TABLE OF CONTENTS Gas migration can occur when a well is shut in on a gas kick. It is indicated by a uniform increase in both the SIDPP and SICP. If the influx is allowed to migrate without expanding, pressures will increase everywhere in the wellbore. If it is ignored it can cause formation damage and mud losses. The worst-case scenario would be an underground blowout.
Gas migration can be controlled using two methods:
Drill Pipe pressure method
Volumetric method
Drill pipe pressure method
English units
This is a constant bottom hole pressure method of well control, and it is the simplest method. In order to use this method, the bit must be on bottom with no float in the string.
Procedure:
Allow the SIDPP to increase by a safety margin: 50 100 psi. This is the lower limit. The SIDPP must not be allowed to decrease below this level.
Next, allow the drill pipe pressure to further increase by another 50 100 psi. This is the upper limit.
Open the choke and bleed fluid out of the well until the drill pipe pressure drops to the lower limit.
Repeat steps 2 and 3 until circulation is possible or the gas migrates to the top of the well.
Metric units
Procedure:
Allow the SIDPP to increase by a safety margin: 350 1400 kPa. This is the lower limit.
Next, allow the drill pipe pressure to further increase by another 350 1400 kPa. This is...
