The Characteristics Of Coal Facies In The Permian Coal Seams In The North Of Pingdingshan And Its Control Of Coal Pore Characteristics

As a fossil energy,coal is formed by ancient plants through coalification.The composition of coal is affected by the coal-forming environment and has a great influence on the pore characteristics of coal.In this paper,18 samples of four coal seams in three mines in Pingdingshan area were selected for macroscopic feature analysis,quantitative analysis of coal micro-components,the vitrinite reflectance analysis,coal ash composition analysis,total sulfur analysis,proximate analysis of coal and other experiments on the coal-forming environment.Based on multi-angle analysis,combined with low-temperature liquid nitrogen experiments and high-pressure mercury injection experiments,the pore characteristics in different environments were analyzed.The main conclusions are as follows:(1)Through the analysis of the constant elements in coal ash,it can be found that the entire coal seam in the study area belongs to the sea-land transitional facies environment.Although the environmental background is similar,it can be divided into:(a)shallow-water covered forest peat moor,(b)wetland herbaceous moor,(c)shallow-water covered wetland herbaceous moor,(d)moist forest peat moor,and(e)low peat moor five coal facies,.The regular appearance of different coal facies in the coal seam indicates that the coal-forming environment in the same coal seam may change during the coal-forming period.(2)Parameters such as porosity,specific surface area,and average pore diameter with the diameter range(5.5nm～100μm)obtained from high-pressure mercury injection experiments show different trends in different coal facies.The change in porosity is e> a> d> b> c;the change trend of pore volume is e> a> d> c> b;the change trend of specific surface area is e> a>c> d> b;the change trend of average pore diameter is b> a> e> d> c.From the data of nanometer pore size(1-170nm)obtained by nitrogen adsorption method,the change trend of BET specific surface area between different coal phases is e> b> d> a> e;the change trend of DFT pore volume is e> d> a> b> c.(3)Based on the relationship between the coal-forming environment and the coal pore characteristics,it is found that the action of groundwater,the degree of marsh wetness and the degree of reduction in the coal seam in the study area play the most important role in the coal pores,and the characteristics of coal-forming plants have little effect on the coal pores in this area.