MILLING AND POLISHING IN THE NORTH SEA

Background

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 1812 ft and 1819 ft TD.

OPERATION

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 1815 ft and successfully drilled a pilot hole. During both the second and third runs, scale was observed between 900 ft and 1500 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 1500 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 1800 ft and 1825 ft was much cleaner than before the run with the WBH and was ready for the new safety valve to be successfully installed.

ACHIEVEMENTS

The Well Miller 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 clean-out interventions. Unexpected issues, as seen here, can be solved by planning, testing, and effective execution on e-line in quicker timeframes and for less cost than heavier, time-consuming alternatives.

WELL TYPE: OIL PRODUCER
DEVIATION: 15.3°D
DEPTH: 552-554M (1812-1819) TD @ SAFETY VALVE

 

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