All of well control articles in this website are based on gas kick assumption. Therefore, all the responses as bottom hole pressure, surface pressure, gas volume, maximum pit gain, etc are influenced by gas expansion and gas migration. In reality, you may face with water influx or oil influx which is quite different than gas influx.
The following indications showing water or oil kick are listed below:
• When the well is shut in, casing pressure will not increase because water and oil don’t migrate.
• When bumping the float, it is quite clear to see where the float is opened in order to obtain shut in drill pipe pressure.
• While circulating influx out of the wellbore, casing pressure will not increase too high because water and oil don’t expand like gas.
Actually, dealing with water kick or oil kick is a lot easier than gas kick because you don’t need to deal with gas migration, and gas expansion. Moreover, surface equipment will not be exposed to high pressure.
To confirm if this kick is water kick, you need to collect mud sample at the bottom and perform mud check. If the influx is water, electrical stability will decrease, viscosity will increase, and oil water ratio will decrease.
On the other hand, if the oil influx is suspected, you should see the following indications from the mud check: oil water ratio will increase, electrical stability may increase, and crude oil sample may be seen in the drilling mud.
For a good well control practice, you should treat all of well control as gas kick because it is the worst case scenario.
Reference book: Well Control Books