An Experimental Study of Using Plasma Shock Wave for Rock Damage

Abstract

Plasma shock wave (PSW) has been proven to be able to destroy rocks and improve the ROP for conventional rotary drilling. The aim of this paper is quantify the damage caused by PSW generated by different discharge energies, and to study the mechanism and characteristics of PSW damage to rocks. The PSW has been extensively used in many areas, such as alternative fracturing. In the tests, the PSW reactor generated the electrohydraulic effect to convert electrical energy into mechanical energy, which was sufficient to destroy the hardest rock. Firstly, the experiment was carried out using concretes instead of real rocks. Secondly, three types of discharge energy were used to generate PSW to damage samples. Finally, the amplitude attenuation coefficient (AAC), the damage variable and the drillability were used to quantitatively analyze the damage of the samples. Experimental results showed that samples were impacted to produce many circular holes and cracks and the damage to samples increased as the energy increased. However, when the energy rose to a certain extent, there was a gradually decrease in the growth rate of damage. In addition, it was found that the AAC measured at different locations was different for the same sample, which indicated that the internal damage of a concrete sample produced by the PSW was anisotropic. Finally, the average drillability was improved after the sample was subjected to PSW impact. The findings gained will help understand the mechanism by which the PSW destroys rocks It also provide some methods to quantitatively evaluate damage of rock.