Negative Operational LL with Wellesley

Gnomoria (35/10-12 S) – P&A

What happened:

Observed flowback of the mud lost while running and cementing 9 5/8″ casing. Of ±200 m3 of mud lost, approximately 50 m3 returned due to wellbore breathing which had to be bled back in a controlled manor.

What was planned:

Cut & Pull 9 5/8″ casing including a flow check prior to POOH with cutter BHA.

What was learned:

The initial method to bleed back was up the choke and kill lines through the MGS back to the shaker pits. With a large active volume this made it difficult to track return volumes over time so the annular was opened and the trip tank used. This allowed too much gas cut mud into the riser which had to be dealt with later.

What actions are required:

If this occurs on another well, continue to bleed off through the choke and kill lines for longer to minimise the volume of gas cut mud that will enter the riser.

What Was Done

Gas cut mud had to be displaced out of the riser in stages by boosting the riser.