煤田钻探由于所钻煤系地层为覆盖层、砂岩、泥质砂岩、泥岩、含砾泥岩等水敏性造浆层和煤层，退心困难，尤其是水敏性造浆层更为困难。近年来，用泥浆泵退取岩矿心方法，既简单，又方便，效果良好。既节约了岩心管和钻头，又缩短了退心时间，一般一根4～5m长的岩心管，退心仅用3～5分钟，深受工人们欢迎。 Coal Drilling Due to the fact that the drilled coal strata are water-sensitive strata and coal seams, such as overburden, sandstone, muddy sandstone, mudstone and gravel mudstone, it is more difficult to withdraw from the heart, especially the water-sensitive strata. In recent years, using the mud pump withdraw rock core method, is simple, convenient, good effect. It not only saves the core pipe and bit, but also shortens the time for withdrawing the heart. Generally, a 4 to 5m long core pipe is only welcomed by workers for 3 to 5 minutes.