Abstract: Shut-in pressure survey is the conventional method for determination of gas reservoir parameters. For extra-low permeability gas reservoir, the time for pressure buildup is normally long, sometimes lasts several months. So it is necessary to do it based on the gas well production history so as to avoid economic loss caused by the shut-in. For wells with production history, the modern production decline analysis can be applied to yielding the formation parameters, and the semi-log figure of normalized time vs. normalized pressure is taken as the criterion to validate the calculated results. Case correlation study shows that for gas wells without shut-in pressure survey, this method can be used to resolve the reservoir parameters.

Key words: production decline, reserve, permeability, normalized time, abnormal pressure