Triple Barrier With On-Demand Pressure Readout Enabling Dry Workover on Live Gas Cavern
In October 2025, a fully redundant triple-barrier solution was deployed on a live gas cavern in Germany to enable a dry workover under challenging completion integrity conditions. Three independently verifiable barriers with on-demand pressure readout provided continuous assurance of well control, reducing operational risk while allowing the intervention to be executed safely and in full compliance with ISO 14310 V0 standards.
Year
Region
Challenge
A gas cavern in Germany with completion integrity concerns required a complex barrier concept to allow for a dry workover. Recompleting a live gas cavern calls for a highly reliable and fully monitored barrier system to mitigate the risk of pressure-related failures during intervention. The existingcompletion architecture offered uncertain redundancy, tight well restrictions
and a short area available for setting barriers.
The operator needed a solution that not only enabled setting three independently verifiable barriers within a 20-metre well section, but also offered operational flexibility in case a barrier became compromised. Ensuring compliance with ISO 14310:2008 V0 standards while maintaining full real-time monitoring capability was essential.
Solution
The proposed intervention introduced a fully redundant, triple barrier system based on the deployment of two 11 3/4” High Expansion (HEX) Retrievable Bridge Plugs (RBPs) in the lower completion casing and one additional 8 5/8” HEX RBP. This approach ensured compliance with dual-barrier rules even in the case of compromised completion integrity.
The combination of three key Interwell technologies allowed the operator to perform the dry workover with the capability of verifying integrity of each of the three installed barriers, on demand, throughout the operation:
Interwell’s HEX RBP technology was one of the enablers of this custom solution. With a maximum running OD of 6 1/2” for the 11 ¾” barriers, it allowed passing the tool strings through an existing 7.05” landing nipple profile using conventional e-line.
Another critical element of the solution was the integration of Interwell’s Intelligent Barrier Valve (IBV) technology. Both 650-1175 HEX RBPs were installed in gaseous environments, while the uppermost 520-863 HEX RBP was to be installed in water, only a couple of metres above the upper 11 ¾” barrier. Due to the incompressibility of water, this could have compromised the plug setting sequence and thereby the barrier integrity. To mitigate this risk, Interwell developed a through-bore 520-863 HEX RBP, which was installed in conjunction with an IBV in open configuration, to provide a pressure relief path during the setting sequence. After the setting sequence, the IBV was closed, thereby providing testable V0 barrier.
Each of the barriers had been equipped with an Iconic Digital Transponder (iDT) enabling continuous transmission of barrier integrity data (pressure and temperature) from all plugs through an acoustic daisy-chain telemetry path up to surface via e-line. This allowed on-demand verification of all barriers at any
point in the operation.
Value Created
Interwell’s integrated triple-barrier solution delivered substantial value by significantly reducing operational risk and enhancing well control throughout the intervention. Real-time monitoring via the Iconic iDT system eliminated uncertainty around barrier integrity, enabling the operator to make immediate, data-driven decisions. This capability not only improved safety but also reduced the likelihood of non-productive time.
Besides allowing for the setting of three HEX RBPs in just a 20-metre section of the well, the IBV technology would also enable repeated pressure testing of the middle barrier, even after installation of the uppermost barrier. This could be achieved by opening and closing the IBV through application of pre-determined pressure signals. All this, without sacrificing ISO 14310:2008 V0 standards.
By adhering to ISO 14310:2008 V0 validation standards, the proposed solution ensured regulatory compliance and provided confidence in barrier performance. Real-time monitoring through the Iconic iDT system enabled immediate confirmation and periodical re-confirmation of barrier integrity, drastically lowering the risk of barrier-related failures and minimising time spent on manual verification.
The intervention provided a robust, fully monitored, and highly adaptable barrier strategy that improved safety margins, reduced operational risk, and delivered cost and time savings across the intervention workflow.
