DOI: 10.11799/ce202505009
Application of milling and fishing string technology for pneumatic directional drilling in broken soft coal seam
YANG Weifeng
FANG Jun
LIU Fei
LIU Jianlin
SHAO Guojie
CHU Zhiwei
Abstract：Drill pipe sticking is one of the main accidents in pneumatic directional drilling of broken soft coal seams.In response to the characteristics of such accident,a technical solution using gas sleeve milling and fishing string was proposed.A sleeve milling and fishing string technology for broken-soft coal seams was developed using nitrogen as the circulating medium,and a gas sleeve milling and fishing string tool assembly was designed.Based on the feedback of drilling conditions inside the hole,the key process parameters of sleeve milling and fishing string were optimized,and the passing ability of sleeve milling and fishing string in curved hole sections was calculated and analyzed.In Huayang No.2 Coal Mine,two incidents of pneumatic directional drill pipe sticking in broken soft coal seams were successfully handled.Practice showed that:using a combination of drilling tools with a diameter of 168 mm milling and fishing string can increase the slag discharge channel in the drilling annulus and improve the passing capacity of accident drilling tools;Adopting the drilling process parameters of"medium low weight on bit and medium low rotation speed"can effectively reduce the risk and improve the success rate of accident handling.The key finds offers reference for the handling of drilling accidents in broken soft coal seams.
Keywords：broken soft coal seamdirectional drillingdrill pipe stickingcasing milling and fishing stringdrill tool wear
Publication Date：2025-05-20
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：6( 64-69 )