Wel-lok M2M Perf-lokTM

Sealing Perforations in Cased Hole Completions

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.

Summary of Wel-lok M2M Perf-lok™ Features

No mechanical parts

Electronically activated

One trip operation

Differential pressure ratings up to 10,000 psi

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

Temperature ranges up to 160 °C

Benefits of Wel-lok M2M Perf-lok™ for Squeezing Perforations

Can be used even in damaged and corroded tubings and casings

Creates a gas tight barrier without the need to pump from surface

Non-corrosive and not affected by H2S or CO2

Can seal in cased or open hole

Millable to achieve a full bore

Non-porous and solidifies in minutes as opposed to cement and resins


The Wel-lok M2M Perf-lok™ was developed to isolate perforations in a cased hole completion for zonal isolation or well P&A. Unlike typical cement squeezes traditionally used for this purpose, the Perf-lok™ does not require squeezing as it is flows into the perforation tunnels by gravity due to its viscosity and density. Applying pressure to squeeze the cement can often cause the perforations to collapse and eliminate the ability to fill the entire void. If the Perf-lok™ can also be milled out inside the casing, maintaining a seal inside the perforations through its unique expansion properties.

Flow prior to tool setting

Flow prior to tool setting

Flow after tool setting

Flow after tool setting

BiSN WEL-LOK M2M Perf-lokTM Current Qualified Tools  
(in) (A)
(ft) (B)
4 1/2"3.58400
5 1/2"4.58550
9 5/8"8.25121,800
* 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.