An unwanted influx of formation fluid (oil, gas or water) into the wellbore, caused when downhole pressure exceeds the mud's hydrostatic pressure. An uncontrolled kick can become a blowout.
The two lines of defense
Primary well control is the mud itself: its hydrostatic pressure keeps formation fluids out. Secondary well control is the blowout preventer (BOP) — a stack of valves that can seal the well in seconds if a kick gets past the mud.
How a kick is handled
- Detect — signs include a pit-volume gain or increased return flow.
- Shut in — close the BOP to seal the well.
- Circulate out — pump heavier kill mud to remove the influx and restore balance.
The BOP is the last line of defense against a blowout. On offshore wells it sits on the seabed and can be activated remotely.
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Frequently asked
A kick happens when formation pressure exceeds the hydrostatic pressure of the mud column, letting formation fluid flow into the wellbore — often due to too-light mud or drilling into an unexpectedly high-pressure zone.
A blowout preventer (BOP) is a stack of high-pressure valves at the wellhead that can seal a well in seconds to control a kick and prevent an uncontrolled blowout.