A leading operator in Western Australia was carrying out a rig move during a drilling campaign. While they were moving the anchor of a mobile offshore drilling unit over live hardware the anchor chain become entangled with a subsea christmas tree and caused considerable damage. After subsea inspections were carried out the extent of the damage became clear; the chain had sawed completely through part of the christmas tree and in the process severed the unitech gas lift connector and flowline off the tree, leaving only a broken API flange weld neck flange in its place. The damage rendered the christmas tree inoperable but, thankfully, the well integrity remained intact.
Rapid Response Engineering Solution: Australia
The client approached Proserv to understand whether the problem could be repaired economically via ROV. The remit was simple; re-establish the unitech connector on the tree and deliver the system in five weeks.
Some of the challenges were significant and included:
Incredibly tight deadline
No tool existed to perform the task
API compliance was to be retained so no modifications allowed
Near 100% redundancy required
Proserv developed a new spool support frame so that the orientation and attitude of the replacement spool could be adjusted to adopt that of the damaged tree. An ROV operated, semi-automated flange bolting tool completed the connection.
The scope of supply included removing damaged sections of the gas lift spool, delivering and supporting a new spool on the seabed adjacent to the tree, and connecting the new spool flange with the existing via a standard API flange. Pressure testing of the completion was required to verify integrity of the
- Provided a qualified, industry standard, bolted flange connection in a subsea environment
- All tooling used for the bolting operation was removed from the spool, guaranteeing enduring integrity of the spool
- Support frame isolated the flange from external loads, and allowed the location of the spool to be adjusted in 3D space