Abstract: At present, the methods for determination of deviation factor of gas reservoir are mainly experimental measurement, formula calculation and chart curves. In field application, the programming calculation is needed, and for each calculation the program has to be used for each time, inputting a series of parameters as required. To resolve the heavy problem, this paper presents a new calculation method, that is, only to calculate the initial deviation factor one time, and then combine the material balance equation of constant volume dry gas reservoir with the actual production data, the deviation factor of natural gas is obtained. Applying to SZ gas felid of Daqing indicates that this method is simple, practicable and reliable.

Key words: calculation, deviation factor, material balance equation, formation pressure, gas reservoir