Mooring operations meet asset integrity challenges

Achieving consistent mooring integrity requires operational experience, a focus on innovation, systematic processes, a close and advanced supply chain, global reach, and flexibility for different markets.

Mooring operations today are rising to meet these considerable challenges.

Today’s hurdles
Since the 1990s, there has been an increasing focus on deeper and more remote discoveries. The recent focus on deepwater basins, such as the Santos Basin offshore Brazil and a number of fields offshore Ghana, indicate requirements for remote and deepwater mooring of exploratory drilling rigs are here to stay.

Another challenge is the complexity of subsea production systems that mooring providers must work around – often due to many exploration activities taking place around fields that currently are in production, the North Sea being particularly congested.

Whether it is extensive pipeline networks, subsea tiebacks, water or gas injection wells, or multiphase pumping and subsea separation systems, complex seabed infrastructure poses considerable challenges.

A third less tangible challenge is the increasing need for operators to manage costs. Every day a rig is not connected to its mooring lines is a day lost drilling. Mooring providers need to move rigs quickly and seamlessly while guaranteeing asset integrity and ensuring safety is not compromised.

AHC cranes and the accompanying crane wire are vital to mooring integrity. (Images courtesy of Viking Moorings)

Through a combination of new technology-led solutions and a systematic focus on more traditional forms of protecting assets, mooring providers are taking on these challenges, delivering to operators and rig owners assurances for the structural integrity of offshore facilities and equipment.

Automation growth, real-time data
One key development in asset integrity is the growth in automation and realtime data in mooring operations.

Take the difficult task of laying anchors. Few people can forget the Bourbon Dolphin tragedy in 2007 when an anchor-handling tug supply vessel capsized off the coast of Scotland. The accident report found that the vessel was not equipped to deal with the bollard pull, thruster capacity, powerful winches, big drums, and equipment for handling chain, which anchor-handling demands.

Today there is considerable real-time information available to influence decision-making for mooring providers laying anchors. For example, in September 2010, Viking Mooring was able to conduct the first test on a new prototype product being developed jointly with Vryhof Anchors. The product, called the Stevtrack Anchor Data Acquisition System, was tested in the presence of the Norwegian Maritime Directorate, the Petroleum Safety Authority, and partners such as Det Norske Veritas (DNV).

The system provides a real-time view of the anchor installation process underwater where a transponder unit on the anchor communicates with a control module on the anchor-handling vessel, displaying real-time data on roll, pitch, water depth, and pull-in force.

The system allows the anchor to be positioned correctly on the seabed before force is applied to penetrate the anchor into the seabed. This removes the need for ROV inspection and avoids problems that occur when anchors need to be reset, alleviating the risks to existing infrastructure and saving both time and money. The result is greater control over the anchor laying process and enhanced asset integrity.

Another example of automation is in the mobilization and demobilization of rigs at times when assets are particularly vulnerable. Viking has developed a new connection device to improve safety during mobilization and demobilization through a series of automated wireline connections.

The Quick Safe Connector (QSC) connects piggyback, chaser wire, and pennant wire. Connection and disconnection are carried out in a deck cradle supported by a hydraulically driven manipulator tool with all operations controlled from the vessel control room. The tool consists of two halfshells, with the shells clamping around two QSC sockets to make a safe wire connection.

The connection tool also can support preset mooring solutions – another advance in mooring that can meet asset integrity demands. Benefits include greater precision and control over the positioning of the mooring solutions around existing infrastructure, the ability to carry out anchor laying operations when conditions are most favorable, and faster and more seamless transitions for drilling rigs.

Material innovations, inspections
A more traditional form of asset integrity is the innovation in material selection for key components of mooring operations.

Mooring ropes, for example, have seen considerable advances over the last few years, with synthetic rope now prevalent alongside steel rope. These developments have been facilitated by new standards such as the steel wire rope mooring standard set by DNV in 2009. Such standards are vital to operators as they look to comply with market requirements in systems design, materials, product quality, certification requirements, and fabrication.

Active heave compensated (AHC) cranes and the accompanying crane wire used specifically for installing subsea systems wire also are vital – especially in deep water. One of Viking’s key partners is Redaelli, an Italian-based company that has built the world’s largest wire-closing machine, able to produce wire at up to 550 metric tons and 175 mm diameter with a breaking strength of 2,400 metric tons. In March 2010, Redaelli manufactured the heaviest steel wire rope in the world.

Chain inspection services are critical both to mooring safety and to ensuring the integrity of offshore assets.

What also is essential to asset integrity is the constant vigilance and maintenance of existing equipment to counter the accumulated effects of wear and corrosion.

Chain inspection services, for example, are vital and require a rigorous and meticulous process. This consists of a visual inspection with the chain flaked on the quayside and where the level of loose studs can be determined; ultrahigh- pressure water jetting to bring the chain back to a recognized standard for magnetic particle inspection, the process for detecting surface and subsurface discontinuities in ferrous materials; and the fitting of horizontal and vertical presses to allow for most studs to be pressed into position. Only at this point can detailed inspections be carried out with a specially designed chain inspection and repair unit that can be mobilized within hours.

Close supply chain, global reach
Two other important drivers in asset integrity are a secure supply chain with a global reach.

Partnering with leading providers of mooring equipment is critical. Viking has partnered with Norwegian company Spin AS, using Spin’s acoustic-based SPIN technology and applying it to the anchor retrieval process, where buoys connected to mooring lines can be brought to the surface using a coded acoustic signal. The company is in discussion with another Norwegian company, Smart Installations, about the ControlCutter device that can cut chain in less than three seconds.

Gone are the days where mooring providers can coordinate operations thousands of nautical miles from their main hubs. Asset integrity requires onsite local support to react to challenges as they occur and to source additional equipment when needed. To this end, Viking recently has expanded its network with hubs and equipment bases in Aberdeen, Stavanger, Malta, Cape Town, Egypt, Ghana, Singapore, Perth, and soon in Brazil.