Abstract: This paper presents the derivation of a flow equation, considering gas well producing at constant pressure in infinite gas reservoir with accounting for high velocity non-Darcy flow effect in vicinity of the well bore. With further treatment of this equation and analysis of gas well test data, formation permeability, non-Darcy flow factor and skin factor can be determined reliably. Examples show that as for gas well in which constant-pressure well test can be applied, the proposed well test method can acquire formation parameters conveniently and accurately.

Key words: non-Darcy flow, constant pressure, gas well, well test