Low rank enrichment of coalbed methane in Hunchun basin

To obtain the industrial breakthrough of coalbed methane in Hunchun basin has great significance for the exploration of coalbed methane(CBM) in China's low rank coal basins. Through the deepened analysis on the reservoir-forming conditions of coalbed methane of low rank coal in Hunchun basin, the paper discussed the major controlling factors of CBM enrichment of low rank coal and its reservoir-forming model. The results show that Hunchun basin is characterized by low coal rank, multiple and thin seams. There are three main control factors for CBM accumulation, including tectonic setting, sedimentary characteristics and magmatic rock intrusion. The area with faults and folds in the west of the basin has not only created the favorable environments for biogas, but also provided the place for secondary reservoir forming, eventually forming the gas enrichment model of "continuous fold". The vertical superimposition of microfacies of marshes and natural levee which made mudstone and dense sandstone as the direct roof and floor of coal seams have better sealing effect for CBM, local diabase intrusion inside coal seams made again hydrocarbon to be generated, and greatly improved the physical properties of coal. Therefore, the west of Hunchun basin is an area rich in CBM and has a great potential for exploration and development.