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题名	偶极子源在井孔中激发的声场
作者	张秀梅
学位类别	博士
答辩日期	2008-06-04
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	偶极子 弯曲波 截止频率 黎曼叶 垂直割线
其他题名	Acoustic wave field excited by a dipole source within a fluid-filled borehole
学位专业	声学
中文摘要	偶极声波测井可以获取各种地层的横波速度，其发射和接收具有的方向性又促进了声波测井新的应用，在评价油气储层方面发挥着越来越大的作用。对偶极子源在井孔中激发的模式的传播特性及其与声场中全波和分波关系的研究，可以为改进测井仪器的设计、提高测井资料的处理及解释能力提供必要的理论指导。 本文首先对“截止频率”附近的模式波频散方程进行推导和化简，得到求解“截止频率”附近模式的解析公式。结合数值计算得到弯曲波模式无截止频率的结论。 其次，论文的理论分析表明，计算偶极声源激发的井孔声场的沿波数 的实轴积分可以转换为 黎曼面上的割线积分和极点留数的贡献，后者可用于分析模式与声场中全波和分波的关系。通过分析 黎曼面的结构，指出积分路径转换扫过的极点主要包括(-1,-1) 黎曼叶上实部满足 的极点、(0,-1) 黎曼叶上实部满足 的极点和 (0,0) 黎曼叶上实部满足 的极点。论文用数值计算分析了快慢地层井孔中这几个黎曼叶上的极点分布规律。其中 (-1,-1) 和 (0,-1) 黎曼叶上的极点为复极点，对应泄漏模式；(0,0) 黎曼叶上的极点都是实极点，对应传播模式。 在深入考察垂直割线和极点对井孔中分波和全波贡献的基础上，给出了数值表示偶极源井孔声场中分波的方法。算例结果表明纵波头波是纵波垂直割线和部分复极点的贡献，在地层的泊松比较大或者源距较小的慢地层井孔中，复极点对头波的贡献较大；横波是横波垂直割线和实极点的贡献，两者对横波的贡献与声源和井孔及地层参数有关。 论文进一步考察了泄漏模式对纵波头波的贡献随地层性质、源距及声源性质的变化，特别分析了纵波头波与地层衰减性质之间的关系，并探索了用纵波头波反演地层衰减特性的方法。这些工作为进一步应用偶极声波测井中纵波头波信息反演地层参数提供了方法和基础。 最后，论文用实验室缩尺模型井中实验和现场的数据，对模拟井孔中声场的算法进行了验证。
英文摘要	Dipole logging has made it possible to determine shear wave velocities in various formations. The excitation and reception of nonaxially symmetric wave phenomena promote many new applications of dipole logging and it plays an increasingly important role in the evaluation of oil and gas reservoirs. The study on propagation characteristics of modes excited by dipole sources within a borehole, and their contributions to the wave field, are necessary for optimizing the design of the acoustic tools, improving the data processing and interpretation techniques. Firstly, the paper studies the mode dispersion equation near the so called “cut-off frequencies”. After some derivation and simplifications, an analytical formula is obtained for solving modes near the “cut-off frequencies”. Numerical results show that there is no cut-off frequency for the flexural mode. Secondly, according to the theoretical analysis, the numerical integral path stretches along the real axis in the complex wave-number ( ) plane can be transformed into the vertical branch cut integral. The latter has the advantage of analyzing relationship among modes, individual arrivals, and the full waveforms. Based on the analysis of the structure of Riemann surface of , when the original integral path of the real axis is transformed into the vertical cut integral, the integral path sweeps over poles satisfying on Riemann sheet (-1,-1), poles satisfying on Riemann sheet (0,-1) and all poles on Riemann sheet (0,0). Then, distributions of complex poles contributing to the wave field on various Riemann sheets are investigated in detail for both fast and slow formations. The results show that poles on Riemann sheet (0,0) are real, corresponding to propagation modes, while poles on Riemann sheet(-1,-1) and (0,-1) are complex, corresponding to leaky modes. Thirdly, an approach of separating individual arrivals excited by dipole sources is presented by studying the poles and branch cuts contributions to the wave field. Numerical results show that contributions of complex poles on sheets (-1,-1) and (0,-1) together with vertical compressional branch cut integration represent the P- head wave arrival, and the complex poles contribute a lot for slow formations with large Poisson’s ratio or small offsets, while the contributions of poles on sheet (0,0) incorporated with vertical shear branch cut integration may be considered as one wave component (S- wave arrival) with an apparent wave arrival time, and the proportion of each part depends on borehole and formation parameters. For the further step, the paper examines the sensitivities of complex pole contributions to various factors of interest, including paremeters of the formations, offsets and sources, etc.. Specially, changes of head waves to attenuation of formations and inversion of head wave for attenuation are carried out, which provide method and guidance for possible applications of head waves. Finally, the experimental results from laboratory experiments and in situ XMAC datum are analyzed and compared with numerical results, which show that the experimental results conform to the theoretical predictions.
语种	中文
公开日期	2011-05-07
页码	111
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/292]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	张秀梅. 偶极子源在井孔中激发的声场[D]. 声学研究所. 中国科学院声学研究所. 2008.

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