This is the second part of the possible kick indications that I would like to share with you.
Decrease in d-Exponent Value
Normally, trends of d-Exponent will increase as we drill deeper, but this value will decrease to lower values than what we expect in transition zones. By closely monitored d-Exponent, d-Exponent chart will be useful for people on the rig to notify the high pressure transition zones.
Change in Mud property
Without any chemical added into drilling fluid system, its property change due to increasing in water and/or chloride content indicates that formation fluid enters into the wellbore.
For some mud, when salt water enters into the wellbore and mix with drilling fluid, the mud viscosity will increase.
In water base mud with low Ph salt saturated, the mud viscosity will decrease because of water from formation mixing with mud.
On the other hand, water contamination in oil base mud will result in viscosity increases.
Increase in Temperature from Returning Mud
By observing trend of temperature coming from mud return, temperature trend showing deviation from the normal temperature trend can be an indication of abnormal pressure zones, especially while drilling into transition zones.
There are some factors that you need to account for when you try to evaluate mud temperature changes as listed below;
• Surface temperature conditions
• Elapsed time since tripping
• Mud chemicals used
• Wellbore geometry
• Circulating rate
• Cooling effect when drilling fluid flows through a long riser (deep water consideration)
Increase in trip, connection and/or background gas
Gas in mud, normally called gas cut mud, does not be a sign of a well flowing because it could be gas coming from formation. Nonetheless, personnel on the rig should keep in mind as a possible kick indicator. Hence, flow show and PVT (pit volume total) must be closely monitored.
Gas in the mud can come from one or more of the reasons listed below:
• Drill into a formation that contains gas or hydrocarbon.
• Temporally reduce in hydrostatic pressure due to swabbing effect.
• Pore pressure in a formation is greater than the hydrostatic pressure provided by drilling fluid in a wellbore.
On the rig site, all kind of gas indications as trip, connection and/or background gas, must be fully monitored all time. It is the best practice to monitor in a chart format because we can look for the trend changes easily than just looking at one data point.
I wish you enjoy reading about the possible well control indicators.
Reference book: Well Control Books