Novel Well Intervention System Enables Safe and Efficient Well Re-Entry

Abstract This paper will present a groundbreaking subsea intervention and abandonment system, recently developed and deployed by Plexus, which facilitates re-connection to a shallow water well to allow a controlled intervention without the need for a subsea BOP. This paper will explain the unique and enabling aspects of the design, and how the system can be deployed to offer an alternative method of well intervention. Plexus's intent was to design a system, sized to be run from a standard jack-up, consisting of high-pressure spools with gripping systems which are hydraulically controlled via umbilical or ROV. The hydraulic systems on the spools allow manipulation of downhole tooling and equipment under controlled conditions, re-establishment of a high-pressure riser if necessary, and ultimately the safe plugging and abandonment of the well. The system was designed to be able to connect to a variety of different conductor states at the mudline, with an initial focus on connecting to the shoulder of a connector protruding above the sea bed. Following an accelerated design and manufacture process through 2023, the system was deployed in 2024. The high pressure spool assemblies featured a number of ROV-operated ball valves below dual gripping units. Tools were secured in the gripping units and sealed within the spools, with inner strings that were stripped through the gripped bodies. This combination of ball valves on the spool assembly and gripped stripping assemblies allowed vertical well entry with a capability to seal on the drill pipe at the sea bed so that downhole operations could be carried out and equipment removed under controlled conditions. Once these operations were completed, the gripping units were reused, this time to secure a high-pressure tieback string to connect to further well control equipment at surface for the remaining intervention operations. All planned stages of the operation of the system were carried out successfully, and the well intervention and abandonment was complete by the end of the year. The operational results have been reviewed, and the returned equipment has been thoroughly inspected and refurbished so that improvements may be incorporated into the design for subsequent use. The successful deployment, use, and recovery of this system have demonstrated that this equipment allows the safe and controlled abandonment of a potential high risk / high pressure environment for shallow water wells. This new method can allow for improved safety and significant cost savings.