Requalifying 15-Year-Old Suspension Plugs for Final Well Abandonment
In July 2025, two suspension plugs installed more than 15 years earlier were successfully requalified during final Plug & Abandonment operations in the UK North Sea. Dedicated pressure testing confirmed the integrity of the existing mechanical barriers, allowing them to be accepted within the permanent abandonment programme and avoiding the need for additional deep-set plugs, reducing rig time, risk, and cost.
Region
Year
In situ
Challenge
As part of a wider Plug & Abandonment (P&A) campaign in the UK North Sea, the operator was progressing wells from long-term suspension to final abandonment. Two of these wells contained Interwell’s Retrievable Bridge Plugs (RBPs) installed in 2010 as temporary suspension barriers, which had
remained in situ for more than 15 years.
Prior to placing permanent cement abandonment barriers, the operator needed to determine whether these existing mechanical barriers could be requalified and relied upon within the abandonment sequence, or whether additional deep-set mechanical barriers would need to be installed.
The key challenge was to assess whether two RBPs installed over 15 years earlier as suspension barriers still retained sufficient integrity to be accepted as qualified mechanical abandonment barriers within the permanent abandonment programme.
The operator required confirmed pressure integrity before these barriers could be relied upon to support subsequent abandonment operations and cement placement. If the existing plugs could not be requalified, additional deep-set bridge plugs would be required, increasing rig time, operational complexity, and cost. The objectives were to:
- Verify integrity of existing deep-set mechanical barriers
- Avoid installation of additional deep-set bridge plugs where possible
- Reduce rig time and operational complexity ahead of cement abandonment
- Support efficient execution of the permanent abandonment programme
Solution
Two Interwell RBPs had been installed during the suspension phase in 2010:
- A 386–550 High Pressure High Temperature (HPHT) RBP (3.86” OD for 5 1/2” tubing) was set at 2497 m (8192 ft) Measured Depth (MD). This plug was selected due to a tubing restriction, which had been successfully drifted with a 3.9” gauge.
- A 420–550 Medium Expansion (ME) RBP (4.20” OD for 5 1/2” tubing) was
set at 2473 m (8114 ft) MD.
Both plugs had remained undisturbed for more than 15 years, serving as suspension barriers throughout this period. During final abandonment operations, each RBP was subjected to dedicated pressure integrity testing in line with the abandonment programme and operator requirements. The objective was to determine whether the existing mechanical barriers could be requalified and incorporated into the abandonment sequence ahead of permanent cement placement.
- The 386–550 HPHT RBP successfully held pressure at 1300 psi (90 bar).
- The 420–550 ME RBP successfully held pressure at 1600 psi (110 bar).
Based on these results, the existing RBPs were formally accepted by the operator as qualified mechanical abandonment barriers within the permanent abandonment programme. This removed the requirement to install additional deep-set mechanical barriers prior to placing the permanent cement abandonment barriers.
Value Created
- Two long-term suspension plugs requalified through dedicated pressure testing
- Existing mechanical barriers accepted for use within the abandonment sequence
- Additional deep-set bridge plug installations avoided
- Reduced rig time, operational complexity, and cost ahead of cement abandonment
- Permanent cement abandonment activities able to proceed as planned
- Two independently verified downhole barriers installed without reliance on tree valves or a riser
Key Capabilities
- Proven requalification and integrity of long-term barriers
- P&A solutions resulting in reduced risk, cost and rig time
- Proven ME & HPHT plug technology
- Seamless integration into cement abandonment
- Independent and compliant
barrier solutions
