1. n. [Drilling Fluids]

An influx of formation water, usually salty and sometimes hard, into the mud in the wellbore. Saltwater flows contaminate freshwater or seawater muds, making it expensive, difficult and time-consuming to regain the mud properties. Influxes pose a lesser problem for saltwater muds. Saltwater contamination flocculates the bentonite clay in fresh- or seawater muds. Flocculated, thick, filter cake on a permeable zone frequently results in differential-pressure sticking.

See: bentonite,  clay-water interaction,  differential pressure sticking,  flocculation,  saltwater mud,  seawater mud