Fatigue evaluation of Drilling Risers for Harsh Environments and Ultra DeepwaterDevelopments to Allow Optimised Riser Life and Inspection Plans

摘要

Recent experiences with current drilling risers in harsh anddeepwater environments have identified shortcomings in thecurrent design standards, which require a closer review for thefuture. With recent improvements in analytical methods andbetter field data, it is now possible to develop a much moreaccurate understanding of riser performance than ever before.This improved insight into riser operating behaviour hashighlighted that current demands in environmental andoperating requirements are now taking the current riserdesigns to their limits and it is important to understand thoselimits to establish better margins on current operations and toimprove design standards to meet these demands in future.Particular areas of concern are:a) Current Design Standards for Low TemperatureOperations, in particular the dependence on API 16 Charpy VNotch Standards for riser toughness requirements.B) The requirements for fatigue assessment criteria inthe design standards and how it should be applied, to enableeffective inspection and maintenance programmes to beestablished.C) Assessment of different operating parameters, whichare not normally considered in design standards, but are nowhaving significant impact on the operability of the risers.D) How risers should be assessed for classificationpurposes taking into account the above concerns.The paper examines recent experiences in harshenvironment and deepwater riser operations, which hashighlighted these concerns and the limitations it has put on theoperations.Finally the paper concludes on recommendations forimprovements to the current industry standards to enablefurther discussion and to suggest areas for development inriser design, which may mitigate some of the current issues.