Hydraulic slotting technology could achieve regional stress-unloading,permeability-increas-ing and efficient gas extraction in the low-permeability coal seam through creating artificial fractures u-sing the high-pressure water jet.Unfortunately,the three-dimensional pressure-relief gas migration field in the hydraulic slotting coal mass could not be solved by adopting the typical COMSOL software,which seriously restricts the field application of hydraulic slotting technology.Given this,the FLAC31-COM-SOL combined numerical solution technology was adopted in the research to analyze the three-dimen-sional pressure-relief gas migration fields in medium thick coal seam under different slotting radii,slot-ting thicknesses,buried depths and slotting manners,respectively.The following conclusions could be obtained from the numerical simulation results.A stress-unloading and plastic damage occur in the coal mass during the hydraulic slotting process,the plastic damage zone presents a circular platform shape,and the coal permeability increases by 2～3 orders of magnitude.The coal's permeability-increasing range and amplitude both increase with the slotting radius and the slotting thickness,but increasing the slotting radius is much more conducive to the stress-unloading,permeability-increasing and gas extrac-tion in the medium thick coal seam.The high in-situ stress in the deep coal seam could not only de-crease the coal permeability,but also increase the permeability-increasing range and the amplitude in the hydraulic slotting coal mass,therefore the borehole's gas extraction effect is much better in the ear-ly stage and the gas extraction period should be decreased by improving the borehole density during the field application process.Slotting manner has a great influence on the overall pressure-relief gas extrac-tion effect in the coal seam:the pressure-relief gas extraction effect is the best under the condition of single slotting drilling parallel arrangement,and the next is the single slotting-staggered arrangement,followed by double slotting interval arrangement,the worst.
关键词
低透煤层/水力割缝/卸荷损伤/瓦斯抽采
Key words
low-permeability coal seam/hydraulic flushing/stress-unloading and permeability-increas-ing/gas extraction
维普
万方数据