well control, page-20

Ya,

The can of Pepsi analogy isnt the best one for the water kick theyve taken. Without access to rig sourced details of what happened Id say what happened is they were drilling an overpressured shale section and then hit a thin permeable zone (sand/silt....maybe even a fracture). In this situation you can be drilling through an overpressured shale which wont kick because it has no permeability. As soon as you hit any sort of permeable zone the well will kick. Conoco took such a kick in Barossa-1 and its common at the top of the Caswell on the Ichthys Field. The gas peak associated with the water kick is probably more a result of the well being underbalanced rather than due to the presence of gas bearing reservoir rock.

As a matter of interest then normal proceedure in the case of a kick is usually as follows:

1. Shut in the well at the BOP (usually using annular or "bag" preventer).
2. Monitor drill pipe and annular pressures and determine magnitude of kick and type of fluid.
3. Determine mud weight required to kill the kick and circulate same into the well, continuing to monitor pressures until the well is static.
4. Open well and monitor. If static drill ahead.

Ya is right when he says people sometimes lose their jobs for missing the warning signs of a kick. However in some cases there isnt much warning especially in the case of thin permeable zones. More often than not when formation pressure is gradually getting closer to your mud hydrostatic youll see such things as increases in background gas, connection gas, pressure cavings at the shakers and other classic indicators of overpressure. If youre running LWD tools then modelling of formation pressure is possible using resistivity and sonic data. That said Ive been on wells where these indicators havent been present and the first indication of overpressure is an increase on the mudflow out of the well followed immediately by a mud pit level increase. By this time the kick has happened and its shut in time.

Okay I think Ive probablly added enough to the confusion so will let others rephrase what Ive just written in laymans terms.