The Tectonic Control On Gas Occurrence And The Gas Forecast In Changcun Coal Mine

Coal seam gas which is a geological gas, is the product of geological processes. The gas occurrence of today's coal seam and the geological conditions of gas outburst and gas emission are the results of complex geological evolution. Therefore ,it has great significance to do research on tectonic evolution and their effects on the control of gas occurrence.In this paper, the dynamics background of the Taihang mountains and its formation process were analyzed with the theories of the plate tectonics and the tectonic gradual control. The geological evolution histories of Qinshui Basin( the tectonic evolution, thermal evolution and hydrocarbon generation history of Shanxi Fm) were also analyzed. The regional controls the mining area in terms of tectonic structure. Accordingly, based on the large gas geological datas of Changcun coal mine, characteristics ,causes of minefield structural, and its control features on gas storage were studied. Gas geological units were defined in Changcun coalfield. Gas content and gas emission in each gas geological unit were forecasted finally. Conclusions were as followings: Under the control of the Jinhuo fault zone and the Wuxiang - Yangcheng fold belt in Qinshui depression axial region, the tectonic features varies from the NE, NEE normal faults in the east area to the NNE, nearly SN reverse faults and the folds in the west. In the process of the tectonic evolution, Lu'an tectonic structures underwent multi-stage transformation of tectonic stress field, as a result, the NNE ~ NEE fractures reversed to normal faults, forming a series of horsts and graben structures. Coupled with the rapid uplift of the Taihang mountains, the NNE ~ NEE faults became the main discouraged channels ,losing a lot of gas. However, because of the compression and the strong shear force, the NNW, nearly SN fractures released less gas, and controlled coal and gas outburst in the deep.In the east of Changcun coal field, the mian tectonic structures are the NNE ~ NEE faults and the ladder fault blocks, which controlled the gas occurrence; however, the nearly SN anticlines, synclines and reverse faults are the main tectonic structures,controling the distribution of gas and coal and gas outburst. Then, six gas geological units were defined, and lower bound of the 3# coalbed gas weathering zone were also defined. Combined with the measured gas content datas, the mathematical models of the gas content in every gas geological unit were established, determining the overlying rock thickness of coal seam is controlling factor of gas occurrence over the whole mine field. Gas content and gas emission in each gas geological unit were forecasted finally.May this study give scientific evidences to mining area and coal mine planing,, ventilation, coal bed methane extraction and utilization, coal and gas outburst prediction.