The Magazine for Underwater Professionals
Changes in the subsea landscape
A strong audience of more than 40 people attended the Aberdeen Branch evening meeting entitled Changes in the Subsea Landscape and had the opportunity to hear three speakers discuss subsea project experience from the offshore renewable energy sector with both unique challenges and parallels to the oil and gas market.
The discussions ranged from the innovative approaches to wind farm foundations pioneered by Vattenfall; the challenges of construction and operations in tidal races; and an updating on inter-array trenching solutions.
Adam Ezzamel and Alistair Leighton of Vattenfall provided an interesting overview of the European Offshore Wind Development Centre (EOWDC) from cable challenges through to the innovative foundation designs. As a test bed project for advancing technologies in the offshore wind sector, 66kV cables, maximising turbine sizes and progressing alternative foundation structures are part Vattenfall’s remit for the EOWDC. For the foundations in particular the traditional approach to monopoles or jackets is compromised by a relatively shallow sandstone bedrock layer beneath the overlying sand offshore Blackdog, Aberdeen. This has required an innovative use of suction cans on granular seabeds for the offshore wind industry. It was stated that to date, there is only one turbine with suction cans anywhere in the globe.
Andy Hibler of James Fisher Offshore presented an in depth review of the construction challenges in tidal races, particularly the Meygen tidal array. With flow speeds up to 12m/s during the tidal cycle, non-reciprocal bearings of reverse tidal cycles and rocky seabeds, Andy painted a picture of construction vessels operating at the margins of DP capability, minimal ROV windows and cable stability concerns that required tenacity and engineering discipline to overcome. Andy shared key lessons from Meygen with interesting ideas of how to broaden operability windows in the future.
Kevin Robb provided an overview of the broadening of Global Marine Group capabilities through the acquisition of the Fugro Symphony to further expand on the cable lay and trenching capabilities within the Global Offshore business unit. Kevin provided an insight into Global’s track record in the offshore wind inter array cable market, key equipment capabilities and some of the differences compared to a typical oil and gas project such as multiple cable installs per development.
The evening provided a good overview of parallel industries from the experience of much of the audience and this was reinforced by the many probing questions during the Q&A sessions following each speaker which extended the evening.
The members of the North of England branch of the SUT gathered at Newcastle University on a cold March evening for the second evening meeting of 2018.
The evening began with an intriguing presentation from Craig Loughlin and Chris Turner representing the Marine Management Organisation (MMO), the executive non-departmental public body tasked with promoting economic growth while protecting the UK’s marine environment. Craig began by describing the role of the MMO. The body was formed as a result of the Marine and Coastal Access Act of 2009 and is responsible for planning, licensing and conservation alongside the management of EU funding from the European Maritime Fisheries Fund (EMFF). The area managed by the MMO extends from where a river becomes tidal to the median line (or 200 kilometres from the shoreline) and totals just over 230,000 square kilometres, which is approximately double the landmass of England.
The MMO is currently working to improve marine registration and its digital services. It is tasked to innovate and pioneer despite budget constraints and align itself with other Defra bodies. Craig followed on to explain that the long-term plan aligns with the recent government report A Green Future: Our 25-year Plan to Improve the Environment, a 151-page document detailing the current government plan to improve the environment over the next generation. He then mentioned the MMO’s work with overseas territories on what is known as the Blue Belt programme.
To finish his part of the presentation, he discussed a few of the MMO’s key achievements since the organisation’s inception including how the MMO was able to create and implement the first marine planning system. He also stated that there has been an improvement in fish stocks in recent times due to the MMO’s work and that it currently has 615 projects approved for funding by the EMFF. Craig then passed over to Chris to give some more detail into the work the MMO does with regards to marine licensing.
Initially, Chris explained to the group that marine licensing came in during an amalgamation of previous regimes in April of 2011 and defined that there are four types of marine licensing usually dealt with. These are: International, European, Domestic Primary and Domestic Secondary. He then moved to give details on scenarios in which marine licensing is required.
One of these he detailed was for construction. This category is quite extensive as it covers everything from more conventional developments in ports and marinas to the construction of coastal flood defence systems. Large coastal developments, such as bridges, and even art installations, also fall into this classification. He also explained how licensing is also required for the deposit or removal of any object from the marine environment and the scuttling or incineration of vessels and objects. Dredging also requires marine licensing to be acquired.
Chris then clarified that there are some situations in which a license is unnecessary. Typically, these are due to the assumption that the activity will cause little to no impact such as the use of small scientific instruments or for safety purposes such as fire fighting. One area that Chris highlighted involved the construction of coastally located nuclear facilities. Following the Fukushima Daiichi tsunami disaster in 2011, the development of nuclear facilities has involved the requirement to ensure protection of these facilities from such events in order to avoid a similar disaster in the future. Chris then identified the development of offshore renewable projects as another area within the energy sector that the MMO is responsible for licensing.
In order to provide an applicant with a license for any of the aforementioned marine operations, the MMO must access a wide range of information and review all relevant legislations. It may also consult with other Defra bodies where appropriate to the specific application at hand. The pair then opened the floor to questions. One question asked regarded the licensing required for offshore oil and gas operations. Craig then stipulated that the MMO is not responsible for the marine licensing for this application; however it is often used as a consulting body where appropriate expertise is required.
Following on from the MMO’s presentation, a presentation was given by Phil Pennington and Martin Joliffe from Osbit entitled ‘Introduction to Well Intervention and Osbit’s Well Intervention Equipment’. Phil began the talk by giving some background on the work often done by Osbit. He described how Osbit works on the design on manufacture of a range of bespoke offshore equipment including: offshore handling, access systems, trenching, testing and, the topic of this presentation, well intervention.
Well intervention, explained Phil, is the intervening in a well in order to maximise production capacity from aging assets or potentially decommissioning the asset if required. This involves accessing the well from a vessel to monitor the well and provide downhole feedback with the possibility of making repairs if necessary. The stimulation of the production of a well can also be achieved by using well intervention. Essentially, well intervention can be split into two categories: light intervention and heavy intervention. Light intervention tends to take place from a monohull or semi-submersible and tends to incur fewer costs. It can also be achieved either with or without the use of a riser. Heavy intervention on the other hand is far more expensive, generally taking place from a larger drilling rig and involves removal or heavy duty repair of the well using a riser-based system. Phil indicated that the focus of the rest of his presentation would lie with light intervention.
Three different types of line are used for well intervention; these are slickline, wireline (sometimes referred to as E-Line) and coiled tubing. These varieties range widely in complexity and cost. Phil began by describing the simplest of these; the slickline. The slickline requires few elements topside due to the low pulling forces possible and due to relying on gravity this line can only achieve limited depths. As a result this type of line is the least expensive and is used primarily for the deployment and retrieval of tools. The wireline is similar to the slickline but allows the transmission of electrical signals, allowing it to power tools and achieve greater depths than the standard slickline. This is the most common of the three lines detailed by Phil despite the fact that it has no ability for fluid control. The most expensive, coiled tubing, involves a seamless steel pipe spooled onto a reel and can be used to pump fluid in or out of the well. Due to this capability more control is required during use and a riser is necessary. He then mentioned that riser-less approaches are being investigated. A riser-less system would be cheaper as it requires less equipment, less time to build and does not require the use of a dedicated vessel. However, using a riser does allow for increased water depths.
Phil went on to describe that observing of the well using a wireline or a slickline tends to occur initially. Other potential well interventions can range from pumping and circulation or perforation using a controlled explosion to repairs or cement plugging and abandonment. The types of repair can involve the patching of a tube, the removal of scale build up and a process known as heavy duty fishing in which downhole assemblies can be recovered.
A case study of the Siem Helix 2 was then presented by Martin. The Siem Helix 2 is the second of two new-build vessels dedicated to use for well intervention. He detailed the key equipment that exists upon the Siem Helix 2 vessel which allows it to perform specialist well intervention tasks. This includes the multi-purpose tower (MPT), intervention tension frame (ITF) and maintenance frame as well as the moveable MoBo deck.
Recent work completed by Osbit in the field of well intervention involved the intervention riser system (IRS). In order to prevent the IRS acting as a pendulum, a cantilever system is used during the lowering through the moon pool. Martin explained that Osbit worked on a project to develop the design of the maintenance tower and moveable MoBo deck. The MoBo deck was required to have a 600-tonne capacity and would be positioned six metres above the moon pool. The deck itself would be able to slide allowing access to the IRS. This project was successfully completed and will be used on the Siem Helix vessels.