Development of bismuth-based solutions for well plugging and abandonment: A review

Plugging and abandonment (P&A) is a crucial step of the well life cycle. Regardless of how long one stretches the productive life of a well, P&A operations will have to be carried out eventually. The current panorama of our industry includes many wells to be plugged and abandoned, with steep requirements to abide by both regulations and societal pressure. In this context, we must guarantee that no leakage occurs with an eternal perspective in mind. Cement has been the prime material for this task, but recent studies have indicated the potential of degradation over time – especially in corrosive environments – and the creation of leaking paths due to its shrinkage. This has opened up a path toward the usage of alternative materials. One of the emerging candidates is bismuth, a metal with the unique characteristic of expanding when solidified. Such a trait could improve the overall sealability of wellbores and especially during P&A. This article discusses the current status of bismuth sealing technologies, introducing the basics of bismuth, the ongoing efforts to qualify it as a barrier material, its potential applications, and the challenges that still need to be overcome. The latest research indicates promising results in terms of its usage as a barrier element.