Verification of permanent P&A barriers for wells

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A quick, unambiguous and versatile method to verify integrity of a wide variety of downhole barriers

Page last modified
November 7 2023

Exedra AS has developed a new way to verify whether a dowhole barrier is leak tight.  The method is quick, unambiguous, versatile, and allows the operator to test in the direction towards the external environment. The method applies a well known, and mature technology from other industries, releasing a tracer gas below the barrier to be tested, and 'sniffing' above, to detect any possible leaks aross the barrier. The method allows the operators more flexible, lower cost solutions, enabled by lowered risk and acceptance from regulators. This will result in cost reductions, and at the same time reduced risk of leaking abandoned wells.  Examples include shorter creeping shale barrier, barrier across double casings, verification of PWC plugs, shorter section milled section, etc.  The current design uses Helium as tracer gas, and detectors in flow line provided by third party, typically a mud logging company. The Helium tracer gas can easily be interchanged with an alternative tracer gas if needed.  Exedra has demonstrated the technology together with Geolog International's modified gas detection system, and shown consistency and extreme sensitivity.   The method can also be used to qualify barriers for future CO2 storage. 


Reduces the P&A costs as the operator can be more flexible in choice of plugging method, for instance shorter creeping shale section
Reduces the risk of leaking abandoned wells, which can prove to be extremely costly, and also represent a reputational risk
Enables verification in direction towards the external environment
Enables verification of barriers across dual casings
Enables verification of short creeping shale sections
Enables verification of PWC barriers over single and dual casings
Enables qualification of new barrier materials, such as bismuth alloys, and thermite
New technology, with need to be qualified as a verification method


Length (including X-over) 2,5 m
Diameter 127 mm
Max operating pressure 7500 psi
Max operating temperature 130 deg C
Normal operating time 7 days (can be increased significantly)

Relative Business Impact


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Technology Readiness Level


Development Technology demonstration Mature / Proven
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Exedra AS is delivering a new verification method for permanent plug and abandonment of oil wells. The company was founded as a consultancy in 2016, but turned into a pure technology development company in 2018. The technology development is supported technically and financially by Equinor, ConocoPhillips and AkerBP.  The technology is now in the final stages of being qualified, according to AWES recommended practice. Results are being reviewed by DnV-GL. 

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