Franck Rey-Bethbeder

A new formula for predicting the amplitude of the dynamic pressure wave resulting from breakdown in water gap

The study is part of a global research program concerning the development of an alternative electrical stimulation technique for conventional hydraulic fracturing in tight gas reservoirs. More precisely, the goal of this work is to predict the shock wave amplitude induced by an electrical breakdown in water. The influence of the gap length enhancement on the peak pressure improvement will be shown, and the major importance of improving the electrical circuit maximum current will be demonstrated and accompanied by the development of a new empirical formula directly relating to maximum pressure and maximum current. Furthermore, we point out the fact that the frequency spectrum of the shock wave depends from the speed of current injection into the water gap. These results will allow the optimization of the electric fracturing technique by increasing the electro-acoustic yield.

Corona discharges experiments in water and transition to subsonic discharges

This paper discusses the influence of the discharge current on the compressive shock waves generated by supersonic and subsonic discharges in water gap. The two different ways leading to dielectric breakdown in a water gap will be investigated. The transition phase between the two breakdown modes depends on the electric field and the electrical energy switched. The shock waves associated to breakdowns in water gap will be studied. Whatever the water breakdown mode will be, the peak pressure linearly depends from the peak current. For a constant peak current, the peak pressure value increases with increasing gap length. Moreover, the electro-acoustic efficiency is better using a supersonic discharge.