Discussion on the model of enrichment and high yield of deep coalbed methane in Yanchuannan area at Southeastern Ordos Basin

The production effect of the deep coalbed gas field in Yanchuannan area at Southeastern Ordos is better than expected,in which the No. 2 coal seam of the upper Permain Shanxi formation as the main coal seam is built and com- mercially produced, revealing that the deep coalbed methane has a great exploration and development potential. Through the systematic analysis of structural features,reservoir characteristics and controlling effects on the CBM en- richment and high-yield of the main coal seam,combined with the dynamic production data of the gas field,it is con- sidered that the model of deep CBM enrichment and high-yield in Yanchuannan area is gas content-permeability cou- pling control,of which in the primary fissure development zone with buried depth less than 1 000 m,it is self-generated plus self-storage type,while in the secondary fissure development zone with buried depth greater than 1 000 m,it is en- dogenous generated plus exogenetic-storage type. Upon this basis,the index system of deep CBM evaluation and selec- tion is established,then four favorable areas of gas enrichment and high-yield are optimized,which support for the fine drainage and stable production of the gas field,also provide reference for the exploration and development of other deep CBM areas.