ABERDEEN, UK – Petrex has provided technical assistance for the Causeway and Fionn field subsea installations in the UK northern North Sea.
Both fields have been developed as a tieback to TAQA’s North Cormorant (NC) platform via two production wells equipped with electric submersible pumps and a single water injection (WI) well.
During the initial installation, the two producer wells were tied-in to the NC platform via rigid pipelines and a flexible riser, with umbilicals installed and commissioned for each well.
The WI well was connected to a rigidsubsea WI pipeline but could not initially be linked to NC, and attempts to install the WI flexible riser proved unsuccessful.
On assuming ownership of the facilities following a takeover ofValiant Petroleum, Ithaca Energy contracted Petrex to manage completion of the WI works. The aims were to connect the 6-in. WI riser with the NC J-tube, tie in the 8-in. WI pipeline to the riser, and commission the WI control system.
Surveys identified the cleanliness of the J-tube as the main reason for previous failures with the riser pull-in. Petrex conducted workshops with TAQA, Ithaca, and various suppliers. To achieve the required cleanliness a jetting system and cleaning pigs were deployed using facilities on the platform and a subsea winch.
Following J-tube cleaning operations the flexible riser was successfully pulled-in by the dive support vessel and staff on NC. The flexible was then tied into the WI pipeline and leak tested prior to completing subsea control system tie-ins and commissioning the entire subsea WI control system.