Nozzle Cavitation and Rock Erosion Experiments Reveal Insight into the Jet Drilling Process

An in-depth process analysis of water jetting, a promising cost-effective drilling method for the exploration of geothermal reservoirs, is presented. The jetting process is analyzed under submerged and pressurized conditions by complementary high-speed shadow imaging, particle image velocimetry, and rock erosion analysis. The shadowgraphy and velocimetry experiments show that nozzle cavitation dominates the process, and it can be described by a modified cavitation number. Rock erosion experiments show that cloud cavitation governs material erosion. Thus, control of cavitation is essential for the jetting process.