高压电脉冲水力压裂法煤层气增透的试验与数值模拟

为了提高低渗透性煤层气的抽采效率,揭示高压电脉冲水力压裂技术对煤体产生裂缝的效果及裂缝的扩展演化规律,通过实验室试验,对煤样进行单纯静水压裂(3 MPa)和相同水压力(3 MPa)、不同放电电压(5,10 k V)条件下的高压电脉冲水力压裂试验,应用CT扫描技术分析了煤样内部裂纹的起裂、发展、分布情况;建立数值模拟分析水压电脉冲作用下裂隙的发展规律和裂缝周边的应力分布情况。研究结果表明:在相同静水压力作用下,高压电脉冲水力压裂煤层比单纯静水压力致裂效果明显;放电电压越高,在裂隙尖端产生的拉应力值越大,煤体易产生疲劳损伤破坏,裂隙易产生、易发展;放电电压越高,裂纹数量越多,裂纹的起裂时间更早,裂缝延伸长度更长,宽度更宽,致裂效果更好;可证明高压电脉冲水力压裂煤层方法有效,技术可行。

The experiment and numerical simulation of penetration of coalbed methane upon hydraulic fracturing under high-voltage electric pulse

In order to improve the efficiency of methane extraction from coalbed with low permeability，to reveal the effect of high voltage electric pulse on hydraulic fracturing in coal and the development of crack expansions，the laboratory tests of hydraulic fracturing using the high voltage electric pulse on coal samples were carried out under pure hydrostatic(3 MPa) and the same hydraulic pressure(3 MPa)，different discharge voltages(5，10 kV). CT scanning was employed to analyze the initiation，development and distribution of the internal cracks in coal sample. The numerical analysis of the development of fissures and the periphery stress around the fissures under the action of hydraulic electric pulse were carried out. The results show that under the same hydrostatic pressure，the effect of high voltage pulse on hydraulic fracturing of coal is greater than hydrostatic pressure fracturing. The higher the discharge voltage is，the greater the tensile stress in the crack tip is and the crack is easier to produce and develop. The higher the discharge voltage is，the more cracks there are，the earlier the crack initiation，the longer and wider the crack extensions are，and the better the crack fracturing effect. The results of the study proved that the high-voltage pulsed hydraulic fracturing method is effective and feasible.