Research On The Amount Of Liquid Filled Effect On Fracturing Outburst Elimination By Phase Transformation Of Liquid CO₂

Gas is the main threat to coal mine safety production in our country,and the gas drainage is the fundamental measures to prevent occurrence of gas disasters.Outburst coal seam in our country are mostly low gas permeability coal seam,the gas flow attenuation quickly,long elimination process,large quantity of drilling engineering and so on are seriously impact on mine pumping-mining-drifting balance.How to improve coal seam permeability and gas drainage volume is the key to realize the quick outburst elimination and ensure the pumping-mining-drifting balance.The fracturing by phase transformation of liquid CO₂ is a new antireflective technology in low gas permeability coal seam.this technology has the advantages of high safety,strong applicability and good antireflective effect,the amount of liquid filled is an important factor of fracturing effect by phase transformation of liquid CO₂.In this paper,through blasting pipe series connection to change blasting amount of liquid filled,both numerical simulation and field tests were adopted to study the amount of liquid filled effect on fracturing by phase transformation of liquid CO₂.Combined with the fracturing process and dynamic characteristics of coal to investigate the fracturing mechanism by phase transformation of liquid CO₂.The Pingdingshan mining area has characteristics of high gas pressure,high content and low gas permeability,apply the fracturing technology by phase transformation of liquid CO₂ are applied on seam antireflective,after the single fracturing by phase transformation,double pipe series connection fracturing by phase transformation and three pipe series connection fracturing by phase transformation,the drainage flow attenuation coefficient and seam permeability coefficient were tested,ensure the optimal amount of liquid filled is double pipe series connection fracturing.A fracturing model is established by the software COMSOL,the stress and strain around the borehole after fracturing under different distance between the releasing pipe were simulated,the simulation results showed that the optimal distance between the fracturing pipe is two meter,determined the relationship between coal thickness and the optimal amount of liquid filled.