Characteristics of coal reservoirs and favorable areas classification and optimization of CBM planning blocks in Guizhou Province

The scientific evaluation of favorable CBM blocks concerns the deployment of CBM exploration and development and the maximization of benefits. On the basis of the existing geological and engineering data, the geological background, resource characteristics, occurrence characteristics and reservoir characteristics of CBM are studied in the 18 blocks with unregistered mining rights in Guizhou Province. According to the principle of coal rank classification and evaluation, the optimum block among the 18 blocks is selected by using the multi-level fuzzy comprehensive evaluation method. The results are as follows. (1) The coal seams of Longtan Formation in the 18 planning blocks of Guizhou Province are formed in the marine-continental transitional sedimentary environment. With relatively complex tectonic conditions, a wide range of coal rank variations, and obvious regional characteristics of coal reservoirs, they are characterized by the development of thin-medium thickness coal seams, high gas content, high reservoir energy and low permeability. (2) The method for the classification and optimization of favorable areas of medium- and high-rank CBM is established. 15 evaluation parameters are selected based on the different methods and principles of different CBM evaluation index systems. The weights of parameters are obtained by the analytic hierarchy process, and the membership function of each parameter is established. The scores of evaluation samples are determined by the fuzzy comprehensive evaluation method, and then the comprehensive evaluation coefficient is obtained. (3) By using the coefficient, three favorable areas, five sub-favorable areas and nine backup areas are identified, among which, Dahebian syncline block of medium-rank CBM, Zhaozihe syncline north block, and southern section of Dafang anticline block of high-rank CBM are favorable areas for CBM exploration and development. The evaluation results provide support for the overall and orderly deployment of CBM exploration and development in Guizhou Province in the future.