It is not unusual for Floating Production Storage and Offloading (FPSO) vessels to be on site producing oil for decades. More and more, these assets are remaining active beyond the original design life, and as the units age, processing systems and components begin to wear. Because taking FPSOs to dry dock for repairs is costly and impractical, maintenance is carried out offshore whenever possible. While this appears to be a simple matter, it is a complex undertaking that introduces logistics challenges and often is impacted by sea state and weather conditions. In addition, if repairs are made using traditional methods, production must be shut in while the work is being done, which compounds the cost of the repair.
Although composite materials have been used to repair offshore assets for many years, they are not always the first solution considered when damage is discovered on a drilling or production rig, but composite technologies are changing the way repairs are carried out offshore. They have been used for years in a broad range of applications, including structural repairs to risers, caisson leak repairs, and for life extension work on large components that have experienced corrosion and environmental damage. Adoption of this technology in the oil and gas industry has not been rapid, but composites are gaining ground as an alternative that can compete directly with traditional repair techniques to extend the service life of these critical assets.
When an operator discovered leaks on several live glass reinforced epoxy (GRE) cooling water lines on an FPSO offshore Angola, decisions were made to take immediate steps to mitigate the damage. Stress and internal erosion had led to cracks and through wall defects in several places, including a joint. A repair solution was needed that would arrest the leaks and restore the line integrity for continued safe service.
A traditional solution was not a good option because it would have required multiple areas on the line to be cut and replaced. Since that repair approach could not be carried out without shutting in production, the owner began looking for an alternative. Recognizing that a composite solution might be a better choice, the next step was to contact ClockSpring|NRI with a request to assess the situation and determine if a composite product could address the damage. Experts formulated an engineered composite repair (ECR) that would be able to restore the vessel to safe operations without halting production.
When engineers are designing a composite, they focus on three characteristics:
- Fiber type: glass, carbon, or aramid (strong, heat-resistant synthetic fibers frequently used in aerospace and military applications).
- Fiber form (typically roving, tow, mat, or woven fabric).
- Fiber orientation or architecture (Reinforcement can be oriented in any direction the designer desires. The most common structural elements are designed with greater strength in the direction subjected to the greatest load).
For a composite to be effective in an offshore environment, it must be designed to ensure its mechanical properties can provide the necessary strength to restore damaged components to their original design specifications. When installed, the composite must deliver performance that is the same as or better than a traditional repair in terms of safety, longevity, and economics.
Putting composites to work
Engineers from the ClockSpring|NRI office in Manchester examined the multiple GRE leaks on the FPSO, including one under a bolted flange on a 355-mm (14-inch) line and another on a joint between a 508-mm (20-inch) line and a 51-mm (2-inch) line. Taking into account the complex geometry, the team evaluated the products available and determined that the best approach would be to use its composite injection leak arrest system to seal the live leaks and then apply a Thermo-Wrap™ Inspectable ECR to reinforce the line and ensure continued service.
Two ClockSpring|NRI technicians mobilized to carry out the repair and reinforce both repair areas using Thermo-Wrap™ Inspectable, a custom-engineered system that uses a high modulus fiberglass architecture in conjunction with a patented epoxy system. Its thick, non-crimped, glass fiber architecture and nano-tube-enriched resin combine to yield high strength characteristics. This ECR is designed for high-temperature environments and contains a contrasting agent that enables the repair to be monitored using common radiographic inspection methods to “see” the composite repair as well as the pipe wall.
The first step in the repair process was to use a proprietary composite injection system to arrest the live leaks and Syntho-Poxy™ 101 to improve the complex geometry of the lines. With this step completed, technicians applied eight layers of the Thermo-Wrap™ Inspectable system on the 355-mm (14-inch) line and 10 layers on the 51-mm (2-inch) branch. Within 8 hours, the repairs were fully cured, and the lines were safe for continued service.
This advanced ECR allowed multiple damaged GRE lines with difficult geometry to be restored to safe operations without interrupting production and with little disruption to day-to-day operations. The final repair will enable monitoring for the duration of FPSO operations.
Sean Connolly, Managing Director, ClockSpring|NRI, Europe, has been involved in composite repair technology for nearly two decades and plays an instrumental role in the company’s growth. As founder of NRI Europe Ltd., and part of a recent acquisition that formed ClockSpring|NRI, he is integral to operational expansion within the UK, Europe and West Africa. Connolly has overall responsibility for sales, growth and safety for this important region. He has in-depth knowledge of pipeline and pipework repair methods both offshore and onshore and has extensive experience with the company’s expanding portfolio of composite solutions.