Abstract: According to well pressure performance, the drawdown curves can be divided into three phases, namely non-steady, transitional and pseudosteady states. The method porposed in this paper can be used to determine OGIP, gas-bearing area, boundary delineation, well location and vertical fractural length, and to provide effective permeability, total skin factor, shape-dependent constant of formations under the conditions of original formation pressure available at shut-in after short completion and open flow production at stable or generally stable production rate followed by testing the drawdown data. It is verified that the method is effective in case application. For the effective application of the drawdown curves, it depends on the pressure performance obtaining pseudosteady state and simultanious solutions using pseudosteady and non-steady procedures as neccessary.

Key words: gas reservoir, drawdown, OGIP, area, model