Research On Occurrence Regularity Of Coal Bed Methane (CBM) In Hujiahe-xiaozhuang Coal Mine Field

The Hujiahe-Xiaozhuang coal mine field which is rich in gas is newly constructed.Researching the Occurrence Regularity of coal bed methane(CBM)is really necessary.Therefore,based on the materials of CBM exploration wells,the author systematic studied the Occurrence Regularity of CBM of research area.The results indicate that the Yan'an formation aquifer is located in the underground water area,the host condition is very poor.The major mined #4 coal reservoir shows the features of low porosity,good permeability,low pressure and strong adsorption.The coal reservoir is poorly altered and with low ability to generate the CBM,so the CBM is low,The coal field structure is generally high in southeastern and low in northwest wavy monoclinic structure.The formation is relatively simple,but after the deposition of coal formation,a number of tectonic movements occurred,so many times the coal-bearing strata were uplifted to shallow and weathering and erosion resulted in the majority of coal-bed methane escape.The development of coal-bearing basement paleo-uplifts in and around the coal-bearing strata also resulted in the CBM migration along the ancient weathering crusts to a certain extent.In contrast,the synclinal zone is more favorable to the preservation of CBM than the anticlinal zone.There are seven aquifers in the coal-bearing strata above the coal-bearing strata,and the hydraulic connection between the aquifers is weak.The Yan'an Formation is close to the CBM in the weak groundwater flow field,which is not favorable to the preservation of CBM.Based on the analysis of geological factors affecting the occurrence of CBM,the thickness of mudstone and siltstone and the thickness of 4 coal in the range from the top of the 4 coal to the Anding formation are the main factors affecting the methane enrichment in the study area.The results show that the main geological factors affecting the development of CBM are coal layer thickness and CBM content.The secondary control factors are CBM resource abundance,reservoir permeability,gas saturation,tectonic development and hydrogeological conditions.The research results are very valuable for mining the CBM and preventing the gas.