Selection of strategic replacement areas for CBM exploration and development in China

At present, the increase in proved reserves and production of coalbed methane (CBM) in China depends mainly on several CBM bases in the southern Qinshui Basin and in the eastern margin of the Ordos Basin. Therefore, it is urgent to find new batches of exploration and development strategic replacement areas. For this purpose, we investigated the resources, reservoir properties, preservation conditions, and development conditions of CBM in China, and put forward eight general factors and four critical factors that can be used in establishing selection criteria of strategic replacement areas for affecting the CBM exploration and development in China. The eight general factors are resource abundance, coalbed thickness, gas content, original permeability, burial depth, hydrogeological conditions, coalbed depositional environment, and landforms, and the four critical factors include genetic type, stability type, later reservoir reformation, and damage degree of coal structure. Comparison shows that the low-rank coal area in the northwestern area, the northeastern medium-low rank coal area, and the southwestern medium-high rank and structurally-complex coal area are the major replacement areas for CBM following the northern area of China. Key factors affecting CBM enrichment in each of the three key areas, respectively, are: a) genetic type and stability of coal seams, b) genetic type and reconstruction of the reservoir by volcanic intrusion, and c) stability of coal seams and damage degree of coal structure. Based on these factors, a system for selection and evaluation of strategic replacement areas for CBM development was established. Fifteen blocks in the above three areas were evaluated by using multi-layered fuzzy mathematics, selecting eight favorable areas and seven relatively favorable areas that contain 1.8 trillion m3 of predicted CBM geological resources. The eight favorable areas include the Wucaiwan-Dajing coal exploration area in the Zhundong coalfield (eastern Junggar Basin), the Hami-Dananhu mining area in the Turpan-Hami Basin, the Longdong coalfield (eastern Gansu Province), the Yilan and Hegang coalfields in eastern Heilongjiang Province, the Hunchun coalfield in Jilin Province, the southern Sichuan coalfield, and the Shuicheng coalfield in Guizhou Province. These favorable areas were recommended to be the CBM exploration and pilot development target areas in the near future.