Platelets® are small mechanical objects which can be injected into pressurised fluid conduits to seal and locate leaks. Previous applications of the technology have been focused on large-scale pipelines, however, this paper will describe a novel application of Platelets® to seal and locate leaks in small bore subsea umbilical lines. Leaks in these systems are particularly problematic because they are difficult to locate, and the eventual external egress of fluid may be some distance from the actual line failure due to the presence of additional outer sheath(s). The fundamental principle behind the technology is that the creation of a Platelet® seal, which is often effectively an instantaneous event, modifies the pressure and flow profiles in the line. From this initial insight several complementary approaches to leak location arise. The changes in flow and pressure may comprise both transient and steady state responses. It is therefore possible through remote pressure and flow monitoring to identify the instant of that change of state or, in some instances, the pressure transient. Additionally, through ?time of flight? measurements "again using remote monitoring" it is possible to locate the position of the seal and hence the leak to a high degree of accuracy. This paper will describe the theoretical background to these developments and go on to exhibit the outcomes from a series of tests on long umbilical lines. These tests include a successful ‘leak’ location on an 84-km-long umbilical, which had been achieved prior to its proposed subsea installation. In addition to the technology development itself the crucial issues of risk to infrastructure, hazard analysis and the establishment of the limits of the approach with regard to existing infrastructure and systems will each be considered.

Background-Platelet TechnologyTM

A PlateletTM is a discrete particle which is released into a pressurised pipe flow for the purpose of sealing a known or suspected leak. When a PlateletTM encounters the region of modified flow around a leak, fluid forces entrain it into the leak and hold it against the pipe wall; this facilitates sealing, and also marks the position of the leak for subsequent detection. Once entrained, a PlateletTM is held firmly in place by the pressure differential acting across it. Each PlateletTM that is released into the line has a certain probability of being entrained; statistical analysis carried out prior to deployment enables the optimum batch size to be selected to give the highest chance of a successful seal whilst keeping the volume of injected Platelets® to a minimum. Platelet Technology-takes a radically different approach to pipeline integrity in that it seals and then locates leaks in a single integrated process. Whereas conventional leak sealing techniques require direct access to the leak site, the elegance of Platelet TechnologyTMlies in its ability to be implemented remotely, mimicking the human body to work with the pressure in the line and seal from the inside. Crucially, Platelets® are best deployed when there is flow in the line; this means they can be introduced as part of a routine pipeline operation resulting in minimal disturbance to production.

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