Percussion-rotary method of drilling large-diameter dewatering wells in »Bełchatów« liginte mine

Abstract

Lignite opencast extraction can be performed after prior dewatering of the rock mass. Most frequently it is realized with large-diameter dewatering wells which have been mostly drilled with the invert mud rotary method and airlift. This method allows for quick drilling in lithologically diversifi ed aquifers, minimizing the negative impact of mud on the near-well zone. When drilling in dewatered carbonate rocks with the stone runs or well developed karst the effi ciency of this method considerably decreases. The technical and technological aspects of use of downhole hammers for drilling large-diameter dewatering wells in diffi cult geological conditions are discussed in the paper. Thanksto the use of this method for drilling wells in ‘Bełchatów’ Lignite Mine the drilling rate could be increased and the number of complications and drilling failures lowered.