water influx

1. n. [Well Testing]
The replacement of produced fluids by formation water. Most petroleum reservoirs are underlain by water, and water influx into a reservoir almost always takes place at some rate when gas or oil is produced. Whether appreciable water is produced along with gas or oil depends on the proximity of the productive interval to the oil-water contact or gas-water contact and whether the well is coning (vertical well) or cresting (horizontal well).