Coal Body Structure Research Articles

Deformed coal types and pore characteristics in Hancheng coalmines in Eastern Weibei coalfields

Based on SEM observance, the methods of low-temperature nitrogen and isothermal adsorption were used to test and analyze the coal samples of Hancheng, and pore structure characteristics of tectonic coals were discussed. The results indicate that in the same coal rank, stratification and crack are well developed in cataclastic coal, which is mostly filled by mineral substance in the geohydrologic element abundance, results in pore connectivity variation. Granulated and mylonitic coal being of these characteristics, as develop microstructures and exogenous fractures as well as large quantity of pores resulted from gas generation and strong impermeability, stimulate the recovery of seepage coal, improve coal connectivity and enhance reservoir permeability. Absorption pore (micro-pore) is dominant in coal pore for different coal body structure, the percentage of which pore aperture is from 1 to 100nm is 71.44% to 88.15%, including large of micro-pore with the 74.56%–94.70%; with the deformation becoming more intense in the same coal rank, mesopore enlarge further, open-end pores become thin-neck-bottle-shaped pores step by step, specific surface area of micro-pore for cataclastic coal is 0.0027m2/g, while mylonitic coal increases to 7.479m2/g, micro-pore gradually play a dominant role in effecting pore structural parameters.

Features of gas geology and its main controlling factors in Pingxiang mining area, Jiangxi Province

Pingxiang Mining Area in Jiangxi Province is one of the major coal-producing areas and is prone to serious coal and gas outburst, therefore, it is of significance to research on gas geological features and its controlling factors. Based on the analysis of gas data collected from geological exploration and coal mining, the research reveals that the features of gas geology vary significantly between west part and east part of Pingxiang Mining Area, and it is characterized by high gas mines with serious coal and gas outburst in the west part and low gas mines with no coal and gas outburst in the east part. The main controlling factors to gas geology are discussed, and the great difference of gas geology between west part and east part is the result of comprehensive effect by geological factors. Concerning the gas generation, the coal rank in the west part is higher than that in the east part, which is favorable to generate more gas in the west part than in the east part. Concerning the gas preservation, the structures are characterized by gliding nappe in the west part and by tectonic window in the east part, the surrounding rocks are characterized by poor permeability in the west part and comparatively good permeability in the east part, and the characteristics of coal rank and coal body structure are favorable to gas preservation in the west part and favorable to gas emission in the east part.

Gas parameter characteristic and region prediction in Erdaoling coal mine area

Abstract In accordance with the large amount of test data, a systematic study of the coal body structure and gas parameter characteristic of Erdaoling coal mine area is carried out. With single index method, gas content method and comprehensive index method, region predictions of coal and gas outbursts are conducted in major coal seams of the mine, which offers reference and guidance in improving the efficiency and pertinence of preventing gas outbursts.

Coalbed Methane Resources and Reservoir Characteristics of NO. II1 Coal Seam in the Jiaozuo Coalfield, China

Jiaozuo coalfield is located in the northwest of Henan province, China, and close to the Southern Qinshui coal basin, the most successfully commercial CBM resource developed area in China. The No. II1 coal seam is the main economic coal seam in Jiaozuo coalfield and its average thickness exceeds 5.36m. The maximum reflectance of vitrinite (RO,max) of the No. II1 coal across the Jiaozuo is between 3.16% and 4.78%. The coalbody structure of the No. II1 coal seam changes greatly in different part and can be generally divided into 1∼3 sub-layers. The micropores in the No.II1 coal seam is the major pores, secondly are transitional pores, and then less macropores and mesopores. The No. II1 coal seam has stronger adsorption, and the reservoir natural permeability has an evident heterogeneity vary from 0.0001 to 83.71mD. High permeability region is often near fault structure or the boundary of fault block. The CBM genetic type is homologous thermal cracking gas of humic coal with high matunity. Gas content with the burial depth of 163∼1070m varies very greatly from 4.65 to 45.75m3/t, with an average value of 18.3m3/t, and gradually increases from northeast to southwest. According to the latest evaluation for CBM resource in Jiaozuo coalfield, the existing total in-place CBM resources in the No. II1 coal seam with the depth of shallower than 2000 m are close to 1.2 × 1012m3, most of them mainly distribute in the depth of 1000 ∼ 1500 m. The existing total in-place CBM resources is dominated by the inferred CBM resource reserves (more than 70%), which distribute the undrilled places with few coal geological knowledge and deeper than 1000m. The resource concentration of the No. II1 coal seam in Jiaozuo coalfield is in the range of (0.513–3.478)x108 m3/km2, with an average value of 1.805×108 m3/km2. Based on the CBM resource investigation and reservoir evaluation, the most prospective target zones for CBM production in Jiaozuo coalfield include Guhanshan coal mine, Jiulishan coal mine and the west part of Qiangnan coal district.