1. n. [Well Testing]

Flow into the wellbore during a well test, from a reservoir with no apparent outer boundary limit affecting fluid flow during the test period, the direction of flow being perpendicular to the axis of the well. Unless an outer boundary, such as a nearby fault, is close to the wellbore, it usually takes a day or more for outer boundaries to affect well-test results. Since most tests are of relatively short duration, outer boundaries usually do not affect test results.

See: fluid flow