First Deepwater Plug and Abandonment Project in Nigeria
Authors: Author Augustine Okosun , Author Osehojie Ojeh-Oziegbe , Author Oladokun Adubi 
Published: March 2024

As oil and gas reservoirs are systematically exploited, the constant drilling of new wells remains imperative to maximize reservoir productivity. Inevitably, this ongoing process leaves behind a cluster of wells that have exhausted their operational utility, necessitating compliance with local regulatory mandates and industry standards to abandon these wells in a process referred to as decommissioning and restoration. Oil and gas well decommissioning and restoration encompass the intricate process of permanently sealing off and discontinuing wellbores connected to oil and gas reservoirs that are no longer economically viable or productive and ensuring that the reservoirs are permanently isolated from each other and from the environment. This is achieved by recovering the upper completion tubing, production, and intermediate casing strings, followed by the placement of cement plugs to restore the caprock and create a rock-to-rock isolation of all the zones with flow potential within the wellbore. This approach prioritizes safety and environmental protection.

In alignment with this overarching philosophy, the project's strategic approach revolves around the decommissioning and abandonment of depleted wells as they reach the end of their useful life, adhering to Shell PLC policies and local regulations outlined in the Environmental Guidelines and Standards for the Petroleum Industry in Nigeria (EGASPIN). Notably, the midlife abandonment project in this deep-water Nigerian environment represents a pioneering endeavor aimed at the permanent abandonment of select wells that have outlived their usability, encompassing the isolation of all reservoirs with flow potential and the restoration of caprock.

A total of thirteen wells, each presenting varying degrees of complexity, were meticulously decommissioned and restored without any untoward incidents or accidents. However, the fourteenth well posed intricate challenges that necessitated its re-suspension during the abandonment process. A comprehensive re-planning effort ensued, with a focus on ensuring the availability of the requisite equipment to address these emergent challenges. This project engendered the generation of innovative ideas, particularly centered around enhancing well integrity, tubing and casing recovery techniques, and optimizing permanent isolation cement plug placement such as setting long column of cement(3000ft) wet-on-wet, which are poised to become foundational for future deepwater well abandonment in Nigeria, and potentially across the industry.

The insights garnered from this project have been methodically incorporated into the development of a comprehensive Standard Operating Procedure (SOP) for deepwater well abandonment. The lessons learned and best practices that underpinned the successful execution of the mid-life abandonment campaign are poised to play a pivotal role in guiding the forthcoming end-of-field-life abandonment project. These invaluable experiences and practices will be shared in detail within this paper, contributing to the collective knowledge within the field of well abandonment.