1. n. [Well Testing]

Behavior observed when a well reaches stabilized production from a limited drainage volume. For constant-rate production, under pseudosteady state, the difference between the flowing wellbore pressure and the average reservoir pressure in the drainage volume is constant, and the pressure drawdown is a linear function of time, resulting in a unit slope in the log-log pressure derivative. The late-time buildup pressure will level off to the average reservoir pressure if the buildup duration is sufficient long, resulting in a sudden drop in the log-log pressure derivative. Pressure depletion occurs with continued pseudosteady-state production.

See: average reservoir pressure,  constant rate,  drainage volume,  pressure depletion,  pressure drawdown