Negative Equipment LL with DNO

Norma (25/7-11 S) – Surface section

What happened:

The drill commenced with the Driller pressuring up the well with 30 bar.
The classic method of choke control in a well control situation is that the choke operator controls the operation. He or she instructs the pump operator to bring the pump up to speed as the operator manipulates the choke to maintain constant BHP.
It quickly became apparent that the local pressure gauges on the choke manifold made this very difficult. All three (P dp, P choke and P kill) are only marked in psi and have unsuitable ranges for typical well control operations (0-12,000 psi for P dp and 20,000 psi for P choke and P kill). They are old-style oil-filled units with dual needles.
On attempting to bring the pump up to speed while maintaining 30 bar (450 psi) P kill, it was found that the digital instrumention in the Driller’s cabin responded more quickly than the local oil-filled gauges at the choke manifold.

What was planned:

Performed choke drill prior to drilling out 20″ casing. At Odfjell’s request the drill was carried out using a MANUAL choke and local choke manifold pressure gauges rather than the usual remote choke and digital instrumentation controlled from the Driller’s cabin. This was a (sensible) request from Odfjell to give their crews experience of having to use a manual choke.

What was learned:

If this had to be done for real, better that a supervisor control the operation from the Driller’s cabin while monitoring P dp, P choke and P kill using the digital panel, calling out choke manipulation instructions by radio to the manual choke operator.

What actions are required:

One idea / suggestion would be to instigate a rig modification to the remote gauges at the choke manifold, whereby a T-piece is installed on all three gauges whereby a lower range gauge using bar calibration could be temporarily plugged in to each gauge.