Completions Solutions

Issues encountered at
the Completions Stage

During the completions stage, it is important to ensure the sealing integrity of the well before production begins. One area in which sealing can be compromised is in the annular space between casing strings. Traditional methods of sealing the annulus with cement and Annular Casing Packers (ACP) are often unreliable due to elastomers failing or micro-annuli forming in the cement. This can lead to sustained casing pressure and gas migration that will require remediation at some point before the end of the well’s life.


BiSN has developed a tool utilizing their patented Wel-lok M2M™ technology to address annular sealing issues. This tool is known as the Wel-lok M2M TDAP™ (Thermally Deformable Annular Packer) and creates a metal to metal, gas tight seal in the annulus, preventing future gas migration and annular pressure concerns. Ensuring a competent annular seal at the beginning of the well’s life will eliminate the need of future expensive interventions or unreliable cement squeezes.

Summary Overview of the Wel-lok M2M™ technology

BiSN Wel-lok M2M™ technology consists of utilizing a modified thermite heater to melt a bismuth based alloy that cools and expands on solidification. Some of the advantages of this technology are:

Seals wells with patented metal to metal technology

Heater uses a thermite chemical reaction that is non-explosive, no special licenses or handling permits required

Can be deployed on any standard wireline without special connection

Bismuth has a viscosity similar to water when melted in the liquid state allowing it to flow into the smallest of areas including cement micro-annuli

Bismuth has a density 10 times that of water allowing the alloy to displace wellbore fluids

Bismuth expands on solidification which creates a V0 gas tight seal in accordance with ISO 14310

Bismuth is non-corrosive, environmentally friendly and is not affected by H2S, CO2 or acid washes

The seal is created within minutes and ready to test within one hour

Application of the Wel-lok M2M™ technology for Completions

The engineers at BiSN have developed the unique core Wel-lok M2M™ technology to be specifically applied to the completion stage of the well. This is not a one tool does all but a bespoke innovation which is adapted for annular sealing. Traditionally elastomer seals and cement have been used for decades to seal the annulus between casings. As many field engineers will testify, the elastomers and cement are known to have a high failure rate, having to be remediated using cement or resin squeezes. These are expensive, difficult and unreliable workovers.


The Wel-lok M2M™ TDAP (Thermally Deformable Annular Packer) is the new generation of metal to metal annular seals/packers. The alloy is placed in the well on the inner string during completion and is cemented into place. The unique BiSN design copes with the cementing process and still creates a gas tight metal to metal seal. After cementing the TDAP is set using a wireline activated chemical reaction heater, melting the alloy leaving a gas tight metal to metal seal. Due to the viscosity of the molten alloy being similar to water it will fill and seal the smallest of micro-annuli. The finished metal to metal seal is seamless.