The role of the sea bottom characterization in ultra - deep water projects

摘要

The on-going field developments and pipeline construction in very deep waters – across the continental slope and into the abyssal plains - pose specific and new challenges ranging from material selection to layout design, from installation technology to overall project execution, to cope with conditions in which installation tolerances are an issue, corrective action and intervention works difficult and expensive, repair still un-attempted. A specific aspect of these challenges regards the proper characterization of the sea bottom, with the aim to: ? Cope with usually weak soil, with limited bearing capacity for structure’s foundation and weak frictional containment of lateral (stability, in-service buckling) and longitudinal (pipe walking) movement of pipelines; ? Grant overall long term safety of the field development, taking into account potential dynamic phenomena of the sea bottom (slope stability, mudflow, fault displacement, cyclic soil failure); ? Provide detailed description of bottom morphology, as an aid to installation, considering essentially unmanned operation, with limited fault tolerance and difficult error recovering. Real life examples from the Mediterranean Offshore, West Africa and Gulf of Mexico highlight how advanced geological and geotechnical characterization, adopted since the early phases of deep water projects, can lead to optimized design, reducing project overrun and installation contingences.