Development of Fatigue Resistant Heavy Wall Riser Connectors for Deepwater HPHT Dry Tree Riser Systems

BP is currently looking at the next generation of dry tree development projects in the US Gulf of Mexico (GOM) deepwater operating region. Some HPHT wells call for the design of 15 ksi or greater riser systems with sour service requirements. Over the last 10 years, NACE compliant high strength steels (HSS) together with fatigue resistant threaded and coupled connectors have proved to be reliable technical solutions top tensioned riser (TTR). Today their light weight and increased performance capabilities enable cost effective dry tree systems for water depths up to 10,000 feet. In the frame of BP xHPHT development projects, the design and qualification of Heavy Wall Threaded and Coupled (T&C) riser connectors for TTR applications was launched. Comprehensive development programs were built, involving numerous design variations, Finite Element Analysis evaluation and optimization — including parametric studies —, followed by intensive full scale static and fatigue testing campaigns. Those developments benefited from the design and field running experience accumulated with previous TTR projects, where innovative fatigue enhancement techniques and premium fatigue compliant sealing devices were engineered. In addition, combined static, dynamic and corrosion testing of base material is being conducted to assess and qualify the fatigue resistance of HSS up to 140 ksi under those conditions. This paper will present results and conclusions from these developments and will report the performance levels reached by Heavy Wall High Pressure T&C riser connectors and the associated high strength base material. Forward work plans on riser connectors for xHPHT, SCR and flowlines will also be discussed.