Study On The Preparation And Characteristics Of CO₂ Foam Fracturing Fluid For Mine

The total number of coal and gas outburst in China accounts for more than1/3 of the world's total outburst times.It is one of the most serious and dangerous countries in the world.With the continuous improvement of mining technology level in coal mines in China,some high gas mines also have prominent danger,and gas accidents show new characteristics:coal and gas outburst caused by gas explosion accidents are increasing.It is imminent to solve the problem of coal and gas outburst.Starting from the current research situation at home and abroad and the big background of the industry,this paper first introduces the multiple expansion and cracking mechanism of the CO₂foam fracturing fluid to the coal seam,which is the theoretical basis and the main conclusions are obtained by a series of experiments.?1?The half life,foaming volume and foam quality of four kinds of eight foaming agents were analyzed and contrasted in detail.The properties of the compound foaming agent and the original foaming agent were compared and analyzed in detail,and the compound scheme of NA and K-12 ratio of 6:4 was found.Its compound performance increased greatly,and its half-life increased from 439s to 899s.After cross linking experiments,the half-life increased from899s to 37540s.?2?The shear properties and rheological parameters of foam fracturing fluid under the concentration of different thickener were studied.The rheological properties and foam structure of foam fracturing fluid under different conditions were studied by dynamic simulation experiments.Finally,the optimal ratio scheme of foam fracturing fluid was obtained under the optimal experimental conditions.?3?The influence of foam fracturing fluid on coal is studied by BET specific surface and porosity measurement.It was found that the coal samples soaked by foam fracturing fluid decreased by 64.06%compared with the raw coal,and the adsorption capacity decreased by 51.26%.Its inhibition on the specific surface and adsorptive capacity of coal can desorb the adsorbed gas in the coal seam.?4?The influence of CO₂ foam fracturing fluid on coal is analyzed by Fourier in situ infrared spectroscopy.It is found that the content of free-OH in soaking coal is gradually reduced,and the coal sample is decreased by 50%compared with that of raw coal for 7 hours,and the content of hydrogen bond self association-OH is 20%lower than that of raw coal for 7 hours soaking.It was found that the length of soaking time reduced the hydroxyl content of coal samples to some extent,which made the coal sample more stable and less prone to redox reaction.The-CH₂ content of coal samples soaked for 7 hours is the lowest,indicating that the coal samples after soaking in foam fracturing fluid are shorter to some extent.It is concluded that when the soaking time is 1⁸ hours,the longer the soaking time is,the less likely the coal sample will be attacked by oxygen molecules,that is,it is more difficult to oxidize.