Early-time pressure build-up data of low permeable gas reservoirs

affected by fluid phase changs and non-Darcy effect

can not be used in pressure data interpretation.In this paper

a new method is developed in which phase change is used as the condition

and Duhamel’s principle is used to derive formation pressure equation and then calculate the formation pressure in low permeability wells with early time data

and use this pressure as a match point to match the early time data

thus getting the formation parameters.It has been proved by practice that the parameters obtained by this method possess high reliability.