Abstract: This method uses a simple relationship to compute total raw coal seam (coalbed) desorbed gas volumes from geophysical logs in a well bore. Laboratory total measured raw coal seam gas desorption volumes on coal core samples are calibrated to geophysical log measurements to obtain the relationship. The relationship has different constants and exponents for coal seams in each geologic basin and depositional setting. The calibrated relationship is applied to geophysical log measurements in cored and non-cored coal seams of the same type in the same basin to obtain a continuous total gas desorption volume estimate over the entire well in order to compute natural gas reserves in place. The method can be applied to coal seams where appropriate geophysical log measurements are available in any well.