Eni UK Efficiently Mills Stuck Centralizer | SLB

Eni UK Efficiently Mills Out Stuck Metal Centralizer with Tractor-Powered Wireline Intervention Service

Published: 08/26/2020

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Mill stuck metal centralizer and retrieve toolstring

When a 6-in-long slickline fluted centralizer jammed in a nipple profile above the subsea safety valve of an injector well in the Irish Sea, Eni UK needed to have it milled out to access and retrieve the toolstring. Access to the fish was tight, in 4.79-ID tubing with a minimum restriction to 4.26 in.

A conventional bit hardfaced with tungsten carbide was deployed. However, it was highly inefficient, removing only 60% of the centralizer after 400 operating hours.

Photograph of successfully milled centralizer at surface
Centralizer (left) and milled centralizer recovered to surface (right).

Design a custom bit to optimize metal chips removal

Schlumberger collaborated with a custom bit manufacturer to design an annular bit with nine tips featuring three geometries for optimizing removal of the metal chips. The bit’s performance was tested on a similar centralizer with ReSOLVE instrumented wireline intervention service configured for milling in conjunction with a TuffTRAC cased hole services tractor. ReSOLVE service brings new efficiencies to milling operations by seamlessly integrating the tractor with the milling tool’s performance by using the MillOptimizer autonomous milling system.

Monitor milling progress in real time and efficiently mill jammed centralizer

The new bit design was efficiently advanced at 0.15 in/h in milling through the remaining centralizer in only 12 h. Eni UK was kept informed in real time of the rapid milling progress through ReSOLVE service’s continuous monitoring and control.

Graph indicating smooth milling using MillOptimizer autonomous milling system of ReSOLVE service.
Smooth milling using MillOptimizer autonomous milling system of ReSOLVE service.
United Kingdom, Europe, Offshore

When more than 2 weeks of milling with a conventional crushed tungsten carbide bit was ineffective at removing a 6-in-long jammed centralizer, Eni UK Ltd. deployed ReSOLVE instrumented wireline intervention service with a bit optimized for metal removal to finish the job in only 12 h.

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