Analysis of mechanical action between cone end of borehole packer and coal dregs in borehole and its application

Abstract

Analysis of mechanical action between cone end of borehole packer and coal residue in borehole is helpful to improve speed and depth of borehole packer movement by drag reduction effect of cone end. Firstly, on the basis of force analysis about cone end, the minimum thrust formula of cone end movement was deduced, and its correctness was verified by experimental research. Secondly, the lateral force of accumulated coal dregs was analyzed, and the drag reduction mechanism of cone end was revealed. Lastly, the thinking of cone end optimization was proposed, and borehole packer was improved, and field test has been carried out. The results show that the minimum thrust of cone end movement has a positive correlation with gravity of end, conical surface angle of end, maximum static friction coefficient between conical surface of end and coal dregs, height of accumulated coal dregs and cone base radius of end (there is a tangent function relationship between minimum thrust of cone end movement and conical surface angle). The cone end reduces the drag by reducing the thickness of accumulated dregs and the shear stress of accumulated dregs at the top of the contact surface. The improved hole packer can reduce resistance, increase feed speed and hole depth.

Keywords

• gas drainage drilling holes
• sealing device
• coal dregs
• accumulated coal dregs
• cone end
• drag reduction mechanism