空化射流空化云形态变化规律和流场稳定性研究

高压水射流具有强力的冲蚀能力,在钻井工程中取得了良好的应用效果,而射流过程中会发生空化现象,该现象伴随着高温高压,是影响射流冲蚀能力的关键因素之一。喷嘴的结构对射流的空化发生能力有很大影响,分析空化射流流场特性和喷嘴结构之间的关系,是高压水射流射流研究的一个重要内容。本文采取可视化实验方案,用3D打印的风琴管式自振空化射流喷嘴,通过高速摄影技术,捕获喷嘴出口处空化射流流场特征,尤其是流场中空泡云的形态变化。并采取图像处理,分析了喷嘴结构改变对空化发生能力的影响。我们利用本征正交分解方法(POD)求取了流场结构的时均特征。通过对比不同喷嘴结构和射流水力参数下时均特征变化,分析了自振空化射流流场结构的稳定性差异。研究结果发现,喷嘴结构中谐振腔是影响空化发生能力的主要结构。在一定范围内增大谐振腔长度和直径有利于增强喷嘴的空化发生能力,并提高喷嘴出口流场结构稳定性。但谐振腔长度和直径过大会影响喷嘴自振效应,使流体经过喷嘴时难以形成共振,而使喷嘴空化发生能力骤降。喷嘴出口长度和扩展角在本文研究中最佳值分别为两倍出口直径和40°。研究结果表明,可视化角度直观明显,可以为其他优化方案提供验证和有力补...     

空化射流及其在钻井工程中的应用研究

空化射流是人为地将空化和空蚀作用引入水射流中而得到的一种新型高效射流，在相同条件下，它具有比普通射流强得多的清洗和破碎作用。简要介绍了空化射流的基本原理，主要介绍了空化射流的产生方式及其在石油钻井中的应用研究进展。     

空化水射流物理化学效应分析

空化水射流是射流流场某点压力降至饱和蒸汽压以下,伴随有气泡产生、长大和破灭过程的一种新型射流,空泡溃灭产生瞬间高温和高压现象,伴随有H^＋和OH^＋等强氧化物质的产生。利用高温、高压及微射流等物理效应,可以显著地提高射流清洗、除锈、破碎效果及改善金属表面性能的能力。通过机械剪切、热解、自由基氧化和超临界水氧化等化学效应,可以对毒性难降解有机物进行化学降解。空化水射流在石油、矿业及环保等领域具有广阔的应用前景。     

用于清洗除锈的淹没空化水射流喷嘴实验研究

为提高储油罐和输油管道清洗除锈的效率和安全性,探索空化水射流应用的新方式,设计了4种不同的淹没空化水射流喷嘴。采用冲蚀试件的方法,对4种淹没空化水射流喷嘴的冲蚀性能进行了实验,并与角形喷嘴进行比较,重点对内喷嘴入口压力和靶距两个关键因素进行了对比分析。研究结果表明:射流自喷嘴喷出后成白雾状,且伴随着刺耳的噪音,噪音表示空泡破裂的声音;提高内喷嘴入口压力可以有效提高喷嘴的冲蚀能力,由于空化效应的存在,4种淹没空化水射流喷嘴的冲蚀能力均强于角形喷嘴的冲蚀能力;在相同条件下,淹没空化水射流喷嘴外喷嘴收缩段流线型结构优于锥形结构,锥形结构优于圆柱形结构;靶距过大和过小都会影响射流的冲蚀能力,最优靶距与喷嘴的结构有关,所设计的淹没空化水射流喷嘴的最优靶距在30~40 mm之间。该实验研究对储油罐和输油管线清洗除锈具有借鉴意义。     

常压下淹没自激空化喷嘴的试验研究

本文概述了自激空化射流的原理和自激喷嘴的设计方法;并在常压下进行了淹没自激空化水射流冲蚀人造岩芯的试验研究。重点研究了风琴管喷嘴的腔室底部形状、出口喉部厚度和出口扩散角对射流冲蚀性能的影响,得出了有规律性的结果。同时在不同泵压、不同喷距的条件下对所设计的喷嘴射流轴心压力脉动作了测量。结果表明,风琴管喷嘴的射流压力脉动大于锥形喷嘴的射流压力脉动,且压力脉动的规律和破岩规律有密切的关系。     

空化射流及其在钻井破岩中的应用前景

空化射流在地面低环境压力下已经获得了广泛的应用，但是在地下高环境压力下的应用却遇到了一定的困难。为此，阐述了空化现象和空化射流研究简史、空化形成的机理、检验空化生成的方法和影响空化的因素；讨论了传统上用于判断射流是否空化及空化程度的空化数的合理性,结果为用空化数不能判断射流的空化状态，流场中具有绝对压强小于或等于汽化压强的区域是射流空化的必要条件。针对空化射流比普通射流破岩能力强的问题，分析了Rayleigh空穴湮灭冲击压强计算公式存在的问题，给出了空化射流中的流体质量脉动引发作用在岩石表面上的压强脉动是导致岩石破坏的主要原因的理论解释。应用自振射流喷嘴能提高油气井钻进速度的原因不是射流空化，而是脉动的射流在岩石表面产生的脉动压力。在分析深井钻井的高温、高围压等特殊环境和空化形成机理后，认为空化射流应用于深井钻井很难。     

文丘里管水力空化发生器数值模拟

对水力空化现象及水力空化的形成进行了较为全面的综述,针对文丘里管内的空化现象进行数值模拟,并研究了进口压力、下游恢复压力、喉部收缩率对空化效果的影响。结果表明:进口压力越大,空化效果越明显;下游恢复压力越小,空化效果越明显;喉部收缩率越大,空化效果越明显。     

角形空化喷嘴内外流场的数值模拟

为研究角形空化喷嘴对空化射流空化效果的影响,建立了空化喷嘴内外流场的数学模型和物理模型。利用流体力学模拟软件FLUENT,采用混合模型、空化模型和RNGκ-ε湍流模型对角形空化喷嘴的空化射流内外流场进行了数值模拟。以射流流场中含气率分布为判断喷嘴产生空化效果的依据,分析了直柱段直径、入口压力、围压对射流空化效果的影响。模拟结果表明:相同喷嘴入口压力条件下,直柱段直径越大,射流空化效果越好;增大喷嘴入口压力可以提高射流空化效果,但围压的存在会抑制空化泡的产生,不利于提高空化效果。数值模拟结果可以为空化射流的产生提供指导。     

微颗粒强化射流空化及破岩能力研究

深井、超深井钻井面临地层强度高、机械钻速慢等挑战，利用射流空化作用辅助破碎岩石为深井提速提供了新方向。为此，提出了利用微颗粒降低空化临界负压，提高空化强度的技术思路。采用高速摄影和水听器，证实了微颗粒对射流空化的强化作用，并通过冲蚀破岩试验探索了微颗粒直径、质量分数及喷距对空化射流破岩能力的影响规律。研究结果表明：微颗粒的存在可提供额外的空化核，同时降低了空化初生难度，可提高井底射流的空化强度；随着微颗粒质量分数的增加，空泡云趋于稳定，空化的周期性特征逐渐消失，微颗粒的磨蚀作用和空泡的冲蚀作用将在岩石表面共同形成辅助破岩效果；随着喷距增大，空化破坏作用先增加后减小，无因次喷距为100时空化射流冲蚀效果最佳；优化设计钻头水眼到井底岩石的距离，是保障空化射流辅助破岩效果的关键。研究结果可为提高深部难钻地层射流辅助破岩效率提供参考。     

自振空化射流提高钻井速度的实验研究

空化射流用于提高钻井速度的可行性研究结果表明，在钻进作业中，利用空泡破裂产生强大破坏作用来提高钻探的效率，其效果显著，可行性高。室内实验表明，自振空化射流在比普通喷嘴射流更深的井底或更高的围压条件下，有更大的起始空化数和更强的空化能力。自振空化喷嘴起始空化数大都在1.0以上，最高达到1.67，而锥形喷嘴最高仅为0.43，围压下其冲蚀效率是锥形喷嘴的1~2倍。现场试验同样证实设计的自振空化射流喷嘴在保护钻头、减少钻头磨损及增加进尺、提高机械钻速方面有显著作用。     

自振空化射流钻头喷嘴研制及现场试验

在风琴管谐振腔模型的基础上，给出了自振空化喷嘴的设计模式。用硬质合金为主要材料研制出了石油钻井用自振空化射流喷嘴。现场试验表明。自振空化喷嘴钻头与普通中长喷嘴钻头相比，钻井速度提高10．5%～49．3%，平均机械钻速提高31．2％．钻头进尺也相应增加29．1％。自振空化射流喷嘴具有广泛的应用前景。     

高压水射流理论及其在石油工程中应用研究进展

近年来新型水射流理论研究及其在石油工程中的应用进展主要包括：①自激振荡射流调制机理研究，创制了新型高效自振空化射流，发明了自激振荡射流钻头，首创了自振旋转射流处理近井地层解堵增产增注技术和自激波动注水技术。②机械及水力联合破岩理论研究，揭示了在钻井压入与旋转双向应力作用下，岩石裂纹形成和发展规律，建立了联合破岩钻头设计理论。③旋转射流理论和破岩机理研究，研制了径向水平钻井技术。①磨料射流特性和参数影响规律研究，优化了水力喷砂射孔参数设计，发展和完善了水力喷砂射孔技术。⑤高压水射液深穿透水力射孔及辅助压裂可行性研究，不仅可以提高射孔和压裂效率，而且为油田(特别是低渗透油藏)增产增注提供了一种有效方法。⑥双射流理论及其特性研究，双射流有利于形成大而深的破岩孔道，避免孔眼凸底的形成。可以提高射流破岩钻孔效率。⑦探索超高压射流辅助破岩理论及辅助钻井新方法，建立了超高压射流辅助破岩的三维PDC钻头模型。参18     

Mechanisms and field test of solution mining by self-resonating cavitating water jets

Rapid solution mining is the key to cavern construction in salt formations. Rapid solution mining technology with self-resonating cavitating water jets is described in this paper. It can generate three main physical effects: helical flow dissolution, self-resonating cavitating jet erosion, and ultrasonic waves. A self-resonating cavitating nozzle was also designed with the principles based on theory of fluid transients and hydro-acoustics. Under ambient pressure, the experimental results show that the impulse amplitude of pressure reaches a peak at a standoff distance of 5–13 times the nozzle outlet diameter and the cutting ability of self-resonating cavitating jets is twice that of conventional jets under the same conditions. Compared with the conventional mining method, the field test indicates that rapid solution mining technology with self-resonating cavitating jets can speed the construction by more than 2 times at the pocket stage of cavern development.     

Investigation and Application of Self-Resonating Cavitating Water Jet in Petroleum Engineering

The paper presents the investigations of a unique jet as self-resonating water jet including the modulating principles, characteristics of impact pressure and rock erosion, and field applications in petroleum engineering in China. The research showed that jet nozzles designed with organ pipe structure could generate significant self-resonating cavitating water jets. As compared with conventional cone-shaped nozzle with 120° taper angle, the amplitudes of pressure fluctuation and maximum impact pressure of self-resonating cavitating water jets increase by 24 and 37%, respectively, and rock erosion efficiency increases by 1 to 2 times. Self-resonating water jets have been successfully applied in petroleum drilling engineering, with enhanced average rates of penetration of tricone bits by 31.2% and improved bit footages by 29.1%. Treatment of near wellbore formation and self-excited oscillating water injection with self-resonating water jets have resulted in economic efficiency.     

CURRENT STATUS AND FUTURE PROSPECTS OF WATER JET TECHNOLOGY IN PETROLEUM ENGINEERING IN CHINA

ABSTRACT

This paper reviews the developments of investigation and application of high pressure water jet technology in both deep drilling and oil production including jet-bit drilling, extended nozzles and their combination to enhance hydraulic effectiveness at bottomhole, combined jet and mechanical drilling, new efficient jets (self-resonating cavitating jet, self-excited oscillation jet, swirling jet) used in drilling, horizontal well drilling by water jet, near wellbore plug removal with water jet, and high pressure water jet penetrating. Laboratory investigation and field application have coherently shown that high pressure jet drilling can increase the penetration rate. The hydraulic power of rock bit with extended nozzles and with crossflow hydraulics can increase by 30～40 percent, the bit footage by 40 to 50 percent and dynamic pressure by 90 to 110 percent compared with conventional bit. Combined jet and mechanical drilling can increase drilling rate by a factor of 3 in deep wells than conventional drilling method. New efficient jets can improve the penetration rate of bit with 20 to 60 percent higher, owing to the enhanced cutting and cleaning action. High pressure water jet drilling system can be used to drill multiple ultra-short-radius (0.3 m) radial horizontal wells at the same level without tripping the whipstock. Near wellbore plug removal with hydraulically rotating and pulsating water jet can increase oil production by 20 to 50 percent and increase water injection by 30 to 90 percent. New penetrating system by using high pressure water jet cutting can produce unobstructed radial tunnels with 3 meters in length and 14-25 mm in diameter information rocks and can be used in new well completions, recompilations, and workovers of older wells to enhance the production and injection efficiency. The paper shows the brilliant prospects of development and application of water jet technology.     

CURRENT STATUS AND FUTURE PROSPECTS OF WATER JET TECHNOLOGY IN PETROLEUM ENGINEERING IN CHINA

This paper reviews the developments of investigation and application of high pressure water jet technology in both deep drilling and oil production including jet-bit drilling, extended nozzles and their combination to enhance hydraulic effectiveness at bottomhole, combined jet and mechanical drilling, new efficient jets (self-resonating cavitating jet, self-excited oscillation jet, swirling jet) used in drilling, horizontal well drilling by water jet, near wellbore plug removal with water jet, and high pressure water jet penetrating. Laboratory investigation and field application have coherently shown that high pressure jet drilling can increase the penetration rate. The hydraulic power of rock bit with extended nozzles and with crossflow hydraulics can increase by 30∼40 percent, the bit footage by 40 to 50 percent and dynamic pressure by 90 to 110 percent compared with conventional bit. Combined jet and mechanical drilling can increase drilling rate by a factor of 3 in deep wells than conventional drilling method. New efficient jets can improve the penetration rate of bit with 20 to 60 percent higher, owing to the enhanced cutting and cleaning action. High pressure water jet drilling system can be used to drill multiple ultra-short-radius (0.3 m) radial horizontal wells at the same level without tripping the whipstock. Near wellbore plug removal with hydraulically rotating and pulsating water jet can increase oil production by 20 to 50 percent and increase water injection by 30 to 90 percent. New penetrating system by using high pressure water jet cutting can produce unobstructed radial tunnels with 3 meters in length and 14-25 mm in diameter information rocks and can be used in new well completions, recompilations, and workovers of older wells to enhance the production and injection efficiency. The paper shows the brilliant prospects of development and application of water jet technology.     

自振空化射流改善油层特性实验研究及现场应用

自振空化射流是具有强烈压力振荡和高空化起始能力的新型射流,利用高压釜装置对围压下自振空化射流提高污染岩渗透率进行的实验研究结果表明,对中、低和高渗透率岩样,空化射流作用深度均超过250mm,渗透率提高率随射流压力的增大而增加,随喷距的增大而减小;当围压值为2MPa时,渗透率提高率达到最大值.同时,在相同条件下,自振空化喷嘴作用下渗透率提高率为锥形喷嘴作用的2倍以上.现场应用效果证明,自振空化射流对解除油层和水层堵塞有明显效果.     

围压对射流破岩特性影响的试验研究

围压是石油工程中影响射流动力学特性的重要参数之一。应用高压井筒模拟试验装置进行了围压对常规连续射流、空化射流和磨料射流破岩效果影响的试验，最高围压达到20MPa。试验结果表明，围压对常规连续射流和空化射流破岩效果影响明显，破碎体积随围压的增大而减小，减小的速度随围压增大逐渐变缓；而对获得最大破碎体积的最优喷距影响不大，为3～5倍喷嘴直径，说明围压对射流基本结构特性影响不明显。当围压小于15MPa时，磨料射流射孔深度随围压的增大而近似呈线性减小。该试验可为射流参数的优选提供依据。