Abstract
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Radial jet drilling technology (RJD) is an economical and efficient technology for the development of unconventional oil, gas, and geothermal resources. The self-rotated multi-orifice nozzle, which is the key for the hole-forming, is introduced and tested here. Its sandstone-breaking characteristics are researched by experiment, the influence of working conditions, lithology, axis length, jet pressure (15 ~ 40��MPa), and standoff distance (0 ~ 10��mm) is also studied. Moreover, optimal working parameters for continuous drilling are proposed. Results show that the self-rotating multi-orifice nozzle can effectively drill a large circular hole whose diameter is about 30��mm under the condition of fixed standoff distance or continuous feeding. The submergence conditions are helpful to improve rock breaking efficiency. The short-axis nozzle has good hydraulic performance and rock breaking ability. Uniaxial compressive strength affects rock breaking diameter, while permeability affects rock breaking depth and volume. The rock breaking diameter, depth and volume of sandstone both increase with the jet pressure. The rock breaking diameter increases with the standoff distance, while the rock breaking volume and depth are opposite. The diameter of the rock breaking hole decreased with the augment of the feeding speed. For the sandstone here, the jet pressure is recommended as 35��MPa and the feeding speed 0.03��m/min (1.8��m/h); laterals with a diameter of about 30��mm can be formed. The research results are expected to promote the development of RJD technology.