Oil Platform Monitoring

Posted on December 5th, 2016 by vapro Oil Platform Monitoring - RefTek

The vibration activity monitor is a relatively simple hardware and software system designed to provide updated predictions of the fatigue-loading activity in the jacket major-member welds of offshore oil platforms. Positioned on the platform cellar deck, the vibration recorder measures platform deck motion with two orthogonal accelerometers. These motions are processed in real-time to provide continuous records of the direction and frequency of platform motion. The recorded data is combined with transfer functions from a finite element structural model, which may be the platform design model or a refined version thereof, in order to predict and rank the fatigue activity in the joints. These predictions are used:

  1. To verify and refine the platform design fatigue analysis
  2. To focus on areas where unanticipated fatigue activity has been observed
  3. To help select the welds for detailed underwater inspection.

This type of monitoring system could be installed on jackets, jack-ups, FPSOs, concrete platforms, offshore wind turbines / farms, offset risers, and pipelines.

In seismic areas that could be affected by hurricanes, a strong motion system is required. It should have three component sensors at the free field in the ocean bottom deployed about 100 meters away from the center of the platform.

The response of the structure to influences, such as the environmental loading or structural modification, can provide important information to assist in the verification of the design, assure long-term structural integrity and improve the operating parameters for the structure. The information gained will provide the opportunity for significant cost savings, maximized operating window (with substantial economic benefits), increased safety, minimized fatigue on critical elements, and improved understanding of the platform behavior.

The structural monitoring provides the following range of services to the Offshore Industry:

  • Design verification
  • Installation control
  • Structural integrity
  • Riser Monitoring
  • Noise and Vibration
  • Collision detection
  • Tow monitoring
  • Vessel performance monitoring
  • Platform Monitoring
  • Instrumentation solutions for Wind Farms

The central data acquisition unit should have enough channels to record the accelerometers and several additional channels to record other sensors such as:

  • Tilting and inclinometers to monitor the overall structure.
  • Strain gauges located in the legs to monitor leg and overall structure loads and weight distribution.
  • Relative motion monitoring system allows the motion of a jacket and cantilevered drilling jack up platform to be compared with allowable limits.
  • Tides and ocean waves-height, measuring the air-gap measurements using a radar-based wave height sensor.
  • Meteorological data (wind speed, wind direction, barometric pressure, temperature and humidity).
  • Integrity monitoring for free standing risers.

Significant changes to the platform’s structural integrity could be detected by monitoring its natural frequencies and comparing the response characteristics to agreed upon criteria. With this data it will be possible to:

  • Reduce in frequency the periodic sub-sea inspection.
  • Assess platforms following a hurricane.
  • This allows the operator to prioritize remedial actions when resources are at a premium. A platform fitted with OLM can quickly be assessed and brought back into production.
  • Reduce the time at risk of a failed member, minimizing the probability of catastrophic failure.
  • Monitor systems installed on offshore facilities, especially those requiring extension of operating life.
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