声波测井中首波幅度衰减与速度频散研究
文献类型：学位论文
| 作者 | 周吟秋 |
| 学位类别 | 博士 |
| 答辩日期 | 2007-06-11 |
| 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 | 首波幅度 衰减 速度频散 |
| 其他题名 | Attenuation and dispersion of the first arrivals in borehole acoustic logging |
| 学位专业 | 声学 |
| 中文摘要 | 声波测井中应用最多的是记录到的纵波首波和横波首波的特性。测定首波特性对于鉴别岩性，估计地层孔隙度等都有重要的意义，认识首波特性对于利用声波测井评价天然气水合物储层及油气储层也起到重要的作用。因而，对于首波幅度衰减以及速度频散更加深入的研究也显得非常必需。 本文主要利用实轴积分和割线积分方法对裸眼井中单极子声源和偶极子声源激发的纵波首波幅度随源距的衰减规律进行分析，同时利用Prony方法对裸眼井中的纵波速度频散进行了初步研究。在对裸眼井中纵波首波幅度衰减研究的理论和经验基础之上，我们又对胶结状况不同的套管井中的首波幅度衰减进行研究。文中还模拟了超软地层的裸眼井中的声场并对各组成模式波的成分进行了分析。文中最后利用实际XMAC测井数据与理论模拟的波形对比，计算了实际首波幅度衰减规律，验证了理论数值模拟的结果。 本文通过理论分析、数值计算以及实验模拟对比研究，得到以下主要结论：裸眼井中单极子源激发的纵波首波幅度随源距z按照1/z规律衰减，偶极子源则按照1/z2规律衰减。声源在硬软地层中激发的纵波速度是存在频散的，这个频散程度很小，纵波传播速度在不同的传播特征频率附近发生很小的变化。在套管井中，当声源中心频率从低到高变化时，Ⅰ、Ⅱ界面均胶结良好的套管井中首波幅度随源距的衰减系数相差不大，但是在自由套管井中则不然。在Ⅰ、Ⅱ界面均胶结良好的套管井中，套管首波前几个不同波峰、波谷、波峰-波谷幅度的衰减系数相差不大，但是在自由套管井中则不同。当地层是超软地层时，裸眼井中声源中心频率较低时激发出一个类斯通利波模式，频率逐渐升高时会激发出另一个以略低于超软地层的纵波速度传播的模式波，当频率更高时又激发出另一个传播速度略低于井内流体纵波速度的模式波，类似于直达波。 |
| 英文摘要 | Properties of first arrivals contain the basic formation information in acoustic logging. Measuring the properties of the first arrivals plays an important role in identifying formation lithology and evaluating formation porosity and permeability. It is also helpful in oil, water, gas, and gas hydrate bearing formation evaluation. Therefore, understanding attenuation and dispersion mechanisms of the first arrivals is necessary. In this work, the attenuation of the first arrivals of compressional waves in boreholes by using a branch-cut integration (BCI) and a real axis integration (RAI) methods is studied. An elementary study on the dispersion of compressional waves in a borehole by using the Prony method is also included. With the theory and experience from the studies on the attenuation of the first arrival in open boreholes, attenuation of the first arrivals in cased-boreholes is also analyzed. In addition, acoustic wave simulations in an extremely slow formation are conducted, and several modes are seen. Finally, practical XMAC data from real well logging are used for numerical waveform comparisons, and the attenuation curves for the first arrivals from these data are plotted against the source-receiver offsets. Through theoretical, numerical, and real data studies, the following conclusions are made: In open boreholes, the first arrivals which are excited by monopole and dipole in boreholes, attenuate in the form of 1/z and 1/z2, approximately, respectively, which confirms the theoretical results. In cased boreholes, when source center frequency changes from zero, the attenuation rate of the first wave arrivals for a well-bonded casing doesn’t change much; while the attenuation rate of the first wave arrivals with a free-pipe casing changes apparently. In a well-bonded cased borehole, the attenuation rates of the amplitudes for different crests, troughs and crest-troughs don’t change greatly; while this is not true for free-pipe cased boreholes. In a very soft formation, when the source center frequency is very low, only one mode travels at a velocity close to that of the formation shear wave. When the frequency increases, another mode is excited which travels almost at the velocity of the formation compressional waves. When the frequency increases more, a large amplitude fluid wave mode is excited. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 88 |
| 源URL | [http://159.226.59.140/handle/311008/232]  |
| 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 | 周吟秋. 声波测井中首波幅度衰减与速度频散研究[D]. 声学研究所. 中国科学院声学研究所. 2007. |
入库方式： OAI收割
来源：声学研究所
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