Bismuth metal alloys: A new era in well plugging and abandonment?

Co-author: Marcelo Jaculli

Are bismuth alloys the future of the plugging and abandonment industry?
At this stage, giving a concrete answer to this question is premature. In the ongoing pursuit of safer and more eco-friendly approaches to plugging and abandonment, bismuth-based alloys stand out for their potential to revolutionize wellbore sealing methods making them safer and environmentally friendly. This blog discusses our recently published literature review journal article in which we highlighted the merits of bismuth-based alloys as alternative plugging materials, and conducted a critical analysis of the existing challenges that must be addressed for their successful qualification as barrier materials.

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What are bismuth alloys?

Bismuth (Bi) is a metal with a somewhat white, pinkish, silvery metallic luster. An interesting fact about bismuth is that once it oxidizes, unique rainbow-like colors appear on its surface (see picture below). This fooled alchemists and led them to mistake it for other precious metals like silver or tin. It was not until the 18th century that bismuth was recognized as its own distinct element. Apart from its colors, what makes this metal exceptional is its low melting point and its expansion upon solidification.

Rainbow-like colors after bismuth oxidation. Photo: Bjoern Wylezich/Shutterstock

The existing literature and recent experiments indicate that bismuth is a potential alternative to cement due to a set of unique characteristics, such as:

  • Relatively low melting point when compared to other metals (273℃)
  • Viscosity which is very similar to water when it is in liquid form (melted)
  • Very dense with a specific gravity (SG) of 10
  • Expands approximately 3% upon solidification (like how water expands when it turns into ice)
  • Non-corrosive and resistant to H2S and/or CO2
  • Non-toxic (usually used as a substitute for lead in some applications)
  • It is a eutectic metal which means that, when it cools below its melting point, it goes almost instantaneously from liquid to solid state bypassing the gel phase.
Wel-lok bismuth alloy plug. Photo: BiSN

Why bismuth in P&A?

P&A operations may have considerable costs involved, and thus the development of new cost-efficient technologies is of great interest. According to the OEUK Decommissioning Insight Report 2022, well decommissioning accounts for 48% of expenditure, and this expense is forecast to increase dramatically over the upcoming four years, as seen in the figure below. The expectation is an increase of £325mn between 2022 and 2025 compared with the previous three years.

Expenditure by Work Breakdown Structure. Figure: OEUK Insight report Decommissioning 2022

Here lies the interest in using bismuth as an alternative material. Bismuth plugs may provide better isolation with shorter plug lengths than what is required for cement thus favoring cost-effective P&A operations (Zhang et al., 2020). However, for proper usage, bismuth plugs must be qualified as barrier elements according to acceptance criteria described on the NORSOK D-010 (2021) for alternative materials. The plug length of any alternative material must be equal to or greater than what is required from a cement plug in the same scenario, as seen in the next table. Thus, there is interest in qualifying the bismuth plug to reduce these plug length requirements.

Open hole Cased hole Open hole to surface plug
100 m MD (measured depth) with a minimum of 50 m MD above any source of inflow/leakage point.

A plug placed in the transition from open hole to casing should extend at least 50 m MD above and below the casing shoe.

50 m MD if set on a mechanical/cement plug as fundament, otherwise 100 m MD.

If the qualified annular barrier length is 30 m and set on a mechanical/cement plug as fundament the plug may be 30 m.

50 m MD if set on a mechanical plug, otherwise 100 m MD.

Table 1: Minimum cement plug length for different scenarios (NORSOK D-010, 2021).

Potential Applications:

Bismuth-based alloys, especially bismuth-tin, have been tested and employed for several applications (Fulks and Carragher, 2021) such as:

  • Single bore isolation
  • Single annulus isolation
  • Isolation of sustained casing pressure
  • Zonal isolation including “squeezing” production perforations
  • Multi-annulus isolation
  • Water shut off through gravel pack screens
  • Sealing leaking DV tools
The sequence of operations for setting a bismuth plug inside a casing/tubing. Photo: BiSN


Despite the promising advantages of bismuth-based alloys, several challenges remain in fully qualifying them as barrier materials. Our research not only presents these innovative alloys as promising alternatives but also highlights and discusses the need for further investigation into their long-term performance and impact on other well barrier elements. Some of the major challenges highlighted were:

  1. Thermal Shrinkage
  2. Thermal Shock
  3. Effect of its expansion on the annulus cement
  4. Creep
  5. Liquid metal embrittlement
  6. Availability of bismuth and its consequent cost upon higher demand
Advantages Limitations and disadvantages
  • Very low permeability/impermeable.
  • Can be performed rigless.
  • Can create a usable barrier quicker than conventional methods.
  • In a liquid state, it has water-like viscosity.
  • Can withstand corrosive well fluids such as CO2 and H2S when pure.
  • Expands when solidified, adjusting to the wellbore shape in which the plug is settled, in opposition to cement.
  • Higher costs are compensated by the need for less material to create an acceptable plug.
  • Still little data available on sealing capability and durability.
  • Does not create a chemical bond to formation or casing.
  • Little data regarding its hydraulic bond strength to casing and formation.
  • Potential of liquid metal embrittlement.
  • Potential of creep and stress corrosion cracking.
  • Potential downhole fluid displacement when melted due to its higher density (SG≈8.5).
  • No control of vertical heat propagation during its installation.
  • Currently not qualified as a barrier, with the qualification method unclear and still needing a cement plug alongside.
  • Limited maximum length of the barrier.
  • Toxic if mercury or lead is used in the alloy.

Table 2: Summary of advantages and disadvantages of using bismuth plugs (adapted from Khalifeh and Saasen, 2020; Rios and Ars, 2021).

As the industry moves towards more sustainable and safer plugging and abandonment practices, bismuth-based alloys offer a glimpse into the future. Their potential to provide reliable, durable, and environmentally friendly sealing solutions positions them as a primary alternative to traditional sealing materials. However, the journey from the laboratory to the field is complex, requiring continuous research and collaboration across the industry. We invite you to read our paper, engage with our findings and keep an eye out for more upcoming publications! Your feedback and recommendations for future work would be greatly valued.

Read the full version of the review article:

Lewaa Hmadeh, Marcelo Anunciação Jaculli, Behzad Elahifar, Sigbjørn Sangesland, Development of bismuth-based solutions for well plugging and abandonment: A review, Petroleum Research, 2024, ISSN 2096-2495

Read more from the same author on this topic:

Hmadeh, L., Elahifar, B., Sangesland, S., Abrahamsen, A. E., 2023. A full laboratory study on the physical and mechanical properties of a bismuth plug. In: SPE/IADC International Drilling Conference and Exhibition

Hmadeh, L, Elahifar, B, Sangesland, S., 2023. The sealing behavior of bismuth-based metal plugs. In: Proceedings of the ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering


Fulks, J. M., Carragher, P., 2021. Squeezing perforations rigless – No pumping or injection required. In: SPE/ICoTA Well Intervention Conference and Exhibition

Khalifeh, M., Saasen, A., 2020. Introduction to permanent plug and abandonment of wells. Part of Ocean Engineering & Oceanography volume series. Springer

NORSOK D-010, 2021. Well Integrity in drilling and well operations, Revision 5. Standards, Norway

OEUK, 2022. Decommissioning Insight 2022

Rios, R., Ars, F., 2021. Plug and abandonment materials – Technology landscape. In: Offshore Technology Conference

Zhang, H., Ramakrishnan, T. S., Elias, Q. K., Perez Jr., A., 2020. Evaluation of bismuth-tin alloy for well plug and abandonment. SPE Prod. & Oper. 35 (1), 111–124

1 comment on “Bismuth metal alloys: A new era in well plugging and abandonment?

  1. Avatar photo

    Good work!

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