沁水盆地煤可磨性及其对煤层气排采的影响

Grindability of coal in Qinshui Basin and its influences on CBM production

为研究高阶煤地区煤可磨性特征,解决煤层气井煤粉伤害问题,采用哈氏可磨性指数测定仪对来自山西沁水盆地的11个矿的煤样品进行可磨性指数(KHGI)测定,并通过工业分析、煤岩组分测试发现同为高阶煤但可磨性差异较大。分析发现挥发分有利于煤可磨性,水分、灰分、固定碳均会使可磨性变差,其中水分的影响最大;煤变质程度越高煤可磨性越差,惰质组可磨性较镜质组好,原因在于惰质组在研磨过程中充当硬质"介质"的作用。以煤可磨性为切入点,阐述了煤层气井煤粉产出机理。煤层气井钻井遇煤段,产生钻屑的量及粒度与煤的可磨性正相关;水力压裂产生的煤粉量也与可磨性相关;排采过程中,由于排采流体的冲刷磨蚀,导致煤粉产出,可磨性是煤粉产出量的控制因素之一。可通过工业分析和煤岩组分分析,判定煤层井是否易于产出煤粉,为防控煤粉、制定合理排采工作制度及煤层气井开发可行性分析提供依据。

To study the characters of coal gringability in high rank coal region,and solve problems of coal fines in coalbed methane well,the Hardgrove Grindability Index Tester was used to test the KHGIindex of 11 coal samples from Shanxi Qinshui Basin,after proximate analysis and lithotype of coal test,found that the same high rank coal has different grindability. According to the results,volatile promote coal's grindability,moisture,ash,fixed carbon will reduce grindability of coal and moisture has the strongest influence on grindability;The higher the rank of coal is,the lower grindability is; Inertinite has better grindability than vitrinite,because inertinite in the grinding process can act as a kind of hard ' medium'. Based on grindability of coal,the genetic mechanism of coal fines of CBM well was briefly expounded. When drilling in the coal,the quantity and size of drilling cuttings and grindability of coal are positively related; the quantity of coal fines caused by hydraulic fracturing is related to the grindability; in the productive process,due to the fluid scouring abrasion,the pulverized coal outputs,grindability is one of the controlling factors of coal output. Through proximate analysis and coal rock components,it can be determined whether the well of coal seam likely produces coal fines. It helps to prevention and control coal fines,arrange reasonable working system and provides a basis for feasibility analysis of coalbed methane wells development.