Cross-industry knowledge sharing improves mooring integrity

It has often been commented that the offshore hydrocarbon industry is particularly bad at sharing lessons learned – both with respect to successful solutions and what has proven to be more problematic. However, re-inventing the wheel is expensive. For safety critical systems, not learning from experience can repeatedly place personnel and infrastructure at risk. To avoid this, there is a need to improve knowledge transfer and distribution throughout the industry.

As the industry has moved toward deepwater and complex reservoirs, bottom founded, fixed steel, and concrete platforms of the past have been replaced by more flexible floating units held in place by compliant moorings. Although the chain, wires, and fiber ropes used to moor production and drilling units are strong, they also often have to operate in dynamic environments. Over time fatigue (tension, bending, and torsion), wear, and corrosion (including microbiological activity), all take their toll.

Hence, for example, any material inconsistencies, design approximations, or unexpected loading effects all can result in premature degradation and aging. In fact, engineering experience suggests we should not expect any mechanical system to withstand 20 or more years of field service life without inspection, repair, and maintenance.

Initially in the early 1990s it was expected that brand new bespoke mooring systems for floating production facilities would be much more reliable than those of drilling units, which can be damaged during their regular recovery and relay operations. Although permanent mooring systems have been more reliable than temporary mooring systems, in practice there still have been significant problems, some of which have occurred relatively early in the field life.

Because of this GL Noble Denton (formerly Noble Denton) launched a Joint Industry project (JIP) on Mooring Integrity in 2002 to try and identify the extent of the issues. This attracted 23 participants and reported at Offshore Technology Conference (OTC) in 2005. Following on from this work a Phase II JIP was launched in 2006 to try to tackle the most pressing issues. The Phase II JIP has attracted 38 participants with the principal findings having just been reported in May at OTC. This makes it one of the best supported JIPs in recent years.

Perhaps the most significant factor associated with the Mooring Integrity JIPs, from a pan industry perspective, has been the extent of information sharing at the twice yearly Steering Committee meetings held as part of the FPSO Forum/JIP Week (www.gl-nobledenton.com/fpsoforum or www.fpsoforum.com).

The JIP Steering Committee consists of operators, class societies, regulators, equipment providers, and service companies. Some of the participating companies are in direct competition with each other. However, despite these constraints, participants to the JIP have been prepared to share their experiences to the mutual benefit of the entire industry. For urgent issues that have implications for more than one production facility, this information exchange has included the use of safety bulletins distributed within the Steering Committee. As well as the actual attendees at the meetings there is a much larger virtual correspondents group who are kept informed about latest findings and contribute to the discussion process.

The Mooring Integrity JIPs have demonstrated the importance of a group of experts getting to know each other and regularly meeting up to review developments in their field of expertise. However, JIPs typically only run for a couple of years and once the particular subjects of interest are completed the group typically disbands. GL Noble Denton is currently reviewing the format of a typical JIP to see if a new structure can be established which will promote information sharing on a longer-term basis. If this can be established, it should help in some way to overcome the industry’s poor reputation for sharing information and by so doing help to improve safety.

Martin G. Brown
Consultant Naval Architect, GL Noble Denton

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