Well testing has been a critical step in well evaluation since the 1920s. It has always been the first real measurement of reservoir volumetrics and potential performance.

Described as a temporary completion, well testing gives the industry a chance to flow a well under controlled conditions, allowing it to clean up and stabilize. Total flow rate, as well as the holdup of various phases present, can be measured and representative samples can be taken under PVT conditions for laboratory analysis. Pressure transients can be obtained whose character gives clues about reservoir boundary conditions remote from the well being tested. Reservoir volumes can be calculated along with formation average permeability and near-wellbore formation damage, or "skin".