Addressing Bradenhead Pressure during Well Construction in the DJ Basin April / September 2019
Well Completion with Wel-lok™ TDAP
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.
1: Issues to overcome
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 was cast onto the outside of a 5 ½” marker joint of casing and run in the well as part of the production casing string in 10 new drill wells. This joint was 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 was cemented in place the top of cement was 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.
A Wel-lok™ TDAP was successfully deployed in each of the 10 new drill wells. BiSN awaits the call from the operator to deploy a modified thermite heater and create a seal once Bradenhead pressure is seen.