单相流煤层气井裂隙煤粉受力分析及启动条件

Force Analysis of Uniflow Coal-dust in Cracks of Mine for CBM and Starting Condition

为了准确地计算煤层气井出煤粉条件,基于煤层骨架煤颗粒受力,建立了煤层颗粒启动的力学模型。依据韩城煤田的资料,分析了煤层气井单相流阶段煤层骨架脱落颗粒大小与液体渗流速度、排液量以及压力差的关系。结果表明:在单相水流阶段,煤层气井煤粉产生与流体的渗流速度呈正向二次关系,当液体渗流速度大于该煤粉粒径的临界速度时,小于该颗粒粒径的煤粉将会脱落。从统计学观点,渗流速度越大,产生煤粉越多;排采中排液量越大,对煤层骨架拖拽作用越大,煤粉颗粒越容易脱落,当排液量在17m3/d以上时,大部分煤粉颗粒就会脱落。合理控制排液量在17m3/d以下有利于减少煤粉的产生。

For accurately calculating coal-dust starting condition in CBM mine, this paper set up mechanical model of coal grain initi- ation based on its force condition. It analyzed the relationship between size of uniflow coal grain in CBM mine and seepage velocity, liftingrate and pressure difference on the basis of Hancheng coal-filed data. Results showed that coal-dust starting was quadratic related with seepage velocity in uniflow phrase, and that coal-dust smaller than grain size would fall when seepage velocity was larger than lim- it velocity of coal-dust grain size. Seepage velocity was larger, more coal-dust appeared. Liftingrate was larger, its pulling action on coal body was larger and coal-dust fell more easily. When liftingrate was over 17m3/d, most coal-dust would fall. Controlling liftin- grate less than 17m3/d was benefit for reducing coal-dust.