HPHT UBD - Balance Point Control

Background

The platform was a HPHT gas condensate producer in the Central North Sea. A Well had been suspended with a shallow cement plug and was to be abandoned. Bellow the cement plug was the possibility of 800 bar.

Objective

The objective was to rig up a snubbing unit within the derrick of a jack up, then drill through the shallow cement plug and clean out down to the top of the bottom cement plug. The well was then to be displaced to kill weight mud.

Execution

Over a year of planning went in to this operation, with a BPC desk engineer working in the client office.
Significant engineering and modifications to the unit had to be completed prior to operation.
Very challenging rig up with the basket level 22 m into the derrick.
Numerous different parties involved meaning good communication was paramount.
Drills were performed to ensure communication channels were clear.
First half of plug drilled open hole.
Second half of plug drilled while holding 100 bar back pressure in order to provide cushion should pressure be encountered.
No pressure encountered so continued to wash down to the top of the bottom plug.
Stopped just short of top of the bottom plug as pump pressures were getting too high.
BPC assisted client with expertise and programme writing.

Results

Completely new rig up was completed without significant issues.
Significant amount of equipment to pressure test at high pressures and all tested successfully.
Communication between all the parties worked very well.
Operation was completed on time with minimal delays.
Great team work displayed by all parties on board.
Zero incidents and accidents.