Dynamic assessment of coalbed methane resources and availability in China

Under the frame of oil and gas resources assessment method system,the coal-bed methane(CBM) resources of 41 major basins(basin groups) containing CBM were evaluated by volumetric method. The quality,distribution and availability of CBM resources were analyzed. The results show that the original CBM in-place is 30. 05×1012 m3 in the coal layers with a burial depth of less than 2 000 m,of which 12. 50×1012 m3 is ultimately recoverable. The CBM re- sources are concentrated in 10 large basins such as Ordos,Qinshui and so on,which account for more than 85% of na- tional CBM resources. Resources are mainly distributed in Upper Palaeozoic and Mesozoic. The quality of resources is average. The main type is type II,followed by type I. There are great differences in the recoverability of CBM and limit- ed areas with good recoverability. Compared with the latest evaluation,the original CBM in-place has decreased by 6． 76×1012 m3 ,and the recoverable resources have increased by 1. 63×1012 m3 . It is mainly due to the increased relia- bility of gas content data and the changes in the understanding of buried depth. The reliable recoverable resources CBM is around 4×1012 m3 which have the conditions for development by ground technology. Several large basins have priority development conditions,such as Qinshui,Ordos,Eastern Yunnan-Western Guizhou and Junggar.