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Iv-Consult to play a major role in the decommissioning of offshore platforms
We currently face a major challenge: hundreds of oil and gas platforms in the North Sea will be reused or dismantled in the coming years. In the latter, better known as ‘decommissioning’, Iv-Consult aspires to use its experience to take initiative and responsibility in contributing to this enormous task. Structural Engineer Luuk Blekman has been involved with decommissioning projects for years and sees promising opportunities: “Decommissioning has only just begun and will continue in the coming years. So, there is potentially a substantial amount of work for us in and around the North Sea.”
First of all: what exactly is decommissioning, and why does it need to happen? Over the past decades, hundreds of offshore platforms have been placed in the North Sea around the Netherlands, the United Kingdom, Denmark and Norway to extract oil and gas and deliver it ashore. In the context of the energy transition and sustainability goals set out in the Paris Climate Agreement, the continuing use of these fossil fuels will be phased out further in the future. Hence, many of these platforms are therefore on the list to be dismantled. The dismantling of a platform entails removing the complete infrastructure and the topside and jacket. The owners of these platforms are responsible for the entire lifespan, including the decommissioning thereof. For Iv-consult, the careful dismantling of offshore structures involves the safe lifting and transportation of the topsides or jackets to the mainland, something in which Luuk Blekman has become specialised in the past three years. The process begins at a much earlier stage and involves research, offshore inspections, weight calculations, and determining the centre of gravity of the topside and jacket.
Luuk and several colleagues followed an offshore training to conduct physical surveys on platforms. As a result, Iv-Consult can now carry out offshore inspections on behalf of clients.
“This is a very nice part of our work,” says Luuk. “Without the possibility to perform offshore inspections, we would be working only in an office environment, which could result in people losing touch with the actuality. It is therefore very special as well as useful to perform these inspections. This is all part of the strategy to be fully prepared when a client requests us to go offshore in the future.”
The offshore inspections examine whether the actuality corresponds to the available drawings, reports, and photos. In addition, whether structural changes have occurred over the years and whether equipment has been added or removed is also checked. All of this information helps us to build a complete overview (as much as possible) of the platform before, among other things, the weight is determined, and the models for the lifting and transport analyses are drawn up.
However, much of the information is already collected in the preliminary phase at the office. This is a complicated puzzle, especially at the beginning of such a project. Luuk: “It’s a challenge to gather and organise all the information and ensure nothing is overlooked. Of course, we have set up a system to ensure we know how the information is recorded and where we need to focus. It’s really nice to devise a solution in this way. And compared to when we first began, we are already achieving this much faster. Our goal is to ensure that the reports we offer to clients are drawn up as uniformly as possible and are clear and easy to read.”
“In a later phase of the ‘removal engineering’, we determine whether a platform will remain intact during lifting and transportation. For example, should lifting points be applied? This is, of course, a question that must be answered,” Luuk continues. “We also design a structure, the grillage, to transport the platform. The topside and jacket are welded to the grillage and transported on a vessel. The grillage distributes the weight evenly and prevents damage to the vessel.” The welding part is essential for bringing a platform ashore in one piece. The forces released when transporting such giants can be considerable. An offshore platform can easily weigh 5000 tonnes (which would require more than a thousand HGVs), yet it is possible to transport this giant as a whole with the method and structures that Luuk and his colleagues devise.
Following transportation, the topside and jacket arrive at a decommissioning yard. There, Iv-Consult is often involved in the load-out analysis. At a decommissioning yard, such a platform is then cut into separate pieces and melted down, or the existing equipment is reused. “I think contributing to circularity is one of the best aspects of this work,” says Luuk. “The idea of taking something so huge out of the sea and finding a new use for it is fantastic. And the whole puzzle of achieving this is what completes the challenge. When platforms were placed, it was never taken into consideration in the design that these would also have to be removed. That’s evident. Much has often been added and lifting points removed. It was never a design requirement to make it possible to remove the platform. This is an element that will change from now onwards.”
Iv-Consult also focuses on decommissioning old monopiles. For months, they have been working on a new way to remove monopiles with minimal noise pollution quickly. Iv-Consult has devised a method whereby a
crane’s grab clamps around a monopile and creates some dents, enabling the crane to achieve an optimum grip by enfolding around the monopile and clamping. The monopile is then lifted out of the water. This method works quickly, relatively quietly and effectively.
This patented method will make a significant contribution to the careful dismantling of offshore structures. With regard to the tools and in-house specialist knowledge at Iv-Consult, Luuk is confident there is much to gain, both in the conducting of offshore surveys and the patented decommissioning method. “Decommissioning has only just begun and will continue in the coming years. There is potentially a substantial amount of work for us in and around the North Sea. We are currently building a strong track record.” •
