LYTT, a software company delivering real-time insights to oil and gas operators by combining fiber optic data with hybrid analytics, has repurposed existing fiber optic infrastructure to support the remediation of a shut-in well in the North Sea. The well had been shut-in for more than three years as traditional diagnostic approaches failed to identify a solution to a sustained casing pressure issue.
With price volatility continuing to cause uncertainty for oil producers, the ongoing cost and resource requirement of managing unproductive assets is higher than ever. When traditional approaches to troubleshooting well integrity issues fail to deliver, it can leave operators with sunk costs from multiple remediation attempts alongside missed revenue – a particularly significant issue when the shut-in asset is in a costly offshore installation.
For the asset in question, LYTT was brought in after the operations team were unable to pinpoint the source of a leak in the tubing using a multi-finger caliper tool. Although a wall thickness anomaly was identified and a patch applied, this action failed to fully address the source of the leak, and the pressure issue remained. A further diagnostic attempt using a wireline acoustic sensing tool also failed to identify the source of the issue.
Lilia Noble, Well Integrity Technical Product Owner, LYTT, explains: “In order to fully address the pressure issue and support the team in restarting production, we used the existing fiber optic cable installed in the well and repurposed it as a Distributed Acoustic Sensing (DAS) array. We then analyzed the DAS data, alongside time and depth series data, to produce a real-time view the operations team needed to understand flow through the well tubing and into the annulus. This allowed them to isolate leak points and prevent further pressure build up. Crucially, we helped them see that the compromised area of tubing was greater than originally thought as we were able to detect evidence of multiple leak points within the wider tubing interval. These precise insights are unique to LYTT’s fiber optic approach and cannot be achieved through use of traditional point-based monitoring methods.”
Using the insights LYTT generated, the operations team were able to develop a reliable remedial design to address multiple leak points and bring the well back online.
Lilia concluded: “In order for the operations team to be confident that they can solve a flow-based problem for good, they need distributed and continuous data. Without this, they rely on traditional methodologies that fail to capture the dynamic nature of flow events, relying on luck to position the measurement tool at the right depth at the right time to identify a leak.
“In order to take chance out of the equation, we analyzed data collected in real-time from existing fiber optic infrastructure, applied our proprietary acoustic recognition algorithms and gave the team the visibility and the certainty they needed to solve the pressure issue permanently and bring the well back to life.”
You can read the North Sea case study in full in ‘Using Distributed Fibre Optic Sensing to Recover Well Integrity and Restore Production’, a new paper from LYTT that can be downloaded via: https://onepetro.org/SPECTWI/proceedings-abstract/21CTWI/4-21CTWI/D042S012R002/460500