Scour propagation beneath a subsea pipeline in high and low energy environments

Bottom seated subsea pipelines resting on an erodible bed are subjected to scour and transport processes. These processes potentially undermine pipeline integrity by increasing free-span lengths and resulting in bending stresses. Making predictions of scour is fraught with challenges including: (1) determining when pipeline burial or lowering will occur; (2) unexpected obstacles to scour propagation (e.g. rocks); and, (3) varying incidence angles of fluid flow. Due to these challenges, pipeline surveys remain a key part of ongoing asset management. Field observations of phenomena such as self-burial and the impact of flow incidence angles and localized water velocities also help us characterize the subsea pipeline environment. The validation of empirical formulas through comparison to field data is essential for high-risk regions. For this investigation scour beneath a relatively deep and relatively shallow section of the Tasmanian Gas Pipeline in south-eastern Australia was examined. Our data were collected by an Autonomous Underwater Vehicle (AUV), a Remotely Operated Vehicle (ROV) and Acoustic Doppler Current Profiler (ADCP). tour findings suggest to refine empirical formulas to better explain the coupled effects of waves and currents. An improvement on these formulas may reduce the frequency of monitoring surveys required. AUV and ROV surveys are powerful resources to better inform decision making of these assets and better understand scour at individual sites.