Breakthrough in rubber hose technology for deep-water oil exploration

In shallow fields, a metal pipe on the seabed is used to take the oil from Floating Production Storage and Offloading (FPSO) vessels to shuttle tankers moored at floating single-point mooring buoys about two kilometers away. But in deepwater oilfields, a metal pipe connection of this type laid on the seabed would be prohibitively expensive. "In the first deepwater field in Angola, Total, one of the world's biggest oil companies, used a flexible steel pipe at about 300-500 meters below the surface," explains Jacques Cognard, Oil & Marine manager, Trelleborg Industrie. "But these pipes are extremely costly, which gave us the idea to develop Trelline, a flexible, reinforced rubber hose to provide this link instead," he explains.

Looking at the cost scenario, Trelline is an extremely competitive solution. “Its wider diameter requires less pumping pressure so the FPSO doesn’t need expensive booster pumps, saving up to USD 15 million,” says Cognard. “Engineers have also estimated even higher savings in terms of installation and maintenance costs,” he adds.

Due to its specific design, Trelline hoses are almost corrosion-free and rubber also offers high thermal insulation, thereby lowering the oil’s viscosity – another factor in reducing pressure.

Furthermore, the Trelline solution comes in 12-meter sections, which can be replaced singly if necessary, rather than replacing the entire length of metal pipe.
Trelline was developed and qualified in accordance with API 17K, a specification for rubber hose, in partnership with Single Buoy Moorings (SBM), the Monaco-based engineers who manufacture the floating buoys. SBM financed part of the qualification and engineering tests, and Trelleborg financed product development.

The first order was received in September 2005, to supply a major oil company operating in West Africa and production was completed in June 2006. Installation will be finished in October, and other projects are currently planned.

The benefits of Trelline are many: “We have an enhanced brand image, we learned a huge amount during the stringent FEA (finite element analysis) modeling and hose testing we had to do, and we have even developed Reeline, a new product based on similar technology for linking FPSOs to shuttle tankers in shallower water,” says Cognard. “We’re very optimistic about Trelline’s success.

It’s innovative but it’s based on proven technology. We’re being closely watched because, given the ease of installation and the potential savings, we will surely become the preferred solution,” he smiles.

Trelline’s composition
Trelline is composed of 12-meter reinforced flexible rubber hoses, bonded with steel rings and bolted together. The ends use an integrated bending stiffener to reinforce the flanges, which are completely covered by chloroprene rubber, and integrated internal and external gaskets to prevent contact between oil and seawater. The connecting steel bolts and nuts are covered and sealed with pressurized grease to prevent corrosion. The line’s end connections use a gimbal to eliminate excessive bending loads and to ensure the end connection hoses remain safely within their design limits.