Wolfgang Wandl
Viking Moorings
Faced with deeper, more remote, and more complex installations, the global offshore mooring industry confronts significant logistical, cost, and safety challenges. A key driver behind this is the increase in exploration activity and growth in subsea installations.
The North Sea, for example, is seeing steady activity. According to the Norwegian Petroleum Directorate (NPD), for example, 2009 saw the completion of 72 exploration wells. And this increase is mirrored on the UK continental shelf, where the recent licensing round in June 2010 saw bids for 356 blocks, the largest number since the first licensing round in 1964.
Further afield, exploration and subsea activities are on the rise in West Africa, driven by increased deepwater activity. According to industry analysts Douglas Westwood, the African subsea market is growing faster than all other regions of the world with subsea expenditure expected to increase by 16% from 2008 to 2012 when spend will equal just over $11 billion.
What does this mean to today’s offshore mooring sector?
There are a number of challenges.
Firstly, there is cost. Operators face increased pressure to manage costs and every day a rig is in transport is day of lost drilling. It has never been more important for mooring operators to move and secure rigs quickly and seamlessly – a challenge in remote and deepwater installations. Furthermore, the fact that anchor handling vessels (AHVs) can cost up to $400,000 a day helps focus the operators’ and rig contractors’ minds even more.
Linked to this is the need for operators to access the latest in offshore mooring equipment, wherever they are in the world, with less transportation cost and faster mobilization.
A second challenge is the increased complexity of mooring operations. With the scale of subsea deepwater infrastructure, as seen in Africa or the mature fields of the Norwegian continental shelf, where many newer operations are operating alongside older infrastructure, mooring providers have to work near existing subsea facilities and pipelines.
Finally, there are the different regulatory environments mooring providers must operate in. While these vary substantially around the world, it is essential that mooring providers put safety as a key focus.
Visualizing anchor positioning with real-time data.
What are mooring providers doing to meet these challenges? Do the latest offerings and innovations meet operator demands?
Reducing cost
With cost such a key driver, today’s operator needs to tap into a comprehensive portfolio of mooring equipment – in effect they need access to a total mooring solution.
These should include everything from ultra high-holding power (UHHP) anchors to the best in buoyancy units and mooring chains, synthetic fiber mooring rope, and other value-added services, such as crane wire.
For the latter, Viking Moorings partners with an Italian company that built the world’s largest wire closing machine. These kinds of developments are essential in today’s offshore mooring sector with operators exploring in deeper waters and using heavier equipment.
There is also an increased emphasis on renting such equipment. Benefits include no unnecessary capex, costs limited to the project’s duration, increased flexibility, and no equipment management issues such as storage, maintenance and certification, and no capital locked into depreciating and rarely used equipment.
In addition, the advantages of being able to access this equipment at strategic locations throughout the world is a big value-add feature to operators with reduced mobilization and demobilization time and lower transportation costs.
For example, Viking has storage in Alexandria, Egypt, where stocks of anchors, buoys, chains, and wire rope slings can be shipped immediately to offshore exploration areas, such as the Gulf of Suez, for a recent contract with Rashid Petroleum Co. (Rashpetco).
Viking also has a hub in Malta serving the central and western Mediterranean and the markets of Libya, Algeria and Tunisia and, further south, Viking Moorings set up a base in Takoradi, Ghana, as a stepping stone to deployments off the coast of West Africa from Angola, Nigeria, and Ghana through to other regions, such as the Ivory Coast.
Flexibility in different solutions for different regions is important. In Australia, Viking introduced to the region new methods such as fiber ropes for mooring semisubmersible rigs. New ways to make optimum use of anchor handling vessels is another example since many of the boats in Australian today are relatively small.
Speeding up mooring
As mentioned, improving and speeding up how mooring activities are done reduces costs. There have been a number of developments in mooring to address this – some successful and some not.
For example, there has been an increased focus on dynamic positioned rigs for deeper and more remote locations with the perceived benefits being greater flexibility and no need for mooring anchors.
The downside is the cost to operate the rigs (the logistics of fuel supply, for example), and the computer-controlled thruster which can consume as much as 150,000 l (39,626 gal) of diesel per day with the resulting NOx and CO2 taxes. Their inability to operate in shallower waters due to regulations over the angle of risers (no more than 1.5°) means many DP rigs end up being moored anyway.
This introduction of “smart” anchors will revolutionize mooring, providing accurate and real-time data from the anchor point for the first time.
Anchor handling can be 10% of the total cost of a offshore exploration well, with challenges including deepwater beds and, on occasion, soil instability. With this in mind, Viking and Vryhof Anchors partner to use the new Stevtrack Anchor Data Acquisition System. The new system monitors and visualizes the anchor’s behaviour during installation, embedment, and final penetration. A transponder unit on the anchor communicates with a setback monitor on the AHV, displaying real-time data on variables such as roll, pitch, drag length, penetration depth and pull-in force.
The system confirms when the anchor is positioned correctly on the seabed and avoids the need to reset anchors, saving time and money. Such a system is particularly applicable to harsh, offshore conditions, such as in the North Sea.
Anchor retrieval is equally important. For instance, a buoy that, when submerged, can be brought to the surface using a coded acoustic signal which releases the buoy. The buoy will then be forced to rotate, paying out rope connected to the rest of the mooring line.
This greater control over anchor installation and retrieval not only improves efficiencies and saves costs, but also reduces the danger of damaging subsea infrastructure, such as pipelines and other obstructions, with a reduced need for grapnels to retrieve chain and wire.
Viking Moorings is deploying the QS connector, a new connection device to improve safety during mobilization and demobilization through automated wire line connections. The QS connector has just been deployed for the first time in the North Sea.
Rise of pre-set mooring
Another important development in offshore mooring operations today is the rise in popularity of pre-set mooring.
Benefits of pre-set mooring include greater precision and control over positioning the mooring around existing infrastructure, and reduced costs with few AHVs required and less risk of AHVs being stuck in bad weather at a cost of $400,000/day. Pre-set moorings can be placed months in advance of the rig arrival when weather is likely to be more favorable. There is also the cost to hire the rigs, typically between $300,000 and $500,000/day. When service company costs are included, these can costs can rise even higher.
Pre-laid mooring line must meet industry codes, pass buoyancy analysis, and the positioning of AHVs to fully embed or “break out” anchors must be calculated. In all these instances – whether pre-set or not – detailed mooring analysis is essential with Quasistatic or Dynamic Analyses applied to minimize rig offsets and line tensions.
An example of a pre-laid mooring solution is Noble Drilling’sHomer Ferrington semisubmersible drilling rig in the Baobab oil field off the Ivory Coast. The pre-laid system reduced risk and resulted in greater confidence in the drilling program.
In this case, the client asked to be quoted two different mooring systems 1,000 m (3,281 ft) apart, with the AHVs required to go back and forth in establishing the mooring. Other challenges included significant differences in water depth between the shallowest and deepest anchors, as well an uneven depth in the soft soils. Risks included tensioning the anchors and increased uplift mooring forces as well as concerns over potential rig move delays.
A pre-set mooring solution where the anchors would be placed around the drilling area so the rig could skid between the two drill centers. The mooring system was switched from a catenary system using mooring wire to a taut system using synthetic fiber ropes and vertical loaded anchors.
The result was reduced rig move time and improved mooring performance with less riser downtime and less drilling interruption. In addition, no AHT was required so a platform supply vessel (PSV) was used for significant savings. The client confirmed that the final savings were up to $85 million over the duration of the project.
Focus on safety
Another key issue in offshore mooring is safety. With the 2007Bourbon Dolphin tragedy in mind, where the AHV capsized off Scotland’s Shetland coast raised questions about the vessel’s ability to handle large anchors in deep waters, today’s mooring providers must address the issue of safety at every corner.
For example, Viking is in discussion with Smart Installations, about its ControlCutter, a device that cuts chain in less than three seconds. This kind of solutions will ensure anchor chains are cut immediately in the future, should the need arise.
As challenges in the offshore mooring sector increases, it’s encouraging to see that mooring providers are rising to the challenge.
Offshore Articles Archives
View Oil and Gas Articles on PennEnergy.com
