Abstract: Abstract:Seismic attribute is related to several geological factors, and thus any one attribute is hard to represent the complex and comprehensive geological characteristics of coalbed methane (CBM) reservoir. The key for selecting the sweet spot of CBM exploration by using seismic attributes is to find an accurate explanation of the seismic attribute characteristics, and to decide the main geological parameters of CBM reservoir. In the study area, the coal thickness, gas content, and permeability have high correlations with seismic attributes of amplitudes, frequencies and curvatures, respectively. Based on these correlations and a transformation of multiseismic attributes, this paper provides a forecast model for the main geological parameters of CBM reservoir. Then, a dynamic weight coefficient median method is used to determine the weightings of the key geological parameters that are related to the highest frequency of median evaluation value. Finally, the sweet spots of CBM production are forecasted by using the equations of evaluation values. The evaluation results of Zhengzhuang field show that the most favorable spot is located in the 59-60-57-55 well block in the northern part, and the secondary favorable spot is around the 53-62-49-45 well block in the northeastern part.

Key words: seismic attribute, dynamic weight coefficient, median method, coalbed methane, geological parameter, sweet spot