FlexGel Seals North Sea Annulus Riser Breach
10 February 2012Flexlife says it has successfully applied its FlexGel product to tackle corrosion in a North Sea operation for a major oil company.
Flexlife had discovered the annulus breach during testing in a
4.5-in. (11.4-cm) gas main flexible riser, 4.5 m (14.7 ft) subsea.
The company applied 9,500 l (60 bbl) of FlexGel to fill the I-tube
from 11.5 m (37.7 ft) above the sea surface to 33.5 m (110 ft) subsea.
It was pumped in approximate meter increments to allow time for the
product to settle and displace all water and air in order to fully
surround the breach.
Flexlife’s Stuart Mitchell said: "It is common for the outer sheath
of flexible risers and umbilicals to be damaged either during
installation or even by regular friction caused during operation. If the
problem is left un-addressed, it can lead to rapid corrosion of tensile
armor layers and premature pipe failure.”
He said that the enclosed area inside a caisson is particularly
problematic because there is restricted access for inspection, and
damage usually occurs around the splash zone level where oxygenated
seawater can cause accelerated corrosion.
The advantage of FlexGel, Mitchell said, "is that it can be deployed
from topside or subsea without the need for costly intervention by rope
access or diving teams and the associated health and safety risks of
those types of operation.”
The oil-based product is non-soluble in water, with a density that
can be adjusted to suit the application. In this case, the formulation
was devised to halt corrosion of damaged areas of flexible risers or
umbilicals within caissons.