VORTEX INDUCED VIBRATION MONITORING SYSTEM IN THE STEEL CATENARY RISER OF P-18 SEMI-SUBMERSIBLE PLATFORM

摘要

In 1998, Petrobras installed the first steel catenary riser on a P-18 semi-submersible platform, in Marlim Field, at 910 m water depth. It was decided to install a monitoring system to check the riser design methodology, including Vortex Induced Vibrations (VIV) Analysis. For VIV monitoring, the riser was instrumented with bottles with sophisticated accelerometers in different points, to measure accelerations at a rate of 2 Hz for 300 seconds every 3 hours. The other monitoring systems installed are the oceanographic buoy, to measure waves (height, period and direction), surface current (value and direction), wind, pressures, etc. and Acoustic Doppler Current Profiles (ADCP) to measure instantaneously the current (velocity and direction) along the water column. There is a positioning system (PETRONAV) consisting of GPS receiver with phase correction blended with inertial sensors by a Kalman Filter to measure platform precise absolute positions and movements. All these systems are synchronized to acquire data at the same period of time, to make possible the reanalysis with more reality. This paper describes the VIV monitoring system, including some eletronical system description and the methodology used to define the water depth of each bottle.