Abstract
Last two decades have been marked by a significant evolution on the design of HP/HT subsea pipelines around the world. The HotPipe and SAFEBUCK JIPs can be seen as the first deepened developments in order to obtain safe design guidelines for subsea pipelines systems subjected to global buckling and walking behaviors. The adopted design approach have been to allow exposed pipeline buckles globally on seabed in a safe and controlled manner. Otherwise, the walking phenomenon has been in general mitigated constraining axial displacements by means of anchoring systems.
After several design and installation challenges concerning lateral buckling and pipeline walking behaviors, nowadays there is a significant amount of deepwater pipelines operating with buckle initiators (triggers) as well as walking mitigation devices in offshore Brazil. Oil and gas pipelines, short gathering lines and long export lines, installed by reeling and J-lay methods, in other words different kinds of subsea pipelines have operated on very soft clayey soils and have formed planned lateral buckles as well as rogue buckles.
This paper presents the main characteristics and design challenges of the deepwater pipelines subjected to the lateral buckling behavior, also highlighting mitigation measures to constrain the walking phenomenon of some pipelines. The relevant design results are highlighted as type and number of buckle triggers, buckle spacing, type and locations of walking mitigations. Envelopment of the main design parameters are mapped in order to identify some trends. Finally, survey images of operating pipelines are presented confirming behaviors predicted in the design phase.
