Eliminating Gas Migration on a Remote Island in Australia

Well Abandonment with Wel-lok™ STC

Statistics

Location:
Australia
Deviation:
Depth:
590'
Downhole Pressure:
288psi
Temperature:
40ºC
Setting ID:
6.276"
Restriction:
6.151"
Sealing ID:
8.861"

Identification of problem

A client was experiencing gas migration up the surface casing on all wells in a 14 well P&A campaign. Previous campaigns had been conducted utilizing traditional abandonment methods and materials resulting in continued gas migration up the cemented surface casings. After considering several different plugging materials, the client chose to utilize BiSN’s Wel-lok™ technology to address their gas migration issues for this campaign.

Issues to overcome

The production casing by surface casing annulus was cemented with gas flowing through the channeled cement. To achieve a bismuth seal in the annulus, section milling was required. The client also required a solid bismuth alloy plug across the wellbore so the modified thermite heater would need to be removed, not left in the center of the plug. This is done by pulling the heater out of the bismuth alloy when all of the alloy is liquid. Since the plugs were set shallow in the wells, the time to remove the heaters was shorter than on a deeper set plug due to the alloy cooling faster.

Application

On each of the wells, a section milled window was cut in the production casing out to the surface casing, a Wel-lok™ STC was set inside the window and the heater was removed. The casing sizes for these wells were as follows:

  • 7” x 9 5/8” – 5 wells
  • 9 5/8” x 13 3/8” – 8 wells
  • 13 3/8” x 20” – 1 well

Outcomes/Conclusion

Each of these wells were successfully inflow tested after setting the BiSN STC plug and many underwent long term monitoring. These were the first Wel-lok™ tools deployed in Australia.

About the application

The Wel-lok™ STC (Seal Through Casing) has been developed to achieve a gas tight V0 seal well annuli that cannot be achieved by traditional cement balance plugs. Run on electric line, this tool does not need surface pumping equipment to circulate the alloy in place. Due to its viscosity and density, once melted the liquid alloy will flow with gravity into the annulus. When it cools below its melting point it solidifies, expands and creates a gas tight seal across the entire wellbore. The entire process, from melting to solidification, takes place in minutes and the seal is ready to test within an hour.

Seal Through Casing - BiSN
Seal Through Casing - BiSN
Seal Through Casing - BiSN
Seal Through Casing - BiSN

How it works…

The Wel-lok™ STC (Seal Through Casing) has been developed to achieve a gas tight V0 seal well annuli that cannot be achieved by traditional cement balance plugs.

Get in touch and find a
permanent solution for your well

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