Research On Timeliness Of Influence Radius By Liquid CO₂ Phase Transition Fracturing Technique

Liquid CO₂ phase transition fracturing technique is a new type of coal seam permeability increasing technology,which belongs to the physically high-pressure gas blasting and with the advantages of no spark blasting process,convenient operation,safe and efficient,it can be well used in high gassyand low permeability seam.In this paper,we combined with the field test of strengthening pre-fracturing by liquid CO₂ phase transition fracturing technique in Pingdingshan No.13 Mine,investigate the influence radius of liquid CO₂ phase transition fracturing and studied the efficiency of influence radius.Firstly,we introduced the development of liquid CO₂ phase transition fracturing technique and equipment.Analysed the fracturing process of anti-reflective,and studied the coal unloading anti-reflection principle According to blasting dynamics and fracture mechanics theory to study blasting gas effect on the tensile fracture of the rock,analysis the changes in peripheral crack mechanics field.The power of liquid carbon dioxide phase transformation induced by the use of the compressed gas storage tank to calculate the liquid carbon dioxide is equivalent to 277 g TNT.Secondly,based on the field test of No.13 coal mine,investigated the effects of wear layer of gas drilling drainage by using this technology.Measured the influence radius of the phase transition of liquid carbon dioxide.According to field test drilling gas drainage parameters,using the different changes of the gas extraction before and after fracturing,the flow attenuation coefficient of drilling hole is changed from0.0637d-1to 0.0095d-1after fracturing.The attenuation coefficient of gas flow decreased85.09%.After fracturing,the permeability coefficient of coal seam has been changed to0.577m2/?MPa2·d?by using the radial flow method.It is sixty times higher than before the cracking.Finally,establishing the model of the influence radius of the liquid CO₂ phasetransition fracturing induced cracking according to Darcy law,seepage equation,Langmuir adsorption equation.Combined with the numerical simulation software of Comsol Multiphysics,the article get the effective influence radius of the test Roadway after crack and variation characteristics of gas pressure at different distance from thedistance to the borehole.By comparing the field test results,the effective influence radius of the liquid CO₂ phase transformation in the test tunnel of the thirteen coal mine is determined by 5m.There is a negative exponential relationship such as0.00375.11 5.11 tR e-?28?-?10?between the effective influence radius and the pumping time.Furthermore,this paper also studied the effect of permeability coefficient and phase transformation on the radius of pumping and mining.Through the research,the selection of the phase change fracturing pressure should be in a reasonable range.Through the time characteristic research of the influence radius of the crack and the influence radius of pumping and mining,it lays a foundation for the study of the technological parameters of phase transformation of liquid CO₂.