With the aim of taking a rigless approach to plugging and abandonment (P&A) in Malaysia, a major operator required an offline well severance solution to cut three wells below the seabed on the wellhead platform, offshore Malaysia.
The main objective was to sever the wells below the seabed followed by recovering the conductor and casings to surface for disposal.
Traditionally, surface well P&A is carried out using a jack-up rig, therefore the key challenge for this scope of work was finding a well severance solution with limited space available on the platform and without a drill-pipe deployment option.
Claxton*, a cutting and decommissioning brand in Acteon’s Energy Services proposed water-abrasive cutting technology to complete the severance of the three wells below the seabed using the multistring cutting (MSC) tool due to its unique ability to cut internally through all casings in a single trip.
The MSC tool can be deployed inside casing from 7” to 20” and can cut up to 42” conductors from a modular deployment system to work offline from the vessel crane or a rig’s derrick system.
For the removal of the conductors, a 10” to 24” guillotine saw was offered to section the conductors into manageable lengths for disposal. A 16” to 36” double drill-pin tool was also proposed to drill 4” holes through the conductor and internal casings to insert a bespoke lifting pin for transportation of the conductor sections to a supply vessel.
Three technicians per shift were required for MSC operations and two per shift for sectioning and pinning activities.
The original scope of work was to cut 13-3/8” x 20” casing below the seabed, however, on arrival offshore the scope had increased to include an internal 9- 5/8” casing. As the MSC tool is modular and can assemble to operate in 7” to 20” internal casing, it was re-dressed and set up to provide a solution to the revised well conditions.
The majority of Claxton’s equipment was positioned on the work barge with supply hoses connecting the ancillary equipment to the MSC umbilical on the wellhead platform. By positioning the ancillary equipment on the vessel, the footprint on the platform was reduced significantly to only the MSC umbilical reeler, deployment frame and MSC tool.
The MSC tool was deployed on winch wire from the modular deployment frame until the MSC tool’s cutting nozzle was positioned 3m below the seabed.
Once at the desired cut depth, the MSC tool was locked and sealed into the inner casing and high-pressure water abrasive jetting was used to cut through the 9 5/8” x 13 3/8” x 20” casing in a single attempt. All three cuts with the MSC tool were completed within 10 hours, inclusive of deployment and recovery from the well.
Once all three wells had been severed below the mudline, the final phase of the operation was to remove the conductors for disposal by sectioning them into 10m lengths and transporting them to the nearby supply vessel.
The conductor was pulled from the seabed using a casing jack system and sections were cut using Claxton’s guillotine saw.
The guillotine saw’s reciprocating mechanical blade severed through the conductor and internal casings. To lift the sections, 4” holes were drilled, and a bespoke lifting pin inserted to provide a means of connecting to the vessel crane. The sections were transported by crane to the supply vessel to complete the recovery task.
All three wells were successfully severed below the mudline using the MSC tool. Following the MSC operation, the three wells were sectioned, pinned and recovered to surface with the guillotine saw and double drill pin tool.
The cutting process for all three wells was completed within 28 operational hours, from the first well deployment to final well deployment recovery.
The customer was challenging the traditional rig-based approach to P&A campaigns to be as efficient and safe as possible and Claxton adapted the deployment, recovery and proving methods to align with their vision.
*At the time of this project, Proserv FTS was contracted to perform the work. Proserv FTS has since been acquired by Claxton Engineering Services Ltd.
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