In-Service Repair of Flexible Riser Damage Experience with the North Sea Galley Field

摘要

Routine GVI of the Galley riser system indicated potential damage to the Gas Export riser. This was observed as a steady stream of gas bubbles emanating from within an inverted bellmouth used to constrain riser motion at the Floating Production Facility (FPF) pontoon level. The vented gas volume was consistent with permeated gas rates from the annulus, an indicator of damage to the external sheath of the riser. The inverted bellmouth negated inspection of the riser within, hence the cause of the damage could not be ascertained. To determine the condition of the structure the riser was isolated and raised to allow inspection of the damaged section. This inspection found structural damage to the outer layers of the flexible pipe including corrosion damage of the outer tensile armour wires reducing the structural capacity of the riser. The extent of damage instigated a multi-company, multi-disciplinary team investigation and implementation of unique remedial measures to ensure fit for purpose operations for the remainder of field life. Implementation of the permanent remedial works was performed and successfully completed with reintroduction of the risers to permanent service in January 2006. This paper describes in detail the novel and unique techniques used to repair and re-commission the damaged riser.