Drill riser buoyancy

Balmoral drill riser buoyancy modules

Drill riser buoyancy provides uplift while reducing the submerged weight of the riser joints. This helps to minimise top tension and prevent stress in the riser as well as reducing loadings during deployment and retrieval of the blow-out preventer (BOP) stack.

Drilling risers extend from the BOP to the drilling vessel with their primary function being the provision of fluid communications between the well and the vessel while supporting choke, kill and auxiliary lines. Balmoral Offshore Engineering consistently manufactures high quality modules while its in-house hyperbaric test centre offers test facilities to 7000msw equivalent.

Dressed drill riser buoyancy joint

Dressed drill riser buoyancy joint

Balmoral drilling riser buoyancy modules are fitted around the riser with moulded apertures accommodating auxiliary lines and riser clamps.

The vertical lift of the syntactic modules is transferred to the riser by a thrust collar fitted to the riser pipe below the upper coupling. A matching collar is normally installed at the lower end of the assembly to facilitate the transfer of the module weight during handling.

DuraFloat® and DuraFloat RIS™ (Residual Integrity System)

Drill riser buoyancy up to 12000ft

The demands placed on drilling riser buoyancy have increased dramatically as the industry continues its exploration and development of ever deeper waters.

Similarly, the requirement for ultra-safe modules has grown in response to the extreme conditions which are now commonplace in today’s operating environments.

Balmoral Offshore Engineering’s design team was tasked with the development of a high performance ultra-safe riser buoyancy system to accommodate and perform in the most arduous of conditions. The team created a specialised riser buoyancy series, DuraFloat RIS, comprising a high impact protective skin and residual integrity system.

Significantly, DuraFloat RIS is designed to minimise the risk of cracking and fracture while delivering safe high performance uplift.

Buoyancy plays a critical role in the dynamic performance of the riser string and DuraFloat RIS is an important step forward for the industry. Its contribution to safety and performance should not be underestimated.

Lazy wave

DuraFloat RIS safety design features

DuraFloat Superlite™ and Superlite-X™

Drill riser buoyancy to 15000ft

Having successfully developed its DuraFloat drill riser buoyancy to working depths of 12000ft, Balmoral recognised that further performance improvements were required.

Basing their work on the original DuraFloat system, Balmoral’s technical and engineering teams developed a lighter syntactic material for use at operational extremes to 15000ft.

However, the essential increase in mechanical performance required to operate at these depths cannot be accompanied by a reduction in available buoyancy, and so foam density reduction was targeted alongside mechanical performance improvement.

The result of the R&D programme is DuraFloat Superlite and DuraFloat Superlite-X. With these latest additions, Balmoral Offshore Engineering now offers market-leading densities and performance levels across the entire spectrum of drilling operations.

All Balmoral DuraFloat and DuraFloat Superlite modules feature a number of advanced performance-related benefits including:

Extreme impact resistant shell
Anti-fracture reinforcement
Enhanced flexure resistance
Improved stacking and storage capability
Localised recess reinforcement

In simple terms, more uplift is provided for the cost when specifying DuraFloat Superlite and DuraFloat Superlite-X.

DuraFloat superlite to 15000ft

More uplift for your money

This chart shows how much more uplift is provided by Durafloat Superlite and Superlite-X systems in comparison to industry standard systems.

Even at 7000ft there is approximately 10% improved uplift performance. When depths of 12000-15000ft are reached this increases by an outstanding 30-50% respectively.

DuraFloat superlite to 15000ft

Common product features

External finishing

Drilling riser buoyancy operates in extreme conditions and must withstand harsh and constant handling. Durafloat modules benefit from an integral composite epoxy skin that delivers a robust impact resistant performance.


Balmoral Durafloat RIS modules are designed, manufactured and tested in full accordance with API 16F.

Attachment methods

Balmoral Offshore Engineering offers strapping with stainless steel axis bars and stud bolts as standard attachments between module and riser. Further options are available including through bolts located in reinforced pockets or stainless steel U-bolts with enclosed Kevlar strapping.

Dependent on riser geometry these options can be located within the pitch circle diameter (PCD) of the auxiliary lines thus reducing the transverse bending moment on the buoyancy module.

Flexural pads

Flexural pads are built into BOE buoyancy modules at strategic locations to ensure that excessive bending loads are not transferred from the riser to the module when lifted in the horizontal plane.

Flexural pads

Module stability

300mm flats are standard across the Durafloat range. This allows effective stacking in the yard and in the offshore operations environment.

A fully comprehensive handling and stacking manual is available from the company on request.

Module repair

BOE offers a comprehensive global repair service for damaged buoyancy modules that includes repair of full breaks and rebuilding of missing sections.

The company’s skilled buoyancy refurbishment technicians are available for field work at most locations worldwide.

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