Composite materials have interested engineers for decades. The reasons are obvious. Composites are lighter in weight than the metals and other materials they are used to replace. They are more resistant to corrosion and wear. And they have better fatigue characteristics.
While the oil and gas industry has used composites somewhat sparingly, other industries have embraced and advanced the use of composite materials. The aerospace industry, which introduced modern composites three decades ago, has pioneered composite use, integrating materials in aircraft designs since the 1980s. Since 1987, the use of composites in aerospace has doubled every five years.
One of the first aerospace applications was in tail assemblies on US F14 and F15 fighter jets. Gradually, composites were integrated into more components, eventually being used on wings and fuselages. By 1989, companies had begun using composites for more components. That year, Beech Aircraft Corp. introduced the Beech Starship, a twin-turboprop passenger plane that had an all-composite fuselage. It was the first aircraft with this feature, but not for long. The Eurofighter Typhoon, the first prototype of which was finalized in early 1994, not only had a composite fuselage, it was built with 82% of its structural weight made up of composite material.
Composites also have been applied extensively in the construction industry. Civil engineers have used them in structures ranging from claddings to complete bridge systems. One interesting application that was introduced relatively recently is in high-voltage electrical transmission towers, where engineers identified technical, aesthetic and economic reasons for a move to composite materials. The authors of an article on a pilot project, which was presented at the International Conference on Advances in Manufacturing and Materials Engineering in 2014, explain that the new materials – primarily fiber reinforced polymer composites – and design concepts reduce the dimensions of the support structure, which is a concern in congested areas where it is not possible to erect towers using traditional designs. The paper provides proof of the viability of a transmission tower built using E-glass and epoxy resin that meets the same mechanical requirements of a steel tower – at 17% less cost.
While the aerospace and construction industries have achieved economies through the use of composites, the offshore oil and gas industry has not applied composites so widely. Of course, composite grids and gratings, handrails, ladders, and flooring have been installed on offshore assets for years, and composites are being used for frac balls and plugs, but the offshore industry is not gaining efficiencies at the same level as these other industries.
Fortunately, advances in research and development are poised to change that reality. Composites are being used increasingly in subsea umbilicals and piping systems and more and more frequently are being used in offshore repairs.
One relatively recent repair was carried out on an offshore production facility where a 12-in. riser with back-to-back bends was extensively pitted. In some portions of the pipe, pitting had resulted in 60% wall loss. The pipe was covered by a contoured overwrap, delivering a complete repair that is designed to last for two decades. And the work was carried out in the span of a single day.
In another case, corrosion on riser support clamps discovered during an inspection could have shut down operations. An external surface of a 14-in. heavy wall structural cross member was severely corroded across a length of 8 m. In some places, the metal loss amounted to 80%. Repair required the construction of an engineered heavy-wall composite sleeve, manufactured using bi-axial glass architecture. Filler was applied and molded to rebuild the pipe surface to the original outer diameter, and sleeves were installed and cut to length to cover the repaired surface. When the repairs were completed, the riser holding clamps were safe for service and reinforced for dependable use for the remaining production life of the field.
The obvious value of these repairs is that they forestalled potentially critical failures that could have resulted in lost production or even environmental damage. The less evident value is that they were carried out in a few hours while the production systems were active – and they introduced no significant labor and material costs. The composite materials not only addressed the immediate problem, they will prevent further corrosion for up to 20 years.
This is only the tip of the iceberg. Composite repairs are potentially viable in a broad range of scenarios, including decommissioning projects, where it is critical to ensure pipe integrity to avoid unintentional hydrocarbon release; and in underwater pipeline repairs at depths to 30 ft. The possibilities have only begun to be assessed.
If the oil and gas industry is willing to take a closer look at composites and evaluate the successes accomplished to date, it is quite possible that in another couple of decades, the achievements in offshore oil and gas operations will be comparable to those already realized in other industries.
Vice President–Product Management and Technical Services, Clock Spring