Estimation of correction coefficients for measured coal bed methane contents

Improving the accuracy and precision of coal bed methane (CBM) estimates requires correction of older data from older coal exploration surveys to newer standards. Three methods, the depth gradient method, the contour aerial weight method, and the well-point aerial weight method, were used to estimate the correction coefficient required to predict CBM gas content from coal exploration data. The data from the Nos. 3 and 15 coal seams provided the coal exploration data while the CBM exploration stages within the X1 well block located in the southern part of the Qinshui Basin provided the data obtained using newer standards. The results show the correction coefficients obtained from the two aerial weight methods are similar in value but lower than the one obtained from the depth gradient method. The three methods provide similar results for the Nos. 3 and 15 seams in that the correction factor is lower for the former seam. The results from the depth gradient method taken together with the coal seam burial depth and the coal rank suggest that variations in the correction factor increase linearly along with coal seam burial depth and coal rank. The correlation obtained can be applied to exploration and the evaluation of coal bed gas resources located in coalfields.