Wel-lok M2M TDAPTM

Reduce Gas Migration in the Annulus of New Wells

Wel-lok M2M™ – An Overview of the Technology

The Wel-lok M2M™ technology consists of utilizing a modified thermite chemical reaction heater to melt bismuth-based alloys downhole. The melted alloys have a viscosity similar to water, and a specific gravity 10 times that of water, allowing them to flow into the smallest areas of a wellbore without the need of any surface pumping equipment. As the alloys cool and solidify, they expand to provide a seamless gas tight seal that is non-corrosive and not affected by H2S or C02.

Application of the Wel-lok M2M™ technology for Completions

The engineers at BiSN have developed the unique core Wel-lok M2M™ TDAP to be specifically applied to the completions stage of the well. This is not a one tool does all solution, 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.

Summary of Wel-lok M2M TDAP™ Features

Seals the annulus with advanced metal to metal technology

Gas tight seal without the use of elastomers

Utilises modified thermite chemical reaction heater to quickly melt bismuth based alloys

The melted alloy has the viscosity of water allowing it to flow into the area requiring sealing including micro-annuli in cement

Produces a seamless, gas tight metal to metal seal as the alloy expands when it solidifies

No mechanical moving parts once set

Available in a range of sizes to suit API & non API casings

Electronically activated

Benefits of Wel-lok M2M TDAP™ for Completion

Non-corrosive and not affected by H2S or CO2

Reduced downtime and costs for interventions

Reduced impact on the environment

Enhanced corporate responsibility

Reliable sealing solution

Extends the life of the well providing a long term seal

Reduced contingent liabilities

Easy to deploy in a single trip intervention

Temperature ranges up to 160 °C


The Wel-lok M2M TDAP™ (Thermally Deformable Annular Packer) was developed as a preventative tool to be run as part of the original casing string. It is run on an inner casing string and cemented into place. After cementing, the TDAP™ is set by running a chemical reaction modified thermite heater inside the casing to melt the alloy and create a gas tight seal in the annulus, eliminating the possibility of future casing vent flow when the cement in the annulus ultimately degrades and develops micro-annuli. If utilized in the design of the well, this tool can eliminate future expensive interventions and unreliable cement squeezes required to address surface gas pressure through cemented annuli.

Flow prior to tool setting

Flow prior to tool setting

Flow after tool setting

Flow after tool setting

(in) (A)
ALLOY (ft) (B)
5 1/2" x 8 5/8"7.88410.8
5 1/2" 10 3/4"9.8410.8
9 5/8" x 13 3/8"12.09410.8
* custom sizes available

BiSN tool range

You can view or download a PDF data sheet of all our other tools by clicking the links below.