Igneous rock often causes the abnormal response of well logging due to hydrothermal alteration，especially the false appearance of high neutron logging value，which restricts the identification and quantitative evaluation of effective storage space in oil and gas exploration. Based on the principle of neutron logging，combined with microscopic observation，it is pointed out that the hydrothermal altered minerals such as chlorite and zeolite which contain a large amount of crystal water is the main cause of high neutron value. When the neutron logging value is over 30% and no obvious anomaly exists in natural potential curve，basically it is invalid reservoir. It is suggested that the porosity calculation model associated with neutron logging should be substituted by the MOSTAFA model to quantitatively characterize reservoir porosity in case of se? rious alteration. The rock acoustic in the model could be determined by the method of the cross-plot of logging curves. Taking the igneous reservoir at the upper fourth member of Shahejie Formation in Binnan Oilfield as an example，the skeleton acoustic value is 167 μs/m and the lithology index is 1.706，and the average porosity is 15% calculated by MOSTAFA model. Through comparison between the porosity calculated by the model processing and the measured porosity of cores，it is confirmed that the model of MOSTAFA，which is suitable for carbonate reservoir，is good for evaluation of the porosity of igneous rock when an appropriate rock skeleton parameter is used，and it could be used to quantitatively evaluate physical properties of altered igneous rock in Binnan Oilfield.