Research of rock fracturing based on high voltage pulse in shale gas drilling

Based on the electro-hydraulic effect, rock fracture experiments were conducted on the artificial rock samples and the real sandstone samples. A pulsed power supply with a stored energy of 40 kJ/20 kV was developed. Experimental results show that large multi-fractures could be generated, the maximum length of the fracture in the vertical direction was 0.32 m. The shape of the fracture is related to the stored energy, the discharge voltage, the discharge times and the rock mechanical parameters. The 3-D morphology analyzer was used to observe the surface configuration of the fracture. The fractures have no obvious tortuosity in the near borehole area, and all the fractures generated by the pulsed discharge have certain average roughness in the range of 0.430-1.075 mm, which are capable of forming conductivity ability.