Tripping out of the hole is a critical operation, which drilling team must keep close eye on well control situation that can
occur anytime. Wellbore monitoring and hole filling equipment and must be working properly so that the kick can be quickly detected. You must be aware of and prepared for the well control situation every tripping operation.
While tripping, it can cause swabbing effect that may allow formation fluid entering into wellbore. The well may not start to flow since the swabbing effect is just started. The swabbing effect will result in reducing the overall hydrostatic pressure. If the well is continually swabbed-in until the hydrostatic pressure in the wellbore less than formation pressure, the well will start flowing. Any time that you see short fill while tripping out, you need to go back to bottom and circulate bottom up to confirm wellbore condition.
When the well control situation is happened during tripping operation, the drilling crew must shut the well in right away using the following "3 S" shut-in procedures.
Stab Valve: Install Full-Open Safety Valve (FOSV) that must be in an open position in drill string. Make up to drilling string and close the safety valve.
Space Out: Space out to ensure that tool joint must no locate in BOP element.
Shut-in well: Close the annular preventer or uppermost pipe rams. Open the upper choke line valve against a fully closed manifold valve at a choke manifold. Line up to trip tank to confirm that the well is shut-in and flow has been stopped.