SeaTrack –Acoustic Communication and Tracking of Inline Inspection and Cleaning Tools From the Ocean’s Surface
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SeaTrack, an offshore acoustic pipeline pig location and tracking system developed by CDI of Tulsa, Oklahoma, brings modern communications capabilities and military grade positioning methodologies to inline inspection and cleaning tools. The SeaTrack system provides acoustic communications from inline tools through the use of Chordal Semaphores. Chordal Semaphores can be used by inline inspection or cleaning tools to transmit condition changes and status updates, as well to transfer small amounts of arbitrary digital information from inside of the pipeline to an acoustic receiver on a surface vessel safely, and without the need for expensive divers or ROVs. The acoustic pingers developed by CDI use Free Flooding Rings (FFRs) to send complex multi-frequency pings through the liquid medium of oil pipelines and into the surrounding water. The complex nature of the pings has inherent signal to noise ratio and power benefits, but also combats the problem of multipathing in the subsea environment which dramatically increases the reliability of the system over basic single-tone pings. The multi-tonal nature of SeaTrack’s pings allows for Doppler speed measurements to be calculated and the radial velocity of the pinger-equipped target to be known to within 1/3 of a knot, or about 0.5 meters per second. Using a technique developed by CDI called “Cooperative Target Motion Analysis” (CTMA), the SeaTrack system can be used from a surface vessel to resolve the location of a stationary asset such as a stuck pig. These solutions are presented to the operator of the system as GPS coordinates on the surface of the ocean below which their target lies. The system has the capability of dramatically reducing operation costs of offshore tracking and communications activities, while simultaneously increasing safety because divers or ROVs are not required for these essential activities.
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