As exploration moves into deeper water, the length of umbilicals and cables is increasing, requiring increased capacity reels. The largest reels are limited to a certain size to prevent compromising the safety of the vessel. Additionally, operators are seeking to reduce or minimize the number of subsea joints. Modular carousels offer operators another option in handling increased capacity reels.

Making the case for modular carousels

In late 2011, Aquatic Engineering & Construction Ltd., an Acteon company, investigated the commercial possibilities of building a 1,500-tonne modular carousel.

The business case was compiled through in-depth telephone research with leading oil and gas subcontractors as well as broader industry evaluation. It demonstrated that the 1,500-tonne carousel concept was positively received.

A high priority would be that using a modular carousel would require a decision made at an early stage of project planning; potential customers would need to consider the carousel “off plan.” Incorporating a modular carousel at a later stage of a project would be more challenging.

During 2013, Aquatic invested in the design, manufacture, test and operation of its modular 1500Te carousel. This would be the first truly modular carousel in the market. Other similar products that claim to be modular are cut and welded back together during mobilization. As a modular carousel, it would be much easier to take apart and ship in 12-m (40-ft) containers. Aquatic’s traditional powered reels have high utilization, and the new modular carousel aims to further serve and expand its market in an area where reels are no longer sufficient or optimal due to length and/or weight of umbilical, power line or flexible cables required.

Fast forward to 2014, and Aquatic’s modular carousel has successfully completed its first project.

Product design, mobilization

The 1500Te carousel can handle a product load up to 1,500 tonnes, has a maximum reeling speed of about 1 km/hr (0.62 mph) and uses a built-in tensioner with a maximum line pull of 5 tonnes to maintain product tension on the horizontal reel at all times. The tensioner is mounted on a level-wind tower, which ensures proper spooling on and off the carousel. It has a reel diameter of 12 m and a variable hub diameter, which means that it can handle multiple products and can be mobilized onto most vessels of opportunity.

“Our innovative 1500Te fully modular carousel solution has been designed to maximize product capacity, minimize vessel days and maintain operational efficiency in demanding marine installation projects,” Chris Brooks, president of Aquatic, said.

The carousel was successfully used to install 9.7 km (6 miles) of 8.5-in. diameter umbilical in the South Belut Field offshore Indonesia for ConocoPhillips. As the installation contractor, Kreuz Subsea engaged Aquatic Asia Pacific to mobilize the modular carousel system onto the Seamec Princess and transpool the umbilical prior to sailing to the field and laying off the vessel starboard side.

The project saw the Aquatic carousel mobilized for the first time after completing its factory acceptance test in Singapore. Logistically, the first offshore operation for the new carousel was more than sufficient to put it through its paces, requiring three different lengths of flexible product to be spooled onto the carousel at the start of mobilization. Each length was connected to the next using mid-section connectors, each 8 m (26 ft) long.

The Aquatic team met the challenges of this complex engineering operation, with representatives from Kreuz Subsea observing each stage. The entire operation from equipment mobilization to transpooling, offshore laying and demobilization was completed within three weeks.

“The 1500Te modular carousel is clearly a game-changer,” Brooks said. “Designed for the widest possible range of vessels, clients and project variations to maximize its potential future use worldwide, this necessitated specific design and commercial requirements. Based upon our first project and current proposals, the carousel will be mobilized less often than our smaller pieces of kit and will be out on longer projects each time it is used.”

Built for deepwater

Installation in deeper waters has become a recent trend in the subsea market, often being performed in depths ranging from 1,981 m to 3,048 m (6,500 ft to 10,000 ft). However, installation replacement or recovery work at this depth requires specialist equipment to accommodate the increasing length and weight of the items being installed. Aquatic’s carousel system provides the strength and stability that can withstand the installation of the heaviest equipment in deepwater.

The carousel’s capability and flexibility in all waters also are being proven on projects that demand increasingly long subsea tiebacks to processing platforms.

“It is not enough to have the right pieces of kit in the right places; customers expect this as a minimum,” he said. “Today, clients are ever more demanding and require a total package that combines favorable contract terms, available kit, flexible teams to work with and, overall, people who are interested in forging long-term business partnerships for mutual benefit, not just to win projects here and there.”

Future steps

According to Brooks, the company has established long-standing relationships with companies in both the Middle East/Africa and Asia-Pacific, and maintaining partnerships is at the heart of its strategy for the U.S.

“We understand that to do business anywhere, it’s not possible to merely wave credentials at people. It is vital that trust and cooperation are maintained over a number of projects and negotiations,” he said. “This doesn’t happen overnight, but when it does develop, it harvests long-term rewards built on mutual trust and benefit. By developing existing partner arrangements and creating new partnerships with key regional players, we aim to improve our current prospects and position the business to capture growth and deliver significant improvement.”