Improving subsea safety and efficiency
Published: 02 July, 2014
A specialist engineering design and development company serving the international marine, oil, gas and renewable energy industries, has introduced a new remotely operated lift and deployment system for large payload-carrying. ODEE reports.
Developed for companies involved in subsea operations, Deep Blue Engineering’s (UK) Shuttle Sub offers an efficient and cost-effective way to deploy heavy payloads - such as cables and umbilicals - to and from the seabed. It is used to install and retrieve equipment, lay cable and conduct salvage operations. Even when laden with a payload of 100 tonnes, the buoyant-controlled Shuttle Sub can float, dive, surface and maintain neutral buoyancy, so it is ideally suited for work being carried out in deepwater environments on – or near - the seabed.
Technological breakthrough
Deep Blue's long-term objectives for this technology are diverse. “The Shuttle Sub is essentially an remotely operated vehicle (ROV) in its own right, but it combines this with a transport function”, said David Webster, managing director of Deep Blue Engineering. He continued: “The vast majority of deployment operations are conducted from the surface, using ships with cranes, which has limitations. Shuttle Sub offers an alternative. Eighty percent of our planet is covered with water. In the future, offshore industries will migrate into the vast, deeper and more remote areas where there is currently no activity. Whether installing generating equipment, laying cables, mining, conducting exploration or salvage operations, the industry needs a safe, efficient transport capability - a delivery vehicle - and the Shuttle Sub fulfils that role.”
The company says it is the first lift and deployment system of its kind. It does not require an additional ROV to conduct visual monitoring or connector installation activities subsea. Instead, technicians on a support vessel carry out these tasks remotely. As with a conventional ROV, they monitor and control subsea activities via an umbilical between the Shuttle Sub and the vessel at the surface. Where the Shuttle Sub is said to be unique is that it is also the payload carrier, transferring deployment and retrieval tasks to the ROV. This provides optimum control and removes the need for lift line-based operations. It also removes the loads from cables and umbilicals during deployment when they are suspended between the vessel at the surface and the seabed. The Shuttle Sub performs all of the functions of a work class ROV, but is large enough to accommodate a payload that would normally be deployed or retrieved from a ship. In addition, deployment is very accurate when using the Shuttle Sub because equipment or cable can be placed into position as opposed to working with the lift line, which makes accurate positioning difficult.
Joint venture with umbilical manufacturer wanted
During the coming months, Deep Blue Engineering will submit the first Shuttle Sub to rigorous testing. The company is keen to form a joint venture with an umbilical manufacturer in order to fast track development through to commercialisation of the technology for cable and umbilical deployment. "An umbilical manufacturer with exclusive access to this technology will be capable of offering lighter weight umbilicals for deepwater applications, and steel tube flying leads that are tens of kilometres in length, with the potential for simultaneous deployment and trenching,” said Webster. “This will provide them with a major differentiator and massive advantage within the global market,” he added.
Many benefits, many applications
For those involved in subsea cable- and umbilical-laying, the Shuttle Sub offers considerable cost-savings. When deploying cables and umbilicals from the surface, they must be capable of supporting their own weight, as well as any end termination, which dictates major aspects of their specifications, significantly increasing production costs. But because they are not deployed at surface when using the Shuttle Sub, this is not a factor. By using lightweight, low-cost hardware and smaller support vessels for umbilical and cable deployment, costs are dramatically reduced.
This advantage also extends to maintaining installed equipment. For example, when a cable within an umbilical is suffering IR issues, it is relatively straightforward to install a single, new cable and create a bypass arrangement. In addition, periodic maintenance operations of, for example, subsea processing equipment is easier, with the Shuttle Sub providing a platform to work from, transporting replacement consumables, and retrieving the parts to be changed out. This is completed in a single operation.
Finally, in the event of a catastrophic subsea blowout or pipeline breach, heavy cutting and capping equipment can be swiftly deployed into deepwater for intervention purposes. This is especially important because it is currently not possible to 'fly' this special equipment from a remotely positioned rig or vessel. The central environmental benefit lies in the system’s ability to facilitate intervention in deepwater remotely, allowing complex operations, such as sealing pipelines or damaged, uncontrolled subsea wells.
How it works
The Shuttle Sub, which will be available in two sizes, has a payload capacity of 50 tonnes and 100 tonnes. The vehicle itself weighs slightly less than its payload capacity, and uses a “cartridge-based” carrying system similar to the container method used in the shipping industry. A crane mounted on the support vessel lifts the empty Shuttle Sub into the sea, followed by the payload cartridge, which is lowered into the Shuttle Sub. Different cartridges are designed for different applications. For example, cartridge variants currently include a reel for laying cable, a drum for deploying long steel tube flying leads, and lifting equipment for salvage operations. Future plans include the intervention and capping capability, and a cartridge with a subsea drilling capability. The current design can be deployed in water depths to 1500 metres. Deep Blue plans to develop a Shuttle Sub capable of working at 3000 metres, followed by greater depths in the future.
The first set of wet trials will take place in Quarter 4 2014. Deep Blue will use a reduced scale Shuttle Sub prototype. Even so, the prototype has a payload capacity of four tonnes, and is one of the largest ROVs in the world.
