Case Studies

Eliminating Gas Migration on a Remote Island in Australia November 2018 through April 2019

Well Abandonment with Wel-lok™ STC

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.

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.

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

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.