Abstract
In this study, we explore the long-term creep performance of the Wel-lok BiSN plug, a novel bismuth alloy-based sealing technology developed for the efficient abandonment of offshore oil wells. Unlike conventional cement-based solutions, the Wel-lok system leverages a thermite reaction to melt a bismuth alloy in situ, which flows into the wellbore to create a robust, leak-proof seal upon solidification. This process, completed within minutes, offers a rapid and environmentally friendly alternative to traditional methods. We conducted a comprehensive experimental and numerical analysis to assess the plug's durability under simulated downhole conditions, including a 50-year pressure buildup scenario.The primary merit of this method is its ability to provide a quick and reliable seal, significantly reducing the time and environmental impact associated with well abandonment. The thermite reaction and subsequent bismuth alloy flow ensure a high-density seal less prone to leakage than conventional cement-based plugs. Additionally, the Wel-lok system's resilience under long-term pressure buildup, as confirmed by our finite element simulations using ABAQUS, indicates its potential for extended durability.However, the method also has its disadvantages. Relying on a thermite reaction necessitates precise control over the reaction conditions to ensure consistent alloy melting and flow. Any deviation could result in incomplete sealing. Furthermore, while the bismuth alloy offers superior sealing performance, its behaviour under extreme downhole conditions, particularly over extended periods, still requires further empirical validation.Our findings, derived from laboratory thermite reaction modelling and finite element simulations, confirm that the material properties of the Wel-lok system, particularly its creep behaviour, significantly enhance sealing performance. This research validates the Wel-lok system's potential for widespread application in offshore well abandonment and contributes to developing sustainable and reliable well-sealing technologies.
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