喷射钻井中风琴管空化射流提速规律分析

ANALYSIS ON HOW ROP INCREASED BY ORGAN-PIPE CAVITATING JET IN JET DRILLING

为准确掌握风琴管空化射流在喷射钻井中的提速规律,通过数值模拟的方法分析了空化射流流场特性,探讨了围压对其空化能力及速度脉动能力影响规律,采用真三轴高围压射流破岩规律模拟实验装置开展了空化射流破岩模拟实验,研究了静液注压力对射流破岩效率影响规律,并对比了一定静液注压力下空化射流与常规射流破岩效率。结果表明,在现有机泵条件下,风琴管空化射流可以直接或间接的实现钻井的提速提效。

In order to accurately understand how the ROP increased by the organ-pipe cavitating jet in jet drilling,the characteristics of cavitating jet flow field were analyzed by numerical simulation,and the influence of ambient pressure on cavitation and velocity pulse effects was discussed.A group of simulation experiments were carried out on rock breaking by cavitating jet using the self-developed true tri-axial loading simulation device under high ambient pressures.The influence of ambient pressure on rock breaking efficiency of jet was studied,and the rock breaking efficiency of cavitation nozzless and conventional nozzle under certain ambient pressure was compared.Finally,the limit depth of cavitating jet in jet drilling was discussed by theoretical analysis.The results showed a strong correlation between rock breaking efficiency and the characteristics of cavitating jet.The cavitating jet had the limit depth.When the depth was less than the limit depth,the organ-pipe cavitating jet had obvious cavitation which could directly break the rock.When the depth was greater than the limit depth,the cavitation was obviously suppressed by ambient pressure,and the rock breaking produced was similar to that by the conventional jet.However,better cuttings removal was observed,an indirect rock breaking was made.The results showed that with existing pumps and equipment,the organ-pipe cavitating jet could directly or indirectly improve the drilling speed and efficiency.It was economical and efficient.The analysis herein has established a foundation for the precise application of the organ-pipe cavitating jet in jet drilling.