Measurement Technology NW (MTNW) has recently completed a contract to provide installation, calibration and commissioning on an eight-point mooring monitoring system for Frontier’s drill ship, Duchess, off the coast of Nigeria. The new running line tensiometer and LCI-90 mooring monitoring system provides visibility into line tensions which will support mooring and rig movement monitoring.
The Duchess is a 475 ft by 75 ft vessel which needs to stay centered over an offshore oil-well for months on end despite sea states and drilling activity. The MTNW Line Control Instrument (LCI) Mooring Solution allows the rig manager to keep rig positioning to within a very small tolerance for lateral movement. The goal for most rig managers is to maintain movement to within a 12 inch circle while drilling activity occurs. This is a .2% margin for error.
“Without knowing exactly where your anchors are and the tension in your mooring lines, the rig manager can’t accurately position the ship,” said Tom Rezanka, Director of the LCI division of MTNW. “With subsea pipelines crisscrossing the bottom of the ocean and dynamic sea states, mooring line monitoring becomes a necessary part of rig management for personnel and property safety.”
In a traditional mooring setup, if problems occur, the vessel operator will notice a sudden change in position and will attempt to rectify the situation before the ship drifts too far breaking the drill column. Essentially, the operators can only respond to problems after they have occurred, they have no reliable means of predicting them. With MTNW’s mooring line monitoring system, the user can ensure that the tension on the mooring lines is low enough that the anchors are not at risk of shifting while also being high enough to keep the vessel in place; thus minimizing the chances of an anchor slip. In addition to this functionality, MTNW’s system can also monitor the payout of the line which enables the operators to accurately place buoys (with accuracy better than 30cm) to lift the mooring lines over subsea cables and pipelines.
