Stavanger start-up Exedra has developed a new solution for verification of barriers intended for slot recovery or permanent P&A of wells.
Today, well barriers set for permanent plugging of wells, are verified by "tagging" the top of the plug with drill pipe, by inflow testing or by pressure testing the plug from above. These procedures are described in NORSOK D-010 guidelines. The tagging does not verify the pressure integrity of the plug, and the pressure test can be unprecise, and frequently non-conclusive due to plugging of potential leak paths with mud particles. In addition, the pressure test is normally performed by applying high pressure from above, hence not verifying that the plug is pressure tight in the opposite direction, from below.
Today’s method of inflow testing of barrier plugs is time-consuming and, in most situations, not practically possible.
Exedra’s idea is to introduce a novel P&A verification method, by applying a tracer gas below the barrier that is to be tested. The tracer gas (Helium) will provide a sensitivity approximately 1000 times higher than today’s conventional pressure method. The introduction of an unambiguous, fast and sensitive verification method will pave the way for more cost efficient P&A solutions.
When the tracer gas is released from a high-pressure canister, placed below the barrier to be tested, this will create a differential pressure across the barrier. The NORSOK D-010 guidelines states that permanent well barriers shall be tested to the equivalent of 70 bar pressure above Leak Off Test (LOT) at the relevant casing shoe, preferably in the direction of flow towards the external environment. This is not performed today, as there are no practical solutions available.
“Yearly Equinor perform 60 – 70 slot recovery operations where old wells are re-used by placing barriers in the old well tracks and sidetracked. Equinor also have a portfolio of 1300+ wells that eventually need to be efficiently permanently plugged by verified well barriers. This type of technology will fit well into Equinor’s tool portfolio and our ambition of safe and efficient plugging of old wells” says Tormod Fossdal, Leading Advisor SR/PP&A and member of the project steering committee.
The technology development is co-funded by Equinor Technology Ventures and ConocoPhillips and aims to accelerate the commercialization of Exedra’s barrier verification solution.
