Case Studies

Proactively Addressing Bradenhead Pressure in the DJ Basin December 2019

Well Completion with Wel-lok™ TDAP

Identification of problem

A common issue in the DJ Basin, and throughout the world, is Bradenhead (or surface casing) pressure. It is caused by cement channeling in the production by surface casing annulus and can lead to costly interventions and abandonments over the life of a well. One operator in the DJ Basin decided to address this issue up front, during the original well construction, implementing this proactive solution on all new drill wells going forward.

To avoid disruption to the well and damage to the casing during an intervention, the solution must be implemented before there is an issue, as part of the original casing program.

A Wel-lok™ TDAP is cast onto the outside of a full joint of 5 ½” casing and run in the well as part of the production casing string with a marker joint directly below. This joint is run to a depth above all producing zones in the area to act as the final barrier in the well if/when gas migration occurs. To ensure the bismuth alloy could seal against the open hole formation, when the casing is cemented in place the top of cement is stopped below the casing joint with the cast alloy. If Bradenhead pressure is seen at any time during the life of the well, a BiSN modified thermite heater can be run on wireline inside the casing and activated to melt the alloy and create a V0, gas tight seal in the annulus. By preplacing the alloy in the annuls, the seal can be created rigless without the need to perforate the production casing. The depth of the alloy sleeve can be found by running a CCL and locating the marker joint directly below the alloy.


A Wel-lok™ TDAP has been successfully deployed in 6 new drill wells to date with further installations ongoing. BiSN awaits the call from the operator to deploy a modified thermite heater and create a seal once Bradenhead pressure is seen.