, the ORBIT of Det Norske Veritas (DNV), RB.eye of Bureau Veritas (BV) and RiskWise of British Institute of Welding Technology (TWI). However, in our country, risk-based detection technology is just stay in theory and the capable of forming technology has not been reported up to now.ChapterⅡof this paper gives a detailed description of the theory of risk based inspection from the basic concept to the implementation steps. The processes of RBI include the RBI Initial Screening Assessment, RBI Initial Assessment and RBI detailed Assessment. The objective of Initial Screening is to exclude unrelated risks and identify potential failure modes based on experience; Initial Assessment is a qualitative analytical method which will be used to evaluate all of the pipeline failure modes; In order to further understand the status of pipeline operation and check whether the failure modes can cause the pipeline failure, the quantitative analysis method has been used in RBI detailed Assessment. In the every process of RBI, the probability of failure and consequence of failure are the most important steps.ChapterⅢgives a systematic analysis to the pipeline time-based damage cause including internal corrosion, external corrosion and internal erosion. The consequence of these three-damage causes is the wall thinning of the pipeline. In the RBI qualitative analysis, the detection time is determined according to the risk matrix and in the RBI quantitative analysis, the new pipeline defect should be calculated based on the corrosion rate and erosion rate, then the structure reliability assessment will be used to determine the failure probability which should be used to compare with the target reliability level, thus the detection time will be decided.Chapter IV studied the pipeline event-based damage causes including the pipeline free span, on-bottom stability and the third-party damage causes. The failure probability of event-based damage cause does not vary with time so cannot be predicted. In this case, the external conditions of the pipeline operation will be used to evaluate the failure probability and pipeline safety. In addition, relevant models should be established to assess whether accident can cause the pipeline failure.Finally, the Chapter V presents the achievement of this paper-the software of the RBI, which fills the gap of our country in this area. Meanwhile, i think the RBI theory should be applied to the submarine pipeline, which cannot be detected, and this is more meaningful.