Abstract
Hydrajet fracturing could be a promising technique for increasing hydrate production; however, the pressure distribution law inside the perforation tunnel must first be investigated. This study established a two-dimensional axisymmetric model of the submerged water jet, employing the shear-stress transport k - ω turbulence model, to analyze the pressure distribution. The study examines the impact of various factors on pressure distribution, including well completion, perforation tunnel root diameter, hole diameter on the casing wall, nozzle diameter, nozzle pressure drop, confining pressure, and jet distance. Results reveal that the pressure inside the perforation tunnel exceeds the confining pressure due to jet flow, resulting in pressurization within the erosion tunnel, unaffected by the confining pressure. As the perforation tunnel root diameter increases, the pressurization drops sharply in a parabolic manner in both open hole and uncemented casing completion wells. For cemented casing completion wells, the pressurization is dependent solely on the hole diameter on the casing wall, and the perforation tunnel root diameter has no influence. As the nozzle diameter expands, the pressurization increases exponentially, with a more pronounced effect in open-hole conditions. The pressurization rises linearly in proportion to the nozzle pressure drop. In open-hole wells, a larger nozzle diameter leads to a greater linear increase. For uncemented casing completion, the rate of linear change first increases and then decreases as the hole diameter on the casing wall increases. As the jet distance increases, the pressurization first rises and then falls. The optimal jet distance for maximizing pressurization in open-hole wells decreases with increasing nozzle diameter. In uncemented casing completion wells, increasing the distance between the nozzle and the casing leads to greater pressurization. The results provide theoretical support for the application of hydraulic jet fracturing technology in hydrate extraction.