Failures of mooring systems in offshore floating production are not easy to predict, but they do occur, and they will happen more often as infrastructure nears the end of design life.
"It is mission critical that we do the detective work up front on these ageing systems," according to Tony Hall, CEO of Welaptega Marine. "It’s imperative that we identify any phenomenon that could put a facility at risk of failure."
Hall, whose company specialises in risk-based mooring integrity verification, was speaking today to a group of offshore integrity experts attending a seminar on ageing infrastructure. It was convened by the Oil, Petrochemical and Energy Risk Association (OPERA).
"It’s not good enough to do the postmortem on a failure. That’s too late. We need to be on the lookout for deteriorative mechanisms that put the system at risk of failure so preventive action can be taken."
He said risk-based inspection must be guided by experience of mooring systems and industry best practice. This means looking for risky areas where a deteriorative phenomenon is known to have occurred before.
"Industry has already identified many of these phenomena through operational experience which has been captured in the Oil & Gas UK guidelines on mooring integrity management, and the various Joint Industry Projects on mooring integrity (JIP)."
He said it’s also important to identify other types of deterioration which may not have been associated with failure in the past but that could still lead to failure.
He pointed to mechanisms such as sulfate reducing bacteria, heavy wear and corrosion at the turret, and bird-caging of wire rope.
He said this issue is more important than ever now that offshore reservoirs are being extended for further oil and gas extraction. There is greater demand for older assets like FPSOs to function as tiebacks and gatherings.
Welaptega has built up an in-depth knowledge of moorings after 15 years in the subsea inspection industry. It has participated in industry JIPs and developed its own technologies to identify and quantify subsea damage caused by age-related deterioration and impact.