Experimental Study on the Influence of Jet Dynamic Pressure Based on a New ConfiningPressure Control System

Zhou Shijie1LuWeiping'Liu Jiawei1Zhang Zheng1Zhu Ye1Luo Bin （1.JianghanMachineryResearchInstituteLimitedCompanyofCNPC；2.DownholeSeruiceCompany，CNPCChuanqingDrill ingEngineeringCompany Limited）

Abstract： To address challenges such as low operating eficiency and poor descaling effct in jet stimulation operation of deep/ultra-deep wells，the influence of downhole environmental pressre （confining pressure）on jet dynamic pressure has been studied at home and abroad.The confining pressure loaded in the previous study is mainly below 2O MPa，and the throtling method is used toadjust the pressure，which is inconvenientto control and the accuracy is not high. In this paper，a self-developed high confining pressure control system was used for simulation of higher confining pressure，achieving O＼～1Oo MPa stepless pressure regulation，and monitoring the jet dynamic pressure and confining pressure inreal time.Moreover，the experimental error possibly existed in the system was evaluated，and a preliminary testof confining pressre ≤55 MPa was carried out，verifyingthe feasibility of the new confining pressure loading system.The study results show that when the confining pressure is less than or equal to 10MPa ，the jet dynamic pressure decays significantly.As the confining pressure increases，the attenuation amplitude of jet dynamic pressure gradually decreases.The study results guide the jet operation of ultra-deep wells，and lay a foundation for further consolidating the jet attnuation characteristics under confining pressure and improving the theory of jet attenuation under high confining pressure.

Keywords： deep well; high speed jet；confining pressure;hydraulic control; impact pressure

0 引言

深层油气资源尤其是 8000m 以深超深层油气资源的高效开发，是保障我国能源增储上产的重要领域。现勘探开发最大井深超过 8800m ，地层压力最高超过 140MPa ，井口关井压力最高115MPa 。而随着深层油气井长时间生产，面临高压高产井堵塞后产量损失大的问题。采用高速射流进行井筒或油管内的清理作业，可实现快速解堵复产。根据现场作业实践经验，在深度超过 6000m 的井射流解堵作业过程中存在施工效率低、除垢效果差的问题。作业工程师们一直关注如何在井下复杂工况下提高水射流作业性能。深井的高围压环境是重要的因素，对射流性能的影响不可忽略，多年来学者们对射流特性进行了持续研究。

1988年，SHENZ.等通过试验研究了高压射流在到达井底之前的衰减规律，并提出了冲击压力半衰距离这一指标。1995年，艾池等[2]利用高围压射流动压测试装置开展了 10MPa 围压对射流动压力影响的试验研究，提出了围压 6MPa 范围内的射流动压不稳定段，围压状态下射流中的紊动流相似性和自模性依然存在。2009年，廖华林等[3采用水射流冲击压力测试装置进行了 0～ 10MPa 围压下水射流动力特征室内试验，研究认为，围压条件下射流动压降低导致了射流破岩能力降低。2013年，高晓东4研究了 0～10MPa 范围内围压对水射流冲击压力的影响，采用10、15、20MPa 喷嘴压降，研究发现射流轴向动压随围压升高先衰减后趋于恒定。2016年，李敬彬等[5使用同样装置分析了 0～10MPa 围压对射流冲击压力的影响，同时对该装置能否真实客观地反映井下围压环境提出了质疑。……