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Jixi basin is one of the important coal basins in China. To explore the gas accumulation characteristics and its geological controls, it’s important for further exploration and development of coalbed methane (CBM). The gas content of Jixi Basin is high viable from 4.78 to 11.94 m3/t, indicating high gas content in the north and west but low gas content in the south and east. The further analysis results show that the delta plain and lake are favorable sedimentary environments for coal accumulation. The Chengzihe and Muleng formation are formed in these environments. Moreover, massive magmatic intrusion heat activities and subsequent continuous subside of strata increase coal rank of the coals. In the area of Pingma reverse fault and the area with thick Muleng formation, mud seals are favorable for CBM preservation. In these areas, CBM is sealed and accumulated by hydrodynamic condition. Finally, a comprehensive evaluation model for CBM was found. Based on the evaluation model, the most favorable zone for CBM exploration is forecasted to be J idong depression.

This paper discusses the structural characteristics and tectonic evolution, as well as the accumulation history and preservation conditions of coalbed methane (CBM) in Zhengzhuang block located in southeastern Qinshui basin. Deformed by the Hercynian, Indo-China, Yanshan and Himalayan four tectonic movements, the study area emerges the structure pattern that folds developed in northwest of the block, while faults in the southeast. The area near the syncline axis is the favorable region of CBM accumulation with good sealing condition. The Sitou fault has an effect on the diffusion of CBM. The geological controls of gas accumulation were concluded by a conceptual model, which provides a basis for further exploration and development.

Southern Shizhuang Block has simple structure characteristics, relatively thick coal seams (3.1-10.5 m, 6 m in average), and favorable burial depth (450-900 m). The gas content of the No.3 coal seam in the Shanxi formation ranges from 6-20 m3/t, and it increases from the southeast to northwest area in the southern Shizhuang Block. Gas content is high in the structural low in the area, which means the gas accumulation is controlled by the geological characteristics of local structure and hydrogeologic conditions.

This paper discusses how sedimentary controls on accumulation of coal and coalbed methane in Hancheng CBM field. Two major coal-bearing strata include the Upper Carboniferous Taiyuan formation (a marine and terrestrial sedimentation) and the Lower Permian Shanxi formation (a terrestrial sedimentation). The favorable sedimentary environments for accumulation of coalbed methane by decreasing order are the shallow marine and barrier island system, the delta system, and the shallow marine and plane coast system.

For finding out favorable coalbed methane development districts, the evaluation of geological controls of CBM distribution and accumulation is essential during CBM exploration and development. In this paper, the No. 3 coal seam in the Zhengzhuang coal zone located at southern Qinshui Basin, China, was selected as a focus for comprehensively evaluating geological controls of CBM. The findings of this study are: (1) Coalbed gas contents increase with increasing mudstone roof thickness (ranging from 0-9 m), and will always be as high as 20 m3/t in the coal reservoirs with the mudstone roof thickness greater than about 9 m. (2) The weak transmission and stagnant coalbed water are favorable for CBM accumulation in coal reservoirs resulting from the typical hydraulic preservation of CBM. (3) High coalbed gas contents will commonly occur in vitrinite-rich and low-ash yield coals with high CH4 adsorptive capacity.

The Late Paleozoic coalbed methane (CBM) reservoirs for high-rank coal in North China have the characteristic of high CBM content. But due to the differences between CBM reservoirs in several aspects such as physical property and gas accumulation condition, CBM was developed for commercialization only in the south of Qinshui Basin. Coal samples were systematically collected from Qinshui Basin, Jiaozuo Coalfield, Yongxia Coalfield and Xinggong Coalfield, and then tested on coal petrology, porosity-permeability characteristics and isothermal adsorption, etc. Based on the analyses of these test data, this paper discusses the forming conditions and mechanisms of the favorable CBM reservoirs for high-rank coals. These factors like the coal petrology characteristics, reservoir physical property and gas accumulation conditions were detailedly discussed. The difference characteristics of the favorable CBM reservoirs in North China were comprehensively evaluated as conclusions. The result shows that in comparison with other high-rank coal areas, coals in Qinshui Basin have undergone slight tectonic destruction, which induces the widespread development of primary- and cataclastic-structured coals, developing better microfractures. Moreover, the Qinshui coals have not only the well-developed exogenetic fractures, but also well sedimentary and tectonic conditions at the key accumulation period of CBM. These factors resulted in the formatting of better CBM reservoir in Qinshui Basin when comparing to other high coal rank areas in North China.