Understanding Positive Kick Indicators
A positive kick indicator is a clear sign that the well has taken in a kick, meaning there is an influx of gas or fluid into the wellbore. Recognizing these indicators quickly is critical, as it helps the driller take immediate action to secure the well and minimize the volume of the influx.
Three Main Positive Kick Indicators of a Gas Kick:
- Unaccounted Pit Volume Gain
- A sudden increase in the pit volume without an obvious explanation is a sign of a kick.
- Increased Flow with Constant Pump Speed
- If the flow rate increases while the pump speed remains unchanged, this could indicate that a kick has occurred.
- Flowing with Pumps Off
- If the well begins to flow despite the pumps being turned off, this is a key indicator of a kick.
However, for a indicator to be positive, it’s essential to rule out other potential causes, such as:
- Thermal expansion or “U-tubing” of the mud
- Rig heave or other rig movements
- Ballooning or breathing formations (when formations expand and contract)
Liquid Kick Positive Indicators
The three primary positive kick indicators also apply to a liquid kick, where fluid (typically mud) enters the well. In addition to these indicators, there are some secondary indicators that may suggest a liquid kick:
- A slight decrease in the density of the mud returning from the well (though typically not significant and may not be immediately noticed.)
- A small increase in the string weight
- Changes in the chloride content of the mud (requires a chloride test)
- An increase in rotary torque
- Contaminated mud appearing on the shaker after circulating the well (bottoms up)
Interestingly, liquid kicks may not always cause an increase in casing pressure. In some cases, casing pressure may even decrease while the kick is being circulated up the wellbore.
Positive Indicators During Tripping
When tripping, certain signs may indicate a potential kick:
- Less mud required to fill the hole: If less mud is needed to fill the hole than expected, it could mean the well has taken an influx.
- More mud returning to the trip tank: If more mud than expected returns to the trip tank when running into the well, this may indicate an influx.
- Flowing with the pumps off: Like the earlier indicator, if the well starts to flow without pump activity, it’s a strong signal of a kick.
- Flowing up the drill string: If flow is observed in the drill string when no float valve is present, this is another positive indicator. However, before concluding it’s a kick, be sure to rule out potential causes such as:
- U-tubing due to cuttings in the annulus
- Flowback from ballooning formations
- Thermal expansion, especially in oil-based muds
- Flowback from drilling with a compressible fluid, which may expand after the pumps are turned off
Summary:
Positive kick indicators help identify if a kick has occurred, allowing for quick action to control the well. By recognizing these signs and ruling out other causes, well operators can take the necessary steps to manage the influx and prevent well control issues.
The correct action to tale in response to a positive indicator is to immediately secure the well.
For more information on positive kick indicators and how to react to them, see my Well Control Manual v2.6 at:
Well Control Manual V2.6 by Edwin Ritchie
