Aberdeen-based Balmoral Offshore Engineering has launched a new drill riser buoyancy system that incorporates low drag vibration and suppression capabilities.
During the development process, wide-ranging computational fluid dynamics and fluent modeling was carried out by Balmoral, while comprehensive tank trials were undertaken by SINTEF Ocean to provide the information required for final product design.
Drill risers extend from the drilling vessel to the blowout preventer, with their primary function being the provision of fluid communications between the well and the vessel. Buoyancy modules fitted around the riser provide uplift while reducing the submerged weight of the joints. However, drilling risers are prone to potentially catastrophic motions caused by subsurface vortex-induced vibration (VIV) and drag.
Balmoral developed the Balmoral DuraFloat LDV and Balmoral DuraGuard LDV, integrated and retrofit VIV suppression solutions, respectively, to prevent such motion occurring in the ever-deeper waters encountered in oil exploration and production. Both products have patents pending.
“The new system offers optimum uplift while eliminating riser motion and high drag levels without compromising performance, safety or structural integrity,” Jim Milne, Chairman and Managing Director of Balmoral Group, said.
The LDV profile was inspired by the outer structure of a sea turtle’s upper shell, which has been sculpted to provide a highly efficient and low drag hydrodynamic structure.
Balmoral’s technical team simulated this natural structure by implementing biomimetic engineering resulting in a design that brings VIV and low drag performance to its products. The hex design eliminates the need for ancillary suppression equipment to be attached to the riser, offering significantly improved timings when running and removing drill stacks.
In addition, it is well known that reduced riser motion dramatically improves the fatigue performance of subsea equipment, which has further cost saving benefits by extending the service life of wellhead and conductor/casing equipment.
Balmoral DuraFloat LDV is an integral part of the riser buoyancy module that is moulded into the product during manufacture, while Balmoral DuraGuard LDV is a retrofit option that is applied to existing infrastructure.
Suitable for application on marine drilling and production risers, umbilicals, flowlines and power cables, the system offers an “improved operational envelope.”
Fraser Milne, Engineering and Projects Director at Balmoral Offshore Engineering, said, “Our new system will significantly reduce drag and load during riser deployment, recovery, disconnection and hang-off while offering a substantial reduction in VIV fatigue damage. It does all of this with a negligible loss of buoyancy over conventional modules and is fully compatible with existing riser handling and storage equipment. We are confident that we have a product that will save the industry hundreds of thousands of dollars over the years.”