Milling and polishing
- Well type Oil producer
- Deviation 15.3°
- Depth 552-554m (1,812-1,819 ft) TD @ safety valve
In 2018, a North Sea operator was attempting to set an orientation sleeve followed by the installation of a safety valve in one of their oil producing wells. During the operation, the safety valve flapper was locked into an open position using the Welltec® Dimple Tool.
The control lines to the valve were then punched and the orientation sleeve was installed. The new safety valve was subsequently installed however it did not set properly during the installation process. Attempts to jar on the valve did not resolve the issue.
A downhole camera was then run to further investigate the issue and revealed that the orientation sleeve was bent inwards, creating a restriction in the 4.5” safety valve between 1,812 ft and 1,819 ft TD.
After consultation with the client. Welltec proposed running the Well Miller® with the Well Tractor® to create a pilot hole and dress the orientation sleeve followed by running the Well Cleaner® Wishbone Honer (WBH) to polish the milled-out area. With the agreed upon plan in place, Welltec completed a system integration test that proved the concept would work. The tools were then mobilized offshore.
The first run with the Well Miller and Well Tractor tagged the restriction at 1,815 ft and successfully drilled a pilot hole. During both the second and third runs, scale was observed between 900 ft and 1,500 ft causing difficulties when running in hole and pulling out of hole. The tubing size was 4.5” with a nominal inner diameter of 3.958” and the Well Miller milled the orientation sleeve restriction successfully using a 3.9” bit on run two and a 4.1” bit on run three.
For the fourth run, the operator decided to mill the scale between 900 ft and 1,500 ft using a 3.9” Expandable Bit. Following these runs, a downhole camera inspected the scale bridges and confirmed that there were no leftovers from milling the orientation sleeve. During Welltec’s final run, the WBH polished the milled-out area of the safety valve. A final camera run confirmed that the area between 1,800 ft and 1,825 ft was much cleaner than before the run with the WBH and was ready for the new safety valve to be successfully installed.
The Well Miller with Expandable Bit successfully milled the orientation sleeve, granting full access to the tubing, and the WBH polished the area, enabling the operator to install a new safety valve and complete the intended operation. Downhole camera runs visually confirmed the quality of work performed by Welltec’s tools and personnel.
This operation showcases the ingenuity and innovation that Welltec’s tools can bring to cleanout interventions. Unexpected issues, as seen here, can be solved by planning, testing, and effective execution on e-line in quicker time frames and for less cost than heavier, time-consuming alternatives.