径向钻井高压水射流喷嘴内外流场分析

径向钻井高压水射流技术目前在国内外得到了广泛应用。对射流喷嘴内、外流场进行数值模拟分析将为选择合理的喷嘴结构以及为高压水射流破岩的进一步研究奠定基础。根据射流动力学原理,建立了单喷嘴轴对称淹没射流破岩的物理模型和数学模型,运用Fluent软件对径向钻井高压水射流喷嘴内、外流场进行了数值模拟,并分析了在不同喷距和入口流量下喷嘴内、外流场的规律。分析结果表明,射流轴线上存在速度衰减性、圆柱段速度保持性和最大速度偏移性;当射流冲击到径向井底后,在井底壁面上产生水垫,对喷头的推进产生阻碍作用;在径向钻井高压水射流中会产生滞止现象,将不利于钻井过程中岩屑的快速移运。

Analysis of the Internal and External Flow Fields of High Pressure Water Jet Nozzle in Radial Drilling

The technology of high pressure water jet in radial drilling has currently been used widely at home and abroad.A numerical simulation and analysis of the internal and external flow fields of jet nozzle will lay the foundation for the further study of selection of rational nozzle structure as well as for high pressure water jet rock breaking.According to the jet dynamic principle,the physical and mathematical models of axial-symmetrical submerged jet rock breaking with single nozzle were established.A numerical simulation of the internal and external flow fields of high pressure water jet nozzle in radial drilling was conducted with the Fluent software.The laws of the internal and external flow fields were analyzed in different jet distances and inlet flowrates.The analysis shows that there exist velocity attenuation,velocity retention in the cylindrical section and migration in the maximum speed.When the jet flow impacts into the radial hole bottom,the water cushion will occur on the bottomhole wall surface.This will produce a barrier to nozzle advance.Stagnation will arise in high pressure water jet for radial drilling.This will be unfavorable to the transportation of cuttings in the drilling process.