Abstract: On the basis of petrophysical experiment of natural gas reservoir, the intrinsic relations between reservoir physical property, lithology, gas-bearing nature and AVO abnormal responses from gas reservoirs are summarized, including analysis of the responses sensitivity to the gas reservoirs. For gas reservoirs with high-low effectiveness, the variable porosity and variable gas saturation are simulated by AVO technique, coming to the conclusion that the AVO abnormal responses from gas reservoir with good gas-bearing property belong to Class-III, while those from one with poor gas-bearing property belong to Class-I and Class-II. Therefore, this AVO abnormal response could be used to improve the accuracy of parameters for interpretation and precision of fluid property recognition as references of regional prospecting evaluation.

Key words: gas reservoir, porosity, gas saturation, abnormity, response