JDK18457 - Milling and Polishing in The North Sea

Milling and polishing

  • WELL TYPE
    Oil producer
  • DEVIATION
    15.3°
  • DEPTH
    552-554m (1812-1819) TD @ safety valve

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 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.

Tools Applied

  • Well Tractor®

    The Well Tractor® was regarded as a revolution in the industry when it was introduced in the 1990’s. It enables operators to extend the reach of traditional e-line deployment into highly deviated and horizontal wells.

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  • Well Miller® with Expandable Bit

    The Well Miller® with Expandable Bit for hardware milling provides operators with a better way to repair wells with mechanical obstacles. It can pass through small ID and expand to a larger OD when activated.

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  • Well Cleaner® Wishbone Honer (WBH)

    The Well Cleaner® Wishbone Honer (WBH) is designed to clean deposits from tubular walls over intervals where the internal diameter changes, such as mandrels and profiles.

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