In a gas well, offshore UK, barium sulphate scale build-up from the tubing hanger prevents removal of the Wireline Retrievable Surface Controlled Sub-Surface Valve (WR-SCSSV) which is failing to close and required changed.

Additionally LMMV bonnet and stem requires changed-out, 2 plugs are required to complete this work scope (1 being set in the downhole safety valve nipple).

It was a Normally Unmanned Installation (NUI) Platform, so there was limited space, and only day shift operations.

Tubing hanger ID restriction limited milling bits (3.9” hanger restriction, WR-SCSSV No-Go 3.86”).

3.88” OD Tapered milling bits were manufactured to comply with well ID restrictions and size of replacement sleeve. The tool strings run included 2 x Release devices.

Tapered milling bit was replaced with the expandable milling bit which cleared the path. The expandable milling bit closed has 3-1/8” OD, and for this well their maximum opening was limited to 4.1” (tubing ID 4.126”).

The WR-SCSSV depth was achieved, this was clearly confirmed on surface by current draw down and milling response.

Successfully milled scale from below the tubing hanger to the WR-SCSSV.

Safety valve and LMMV were changed as planned.

Operator praised success and professionalism of the crew and support received.