偶极子声波测井在套管井中的声场特征*

偶极子声波测井在套管井中的应用越来越多,本文重点研究了套管井不同胶结状况下偶极子声源在套管井中激发的声场特征,通过解析方法分析了水泥环第一界面和第二界面不同胶结状况下井孔模式波的频散和衰减。计算结果表明,在水泥环第一界面或第二界面胶结差时井孔声场中可观测地层弯曲波和套管弯曲波;与胶结良好时相比,地层弯曲波的频散曲线向低频偏移,水泥环第二界面胶结差时偏移较大;套管弯曲波对水泥界面存在的流体环厚度很敏感,随着流体环厚度的增加套管弯曲波的相速度逐渐增大,激发幅度也明显增强,这一特征为利用套管弯曲波的相速度估算流体环厚度提供了可能。本文的计算结果为利用套管井中越来越多的偶极子声波测井资料评价水泥胶结质量奠定了理论基础。     

相关固井质量的声波测井仪器刻度和标定*

目前,中海油服已经建成了一批用于固井质量和套损检测的刻度井,刻度井群可以物理模拟不同的套管规格、水泥密度以及不同的水泥胶结状况等,可用于实现对固井质量和套损检测的声波测井仪器进行系统的标定和测试。以刻度井群中用于标定仪器在高密度和中密度水泥套管井中测量性能的应用为例,介绍了依据高精度的超声扫描、数值模拟和实际仪器的测试结果,初步实现对固井质量检测中常用的声幅-变密度测井(CBL/VDL)和扇区水泥胶结测井(SBT)仪器进行定量刻度和标定的步骤和方法。研究工作表明,质量测试可以掌握刻度井中各组成部分的声学物理参数以及胶结质量,在此基础上结合数值模拟和实际仪器的测量响应,可基本实现待测仪器工作性能的标定。     

固井工艺对过套管电阻率测井影响的数值模拟

过套管电阻率测井响应信号十分微弱,增强测量信号幅度对提高仪器测量精度、改善视电阻率计算结果的精确性具有重要意义;建立全空间有限厚度纵向、径向阶跃地层模型,针对近地表段为低阻、中阻和高阻三种地层模型,在MATLAB7.0环境下数值模拟分别得出了近地表段有/无水泥环封固条件下,套管上一、二阶电位差的分布;分析上、下供电模式下电位差分布特点,总结了近地表段水泥环对测井响应的影响,给出了不同地层条件下近地表段水泥封固的建议。     

泄漏Lamb波在固井质量评价中的应用

轻质水泥在油气田固井中的广泛应用使得传统声阻抗测井方式难以准确地对固井水泥胶结质量作出评价。本文基于弯曲型Lamb波传播特征对层状介质胶结质量较为敏感的特点,首先对套管井建立合适的层状介质模型,计算了层状介质的平面波反射系数,从反射系数的角度探讨了在套管井内激发弯曲型Lamb波的条件。然后依据该条件并结合声波角谱理论计算了稳态有限宽脉冲束入射时在套管井内产生的弯曲型Lamb波泄漏波的时间波列信号。通过对泄漏波波列信号的分析,得到了弯曲型Lamb波与套管井水泥胶结质量间的关系。研究表明,入射声波在满足一定条件下可以在套管内激发弯曲型Lamb波,其传播时的衰减率与套管水泥胶结质量以及水泥的声学参数均相关,当水泥为轻质水泥或者普通水泥时,其衰减率随着套管水泥间水层厚度的增加而减小,当水泥为快水泥时,其衰减率随着水层厚度的减小而增加,但当水层厚度减为零即套管水泥胶结良好情况下,其衰减率转而变小。     

套管井中偏心对声场的影响分析*

目前在油田的实际应用中,声幅-变密度水泥胶结测井(CBL/VDL)在套管井的水泥胶结质量评价中发挥重要作用。但是,在一些大斜度井或者水平井中,往往由于仪器或者套管的重量等原因导致套管井中出现偏心现象,这给利用声波测井资料进行水泥胶结质量评价带来一些难题。为此,本文建立了套管偏心和仪器偏心两种情况下的三维声学模型,利用柱坐标系下的三维交错网格有限差分算法数值模拟了两种偏心情况下的声波传播情况,并着重研究了偏心率的变化对套管井中声场波形特征,尤其是套管波及地层波特征的影响。另外,模拟了具有不同外径尺寸的套管和偏心率的组合情况下的声场传播情况,在此基础上研究了偏心率的大小对声场特征的影响规律。本文的研究结果表明,套管偏心和仪器偏心均会给声场波形特征带来影响,且随着偏心率的增加而增大;相比较而言,仪器偏心对套管波的影响更大。     

套管中模式波的响应特征*

在固井质量评价中主要利用套管中模式波的幅度或衰减变化反映水泥的胶结状况,不同测井仪器在套管中激发的模式波的类型不同,研究套管中各模式波的传播特征和影响因素可充分挖掘测量数据的潜在应用价值。CBL和SBT等测井仪器在套管中主要激发拉伸波,类同于平板中的零阶对称Lamb波,水泥环封隔测井仪器的斜入射模式在套管中主要激发套管弯曲波,类同于平板中的零阶反对称Lamb波,垂直入射模式激发套管共振波,类同于平板中的高阶对称Lamb波。该文重点分析了这些模式波的衰减特征及其对微环的响应,套管弯曲波在套后耦合轻质水泥时对微环不敏感,但在套后耦合常规水泥或重水泥时,其衰减明显高于胶结良好的状况;拉伸波对微环的存在最为敏感;套管共振波对微环不敏感。     

弯曲型Lamb波传播特性与固井质量相关性研究

轻质水泥在油田固井中的广泛应用使得传统测井方式无法有效的对固井水泥胶结质量做出评价。为了研究新的可行的评价方法,本文采用传递矩阵方法对套管中传播的弯曲型Lamb波进行建模,并通过对所建模型进行数值计算研究了套管外水泥等介质的声学参数变化对弯曲型Lamb波衰减率的影响。数值计算的结果表明,弯曲型Lamb波的衰减率与水泥的声学参数以及水泥与套管的胶结状况有较强相关性,据此可对水泥与套管胶结状况进行评价。本文的计算结果与分析对弯曲型Lamb波在水泥胶结评价中的应用具有一定的参考意义。     

含气孔裂隙地层的声波测井响应特征

本文以径向分层的孔、裂隙地层多极子井孔声场理论为基础,利用孔、裂隙介质弹性波动统一理论,数值模拟了井壁上有侵入时,单极和偶极声源激发的井孔声场随原状地层含气饱和度变化的特征和规律。结果表明：当原状地层裂隙发育时,相较于饱含水,饱含气时纵波幅度衰减严重,横波波至提前,波幅增大,斯通利波幅度变化不明显,低频时弯曲波到时提前,幅度增大;当原状地层裂隙不发育时,单极子、偶极子波形都对流体性质没有明显响应。可见,原状地层中裂隙的存在加剧了含气对纵波、横波的幅度以及到时的影响,而侵入带的存在使得斯通利波和高频弯曲波对原状地层流体性质变化不敏感。数值计算结果为利用声波响应特征识别致密气层提供了参考。     

软地层随钻测井仪器偏心情况下低频四极子源 激发波场的数值分析*

为了探索测井仪器偏心对随钻低频四极子波场的影响,利用有限元法(多物理场耦合有限元软件包)对软地层井孔中随钻仪器偏心情况下低频四极子声源激发的波场进行了数值模拟。通过对随钻四极子测井波形的分析可知,当采用低频随钻四极子偏心声源激发时,测井波列中除传播速度与低速地层横波速度相当的地层四极子波模式外,还存在一个幅度非常低、传播速度略高于井孔流体中声速的模式波,该模式被对应钻铤弯曲波模式,且该模式波的幅度随着随钻四极子源偏离井孔中心距离的增大呈二次方规律增大,地层四极子模式波幅度呈三次方规律增加。     

超声脉冲窄带激励的水泥环第二界面探测方法*

如何评价水泥环的第二界面固井质量一直是声波测井领域的世界性难题。本文利用有限元方法研究了基于超声脉冲反射法的水泥环第二界面固井质量探测方法。数值模拟了不同声源脉冲宽度及不同声阻抗地层对第二界面超声反射回波的影响。研究结果表明采用窄带的激励信号源可有效的提高水泥环第二界面反射波回波幅度,有望解决水泥环第二界面固井质量评价问题。制作了水泥环第二界面具有胶结缺陷的实验室样品及大型固井质量刻度井,在此基础上开展了基于窄带超声脉冲激励的实验室及刻度井群实验研究。实验结果表明满足水泥环第一界固井质量良好条件,采用窄带的超声脉冲回波技术可有效评价水泥环第二界面固井质量。     

Application of cylindrical linear phased array in casing borehole

An Ultrasonic Phased Array （UPA） transducer is presented for borehole imaging and casing inspection in acoustical logging. First, a Cylindrical Linear Phased Array （CLPA）, which is made up of numbers of piezoelectric elements distributed on the surface of a cylinder uniformly, is designed and fabricated. By transmitting and receiving acoustic waves using different groups of elements under the control of the electric system, the CLPA can gcan all area of the borehole wall dynamically and rapidly. Then the radiation and reflection acoustic fields of the CLPA are investigated theoretically in the casing borehole with defects. Finally, the experimental researches about ultrasonic scanning and imaging for the casing boreholes with defects have been conducted by the CLPA transducer. The experimental results consist well with the theoretical ones.     

Response of a cylindrical machine casing to oscillatory bearing forces

An analytical model is developed for the vibration response of a cylindrical machine casing excited by the force arising in a bearing that is assumed to support a rotating shaft. The casing system consists of a bearing housing mounted in a flat circular end cap that is built into a cylindrical casing. The housing is considered to be a rigid trunnion in the center of the end cap (which itself is modeled as a Mindlin plate). The development allows for arbitrary location of the center of mass of the housing and of the plane of action of the exciting force.     

Numerical investigation of the casing treatment mechanism with a single circumferential groove

The paper investigates the effect of a single circumferential groove casing treatment(CGCT) on a transonic compressor rotor numerically.In particular,the effect of the groove at different axial locations on the flow field is studied in detail and stall margin improvement is also discussed.The present results show that the groove close to the leading edge plays a crucial role in stabilizing the near stall flow structures and,hence,improves the stall margin.The groove at the mid-chord-section of the blade can help exchange and transfer momentums between different directions,and suppress the flow unsteadiness,leading to increased efficiency in rotor performance and extended operation range.The groove located near the blade trailing edge has limited effects on stall margin improvement and may cause additional penalty in efficiency.Through comparison with the recent work on CGCT,some common flow physics can be observed.     

The effects of cement density and pipe dimension on casing waves in oil wells

The acoustic field in a cased hole is studied through numerical modeling by combining experiment measurement when the first and scond interfaces are bonded well.The effects of the density of the cement,the diameter and thickness of the steel pipe on the amplitude of casing arrival(ACA) are investigated,and a part of the numerical results are compared with the experimental results.These results show that the ACA decreases with the increasing density of the cement.There exists a large difference between the ACAs for the low-and normal-density cements.Therefore,the different standard should be taken in the bonding evaluation for cements with different densities.As the thickness of the steel pipe increases while its diameter keeps as a constant,the arrival time of the casing wave remains unvaried,while the ACA increases. But,when the diameter of the pipe with a constant thickness increases,the arrival time of the casing wave is delayed,and the ACA decreases.As for three kinds of the steel pipe commonly used in oilfields,the relative amplitude of the casing arrival is larger in the big pipe. In addition,the numerical results of the varying trend of the relative amplitude of the casing arrival with the density of cements,on the whole,are in agreement with the experimental ones.     

宽带相控线阵声源在套管井外地层辐射声场的指向性

套管井中的声传播涉及到波在柱状多层介质中的传播问题。通过数值计算对比了宽带相控线阵声源在套管井外均匀地层中产生的纵横波声场的指向性。结果表明,在任意胶结状况下,均可实现向套管井外地层定向辐射纵横波的技术;与地层中纵波的传播特征不同的是在主瓣偏转角方向横波幅度随着偏转角的增大逐渐增加,且在主瓣辐射方向的横波幅度受套管井胶结状况的影响较纵波小;采用玻璃钢套管代替钢套管,会进一步减弱地层声场受胶结状况的影响,这有利于实现在套管井外地层较大范围内的精确定向辐射声波的技术。     

On blade/casing rub problems in turbomachinery: An efficient delayed differential equation approach

This paper presents an alternative pathway in studying the ubiquitous blade/casing rub problem in turbomachinery. Bladed disks interfere with the stationary shroud (casing) for a variety of reasons, such as axial offsets, thermal expansions. Both components being compliant, time-varying interface characteristics, nonlinearities and uncertainties in the rub forces make this dynamics very complex to model and analyze. The main idea in this paper originates from the conjecture that this dynamics is inherently akin to internal machining operation which also deals with compliant cutters (blades) but relatively more rigid workpiece (casing). This analogy directs our attention to the fact that the blade/casing impingement dynamics manifests a ‘regenerative mechanism’ which is impregnated with time delays. The ensuing time-delayed system (TDS) can be stable, which is ideal. If it is unstable, however, the interference amplitudes between the blade and the casing grow, and the nonlinear effects become dominant. If the components survived the exercise, this evolution would reach a limit-cycle behavior. Existing literature indicates that this limit cycle mode is the common state of operation in most modern-day turbomachinery. Consequently, the state-of-the-art research effort is focused on minimizing its amplitude to alleviate the destructive levels of fatigue effect. In this article we consider a different perspective in looking at these problems, by proposing the conditions to achieve stable rub interference. For this, a recent mathematical tool of the authors’ group called the Cluster Treatment of Characteristic Roots (CTCR) is deployed. CTCR declares the complete stability outlook of such time-delayed systems in the space of the operational and design parameters. We show how this new capability can assist the design process of the blade-casing interface. Simulations, relevant stability observations and comparisons with a peer technique are provided for some case studies to demonstrate the capabilities of the approach.     

Influence of tool eccentricity in a well casing on theultrasonic televiewer image and its correction processing

文章研究了在套管井中仪器偏心对井壁超声电视图象的影响,提出了基于计算影响所用模型的校正方法。实验结果表明,该方法能较好地消除由于仪器偏心所引起的超声电视图象中的两条垂直黑带,明显地改善图象的质量。经对比度增强后,井壁的细节更加清楚。     

套管井中仪器偏心对井壁超声电视图象的影响及其校正

文章研究了在套管井中仪器偏心对井壁超声电视图象的影响,提出了基于计算影响所用模型的校正方向,实验结果表明,该方法能较好地消除由于仪器偏心所引起的超声电视图象中的两条垂直黑带,明显地改善图象的质量,经对比度增强后,井壁的细节更加清楚。     

多孔扩散型消声器外壳对其性能影响的研究

多孔扩散型消声器由于其体积小、消声性能高而广泛应用到排气噪声的降低上,其外壳对消声器的消声性能具有重要作用。本文对此类消声器外壳的孔型、孔径和孔距以及外壳同消声材料的配合方面进行了细致的实验研究,特别对外壳与消声材料的配合与其排放噪声以及外部流场之间的关系进行了探讨,得到了一些有用的结论,对消声器性能的提高具有一定指导意义。