A former gas producing well in the Netherlands, drilled in 1969, was due to be abandoned. The annulus pressure were monitored since the well stopped producing. The B annulus was showing a pressure build up and was being bled down when appropriate.
During pre-engineering of the well a cement logging run revealed bad cement over the interval of the caprock and samples of the bled down gas showed traces of reservoir gas. Because of this, it was decided to remediate the annulus. However, there was only 20m of good caprock available to set a cement plug with a 5m rat hole below.
The Abandonator P&A unit was used to successfully remediate the well, set the cement plug, and further isolate the well.
After successfully retrieving the 5" tubing with the control line, the section milling 144m BHA was ran in, fitted with the following:
After the BHA was ran into the hole and tubing stump tagged at 1762m , the process of locating the casing collars to determine the final cut-out depth was performed. At the cut-out depth the mud was conditioned to 1.58sg WBM mud with a viscosity between 40 - 50 Cp.
The Cut out was made with 2100 lpm, 135 Bar, 90 RPM, 6600 ft-lbs, and from there on the window was successfully milled from 1735m to 1756.5m.
The next run planned was to under ream the milled section from 12-1/4" to 15" to guarantee a good cement bond against fresh formation.
The Under Ream BHA consisted of the following elements:
The same mud was used as on the previous run, 1.59 WBM with a viscosity between 40 - 50 Cp.
The next run was a 5" cement string consisting of 5" drill pipe combined with a closed end slotted mule shoe. A pancake type cement plug was successfully set and tagged.