不同粒径煤样常压与带压解吸对比实验研究

Comparative experimental study of atmospheric pressure desorption and methane pressure desorption among coal samples of different particle sizes

为了研究煤储层内的带压解吸规律和不同粒径煤样在解吸过程中的差异,分别对取自沁水盆地晋城矿区寺河煤矿3#煤层的大块煤样和粒状煤样（粒径2～5cm）进行了等温吸附实验、常压（0.1 MPa,即1个大气压）解吸实验以及7个连续压降阶段的带压解吸实验.认为煤样内部的压降传递速度差异和煤储层本身的孔隙结构特征是造成不同粒径煤体降压解吸阶段迥异的主要原因.结果表明：相同温度、压力条件下,粉末状煤样（粒度60～80m,（mesh,180～250μm））吸附量是粒状煤样的1.20倍,是大块煤样的1.79倍;常压解吸条件下,粒状煤样的累计解吸量与相对累计解吸率分别是大块煤样的1.36,1.02倍;带压解吸条件下,粒状煤样的累计解吸量与相对累计解吸率分别是大块煤样的1.56,1.17倍.研究发现,不同粒径的带压解吸具有阶段性,其中前3个阶段大块煤样的累计解吸量以及相对累计解吸率均小于粒状煤样;后4个阶段大块煤样相对累计解吸率大于粒状煤样。

In order to study the rule of desorption under methane pressure and the difference among coal samples with different particle sizes during the desorption process in coal reservoir,experiments of bulk and granular coal samples（particle size 2—5cm）collected from No.3coal seam in Sihe Coal Mine,Jincheng mining area,Qinshui basin are conducted respectively,which consist of isothermal adsorption experiment,desorption experiment under atmosphere pressure and desorption experiment of 7consecutive pressure-step-down stages.This paper considers that difference of internal pressure drop transfer speed of coal samples and pore structure characteristics of coal reservoir itself are the main reasons for the distinction of different particle size coal pressure-step-down desorption stages.The results indicate that under thesame temperature and pressure condition,the adsorption capacity of powdered coal（the granularity of 60～80m,（mesh,180—250μm））is 1.20 times of 2—5cm granular coal while 1.79 times of bulk coal;during the process of desorption under atmosphere pressure,cumulative desorption quantity and relative cumulative desorption rate of granular coal sample is 1.36and1.02 times of the bulk coal sample respectively;while during the process of desorption under methane pressure,the sum of cumulative desorption quantity and relative cumulative desorption rate in each pressure-step-down stage of granular coal sample is respectively 1.56,1.17 times of the bulk coal sample.Research found that periodical characteristics were showed in the desorption process of different particle size coal samples under methane pressure,among which in the first 3stages cumulative desorption quantity and relative cumulative desorption rate of bulk coal sample were all less than those of granular coal sample;while in the last 4stages,relative cumulative desorption rate of bulk coal sample was less than that of granular coal sample.