This paper discusses briefly some of the most vital performancecontrol loops for a subsea oil/water separation processes, a subsearaw seawater chlorination/injection plant, and a subsea compressionplant. Monitoring issues for a subsea separation plant:

  • The oil quality needs to be monitored (such that there is not toomuch water in it).

  • The water quality needs to be monitored (such that there is not toomuch oil and sand in it).

  • Sand may accumulate in the separator vessel, and ultimately fill itup such that it no longer operates properly. The sand deposition needsto be monitored, and the sand flushed out when necessary.

Monitoring issues for a subsea compression plant:

  • Liquid carryover from scrubber to compressor needs to be monitored

  • Solids build-up in scrubber need to be nmonitored Monitoring issues for a subsea seawater chlorination/injection plant:

  • Solids content in injection water

  • Live bacteria content in injection water

Monitoring issues for a subsea raw seawater injection plant:

  • Solids content in injection water

  • Bacteria content in injection water

The 6 main control loops discussed in this paper are thus:

  • . Separation Oil quality sensing and control

  • . Separation Water quality sensing and control

  • . Sand deposition sensing and control

  • . Liquid carry-over sensing and control

  • . Solids content monitoring and control in injection water

  • . Bacterial content monitoring and control in injection water

Sensing and mitigating options are discussed.

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