Water depth is 1,300 ft (396 m).
Deployed via wireline from the drillship Noble Don Taylor, the lightweight, thermoplastic cap was landed, locked, and sealed to the wellhead using an ROV. The isolation cap and subsea wellhead were injected with USI’s proprietary, nontoxic, biodegradable Defender Stasis LT subsea equipment preservation fluid.
The low-pressure isolation cap design ensured that seawater was completely purged from the wellhead bore and external chambers and replaced with the preservation fluid.
John Fitzgerald, director of Sales and Marketing, USI, said: “Defender is the only ROV-installable protector cap that provides positive locking and reliable sealing to the wellhead mandrel. It is also the only cap of any size or rating that allows all seawater to be completely removed from the internal and external protection zones.
“The wellhead bore, ring gasket profile, and external connector profile are completely isolated from the subsea environment and immersed in non-electrolytic preservation fluid to protect against deterioration.”
The drilling program for the Bulleit well called for an estimated 12-month temporary abandonment period before the subsea tree installation. Protection against corrosion and marine growth during the abandonment was considered crucial.
According to USI, the technical team at Talos recognized the intrinsic value of maintaining the wellhead mandrel in the “as-installed” condition during the abandonment, and eliminating the costs and schedule impacts for remedial cleaning activities prior to subsea tree installation.