The Challenge
An operator in the Norwegian North Sea required the removal of 24 conductors including six tie-back wells which were installed in a subsea template. The 18 platform wells had a 20”x26” profile, with the tie backs being 20”x30” and one single 26”. All wells were to be severed 2 meters below the mudline.
The tie-back wells introduced significant technical constraints:
• The cutting manipulator had to pass through a 15in restriction inside the tie-back connector, which was present in all tie-back wells, before expanding into a 19in wellbore.
• A second cut was required above the tie-back connector to allow the wells to be recovered together with the subsea template.
• The client required both cuts to be completed in a single deployment for operational efficiency.
• On the single string well the cutting manipulator still had to pass the 15in restriction, while still being capable of seating securely inside a 26-inch conductor.
Additional project complexities included:
• Deployment from a custom Conductor Guide Frame positioned 48 meters above sea level.
• 175 meters water depth.
• 29 meters conductor stick-up, resulting in a total cut depth of 206 meters from wellhead to cut elevation, making these the deepest platform wells ever cut using xcalibre - Claxton’s Abrasive Cutting Solution.
• During annulus venting, a small hydrocarbon-like substance was observed. Before cutting operations could proceed, the entire 206-meter annulus column had to be confirmed hydrocarbon-free to eliminate environmental risk.
Standard tooling was not suitable due to the limited packer expansion range and internal diameter restrictions within the tie-back connectors.
