Based On The High Voltage Electrical Hydraulic Fracturing Of Coal Seam Gas Crack Anti-reflection Effect Research

Low permeability of coal seam gas extraction is at present our country coal mine gascontrol and exploration technical problem.The method of artificial gas layers of coal androck structure transformation,increase fracture, and the strength of weakening is aneffective way improve permeability.On the basis of the borehole hydraulic fracturing,bythe pressure on electrical load,using high voltage pulse discharge in the hydraulic fracturetip formation water shock and vibration effect to change the gas occurrence environment,promote the transformation of state adsorption to (free) process,and increase thepermeability of coal seam,and improve the efficiency of gas drainage. High voltage pulsedischarge technology is a successful application in oil and gas layer mining,but the storageof gas occurrence conditions,physical and mechanical properties and coal seam have greatdifferences.Introducing the technology to prevent coal seam gas outburst and gas drainage,there are a lot of problems for further study. This paper mainly completed the followingseveral aspects:1) Launched by ultrasound scans of time, the drilling of coal sample in7kV dischargevoltage and3MPa under the pressure of the12MPa pulsation pressure made by coalsample produce250mm throughout the bedding surface crack. With the increase ofdischarge voltage, to develop the main crack, micro cracks form and with the maincrack.Discharge voltage for11kV, transverse crack extension to the surface of specimen,micro cracks and the main crack basic is full of the coal sample.2) Theoretical analysis of the influence of in-situ stress of coal and rock mechanicalproperties and in-situ stress under the action of shock wave and pulse water coal and rockfailure process, and the ideal conditions of coal rock drilling crack positions are analyzed.By test in the process of the crack position, the role of high voltage electrical pulse watershock wave makes drilling radial maximum tangential stress and tangential stress tensilemake radial location first crack and crack extension. 3) By RFPA2D-FLOW software, to simulate the coal sample under actual stresscondition, the simulation process of the water pressure increasing continuously, which isdescribed by acoustic emission coal sample fracture of the main crack and thedevelopmental process of micro cracks, and ultrasound scanning and test results. Incomparison,the traditional hydraulic fracturing technology,coal sample to produce themain crack when18MPa,12MPa hydrostatic pressure can only be formed extender, andhigh voltage electrical pulse12MPa pulsation pressure produced by hydraulic fracturingtechnology has internal coal samples produced throughout the bedding surface crack.4) By ultrasonic nondestructive testing methods and the results obtained in the processof simulation, evaluation of high voltage electrical hydraulic fracturing technology to crackeffect and application prospect of coal samples, and advantages and problems to overcomewhen the high voltage electrical hydraulic fracturing technology is applied to the actualproject.