Research of rock fracturing based on high voltage pulse in shale gas drilling
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摘要: 基于液电效应原理，采用高压电脉冲放电对模拟岩样及实际砂岩岩样进行了压裂实验研究。脉冲电源最大储能40 kJ/20 kV，放电电流最高可达70 kA。实验结果表明，高压电脉冲能够在岩样中造成非常明显的裂缝，可以在多个方向上造出多条具有一定高度（最大0.32 m）的裂缝，近井筒裂缝无明显的扭曲，裂缝的形态与放电电压、能量及放电次数有关。对模拟岩样压裂后产生的裂缝进行了三维形貌分析，得到裂缝的表面平均粗糙度在0.430~1.075 mm之间，具有一定的导流能力。Abstract: 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.
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Key words:
- electro-hydraulic effect /
- pulse discharge /
- rock fracturing /
- 3-D morphology analysis /
- roughness
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