Rawwater, the UK-based oil industry flow-assurance company, has announced the deployment of its well sealing innovation, the Bismuth Plug, in an abandoned South Alberta gas well. The Bismuth Plug is a high-integrity wellbore sealing patented technology in the form of a permanent and reversible plug. The South Alberta well was plugged using the technology, which was funded by Rawwater, the industry and the UK Government. It has been developed at a cost of £400,000.
Well abandonment
Oil companies have one technology available to them at present for permanent well abandonment: cement slurry is pumped and squeezed into the well bore to establish pressure tight casing sections. Onshore this is a relatively inexpensive method of sealing wells but offshore the process is costly and time consuming.
Sources inside the industry have estimated that approximately 30% of the 22,000 onshore and offshore oil wells abandoned per year leak to some undetermined extent. The cost of plugging and re-plugging the oil wells, coupled with potential environmental pollution issues, means alternative long-term sealing technologies are required.
The Bismuth Plug solution
The plug offers a more reliable alternative to cement plugs that are currently set in well abandonment procedures. The plug comprises a steel carrier spool to support a cast low melting point bismuth alloy ingot. Using existing wire line technologies the plug is installed in the wellbore at a predetermined depth. An integral electrical heater re-melts the alloy ingot, casting it into the wellbore. Computer models run at the University of Manchester enabled Rawwater to design the critical rapid melting and casting process.
The unique property of the alloy is that during the casting the alloy expands by up to 1% by volume, resulting in the casting swaged into the casing, establishing a high integrity gas tight plug. In situ casting ensures that the casing bore imperfections, corrosion and tooling scores do not affect seal integrity - the melt simply flows and solidifies in and around these defects.
Furthermore, given ever improving oil recovery technology, the wellbore could even be re-entered by simply drilling out the soft metal seal at some later time in the future.
Bismuth alloy sealing technology
The principal unique benefit of the Bismuth Plug is its mechanical simplicity allowing utilisation of existing well ‘downhole’ tooling. The cast in situ alloy creates a permanent and contiguous high-pressure seal that results in improved well bore isolation, environmental protection and elimination of re-abandonment costs.
Rawwater is looking for partners to exploit the use of the bismuth alloy sealing technology for the offshore market. If you are interested in finding out more about this unique process, contact Bob Eden at Rawwater Engineering (+44 192 576 8910 or email bob.eden@rawwater.com).
Twitter