Well Miller® for Scale Removal helps return well to full production

Downhole safety valves
JANG162764 Well Miller® for scale removal helps return well to full production
  • Well type Oil producer
  • Well fluid density 8.54 PPG
  • Well temperature 186°F
  • Well pressure 2,815 psi
  • Well deviation 22.35°


A client in Africa recently needed to change out a Christmas tree to regain wellbore integrity prior to returning a well to production. During the drift run prior to setting an isolation plug, scale was encountered. Initially, slickline was used to run a standard 3.8″ OD broach and cut about 10’ of scale from ~ 600 ft. Then a larger, 3.83″ OD broach was run but could only increase the ID down to ~ 85 ft. Analysis of the scale cuttings showed a combination of barium and strontium sulphate, as well as a significant amount of naturally occurring radioactive material (NORM), resulting in the operation being suspended.

To avoid bringing in a rig, the client began exploring chemical and mechanical interventions for scale removal. Welltec’s e-line solution, the Well Miller was ultimately chosen as the way forward for removing the scale.


The plan was to apply the Well Miller 318 to mill away the built-up scale inside the tubing down to the 3.813” nipple profile in the tubing retrievable surface controlled subsurface valve (TRSCSSV). This would restore access to the tubing retrievable safety valve (TRSV). The higher amounts of NORM in the scale added additional considerations to the operation. Following some customization and a successful systems integration test (SIT), Welltec® deployed to the platform.

The total operation consisted of two successful runs. During the first run, the Well Tractor® and Well Miller were run with a 3.82” OD bit. Hard scale was encountered throughout the milling, but it was successfully removed. On the second run, the Well Tractor and Well Miller were equipped with a rotating scale brush to clean the top of the TRSV.

The well was now cleaned of scale down to the desired depth and the client was able to successfully set the plug and perform the desired well maintenance, thus returning the well to full production.


Welltec successfully achieved the client’s objective by removing the scale build-up inside the tubing and re-establishing full wellbore access to the TRSV. The Well Miller enabled the operator to return the well to 100% full production after it had previously been shut-in. Additional choking since the operation has increased the production by another 50%.

Welltec’s fast mobilization, combined with the benefits of the e-line interventions exceeded the client’s expectations, returning the well to production earlier than anticipated. The capabilities of Welltec’s Milling Solutions helped the client avoid the time and costs of bringing in a rig. Finally, in light of the NORM encountered in this well, all safety protocols were followed with no incidents.