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Well-Abandonment Solutions Use Bismuth and Thermite Effectively and Safely

Traditional methods of abandoning a well by use of cement and bridge plugs are still common practice among most operators globally. Although resins have been used as an alternative, no major developments have been made in well-abandonment materials for nearly a century. This paper demonstrates a new way to create gas-tight seals during well abandonment, overcoming the limitations of traditional methods and reducing the operator’s liability and potential environmental impact after decommissioning has been completed.

Statement of Theory and Qualification Testing

Bismuth has multiple commercial uses outside of the oil and gas industry. The idea of using bismuth for sealing in downhole environments is not new; the earliest patents were filed in the 1930s. Bismuth possesses many unique qualities, including

  • Relatively low melting point (273°C) compared with other metals
  • Viscosity very similar to water when in liquid form
  • High density, with a specific gravity of 10
  • Noncorrosive and unaffected by hydrogen sulfide or carbon dioxide
  • Expands approximately 3% upon solidification
  • Nontoxic (used in place of lead in some commercial applications for this reason)
  • Eutectic metal, converting from liquid to solid state almost instantaneously when it cools below its melting point, bypassing the gel phase

The challenge in creating a seal with bismuth has always been how to deploy it downhole—melting it and then causing it to solidify and expand where the seal is required. Previous attempts were made with electrical heaters. These heaters required large amounts of power (480 V and 11 A to generate 540 kJ of energy) for hours to melt a relatively small amount of bismuth alloy. Voltage drops in the electric line limited the depth at which the tool could be run in the well. After melting, the electrical heaters could not keep the bismuth in the liquid phase long enough for it to reach the sealing area and fill the void it was intended to seal.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 193118, “Well-Abandonment Solutions Using Bismuth and Thermite,” by Paul Carragher, SPE, and Jeff Fulks, BiSN Oil Tools, prepared for the 2018 SPE Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 12–15 November. The paper has not been peer reviewed.
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Well-Abandonment Solutions Use Bismuth and Thermite Effectively and Safely

01 May 2019

Volume: 71 | Issue: 5

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