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BEYOND THE HORIZON
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 produc-
tion 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 dur-
ing 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 under water 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
Composite materials have many
potential offshore applications