Effective Improvements to Reliability Based Corrosion Management

Reliability methods have being adopted by oil and gas operators for integrity management decisions. These methods explicitly account for all relevant uncertainties and are designed to provide consistent safety. Consequently, a risk or reliability based approach is a very appropriate basis for decision making in the face of uncertainties. However, as in the effective use of any powerful methodology the sensitivities of the method to assumptions and limitations of applicability need to be well understood. This paper presents how improvements were made to reliability based integrity program by understanding its limitations and sensitivities. First the inputs that have the highest impact on the results were identified. These inputs are the most appropriate areas for improvement and data gathering. It is also very important to understand how the results are to be used and for what purpose. The results of this particular inline inspection based reliability assessment are used to make better excavation and repair decisions. A defect-based and joint-based decision making process is essential for determining with sufficient confidence if each defect and joint is in a safe condition. Consequently, the improvements are focused on discriminating between the myriad of defects found during an inline inspection run. Distinct field characteristics of corrosion growth are also taken into account in these improvements. The paper presents the implementation of effective area methods for future integrity probabilistic evaluations. It also describes the benefit of applying defect-specific growth rates. Finally, case studies are presented to demonstrate the effectiveness of the changes.Copyright © 2010 by ASME