Brazilian oil giant Petrobras has specified ultra-strong, lightweight Dyneema® fibers for a complete set of mooring ropes for a semi-submersible mobile offshore drilling unit (MODU).
Headquartered in Rio de Janeiro, Petrobras has substantial interests in deepwater exploration. Petrobras specifically asked for the ropes to be made with SK78 grade of UHMWPE (ultra-high molecular weight polyethylene) fibers from DSM Dyneema for its high strength at low-weight properties. SK78 grade fiber was developed specifically for this type of mooring application and although it has a proven track record of success in Asia, the US and European waters, the Petrobras order marks the first time they will be used for MODU mooring in Brazil.
Petrobras is expected to use eight mooring ropes made with Dyneema SK78 fiber on a MODU in its new pre-salt deepwater fields off the Southeastern coast of Brazil, site of one of the largest recent oil discoveries in the Western Hemisphere. Petrobras plans to start using the ropes around mid-year.
Petrobras has chosen to use ropes made with Dyneema over polyester because of the lower weight and greater ease of handling. Polyester ropes with the same mechanical properties weigh around three times as much and are almost twice as thick as ropes made with Dyneema. Steel ropes would weigh around seven times more than ropes made with Dyneema fiber. Ropes made with Dyneema fiber will allow Petrobras to moor the MODU more quickly, saving on equipment costs, as well as on support vessels, delivering lower operating costs and a positive return on the investment.
Furthermore, ropes made with Dyneema fiber take up half the space of those made with polyester. This is important because fewer resupply trips are required. Drilling locations in the pre-salt province are around 200km offshore, and rental rates for supply ships are high.
DSM Dyneema and Petrobras worked closely together for several years on this project from fiber specification to comprehensive testing.
“Petrobras tested the performance of SK78 grade from DSM Dyneema at both fiber level and in full-scale ropes,” says Jorn Boesten, offshore segment manager at DSM Dyneema. “They were particularly concerned about the creep properties, and the ropes made with Dyneema SK78 met all requirements,” he adds.
“We are delighted with this order as it is our first in the Brazilian market. Working with Petrobras, a pioneer in the use of synthetic ropes, has been a rewarding and stimulating experience for us, and we look forward to continuing this successful collaboration and developing more opportunities in South America,” says Boesten.