Experimental study on evolution of pore structure in coal after cyclic cryogenic fracturing
Zhai Cheng
Sun Yong
Abstract：For the ineffective gas drainage in single low-permeability coal seam in China,the method of cyclic cryogenic fracturing coal is proposed.ln the process of cyclic cryogenicfluid injection,the coal freezes.Then the frozen coal thaws bv absorbing heat from surrounding coals.So the freezing and thawing cycles emerge in coal mass and the pore structure and permeability of coal will also be changed.The experiment which coal samples were treated by freezing and thawing in a total of 20 cycles was carried out.The nuclear magnetic resonance test was used to the coal samples.The evolution of pore structure characteristics at different freeze-thaw cycles was researched.The results show that the maeropores and fractures' proportion,the total porosity,the effective porosity,the permeability is rising with increasing freeze -thaw cycles.This proves that the pores of coal samples have bigger quantities,larger size and be more connected after multiple freeze-thaw cycles,so the pore-fracture network forms.Finally,the gas permeability of coal seam increases signifieantly.
Keywords：gas drainagefreeze-thawnuclear magnetic resonancepore structurepermeability
Publication Date：2017-01-01
Pages：6( 24-29 )