Efficiently mill and underream section in offshore well
An operator was planning a P&A operation in the UK sector of the
North Sea. Its objective was section milling a 150-ft window in the 9 5/8-in
casing then underreaming the open hole—all in a single trip— to
enable placing a rock-to-rock abandonment cement plug against the original
Use integrated, single-run solution to achieve objectives
Schlumberger collaborated with the operator on an integrated solution
that would meet the P&A objectives while decreasing the cost and regulatory
concerns inherent to well decommissioning. The BHA solution included the
ProMILL system with new performance milling inserts that feature a concave
shape. The performance milling inserts were used in combination with the
conventional inserts to enhance cutter durability and improve swarf quality.
Additionally, the WELL COMMANDER valve was run to boost circulation by removing
cuttings at high flow rates, which eliminated a dedicated trip for conditioning
the wellbore fluids for the milling program.
The ProMILL system would eradicate all potential leak paths from the
abandonment barrier which is not possible to ensure when using perf-and-squeeze
Saved 3.5 days and USD 600,000 with single-trip solution
The integrated P&A solution performed the following operations in a single run:
- displaced and conditioned the well
set the 9⅝-in bridge plug on the taper mill
milled a 150-ft section
- underreamed the exposed formation to prepare the wellbore for a rock-to-rock abandonment plug
During milling, the operator achieved an ROP of 4.5 ft/h, representing a
50% increase compared with 3 ft/h, the average ROP of the operator's jobs
completed in the field. The knife wear on the ProMILL system was 30%–35%,
which was lower than has been previously seen in similar operations.
The window was completed in 50 h, saving the operator 3.5 days and USD
600,000. This operation set Schlumberger records for the longest single-run
window milling, section underreaming, and bridge plug setting as well as the
longest single-run milled window.