A flow assurance system includes an inner pipe disposed within an outer pipe to assure flow through the outer pipe. During installation and relative axial movement with the outer pipe, the inner pipe is nearly neutrally buoyant or fully neutrally buoyant in the fluids of the outer pipe and may extend...http://www.google.com.au/patents/US6772840?utm_source=gb-gplus-sharePatent US6772840 - Methods and apparatus for a subsea tie back
