自推进喷嘴井筒内流场数值模拟

摘要

Taking the self-propelled nozzle used in deep penetrate horizontal drilling as the object, wellbore flow field numerical simulation under different back nozzle holes arrangements of self-propelled nozzle was obtained byk−ε two equation turbulence model according to the model and bore hole diameter. The results show that a swirl is formed between two adjacent jets because of pumping effect of back nozzle jet within the wellbore. The swirls may be blockers or promoters to bottom regurgitation based on different positions. Besides, the back nozzle jet can also be an accelerator to the bottom regurgitation. Along wellbore radial direction, the flow velocity of the swirl zone increases from wall to nozzle, which aggravates erosion of the nozzle and high-pressure hose. After changing quantity of the back nozzle hole from 3 to 6, the swirl area is only 25% of the one before the improvement, and swirl velocity has a 6 m/s drop at most. These falling indexes indicate that the quantity changing can make full use of characteristic of the swirl zone and jet flow itself, and they can improve the self-propelled nozzle rock carrying efficiency and increase working life.%以深穿透水平钻孔自推进喷嘴为模拟对象，根据模型和实测井眼建立流场模型，采用标准k−ε双方程模型，对不同后喷孔布置下的自推进喷嘴井筒内流场进行数值模拟。研究结果表明：井筒内，由于后喷孔射流的抽吸作用，2个相邻射流之间会形成一个漩涡区，该漩涡由其发生位置的不同，可对井底返流形成阻碍或卷吸加速作用；后喷孔射流本身对井底返流有加速携带作用；沿井筒径向，漩涡区速度由井壁向喷嘴处逐渐增大，这将加剧喷嘴和高压软管的冲蚀；将后喷孔由3个均布改为6个均布，改进后喷嘴射流形成的漩涡区面积只为改进前的25%，且漩涡区速度降低最多达6 m/s，充分发挥了射流本身和漩涡区的特点，可有效提高自推进喷嘴流场的携岩效率，延长其使用寿命。