Evaluating the fracture resistance and drainage difficulty of coal reservoirs using log data

Evaluating the fracture resistance and drainage difficulty of a coal reservoir is essential in the coalbed methane (CBM) industry. In this study, the coal body structure and brittleness indices, as well as the difference coefficient of coal stress, were calculated for coal reservoirs in the Hancheng Gas Field in the Ordos Basin using log data, coal core testing analysis, and dynamic testing data, and a prediction model of the completion quality index was constructed on the basis of the results. In addition, a CBM drainage model was established after analyzing the intrinsic relationships between CBM drainage and the influencing factors. The evaluation criteria of the fracture resistance and drainage difficulty were determined using the indices of the coal reservoir completion quality and water yield. The results showed that the technology fully considers the influences of the completion quality and water yield during CBM production. The evaluated data are in good agreement with those reported in the actual production of CBM.