Fine Description Of Coal Reservoir And Analysis Of Its Influencing Factorsin Eastern Yunnan

Laochang mining and Enhong mining are important coal-producing areas in the eastern Yunnan Province,which are one of the important coalbed methane(CBM)enrichment areas in China.In order to describe the coal reservoir characteristics and its primarycontrolling factors in the area,this paper analyzedthe coal quality characteristics on the basis of the previous studies combined with a series of experiments such as scanning electron microscopy(SEM),microscopic identification and industry analysis.Moreover,tthe characteristics andinfluencing factors of the coal reservoir were analyzed systematically via nitrogen physisorption,isothermal adsorption and NMR.The main conclusions are as follows:(1)The micro composition and industrial analysis showed that all the samples-are semi bright coal and semi dull coal,and most of them are semi bright coal,because the organic matter in coal seam is dominated by vitrinite.The ash content of Laochang mining is slightly less than the Enhong mining's.The ash content of the upper part is generally larger than that of the lower's for both of the minings.The sulfur in coal is mainly inorganic sulfur.(2)Low temperature nitrogen physisorption showed that the pores in the study area are mainly micropore and small pores.The small pores and mesopores contribute more than 70% of the pore volume,and the micropores contribute more than 50% of the specific surface area.The nitrogenadsorption–desorption isothermscan be divided into three groups.In different locations of same reservoir in Laochang mining,the curves are quite different,especially 7# coal,showing that the pore structure of some coal reservoirs in the study area is quite different.(3)By nuclear magnetic experiment,the atlas of samples are divided into three types: adsorption pore connected type,adsorption pore block type,and seepage pore fracture development type.The ratio of the effective and residual porosity to the three types of atlas is: 40%,60%;20%,80% and 75%,25%,respectively.The development of seepage holes and fissures in coking coal in Enhong mining is much better than that of anthracite in Laochang mining.(4)The gas content of the coal reservoir in the Laochang mining is higher than that of Enhong mining area.The CBM in the Enhong mining area has the characteristics of moisture.In Laochang mining area,the correlation between gas content and buried depth is better than that of Enhong mining.The Langmuir volume of coal reservoir in Laochang mining is greater than that of Enhong mining area,showingthat the adsorption ability is better than Enhong mining.The gas content of the coal reservoir in the study area increases with the increase of the degree of metamorphism of the coal.(5)Adsorption experiments and low temperature nitrogen physisorption of Laochang mining showed that the Langmuir volume of 2# coal is less than 7# coal,however,the BET surface area and BJH total pore volume of 2# coal are greater than those of 7# coal,indicatingthat the content of super micro pores in 7# coal is more than 2# coal.(6)The development of fracturesin coal reservoirs is mainly influenced by structure.Pore development is closely related to the coal quality of coal reservoir.