Study on the coal seam permeability increasing technique based on hydraulic cutting and CO2 fracturing

According to the limitation of the single coal seam permeability increasing technique, the gas-liquid two-phase comprehensive action coal seam permeability increasing technique was put forward, including CO2 fracturing technique and hydraulic cutting technique. The principle and process of the gas-liquid two-phase comprehensive action were studied, the low pressure drilling process, the high pressure cutting process and the CO2 fracturing process were confirmed. The permeability increasing effect testing programs of the gas-liquid two-phase comprehensive action were designed.The field tests showed that the average mixed amount of the gas extraction reached to 12.80 m3/min after the gas-liquid two-phase comprehensive action, which was 9.41 times than that of the average mixed amount before permeability increasing.The average absolute amount of the gas extraction reached to 9.53 m3/min after the gas-liquid two-phase comprehensive action, which was 14.44 times than that of the average absolute amount before permeability increasing.The permeability increasing effect of the gas-liquid two-phase comprehensive action were higher than the single permeability increasing technique effect, the gas-liquid two-phase comprehensive action permeability increasing technique provided a new technical means for coal seam permeability increasing.