Soil Characterisation for Installing and Operating Deep-Water Pipelines

Deep-water developments rely on pipeline and riser systems to transfer hydrocarbon products to floating facilities or potentially longer tie-back pipelines to shallow water platforms/onshore facilities. Depending on the nature of the product and operational conditions, the pipeline and riser system design may need to consider a range of dynamic processes during operation such as (i) controlled lateral buckling of the pipeline in order to relieve excessive constrained axial forces induced by temperature and pressure changes in the system; (ii) the accumulation of pipeline axial displacement or ‘walking’; and (iii) evolution of the pipe-soil interaction at the riser seabed touchdown point due to the dynamic behaviour of the riser. Under these conditions, the reliable structural assessment of the pipeline system relies upon accurate assessment of the pipeline-soil interaction (PSI), from the initial lay embedment of the pipeline to the evolution of the lateral and axial response over the lifetime of the facilities. Accurate assessment of these PSI parameters requires adequate characterisation of the seabed topography, seabed processes (e.g. geohazards) and the soil properties. This paper proposes ways for efficient planning of the geophysical and geotechnical site investigation activities and subsequent soil element and physical model testing for the assessment of relevant PSI parameters in deep-water.