In oil and gas fields, once exploration or production phase concludes, the wells undergo plugging and abandonment (P&A), a crucial phase in their lifecycle. P&A aims to seal wells to prevent environmental contamination and hazards. In Norway, increased attention to this phase arises as more than 7000 wells are heading for plugging and abandonment in the North Sea till 2050. Compliance with specific NORSOK standards dictates the use of well-barrier materials tailored to stringent requirements.

Historically, cement has served as the primary well-barrier material for P&A activities. However, inherent drawbacks such as shrinkage, poor bonding, and susceptibility to gas migration have spurred exploration into alternative materials offering enhanced mechanical strength and sealing performance. Among these alternatives, bismuth-based alloys stand out as promising candidates.

This article is a literature review, aiming to disseminate international innovative endeavors from industry and academia alike, addressing the efforts made to achieve well integrity and environmental protection, using bismuth-based alloys as well barrier materials. At the beginning, the article examines diverse practices employed by 15 different industry stakeholders utilizing the same material. To date, bismuth-based plugs have been deployed as environmental plugs and for annular sealing, utilizing the intense heat mostly generated by an exothermic reaction from a thermite blend. The combination of these materials has made bismuth alloy plugs promising candidates as well-barrier materials, particularly because they may be deployed without the need for rigs, section milling, perforation, or casing removal. This significantly reduces both the time and cost of P&A operations. The paper describes various new technologies and field operations, highlighting how bismuth-based plugs are emerging as a novel solution that enhances well integrity and safety while also lowering operational costs. Furthermore, the paper provides a comprehensive overview of academic research focused on the BiSn alloy, detailing laboratory mechanical testing, microstructural analysis, and numerical simulations to assess its suitability for well applications. Overall, this article effectively communicates the significance of P&A operations, the necessity for advanced well barrier materials, and ongoing collaborative efforts between industry and academia to meet the challenges of integrity that a well may face. It contributes to the advancement of environmentally responsible well-abandonment practices and to the enhancement of the knowledge of the bismuth-based sealing methods used in this area.