5 project-critical considerations for a successful conductor slot recovery
2. HAVE ALL ACCESS AND SLOT CONFIGURATION ISSUES BEEN CONSIDERED?
As a starting point, take time to consider the location and configuration of your slots. Are the target slots accessible and are there structural restrictions for either removal of old conductor or installing the new one?
Inner slots may not be accessible for above seabed cut or for easy deflection of a new conductor. A specialist provider will be able to quickly survey your infrastructure and help you identify and understand these issues.
A spider plot of existing wells can be a useful tool to indicate any new well trajectory issues. Other common issues to consider include existing templates on the seabed, the locations of old slot guides, structural beams on the seabed or close to the seabed, or any post-installation changes to the platform (such as additional piping). Any of these could impede the removal of your old conductor or access for the required equipment.
3. CAN YOUR CHOSEN CUTTING SOLUTION COPE WITH ‘SURPRISES’ IN YOUR ANNULI CONFIGURATION?
The Claxton SABRE™ subsea abrasive cutting system’s powerful abrasive jet being tested overboard, prior to downhole deployment.
Often older conductor and casing strings can throw up surprises – which means careful consideration needs to be given to your choice of cutting solution.
Access is one issue to keep in mind: depending on your jacket and guide configuration, the cut may be above or below the seabed and may require the use of either an external marinised diamond wire cutter (above seabed) or internal abrasive cutting tool (below seabed).
Regardless of the final choice be aware that the casing configuration and any internal loading may not be uniform – eccentric casings and inconsistent tension or internal loading are relatively common occurrences and your choice of cutting tool should be able to cope with these variations.
Internal abrasive water jet cutting can overcome most of these issues. The abrasive jet (a high-pressure mixture of air, water and a mineral cutting medium) of tools like the Claxton SABRE™ system can cut cleanly and quickly regardless of casing configuration, eccentricity or annuli contents.
Note also that abrasive cutting gives the benefit of finite control of the cutting height and a clean cut compared to knives – both of which are important for slot recoveries.
4. WILL YOUR PLATFORM WITHSTAND LATERAL LOADS?
Conductor Deflection Tools, such as the sample diagrams shown above, mitigate loads being transferred to your platform jacket.
While the operation is a well-proven means of enhancing the economics of older platform infrastructure, the platform itself can pose a number of engineering challenges within the process – not least of which is the running of the new conductor.
Traditionally a ‘whipstock’ is inserted into the ‘stump’ of the old conductor – above or below the seabed – and this forms a kick-off point for the new conductor. In most instances this can be achieved without issue, however, the process of running a new conductor will transfer loads to the jacket structure hence it is important to fully calculate how the jacket will react – obviously older and smaller jackets will be less tolerant of these loads.
Conductor Deflection Tools can mitigate lateral loads and avoid undue stress on your jacket structure. Deflection tools perform the same role as a conductor whipstock, but include a ‘sheath’ for the conductor itself and transfer the load from running a new conductor into the existing one.
5. ENSURE AGED CONNECTORS ARE TAKEN INTO CONSIDERATION
When recovering a platform slot, the cutting and recovery operation is usually given the most consideration – and rightly so. However, one item is sometimes overlooked that can make the operation significantly more challenging: The integrity of the connections in the conductor and casing string.
While connectors may have sufficient integrity while the conductor is in-situ, there have been reported incidents where the string has parted during pulling and recovery, creating significant downtime and additional cost.
Claxton provides bespoke pinning tools that can secure your conductor subsea during the slot recovery operation, even where clearance is tight – negating the issue of fatigued connectors.