Riser Instrumentation: Deep Water Drilling Campaign Results

During the 1982–1983 drilling campaign in the Mediterranean, two wells were drilled by the Discoverer Seven Seas in record water depths of 1714 m and 1252 m. The riser was equipped with instruments to measure tensions, moments and angles at points close to the extremities. Simultaneously ship motions and environmental conditions including current measurements at various depths were recorded by ELF AQUITAINE and I.F.P. A large quantity of data relating to riser behavior was gathered and recorded. The results available for publication include raw data relating to the evolution of current at different depths, long period lateral ship motion acting at the riser top end, induced by the dynamic positioning system. Simultaneous measurements of angles at extremities were recorded to confirm the validity of two-dimensional riser analysis. Measurements of riser parameters made with deliberately large ship excursions from the vertical, enabled the riser practical profile to be compared with the theoretical one. Measurements, made with the riser hung off in storm conditions, confirmed the existence of large dynamic tensions and enabled them to be compared with the theoretical values. Correlation of the fluctuation of cable tension with ship heave has led to practical values of tensioner stiffness.