In order to predict the reservoir productivity, solve the problem of weak log response characteristics caused by complex pore structure and low productivity prediction accuracy by conventional logging methods. The method of crossplots was used to investigate the relationship between the enveloped area of well log curves in the clastic rock reservoir of the Xihu Sag in the East China Sea Basin and productivity. The sensitivity envelope area of productivity was selected as the productivity prediction index. Based on the principle of wave superposition, the envelope area productivity prediction index is constructed, the entropy weight method is used to determine the weight of each prediction index, and then the productivity prediction model is established by reservoir type. The results show that the four envelope areas of compensation neutron permeability, resistivity density, resistivity apparent wave impedance and apparent wave impedance acoustic wave lag have strong sensitivity to productivity. The accuracy of the productivity prediction model established in this paper is high, and the average error is 19.4%. It is concluded that the productivity prediction model based on envelope area can be used to predict the productivity of oil and gas reservoirs without dynamic test, which provides a new idea for the oil and gas reservoir productivity prediction method.