AGR CSS™ Subsea - Subsea Conductor Stabilisation for the Offshore Industry

AGR's CSS™ Subsea is a new solution to an old problem. Wave-induced damage to conductors and caissons is a well-known problem in the offshore world but AGR's new solution represents a safe and innovative subsea method.

In June 2011, AGR successfully completed a pilot project for Statoil on the Brage platform in the Norwegian continental shelf. Two subsea conductors were successfully stabilised with AGR CSS Subsea. The installation was fully performed with the use of an ROV.

Conductor stabilisation for the offshore industry

Over the past five years AGR has developed the Conductor Stabilisation Solution (CSS) to improve technical safety in the offshore environment. The unique technique implements polyurethane material which has extreme durability qualities.

The solution uses an elastic polyurethane compound which provides flexibility to absorb the shock impacts caused by lateral wave movements. The void between the conductor and the guide is filled with polyurethane, eliminating all horizontal movement, but allowing vertical conductor movement, which is a design principle.

Subsea conductor stabilisation

The AGR CSS Subsea solution focuses on HSE and eliminates the need for any divers. The solution offers a considerable time / cost saving operation compared to the traditional diver deployed systems.

The ROV operated subsea solution flies the prefabricated section to the installation site. The sections are zero buoyant in water prior to installation.

After the section is installed the buoyancy aid is removed and the section becomes negatively buoyant.

Benefits of the AGR CSS Subsea solution include:

• No diver operation required for installation
• Operation performed 100% by ROV
• No steel to steel contact between conductor and guide
• Stabilisers are fabricated to cater for misalignment
• Stabiliser sections prefabricated onshore before start of operation
• No need for post-installation maintenance
• The material is environmentally friendly
• The material is not affected by seawater environment

Topside conductor stabilisation for offshore installations

AGR CSS Subsea minimises wave-induced damages to an offshore installation by improving traditional techniques to obtain conductor / guide stability. Waves generate vibrations which are damaging to the conductors, risers, caissons and the installation in general. Conductors' hammering against the guides, resulting in fatigue and fracturing, is one known problem with lateral wave movement. Repairing these damages can be costly, challenging and even dangerous.

AGR has vast experience and excellent results with use of this technique on conductors, caissons and risers above sea level. The AGR CSS Topside was first used on a Statoil installation in 1999. To date, no preventative maintenance has been required on this cast.

Conductor stabilisation solution

A new elastic stress-absorbent compound called Elastogran™ is cast into the entire length and diameter of the conductor guide. The AGR CSS entirely replaces the traditional need for centering and chocking solutions and provides for a new, better and measurable solution.

AGR CSS benefits:

• Faster and better solution than traditional methods
• Uses the entire length and width of guide
• Three-step easy implementation
• Reduces wave-induced impact and damage
• Increased guide stability
• Extends life of conductors and caissons
• Subsea application
• No maintenance and long-lasting solution