Case Studies

First rigless P&A in Gulf of Mexico offshore without section milling. Stopped gas migration in the annulus using V0 qualified seal

Plug and Abandonment with Wel-lok™ Cement Repair Tool (CRT)

The Wel-lok™ CRT (Cement Repair Tool) has been developed to eliminate sustained casing pressure, or casing vent flow, in cemented annuli. Unlike traditional methods of perf and squeeze or perf and wash, this tool does not require any surface pumping pressure to squeeze or circulate the sealing material into place. The tool is also run rigless on electric line, sealing through casing perforations, so section milling is not required.

The bismuth-based alloy has no porosity and solidifies to create a seal in minutes as opposed to hours with traditional cement and resins, eliminating the possibility of a micro-annulus being formed to allow future gas migration. If full bore access is required, it can be milled out and still maintain a gas tight seal in the annulus.

A GoM offshore operator had challenges with gas migration in the 7″ x 10-3/4″ casing annulus. A perf and cement squeeze had been attempted with no success. The challenge was to deploy a rigless solution to repair the cemented annulus for permanent abandonment.

As a forward thinking operator, always looking for the very best cutting edge technology solution, after discussions, Wel-lok™ Cement Repair Tool (CRT) was chosen for this well because of its proven success history in addressing gas migration for similar applications. Prior to the deployment of the Wel­-lok™ CRT, perforation guns were run in the well to establish communication between the 7″ and 10 ¾” casings. Based on best practices from previous installations, the perf sizes and penetration depths were optimized. The CRT was then run on a wireline to setting depth across the perforations and activated. This started the chemical reaction in the heater to melt the alloy.

With its low viscosity and high density (-80 ppgor specific gravity of -10), the alloy flowed through the perforations and into the annulus to cover the open channels in the cemented annulus. After solidification, the alloy created a gas-tight seal which was later confirmed by having no more gas bubbles observed on the surface.


The well was successfully bubble tested, resulting in zero bubbles at the surface and allowing the operator to complete the permanent well abandonment. Saved significant time and cost by eliminating the need to section mill with a rig.

  • BiSN saved the operator significant time and cost by eliminating the need to section mill.
  • P&A operation was accomplished on wireline without any rig.
  • After a previous failed attempt to perf and squeeze, BiSN’s alloy flowed into and sealed the cemented annulus without needing any pumping equipment.
  • The solution stopped the gas migration in the annulus and passed the bubble test for permanent well abandonment.

If you’re looking for a faster, permanent, gas tight seal, get in touch with our team of technical experts today.