If an overbalance existed prior to pulling out of hole, then the only reasons for the well to flow are:·swabbing;·failure to keep the hole full;·losses induced by surge pressures.
Early detection of kicks off bottom can be achieved by observing whether the hole is taking the proper amount of fluid during roundtrips. This can be achieved by pumping across the flowriser with the trip tank (also called possum belly) which will give an immediate indication of gains or losses. Trip tank fluid levels observed during roundtrips should be recorded on a dedicated trip sheet and compared to previous roundtrips. This is the most accurate method of checking if the hole is filling-up correctly. If swabbing is observed, but the well does not flow, the string should be run back to bottom carefully and the possible influx should be circulated out. If the well shows any indication of flow, the well must be closed in and the string should be stripped back to bottom, because it is more complicated to handle a kick with the bit off bottom as compared to killing a well with the bit on bottom.
If severe losses are experienced, followed by a kick (i.e. when running in too fast) LCM pills should be squeezed into the loss zone formation via the annulus at such a rate as to prevent the influx rising up the annulus. The losses should be cured before the remaining influx is circulated out.
An inside BOP and RH kelly cock complete with lifting arms must always be available on the drilling floor and be ready for immediate use. If the well starts to flow whilst tripping pipe, the kelly cock should be installed and the well closed-in. Do not attempt to run the bit back to bottom with the well still open, since this may lead to excessive kick volumes and make well control much more difficult, if not impossible. The correct procedure is to close in the well at first indication of flow. Closed-in pressures will be much lower and will leave more options open during further well control operations.